Investigation into the accuracy and measurement methods of sequential 3D dental scan alignment

An alternative approach to code, store, and regenerate 3D data in dental medicine using open-source software: A scripting-based technique

PURPOSE

To develop a scripting-based technique for managing three-dimensional (3D) dental data and evaluate the regenerated standard tessellation language (STL) data in terms of file size, accuracy (trueness and precision), and processing time.

MATERIALS AND METHODS

Ten STL dental and maxillofacial models were obtained from various imaging technologies, including intraoral scanners, computer-aided design (CAD) software, and cone-beam computed tomography (CBCT), and saved as STL files. ChatGPT was used to generate Python scripts in Blender for mesh simplification and data compression, which were then saved as .py files. The models were regenerated from these scripts in Blender, and their accuracy was assessed using GOM Inspect software, comparing trueness and precision. Statistical analysis, including Kruskal-Wallis and Mann-Whitney tests, was conducted to evaluate differences in file sizes between the original, Python-generated, and regenerated STL files, with statistical analyses performed at a level of significance α=0.05.

RESULTS

The scripting-based technique was successfully utilized in ChatGPT to generate Python script code for accessing comprehensive data on STL models, utilizing Blender's scripting functionality. This approach enabled the generation, regeneration, and visualization of STL models, resulting in significantly smaller file sizes for both the Python script and regenerated STL files compared to the original STL files (p < 0.001). No significant differences in trueness were observed, with deviations ranging from 0.0 µm to 6.8 µm, and all regenerated STL models demonstrated perfect precision. Additionally, a proportional relationship was noted between the original STL file sizes and processing times.

CONCLUSIONS

The scripting-based approach proved to be effective in coding, storing, and regenerating STL dental data with reduced file sizes and efficient processing times without compromising the accuracy.

CLINICAL SIGNIFICANCE

Various STL dental models of patients can be coded, stored, and regenerated to be used again within efficient processing time without affecting the accuracy.

Innovative use of the snowplow technique in orthodontics: Evaluation of its effect on the accuracy and manipulation time in clear aligner attachment reproduction

OBJECTIVE

In this study, we evaluated the effectiveness of the snowplow technique, commonly used in restorative dentistry, in clear aligner therapy, focusing on manipulation time and the accuracy of attachment-shape transfer from the 3D-designed model (i.e., attachment-reproduction accuracy).

METHODS

Rectangular, ellipsoidal, and customized attachments were placed on the first premolar teeth, and different attachment-reproduction methods were evaluated. The study groups included high-viscosity (HV) and low-viscosity (LV) composites, as well as two variations of the snowplow techniques (S1 and S2). The manipulation time was recorded, and a highly detailed 3D comparison methodology (sigma, arithmetic mean, and deviation label) was used to assess attachment-reproduction accuracy.

RESULTS

Manipulation time differed significantly across all groups, with the LV group exhibiting the shortest time, followed by the S1 group (p < .001). For surface deviation, the S1 group demonstrated the lowest sigma values, particularly for rectangular attachment designs (p < .001).

CONCLUSIONS

Using the LV composite allowed the shortest application time, while the S1 technique required less manipulation time than did the HV composite. The S1 technique also achieved superior attachment accuracy, making it an effective technique for reproducing attachments with intricate surface details.

CLINICAL SIGNIFICANCE

The improved accuracy facilitated by the S1 technique may positively influence clinical outcomes by enhancing successful execution of planned tooth movements, thereby potentially improving the overall efficacy of clear aligner therapy.

Effect of Implant Scan Body type, Intraoral scanner and Scan Strategy on the accuracy and scanning time of a maxillary complete arch implant scans: an in vitro study

OBJECTIVES

This study aimed to investigate the influence of three Implant Scan Bodies (ISBs), four intraoral scanners (IOSs), and two scan strategies on the trueness of complete arch implant scans.

METHODS

A reference digital cast of an all-on-six maxillary rehabilitation was obtained using a coordinate measuring machine. Three ISBs - AQ (ISB-AQ), One-shot, Elos (ISB-PEEK) - four IOSs - Trios3POD (TRIOS), Medit i700 (MED), iTero Element 5D (iTe), Primescan (PRIME) - and two scan strategies - Zig-zag (ZZ), One-shot (OS) - were used for evaluation. For each group created by the combination of the different variables, 10 digital scans were taken by one operator (n=240) under controlled temperature and lighting conditions. The positions of the ISB connections were compared to the standard tessellation language reference file by using the nurbs-to-nurbs method. The overall 3D linear and angular deviations of the ISBs connections between reference and test scans were evaluated by computing the Euler distances (α=.05). Interimplant distance discrepancies were calculated at the ISB connection level. Scanning times were recorded.

RESULTS

Regarding linear and angular deviations, AQ had significantly higher trueness than the other ISBs (p<0.01). TRIOS showed significantly higher trueness (p<0.01). No significant differences for scan strategies were found (p>0.05). ISB-OneSh, Primescan and ZZ method resulted in significant shortest scanning times (p<<0.01).

CONCLUSIONS

ISB-AQ demonstrated higher trueness than One-Shot and PEEK. TRIOS performed better than the other IOSs. Scan strategy didn't influence the trueness. ISB-OneSh, Primescan, and ZZ strategy allowed the fastest scans.

CLINICAL SIGNIFICANCE

The choice of ISB and IOS significantly affects the accuracy of complete-arch implant scans. The scan strategy did not impact trueness but influenced the efficiency. As an in vitro study, results observed need confirmation in the clinical settings.

Wear behavior of 3D printed, minimally invasive restorations: Clinical data after 24 months in function

STATEMENT OF PROBLEM

The prevalence of pathological tooth wear and a reduced vertical dimension of occlusion has increased, but prosthetic rehabilitation concepts have been invasive, time-consuming, and expensive. How affordable, esthetic, and less invasive treatment concepts will perform remains unclear.

PURPOSE

The purpose of this proof-of-concept clinical study was to evaluate the wear behavior of 3-dimensionally (3D) printed, minimally invasive restorations fabricated from a ceramic- reinforced composite resin material after 24 months in clinical function.

MATERIAL AND METHODS

The study included 28 participants who received noninvasive 3D printed restorations made of a computer-aided design and computer aided-manufacturing (CAD-CAM) ceramic-reinforced composite resin material (n=352). Maximum occlusal height loss and mean profile loss were measured by using an intraoral scanner and a matching software program (Geomagic Control X; 3D systems) by 1 clinician. Scans were conducted at baseline and after 12 and 24 months. A descriptive statistical analysis, including mean values, medians, standard deviations (SDs) interquartile range and 95% confidence interval (95% CI) were conducted (α=.05).

RESULTS

Maximum occlusal height loss and mean profile loss were analyzed. The molar restorations showed the highest mean values of maximum occlusal height loss after 12 (0.76 mm) and 24 (1.25 mm) months. The anterior restorations showed the lowest wear rates. In general, 123 restorations (35%) had material wear >0.5 mm and were classified as fractured after 24 months of clinical application. Most of the nonfractured restorations experienced localized material wear between 0.11 mm and 0.35 mm, whereas mean profile loss values varied between 0.05 mm and 0.11 mm.

CONCLUSIONS

Three-dimensionally printed, noninvasive restorations manufactured from a ceramic-reinforced composite resin material showed considerable material wear after 2 years of clinical function, and the material appears suitable only for interim restorations.

A New Method for Volumetric Analysis of Soft-Tissue Changes Using Three-Dimensional Imaging in Patients With Periodontitis

AIMS

To quantify changes in soft-tissue volume induced by non-surgical periodontal therapy (NSPT) in patients with periodontitis and correlate them with clinical parameters and smoking. A new digital approach is investigated because standard periodontal clinical assessment methods are unable to accurately capture volumetric changes.

MATERIALS AND METHODS

Thirty-nine subjects with periodontitis aged 27-70 years (median 48; 51% females; 49% smokers) were included. All subjects underwent clinical examination and intraoral scanning at baseline and 8 weeks after NSPT. Digital models were superimposed, and changes in volume were analysed and correlated with clinical parameters.

RESULTS

NSPT reduced soft-tissue volume in both smokers and non-smokers (p < 0.001). Non-smokers had a higher median change in volume than smokers (267.4 vs. 210.5 mm3), without statistically significant differences. Periodontal clinical parameters linearly correlated with soft-tissue volume changes. In multiple linear regression, a higher initial proportion of pockets ≥ 5 mm was the only predictor of volume change when the effects of change in plaque score, smoking status, age and sex were controlled for (p = 0.015).

CONCLUSION

NSPT resulted in comparable reductions in soft-tissue volume for both smokers and non-smokers, which was confirmed by a new digital approach.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT05719519, 25.01.2023.

Evaluation of the accuracy (trueness, precision) and processing time of different 3-dimensional CAD software programs and algorithms for virtual cast alignment

OBJECTIVES

This in vitro study aimed to evaluate the impact of different alignment algorithms and CAD software programs on alignment accuracy (trueness and precision) and processing time.

METHODS

A mandibular typodont was digitized using a laboratory scanner (L2i) to obtain a reference standard tesselletion language (STLr) file. It was then scanned with an intraoral scanner (Primescan) and digitally duplicated ten times (n = 10). Each scan was aligned with the STLr using 42 combinations of 3D CAD software and alignment algorithms. The tested software programs included Blender for Dental, BlueSkyPlan, Dental CAD App (Exocad), Medit Design, NemoSmile, and Meshmixer. Alignment accuracy (trueness and precision) and processing time were recorded using Python software (v3.8). Statistical analysis was performed with a two-way ANOVA test (α = 0.01) to identify overall differences, followed by a post hoc Tukey Honestly Significant Difference test (α = 0.05) to establish rankings.

RESULTS

Significant differences in alignment accuracy were observed based on the software and algorithm used, affecting both trueness (p<.01) and precision (p<.01). Processing time also varied significantly (p<.01). Post hoc analysis identified the optimal algorithm for each software, revealing variations in trueness, precision, and processing time among the optimal versions. Medit Design achieved the best overall performance by combining high accuracy with the fastest processing time, while Meshmixer exhibited the lowest accuracy due to its lack of advanced algorithms.

CONCLUSIONS

The choice of CAD software and alignment algorithm significantly influences alignment accuracy and efficiency. Best-fit and section-based provided the best results, offering valuable insights into the optimization of digital workflows in prosthodontics.

CLINICAL SIGNIFICANCE

Alignment protocols must be tailored to the specific CAD software program used, as no universal protocol was effective across all tested software. Optimizing alignment protocols reduces errors, enhances prosthodontic outcomes, and improves the reliability and efficiency of clinical and laboratory workflows, ultimately ensuring better patient care and treatment success.

