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.

Precision of In Vivo Quantitative Tooth Wear Measurement using Intra-Oral Scans.

Quantitative wear measurement is of increasing interest for measuring tooth wear progression. However, most research on quantitative wear measurement has focused on simulated wear or scanned gypsum casts. A 3D Wear Analysis (3DWA) protocol has been developed that analyzes tooth wear in vivo through intra-oral scanners available to dental clinicians. This study investigated the precision of the 3DWA protocol for measuring wear through maximum height loss (mm) and volume change (mm3). Observational prospective wear data from 55 patients were analyzed after 0-1-, 0-3-, and 0-5-year intervals to determine rates of wear, and convenience samples were chosen to test the protocol's precision on dentitions scanned twice in one sitting and its intra- and inter-rater precision on scans with 0-3- and 0-5-year intervals. Scans were made using intra-oral scanners (IOS) and superimposed using 3D measurement software. T-tests were performed to determine the structural and random error, and trimmed ranges were calculated to interpret the error. For protocol precision, the mean difference was 0.015 mm (-0.002; 0.032, p = 0.076) for height and -0.111 mm3 (-0.250; 0.023, p = 0.101) for volume. The duplicate measurement error was 0.062 mm for height and 0.268 mm3 for volume. The height measurements were precise enough to measure wear after intervals of 0-3 or 0-5 years; however, volume measurements were susceptible to procedural error and operator sensitivity. The 3DWA protocol is precise enough to adequately measure tooth height loss after intervals of a minimum of 3 years or in patients with severe wear progression, but it is not suited to measuring volumetric changes.

Associated risk factors with quantitative erosive tooth wear progression.

OBJECTIVES: The aim of this study was to determine predictors of erosive tooth wear (ETW) progression, using novel primary-care quantitative analysis techniques. METHODS: In a single-centre, prospective, observational cohort longitudinal study, adolescents, aged 11-18 years, underwent a baseline BEWE examination, validated risk factors questionnaire and baseline intraoral scan (IOS, TRIOS 3.0, 3Shape, Copenhagen, Denmark). One year later a repeat scan was taken. Quantitative analysis of wear progression (volume loss) on first permanent molars and upper central incisors was performed using previously published protocols. Multilevel linear regression was used to investigate the associations between baseline predictors and volume loss per mm2. RESULTS: A total of 295 dental surfaces (131 incisors and 164 molars) in 70 patients were analysed for this study. The mean age of participants at baseline was 15.0 years (SD: 0.79), and the average time between scans was 11.8 months (1.61 SD; range 10-13). The mean volume loss per mm2 of dental surfaces was -0.013 mm3 (SD: 0.009). Greater volume loss was observed amongst adolescents with higher baseline BEWE scores and those whose parents had lower education as well as on molar than incisor surfaces. No associations were found with dietary acid intake and intrinsic acid exposure when baseline levels of tooth wear, parental education and other factors were controlled for. CONCLUSIONS: The findings help to characterise groups at greater risk of ETW and would indicate that improved screening and upstream preventative measures should form the basis of a preventative program. CLINICAL SIGNIFICANCE: Intra-orals scans and registration software might improve the ability to diagnose, monitor and prevent the early loss of dental hard tissue.

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.

Application of the Intraoral Scanner in the Diagnosis of Dental Wear: An In Vivo Study of Tooth Wear Analysis.

In recent years, there has been an increase in the incidence of dental wear; thus, an early diagnosis is important. Conventional methods of diagnosis are based primarily on the visual abilities of the dentist, and therefore the use of new technologies for the detection of dental wear may be very useful. The aim of the study was to analyze the sensitivity and specificity of the intraoral scanner for measuring dental wear, as well as to evaluate patients' satisfaction with the use of the scanner. The study was conducted with 46 volunteers who underwent three intraoral analyses: a first baseline scanning, a second scanning after 6 months and a final scanning after one year performed by four operators divided into two groups. One of the operators performed the visual analysis of dental wear, and the other performed the analysis using the intraoral scanner 3M™ True Definition intraoral scanner (ESPE, Seefeld, Germany). The data obtained from the intraoral scanner showed levels of specificity and sensitivity that enable the intraoral scanner to be used as a diagnostic tool in the assessment of tooth wear. The participants also showed a high degree of satisfaction with the scanner as a communication tool.

