Investigation into the validity of WearCompare, a purpose-built software to quantify erosive tooth wear progression

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.

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.

Measurement of volumetric wear of printed polymer resin and milled polymer infused ceramic network definitive restorative materials

STATEMENT OF PROBLEM

Currently there is no regulatory requirement or international standard for the wear resistance of dental materials and therefore no need to test prior to market launch.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the total volumetric wear characteristics of milled polymer infiltrated ceramic network (MPICN) and printed polymer resin (PPR) as substrates opposing five antagonists, human enamel (EN), lithium disilicate (LD), zirconia (ZR), MPICN, and PPR, and to evaluate and compare the volumetric wear of these same materials as antagonists.

MATERIAL AND METHODS

Ten of each antagonist for a total of 50 EN, LD (IPS e.max CAD), ZR (IPS e.max ZirCAD MT), MPICN (Crystal Ultra), and PPR (Crowntec for NextDent) were shaped into spherical heads and were tested against 2 disk-shaped substrates, MPICN (Crystal Ultra) and PPR (Crowntec for NextDent). Specimens were tested in a wear machine with a third-body food substitute and loaded with a force of 20 to 70 N at 1 Hz for 100 000 cycles. The total wear volume was digitally measured by comparing scans before and after cycling. The area of the wear facet of the antagonists was measured in a similar way and used to estimate the total volume loss of the antagonists. Data were analyzed using 2-way and 1-way ANOVA followed by the Tukey multiple comparisons post hoc test (α=.05).

RESULTS

Antagonist type was found to significantly affect the total volume wear of the substrate (P=.022). EN was found to cause significantly more wear in opposing substrates than ZR and PPR. Substrate material did not significantly affect the wear rate of the substrates (P=.345) nor did the interaction between substrate and antagonist type (P=.150). Antagonist wear was significantly affected by antagonist type (P<.001), with ZR showing no visible signs of wear and MPICN showing the most wear overall; substrate type (P=.002), with antagonists opposing MPICN showing more wear than PPR; and their interaction (P=.031).

CONCLUSIONS

Differences in the wear resistance of milled polymer infiltrated ceramic network and printed polymer resin definitive restorative materials were found but varied depending on the opposing material. No material showed superior wear resistance across all tests. Overall, printed polymer resins created less wear in opposing antagonists than milled polymer infiltrated ceramic network materials.

Acidic/abrasive challenges on simulated non-carious cervical lesions development and morphology

OBJECTIVES

This in vitro investigation assessed how frequency of erosive challenges and duration of toothbrushing abrasion influenced non-carious cervical lesions (NCCLs) development and morphology.

DESIGN

Experimental units were prepared using extracted human premolars assigned to four erosive-abrasive frequency protocols (n=16): F0. No acid exposure (negative control), F2.5 K. Acid exposure (1 % citric acid at natural pH) every 2500, F5K. 5000 and F15K. 15000 brushing-strokes. All groups were brushed for 55000 total brushing-strokes. Three-dimension images of the teeth were captured at baseline, after 15000, 35000 and 55000 brushing-strokes, using an intraoral scanner (TRIOS4, 3Shape). WearCompare software (Leeds Digital Dentistry) was used to analyze volumetric tooth loss (mm3) by superimposition followed by subtraction analysis. Lesion angle was measured (ImageJ, NIH) and morphology visually classified. Data were analyzed using ANOVA and Fisher's Exact tests adopting two-sided 5 % significance level.

RESULTS

Tooth loss increased with brushing-strokes overall (p<0.001) and for each erosive-abrasive protocol (p<0.001). Acid exposure significantly increased tooth loss (p<0.001), regardless of brushing interval (p<0.001), however by 35000 strokes no tooth loss difference was observed among acid-exposed groups (p>0.05). Control had significantly sharper mean lesion angle (59°) than all acid-exposed groups (∼145°) (p<0.001), and significantly different lesion shape with 94 % wedge-shaped lesions versus 0 %, respectively (p<0.001). In contrast to the control, acid exposure was associated to more striated lesions.

CONCLUSIONS

Simulated NCCLs developed and progressed differently and more rapidly in the presence of acidic challenges, regardless of their frequency. Exposure to acid impacted the morphology of lesions.

Automated monitoring of tooth wear progression using AI on intraoral scans

OBJECTIVES

This study aimed to develop and evaluate a fully automated method for visualizing and measuring tooth wear progression using pairs of intraoral scans (IOSs) in comparison with a manual protocol.