Critical methodological factors influencing the accuracy of intraoral scanners in digital dentistry research

This in vitro study aimed to identify the key methodological factors influencing the accuracy of intraoral scanners (IOS). The primary factors analyzed included the length of the scanned area, the total number of alignment points, the software used for analysis, and the operator's expertise. Three IOS systems were assessed-CEREC Primescan, Trios 3, and Omnicam-along with a laboratory desktop scanner (inEos X5). Scans were performed on a mandibular typodont, with the Root Mean Square (RMS) error used to measure the discrepancies between reference and experimental scans. The results indicated that the length of the scanned area significantly affected the RMS values, with full-arch scans producing greater errors compared to those of quadrant scans. Additionally, the total number of alignment points in the standard tessellation language files positively influenced accuracy, although improvements plateaued beyond 20 points. The choice of processing software also impacted accuracy, with Geomagic Control X yielding significantly lower RMS values than those of MeshLab and CloudCompare. Finally, user expertise played a significant role in scanning accuracy, with the experience user achieving more precise results, especially when using the Trios 3 scanner. Thus, the length of the scan, number of alignment points, software tools, and operator expertise significantly influence the accuracy of IOS, highlighting the importance of considering these methodological factors in both clinical and research settings for digital impressions.

Comparing the Capacity of Intraoral Scanner and Expert Scoring in Detecting Potential Deviations in Guided Endodontics: An In Vitro Study

INTRODUCTION

Guided endodontics recently offers a conservative solution for conducting root canal treatment in cases of obliterated canals, but guide mispositioning remains a challenge. Recently, intraoral scanners (IOS) were proposed to detect deviations, but their effectiveness compared to expert visual assessments during guide insertion is uncertain. The objective of the present study was to primarily compare the risk of deviation predicted by an IOS vs expert assessment and secondarily identify factors influencing this risk.

METHODS

Using a design of experiments approach, 16 endodontic guides were 3D-printed to assess the influence of guide thickness, internal offset, number of supporting teeth, and presence of windows. Guide positioning was evaluated digitally with the Trios 4 IOS to calculate angular deviation and visually by 10 experts using a Likert scale. The overall agreement between the value of angular deviation (less than or greater than 2°) and the expert score (positive or negative) was calculated.

RESULTS

The mean angular deviation was 4.32° (SD = 2.40°) and the mean expert score was -0.29 (SD = 1.39). Angular deviation was most influenced by greater guide thickness (41.4%) and internal offset (27.0%), which both increased it. The most influential factor for expert scores was internal offset (90.5%), which decreased ratings. Agreement between IOS and expert scores averaged 60.6% (SD = 39.1%), with the highest agreement for guides with a high internal offset.

CONCLUSIONS

Experts effectively detected positioning errors with high internal offset but struggled with other factors where IOS was more accurate. IOS shows promising potential for improving guide fitting in clinical practice.

Trueness and precision of complete denture digital impression compared to conventional impression: an in vitro study

Background

This study aimed to compare the precision and trueness of digital impressions of the edentulous arch made with different scanners to conventional physical impressions.

Methods

A total of 40 impressions of a completely edentulous maxillary arch model (n = 10) were made using different digital impressions with an extraoral scanner, E3 3Shape desktop scanner, as the reference scan, intraoral scanner (TRIOS IOS, and Medit IOS) and Vinyl Polysiloxane impressions (VPS) impression using a Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) custom tray. The VPS impression was scanned with the desktop scanner to produce standard tessellation language (STL) files for comparison with the digital impressions made by the Desktop and intraoral scanners. The STL files were super-imposed to a desktop scan and to each other with the same group using Geomagic Control X Software to assess the trueness and precision, respectively. A t-test was conducted for statistical analysis with a significance level of 0.05.

Results

The overall trueness, Medit had the highest deviation compared to the VPS and TRIOS groups with a P value of 0.0013 and <0.0001, respectively. In terms of overall precision, TRIOS had a lower deviation than the VPS group, with a P value of 0.0002. The TRIOS and Medit groups had statistically comparable results. The desktop scanner showed the highest precision in digitizing completely edentulous cases, followed by the TRIOS scanner. The Medit scanner's trueness had the highest deviation compared to the VPS and TRIOS groups.

Implant scanning workflows: Accuracy of registration methods for integrating intraoral scans containing soft tissue and tooth position information

STATEMENT OF PROBLEM

An implant scanning workflow involves recording different intraoral scans containing all the information needed to fabricate an implant-supported prosthesis. The accuracy of these implant scanning workflow registration methods remains unknown.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of different implant scanning workflows for registering the soft tissue and tooth position information scans recorded by using 5 intraoral scanners (IOSs).

MATERIAL AND METHODS

A maxillary edentulous stone cast with 6 implant abutment analogs (MultiUnit Abutment Replica) and 2 screw-retained implant-supported interim restorations (from the right first molar to the left canine and from the left first premolar to the left first molar) were obtained. Three markers were attached on the palatal surface of the cast on the anterior palatine raphe and right and left first molar positions, and 4 markers were attached on the palatal surface of the right and left second premolar and right and left lateral incisor of the interim prostheses. Afterwards, 5 composite resin (CR) reference landmarks were created on the palatal surface of the cast on the anterior palatine raphe, right and left first premolar, and right and left first molar. Additionally, a screw was placed in the posterior palatine raphe, simulating a temporary anchorage device (TAD). The interim prostheses were positioned in the implant analogs of the cast and digitized by using a laboratory scanner (T710). Five groups were created depending on the IOS: TRIOS 5, i700, Elite, iTero, and Primescan groups. A tooth position, soft tissue information, and soft tissue with existing teeth scans were obtained by using each IOS. Six subgroups were created depending on the reference landmarks used to register the scans: 3 or 5 CR landmarks (3CR or 5RC subgroup, respectively), existing teeth (teeth subgroup), existing teeth combined with 2 CR landmarks (teeth+2CR subgroup), TAD (TAD subgroup), TAD combined with 1 CR landmark (TAD+1CR subgroup). Twelve linear measurements were performed on the control scans and on each specimen among the 7 markers. Trueness was analyzed by using 2-way ANOVA and the pairwise comparison Tukey tests (α=.05). Precision was evaluated by using the Levene and pairwise comparisons tests (α=.05).

RESULTS

Trueness discrepancies were found among the groups (P<.001) and subgroups (P<.001), with a significant group*subgroup interaction (P=.004). The Tukey test showed that the Primescan and iTero systems obtained worse trueness than the other groups. Also, the TAD and Teeth subgroups obtained worse trueness than the other subgroups tested. All the groups and subgroups were significantly different from each other (P<.05).

CONCLUSIONS

The IOS and reference landmarks tested impacted the trueness and precision of the registration of soft tissue and tooth position information scans.

Implant Scanning Workflows for Fabricating Implant-Supported Prostheses Recorded by Using Intraoral Scanners With or Without Photogrammetry Technologies

OBJECTIVES

To classify complete-arch implant scanning workflows for registering implant position, tooth position, soft tissue information, and maxillomandibular relationship recorded by using intraoral scanners (IOSs) with or without photogrammetry (PG) technologies.

OVERVIEW

Implant scanning workflow has been defined as the procedures required to acquire the digital information needed to design an implant-supported prosthesis, including implant and tooth position, soft tissue information, and maxillomandibular relationship scans. As a part of the implant scanning workflow, different implant scanning techniques have been described for recording the 3-dimensional position of the implants being scanned by using IOSs. Alternatively, PG systems can also be used to record implant positions. However, dental literature lacks a classification of implant scanning workflows.

CONCLUSIONS

There are six main implant scanning workflows based on the reference landmarks used: worflows guided by existing teeth, fiducial markers, fixation references, implant scan bodies, auxiliary devices, and interim restorations.

CLINICAL SIGNIFICANCE

Understanding different implant scanning workflows allows dental professionals to efficiently capture all the digital data information needed to design and fabricate implant-supported prostheses by using an intraoral scanner with or without a photogrammetry system.

Use of polyvinyl siloxane impressions to monitor sub-5-μm erosive tooth wear on unpolished enamel

STATEMENT OF PROBLEM

Whether polyvinyl siloxane impressions are capable of reproducing 5-μm changes on natural freeform enamel and potentially enabling clinical measurements of early surface changes consistent with wear of teeth or materials is unclear.

PURPOSE

The purpose of this in vitro study was to investigate and compare polyvinyl siloxane replicas with direct measurements of sub-5-μm lesions on unpolished human enamel lesions by using profilometry, superimposition, and a surface subtraction software program.

MATERIAL AND METHODS

Twenty ethically approved unpolished human enamel specimens were randomized to a previously reported cyclic erosion (n=10) and erosion and abrasion (n=10) model to create discrete sub-5-μm lesions on the surface. Low viscosity polyvinyl siloxane impressions were made of each specimen before and after each cycle and scanned by using noncontacting laser profilometry and viewed with a digital microscopy and compared with direct scanning of the enamel surface. The digital maps were then interrogated with surface- registration and subtraction workflows to extrapolate enamel loss from the unpolished surfaces by using step-height and digital surface microscopy to measure roughness.

RESULTS

Direct measurement revealed chemical loss of enamel at 3.4 ±0.43 μm, and the polyvinyl siloxane replicas were 3.20 ±0.42 μm, respectively. For chemical and mechanical loss direct measurement was 6.12 ±1.05 μm and 5.79 ±1.06 μm for the polyvinyl siloxane replica (P=.211). The overall accuracy between direct and polyvinyl siloxane replica measurements was 0.13 +0.57 and -0.31 μm for erosion and 0.12 +0.99 and -0.75 μm for erosion and abrasion. Surface roughness and visualization with digital microscopy provided confirmatory data.

CONCLUSIONS

Polyvinyl siloxane replica impressions from unpolished human enamel were accurate and precise at the sub-5-μm level.

In vivo prospective randomised study of the wear of dental restorations using an intraoral scanner and its correlation with visual assessment

OBJECTIVES

To evaluate the efficacy of the True Definition® intraoral scanner in quantifying the wear of glass ionomer restorative materials (KetacTM Universal and KetacTM Molar) over 1 year. We also studied the correlation between visual and digital assessments of restoration wear.

METHODS

This was a clinical follow-up study of a post-marketed material with a prospective, controlled, randomised, split-mouth, and blinded assessment design. Intraoral optical impression and visual assessment were carried out over three appointments over 12 months, starting with 36 patients.

RESULTS

According to the visual indices, all restorations in this study were clinically healthy. However, in the digital measurement of wear, 94.74% and 94.44% of the restorations during the T0-T6 and T6-T12 observation periods, respectively, showed deterioration greater than 41 microns. Moreover, in the analysis of agreement between measurement techniques, no agreement was obtained in the two analysed time periods: T0-T6 yielded a kappa (k) value of 0.000, and T6-T12 yielded k=0.0030. Discordant results were obtained in the correlation analysis. In T0-T6, the results were not considered statistically significant (p=0.838); however, the results obtained during T6-T12 showed a correlation (p-value <0.001).

CONCLUSIONS

The wear of dental materials as observed by the human eye did not agree with that observed by intraoral scanning. The scanner effectively measures wear, detecting details that are beyond the capability of the human eye and conventional photographs. The surface deterioration of the restorations at both observation times can be considered non-physiological, potentially leading to premature occlusal alterations and accelerated physiological ageing.

CLINICAL RELEVANCE

Early diagnosis is crucial for avoiding alterations in the function of the stomatognathic system due to the wear of dental restorations. Additionally, since most of the tools applied are qualitative in nature, such as visual inspection, it is essential to find a standardised and precise tool that offers diagnosis, monitoring, and records of the evolution of tooth wear. This study has been registered at https://www.