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.

Testing the reliability of CT scan-based dental wear magnitude scoring.

OBJECTIVES: Digital models are now frequently used in biological anthropology (bioanthropology) research. Despite several studies validating this type of research, none has examined if the assessment of dental wear magnitude based on Computerized Tomography (CT) scans is reliable. Thus, this study aims to fill this gap and assess if dental wear magnitude scoring based on CT scans provides results consistent with scoring based on direct observation of the physical specimens. MATERIALS AND METHODS: Dental wear magnitude from 412 teeth of 35 mandibles originating from the Portuguese Muge and Sado Mesolithic shell-middens was scored. The mandibles were also CT scanned and visualized using 3D Slicer. CT scan-based scoring of dental wear magnitude was then undertaken. Two scoring rounds were undertaken for each observation method (totaling four scoring rounds) and an intra-observer error test was performed. The averaged results of the two observation methods were compared via boxplots with paired cases. RESULTS: Intra-observer error was negligible and non-significant. Scoring results are comparable between the two observation methods. Notwithstanding, some differences were found, in which CT scan assessment generally overestimates dental wear when compared to direct observation. DISCUSSION: Our results generally validate the use of CT scans in studies of dental wear magnitude. Notwithstanding several caveats relating to CT scanning and visualization limitations should be considered to avoid over or under-estimation of dental wear.

Confirmation of a wear-compensation mechanism in dental roots of ruminants.

Diet affects many factors of an animal's anatomy, but teeth are a specific focus of dietary research, as their durability lends them to record information on a large variety of scales. Abrasive diets like those of grazing herbivores are known to wear down teeth, but how that wear affects tooth growth and the relations between its different morphological components is rarely investigated. Seven pelleted diets varying in abrasive size and concentration were fed over a 17-month period to 49 sheep (Ovis aries), of which n = 39 qualified for morphology measurements. Using computed tomography, scans of the skulls were made over the course of the experiment, and the impact of diet-related wear was observed on tooth volume and morphology, including the position of dental burr marks, over time. Digital caliper measurements were applied to 3D renderings of the teeth, and the volume of crown and root segments were investigated separately. We aimed to detect a signal of root growth compensating for wear, and test if this mechanism would be affected by dietary abrasives. Crown-segment volume loss was correlated to root-segment volume gain. Height and burr mark measurements indicated a much higher experimental tooth wear than that previously reported for free-ranging animals. The reason for this is unclear. There was no relationship between tooth height and dentine basin depth. For all parameters, there was no effect of diet; hence, while the measurements corroborate general understanding of tooth wear and compensatory processes, these methods appear not suitable to assess subtle differences between feeding regimes.

A comparative evaluation between the reliability of gypsum casts and digital greyscale intra-oral scans for the scoring of tooth wear using the Tooth Wear Evaluation System (TWES).