METHODS

Eight patients with severe tooth wear progression were retrospectively included, with IOSs taken at baseline and 1-year, 3-year, and 5-year follow-ups. For alignment, the automated method segmented the arch into separate teeth in the IOSs. Tooth pair registration selected tooth surfaces that were likely unaffected by tooth wear and performed point set registration on the selected surfaces. Maximum tooth profile losses from baseline to each follow-up were determined based on signed distances using the manual 3D Wear Analysis (3DWA) protocol and the automated method. The automated method was evaluated against the 3DWA protocol by comparing tooth segmentations with the Dice-Sørensen coefficient (DSC) and intersection over union (IoU). The tooth profile loss measurements were compared with regression and Bland-Altman plots. Additionally, the relationship between the time interval and the measurement differences between the two methods was shown.

RESULTS

The automated method completed within two minutes. It was very effective for tooth instance segmentation (826 teeth, DSC = 0.947, IoU = 0.907), and a correlation of 0.932 was observed for agreement on tooth profile loss measurements (516 tooth pairs, mean difference = 0.021mm, 95% confidence interval = [-0.085, 0.138]). The variability in measurement differences increased for larger time intervals.

CONCLUSIONS

The proposed automated method for monitoring tooth wear progression was faster and not clinically significantly different in accuracy compared to a manual protocol for full-arch IOSs.

CLINICAL SIGNIFICANCE

General practitioners and patients can benefit from the visualization of tooth wear, allowing quantifiable and standardized decisions concerning therapy requirements of worn teeth. The proposed method for tooth wear monitoring decreased the time required to less than two minutes compared with the manual approach, which took at least two hours.

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.

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.

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.

Objective assessment of simulated non-carious cervical lesion by tridimensional digital scanning - An in vitro study

OBJECTIVE

Clinical assessment of progression of non-carious cervical lesions (NCCLs) is currently based on subjective methods. We hypothesize that 3D digital intraoral scanners (IOS) can provide quantitative outcomes for objective measuring and monitoring of NCCLs. This in vitro study verified the reliability of IOS to monitor dental structure loss of simulated NCCLs, in comparison to a reference bench-top 3D optical profilometer (BTS).

METHODS

NCCLs of different severity levels (early, moderate, or severe, n = 150) were simulated in a preceding study. Impressions of the lesions were taken and scanned with both BTS (ProScan; Scantron) and IOS (TRIOS4; 3Shape). Generated 3D images were analyzed for volumetric tooth loss (mm3) by superimposition followed by subtraction analysis. ProForm (Scantron) and WearCompare (Leeds Digital Dentistry) software were used in association to BTS and IOS, respectively. Agreement was assessed using intraclass correlation coefficient (ICC, alpha=0.05) and Bland-Altman plots.

RESULTS

ICC (confidence interval at 95 %) between IOS and BTS for all data combined was 0.962 (0.942-0.973), showing excellent reliability. Subset analyses showed that NCCLs with lower volume loss (early- and moderate-stage lesions) resulted in moderate ICCs, whereas severe lesions showed excellent ICC. Bland-Altman plots demonstrated general good agreement, with narrower limits for early stage-lesions.

CONCLUSION

IOS data demonstrated good agreement to BTS, when measuring tooth structure loss in simulated NCCLs, with particularly higher ICC in more severe lesions. Considering the accessibility and ease-of-use, IOS showed to be a good alternative for the objective assessment of NCCLs in vitro.

CLINICAL SIGNIFICANCE

3D intraoral scanners' accessibility and objectivity make them potentially valuable tools for assessing and monitoring NCCLs.

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.

Reliability of digital repeated-scan superimposition and single-scan techniques for wear volume loss assessment on flat surfaces

OBJECTIVES

Evidence on the reliability of digital techniques for wear volume assessment using three-dimensional (3D) scan datasets is scarce. This study evaluated the reliability of a repeated-scan superimposition technique and two single-scan techniques in assessing wear volume loss on flat surfaces of 3D-printed resin specimens.

METHODS

Cuboid-shaped (15×10×10 mm) resin specimens were 3D-printed (n = 14) and scanned before and after 200,000 cycles of masticatory simulation. For the repeated-scan superimposition technique, digital 3D models of specimens before and after masticatory simulation were superimposed, and the volume loss was determined. The first single-scan technique utilized a computer-aided design freeware program, while the second one employed a 3D-metrology software program. In the freeware program, the worn area of 3D objects was edited directly to obtain a flat surface. In the 3D-metrology software program, the worn area was deleted first and then filled to the flat surface. The volume differences before and after editing were calculated in each software program. Agreement between the three measurement techniques was determined through intraclass correlation coefficients (ICCs). One-way analysis of variance was performed to compare the wear volume loss assessed by the three techniques (α = 0.05).

RESULTS

High inter-technique reliability was observed between the three assessment techniques (ICC = 0.998, p < .001). On pair-wise comparisons of two of the three techniques, all pairs showed high consistency (ICC ≥ 0.999, p < .001). No significant difference was found in the wear volume loss assessed using the three techniques (p = .996).

