Digital workflow: In vitro accuracy of 3D printed casts generated from complete-arch digital implant scans

Trueness of 3-dimensionally printed complete arch implant analog casts

STATEMENT OF PROBLEM

Although a completely digital workflow has numerous advantages, a physical definitive cast may be especially helpful for the accurate assembly of components of complex complete arch-fixed prostheses, the evaluation of esthetic and occlusion features, or prosthesis fabrication. Research on the accuracy of additive complete arch casts with implants positioned with a large anterior-posterior (A-P) spread is sparse.

PURPOSE

The purpose of this in vitro study was to evaluate the trueness of complete arch 4-implant analog casts with a large A-P distribution fabricated with different 3-dimensional (3D) printers.

MATERIAL AND METHODS

Ten systems were evaluated representing currently available printing technologies and materials for the additive fabrication of complete arch 4-implant analog casts and compared for deviations in the X-, Y-, and Z-axes from the master model scan (MMS), recorded in standard tessellation language (STL). The MMS was provided to the laboratory selected by the manufacturer, permitting them to create their specific cast with computer-aided design and computer-aided manufacture specific to a particular system, including analog receptacle offset settings. Laboratories fabricated N=10 casts and affixed analogs. A conventional splinted impression and stone cast (CON) was fabricated as a control. The casts were scanned with a precision laboratory scanner (D2000; 3Shape A/S), and files were imported into the Convince metrology software program (3Shape A/S) for comparison with the MMS for mean deviations in the X-, Y-, and Z- axes. A 2-way ANOVA and the Tukey HSD comparison tests were performed between system groups and the 4 implant locations (α=.05). Comparative color maps were used to determine dimensional changes of the edentulous ridges.

RESULTS

For 2-dimensional deviations from the MMS in each of the 3 axes, the printer type, implant location, and interaction between those 2 variables were found to be statistically significant (P<.05). Comparisons among printers showed the smallest deviations for Asiga Pro 4K (ASG) and Stratasys Origin One (ORI) printers in both the X- and Y-axes and for CON in the Z-axis. For 3D deviations, comparison among printers indicated that ORI, SprintRay Pro55 S (SPR), and Ackuretta SOL (ACK) had the largest deviations, whereas CON and ASG showed the smallest deviations. Comparison color mapping demonstrates a disparity between printed model dimensional changes and implant analog positioning since the color maps of the casts' ridge crests were not in concordance with the results of the implant analog deviations.

CONCLUSIONS

ASG, 3D Systems ProJet MJP 2500 Plus (MJP), 3D Systems NextDent 5100 (NEX), Stratasys J5 DentaJet (PJ5), Ivoclar PrograPrint PR5 (PR5), and Prodways ProMaker LD20 (PWY) were similar in terms of 3D deviations to the conventional stone cast control. Comparative color mapping showed the direction and quantity of the dimensional changes of the ridge crest frequently did not correlate with the 3D deviations of implant analog positioning. Implant analog insertion errors were predominantly responsible for analog position 3D deviations rather than the polymerization shrinkage of additive photopolymers.

Three-Dimensional-Printed Osteochondral Scaffold with Biomimetic Surface Curvature for Osteochondral Regeneration

OBJECTIVES

Treatment of osteochondral defects is hindered by several challenges, including the failure of traditional scaffolds with a predefined cylindrical or cuboid shape to comprehensively match the natural osteochondral tissue. Herein, we employed reverse modeling and three-dimensional (3D) printing technologies to prepare subchondral bone and cartilage.

METHODS

The osteochondral scaffold was prepared by bonding the subchondral bone and cartilage layers, and the curvature distribution and biomechanical behavior were compared with those of the native tissue. Biocompatibility and osteochondral regeneration performance were further evaluated using cell adhesion and proliferation assays, as well as animal osteochondral defect repair tests.

RESULTS

We found that increasing the printing temperature or decreasing the layer height improved the dimensional accuracy of printed subchondral bones, whereas increasing the exposure time or decreasing the layer height enhanced the dimensional accuracy of the printed cartilage. Biomimetic scaffolds exhibited curvature distribution and biomechanical behavior more similar to native tissues than traditional cylindrical scaffolds. Incorporating gelatin methacryloyl into poly (ethylene glycol) diacrylate markedly improved the biocompatibility, and correspondingly prepared osteochondral scaffolds had better osteochondral regeneration ability than the traditional scaffolds.

CONCLUSIONS

Osteochondral scaffolds exhibiting biomimetic morphology and an internal structure could be prepared based on reverse modeling and 3D printing, facilitating personalized osteochondral injury treatment.

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.

Current applications of 3D printing in dental implantology: A scoping review mapping the evidence

OBJECTIVES

This scoping review aimed to identify the available evidence in the use of 3D printing technology in dental implantology. Due to the broad scope of the subject and its application in implantology, three main areas of focus were identified: (1) customized dental implants, (2) manufacturing workflow for surgical implant guides, and (3) related implant-supported prostheses factors, which include the metallic primary frameworks, secondary ceramic or polymer superstructures, and 3D implant analog models.

MATERIALS AND METHODS

Online databases (Medline, Cochrane, Embase, and CINAHL) were used to identify the studies published up to February 2023 in English. Two experienced reviewers performed independently the screening and selection among the 1737 studies identified. The articles evaluated the additive manufacturing (AM) technology, materials, printing, and post-processing parameters regarding dental implantology.

RESULTS

The 132 full-text studies that met the inclusion criteria were examined. Thirteen studies of customized dental implants, 22 studies about the workflow for surgical implant guides, and 30 studies of related implant-supported prostheses factors were included.

CONCLUSIONS

(1) The clinical evidence about AM titanium and zirconia implants is scarce. Early data on survival rates, osseointegration, and mechanical properties are being reported. (2) 3D printing is a proven manufacturing technology to produce surgical implant guides. Adherence to the manufacturer's instructions is crucial and the best accuracy was achieved using MultiJet printer. (3) The quality of 3D printed prosthetic structures and superstructures is improving remarkably, especially on metallic alloys. However, better marginal fit and mechanical properties can be achieved with milling technology for metals and ceramics.

Effect of a Novel 'Scan Body' on the In Vitro Scanning Accuracy of Full-Arch Implant Impressions

OBJECTIVE

This in vitro study aimed to determine whether a newly designed arcuate scan body can improve intraoral scanning accuracy for implant rehabilitation of edentulous jaws.

MATERIAL AND METHODS

A master model containing 4 implant abutment replicas was fabricated and digitized with different scan bodies using an intraoral scanner. Four types of scan bodies were evaluated: original scan bodies (group OS), computer-aided design and computer-aided manufacturing (CAD/CAM) scan bodies without extension (group CS), CAD/CAM scan bodies with straight extension (group CSS), and CAD/CAM scan bodies with arcuate extension (group CSA). Conventional splinted open-tray impressions (group CI) were used as controls. The master model and the poured casts were digitized using a laboratory scanner. Impressions were repeated 10 times each in 5 groups. Scans in standard tessellation language format were exported to reverse engineering software and root mean square (RMS) values were used for trueness and precision assessments. In each group, 45 RMS values were acquired for precision evaluation and 10 RMS values were obtained for trueness assessment. Statistical evaluation was performed with the Kruskal-Wallis test and Dunn-Bonferroni test (α = 0.05).