BACKGROUND: The Tooth Wear Evaluation System (TWES) is a type of tooth wear index. To date, there is the lack of data comparing the reliability of the application of this index on gypsum cast records and digital greyscale intra-oral scan records. OBJECTIVES: A comparative evaluation between the use of gypsum cast records and digital greyscale intra-oral scan records with the reliability of tooth wear scoring using the TWES amongst a group of patients with tooth wear. METHODS: Records for 10 patients with moderate to severe tooth wear (TWES ≥ 2) were randomly selected from a larger clinical trial. TWES grading of the occlusal/incisal, buccal and palatal/lingual surfaces was performed to determine the levels of intra- and interobserver agreement. Intra-observer reproducibility was based on the findings of one examiner only. For the interobserver reproducibility, the findings of two examiners were considered. One set of models/ records were used per patient. Cohen's weighted kappa (κW ) was used to ascertain agreement between and within the observers. Comparison of agreement was performed using t tests (P < .05). RESULTS: For the scoring of the of the total occlusal/incisal surfaces, the overall levels of intra- and interobserver agreement were significantly higher using the gypsum cast records than with the digital greyscale intra-oral scan records, (P < .001) and (P < .001), respectively. For the overall buccal surfaces, only a significant difference was found in the intra-observer agreement using gypsum casts, (P = .013). For the palatal/lingual surfaces, a significant difference was only reported in the interobserver agreement using gypsum casts, (P = .043). At the occlusal/incisal surfaces, grading performed using gypsum casts, culminated in significantly higher TWES scores than with the use of the digital greyscale intra-oral scans (P < .001). At the buccal and palatal/lingual surfaces, significantly higher wear scores were obtained using digital greyscale intra-oral scan records (P < .009). CONCLUSIONS: The TWES can offer a reliable means for the scoring of wearing occlusal/incisal surfaces using gypsum casts. The reliability offered by digital greyscale intra-oral scans for consecutive scoring was in general, inferior.

Applying dental microwear texture analysis to the living: Challenges and prospects.

OBJECTIVES: The food that people and animals consume leaves microscopic traces on teeth in predictable ways, and analyses of these markings-known as dental microwear analyses-allow us to reverse engineer the characteristics of diet. However, the microwear features of modern human diets are most often interpreted through the lens of ethnographic records. Given the subtle variation within human diets when compared to other species, we need better models of how foods and processing techniques produce marks on teeth. Here, we report on the second study to target the occlusal surface microwear of living human populations, and the first to target populations other than foragers. METHODS: We collected 150 dental impressions from five Kenyan communities: El Molo, Turkana (Kerio), Luhya (Webuye), Luhya (Port Victoria), and Luo (Port Victoria), representing a range of subsistence strategies and associated staple diets-fishing, pastoralism, and agriculture. Our results suggest that the occlusal microwear of these groups records differences in diet. However, biofilm obscured most of the molds obtained despite the steps taken to remove it, resulting in only 38 usable surfaces. RESULTS: Due to the biofilm problem and final sample size, the analysis did not have enough power to demonstrate the differences observed statistically. The results and problems encountered are here explained. CONCLUSIONS: Considering that in vivo studies of dental microwear texture analysis have the potential to increase our understanding of the association between patterns of dental microwear and complex, mixed human diets, resolution of the current pitfalls of the technique is critical.

Diagnosis of Occlusal Tooth Wear Using 3D Imaging of Optical Coherence Tomography Ex Vivo.

The aim of this study was to assess the utility of 3D imaging of optical coherence tomography (OCT) for the diagnosis of occlusal tooth wear ex vivo. Sixty-three extracted human molars with or without visible tooth wear were collected to take digital intraoral radiography and 3D OCT images. The degree of tooth wear was evaluated by 12 examiners and scored using 4-rank scale: 1-slight enamel wear; 2-distinct enamel wear; 3-tooth wear with slight dentin exposure; 4-tooth wear with distinct involvement of dentin. The degree of tooth wear was validated by the histological view of confocal laser scanning microscopy (CLSM). The sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic analysis were calculated. Diagnostic accuracy was compared with the agreement with CLSM observation using weighted kappa. The results were statistically analyzed at a significance level of α = 0.05. Three-dimensional OCT showed significantly higher sensitivity (p < 0.05) for all the diagnostic thresholds of enamel wear and dentin exposure than digital radiography (0.82, 0.85, and 0.79 vs. 0.56, 0.52, and 0.57, respectively). Three-dimensional OCT showed higher AUC and kappa coefficients than digital radiography (p < 0.05), where mean AUC and Kappa values were 0.95 and 0.76 for OCT and 0.92 and 0.47 for radiography, respectively. No significant difference of specificity was observed (p > 0.05). Three-dimensional OCT could visualize and estimate the degree of tooth wear and detect the dentin exposure at the tooth wear surface accurately and reproducibly. Consequently, a new guideline for tooth wear assessment can be proposed using OCT.