CONCLUSIONS

Digital repeated-scan superimposition and two single-scan techniques demonstrated high reliability in assessing wear volume loss on flat surfaces.

CLINICAL SIGNIFICANCE

The repeated-scan superimposition technique can be effectively utilized to assess wear volume loss of anatomically shaped specimens and flat surfaces. This study indicates that the single-scan techniques may serve as a suitable alternative to the repeated-scan superimposition technique when evaluating wear volume loss of flat surfaces.

Detection of Erosive Changes on Smooth Surfaces with and without Orthodontic Brackets Using an Intraoral Scanner-An In Vitro Study

BACKGROUND

Consumption of acidic beverages favours development of erosions. Modern diagnostic methods are required to detect erosions at an early stage. This study aimed to evaluate the suitability of an intraoral scanner (IOS) for detection of erosive changes on smooth surfaces adjacent to orthodontic brackets.

METHODS

Orthodontic metal brackets were attached to the buccal surfaces of 58 extracted permanent human teeth. Teeth were randomly divided into groups: A = 6% citric acid, B = Coca-Cola, C = Redbull, D = Powerade, E = Control, no acid exposure. Teeth were exposed to acid in three erosion cycles, followed by rinsing and brushing. Scans of teeth were performed at baseline and after each erosion cycle and enamel loss was measured. Quantitative light-induced fluorescence (QLF) measurements were performed as reference standard.

RESULTS

Significant substance loss was measured in all acid groups after the second and third erosion cycle (p < 0.0001). Correlation between scans and QLF were significant (p = 0.001).

CONCLUSIONS

With IOS, it was possible to detect and quantify enamel erosion at smooth surfaces with and without orthodontic brackets after a short exposure time. Considering the limitations of in vitro results, the use of IOS can be a promising digital tool to detect and monitor erosive enamel changes during fixed orthodontic treatment.

Erosion-inhibiting and enamel rehardening effects of different types of saliva

OBJECTIVES

The objective of this study was to assess the effects of in situ saliva compared to in vitro human saliva, with or without mucin, on inhibiting erosion and promoting enamel rehardening.

DESIGN

Bovine enamel blocks were randomly distributed into groups (n = 23): Gsitu (human saliva in situ), Gvitro (collected human saliva) and GvitroM (collected human saliva with mucin). The enamel blocks underwent a 2-hour period for the formation of salivary pellicle, based on the assigned groups. Subsequently, they were subjected to three erosive cycles, each of them consisting of an erosive challenge (immersion in 0.65 % citric acid, pH 3.5, 1 min) and saliva exposure (immersion in situ or in vitro saliva for 2 h). Microhardness measurements were performed at each cycle, after each experimental step (erosive challenge and exposure to saliva).

RESULTS

After the first demineralization, in vitro saliva groups presented greater hardness loss, with no statistical difference between GVitroM and GVitro. After the third erosive demineralization the in situ saliva resulted in less hardness loss compared to the first demineralization. In relation to surface hardness recovery, there was no difference among types of saliva but there was a decrease in hardness as the cycles progressed.

CONCLUSION

Saliva groups had different behaviors between the first and third demineralization, being similar after the third cycle in terms of hardness loss. Regarding hardness recovery, all saliva promoted enamel gain, but there was a gradual decrease with the progression of the cycles.

Diagnostic Applications of Intraoral Scanners: A Systematic Review

In addition to their recognized value for obtaining 3D digital dental models, intraoral scanners (IOSs) have recently been proven to be promising tools for oral health diagnostics. In this work, the most recent literature on IOSs was reviewed with a focus on their applications as detection systems of oral cavity pathologies. Those applications of IOSs falling in the general area of detection systems for oral health diagnostics (e.g., caries, dental wear, periodontal diseases, oral cancer) were included, while excluding those works mainly focused on 3D dental model reconstruction for implantology, orthodontics, or prosthodontics. Three major scientific databases, namely Scopus, PubMed, and Web of Science, were searched and explored by three independent reviewers. The synthesis and analysis of the studies was carried out by considering the type and technical features of the IOS, the study objectives, and the specific diagnostic applications. From the synthesis of the twenty-five included studies, the main diagnostic fields where IOS technology applies were highlighted, ranging from the detection of tooth wear and caries to the diagnosis of plaques, periodontal defects, and other complications. This shows how additional diagnostic information can be obtained by combining the IOS technology with other radiographic techniques. Despite some promising results, the clinical evidence regarding the use of IOSs as oral health probes is still limited, and further efforts are needed to validate the diagnostic potential of IOSs over conventional tools.