RESULTS

The median trueness values were 41.40, 55.95, 39.80, 39.75, and 22.30 μm for group OS, CS, CSS, CSA, and CI, respectively. CI showed better trueness than OS (P = .020), CS (P < .001), and CSS (P = .035). The median precisions for group OS, CS, CSS, CSA, and CI were 47.40, 51.50, 43.90, 25.20, and 24.60 μm. respectively. The precision of CSA and CI were higher than OS (P < .001), CS (P < .001), and CSS (P < .001). Between CI and CSA, there was no significant difference (P = 1.000).

CONCLUSIONS

For full-arch implant rehabilitation, the scan body with arcuate extension could improve the intraoral scanning precision and showed similar 3-dimensional discrepancy compared to conventional splinted open-tray impressions.

The Evaluation of the Trueness of Dental Mastercasts Obtained through Different 3D Printing Technologies

In contemporary dentistry, several 3D printing techniques, including a stereolithography apparatus (SLA), digital light processing (DLP), liquid crystal display (LCD), and PolyJet 3D inkjet printing technology (PolyJet), are employed for model production. Despite their widespread use, there remains a paucity of the literature regarding the trueness and precision of these devices in dental applications. Existing studies comparing the accuracy of dental models manufactured by different printing technologies yield disparate conclusions regarding dental prosthesis manufacturing. This study aimed to test two null hypotheses: first, that the trueness of various new-generation 3D printers is equivalent, and second, that the trueness of printing by these printers is sufficient for achieving high-precision mastercasts in dental prosthodontics manufacturing. The research focuses on evaluating the trueness of five contemporary dental 3D printers: Anycubic Mono X 6Ks (Hongkong Anycubic Technology Co., Hongkong, China), Asiga Max (Asiga, Sydney, Australia), Creo C5 (Planmeca Oy, Helsinki, Finland), Form 3B (Formlabs, Boston, MA, USA), and J5 Dentajet (Stratasys Ltd., Eden Prairie, MN, USA). The methodology employed involved the creation of a digital test object using Blender software, adhering meticulously to the dimensions outlined in ISO standard 20896-1. These dimensions were chosen to be both relevant for this study and representative of clinical scenarios. Subsequently, the test object was printed and precise measurements were conducted utilizing a metrology-type Nikon XTH225 ST Reflection target in conjunction with VGStudio MAX analysis software. The results of our investigation revealed clinically negligible deviations in ball dimensions across all printers, with the maximum observed deviations ranging between 1.17% and 2.03% (notably observed in the Creo C5 printer). Transversal distortion exhibited variance based on the linear accuracy of each printer, with Stratasys21 and Formlabs 3B demonstrating superior accuracy among the evaluated printers. Distortions in the analyzed dimensions (specifically, anterior b-c, posterior a-d, and oblique a-c) were found to be uniform. In conclusion, while the first null hypothesis was rejected, indicating variations in trueness among the 3D printers assessed, our findings affirm the suitability of all five analyzed 3D printers for clinical applications. Consequently, these printers can be utilized for the fabrication of high-precision mastercasts in dental prosthodontics manufacturing.

Dimensional Accuracy of Different Three-Dimensional Printing Models as a Function of Varying the Printing Parameters

Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With digital light processing (DLP) and stereolithography (SLA) printing systems, 126 models were produced in several printing runs-SolFlex350 (S) (DLP, n = 24), CaraPrint 4.0 (C) (DLP, n = 48) and Form2 (F) (SLA, n = 54)-and their accuracy was compared with plaster and milled polyurethane models. In addition to the positioning on the build platform, a distinction was made between parallel and across arrangement of the models to the printer's front, solid and hollow models, and printing with and without support structures. For accuracy assessment, five measurement sections were defined on the model (A-E) and measured using a calibrated digital calliper and digital scans in combination with the GOM Inspect Professional software 2021. The mean deviation between the measurement methods for all distances was 79 µm. The mean deviation of the models from the digital SOLL model were 207.1 µm for the S series, 25.1 µm for the C series and 141.8 µm for the F series. While positioning did not have an influence, there were clinically relevant differences mainly regarding the choice of printer, but also individually in alignment, model structure and support structures.

Spatial Trueness Evaluation of 3D-Printed Dental Model Made of Photopolymer Resin: Use of Special Structurized Dental Model

(1) Background: Various 3D printers are available for dental practice; however, a comprehensive accuracy evaluation method to effectively guide practitioners is lacking. This in vitro study aimed to propose an optimized method to evaluate the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a special structurized dental model, and provide the preliminary evaluation results of six 3D printers. (2) Methods: A structurized dental model comprising several geometrical configurations was designed based on dental crown and arch measurement data reported in previous studies. Ninety-six feature sizes can be directly measured on this original model with minimized manual measurement errors. Six types of photo-curing 3D printers, including Objet30 Pro using the Polyjet technique, Projet 3510 HD Plus using the Multijet technique, Perfactory DDP and DLP 800d using the DLP technique, Form2 and Form3 using the SLA technique, and each printer's respective 3D-printable dental model materials, were used to fabricate one set of physical models each. Regarding the feature sizes of the simulated dental crowns and dental arches, linear measurements were recorded. The scanned digital models were compared with the design data, and 3D form errors (including overall 3D deviation; flatness, parallelism, and perpendicularity errors) were measured. (3) Results: The lowest overall 3D deviation, flatness, parallelism, and perpendicularity errors were noted for the models printed using the Objet30 Pro (overall value: 45 μm), Form3 (0.061 ± 0.019 mm), Objet30 Pro (0.138 ± 0.068°), and Projet 3510 HD Plus (0.095 ± 0.070°), respectively. In color difference maps, different deformation patterns were observed in the printed models. The feature size proved most accurate for the Objet30 Pro fabricated models (occlusal plane error: 0.02 ± 0.36%, occlusogingival direction error: -0.06 ± 0.09%). (4) Conclusions: The authors investigated a novel evaluation approach for the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a structurized dental model. This method can objectively and comprehensively evaluate the spatial trueness of 3D-printed dental models and has a good repeatability and generalizability.

In vitro comparative study between complete arch conventional implant impressions and digital implant scans with scannable pick-up impression copings

STATEMENT OF PROBLEM

Intraoral digital scan techniques have been widely used and sufficient evidence supports this technique in partially edentulous patients. However, the evidence supporting the use of intraoral scanners (IOSs) for edentulous patients is limited.

PURPOSE

The purpose of this in vitro study was to measure and compare the accuracy of complete arch conventional pick-up implant impressions with open and closed trays, complete arch digital implant scans with IOSs, and 3-dimensional (3D) printed casts from complete arch digital implant scans.

MATERIAL AND METHODS

Six implants were placed in a mandibular model. Scannable pick-up impression copings were inserted in the implants, scanned with a reference scanner, and exported in standard tessellation language (STL) format (Group Control). Splinted open-tray pick-up impressions (Group OT, n=5) and closed-tray pick-up impressions (Group CT, n=5) were made, and stone casts were fabricated. Digital scans (Group DS, n=5) were made with an IOS, and the STL files were exported to fabricate 3D printed casts (Group STL, n=5). Scannable pick-up impression copings were inserted in the dental implant analogs in Groups OT, CT, and STL and scanned with the reference scanner. Using a 3D inspection software program, the recording techniques were compared with the control. Root mean square (RMS) values were calculated from the control, and superimposed digitized casts from different recording techniques. Analysis of variance was used to determine differences in RMS values, and theTukey post hoc test was used to determine difference between different groups.