Monitoring of simulated occlusal tooth wear by objective outcome measures.

OBJECTIVES: This in vitro study explored quantitative outcome measures as clinical indicators of simulated occlusal tooth wear progression. METHODS: Ten sound, extracted human premolars were selected and submitted to occlusal tooth wear simulation in 0.5-mm steps (0/0.5/1.0/1.5 mm). At each step, enamel thickness on the buccal cusp tips was evaluated using cross-polarization optical coherence tomography (CP-OCT) and micro-computed tomography (µ-CT). The occlusal surface of each premolar was also scanned at each step using a 3D digital intraoral scanner, followed by morphological characterization using standard topography attributes (Slope, Relief, RFI, OPCr). Repeated measures ANOVA assessed differences in simulated wear levels for the µ-CT and CP-OCT data as well as the topography values. Correlations were also calculated between the µ-CT/CP-OCT and topography data. RESULTS: Significant differences were observed for enamel thickness at each simulation wear stage, for both CP-OCT (p < 0.001) and µ-CT (p < 0.001), with good agreement between methods (intraclass correlation: 0.89). For topography analysis, as wear increased, the average Slope, RFI, and Relief values decreased, and average OPCr values increased, with more significant differences shown for Slope. Slope showed significant (p < 0.05) positive correlations with CP-OCT. OPCr showed significant negative correlations with µ-CT, and CP-OCT (p < 0.05). RFI and Relief were not correlated with either µ-CT or CP-OCT (p > 0.05). CONCLUSIONS: Our findings suggest the potential of PS-OCT for measuring enamel thickness changes in the cusp tips of the occlusal surface. Similarly, conventional intraoral scanners can serve effectively for monitoring overall tooth wear when combined with dental topographic analyses of resultant point clouds. CLINICAL SIGNIFICANCE: CP-OCT measures of enamel thickness and dental 3D topographic attributes showed potential as objective outcomes for the clinical monitoring of occlusal tooth wear. Their combination provided a comprehensive understanding of the tooth wear development process.

Detecting early erosive tooth wear using an intraoral scanner system.

OBJECTIVES: To assess the feasibility of detecting and monitoring early erosive tooth wear using a 3D intraoral scanner (IOS) aided by specific software. METHODS: Extracted sound permanent teeth were assembled in two shortened artificial dental arches and scanned at different intervals with an IOS (3Shape TRIOS® 3) before and after an erosion/abrasion protocol (i.e. 1 h up to 24 h immersion in citric acid solution and subsequent brushing). The 3D models obtained at consecutive time points were superimposed with the baseline model using dedicated software (3Shape TRIOS® Patient Monitoring, version 2.1.1.0) and reference surface alignment. Surface profile differences between the baseline 3D model and the respective models from different time points were expressed as tooth substance loss. Non-parametric tests were used to assess the significance of tooth substance loss at different time points. Spearman's correlation was applied between the tooth substance loss at the end of each erosion/abrasion cycle and the immersion time in acid. RESULTS: Significant tooth substance loss (0.08 mm, IQR = 0.05) was detected by the software after 3 h of erosive-abrasive challenge (p = 0.045). The overall median loss increased gradually from baseline to 24 h showing a strong correlation with the immersion time in acid (rs = 0.971, p < 0.01). CONCLUSIONS: The use of an IOS aided by specific software showed good performance for early detection and monitoring of tooth wear in vitro and has promising potential for in vivo application. CLINICAL SIGNIFICANCE: Detection and monitoring of early erosive tooth wear can be reliably aided by intraoral scanning supported by specific software. The measurement error and uncertainty involved in this method should be taken into consideration when interpreting the tooth substance loss measurements. Furthermore, presuming the difficulty in defining reference surfaces in vivo, clinical validation is needed to determine the system's in vivo performance.