Intraoral occlusal adjustment time and volume required for CAD/CAM crowns fabricated with different virtual mounting methods (A randomized crossover trial)

OBJECTIVE

To measure the required clinical time and volume of occlusal adjustment when the maxillary cast is positioned in a virtual articulator using one of three methods: digitization of a facebow-mounted mechanical articulator (group A), virtual Bonwill triangle (group B) or a 3D face scan (group F).

MATERIALS AND METHODS

In this randomized, triple-blind, crossover trial; 11 participants were enrolled. Every participant had one molar indicated for a single crown restoration. Three crowns were designed and milled for every participant molar totaling 33 crowns. Each of the three crowns was fabricated with the participant's casts virtually mounted utilizing a different method. An impression was taken of the crown in place before occlusal adjustment. The occlusal adjustment was then performed and timed with the three crowns in the different groups. After the occlusal adjustment, an impression of the adjusted crown was taken. The pre-adjustment and post-adjustment impressions were digitally superimposed and the volume difference was measured. The Kruskal-Wallis test was used to compare the groups.

RESULTS

Group A showed the shortest mean adjustment time (3:44.59 ± 3:39.07) followed by group F (4:30.09 ± 2:01.50) and group B (4:35.30 ± 2:32.33). The mean adjustment volume for group A was (28 ± 19.1 mm³) followed by group F (30.5 ± 18.8 mm³) and group B (40.6 ± 29.5 mm³). Different virtual mounting methods had no statistically significant effect on adjustment time (P-value = 0.538) or adjustment volume (P-value = 0.490).

CONCLUSIONS

A simplified approach in virtual articulator mounting appears to be justified in the construction of a single full-coverage prosthesis. Added labor, time and cost of more elaborate virtual mounting methods seem to be counterproductive.

A pilot study on the association between soft tissue volumetric changes and non-surgical periodontal treatment in stage III periodontitis patients. A case series study

OBJECTIVES

This study investigates the correlation between soft tissue volumetric changes and clinical periodontal parameters for patients suffering from Stage III periodontitis after non-surgical periodontal treatment (NSPT) via intraoral scanning.

METHODOLOGY

The following study is a case series pilot study involving twenty-eight Stage III Periodontitis patients. All subjects received full-mouth periodontal examination and intra-oral scanning cat baseline and re-evaluation. NSPT with bi-weekly oral hygiene reviews were carried out, and re-evaluation was performed after 10-12 weeks. Baseline scanned data of all subjects would be superimposed with the corresponding scanned data obtained during re-evaluation to ensure the teeth are in the correct alignment. Boolean subtraction would be performed with the 3D scanned data after superimposition and transformation into a 3D solid. The association of baseline clinical parameters and changes after NSPT with soft tissue volumetric changes up to tooth surface level would be evaluated.

RESULTS AND CONCLUSION

Mean volumetric reduction after NSPT was 153.45 mm³ ± 185.30 mm³ and 124.06 mm³± 124.17 mm³ for the maxillary and mandibular arch, respectively. A statistically significant correlation was detected between soft tissue volumetric reduction to baseline and post-treatment clinical periodontal parameters. Posterior teeth were found to have the highest reduction in soft tissue volume. According to this pilot study, baseline clinical periodontal parameters (PPD, CAL, BOP) correlate with the soft tissue volumetric reduction after NSPT. Further studies on a larger scale and utilization of digital means on tooth sites would be necessary to strengthen the proof of concept.

CLINICAL SIGNIFICANCE

Intraoral scanning can be a valid non-invasive method to assess soft tissue volumetric changes after initial periodontal treatment, which are correlated to changes in the baseline clinical periodontal parameters.

Monitoring of erosive tooth wear: what to use and when to use it

Although we are increasingly recognising the need to assess patients for accelerated rates of tooth wear progression, it is often difficult to do so within a feasible diagnostic window. This paper aims to provide evidence-based timelines which a diagnosing clinician can expect to assess tooth wear progression in study models, clinical indices, clinical photographs and visually with intraoral scans. It also discusses new technologies emerging for the quantitative assessment of tooth wear, timelines for diagnosis, and caveats in the 3D scan registration and analysis process.

Quantifying composite restoration removal and cavity re-preparation using novel region-specific volumetric analysis

OBJECTIVES

This in-vitro study investigated the effect of 400-405nm light used during removal of a composite restorations on volume of tooth tissue removed iatrogenically (IATR) and the volume of residual composite.

METHODS

Thirty unrestored premolar teeth obtained via a university tissue bank were evenly allocated to test and control groups; material removal with and without violet light. Three clinicians (blinded to the protocol) prepared class V buccal cavities in the teeth. The teeth were scanned using CEREC Omnicam and reallocated to another clinician prior to restoration and rescanning. The teeth were reallocated, and the restorations were removed prior to rescanning. Volumetric scan data was obtained on: changes in cavity volume; the volume of IATR; the volume of residual composite. Data were analysed using Shapiro-Wilk and Kruskal-Wallis tests to a significance of p<0.05.