CLINICALTRIALS

gov, under the identifier NCT06275581.

Spatial Abilities and Endodontic Access Cavity Preparation: Implications for Dental Education

INTRODUCTION

Access cavity preparation is a crucial step in root canal treatment but is one of the most complex procedures in the curriculum to learn, with students often reporting spatial orientation difficulties during drilling. The present study aimed to evaluate the influence of spatial abilities on the preparation of endodontic access cavities among third-year dental students.

MATERIALS AND METHODS

Students from Lyon dental faculty participated voluntarily. The mental rotation test (MRT) evaluated spatial ability. Students prepared access cavities on 3D-printed mandibular molars, subsequently scanned and assessed against eight evaluation points, including morphology, canal access, floor preservation and convergence angle. Principal component analysis (PCA) assessed dataset variations.

RESULTS

A total of 43 volunteers participated. PCA revealed two principal components accounting for 80.8% of variations: the first PC primarily consisted of MRT score (64.3%) and morphology (14.1%); the second comprised operative time (46.1%) and morphology (18.0%). There were significant differences in morphology based on MRT scores, but no correlation was found between other parameters.

DISCUSSION

Lower MRT scores were associated with larger cavity preparations, raising questions about potential curriculum adaptations to enhance spatial reasoning. The operative time was not correlated with higher MRT scores but did contribute to variations in cavity morphology.

CONCLUSION

Spatial abilities have a substantial impact on the quality of endodontic access cavity preparations; further studies should evaluate if the incorporation of 3D atlas exercises could be beneficial.

Feasibility, trueness and precision of intraoral scanners in digitizing maxillectomy defects with exposed zygomatic implants in situ: An in vitro 3D comparative study

OBJECTIVES

To in-vitro evaluate the feasibility and accuracy (trueness and precision) of various intraoral scanners (IOS) to digitize maxillectomy defect models with exposed zygomatic implants in situ.

MATERIAL AND METHODS

Six partially edentulous and edentulous maxillectomy defect models with 2 zygomatic implants each were obtained. References scans were obatined by using a laboratory scanner (inEos X5; Dentsply Sirona). Three IOS, Trios 3, Trios 4 (3Shape A/S), and Primescan (Dentsply Sirona) were used first to digitize the entire model including implants and then to only scan the exposed part of zygomatic implants. The feasibility was assessed by evaluating the intraoral scanner's ability to accurately capture the maxillectomy defects and zygomatic implants, compared to a reference standard. Trueness and precision were evaluated using software's global best-fit alignment (GOM Inspect, GOM GmbH). Multifactorial analysis of variance (ANOVA) was used to compare the mean 3D deviation according to different scanners, groups, and model types. The significance level used in the analyses was 5 % (α=0.05).

RESULTS

All scanners showed adequate feasibility to scan the entire maxillectomy defects and exposed implants regardless of the structural complexity. The results of trueness showed that Primescan has the smallest 3D deviations (0.0252 mm) followed by Trios 4 (0,0275 mm), and then Trios 3 (0.0318 mm) (p < 0.001). The results of precision showed that Primescan had the smallest 3D deviations (0.0026 mm) followed by Trios 3 (0,0080 mm), and then Trios 4 (0,0097 mm) (p < 0.001).

CONCLUSION

Intraoral scanners differ in feasibility, trueness and accuracy of all scans, with Primescan providing the best combination of feasibility, trueness and accuracy, followed by Trios 4 and Trios 3.

CLINICAL SIGNIFICANCE

Scanning maxillectomy defects with various exposed zygomatic implants can be feasible and accurate using intraoral scanners (Trios 3, Trios 4, and Primescan). The use of intraoral scanners for implant-prosthetic rehabilitation of maxillectomy defect can be a feasible alternative that can improve and simplify the workflow.

Colorimetric analysis of intraoral scans: A novel approach for detecting gingival inflammation

BACKGROUND

Gingivitis, a widely prevalent oral health condition, affects up to 80% of the population. Traditional assessment methods for gingivitis rely heavily on subjective clinical evaluation. This study seeks to explore the efficacy of interpreting the color metrics from intraoral scans to objectively differentiate between healthy and inflamed gingiva.

METHODS

This study used the percentage of bleeding on probing (BOP%) as the clinical reference standard. Intraoral scans, obtained before and after gingivitis treatment using a scanner, were analyzed through a custom MATLAB script to quantify HSV (hue, saturation, value) and CIELAB (Commission Internationale de l'Eclairage L*a*b*) color coordinates. The region of interest was a 2-mm-wide gingival strip along the buccal margin of the maxillary anterior teeth. Linear regression analysis was performed to evaluate the relationship between photometric outcomes and continuous, dichotomous, and categorical BOP data. Diagnostic accuracy was assessed using the area under the receiver operating characteristic (ROC) curve (AUC), as well as sensitivity and specificity measures.

RESULTS

The analysis included clinical and digital color data from 110 scans, adhering to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. The multilevel linear regression analysis underscored a significant correlation between the BOP% and digital color metrics, specifically the CIELAB a* (red-green chroma), CIELAB b* (yellow-blue chroma), and color saturation, with AUC performances of 70%, 79.5%, and 80.8%, respectively.

CONCLUSION

Digital color analysis of intraoral scans has demonstrated a range of performance from acceptable to excellent in distinguishing sites with BOP. This innovative approach presents a promising tool for dentists and researchers in the accurate diagnosis, screening, and management of gingivitis.

PLAIN LANGUAGE SUMMARY

Our study focuses on finding a better way to detect gingivitis, a common gum disease affecting many people. Traditional methods rely on the dentist's visual inspection, which can be subjective. We explored the use of color measurements from digital intraoral scans to objectively identify healthy versus inflamed gums. We analyzed 110 scans from 55 participants, examining the color differences in the gums before and after treatment. By measuring specific color values, we achieved up to 80.8% accuracy in distinguishing between healthy and inflamed gums. This method could offer a more reliable tool for dentists and researchers to diagnose and manage gingivitis, leading to better oral health outcomes.

Precision in dentistry: how PLA 3D printing settings influence model accuracy

PURPOSE

Advancements in computer-aided design and manufacturing (CAD/CAM), such as intraoral scanners, digital treatment planning, and 3D printers, offer digital alternatives to conventional orthodontics. For transforming digital data into a traditional model, precise 3D printing technologies are necessary. With numerous settings available on each 3D printer, selecting the most precise one is challenging. Therefore, the impact of layer height, printing temperature, print speed, and infill density on the accuracy of dental models was analyzed in this study.

METHODS

A 3D file of a right upper central incisor was designed and printed 275 times in total with different settings for temperature, layer height, print speed, and infill density by using polylactic acid (PLA) filament on an industrial 3D printer. After scanning the models, root mean square error was calculated for analysis of precision. For each group, R2 value was calculated and linear regression as well as an ANOVA was performed for the factors influencing accuracy.

RESULTS

Printing temperature as well as layer height had statistically significant impacts on printing 3D tooth models (p < 0.05). R2 values of 0.43 for printing temperature as well as of 0.11 for layer height were detected. The infill density as well as the print speed had no statistically significant impacts on accuracy (p > 0.05).

CONCLUSION

This study confirms that choosing the correct printing temperature and layer height for printing dental models with PLA is important for obtaining good accuracy, whereas print speed and infill density have less of an impact.

Influence of short-span scans on trueness in the digital transfer of the maxillomandibular relationship

OBJECTIVES

This study aimed to assess the influence of the location and distribution of short-span scans, serving as intermediate registration data, on the trueness of digitally transferring the maxillomandibular relationship in full-mouth rehabilitation.

METHODS

Maxillary and mandibular complete-arch preparation casts mounted on an articulator were scanned, with and without interim restorations, using an intraoral scanner. Four types of short-span scans-right anterior, left anterior, right posterior, and left posterior-were captured from maxillary and mandibular casts. Each scan comprised two prepared teeth and two crowned teeth arranged alternately. These short-span scans served as intermediate data and were cross-registered with complete-arch interim restorations and preparation casts to transfer the maxillomandibular relationship. Based on the number (1 or 2), location (anterior or posterior), and distribution (unilateral or bilateral) of short-span scans, they were categorized into six groups. Trueness was assessed by evaluating the mandibular 3-dimensional (3D), spatial distance, angle, and linear distance deviations between the test and reference scans.

RESULTS

Significant differences in the trueness of digital cross-mounting were observed among the six groups (P < .05). The group registering the bilateral posterior areas exhibited the smallest 3D, spatial distance, angle, and linear distance deviations, whereas the group registering one anterior area showed the largest deviations.

CONCLUSION

The number, location, and distribution of the registered short-span scans significantly affected the trueness of transferring the maxillomandibular relationship. A posterior short-span scan had higher trueness than an anterior scan. The symmetrical distribution of the two registered larger short-span scans over the cross-arch enhanced the registration trueness.

CLINICAL SIGNIFICANCE

Digital cross-mounting in full-mouth rehabilitation using short-span scans enhances transfer accuracy, improves patient comfort, and increases chairside efficiency.

"Evaluation of Silver Diamine Fluoride Modified Atraumatic Restorative Treatment (SMART) on hypomineralized first permanent molar"- a randomized controlled clinical study

BACKGROUND

Restoring first permanent molars affected with molar incisor hypomineralization (MIH) is challenging. Focusing on improving the quality of life for children affected by MIH, at least until the complete eruption of first permanent molars to receive full coverage, to decrease the hypersensitivity and to be able to perform proper oral hygiene measures, the purpose of this study was to compare silver modified atraumatic restorative technique (SMART) versus the conventional restoration and fluoride varnish application on moderate to severe hypomineralized molars. The comparison considered the restoration survival, hypersensitivity, and digital surface area changes after one year follow up.

METHODS

Twenty-eight children were selected (20 girls and 8 boys) with at least 2 MIH molars with the same defect severity. The study comprised 2 groups; MOD group (moderate hypomineralized molar severity) and SEV group (Severe hypomineralized molar severity) (n = 28 tooth). Each group was further subdivided into 2 subgroups according to the technique of restoration: SMART subgroup and CONV subgroup (high viscosity glass ionomer restoration and fluoride varnish application) (each = 14 tooth). Evaluation was done in terms of the restoration survival (6 months and 12 months), hypersensitivity at 1 weak, 6 months and 12 months and occlusal surface area changes at 12 months). Professional Fluoride varnish application and home prophylaxis using MI paste were the protocol for each child patient.

RESULTS

There was no significant difference between the 4 subgroups, regarding tooth restoration integrity at 6-months vs. 12-months. However, a statistically significant difference in tooth restoration integrity between the 4 subgroups at 12-months (P = .049). Also, the hypersensitivity score, there was a statistically significant difference between the 4-time intervals (P < .001) and a statistically significant difference in surface area changes between the 4 subgroups.

CONCLUSIONS

Selective removal of carious tissue and SMART restoration, combined with dental home and professional preventive measures every 3 months maintained the integrity of restorations in severely and moderately affected permanent molars up to 1 year.

TRIAL REGISTRATION

The study protocol was retrospectively registered on Clinical Trials (NCT05931822-05/ 07/2023).