RESULTS

Group CT had the lowest mean dimensional difference when superimposed with Group Control, followed by Groups DS, OT, and STL. Significant differences were found in RMS values between Control and digitized casts fabricated with different techniques (P<.05). The post hoc Tukey test revealed that Group DS (P<.05) was significantly different from the other groups, while no significant difference was found among Groups CT, OT, and STL (P>.05).

CONCLUSIONS

Based on the findings of the present study, 3D printed casts from digital scans have the same accuracy as stone casts from conventional impressions in complete arch implant cases. Intraoral scans had the highest accuracy. Complete arch pick-up impression techniques using dual-functioning scannable pick-up impression copings are as accurate as splinted complete arch pick-up impressions.

A comparative analysis of the passivity of fit of complete arch implant-supported frameworks fabricated using different acquisition techniques

STATEMENT OF PROBLEM

The accuracy of intraoral scanners (IOSs) in recording edentulous jaws has improved recently. However, improvement in accuracy does not necessarily imply the clinical validity of the scans, and limited information is available regarding the manufacture of passively fitting prostheses.

PURPOSE

The purpose of this in vitro study was to analyze the passivity of complete arch screw-retained frameworks fabricated using different acquisition techniques.

MATERIAL AND METHODS

A 3-dimensional maxillary edentulous model to receive all-on-4 screw-retained frameworks was prototyped. Eighteen polymethylmethacrylate (PMMA) frameworks were fabricated with a 5-axis milling machine and divided into 3 groups according to the acquisition technique (n=6): scanned by using an IOS (CEREC Primescan; Dentsply Sirona), scanned with the aid of an auxiliary device by using the same IOS, and by using a conventional impression and then scanning the stone cast with an extraoral scanner (EOS). The passivity of fit of the frameworks was tested with the 1-screw test, the terminal screw of the framework assembly was tightened on the multiunit abutment (MUA), and the vertical marginal gap (µm) was measured at the other 3 framework-to-abutment interfaces by using a digital microscope at ×40 magnification. A modification to the 1-screw test was analyzed by tightening all screws and then unscrewing all except 1 of the anterior abutments. Data were explored for normality by using the theoretical quantile-quantile (Q-Q) plots and the Shapiro-Wilk test of normality. The Friedman test compared data between the different acquisition techniques; the tightening methods and locations (buccal and palatal) were used as the block variable. The post hoc Dunn test was used when the Friedman test was significant. The Kruksal-Wallis test compared the data from the 2 groups of the tightening methods and the 2 location groups. The aligned rank transformation (ART) ANOVA test was used for the interaction effects among the 3 variables. A multiway ANOVA was applied to the ranked data. (α=.05 for all tests).

RESULTS

Significant differences were found among all groups (P<.001). Regarding the passivity of fit, the mean vertical marginal gap was 50 µm for frameworks fabricated from an intraoral scan with the aid of an auxiliary device, 62 µm for frameworks fabricated by using an IOS, and 140 µm for frameworks fabricated by using an EOS. No significant difference was found among all groups regarding the tightening method (P=.355) or location measured (P=.175).

CONCLUSIONS

Digital scanning with the aid of an auxiliary device resulted in the best fit; however, digital approaches with or without the auxiliary device resulted in a more accurate fit with a smaller marginal gap than with the conventional impression.

A comprehensive review and update on the current state of computer-assisted rehabilitation in implant dentistry

AIM

This paper provides a comprehensive review of the established concepts and newer developments related to computer-assisted implant rehabilitation.

METHODS

Two independent researchers searched the English literature published to 31st December 2023 in the PubMed/Medline database for primary and secondary research and related publications on computer-assisted implant planning, computer-assisted implant placement and computer-assisted implant restoration.

RESULTS

A total of 58,923 papers were identified, 198 relevant papers were read in full text and 110 studies were finally included. Computer-assisted implant rehabilitation was found to result in more precise implant positioning than freehand placement. Advantages include reduced trauma and surgery time; disadvantages include reduced primary implant stability and higher cost.

CONCLUSION

Computer-assisted surgery is particularly indicated in cases of critical anatomy, but may encounter limitations in terms of cost, restricted mouth opening, visibility and adjustment of the surgical guides and the need for prior familiarisation with the procedure. Nonetheless, this surgical technique reduces the post-implant placement complication rate.

Comparative analysis of intaglio surface trueness of cement-retained implant-supported prostheses generated by a cast-free digital workflow and a three-dimensionally printed cast workflow

STATEMENT OF PROBLEM

Comparative analysis of the accuracy of the prostheses produced by a cast-free digital workflow and 3-dimensional (3D) printing cast workflow is lacking.

PURPOSE

The purpose of the present investigation was to compare the intaglio surface trueness of implant-supported prostheses fabricated by using 3 different digital workflows: cast-free computer-aided design (CAD), 3D printed cast CAD (direct insert), and 3D printed cast CAD (indirect insert).

MATERIAL AND METHODS

The laboratory data of 11 partially edentulous arches for prosthetic implant treatment were obtained. Three different workflows were tested to produce the cement-retained prostheses: cast-free CAD (Group CF), 3D printed cast CAD with direct insert (Group PD), and 3D printed cast CAD with indirect insert (Group PI). The intaglio surfaces of the prosthesis CAD data from Groups CF, PD, and PI were superimposed with 3D printed prosthesis scan data from Group CF to measure 3D surface deviation. Using the prosthesis CAD data from Group CF as a reference, those from Groups PD and PI were compared by superimposition analysis. The root mean square (RMS) estimates, positive average deviations, and negative average deviations were measured. The Kruskal-Wallis test and Dunn test with Bonferroni correction, and the Wilcoxon rank sum test were used for statistical analyses (α=.05).

RESULTS

Significant differences were found among the 3 groups when the 3D printed prosthesis scan data were referenced (P<.05). Group CF showed the lowest RMS, positive average deviation, and negative deviation values, while Group PI showed the highest values. Significant differences in the RMS, positive average deviation, and negative average deviation values were found between Groups PD and PI when the prosthesis CAD data (Group CF) were referenced (P<.05).

CONCLUSIONS

Among the 3 different workflows tested, the prostheses generated from the cast-free CAD flow showed significantly lower intaglio surface deviation than those generated from the 3D printed cast CAD flows, regardless of the insertion method of the implant replicas.

Effect of storage temperature on the dimensional stability of DLP printed casts

STATEMENT OF PROBLEM

Despite studies focusing on the accuracy and dimensional stability of additive manufacturing, research on the impact of storage conditions on these properties of 3-dimensional (3D) printed objects is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the influence of storage temperature on the dimensional stability of digital light processing (DLP) printed casts and to determine how different locations in printed casts react differently.

MATERIAL AND METHODS

A completely dentate maxillary typodont model was digitized with a desktop laser scanner. The typodont was subsequently modified with a software program by adding cuboids with a side length of 3 mm on both maxillary central incisors, first molars, and second molars. The file was saved in the standard tessellation language (STL) format. The modified digitized typodont was then processed through the DLP technology printing process with a desktop DLP printer and photopolymerizing resin. The casts were printed 32 times and stored in sealed plastic bags, shielded from light, and subjected to 4 different temperature conditions (-20 °C, 4 °C, 20 °C, and 37 °C, n=8 each). The cuboids on the central incisors were labeled as the P1 group, first molars as the P2 group, and second molars as the P3 group. The distance between the cuboids was measured 5 times, with results recorded immediately after cast production and at 1, 2, 3, 5, 7, 14, and 28 days after. Repeated analysis of variance (ANOVA) and the Tukey honestly significant difference (HSD) test were used to compare the recorded values among the groups (α=.05).