RESULTS

Data showed that there is more IATR when the light was used with mean volume CAV2-over cut of (3.4 mm3, SD 4.22) whereas less IATR was seen when the light was not used (1.2 mm3, SD 1.00), (p<0.05). Data also showed that there is no significant difference in the overall volume of resin composite left when the light was used or not (p> 0.05). However when the light was used, less resin composite material was left around the margins of the cavities when compared to the no light group.

SIGNIFICANCE

This novel region-specific cavity analysis method reveals patterns of iatrogenic damage and retained composite which may hold clinical relevance. The use of violet light may result in more complete removal of composite at margins, but also increase IATR. Further research using the novel method is required to ascertain the repeatability and clinical significance of findings.

Effect of masseter muscle activity during wakefulness and sleep on tooth wear

PURPOSE

To investigate the effect of masseter muscle activity during wakefulness and sleep on tooth wear.

METHODS

Sixteen participants with no or mild tooth wear (NMTW group) and sixteen participants with moderate-to-severe tooth wear (MSTW group) were enrolled. The severity of tooth wear was evaluated using the occlusal and incisal indices of the tooth wear index. Surface electromyography was performed to record the electrical activity of the left masseter muscle during wakefulness and sleep. Electromyographic activity was detected using an electromyographic threshold of 5% and 20% of maximal voluntary clenching (MVC). The total duration of electromyographic activity and bruxism episodes were calculated.

RESULTS

The mean ages of the NMTW and MSTW groups were 71.75 ± 7.61 years and 71.69 ± 7.49 years, respectively. The mean cumulative duration of electromyographic activity during wakefulness using a threshold of >5% MVC was 6.44 ± 4.52 min/h and 13.62 ± 10.08 min/h for the NMTW and MSTW groups, respectively (p=0.048). The mean total durations of electromyographic activity during wakefulness and sleep using a threshold of >20% MVC were 1.08 ± 1.70 min/h and 1.05 ± 3.02 min/h, respectively, in the NMTW group and 4.78 ± 6.37 min/h and 1.61 ± 1.79 min/h, respectively, in the MSTW group (p=0.048 and p=0.003, respectively).

CONCLUSION

These results suggest that masseter electromyographic activity during wakefulness and sleep may be related to the severity of tooth wear.

Tooth wear and socioeconomic status in childhood and adulthood: Findings from a systematic review and meta-analysis of observational studies

OBJECTIVES

To evaluate the association and level of evidence between socioeconomic status (SES) and tooth wear (TW) in children, adolescents, and adults.

DATA

Eligibility criteria comprised population-based observational studies assessing the association between SES and TW in permanent dentition of adolescents and adults. Interventional and descriptive studies or those without an internal comparison between exposed and nonexposed groups were excluded. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied where applicable. Risk of bias (RoB) was assessed using the Newcastle-Ottawa scale. Meta-analyses were conducted to estimate the pooled effect measures. Q-statistic, I²statistic, subgroup and sensitivity analyses assessed study heterogeneity.

SOURCES

PubMed/Medline, Embase, Scopus, Web of Science, LILACS, SciELO, Cochrane Library, and Google Scholar databases were searched for articles published in English between 1st January 1980 and 31st March 2021.

RESULTS

Sixty-five studies were included, involving 63,893 participants in over 30 countries. A positive association was found between TW and education (OR=1.25 [0.96; 1.62]), family income (OR=1.18 [0.91; 1.53]), and private school (OR= 1.24 [0.90; 1.72]) among adolescents. Higher educated adults had a lower risk for TW (OR=0.70 [0.52; 0.93]). Most included studies had a moderate RoB. Limitations relating to population representation and assessment methodologies were identified in the included studies.

CONCLUSIONS

SES was associated with TW with its direction depending on the individuals' age. The overall quality of evidence was moderate.

CLINICAL SIGNIFICANC

SES should be included as part of the routine screening and risk assessment for tooth wear.

Longitudinal 3D Study of Anterior Tooth Wear from Adolescence to Adulthood in Modern Humans

Simple Summary

Tooth wear is the loss of tooth substance during everyday functioning by means other than dental caries. It is expected at a certain level in every person, and it increases with age. In the last decades, due to the increased life expectancy and high patient demands, it has become an important problem modern dentistry has to face. However, the average amount of tooth wear among individuals remains controversial. The purpose of this clinical study was to precisely detect the extent of anterior tooth wear over a thirteen-year period, from adolescence to adulthood. The present study revealed the very high tooth wear occurrence in the population already at early adulthood and showed that wear monitoring at an individual level is important for dentists to enable the better understanding of the problem and allow timely targeted interventions for patients in need. These might be preventive, such as the prescription of mouth guards to limit grinding and the cessation of harmful habits that lead to tooth wear, or interceptive, such as the restoration of the lost tooth substance to stop the progress of the condition and improve esthetics and function.