An accurate and efficient method for occlusal tooth wear assessment using 3D digital dental models.

Tooth or material wear in a dentition is a common finding that requires timely diagnosis for management and prevention of further loss or associated esthetic or functional impairment. Various qualitative and quantitative methods have been suggested to measure tooth or material wear, but they present with limitations, such as imprecision, subjectivity, or high complexity. Here we developed and assessed an efficient 3D superimposition method to accurately measure occlusal tooth wear on 3D digital dental models. For this purpose, teeth on plaster casts were manually grinded on their occlusal surfaces to simulate various degrees of tooth wear. The casts were scanned using a surface scanner. Grinded tooth crowns (T1) were segmented and compared to the original crowns (T0) using five 3D surface superimposition techniques and a gold standard technique (GS). GS measurements were obtained by using intact adjacent structures as superimposition references. The technique of choice (complete crown with 30% estimated overlap of meshes) showed the best reproducibility (maximum difference < 0.050 mm3) and excellent agreement with the GS technique (median difference: 0.032 mm3). The suggested 3D superimposition method offers a highly efficient and accurate tool for tooth wear assessment, which could be applicable to clinical conditions.

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.

Cup-Shaped Tooth Wear Defects: More than Erosive Challenges?

BACKGROUND/AIM: The underlying mechanism of the development of cups and grooves on occlusal tooth surfaces is still unclear. The aim of this study was to evaluate factors contributing to in vitro cup formation, in order to elucidate the clinical process. METHODS: A total of 48 extracted human molar teeth were exposed to acidic aqueous solutions at pH of 4.8 and 5.5 in constant motion, in combination with different loading conditions: no load (0N group, control), 30 N (30N group) or 50 N (50N group) (n = 8 per group). Before and after 3 months of exposure (1,422,000 loading cycles), the samples were scanned using a non-contact profilometer. Pre- and post-exposure scans were subtracted and height loss and volume tissue loss were calculated. Representative samples with wear and cupping lesions were imaged using scanning electron microscopy, light microscopy and micro-computed tomography. RESULTS: Average height and volume tissue loss at pH 5.5 was 54 µm and 3.4 mm3 (0N), 52 µm and 3.4 mm3 (30N) and 58 µm and 3.7 mm3 (50N), respectively, with no statistically significant differences. Average height and volume loss at pH 4.8 were 135 µm and 8.7 mm3 (0N), 172 µm and 12.6 mm3 (30N) and 266 µm and 17.8 mm3 (50N), respectively, with a statistically significant difference between 0N and 50N (p < 0.002). Cup-shaped lesions had formed only at pH of 4.8, in the 30N and 50N groups. CONCLUSION: The study showed that a cup can arise fully in enamel and that mechanical loading in addition to erosive challenges are required.

Evaluation of tooth wear by estimating enamel thickness with quantitative light-induced fluorescence technology.

BACKGROUND: Various techniques have been suggested to quantitatively assess tooth wear; most have limited clinical application. The first aim of this in vitro study was to estimate the residual enamel thickness of teeth with various degrees of occlusal wear using quantitative light-induced fluorescence (QLF). The second aim was to identify relationships between the fluorescence parameters of QLF and the conventional tooth wear index (TWI) system. METHODS: Sixty-nine extracted permanent premolars and molars with initial stages of tooth wear (TWI score 1a-2: enamel wear to dentin exposure) were used. Two blinded and trained examiners participated in evaluation procedures. Occlusal QLF-digital (QLF-D) images were acquired for selecting area of interest (AOI) and calculating fluorescence for occlusal tooth wear (ΔFwear) of the AOI by the first examiner. Each specimen was cross-sectioned in the buccal-lingual direction. Enamel thickness from images obtained by stereomicroscopy and TWI of each sample was determined by the second examiner. Spearman correlation was used to determine the relationship of ΔFwear with enamel thickness and TWI. ΔFwear values were compared between histological scores with the Mann-Whitney U test. RESULTS: Seventy-six AOIs were analyzed. As enamel thickness decreased, ΔFwear values significantly increased and strongly correlated with enamel thickness (Spearman rho = -0.825, P < 0.001). There were significant differences in ΔFwear values among TWI scores (P < 0.001); ΔFwear strongly correlated with TWI (Spearman rho = 0.753, P < 0.001). CONCLUSIONS: ΔFwear values, which denote fluorescence difference by using QLF, showed a strong correlation with residual enamel thickness and tooth wear severity.

