Intraoral scanner-based monitoring of tooth wear in young adults: 24-month results

OBJECTIVES

Tooth wear causes irreversible cumulated surface loss and already occurs at a young age. Therefore, the objective of this clinical prospective observational study was to monitor the occlusal surface of a mandibular first molar in young adults for a period of 24 months. Furthermore, potential aetiological factors obtained by a questionnaire were considered.

MATERIALS AND METHODS

The study teeth (FDI #36 or #46) of 81 participants (mean age 22.8 ± 2.2 years) were scanned with the intraoral scanner (IOS, Trios 3, 3Shape) at the second follow-up (T2) after an observation period of 24 months. Standard-tessellation-language datasets were superimposed with baseline (T0) and T2 scans in 3D analysis software (GOM Inspect). The maximum vertical substance loss was measured between T0 and T2 at 6/7 areas (4/5 cusps and 2 ridges) of each study tooth and data compared to the already published data of the first follow-up (T1) after 12-month observation period. The morphology of tooth wear was classified into three groups: cupping (C), facet (F) and combined cupping-facet (CF). The analysis of aetiological factors, such as acid impacts, was based on a questionnaire filled out by participants at time points T0, T1 and T2. Non-parametric tests were used for statistical analysis (p < 0.05).

RESULTS

The buccal load-bearing cusps (mesiobuccal: median 15 μm, 95%CI 11/18 μm; mesiolingual 8 μm, 0/11 μm) were most affected by tooth wear. Loss values increased significantly at T2 compared to T1 for all areas, although significantly less than in the first 12 months (T0-T1). Areas that already exhibited F at T0 mostly displayed them also at T2 and only rarely developed further into C or CF. The only association between aetiological factors and loss values could be detected for sex as males had significantly higher loss values than females.

CONCLUSIONS

Progression of tooth wear could be clearly shown with high interindividual variations in loss values among participants. This indicates the need for individual monitoring with IOS.

CLINICAL RELEVANCE

IOSs show the potential for patient-specific monitoring to detect the progression of tooth wear. Thus, data of 24 months fills the gap of tooth wear data for young adults in literature. Further studies over a longer observation period are highly recommended to gain more information about the dynamic of tooth wear and aetiological factors.

Accuracy of the Intraoral Scanner for Detection of Tooth Wear

OBJECTIVE

The aim of this work was to study the accuracy of the intraoral scanner for detection of tooth wear in natural teeth by using micro-computed tomography (micro-CT) as a gold standard.

MATERIALS AND METHODS

Twenty premolars were prepared, fixed in acrylic blocks, and scanned with an intraoral scanner (iTero Element® 2) and micro-CT for baseline reference images before artificial tooth wear induction. The samples were then scrubbed with abrasive sandpaper 20 times and scanned with the intraoral scanner. They were then superimposed with the reference images utilising the "TimeLapse" feature of the scanner until the abraded area appeared yellow, indicating tooth surface loss in the 50-200 μm range. The same samples were then rescanned by micro-CT to measure the actual tooth surface loss. This procedure was repeated for the subsequent experimental tooth surface loss of 200-400 μm range (orange areas) and 400-750 μm range (red areas). The collected data were analysed for sensitivity, positive predictive value (PPV), and accuracy. Level of statistical significance was set at .05.

RESULTS

In the detection of experimental tooth surface loss, the specificity, PPV, and accuracy of the intraoral scanner were 98%, 98%, and 97%, respectively.

CONCLUSIONS

The iTero® intraoral scanner can be recommended to be a suitable screening tool for tooth wear in routine dental practice.

The threshold of an intra oral scanner to measure lesion depth on natural unpolished teeth

OBJECTIVES

To investigate the threshold and accuracy of intraoral scanning in measuring freeform human enamel surfaces.

METHODS

Software softgauges, ranging between 20 and 160 µm depth, were used to compare four workflow analysis techniques to measure step height on a freeform surface; with or without reference areas and in combination with surface-subtraction to establish which combination produced the most accurate outcome. Having established the optimum combination, 1.5 mm diameter, individual depths ranging from 11 to 81 µm were created separately on 14 unpolished human enamel samples and then scanned with gold standard laboratory optical profilometry (NCLP, TaiCaan Technologies™, XYRIS2000CL, UK) and a clinical intraoral scanner (TrueDefinition™, Midmark Corp., USA). The sequence of surface registration and subtraction determined from the softgauges was used to measure step height on natural human enamel surfaces. Step heights (μm) were compared using two-way ANOVA with post-hoc Bonferroni (p < 0.05) and Bland-Altman analyses.