Abstract

In modern humans, tooth wear can easily be observed as a loss of tooth substance, but its precise measurement is problematic. The aim of this longitudinal cohort study was to determine the precise amount of occlusal tooth wear in the anterior permanent dentition from adolescence to adulthood. Corresponding tooth crowns from serial 3D digital dental models of 72 individuals were best fit-approximated by applying novel, highly accurate 3D superimposition methods. The superimposed crowns were simultaneously sliced on intact structures, and the differences in the volumes of the subsequent occlusal parts were calculated. Over a thirteen-year period, there was an average loss of anterior occlusal surfaces of 1.58 mm³ per tooth. Tooth surface loss in at least one tooth was higher than 1 mm³ in 93.1% of the human subjects. Tooth wear severity differed by sex and tooth type, with males showing higher values versus females and upper canines versus other anterior teeth. The study revealed the endemic occurrence of occlusal anterior tooth wear, highlighting the need for monitoring of the condition in the population to identify high-risk patients and enable timely interventions. The novel methods applied here on 3D digital models are recommended for this.

Progress and limitations of current surface registration methods when measuring natural enamel wear

OBJECTIVES

Our ability to detect dental wear on sequential scans is improving. This experiment aimed to determine if widely used surface registration methods were sufficiently accurate to distinguish differences between intervention groups on early wear lesions.

METHODS

Baseline measurements were taken on human molar buccal enamel samples (n = 96) with a confocal scanning profilometer (Taicaan, UK). Samples were randomly assigned to subgroups of brushing (30 linear strokes 300 g force) before or after an acid challenge (10 min citric acid 0.3% immersion) for four test dentifrices (medium abrasivity NaF, medium abrasivity SnF₂, low abrasivity NaF and a water control). Post-experimental profilometry was repeated. 3D step height was analysed using WearCompare (www.leedsdigitaldentistry.co.uk/wearcompare, UK). Percentage Sa change was calculated using Boddies (Taicaan Technologies, Southampton, UK). Data were analysed in SPSS (IBM, USA).

RESULTS

The mean 3D step height (SD) observed when samples were brushed before the erosive challenge was -2.33 µm (3.46) and after was -3.5 µm (5.6). No significant differences were observed between timing of toothbrushing or dentifrice used. The mean % Sa change for the low abrasivity group (water control and low abrasivity NaF) was -10.7% (16.8%) and +28.0% (42.0%) for the medium abrasivity group (medium abrasivity NaF and SnF₂).

CONCLUSIONS

Detectable wear scars were observed at early stages of wear progression. However standard deviations were high and the experiment was underpowered to detect significant changes. Brushing with a low abrasivity dentifrice or water control produced a smoother surface whereas brushing with a high abrasivity dentifrice produced a rougher surface.

CLINICAL SIGNIFICANCE

The methodology currently used to align sequential scans of teeth and measure change is too imprecise to measure early wear on natural enamel surfaces unless a large sample size is used. Further improvements are required before we can fully assess early wear processes on natural teeth using profilometry.

3D Occlusal Tooth Wear Assessment in Presence of Limited Changes in Non-Occlusal Surfaces

The study aimed to develop an accurate and convenient 3D occlusal tooth wear assessment technique, applicable when surfaces other than the occlusal undergo changes during the observation period. Various degrees of occlusal tooth wear were simulated in vitro on 18 molar and 18 premolar plaster teeth. Additionally, their buccal and lingual surfaces were gently grinded to induce superficial changes and digital dental models were generated. The grinded and the original tooth crowns were superimposed using six different 3D techniques (two reference areas with varying settings; gold standard: GS). Superimposition on intact structures provided the GS measurements. Tooth wear volume comprised the primary outcome measure. All techniques differed significantly to each other in their accuracy (p < 0.001). The technique of choice (CCD: complete crown with 30% estimated overlap of meshes) showed excellent agreement with the GS technique (median difference: 0.045, max: 0.219 mm³), no systematic error and sufficient reproducibility (max difference < 0.040 mm³). Tooth type, tooth alignment in the dental arches, and amount of tooth wear did not significantly affect the results of the CCD technique (p > 0.01). The suggested occlusal tooth wear assessment technique is straightforward and offers accurate outcomes when limited morphological changes occur on surfaces other than the occlusal.