Controlled feeding experiments with diets of different abrasiveness reveal slow development of mesowear signal in goats (Capra aegagrus hircus).

Dental mesowear is applied as a proxy to determine the general diet of mammalian herbivores based on tooth-cusp shape and occlusal relief. Low, blunt cusps are considered typical of grazers and high, sharp cusps typical of browsers. However, how internal or external abrasives impact mesowear, and the time frame the wear signature takes to develop, still need to be explored. Four different pelleted diets of increasing abrasiveness (lucerne, grass, grass and rice husks, and grass, rice husks and sand) were fed to four groups of a total of 28 adult goats in a controlled feeding experiment over a 6-month period. Tooth morphology was captured by medical CT scans at the beginning and end of the experiment. These scans, as well as the crania obtained post mortem, were scored using the mesowear method. Comparisons between diet groups showed few significant differences after 6 months, irrespective of whether CT scans or the real teeth were scored. Only when assessing the difference in signal between the beginning and the end of the experiment did relevant, significant diet-specific effects emerge. Diets containing lower phytolith content caused a more pronounced change in mesowear towards sharper cusps/higher reliefs, while the feed containing sand did not result in more extreme changes in mesowear when compared with the same feed without sand. Our experiment suggests that the formation of a stable and hence reliable mesowear signal requires more time to develop than 6 months.

The facial effects of tooth wear rehabilitation as measured by 3D stereophotogrammetry.

OBJECTIVE: Evaluate the effect of a full rehabilitation, including an increase of vertical dimension of occlusion (VDO), in patients with severe tooth wear on changes in facial appearance. METHODS: Patients with severe tooth wear were restoratively treated using direct composite restorations, including an increase of the VDO. Before and one month after treatment 3D stereophotographs were taken and facial changes were measured with the use of 3D cephalometric landmarks. Cast models were used to determine the Tooth Wear Index (TWI) and the VDO-increase. The Orofacial Esthetic Scale-questionnaire was used to evaluate subjective happiness with appearance. Paired Student's t-tests were used to evaluate the changes after full rehabilitation. The relation between the facial changes, VDO-increment and TWI-score were analyzed using multiple regression models (p < 0.05). RESULTS: 44 Patients (35 men, 9 women, mean age: 38.2 ±â€¯7.1 y) participated in this study. Mean TWI-score at baseline was 3.3 ±â€¯0.5 and the mean increase in VDO was 1.6 ±â€¯0.9 mm. Lower face height increased by 1.9 mm (p ≤ 0.001). Patients reported a significant improvement in orofacial appearance: OES-summary score of 34.3 ±â€¯11.2 before and 59.9 ±â€¯6.8 one month after treatment (p < 0.001). The increase of VDO resulted in an increase in Lower Face Height (p ≤ 0.002), whereas the TWI-score at baseline had no effect on the facial changes. The applied increase in VDO and TWI-score were not related to changes in OES-scores. CONCLUSIONS: A full rehabilitation with an increase in VDO resulted in objective differences in facial height as measured with 3D stereophotogrammetry. CLINICAL SIGNIFICANCE: In patients with severe tooth wear, receiving a full rehabilitation including an increase in vertical dimension of occlusion, an objectively change will occur in the Lower facial height, but this effect will be subjectively judged as a positive change.