Factors affecting accuracy in the additive manufacturing of interim dental prostheses: A systematic review

STATEMENT OF PROBLEM

A systematic review of the effect of different factors on the accuracy of additively manufactured (AM) interim dental prostheses is lacking.

PURPOSE

The purpose of this systematic review was to identify potential factors that may affect the accuracy of AM interim dental prostheses.

MATERIAL AND METHODS

The review adhered to the guidelines outlined in the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. The protocol was registered in the international prospective database of systematic reviews (PROSPERO) (CRD42024521564). The risk of bias in the included studies was assessed by using the Joanna Briggs Institute (JBI) checklist. Two reviewers performed an electronic search on the Web of Science, Scopus, PubMed, and Embase databases for articles published up to the end of 2023.

RESULTS

The electronic search resulted in 406 studies. After removing duplicates, 205 studies remained. Thirty-one studies (30 in vitro and 1 in vivo) were included and categorized into 6 types: AM material (type and composition), prosthetic factor (tooth type, restoration size, finish line, abutment taper), AM system (technique and printer), AM parameters (layer thickness, printing orientation), postprocessing (rinsing, postpolymerization), and aging.

CONCLUSIONS

The accuracy of AM interim dental prostheses is affected by factors that include the AM material, prosthetic factors, the AM system, the AM parameters, postprocessing, and aging.

Impact of the superimposition methods on accuracy analyses in complete-arch digital implant investigation

OBJECTIVES

To measure the impact of the superimposition methods on accuracy analyses in digital implant research using an ISO-recommended 3-dimensional (3D) metrology-grade inspection software.

MATERIALS AND METHODS

A six-implant edentulous maxillary model was scanned using a desktop scanner (7Series; DentalWings; Montreal, Canada) and an intraoral scanner (TRIOS 4; 3Shape; Copenhagen, Denmark) to generate a reference and an experimental mesh, respectively. Thirty experimental standard tesselletion language (STL) files were superimposed onto the reference model's STL using the core features of six superimposition methods, creating the following groups: initial automated pre-alignment (GI), landmark-based alignment (G1), partial area-based alignment (G2), entire area-based alignment (G3), and double alignment combining landmark-based alignment with entire model area-based alignment (G4 ) or the scan bodies' surface (G5). The groups underwent various alignment variations, resulting in sixteen subgroups (n = 30). The alignment accuracy between experimental and reference meshes was quantified by using the root mean square (RMS) error as trueness and its fluctuation as precision. The Kruskal-Wallis test with a subsequent adjusted post-hoc Dunn's pairwise comparison test was used to analyze the data (α = 0.05). The reliability of the measurements was assessed using the intraclass correlation coefficient (ICC).

RESULTS

A total of 480 superimpositions were performed. No significant differences were found in trueness and precision among the groups (p > 0.05), except for partial area-based alignment (p < 0.001). Subgroup analysis showed significant differences for partial area-based alignment considering only one scan body (p < 0.001). Initial automated alignment was as accurate as landmark-based, partial, or entire area-based alignments (p > 0.05). Double alignments did not improve alignment accuracy (p > 0.05). The entire area-based alignment of the scan bodies' surface had the least effect on accuracy analyses.

CONCLUSIONS

Digital oral implant investigation remains unaffected by the superimposition method when ISO-recommended 3D metrology-grade inspection software is used. At least two scan bodies are needed when considering partial area-based alignments.

CLINICAL SIGNIFICANCE

The superimposition method choice within the tested ISO-recommended 3D inspection software did not impact accuracy analyses in digital implant investigation.

Assessing tooth wear progression in non-human primates: a longitudinal study using intraoral scanning technology

Intraoral scanners are widely used in a clinical setting for orthodontic treatments and tooth restorations, and are also useful for assessing dental wear and pathology progression. In this study, we assess the utility of using an intraoral scanner and associated software for quantifying dental tissue loss in non-human primates. An upper and lower second molar for 31 captive hamadryas baboons (Papio hamadryas) were assessed for dental tissue loss progression, giving a total sample of 62 teeth. The animals are part of the Southwest National Primate Research Center and were all fed the same monkey-chow diet over their lifetimes. Two molds of each dentition were taken at either two- or three-year intervals, and the associated casts scanned using an intraoral scanner (Medit i700). Tissue loss was calculated in WearCompare by superimposition of the two scans followed by subtraction analysis. Four individuals had dental caries, and were assessed separately. The results demonstrate the reliability of these techniques in capturing tissue loss data, evidenced by the alignment consistency between scans, lack of erroneous tissue gain between scans, and uniformity of tissue loss patterns among individuals (e.g., functional cusps showing the highest degree of wear). The average loss per mm2 per year for all samples combined was 0.05 mm3 (0.04 mm3 for females and 0.08 mm3 for males). There was no significant difference in wear progression between upper and lower molars. Substantial variation in the amount of tissue loss among individuals was found, despite their uniform diet. These findings foster multiple avenues for future research, including the exploration of wear progression across dental crowns and arcades, correlation between different types of tissue loss (e.g., attrition, erosion, fractures, caries), interplay between tissue loss and microwear/topographic analysis, and the genetic underpinnings of tissue loss variation.

Cervical wear pathobiology by robot-simulated 3-year toothbrushing - New methodological approach

OBJECTIVES

An ex-vivo study was aimed at (i) programming clinically validated robot three-year random toothbrushing, (ii) evaluating cervical macro- and microwear patterns on all tooth groups of different functional age, (iii) documenting and codificating wear related morphological features at the cemento-enamel junction in young teeth and on roots in older teeth.

DESIGN

Following ethical approval random toothbrushing (44 strokes per tooth horizontally, rotating, vertically; 2x/d) with manual toothbrushes and low-abrasive dentifrice was performed in an artificial oral cavity with brushing-force 3.5 N on 14 extracted human teeth. Morphological features were examined by SEM at baseline and after simulated 3 years using the replication technique. 3D-SEM analyses were carried out with a four-quadrant back scattered electron detector. Wilcoxon-Mann-Whitney-test was used for statistical analyses.

RESULTS

3-year random toothbrushing with horizontal, rotating and vertical brushing movements revealed morphological features classified as four enamel patterns, one dentin pattern and three cervical patterns. Negative impacts were enamel, cementum and dentin loss. Positive impact on oral health was removing dental calculus and straightening cervical traumatic and iatrogenic damages. The volume loss varied from x̅=34.25nl to x̅=87.75nl. Wear extended apically from 100 to 1500 micrometres.

CONCLUSION

Robot simulated toothbrushing in an artificial oral cavity, with subsequent SEM and 3D-SEM assessment, elucidated both negative and oral health-contributing micromorphology patterns of cervical wear after simulated 3-year random toothbrushing. Cervical macro- and microwear of cementum revealed, for the first time, what we describe as overhanging enamel peninsulas and enamel islands on roots in young teeth, but no enamel islands on roots from older teeth after root cementum loss. In contrast, many older teeth exhibited enamel peninsulas.

Intraoral scanners as tracking devices: A dental protocol for assessing volumetric changes between intraoral scans

Intraoral scanners (IOSs) are digital data acquisition technologies that ease the recording of virtual diagnostic casts. Some IOSs have a specific software tool to assess volumetric changes between 2 scans acquired on the patient at different times. The scans are superimposed and volumetric differences between both meshes are reported. However, these software tools may be limited to scans captured only by the IOS of the same manufacturer. The present manuscript describes a protocol for comparing volumetric changes between 2 scans recorded using any IOS. Additionally, 1 of the scans is divided into 3 sections to minimize the alignment distortion and maximize the evaluation of the volumetric changes.

Comparison of wear and fracture resistance of additively and subtractively manufactured screw-retained, implant-supported crowns

STATEMENT OF PROBLEM

Additively manufactured resins indicated for fixed definitive prostheses have been recently marketed. However, knowledge on their wear and fracture resistance when fabricated as screw-retained, implant-supported crowns and subjected to artificial aging is limited.

PURPOSE

The purpose of this in vitro study was to evaluate the volume loss, maximum wear depth, and fracture resistance of screw-retained implant-supported crowns after thermomechanical aging when fabricated using additively and subtractively manufactured materials.

MATERIAL AND METHODS

Two additively manufactured composite resins (Crowntec [CT] and VarseoSmile Crown Plus [VS]) and 2 subtractively manufactured materials (1 reinforced composite resin, Brilliant Crios [BC] and 1 polymer-infiltrated ceramic network, Vita Enamic [EN]) were used to fabricate standardized screw-retained, implant-supported crowns. After fabrication, the crowns were cemented on titanium base abutments and then tightened to implants embedded in acrylic resin. A laser scanner with a triangular displacement sensor (LAS-20) was used to digitize the pre-aging state of the crowns. Then, all crowns were subjected to thermomechanical aging (1.2 million cycles under 50 N) and rescanned. A metrology-grade analysis software program (Geomagic Control X 2020.1) was used to superimpose post-aging scans over pre-aging scans to calculate the volume loss (mm3) and maximum wear depth (mm). Finally, all crowns were subjected to a fracture resistance test. Fracture resistance and volume loss were evaluated by using 1-way analysis of variance and Tukey Honestly significant difference (HSD) tests, whereas the Kruskal-Wallis and Dunn tests were used to analyze maximum wear depth. Chi-squared tests were used to evaluate the Weibull modulus and characteristic strength data (α=.05).

RESULTS

Material type affected the tested parameters (P<.001). CT and VS had higher volume loss and maximum wear depth than BC and EN (P<.001). EN had the highest fracture resistance among tested materials (P<.001), whereas BC had higher fracture resistance than CT (P=.011). The differences among tested materials were not significant when the Weibull modulus was considered (P=.199); however, VE had the highest characteristic strength (P<.001).

CONCLUSIONS

Additively manufactured screw-retained, implant-supported crowns had higher volume loss and maximum wear depth. All materials had fracture resistance values higher than the previously reported masticatory forces of the premolar region; however, the higher characteristic strength of the subtractively manufactured polymer-infiltrated ceramic network may indicate its resistance to mechanical complications.

Impact of the superimposition reference area on intraoral scanning accuracy in a partially dentate maxilla

STATEMENT OF PROBLEM

The alignment of 3-dimensional (3D) files involves selecting a reference area before performing a local best fit alignment during the digital scan superimposition and is essential for comparing digital scans. Scan alignment relies on both reference area location and the alignment algorithm. However, a consensus on the impact of different reference areas on intraoral scanning accuracy is lacking.

PURPOSE

The purpose of this in vitro study was to assess the impact of 3 superimposition reference areas on the accuracy of 3 intraoral scanners for a partially dentate maxilla.

MATERIAL AND METHODS

A Kennedy class II resin cast was scanned using 3 intraoral scanners (Primescan, TRIOS 3, and Emerald) outputting 30 digital scans (10 per scanner). Test scans from intraoral scanners were subsequently compared with a reference digital standard tessellation language file generated by a laboratory scanner with validated accuracy. The files were superimposed using best fit alignment for each intraoral scanner using 3 different superimposition reference areas (whole region of interest, palate, and all teeth). Accuracy was assessed by using a 3D analysis program (Geomagic Control X; 3D systems) for each scanner at 4 preselected areas. Test and reference scan differences were depicted on color maps and quantified via root mean square deviations. Differences were analyzed using regression analysis with the post hoc student t test and Bonferroni correction (α=.05).