Monitoring of Erosive Tooth Wear with Intraoral Scanners In vitro

Intraoral scanners (IOS) have been used to quantify tooth wear, but so far they have not been systematically validated for monitoring of tissue loss. The aim of this in vitro study was to investigate whether progression of tissue loss can be detected with an IOS and whether IOS values agree with those obtained with noncontacting profilometry (PRO) serving as a standard method. Model jaws were mounted in a phantom head positioned in a dental chair. Flattened areas were prepared on the non-load-bearing cusps of the first molars (model teeth; n = 16) in order to fix flat enamel samples with an experimental area and a reference area. After baseline PRO and IOS, the experimental enamel area was stepwise etched with 35% H3PO4 gel (4 × 30 s and 4 × 15 s). After each etching, PRO and IOS was performed and the vertical tissue loss between the reference and experimental areas was measured, each at the same 3 measurement points. Furthermore, cupped cusps were simulated by stepwise preparation of the load-bearing cusps of the model teeth with a spherical diamond bur, and the maximum vertical depth after each preparation step was measured only by IOS. Trios3 (3Shape, Denmark), Carestream CS3600 (Carestream, USA) and an optical profilometer (MicroProf, Fries, Germany) were used to measure the flat areas of the enamel samples, whereas only IOS were used to measure curved surfaces on the load-bearing cupped cusps of the model teeth. The IOS data were analyzed with an external software (GOM Inspect, Germany) and with the respective internal IOS software. PRO revealed a mean (±SD) tissue loss of 17.1 ± 4.7 µm after 30-s etching steps and 10.1 ± 5.1 µm after the 15-s etching steps. IOS and software types were able to detect the progression of tissue loss after each etching step (p ≤ 0.001 each); Bland-Altmann plots revealed good agreement with PRO regardless of the order of tissue loss, and no systematic difference was found. Increasing cupped lesion depths were detected by all IOS, with no significant differences between IOS and analysis methods. IOS were able to detect small amounts of tissue loss under simulated clinical conditions and seem to be a promising tool for monitoring even initial erosive tooth wear.

Objective assessment of simulated non-carious cervical lesion by tridimensional digital scanning

OBJECTIVE

To explore the use of 3D intraoral scanner/image analysis for the detection and monitoring of simulated non-carious cervical lesions (NCCLs) in vitro.

MATERIALS AND METHODS

A total of 288 NCCLs of different severities and simulated using a laboratorial model associating toothbrush stiffness (soft, medium, and hard) and toothpaste abrasivity (low, medium, high, and negative control) were analyzed. Dental impressions were taken from specimens before and after 35K and 65K brushing strokes, and then scanned with a CEREC Omnicam scanner. 3D models were analyzed for volumetric tooth loss. 3D optical profilometry was considered as the gold standard. Data were analyzed using ANOVA and Fisher's PLSD tests (alpha = 0.05), and agreement between methods by using intraclass correlation coefficient.

RESULTS

Toothbrushes of hard and mid stiffness caused higher tooth loss than soft when associated with the highest abrasive, at 35K and 65K strokes (p < 0.001). Variation in slurry abrasivity led to differences in tooth loss (with control < low < medium < high, p < 0.0001) after both 35K and 65K strokes, regardless of the type of toothbrush used, except at 35K, wherein control = low (p = 0.55). 35K strokes caused less tooth loss than 65K for all abrasive slurries (p < 0.0001) except controls. The intraclass correlation coefficient for agreement between the test and gold standard methods was 0.85.

CONCLUSIONS

Analysis of 3D images from intraoral scanner could detect and monitor NCCL progression, although this ability was limited on incipient lesions. Overall good agreement was found between the test method and optical profilometry.

CLINICAL RELEVANCE

The suggested method may be applicable to detect and monitor NCCLs clinically.

3D Method for Occlusal Tooth Wear Assessment in Presence of Substantial Changes on Other Tooth Surfaces

Early diagnosis and timely management of tooth or dental material wear is imperative to avoid extensive restorations. Previous studies suggested different methods for tooth wear assessment, but no study has developed a three-dimensional (3D) superimposition technique applicable in cases where tooth surfaces, other than the occlusal, undergo extensive morphological changes. Here, we manually grinded plaster incisors and canines to simulate occlusal tooth wear of varying severity in teeth that received a wire retainer bonded on their lingual surfaces, during the assessment period. The corresponding dental casts were scanned using a surface scanner. The modified tooth crowns were best-fit approximated to the original crowns using seven 3D superimposition techniques (two reference areas with varying settings) and the gold standard technique (GS: intact adjacent teeth and alveolar processes as superimposition reference), which provided the true value. Only a specific technique (complete crown with 20% estimated overlap of meshes), which is applicable in actual clinical data, showed perfect agreement with the GS technique in all cases (median difference: −0.002, max absolute difference: 0.178 mm³). The outcomes of the suggested and the GS technique were highly reproducible (max difference < 0.040 mm³). The presented technique offers low cost, convenient, accurate, and risk-free tooth wear assessment.