RESULTS

In the P1 group, the casts stored at -20 °C exhibited the smallest overall size change, with a mean ±standard deviation volume of 99.42 ±0.04% compared with the original casts after 28 days of storage. This was followed by the casts stored at 4 °C, 20 °C, and 37 °C, with remaining volumes of 99.39 ±0.06% (P=.139), 99.14 ±0.08% (P<.001), and 98.96 ±0.03% (P<.001), respectively. For the P2 and P3 groups, casts stored at 4 °C retained the most volume at 99.82 ±0.01%, whereas those stored at -20 °C, 20 °C, and 37 °C underwent greater changes, with remaining volumes of 99.66 ±0.03%, 100.32 ±0.02%, and 100.44 ±0.02%, respectively (P<.001). The P3 group exhibited a similar trend to that of the P2 group, with the casts stored at 4 °C remaining closest to the original dimensions at 99.86 ±0.02%, while casts stored at -20 °C showed 99.73 ±0.03% of the original volume and those stored at 20 °C and 37 °C expanded with volumes of 100.37 ±0.03% and 100.48 ±0.03%, respectively (P<.001).

CONCLUSIONS

DLP printed casts stored at 4 °C exhibited the greatest overall dimensional stability, followed sequentially by those stored at -20 °C, 20 °C, and 37 °C. Additionally, the study confirmed that the posterior and anterior teeth regions of DLP printed casts respond differently to different storage temperatures.

Effect of geometric heterogeneity using an auxiliary device on the accuracy of complete arch implant scanning: An in vitro study of different clinical simulations

STATEMENT OF PROBLEM

Intraoral scanning of implants supporting complete arch prostheses is limited because of the lack of geometric heterogeneity and unique reference points, creating inherent errors in the image stitching process by the scanner software program.

PURPOSE

The purpose of this in vitro study was to evaluate the significance of geometric heterogeneity on complete arch implant scanning by using a novel auxiliary geometric device. Three different clinical simulations were tested to assess its significance. The study also assessed whether scans produced using the auxiliary device would meet a clinically acceptable threshold.

MATERIAL AND METHODS

A total of 60 scans (n=20) were performed using an intraoral scanner in 3 different clinical simulations: 2 parallel implants, 4 parallel implants, and 4 implants with a 30-degree posterior angulation of the distal implants. Scanning alternated between using the auxiliary geometric scanning device (test groups; 4IP+, 4IA+, 2IP+) and not using the device (control groups; 4IP-, 4IA-, 2IP-). A reference scan for each model was prepared from a high precision laboratory scanner. The scans were analyzed for accuracy in 3-dimensional deviation, interimplant distance deviation, and angular deviation by using an inspection software program. The effect of the auxiliary device was statistically analyzed by comparing scans of the same group using the paired t test for normally distributed data and the Wilcoxon Signed Rank test when data were not normally distributed (α=.05).

RESULTS

Significant effects of the auxiliary geometric device were found in 3-dimensional, distance and angular deviations (P<.05). Scans performed using the device were significantly more accurate in most implant positions (P<.05). Linear and angular deviations were clinically acceptable for all test groups. However, the deviations were above the clinically acceptable threshold for the control groups.

CONCLUSIONS

Using an auxiliary geometric device significantly improved scanning accuracy and produced scans with clinically acceptable deviations, while standard digital scans exceeded the accepted clinical threshold.

Device trueness in passivity and misfit of CAD-CAM frameworks: Conventional versus printed casts

STATEMENT OF PROBLEM

Obtaining a passive and well-adapted framework is challenging when intraoral scanning edentulous arches with multiple implants. The trueness of the printed casts is unclear.

PURPOSE

The purpose of this clinical study was to evaluate the trueness of frameworks made from conventional and printed casts regarding clinical passivity and misfit.

MATERIAL AND METHODS

Ten participants with complete mandibular fixed implant-supported interim prostheses retained by 4 implants were included. Each participant had a conventional impression and a digital scan made. The digital scan was made using an innovative device. Both conventional and digital casts were made, and the virtual images were used for milling the digital framework in cobalt chromium alloy. All frameworks were evaluated for passivity and marginal vertical misfit with the single screw test, with 4 attempts consisting of the tightened screw position, a test with all screws tightened, and an interspersed tightening test. The Kruskal-Wallis test was used to evaluate the trueness of the tested device for framework construction through the single screw test on vertical marginal misfit in the conventional and printed groups (α=.008). The Friedman test was used to assess the effect of test type (α=.05), and the Wilcoxon test was used to identify group-to-group differences (α=.017).

RESULTS

The absence of space between the framework and the abutments and interferences during its placement, as well as good stability, were observed clinically. In laboratory analysis, greater framework misfits were observed in the printed group compared with the conventional group when the single screw test was applied. Comparing the 3 tests used, the greatest misfits were observed when the framework was screwed onto the printed cast.

CONCLUSIONS

The innovative device tested for the intraoral scanning of multiple implants had clinically acceptable accuracy for the construction of passive and adapted frameworks. The conventional cast was more accurate than the printed cast, with lower misfit values, in all tests.

Clear guidance to select the most accurate technologies for 3D printing dental models - A network meta-analysis✰

OBJECTIVES

Thus far, the findings of numerous studies conducted on the accuracy of three-dimensional (3D) printed dental models are conflicting. Therefore, the aim of the network meta-analysis (NMA) is to determine the accuracy of 3D printed dental models compared with digital reference models.

DATA

Studies comparing the accuracy of 3D printed full-arch dental models manufactured using different printing techniques to initial STL files were included.

SOURCES

This study was registered in PROSPERO (CRD42021285863). An electronic search was performed across four databases in November 2021, and search was restricted to the English language.

STUDY SELECTION

A systematic search was conducted based on a prespecified search query. 16,303 articles were pooled after the removal of the duplicates. Following study selection and data extraction, 11 eligible studies were included in the NMA in 6 subgroups. The outcomes were specified as trueness and precision and expressed as root mean square (RMS) and absolute mean deviation values. Seven printing technologies were analyzed: stereolithography (SLA), digital light processing (DLP), fused deposition modeling/fused filament fabrication (FDM/FFF), MultiJet, PolyJet, continuous liquid interface production (CLIP), and LCD technology. The QUADAS-2 and GRADE were used to evaluate the risk of bias and certainty of evidence.

CONCLUSIONS

SLA, DLP, and PolyJet technologies were the most accurate in producing full-arch dental models.

CLINICAL SIGNIFICANCE

The findings of the NMA suggest that SLA, DLP, and PolyJet technologies are sufficiently accurate for full-arch dental model production for prosthodontic purposes. In contrast, FDM/FFF, CLIP, and LCD technologies are less suitable for manufacturing dental models.

Application and evaluation of fused deposition modeling technique in customized medical products

The fused deposition modeling (FDM) technique has enormous potential for developing customized medical products with complicated structures. In this study, the application of the FDM technique to three medical products was investigated, and the risk factors affecting product quality were evaluated. For FDM-printed matrix and reservoir preparations, special attention should be paid to spacing width reduction and layered coating thickness. Therefore, spacing printing fidelity and interlayer bonding strength was established as unique indexes to characterize the effectiveness and safety of FDM-printed medicine. For FDM-printed orthopedic implants, layer height affected the dimensional deviation of surface morphology, which could be digitally evaluated. Moreover, internal structure affected the biomechanical behavior, which could be investigated using in silico simulation. The results reveal the broad application of FDM technology in customized medical products and might help to establish scientific and reasonable evaluation systems for them.