RESULTS

The TRIOS 3 and Emerald produced positive deviations in the palatal color maps, whereas Primescan produced more uniform color maps, regardless of the superimposition strategy used. Primescan exhibited the best accuracy (trueness and precision) in both palatal and bounded edentulous areas, regardless of the superimposition reference area. The TRIOS 3 recorded the highest distal extension trueness (ranging from 42.9±7.7 µm to 65 ±19.5 µm), and Primescan achieved the highest precision (ranging from 28.5 ±9.8 µm to 48.9 ±16.9 µm), regardless of the superimposition area. Emerald demonstrated the highest teeth trueness (ranging from 31.6 ±6.8 µm to 69.6 ±11.5 µm), while Primescan produced the highest precision (ranging from 17.9 ±6.1 µm to 30.7 ±9.2 µm), regardless of the reference area used.

CONCLUSIONS

The chosen reference area for best fit alignment significantly influenced digital scan accuracy (P<.001). Primescan displayed the highest palatal and bounded edentulous area accuracy, with TRIOS 3 recording the highest distal extension trueness. Emerald recorded the highest teeth trueness and Primescan recorded the highest distal extension and tooth precision. All conclusions were independent of the superimposition strategy used.

Investigation of the precision of a novel jaw tracking system in recording mandibular movements: A preliminary clinical study

OBJECTIVES

This preliminary study aimed to clinically assess the precision of a novel optical jaw tracking system (JTS) in registering mandibular movements (MMs) of protrusion and mediotrusion.

METHODS

Twenty healthy participants underwent recordings using Cyclops JTS (Itaka Way Med) for functional MMs of protrusion and laterotrusion by two trained clinicians. Each subject performed five registrations at different times according to a standardized pattern within one-month period. The angulations of protrusive and mediotrusive functional paths within the first 2 mm from the maximal intercuspal position (MIP) were calculated for each trace, using a data software for angle measurements. Descriptive statistics were used to assess the repeatability of the recordings for each participant and MM. Additionally, inferential statistics were carried out on standard deviation values obtained (α=0.05).

RESULTS

The overall precision for all the patients was 7.07±3.37° for the protrusion angle, 5.24±2.24° for right laterotrusion and 5.14±3.06° for left laterotrusion angles. The protrusion angle ranged from 3.08° to 13.57°, while the right and left laterotrusion ranged from 1.82° to 9.42° and from 1.58° to 10.59°, respectively. No statistically significant differences were observed between different functional MM types and gender (p > 0.05).

CONCLUSIONS

Recordings functional MMs of mediotrusion and protrusion using Cyclops JTS showed consistent repeatability, regardless of gender and functional MM type. The results revealed non-negligible variations that may be due to the patients' abilities to precisely reproduce jaw movements or to the operator's ability to consistently connect the kinesiograph.

CLINICAL SIGNIFICANCE

Capturing functional MMs digitally and importing the data into dental CAD software is essential for virtual waxing in prosthetic rehabilitations to design a functionalized adapted occlusion. Establishing the repeatability of MM recordings by a JTS is a crucial step in better understanding this novel JTS in the market. This process could facilitate the interpretation of cusp angles, aid in CAD dynamic technical modeling, and enhance clinical data communication between clinicians and technicians in a modern workflow.

Accuracy of Complete-Arch Scans Obtained by Intraoral Scanner and Smartphone Three-Dimensional Scanning Applications With Different Smartphone Position Setups: An In Vitro Study

INTRODUCTION

The high cost of intraoral scanners (IOS) for complete-arch scans makes them less accessible for many dental practitioners. As a viable alternative, smartphone scanner applications (SMP) provide comparable scanning capabilities at a significantly low cost. However, there is limited data on the accuracy of SMP, especially when used in various smartphone positions. This study aimed to compare the three-dimensional (3D) and linear accuracy of complete-arch scans acquired by an IOS and SMP (KIRI Engine, KIRI Innovations, Guangdong, China) at three shooting angles (0°, 45°, and 90° for SMP_3A) and two shooting angles (30° and 60° for SMP_2A).

METHODS

A stone dental cast was scanned with a laboratory scanner as a reference, with 11 scans performed by an IOS, SMP_2A, and SMP_3A. In 3D analysis, trueness and precision were evaluated through superimposition with the reference scan and within each group, respectively, using the best-fit algorithm of Geomagic Wrap software (3D Systems, Inc., Rock Hill, SC). Trueness in linear discrepancy was assessed by comparing the occlusal-cervical and mesiodistal dimensions of reference teeth (canine, premolar, and molar), intercanine width, and intermolar width on the digital casts to measurements of the stone cast, while precision was measured using the coefficient of variance. Differences between groups were analyzed using the Friedman test, followed by the Dunn-Bonferroni post hoc test with a significance level set at 0.05.

RESULTS

IOS exhibited significantly lower trueness than SMP_2A (p = 0.003) with significantly greater width discrepancies on canines (p = 0.001) and molars (p < 0.001). Discrepancy patterns differed among the three scanning methods. The IOS showed greater discrepancies on the occlusal surfaces of posterior teeth. While SMP_3A demonstrated higher variation on the palatal surfaces and interproximal areas of posterior teeth. For precision, SMP_3A (p = 0.028) and SMP_2A (p = 0.003) showed a significantly lower precision in 3D analysis, but a comparable reproducibility in linear measurement to IOS.

CONCLUSION

TRIOS IOS (3Shape, Copenhagen, Denmark) exhibited lower trueness in 3D and linear accuracy analyses for complete-arch scans. The positions of the smartphone significantly enhanced trueness at the undercut region. SMP_2A and SMP_3A can be a potential alternative for precise linear measurement in complete-arch scans with selective use.

Three-dimensional analysis of mandibular morphology asymmetry and temporomandibular joint position in patients with unilateral Brodie bite

OBJECTIVE

Previous studies have shown unilateral posterior crossbite is associated with mandibular asymmetry in morphology and position. However, it remains unclear whether unilateral Brodie bite plays a similar role in mandibular development. Therefore, this study aims to investigate the morphological and positional symmetry of mandibles in patients with unilateral Brodie bite by three-dimensional anaylsis.

METHODS

Fourteen patients with unilateral Brodie bite (mean age 18.43 ± 4.24 years) and fourteen sex- and age-matched patients with normal occlusion (mean age 18.07 ± 5.48 years) underwent cone-beam computed tomography (CBCT) scans. 3D surface mesh models of their mandibles were established using Mimics Research 19.0. The surface matching percentage was compared between the original and mirrored mandible by Geomagic Control X software. Furthermore, the dimension and position of the temporomandibular joint (TMJ) were determined for both groups using InVivoDental 5.0.

RESULTS

For surface-to-surface deviation analysis, the percentage of mismatch in patients with unilateral Brodie bite was significantly higher than the control group at ±0.50 mm, ±0.75 mm, and ±1.00 mm tolerance (P < .001). In patients with unilateral Brodie syndrome, the condyles on the scissors-bite side showed a significantly more anterior position (P = .03), greater medial inclination (P < .01), and larger posterior TMJ space (P = .01) than the non-scissors-bite side.

CONCLUSION

Patients with unilateral Brodie bite exhibit a more asymmetrical mandibular morphology, with a greater anterior condylar position and posterior joint space on the scissors-bite side, indicating that early diagnosis and treatment may be necessary for patients with unilateral Brodie bite.

Tooth wear and bruxism: A scoping review

OBJECTIVE

This study presents a scoping review to determine the association between tooth wear and bruxism.

DATA

A protocol was developed a priori (Open Science Framework (DOI 10.17605/OSF.IO/CS7JX)). Established scoping review methods were used for screening, data extraction, and synthesis. Risk of bias was assessed using JBI tools. Direct associations between tooth wear and bruxism were assessed.

SOURCES

Embase, SCOPUS, Web of Science, Cochrane, and PubMed were searched.

STUDY SELECTION

Any clinical study containing tooth wear and bruxism assessment done on humans in any language was included. Animal, in-vitro studies and case reports were excluded.

CONCLUSIONS

Thirty publications reporting on the association between tooth wear and bruxism were included. The majority of publications were cross-sectional studies (90%) while only three were longitudinal (10%). Eleven papers assessed definitive bruxism for analysis (instrumental tools), one paper assessed probable bruxism (clinical inspection with self-report) and eighteen assessed possible bruxism (self-report). Of the eleven papers assessing definitive bruxism, eight also reported outcomes of non-instrumental tools. Tooth wear was mostly scored using indexes. Most studies reported no or weak associations between tooth wear and bruxism, except for the studies done on cervical tooth wear. When bruxism assessment was done through self-report, more often an association was found. Studies using multivariate analyses did not find an association between tooth wear and bruxism, except the cervical wear studies. Evidence shows inconclusive results as to whether bruxism and tooth wear are related or not. Therefore, well-designed longitudinal trials are needed to address this gap in the literature.

CLINICAL SIGNIFICANCE

Based on the evidence, dental clinicians should not infer bruxism activity solely on the presence of tooth wear.

Effect of implant scan body geometric modifications on the trueness and scanning time of complete arch intraoral implant digital scans: An in vitro study

STATEMENT OF PROBLEM

The effect of the surface geometry of implant scan bodies (ISBs) on the accuracy and scanning time of complete arch implant digital scans remains uncertain.

PURPOSE

The purpose of this in vitro study was to evaluate whether geometric modifications on implant scan bodies (nonmodified, subtractively modified, and additively modified ISBs) affect the trueness and scanning time of complete arch intraoral implant digital scans.

MATERIAL AND METHODS

A completely edentulous maxillary cast with 2 anterior parallel and two 17-degree posteriorly tilted implant abutment analogs was prepared. A digitized reference was created from this cast with polyetheretherketone (PEEK) (CARES Mono Scanbody for screw-retained abutment) ISBs by using a desktop scanner (E3). Three different groups were created: nonmodified (NM group), subtractively modified (SM group), and additively modified (AM group). For the NM group, no modifications were made to the ISBs. For the SM group, 4 round-shaped grooves were created on the buccal, lingual, mesial, and distal sides. For the AM group, PEEK beads were printed and cemented on the same areas of the ISB of the SM group. Fifteen consecutive scans were captured with an intraoral scanner (TRIOS 3) for each group, and the scanning time was recorded. By using a metrology software program, scans of each group were superimposed on the reference file to determine the 3D surface, linear, and angular position discrepancies of each ISB. Repeated-measures analyses of variance followed by univariate analysis and Bonferroni multiple comparison tests were performed to analyze the data (α=.05). To compare the mean time among groups, 1-way analysis of variance was performed followed by the Tukey post hoc tests.

RESULTS

Significant 3D surface, linear, and angular position discrepancies were found when measuring trueness among the NM, SM, and AM groups (P<.001). Discrepancies in 3D surface deviation were highest for the AM group (0.266 ±0.030 mm), and the lowest mean angular deviation values were for the SM group (0.993 ±0.062 degrees). However, the mean scanning time was not significantly different among the groups tested (P=.237).

CONCLUSIONS

For complete arch intraoral implant digital scans, subtractive modifications on ISBs enhanced scanning trueness, while additive modifications on ISBs decreased scanning trueness. However, implant scan body geometric modifications did not affect scanning time.