Influence of Scanner Precision and Analysis Software in Quantifying Three-Dimensional Intraoral Changes: Two-Factor Factorial Experimental Design

BACKGROUND

Three-dimensional scans are increasingly used to quantify biological topographical changes and clinical health outcomes. Traditionally, the use of 3D scans has been limited to specialized centers owing to the high cost of the scanning equipment and the necessity for complex analysis software. Technological advances have made cheaper, more accessible methods of data capture and analysis available in the field of dentistry, potentially facilitating a primary care system to quantify disease progression. However, this system has yet to be compared with previous high-precision methods in university hospital settings.

OBJECTIVE

The aim of this study was to compare a dental primary care method of data capture (intraoral scanner) with a precision hospital-based method (laser profilometer) in addition to comparing open source and commercial software available for data analysis.

METHODS

Longitudinal dental wear data from 30 patients were analyzed using a two-factor factorial experimental design. Bimaxillary intraoral digital scans (TrueDefinition, 3M, UK) and conventional silicone impressions, poured in type-4 dental stone, were made at both baseline and follow-up appointments (mean 36 months, SD 10.9). Stone models were scanned using precision laser profilometry (Taicaan, Southampton, UK). Three-dimensional changes in both forms of digital scans of the first molars (n=76) were quantitatively analyzed using the engineering software Geomagic Control (3D Systems, Germany) and freeware WearCompare (Leeds Digital Dentistry, UK). Volume change (mm³) was the primary measurement outcome. The maximum point loss (μm) and the average profile loss (μm) were also recorded. Data were paired and skewed, and were therefore compared using Wilcoxon signed-rank tests with Bonferroni correction.

RESULTS

The median (IQR) volume change for Geomagic using profilometry and using the intraoral scan was -0.37 mm³ (-3.75-2.30) and +0.51 mm³ (-2.17-4.26), respectively (P<.001). Using WearCompare, the median (IQR) volume change for profilometry and intraoral scanning was -1.21 mm³ (-3.48-0.56) and -0.39 mm³ (-3.96-2.76), respectively (P=.04). WearCompare detected significantly greater volume loss than Geomagic regardless of scanner type. No differences were observed between groups with respect to the maximum point loss or average profile loss.

CONCLUSIONS

As expected, the method of data capture, software used, and measurement metric all significantly influenced the measurement outcome. However, when appropriate analysis was used, the primary care system was able to quantify the degree of change and can be recommended depending on the accuracy needed to diagnose a condition. Lower-resolution scanners may underestimate complex changes when measuring at the micron level.

Quantifying increased rates of erosive tooth wear progression in the early permanent dentition

OBJECTIVES

To investigate if quantitative analysis of intraoral scans of study models can identify erosive tooth wear progression.

METHODS

Data were collected from a retrospective longitudinal study, using pre-and post-orthodontic treatment casts of 11-13 year olds, recorded at two consecutive appointments 29 months apart. Casts were digitised with intra-oral scanner TRIOS™ (3Shape, Copenhagen, Denmark) and first molar scan pairs used for analysis. Occlusal surfaces of each molar pair were visually assessed using the BEWE index as having no BEWE progression (n = 42) or BEWE progression (n = 54). Scan pairs were aligned and analysed for volume loss, maximum profile loss and mean profile loss in WearCompare (Leedsdigitaldentistry.com/wearcompare) using previously published protocols. Data were analysed in SPSS and not normal. Mann-Whitney U test with a Bonferroni correction assessed differences between progression groups. Receiver-operating-characteristic (ROC) curves were used to identify the sensitivity and specificity of quantified wear progression rates at determining visual wear progression.

RESULTS

Surfaces with visible progression demonstrated a median volume loss of -2.19 mm³ (IQR-3.65, -0.91) compared to a median volume loss of -0.37 mm³ (IQR -1.02, 0.16) in the no visible progression group (p < 0.001). Mean profile loss was -75.2 μm (IQR-93.9, -61.0) and 63.2 μm (IQR -82.5, -49.7) for the progression and no-progression groups respectively (p = 0.018). Volume loss of -1.22mm³ represented a 79 % sensitivity and 61 % specificity. The estimated area under the curve for volume loss was 0.80 (95 %CI 0.71-0.89, p < 0.001).

CONCLUSIONS

This is the first study to propose rates of high wear progression in adolescents. Limited sensitivity and specificity confirms that quantitative analysis is an adjunct tool to be used alongside history taking and clinical judgement.

CLINICAL SIGNIFICANCE

The rapid advancement of digital technologies may result in improved diagnosis in erosive tooth wear (ETW). Intra-oral scans and registration software are a promising adjunct for monitoring ETW progression in clinical practice.