Predictability of intraoral scanner error for full-arch implant-supported rehabilitation

OBJECTIVES

The present study aimed to analyze the behaviors of three intraoral scanners (IOSs): evaluating the interdistance and axial inclination discrepancies in full-arch scans, predictable errors were searched.

MATERIALS AND METHODS

Six edentulous sample models with variable numbers of dental implants were used; reference data were obtained with a coordinate-measuring machine (CMM). Each IOS (i.e., Primescan, CS3600, and Trios3) performed 10 scans per model (180 total scans). The origin of each scan body was used as a reference point to measure interdistance lengths and axial inclinations. Precision and trueness of interdistance measurements and axial inclinations were evaluated to address error predictability. Bland-Altman analysis, followed by linear regression analysis and Friedman's test (plus Dunn's post hoc correction), was performed to evaluate the precision and trueness.

RESULTS

Regarding interdistance, Primescan showed the best precision (mean ± SD: 0.047 ± 0.020 mm), while Trios3 underestimated the reference value more than the others (p < 0.001) and had the worst performance (mean ± SD: -0.079 ± 0.048 mm). Concerning the inclination angle, Primescan and Trios3 tended to overestimate angle values, while CS3600 underestimated them. Primescan had fewer inclination angle outliers, but it tended to add 0.4-0.6° to the measurements.

CONCLUSIONS

IOSs showed predictable errors: they tended to overestimate or underestimate linear measurements and axial inclinations of scan bodies, one added 0.4-0.6° to the angle inclination values. In particular, they showed heteroscedasticity, a behavior probably related to the software or the device itself.

CLINICAL SIGNIFICANCE

IOSs showed predictable errors that could affect clinical success. When performing a scan or choosing a scanner, clinicians should clearly know their behaviors.

Digital verification and correction of digital intraoral scans for fixed implant rehabilitation of edentulous arches: A dental technique

A method is described for the verification and correction of a digital scan of a complete arch implant-supported prosthesis for a completely edentulous patient. The technique provides an efficient way to integrate a highly accurate and precise scan of an implant index cast with a digital intraoral implant scan by using a computer-aided design and computer-aided manufacturing (CAD-CAM) software program. This method allows dental professionals to validate and, if necessary, correct the implant positions in the scan without the need for a conventional impression.

Accuracy of four recent intraoral scanners with respect to two different ceramic surfaces

OBJECTIVES

To investigate the complete arch accuracy of intraoral scanners (IOS) on two different ceramic surfaces.

METHODS

Two maxillary master cast samples were prepared. The bases of both the master casts were made from zirconium oxide. The difference between the two casts was that the teeth of the [ZR] cast were produced from zirconium oxide and that of the [LD] cast were made of lithium disilicate glass-ceramic. Unlike the zirconia teeth of the [ZR] cast, the lithium disilicate teeth of the [LD] cast were glazed. The two master casts were digitized using a high-resolution scanner (Atos Compact Scan 5 M, GOM GmbH, Braunschweig, Germany) to obtain digital reference casts. Subsequently, each master cast was scanned 15 times using four IOSs. The IOSs were the Cerec Omnicam [OM], Primescan [PR], Trios 4 [TR4], and VivaScan [VS]. On surface comparison, the absolute mean deviation values were obtained for trueness and precision. For multiple comparisons, statistically significant differences were analyzed using one-way ANOVA and the Kruskal-Wallis H test. The p-value was adjusted to control for the increased risk of type I error (p < 0.0083). To compare the two means, the t-test and Mann-Whitney U test were used (p < 0.05).

RESULTS

Trueness values for [ZR] ranged from 24.6 (±6.3) µm for [PR] and 77.1 (±8.3) µm for [OM]. Trueness values for [LD] were between 28.3 (±6.3) µm for [PR] and 72.8 (±15.6) µm for [OM]. Precision values for [ZR] ranged from 17.6 (±3.7) µm for [PR] to 37.3 (±9.9) µm for [OM]. Precision values for [LD] ranged from 17.5 (±3.6) µm for [PR] to 41.8 (±8.7) µm for [OM]. Statistically significant differences were found among all the IOSs (p < 0.0083). The trueness values of the four IOSs did not differ significantly (p < 0.05) with respect to either the [ZR] or [LD] cast. The precision values of [OM] and [VS] differed significantly with respect to the scanned surface.

CONCLUSIONS

Complete arch scans achieved with the four IOSs showed significantly different trueness and precision results. [VS] and [OM] were more sensitive in terms of the scanned material.

CLINICAL SIGNIFICANCE

The latest IOSs showed the required accuracy for complete arch digital impressions in-vitro investigations. These findings should be implemented under conditions relevant to complete arch deviations, such as the construction of occlusal splints, analysis of occlusal relationships, and long-span restorations. Clinicians should be aware that the clinically acceptable threshold varies depending on the purpose of the IOS.

Additive manufacturing technologies in the oral implant clinic: A review of current applications and progress

Additive manufacturing (AM) technologies can enable the direct fabrication of customized physical objects with complex shapes, based on computer-aided design models. This technology is changing the digital manufacturing industry and has become a subject of considerable interest in digital implant dentistry. Personalized dentistry implant treatments for individual patients can be achieved through Additive manufacturing. Herein, we review the applications of Additive manufacturing technologies in oral implantology, including implant surgery, and implant and restoration products, such as surgical guides for implantation, custom titanium meshes for bone augmentation, personalized or non-personalized dental implants, custom trays, implant casts, and implant-support frameworks, among others. In addition, this review also focuses on Additive manufacturing technologies commonly used in oral implantology. Stereolithography, digital light processing, and fused deposition modeling are often used to construct surgical guides and implant casts, whereas direct metal laser sintering, selective laser melting, and electron beam melting can be applied to fabricate dental implants, personalized titanium meshes, and denture frameworks. Moreover, it is sometimes required to combine Additive manufacturing technology with milling and other cutting and finishing techniques to ensure that the product is suitable for its final application.

Complete Digital Workflow for Prosthesis Prototype Fabrication with Double Digital Scanning: Accuracy of Fit Assessment

PURPOSE

To assess the accuracy of a complete digital workflow protocol for fabrication of printed prosthesis prototypes for maxillary immediate loading treatment.

MATERIALS AND METHODS

A maxillary stone cast with 4 abutment-level implant analogs with adequate antero-posterior spread was fabricated. This stone cast served as a reference cast and a zirconia prosthesis was also fabricated to serve as an interim prosthesis. Double digital scanning was used for digital scans of the reference cast and the interim prosthesis, respectively. An intraoral scanner (TRIOS^® 3) was used to capture the standard tessellation language (STL) files. These STL files were then imported to computer-aided design (CAD) software (Exocad DentalCAD) and superimposed into a final design STL file that was exported to 3 different (Form 3b+, Carbon M2, Sprintray Pro95) three-dimensional (3D) printers to produce a total of 90 printed prototypes (n = 30 from each 3D printer). Two blinded clinicians assessed the accuracy of fit of each digitally fabricated prosthesis prototype on the reference cast, utilizing the screw-resistance test and radiographs. The Fisher's exact test was used to test the difference between the groups.