An evaluation of dental paste-like bulk-fill composite wear using intra-oral scanner

This study evaluates the wear resistance of dental paste-like bulk-fill composites compared to conventional paste-like composite resins using an intraoral scanner and 3-D analyzing software. Six different dental composite materials, including five bulk-fill composites and one conventional composite, were tested alongside natural human enamel as a control group. A computer-controlled chewing simulator for wear testing. A one-way ANOVA test was used to identify any significant differences between the means of the tested dental composite materials α=0.05. The results showed variability among bulk-fill composites, with some demonstrating wear resistance similar to conventional composites (p<0.05). Human enamel displayed the lowest wear values, but some bulk-fill composites matched this resistance(p>0.05). Significant variability was observed among bulk-fill composites but the results were comparable to those of conventional composites. The enamel control group demonstrated the lowest wear values, with some bulk-fill composites showing similar wear resistance. This study provides valuable information about the wear resistance of contemporary bulk-fill composite materials, commonly used in current clinical practice, contributing to enhancing clinical procedures.

Impact of the superimposition methods and the designated comparison area on accuracy analyses in dentate models

OBJECTIVES

To measure the impact of superimposition methods and the designated comparison area on accuracy analyses of dentate models using an ISO-recommended 3-dimensional (3D) metrology-grade inspection software (Geomagic Control X; 3D Systems; Rock Hill, South Carolina; USA).

MATERIALS AND METHODS

A dentate maxillary typodont scanned with a desktop scanner (E4; 3 Shape; Copenhagen; Denmark) and an intraoral scanner (Trios 4; 3 Shape; Copenhagen; Denmark) was used as reference. Eight groups were created based on the core features of each superimposition method: landmark-based alignment (G1); partial area-based alignment (G2); entire tooth area-based alignment (G3); double alignment combining landmark-based alignment with entire tooth area-based alignment (G4); double alignment combining partial area-based alignment with entire tooth area-based alignment (G5); initial automated quick pre-alignment (G6); initial automated precise pre-alignment (G7); and entire model area-based alignment (G8). Diverse variations of each alignment and two regions for accuracy analyses (teeth surface or full model surface) were tested, resulting in a total of thirty-two subgroups (n = 18). The alignment accuracy between experimental and reference meshes was quantified using root mean square (RMS) error as trueness and its repeatability as precision. The descriptive statistics, a factorial repeated measures analysis of variance (ANOVA) and a post hoc Tuckey multiple comparison tests were used to analyze the trueness, and precision (α = 0.05).

RESULTS

A total of 576 superimpositions were performed. The unique partial area-based superimposition method demonstrated the least precise alignment and was the sole group to exhibit a significant difference (p<.001). Automated initial pre-alignments demonstrated similar accuracy to other superimposition methods (p>.05). Double alignments did not result in accuracy improvement (p>.05). The designated comparison area displayed differences in both trueness (p<.001) and precision (p<.001), leading to an overall discrepancy of 8 ± 4 μm between selecting the teeth surface or full model surface.

CONCLUSIONS

The superimposition method choice within the tested software did not impact accuracy analyses, except when the alignment relies on a unique and reduced area, such as the palatal rugae, a single tooth, or three adjacent teeth on one side.

CLINICAL SIGNIFICANCE

The superimposition method choice within the tested ISO-recommended 3D inspection software did not impact accuracy analyses.

Evaluation of the accuracy of seven intraoral scanners for the full dentate and partially edentulous complete-arch mandibular casts: An in vitro comparison

Statement of problem

Intraoral scanners (IOSs) are widely used in dentistry, providing high accuracy in short-range scanning. Nevertheless, when scanning the full dental arch, it remains a challenge. Furthermore, there is a lack of studies reporting the differences in scan accuracy between dental arches with large-span mucosal areas and fully dentate casts or optimal IOS selection for different dental statuses.

Purpose

This study aimed to evaluate the accuracy and scanning time of different IOSs for full dentate (FD) and partially edentulous (PE) casts with missing teeth in the #34-#44 range and to determine the IOSs with the optimal clinical adaptability and scanning accuracy for different complete-arch casts.

Material and methods

Reference scans of two complete-arch (FD and PE) casts were obtained using a laboratory scanner (Ceramill Map 600). Subsequently, the same casts were scanned ten times each by seven IOSs (3Shape Trios 3, CS3600, Planmeca Emerald, iTero Element 5D, Medit i500, BAMBOO B1, and Shining Aoralscan 3), and the scanning time was recorded. The test data were superimposed on the reference scans for the selected areas, and three-dimensional deviations between the reference and test casts (trueness), and between test casts (precision) were determined using reverse engineering software (Geomagic Wrap). The dataset was analyzed using a two-factor analysis of variance with post-hoc Bonferroni tests.

Results

Two-factor analysis of variance revealed significant differences in accuracy and scanning time for different casts (P < 0.001) and IOSs (P < 0.001). For the FD cast, the i500 (0.35 ± 0.11 mm trueness) and CS3600 (0.23 ± 0.12 mm precision) performed worse than the remaining scanners. For the PE cast, the BAMBOO B1(0.89 ± 0.58 mm trueness; 0.88 ± 0.48 mm precision) performed worse than the remaining scanners. There were no differences in the accuracy of scanning between the Element 5D and Emerald for both cast types. However, the scanning time differed significantly between the different IOSs (P < 0.001). Regardless of the cast type, the fastest and slowest scans were performed by the Trios3 and CS3600 scanners respectively.

Conclusions

The accuracy and scanning time differed between the different IOSs and types of complete-arch casts.

Accuracy of edentulous full-arch implant impression: An in vitro comparison between conventional impression, intraoral scan with and without splinting, and photogrammetry

OBJECTIVES

The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry.

MATERIALS AND METHODS

An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations.

RESULTS

Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05).

CONCLUSIONS

Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

Trueness of crowns fabricated by using additively and subtractively manufactured resin-based CAD-CAM materials

STATEMENT OF PROBLEM

Advancements in digital dental technologies have enabled the use of different resin-based materials that can be fabricated either additively or subtractively. However, knowledge on the fabrication trueness of these materials is scarce.

PURPOSE

The purpose of this in vitro study was to investigate the trueness of crowns fabricated by using different resin-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials.

MATERIAL AND METHODS

A complete crown for a mandibular right first molar with a 30-μm cement space was designed in standard tessellation language (STL) format. This master STL (MC-STL) was used to fabricate 40 complete crowns with 4 different resin-based CAD-CAM materials and either additive (Crowntec [MS]) or subtractive techniques (Brilliant Crios [BC], breCAM.monoCOM [PMMA], and G-CAM [GR]; n=10). All crowns were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their STL files (TC-STLs). MC-STL and TC-STLs were transferred into a 3-dimensional analysis software program (Medit Link v2.4.4), and a trueness (overall, external, occlusal, intaglio occlusal, and marginal) analysis was performed by using the root mean square (RMS) method. The Kruskal-Wallis and Dunn tests were performed to analyze data (α=.05).

RESULTS

The test groups had significantly different deviations on all surfaces (P≤.001). MS crowns had higher overall (P≤.007) and external surface (P≤.001) deviations than GR and PMMA crowns, while the differences between GR and PMMA crowns were not significant (P≥.441). BC crowns had higher external surface deviations than GR crowns (P=.005), higher occlusal deviations than GR and MS crowns (P≤.007), and higher intaglio occlusal deviations than GR and MS crowns (P≤.009). However, BC crowns had lower marginal deviations than MS and GR crowns (P≤.018).

CONCLUSIONS

The brand of resin-based CAD-CAM materials affected the trueness of crowns. Additively manufactured crowns (MS) mostly had lower overall and external surface trueness than the other groups. Nevertheless, the deviation values of occlusal, intaglio occlusal, and marginal trueness were generally small; thus, the effect of the tested materials on clinical crown fit may be negligible.

Evaluation of repeatability of different alignment methods to obtain digital interocclusal records: An in vitro study

STATEMENT OF PROBLEM

The alignment of the maxillary and mandibular digital scans obtained with an intraoral scanner (IOS) generates digital interocclusal records. Although the accuracy of maxillary and mandibular digital scans obtained from an IOS is widely studied, the accuracy of digital interocclusal records obtained with them is not; even less studied is the accuracy (trueness and precision) of the alignment methods that are available to obtain them.

PURPOSE

The purpose of this in vitro study was to assess the precision under repeatability conditions (repeatability) of the different alignment methods used to obtain digital interocclusal records.

MATERIAL AND METHODS

Digital scans of maxillary and mandibular casts of a dentate healthy adult were acquired with an IOS. Casts were then mounted in maximum intercuspal position in a semi-adjustable mechanical articulator (1801 AR Model PSH Articulator), and left and right occlusal digital scans were acquired with the IOS. Occlusal digital scans were repeated 7 times under repeatability conditions. After obtaining each pair of occlusal digital scans, the software program of the IOS automatically aligned the maxillary and mandibular digital scans with occlusal digital scans (TRI method), resulting in 7 digital interocclusal records composed of aligned maxillary and mandibular digital scans and occlusal digital scans. All 7 sets of aligned digital scans were exported and realigned in a dental computer-aided design software program by means of global and reference alignment methods (EXO-B and EXO-R methods, respectively). To assess the repeatability, the 7 aligned digital scan sets of each group were repositioned in the common coordinate system by aligning maxillary digital scans, and repeatability was calculated in terms of the distance between the vertices of the mandibular digital scans for each of the possible nonrepeating combinations of pairs (7C2=21). The repeatability was tested by using the Kruskal-Wallis test for nonparametric distribution followed by the Mann-Whitney U test and Bonferroni correction for pairwise comparisons (α=.05).

RESULTS

The median with interquartile range for the TRI alignment method was 47 (27) μm for the EXO-B method 41 (25) μm and 16 (5) μm for EXO-R. The Kruskal-Wallis test showed statistical difference between test groups (P<.05). The post hoc Dunn test with Bonferroni adjustment detected significant statistical differences between the EXO-R-TRI (P<.001) and EXO-R-EXO-B (P<.001) alignment methods.

CONCLUSIONS

This study found that the alignment method could influence the repeatability of digital interocclusal records. The reference best-fit alignment method (EXO-R) provided better repeatability.

Effect of printing layer thickness on the trueness of 3-unit interim fixed partial dentures

STATEMENT OF PROBLEM

Three-dimensional printing has facilitated the fabrication processes in dentistry. However, knowledge on the effect of layer thickness on the trueness of 3D printed fixed partial dentures (FPDs) is lacking.

PURPOSE

The purpose of this in vitro study was to compare the effect of printing layer thickness on the trueness of 3-unit interim FPDs fabricated by using additive manufacturing with that of those fabricated by subtractive manufacturing.

MATERIAL AND METHODS

The right first premolar and first molar teeth of a dentate mandibular model were prepared for a 3-unit restoration and then digitized by using an intraoral scanner. A 3-unit interim FPD was designed to fabricate 40 restorations by using either the additive (NextDent C&B MFH) with layer thicknesses of 20 μm (n=10), 50 μm (n=10), and 100 μm (n=10) or subtractive manufacturing technique (Upcera) (milled, n=10). After fabrication, the interim FPDs were digitized by using the same intraoral scanner and were superimposed over the design data by using a 3D analysis software program. Root mean square (RMS) was used to analyze the trueness of the restorations at 4 different surfaces (external, intaglio, marginal area, and intaglio occlusal) and as a complete unit (overall). Data were analyzed with the Kruskal-Wallis and Wilcoxon tests with Bonferroni correction (α=.05).