RESULTS

Software differences were significantly reduced from - 29.7 to - 32.5% without, to - 2.4 to - 3.6% with reference areas (p < 0.0001) and the addition of surface-subtraction after registration reduced this further to 0.0 to - 0.3% (p < 0.0001). The intraoral scanner had a depth discrimination threshold of 73 µm on unpolished natural enamel and significant differences (p < 0.05) were observed compared to NCLP below this level.

SIGNIFICANCE

The workflow of combining surface-registration and subtraction of surface profiles taken from intraoral scans of freeform unpolished enamel enabled confident measurement of step height above 73 µm. The limits of the scanner is related to data capture and these results provide opportunities for clinical measurement.

Monitoring erosive tooth wear with intraoral 3D scanner: A feasibility study

PURPOSE

To evaluate in vitro the potential of an intraoral scanner (IOS) to monitor erosive tooth wear (ETW) using different alignment software with distinct quantitative measurement metrics.

METHODS

15 unpolished bovine crowns were exposed to citric acid (pH ~2.5) at 24-hour intervals up to 168 hours. At baseline and after each acid exposure episode, the teeth were scanned with IOS (3Shape TRIOS 3). Scanned images from each data point were superimposed on baseline image using WearCompare software to obtain volume loss (mm³) and area loss (mm²) and using IOS built-in software (3Shape TRIOS Patient Monitoring) to obtain depth loss (mm). Pearson's test was used to determine the correlation between acid exposure time (h) and each outcome measure (α= 0.05).

RESULTS

As the acid exposure time increased, the lesion parameters (depth, volume, and area) increased. Friedman's test showed that relative to baseline volume loss became significant (P< 0.05) after 72 hours from median 11.48 mm³ (IQI 25% = 8.72 mm³), eroded area became significant (P< 0.05) from median 48.67 mm² (IQI 25% = 44.46 mm², P< 0.05) after 96 hours, and erosion depth became significant (P< 0.05) from median 0.69 mm (IQI 25% = 0.66 mm²) after 144 hours. A strong correlation was observed between depth (mm²) and time (r= 0.9993 P< 0.0001), volume (mm³) and time (r= 0.9968, P< 0.0001), and area (mm²) and time (r= 0.9475, P= 0.0003).

CLINICAL SIGNIFICANCE

Currently, there is no quantitative method for clinical monitoring of erosive tooth wear. The present study demonstrated that the intraoral scanner is a potential clinical tool for detecting and quantitatively monitoring early and advanced erosive tooth wear.

Anterior tooth-use behaviors among early modern humans and Neandertals

Early modern humans (EMH) are often touted as behaviorally advanced to Neandertals, with more sophisticated technologies, expanded resource exploitation, and more complex clothing production. However, recent analyses have indicated that Neandertals were more nuanced in their behavioral adaptations, with the production of the Châtelperronian technocomplex, the processing and cooking of plant foods, and differences in behavioral adaptations according to habitat. This study adds to this debate by addressing the behavioral strategies of EMH (n = 30) within the context of non-dietary anterior tooth-use behaviors to glean possible differences between them and their Neandertal (n = 45) counterparts. High-resolution casts of permanent anterior teeth were used to collect microwear textures of fossil and comparative bioarchaeological samples using a Sensofar white-light confocal profiler with a 100x objective lens. Labial surfaces were scanned, totaling a work envelope of 204 x 276 μm for each individual. The microwear textures were examined for post-mortem damage and uploaded to SSFA software packages for surface characterization. Statistical analyses were performed to examine differences in central tendencies and distributions of anisotropy and textural fill volume variables among the EMH sample itself by habitat, location, and time interval, and between the EMH and Neandertal samples by habitat and location. Descriptive statistics for the EMH sample were compared to seven bioarchaeological samples (n = 156) that utilized different tooth-use behaviors to better elucidate specific activities that may have been performed by EMH. Results show no significant differences between the means within the EMH sample by habitat, location, or time interval. Furthermore, there are no significant differences found here between EMH and Neandertals. Comparisons to the bioarchaeological samples suggest both fossil groups participated in clamping and grasping activities. These results indicate that EMH and Neandertals were similar in their non-dietary anterior tooth-use behaviors and provide additional evidence for overlapping behavioral strategies employed by these two hominins.