RESULTS

Out of the 90 digitally fabricated prototypes, 86 (95.6%) presented with accurate fit. The accuracy of fit ranged from 87% (26/30) for Sprintray Pro95 to 100% (30/30) for the Form 3b+ and M2 Carbon groups.

CONCLUSIONS

Digitally fabricated prosthesis prototypes can be generated with a complete digital workflow leading to clinically acceptable fit, while reducing the number of appointments and treatment time. The 3D printer had an effect on the accuracy of prosthesis prototype fit.

Evaluation of the accuracy of dental casts manufactured with 3D printing technique in the All-on-4 treatment concept

PURPOSE

The aim of this study is to compare the casts obtained by using conventional techniques and liquid crystal display (LCD) three-dimensional (3D) print techniques in the All-on-4 treatment concept of the edentulous mandibular jaw.

MATERIALS AND METHODS

In this study, a completely edentulous mandibular acrylic cast (typodont) with bone-level implants placed with the All-on-4 technique served as a reference cast. In this typodont, impressions were taken with the conventional technique and dental stone casts were obtained. In addition, after scanning the acrylic cast in a dental laboratory scanner and obtaining the Standard Tessellation Language (STL) data, 3D printed casts were manufactured with a 3D printing device based on the design. The stone and 3D printed casts were scanned in the laboratory scanner and STL data were obtained, and then the interimplant distances were measured using Geomagic Control X v2020 (3D Systems, Rock Hill, SC, USA) analysis software (n = 60). The obtained data were statistically evaluated with one-way analysis of variance (ANOVA) and Tukey's pairwise comparison tests.

RESULTS

As a result of the one-way ANOVA test, it was determined that the stone casts, 3D printed casts, and reference cast values in all distance intervals conformed to the normal distribution and these values had a significant difference among them in all distance intervals. In Tukey pairwise comparison test, significant differences were found between casts at all distance intervals. In all analyses, the level of significance was determined as .05.

CONCLUSION

3D printed casts obtained with a 3D LCD printing device can be an alternative to stone casts when implants are placed in edentulous jaws.

Accuracy of 3D printed models and implant-analog positions according to the implant-analog-holder offset, inner structure, and printing layer thickness: an in-vitro study

PURPOSE

This study aimed to determine how the implant-analog-holder (IAH) offset, inner structure, and printing layer thickness influence the overall accuracy and local implant-analog positional changes of 3D printed dental models.

METHODS

Specimens in 12 experimental groups (8 specimens per group) with different IAH offsets, inner structures, and printing layer thicknesses were printed in three dimensions using an LCD printer (Phrozen Shuffle) and digitized by a laboratory scanner (Identica T500). The trueness and precision of the printed model as well as the angular distortion, depth deviation, and linear distortion of the implant analog were evaluated using three-way ANOVA.

RESULTS

The positional accuracy was significantly higher for IAH offsets of 0.04 mm and 0.06 mm than for one of 0.08 mm, for a hollow than a solid inner structure, and for a printing layer thickness of 100 µm than for one of 50 µm (all P<.001).

CONCLUSIONS

The accuracies of the 3D printed models and the implant-analog positions were significantly affected by the IAH offset, inner structure, and printing layer thickness.

CLINICAL SIGNIFICANCE

Given the observation of this study, premeditating the IAH offset of 0.06 mm, hollow inner structure, and printing layer thickness of 100 µm before printing can help clinicians reach the optimum overall printing accuracy and minimum the local positional changes of the implant-analogs.

A Comparative Analysis of Dental Measurements in Physical and Digital Orthodontic Case Study Models

Background and Objectives: Study models are essential tools used in the dental teaching process. The aim of the present study was to compare the values obtained by manual and digital orthodontic measurements on physical and digital case study models. Materials and Methods: The physical experimental models were obtained by traditional pouring (improved stone-type IV gypsum products) and by additive manufacturing (resins). The digital experimental models were created by scanning the physical ones, using a white light-emitting diode (LED) source and an L-shaped dental scanner—Swing DOF (DOF, Seoul, Korea). The physical study models were first measured using a digital caliper, and then, they were scanned and evaluated using the DentalCad 3.0 Galway software (exocad GmbH, Darmstadt, Germany). The Pont, Linder−Harth, and Bolton indices, which are used in orthodontics for training students, were derived using the available data. Results: When comparing the linear measurement mean ranks taken on physical study models to those of digital models, no statistically significant differences (p > 0.05) were found. A similar result was also shown when the dentoalveolar growth indicators were analyzed. Conclusions: It can be concluded that dental study models made by direct light processing (DLP) and pouring type IV class gypsum are both acceptable for orthodontic teaching purposes.

The cumulative effect of error in the digital workflow for complete-arch implant-supported frameworks: an in vitro study

PURPOSE

To investigate the error accumulation and distribution through various stages of the digital workflow for complete-arch implant-supported framework fabrication.

MATERIALS AND METHODS

A resin model of edentulous maxilla with 6 dental implants was scanned using an intraoral scanner for 10 times (Complete-digital group). Ten conventional gypsum casts were made and digitized by a laboratory scanner (Analogue-digital group). Five implant frameworks were designed and milled using CAD-CAM technique for each workflow. Inter-implant distances and angles of the resin model (reference) and frameworks were measured by a coordinate measuring machine, while the scans and virtual frameworks were examined by an inspection software. Effect of type of workflow and the individual stage on the accuracy of the frameworks were analysed by Two-way ANOVA.

RESULTS

The expanded uncertainty of both workflows was ~150 μm and ~0.8°. The accuracy of the CAD stage was the highest. In the complete-digital workflow, the greatest distortion was found in the data acquisition stage, while in the analogue-digital workflow, it was found in the CAM stage. Compared to the analogue-digital group, the complete-digital group showed a significant higher precision in first-quadrant but lower trueness in second-quadrant in data acquisition, and a significantly lower precision in second-quadrant at the CAD stage.

CONCLUSIONS

Linear distortions of the complete-digital and analogue-digital workflows were clinically acceptable, while angular distortions were not. Distortions were generally derived from data acquisition and CAM stage. The CAD precision depended on the distortions derived from data acquisition. The complete-digital workflow was not as accurate as the analogue-digital in complete-arch implant rehabilitation.

In Vitro Comparison of Three Intraoral Scanners for Implant-Supported Dental Prostheses

With continuing technological developments, there have been advances in the field of fixed prosthetics, particularly in impression-taking techniques. These technological advances mean that a wide variety of diagnostic and/or rehabilitation possibilities can be explored without the need for physical models. The aim of this study was to evaluate the accuracy of three intraoral scanners used in oral implant rehabilitation using an extraoral scanner as a reference and varying the scanning area. Three models representing different clinical scenarios were scanned 15 times by each intraoral scanner and three times by the extraoral scanner. The readings were analyzed and overlaid using engineering software (Geomagic^® Control X software (Artec Europe, Luxembourg)). Statistically significant differences in accuracy were found between the three intraoral scanners, iTero^® (Align Technology Inc., San Jose, CA, USA), Medit^® (Medit^®: Seoul, Korea), and Planmeca^® (Planmeca^®: Helsinki, Finland). In all clinical scenarios, the iTero^® scanner had the best trueness (24.4 μm), followed by the Medit^® (26.4 μm) and Planmeca^® (42.1 μm). The Medit^® showed the best precision (18.00 μm) followed by the iTero^® (19.20 μm) and Planmeca^® (34.30 μm). We concluded that the iTero^® scanner had the highest reproducibility and accuracy in the clinical setting.