RESULTS

The 100-μm-layer thickness interim FPDs showed the greatest overall (P≤.015), external (P≤.021), and intaglio occlusal (P≤.021) deviations, whereas the milled interim FPDs showed the lowest (P=.001). No significant differences were found among the test groups for marginal RMS (P≥.108). The differences between the 50-μm-layer thickness and 100-μm-layer thickness interim FPDs for the intaglio surface deviations (P=.064) and between the 20-μm-layer thickness and 50-μm-layer thickness interim FPDs for each surface tested were not statistically significant (P≥.108).

CONCLUSIONS

The printing layer thickness had a significant effect on the trueness of the additively manufactured interim FPDs. However, subtractively manufactured interim FPDs presented higher trueness than those additively manufactured, regardless of the printing layer thickness.

Occlusal caries detection and monitoring using a 3D intraoral scanner system. An in vivo assessment

OBJECTIVE

To assess the agreement in detecting and monitoring occlusal caries over thirty months using conventional visual and radiographic assessment and an intraoral scanner system which supports automated caries scoring.

METHODS

Ninety-one young participants aged 12-19 years were included in the study. All occlusal surfaces were examined visually, radiographically (when indicated), and scanned with the TRIOS 4 intraoral scanner. TRIOS Patient Monitoring software (vers. 2.3, 3Shape TRIOS A/S, Denmark) was used for automated caries detection on the 3D digital models.

RESULTS

Fifty-five of the study participants were re-examined after 30-months. Significant differences regarding caries detection were found between the conventional methods and the automated caries scoring system (p < 0.01), with moderate positive percent agreement (49-61%) and high negative percent agreement (87-98%). All methods reported significant caries progression over the follow-up period (p < 0.01). However, the automated system showed significantly more caries progression than the other methods (p < 0.01).

CONCLUSIONS

The software for automated caries detection and classification showed moderate positive agreement and strong negative agreement with the conventional methods considering both the baseline and the follow-up assessments. The automated caries scoring system detected significantly fewer caries lesions and tended to underestimate the caries severity. All methods indicated significant caries progression over the follow-up period, while the automated system detected more caries progression.

CLINICAL SIGNIFICANCE

The TRIOS system supporting automated occlusal caries detection and classification can assist in detecting and monitoring occlusal caries on permanent teeth as a complementary tool to the conventional methods. However, the operator should be aware that the automated system shows a tendency to underestimate the caries presence and lesion severity.

Digital registration versus cone-beam computed tomography for evaluating implant position: a prospective cohort study

BACKGROUND

Postoperative cone-beam computed tomography (CBCT) examination is considered a reliable method for clinicians to assess the positions of implants. Nevertheless, CBCT has drawbacks involving radiation exposure and high costs. Moreover, the image quality can be affected by artifacts. Recently, some literature has mentioned a digital registration method (DRM) as an alternative to CBCT for evaluating implant positions. The aim of this clinical study was to verify the accuracy of the DRM compared to CBCT scans in postoperative implant positioning.

MATERIALS AND METHODS

A total of 36 patients who received anterior maxillary implants were included in this clinical study, involving a total of 48 implants. The study included 24 patients in the single implant group and 12 patients in the dual implant group. The postoperative three-dimensional (3D) positions of implants were obtained using both CBCT and DRM. The DRM included three main steps. Firstly, the postoperative 3D data of the dentition and intraoral scan body (ISB) was obtained through the intraoral scan (IOS). Secondly, a virtual model named registration unit which comprised an implant replica and a matching ISB was created with the help of a lab scanner and reverse engineering software. Thirdly, by superimposing the registration unit and IOS data, the postoperative position of the implant was determined. The accuracy of DRM was evaluated by calculating the Root Mean Square (RMS) values after superimposing the implant positions obtained from DRM with those from postoperative CBCT. The accuracy of DRM was compared between the single implant group and the dual implant group using independent sample t-tests. The superimposition deviations of CBCT and IOS were also evaluated.

RESULTS

The overall mean RMS was 0.29 ± 0.05 mm. The mean RMS was 0.30 ± 0.03 mm in the single implant group and 0.29 ± 0.06 mm in the dual implant group, with no significant difference (p = 0.27). The overall registration accuracy of the IOS and CBCT data ranged from 0.14 ± 0.05 mm to 0.21 ± 0.08 mm.

CONCLUSION

In comparison with the 3D implant positions obtained by CBCT, the implant positions located by the DRM showed clinically acceptable deviation ranges. This method can be used in single and dual implant treatments to assess the implant positions.

Quantifying error introduced by iterative closest point image registration

OBJECTIVES

The aim of this paper was to quantify the analysis error introduced by iterative closest point (ICP) image registration. We also investigated whether a subsequent subtraction process can reduce process error.

METHODS

We tested metrology and two 3D inspection software using calibration standards at 0.39 μm, and 2.64 μm and mathematically perfect defects (softgauges) at 2 and 20 μm, on free form surfaces of increasing complexity and area, both with and without registration. Errors were calculated in percentage relative to the size of the defect being measured. Data were analysed in GraphPad Prism 9, normal and two-way ANOVA with post-hoc Tukey's was applied. Significance was inferred at p < 0.05.

RESULTS

Using ICP registration introduced errors from 0 % to 15.63 % of the defect size depending on the surface complexity and size of the defect. Significant differences were observed in analysis measurements between metrology and 3D inspection software and within different 3D inspection software, however, one did not show clear superiority over another. Even in the absence of registration, defects at 0.39 μm, and 2.64 μm produced substantial measurement error (13.39-77.50 % of defect size) when using 3D inspection software. Adding an additional data subtraction process reduced registration error to negligible levels (<1 % independent of surface complexity or area).

CONCLUSIONS

Commercial 3D inspection software introduces error during direct measurements below 3 μm. When using an ICP registration, errors over 15 % of the defect size can be introduced regardless of the accuracy of adjacent registration surfaces. Analysis output between software are not consistently repeatable or comparable and do not utilise ISO standards. Subtracting the datasets and analysing the residual difference reduced error to negligible levels.

CLINICAL SIGNIFICANCE

This paper quantifies the significant errors and inconsistencies introduced during the registration process even when 3D datasets are true and precise. This may impact on research diagnostics and clinical performance. An additional data processing step of scan subtraction can reduce this error but increases computational complexity.

Coordinate-based data analysis of the accuracy of five intraoral scanners for scanning completely dentate and partially edentulous mandibular arches

STATEMENT OF PROBLEM

Current methods for assessing the accuracy of intraoral scanners (IOSs) that reduce errors and provide comprehensive data compared with previous methods are lacking.

PURPOSE

The purpose of this in vitro study was to present a coordinate-based data analysis method to compare the accuracy of 5 IOSs for scanning completely dentate and partially edentulous casts.

MATERIAL AND METHODS

Reference scans of 2 complete arch casts (completely and partially dentate) were digitized using a high-precision laboratory scanner (Ceramill Map 600). Each cast was scanned 10 times each using 5 IOSs (3Shape TRIOS 3, Planmeca Emerald, iTero Element 5D, Medit i500, and Shining Aoralscan 3). The dataset of all 10 test groups was analyzed by using a reverse engineering software program (Geomagic Wrap). Each test cast was aligned with the reference cast by 3-dimensional (3D) superimposition to determine the translation and rotation along the x-, y-, and z-axes. The dataset was analyzed using the Kruskal-Wallis and post hoc Bonferroni tests (α=.05).

RESULTS

Significant differences were observed in all parameters among all scanners when scanning the same cast (P<.05). Significant differences were observed in at least 1 parameter for all scanners, except Element 5D after scanning different casts using the same scanner. Deviations in the test data generally relocated toward the mesial, buccal, and apical sides, and the casts were almost always rotated clockwise around the y-axis and counterclockwise around the z-axis. For the completely dentate cast, among all IOSs, Element 5D demonstrated the highest accuracy in most of the measured parameters, specifically in the y-axis translation (0.06[0.07] mm), z-axis translation (0.08[0.05] mm), and y-axis rotation (0.21[0.16] degree) (P<.05). For the partially edentulous cast, Element 5D displayed higher accuracy in most of the measured parameters, including the x-axis translation (0.11[0.14] mm) and z-axis rotation (0.12[0.18] degree) (P<.05). Emerald also displayed higher accuracy in most of the measured parameters, including the y-axis translation (0.05[0.08] mm) and y-axis rotation (0.14[0.12] degree) (P<.05). Element 5D exhibited no difference in the scanning accuracy between the 2 types of casts (P>.05).

CONCLUSIONS

Element 5D offered a high level of accuracy and was an appropriate scanner for both situations. The method presented in this study provides a good assessment of accuracy deviations in complete arch scans using 3D coordinate-based data analysis.

Two-year clinical performance of dual- and light-cure bulk-fill resin composites in Class ӀӀ restorations: a randomized clinical trial

OBJECTIVE

This study aimed to compare the clinical performance of dual- and light-cure bulk-fill resin composites (BFRCs) in Class ӀӀ restorations after 2 years.

MATERIALS AND METHODS

A double-blinded, prospective, randomized clinical trial (RCT) was conducted following the CONSORT (Consolidated Standard of Reporting Trials) guidelines. Forty patients were enrolled in the study. Each patient received three compound Class ӀӀ restorations. One dual-cure (Fill-Up; Coltene Waledent AG) and two light-cure (QuiXfil; Dentsply, and Tetric N-Ceram Bulk Fill; Ivoclar Vivadent) BFRCs were used for 120 Class ӀӀ restorations. A universal adhesive (ONE COAT 7 UNIVERSAL; Coltene Waledent AG) was used with all restorations. Restorations were clinically evaluated after 1 week (baseline), 6 months, 12 months, 18 months, and finally after 24 months using the FDI World Dental Federation (FDI) criteria. The Kruskal-Wallis test was used for comparison between BFRCs groups at baseline and at each recall period, and the Wilcoxon signed-rank test was used for comparing different follow-up times of each BFRC to baseline. The level of significance was set at p < 0.05.

RESULTS

All BFRCs restorations showed only minor changes and revealed no statistically significant differences between their clinical performance for all evaluated parameters at all recall periods; also, there was no statistically significant difference between all recall periods and baseline for all evaluated parameters.

CONCLUSION

The two-year clinical performance of dual-cure BFRC was comparable to light-cure BFRCs in Class ӀӀ restorations.

CLINICAL RELEVANCE

Dual- and light-cure BFRCs showed excellent clinical performance in Class ӀӀ restorations after a 2-year clinical follow-up.

Different Methods of Scan Alignment in Erosive Tooth Wear Measurements: An In Vitro Study

BACKGROUND

Model alignment in cases of erosive tooth wear can be challenging, and no method has been reported to outweigh the others.