Digital VS Conventional Full-Arch Implant Impressions: A Retrospective Analysis of 36 Edentulous Jaws

PURPOSE

There is a paucity of comparative clinical studies assessing the accuracy of full-arch digital versus conventional implant impressions. The aim of this retrospective study was to compare the three-dimensional (3D) deviations between full-arch digital and conventional implant impressions for edentulous maxillae and mandibles.

MATERIALS AND METHODS

Twenty-seven patients (36 edentulous jaws) were treated with one-piece, screw-retained implant-supported fixed complete dental prostheses (IFCDPs). Twenty-one jaws were maxillary, and 15 were mandibular. Full-arch conventional impressions and intraoral digital scans with scan bodies and an intraoral scanner had been taken during the impression phase. Following verification of the conventional stone casts, the casts were digitized. The generated standard tessellation language (STL) files from both impression techniques were merged and analyzed with reverse engineering software. The primary aim was to evaluate the accuracy between conventional and digital full-arch scans, while the effect of the edentulous jaw in 3D accuracy was the secondary aim.

RESULTS

The cumulative 3D (mean ±SD) deviations between virtual casts from intraoral full-arch digital scans and digitized stone casts generated from conventional implant impressions were found to be 88 ±24 μm. In the maxillary group, the mean ±SD 3D deviation was 85 ±25 μm, compared to 92 ±23 μm for the mandibular group (P = .444).

CONCLUSION

The 3D implant deviations found between the full-arch digital and conventional impressions lie within the clinically acceptable threshold. No statistically significant difference was identified between maxillary and mandibular jaws in terms of 3D deviations. This article is protected by copyright. All rights reserved.

Accuracy between intraoral and extraoral scanning: Three-dimensional deviation and effect of distance between implants from two scanning methods

Aim

Evaluate the accuracy between the intraoral and extraoral scanning regarding the three dimensional (3D) deviation and distances between the implants, through 2 scanning methods.

Settings and Design

An in vitro study.

Materials and Methods

An edentulous mandibular model was used to install four implants and abutments, recommending 6 distances between the implants. Scans were performed using an intraoral (SI) and extraoral (SE) scanner for each studied group: Scanning with the scan bodies (SB) and device (SD) (n = 10). The files were imported into a surface evaluation program to assess 3D deviations and measure distances between implants.

Statistical Analysis

Precision was assessed as the difference between files (Kruskal-Wallis test), while trueness was assessed from the difference between scans, applying the Wilcoxon and Mann-Whitney test.

Results

As for the 3D deviations, SI showed accuracy, for the faces and positions of the implants in relation to the SE, in both scanning methods (P < 0.05). Regarding the capture of distances between implants, the SD scan obtained better trueness than the SB group (P < 0.05).

Conclusion

We concluded that the type and scanning methods used did not influence the 3D deviations, while for distances, scanning with the device had better trueness.

Accuracy of commercial 3D printers for the fabrication of surgical guides in dental implantology

OBJECTIVES

To evaluate the accuracy of two different surgical guides (small extent = single implant and large extent = full arch) fabricated by five additive manufacturing technologies (SLA=Stereolithography, DLP= Digital Light Processing, FDM=Fused Deposition Modeling, SLS=Selective Laser Sintering, Inkjet).

METHODS

Overall, 72 guides (6 per type) were obtained with the different machines (SLA=Form2; DLP=Rapid Shape D40 and Cara Print 4.0; FDM=Raise 3D Pro2; SLS=Prodways P1000; Polyjet®=Stratasys J750). The guides were surface-scanned with an optical dental scanner, and the resulting files were compared with the initial design files using a surface matching software. Root Mean Square (RMS) and standard deviation were calculated, representing respectively trueness and precision. Kruskall-Wallis non-parametric test was used to compare trueness and precision between small-extent and large-extent guides and 3D printer by pairs. The threshold for significance was α=0.05, except for the comparison of printers by pairs where a Bonferroni-corrected level of 0.0033 was used.

RESULTS

Significant differences were observed for trueness and precision between small-extent and large-extent guides, regardless the printer except for DLP (trueness and precision) and SLS (precision). SLA, DLP and Polyjet® technologies showed similar results in terms of trueness and precision for both small-extend and large-extend guides (P>0.05).

CONCLUSIONS

The size affected the accuracy of CAD-CAM surgical guides. The different additive manufacturing technologies had a limited impact on the accuracy.

CLINICAL SIGNIFICANCE

This study is of clinical interest as it shows that the 3D printing technology (SLA/DLP) has a limited impact on 3D printed surgical guides accuracy. However, the size of the guide can have a significant impact, as small-extent guides were more accurate than large-extent guides.

A Combined Digital Technique for Manufacturing Functional Fixed Implant Prosthesis Prototypes Using a CAD/CAM Software

The manufacture of complete-arch fixed implant prostheses requires many technical steps to ensure a successful outcome. With the use of monolithic materials such as zirconia, the design of the prosthesis is crucial for a superior result. The aim of this article is to outline a combined technique using a CAD/CAM software for the manufacture of fixed implant prosthesis prototypes for complete-arch implant rehabilitations, which can be done in-house with minimal equipment. This makes it accessible and feasible for those who wish to be involved in the design phase of such prostheses. The method involves collecting several 3D data files including the patient's current prosthesis, the definitive cast, occlusal records and photographs. The technique is described using a patient case that has been provided with digitally designed and in-house manufactured prototypes.

Effect of computer literacy on the working time of the dental CAD software program

PURPOSE

The purpose of this study was to compare the correlation between the learning effect of dental computer-aided design (CAD) software and computer literacy in the clinical and preclinical experience groups of computer-aided design and computer-aided manufacturing (CAD/CAM).

METHODS

A total of 28 participants were recruited, including 14 dental students and 14 dental technicians. Their working time was evaluated using a custom abutment design with two dental CAD software program (exocad GmbH and Deltanine). The working time of custom abutment design was measured 3 times. A survey was conducted to evaluate the computer literacy. For statistical analysis, Mann-Whitney U test was used to analyze the difference between the clinical and preclinical experience groups and the correlation between computer literacy and reduction in working time was confirmed by Spearman's Rank correlation analysis (α=.05).

RESULTS

The median working time showed the clinical experience group had faster than the preclinical experience group (P<.001). On the other hand, the reduction in working time was higher in the preclinical experience group (P=.002). Only preclinical experience group had a significant positive correlation between the computer literacy and reduction in working time (P<.001).

CONCLUSIONS

Basic computer skills are required for first-time users to achie ve an excellent learning effect of dental CAD software program.

The Modern and Digital Transformation of Oral Health Care: A Mini Review

Dentistry is a part of the field of medicine which is advocated in this digital revolution. The increasing trend in dentistry digitalization has led to the advancement in computer-derived data processing and manufacturing. This progress has been exponentially supported by the Internet of medical things (IoMT), big data and analytical algorithm, internet and communication technologies (ICT) including digital social media, augmented and virtual reality (AR and VR), and artificial intelligence (AI). The interplay between these sophisticated digital aspects has dramatically changed the healthcare and biomedical sectors, especially for dentistry. This myriad of applications of technologies will not only be able to streamline oral health care, facilitate workflow, increase oral health at a fraction of the current conventional cost, relieve dentist and dental auxiliary staff from routine and laborious tasks, but also ignite participatory in personalized oral health care. This narrative article review highlights recent dentistry digitalization encompassing technological advancement, limitations, challenges, and conceptual theoretical modern approaches in oral health prevention and care, particularly in ensuring the quality, efficiency, and strategic dental care in the modern era of dentistry.

Accuracy of 3D Printed Implant Casts Versus Stone Casts: A Comparative Study in the Anterior Maxilla

PURPOSE

To conduct an in vitro comparison of the amount of three-dimensional (3D) deviation of 3D printed casts generated from digital implant impressions with an intraoral scanner (IOS) to stone casts made of conventional impressions.

MATERIAL AND METHODS

A maxillary master cast with partially edentulous anterior area was fabricated with two internal connection implants (Regular CrossFit, Straumann). Stone casts (n = 10) that served as a control were fabricated with the splinted open-tray impression technique. Twenty digital impressions were made using a white light IOS (TRIOS, 3shape) and the Standard Tesselation Language (STL) files obtained were saved. Based on the STL files, a digital light processing (DLP) and a stereolithographic (SLA) 3D printer (Varseo S and Form 2) were used to print casts (n = 10 from each 3D printer). The master cast and all casts generated from each group were digitized using the same IOS. The STL files obtained were superimposed on the master cast STL file (reference) to evaluate the amount of 3D deviation with inspection software using the root mean square value (RMS). The independent-samples Kruskal-Wallis test and Dunn's test with Bonferroni correction (for post hoc comparisons) were used for statistical analyses.

RESULTS

The Varseo S group had the lowest median RMS value [77.5 µm (IQR = 91.4-135.4)], followed closely by the Conventional group [77.7 µm (IQR = 61.5-93.4)]. The Form 2 had the highest mean value [98.8 µm (IQR = 57.6-87.9)]. The independent-samples Kruskal-Wallis test revealed a significant difference between the groups (p = 0.018). Post hoc testing revealed a significant difference between Varseo S and Form 2 (p = 0.009).

CONCLUSION

The casts generated from the Varseo S 3D printer had better 3D accuracy than did those from the Form 2 3D printer. Both the Varseo S group and the conventional stone casts groups had similar 3D accuracy.

The direct digital workflow in fixed implant prosthodontics: a narrative review

BACKGROUND

The purpose of this narrative review was to examine the applicability of IOS procedures regarding single and multiple fixed implant restorations. Clinical outcomes for monolithic zirconia and lithium disilicate restorations produced through a direct digital workflow were reported.

METHODS

A MEDLINE (Pubmed) search of the relevant English-language literature spanning from January 1st 2015 until March 31st 2020 was conducted. In vitro studies comparing digital implant impression accuracy by different IOS devices or in vitro studies examining differences in accuracy between digital and conventional impression procedures were included. Also, RCTs, clinical trials and case series on the success and/or survival of monolithic zirconia and lithium disilicate restorations on implants, manufactured completely digitally were included. In vitro and in vivo studies reporting on restorations produced through an indirect digital workflow, case reports and non-English language articles were excluded. The aim was to investigate the accuracy of IOS for single and multiple fixed implant restorations compared to the conventional impression methods and report on the variables that influence it. Finally, this study aimed to report on the survival and success of fixed implant-retained restorations fabricated using the direct digital workflow.

RESULTS

For the single and short-span implant sites, IOS accuracy was high and the deviations in the position of the virtual implant fell within the acceptable clinical limits. In the complete edentulous arch with multiple implants, no consensus regarding the superiority of the conventional, splinted, custom tray impression procedure compared to the IOS impression was identified. Moreover, complete-arch IOS impressions were more accurate than conventional, non-splinted, open or close tray impressions. Factors related to scanbody design as well as scanner generation, scanning range and interimplant distance were found to influence complete-arch scanning accuracy. Single implant-retained monolithic restorations exhibited high success and survival rates and minor complications for short to medium follow-up periods.

CONCLUSIONS

The vast majority of identified studies were in vitro and this limited their clinical significance. Nevertheless, intraoral scanning exhibited high accuracy both for single and multiple implant restorations. Available literature on single-implant monolithic restorations manufactured through a complete digital workflow shows promising results for a follow-up of 3-5 years.

Accuracy of 3-Dimensionally Printed Full-Arch Dental Models: A Systematic Review

The use of additive manufacturing in dentistry has exponentially increased with dental model construction being the most common use of the technology. Henceforth, identifying the accuracy of additively manufactured dental models is critical. The objective of this study was to systematically review the literature and evaluate the accuracy of full-arch dental models manufactured using different 3D printing technologies. Seven databases were searched, and 2209 articles initially identified of which twenty-eight studies fulfilling the inclusion criteria were analysed. A meta-analysis was not possible due to unclear reporting and heterogeneity of studies. Stereolithography (SLA) was the most investigated technology, followed by digital light processing (DLP). Accuracy of 3D printed models varied widely between <100 to >500 μm with the majority of models deemed of clinically acceptable accuracy. The smallest (3.3 μm) and largest (579 μm) mean errors were produced by SLA printers. For DLP, majority of investigated printers (n = 6/8) produced models with <100 μm accuracy. Manufacturing parameters, including layer thickness, base design, postprocessing and storage, significantly influenced the model’s accuracy. Majority of studies supported the use of 3D printed dental models. Nonetheless, models deemed clinically acceptable for orthodontic purposes may not necessarily be acceptable for the prosthodontic workflow or applications requiring high accuracy.

Feasibility of Using a Prosthetic-Based Impression Template to Improve the Trueness and Precision of a Complete Arch Digital Impression on Four and Six Implants: An In Vitro Study

Background: Intraoral scanners (IOSs) in implantology represent a viable approach for single teeth or partial arches. However, when used for complete edentulous arches or long-span edentulous areas, it has been demonstrated that there is a need for improvement of IOS-related techniques. Therefore, the aim of this in vitro study was to assess the trueness and precision of a complete arch digital impression on four and six implants taken with or without a customized, prosthetic-based impression template. Materials and Methods: Two experimental models were prepared, representative of a complete edentulous mandible restored with four and six implants with built-in scan abutments. Models were scanned with (test group, TG) or without (control group, CG) the prosthetic-based impression template. Eight scans were taken for each model. The time needed to take impressions, error, trueness, and precision were evaluated. A statistical analysis was performed. Results: In the case of four implants, the time needed for the impression was 128.7 ± 55.3 s in the TG and 81.0 ± 23.5 s in the CG (p = 0.0416). With six scan abutments, the time was 197.5 ± 26.8 and 110.6 ± 25.2 s in the TG and CG, respectively (p = 0.0000). In the TG, no errors were experienced, while in the CG, 13 impressions were retaken due to incorrect stitching processes. In the four-implant impression, the mean angle deviation was 0.252 ± 0.068° (95% CI 0.021–0.115°) in the CG and 0.134 ± 0.053° (95% CI 0.016–0.090°) in the TG. The difference was statistically significant (p = 0.002). In the six-implant impression, the mean angle deviation was 0.373 ± 0.117° (95% CI 0.036–0.198°) in the CG and 0.100 ± 0.029° (95% CI 0.009–0.049°) in the TG (p = 0.000). In the TG, there were no statistically significant differences in the mean angle deviation within the group (p > 0.05), but there were in the CG. A colorimetric analysis showed higher deviations from the original model for the six-implant impression without a prosthetic template. Conclusions: Although all of the impressions exhibited deviation from the original model in the range of clinical acceptability, the prosthetic-based impression template significantly improved the trueness and precision of complete edentulous arches rehabilitated with four or six implants, making the complete arch digital impression more predictable.