METHODS

Extracted human teeth were mounted on two models and scanned at different times, from 1 h to 2 weeks, with an intraoral scanner (3Shape TRIOS 4) before and after immersion in Monster® energy drink and tap water. The scans were superimposed (3Shape TRIOS Patient Monitoring, Version 2.2.3.3, 3Shape A/S, Copengagen, Denmark). Best fit, best-fit tooth comparison, reference best fit using fillings, and palatal rugae as reference points were used for alignment. Surface profile differences were calculated in a cross-section view. The nonparametric Bland-Altman and Kruskal-Wallis tests were used.

RESULTS

First, statistically significant differences were marked after 4 days of immersion. The measurements obtained after 2 weeks of immersion were statistically significantly different from the measurements obtained at the different time points until 1 week. No statistically significant differences (p < 0.05) were observed among the alignment methods at any time.

CONCLUSION

In comparison to the best-fit model, both palatal rugae and fillings can be used. The best-fit tooth comparison method is a reliable option; however, it should be used with caution in cases of major surface loss.

3D quantitative analysis and SEM qualitative analysis of natural antagonist enamel opposing CAD-CAM monolithic zirconia or lithium disilicate tooth-supported crowns versus enamel opposing natural enamel

PURPOSE

This study aimed to evaluate the maximum vertical wear, volume wear, and surface characteristic of antagonist enamel, opposing monolithic zirconia or lithium disilicate crowns.

MATERIALS AND METHODS

The study comprised 24 participants (n = 12), who were randomly allocated to receive either a 5 mol% Y-TZP or a lithium disilicate crown in positions which would oppose the natural first molar tooth. The contralateral first molar along with its antagonist was considered as the enamel opposing natural enamel control. Data collection was performed using an intraoral scanner and polyvinylsiloxane impression. The means of the maximum vertical loss and the volume loss at the occlusal contact areas of the crowns and the various natural antagonists were measured by 3D comparison software. A scanning electron microscope was subsequently used to assess the wear characteristics.

Results

The one-year results from 22 participants (n = 11) indicated no significant differences when comparing the zirconia crown's antagonist enamel (40.28 ± 9.11 µm, 0.04 ± 0.02 mm3) and the natural enamel wear (38.91 ± 7.09 µm, 0.04 ± 0.02 mm3) (P > .05). Also, there is no significant differences between lithium disilicate crown's antagonist enamel (47.81 ± 9.41 µm, 0.04 ± 0.02 mm3) and the natural enamel wear (39.11 ± 7.90 µm, 0.04 ± 0.02 mm3) (P > .05).

Conclusion

While some studies suggested that monolithic zirconia caused less wear on opposing enamel than lithium disilicate, this study found similar wear levels to enamel for both materials compared to natural teeth.

Trueness and precision of combined healing abutment scan body system scans at different sites of maxilla after multiple repositioning of the scan body

OBJECTIVES

To evaluate the accuracy of the scans of the combined healing abutment-scan body (CHA-SB) system located at different sites of the maxilla when SBs are replaced in between each scan.

METHODS

Three SBs were seated into HAs located at the central incisor, first premolar, and first molar sites of a maxillary model inside a phantom head, and the model was scanned extraorally (CEREC Primescan SW 5.2). This procedure was repeated with new SBs until a total of 10 scans were performed. Standard tessellation language files of CHA-SBs at each implant location were isolated, transferred into analysis software (Geomagic Control X), and superimposed over the proprietary library files to analyze surface (root mean square), linear, and angular deviations. Trueness and precision were evaluated with one-way analysis of variance and Tukey tests. The correlation between surface and angular deviations was analyzed with Pearson's correlation (α=0.05).

RESULTS

Molar implant scans had the highest surface and angular deviations (P≤.006), while central incisor implant scans had higher precision (surface deviations) than premolar implant scans (P=.041). Premolar implant scans had higher accuracy than central incisor implant scans on the y-axis (P≤.029). Central incisor implant scans had the highest accuracy on the z-axis (P≤.018). A strong positive correlation was observed between surface and angular deviations (r = 0.864, P<.001).

CONCLUSION

Central incisor implant scans mostly had high accuracy and molar implant scans mostly had lower trueness. SBs were mostly positioned apically; however, the effect of SB replacement can be considered small as measured deviations were similar to those in previous studies and the precision of scans was high.

CLINICAL SIGNIFICANCE

Repositioning of scan bodies into healing abutments would be expected to result in similar single crown positioning regardless of the location of the implant, considering high scan precision with the healing abutment-scan body system. The duration of the chairside adjustments of crowns in the posterior maxilla may be longer than those in the anterior region.

Understanding Error Patterns: An Analysis of Alignment Errors in Rigid 3D Body Scans

Three-dimensional body scanners are attracting increasing interest in various application areas. To evaluate their accuracy, their 3D point clouds must be compared to a reference system by using a reference object. Since different scanning systems use different coordinate systems, an alignment is required for their evaluation. However, this process can result in translational and rotational misalignment. To understand the effects of alignment errors on the accuracy of measured circumferences of the human lower body, such misalignment is simulated in this paper and the resulting characteristic error patterns are analyzed. The results show that the total error consists of two components, namely translational and tilt. Linear correlations were found between the translational error (R2 = 0.90, … 0.97) and the change in circumferences as well as between the tilt error (R2 = 0.55, … 0.78) and the change in the body's mean outline. Finally, by systematic analysis of the error patterns, recommendations were derived and applied to 3D body scans of human subjects resulting in a reduction of error by 67% and 84%.

Effect of industrial scanner and framework material interaction on the marginal gaps of CAD-CAM complete arch implant frameworks

STATEMENT OF PROBLEM

Structured-light and computed tomography industrial scanners have been used as reference scanners to measure marginal gaps between implants and superstructures. However, the effect of framework material on the scanners' ability to detect gaps and on precision has not yet been evaluated.

PURPOSE

The purpose of this in vitro study was to investigate the interaction between the industrial scanner and framework material on measured marginal gaps of implant-supported fixed complete arch frameworks made from titanium and polymethylmethacrylate and on the precision of scans.

MATERIAL AND METHODS

A completely edentulous maxillary model with 4 implants and multiunit abutments at the first molar and canine sites was digitized by using a laboratory scanner. Implant-supported frameworks were milled from titanium and polymethylmethacrylate (n=5). Each framework was secured on the left molar site abutment. The marginal gaps between the frameworks and abutment sites without a screw were measured by using an industrial structured-light scanner and an industrial computed tomography scanner. The effect of the scanner, the framework material, and their interaction on measured gaps was analyzed by applying linear regressions and weighted least square methods. The F-statistics was used with Bonferroni corrections for precision analysis (α=.05).

RESULTS

No significant effect of scanner, material, or their interaction was found on the marginal gaps at the canine sites. The titanium framework gaps detected by using the computed tomography scanner were greater than those detected by using the structured-light scanner at the right molar site (estimated difference in means=0.054 mm; P=.003) and overall (estimated difference in means=0.023 mm; P=.033). The structured-light scanner's precision was higher than that of the computed tomography scanner when titanium frameworks were scanned (P=.001). The computed tomography scanner's precision was higher when scanning polymethylmethacrylate frameworks than when scanning titanium frameworks (P=.03).

CONCLUSIONS

Framework material and industrial scanner interaction affected the measured gaps. The computed tomography scanner detected greater marginal gaps with low precision when scanning titanium frameworks than the structured-light scanner. The sample size, the use of only 2 types of materials, and a laboratory scanner to obtain the computer-aided design file should be considered when interpreting the results.

Effect of scan powder and scanning technology on measured deviations of complete-arch implant supported frameworks digitized with industrial and intraoral scanners

OBJECTIVES

To evaluate the suitability of intraoral scanners (IOSs) to analyze the fabrication trueness of titanium complete-arch implant-supported frameworks by comparing with an industrial-grade scanner and investigate how anti-reflective scan powder affects measured deviations.

METHODS

Ten titanium complete-arch implant-supported frameworks were milled from a reference standard tessellation language (STL) file. An industrial-grade blue light scanner (ATOS Core 80 (AT)) and three IOSs (Primescan (PS), TRIOS T3 (T3), and TRIOS T4 (T4)) with (PS-P, T3-P, and T4-P) or without (PS, T3, and T4) anti-reflective scan powder application were used to generate test STL (TSTL) files of the frameworks. Reference STL and TSTLs were imported into a metrology-grade analysis software (Geomagic Control X) and whole surface root mean square (RMS) values were calculated. Another software (Medit Link v 2.4.4) was used to virtually isolate marginal surfaces of all STL files and marginal RMS values were calculated by using the same metrology-grade analysis software. A linear mixed effects model was used to compare the transformed deviations of the scans performed by using each IOS (with or without powder) with the deviations of those performed by using the reference AT scanner within each surface, where a Box-Cox type transformation was used for variance stability. Bonferroni corrected post-hoc tests were used to compare conditions within each IOS (α=0.05).

RESULTS

All IOSs had significantly higher whole surface and marginal RMS values than AT, regardless of the condition (P≤.002). However, scan powder application did not affect the whole surface and marginal RMS values in scans of tested IOSs (P≥.054).

CONCLUSION

Measured whole surface and marginal deviations in all IOS scans performed with or without the use of scan powder were higher than those in AT scans. The application of anti-reflective scan powder did not affect the deviations in scans of tested IOSs.

CLINICAL SIGNIFICANCE

Even though deviations measured in the scans of tested scanners were significantly different than those in the reference scanner, the maximum raw mean difference was 37.33 µm and the maximum raw confidence interval value of estimated differences was 47.88 µm, which can be considered clinically small taking into account the size of the frameworks tested. Therefore, tested intraoral scanners may be feasible to scan prostheses similar to or smaller than tested frameworks for fabrication trueness analysis, which may facilitate potential clinical adjustments.

Comparison of the Time and Accuracy of Intraoral Scans Performed by Dentists, Nurses, Postgraduates, and Undergraduates

OBJECTIVE

This study aimed to assess the scanning time (ST) and accuracy of 10 repeated upper and lower dentition scans by four groups of operators with different professional backgrounds.

METHODS

There were a total of 32 participants, including dentists, nurses, postgraduates, and undergraduates (n=8). They received the same training about intraoral scanning and then performed 10 repeat scans on the plaster maxillary and mandibular dentition models in a manikin head, with the first five scans being the T1 phase and the last five scans being the T2 phase. Each ST was recorded. Trueness and precision were evaluated by root mean square (RMS) value gained from alignments of corresponding virtual models. For statistical analysis, the paired-sample t-tests, one-way ANOVA, and Pearson correlation tests were employed (α=0.05).

RESULTS

Limiting the comparison in scan phase and scan target the sequence of STs for the four groups was the same (p<0.05), by which undergraduates, postgraduates, nurses, and dentists were in descending order. Undergraduates gained the best precision, followed by postgraduates, dentists, and nurses, in both maxillary and mandibular scanning (p<0.05). Compared with corresponding items of the T1 phase, the trueness of the T2 phase was much higher (p<0.05), while the ST of the T2 phase was much shorter (p<0.05).

CONCLUSIONS

The operator's professional background affects the precision and scanning time but not the trueness. Most dental personnel have good access to the intraoral scanner. As the number of scans increased, the accuracy and scanning efficiency also improved.