Examination of the Interproximal Wear Mechanism: Facet Morphology and Surface Texture Analysis

Isotopological remeshing and statistical shape analysis: Enhancing premolar tooth wear classification and simulation with machine learning

OBJECTIVE

The aim of this study was to evaluate the accuracy of a combined approach based on an isotopological remeshing and statistical shape analysis (SSA) to capture key anatomical features of altered and intact premolars. Additionally, the study compares the capabilities of four Machine Learning (ML) algorithms in identifying or simulating tooth alterations.

METHODS

113 premolar surfaces from a multicenter database were analyzed. These surfaces were processed using an isotopological remeshing method, followed by a SSA. Mean Euclidean distances between the initial and remeshed STL files were calculated to assess deviation in anatomical landmark positioning. Seven anatomical features were extracted from each tooth, and their correlations with shape modes and morphological characteristics were explored. Four ML algorithms, validated through three-fold cross-validation, were assessed for their ability to classify tooth types and alterations. Additionally, twenty intact teeth were altered and then reconstructed to verify the method's accuracy.

RESULTS

The first five modes encapsulated 76.1% of the total shape variability, with a mean landmark positioning deviation of 10.4 µm (±6.4). Significant correlations were found between shape modes and specific morphological features. The optimal ML algorithms demonstrated high accuracy (>83%) and precision (>86%). Simulations on intact teeth showed discrepancies in anatomical features below 3%.

CONCLUSION

The combination of an isotopological remeshing with SSA showed good reliability in capturing key anatomical features of the tooth.

CLINICAL SIGNIFICANCE

The encouraging performance of ML algorithms suggests a promising direction for supporting practitioners in diagnosing and planning treatments for patients with altered teeth, ultimately improving preventive care.

Effect of herbal irrigants on surface roughness of intraradicular dentin using quantitative method of 3D surface texture analysis

Replacing the conventional endodontic irrigants with herbal agents could avoid complications associated with using sodium hypochlorite (NaOCl). Endodontic irrigants alter the surface roughness of the dentinal wall surface, which affects sealer mechanical retention. This study aimed to assess the effect of experimental herbal Moringa oleifera and orange peel extract irrigant on intraradicular dentin (IRD) surface roughness using quantitative 3D surface analysis by scanning electron microscopy (SEM) regarding the smear layer assessment. Sixty human root sections were divided into four groups (n = 15): NaOCl combined with 17% ethylenediaminetetraacetic acid (EDTA); negative control (saline); moringa extract (MO); and orange oil (OO). SEM images were assessed quantitatively for surface roughness (Ra) in the coronal, middle, and apical IRD. The data were analysed by Kruskal-Wallis, Friedman, and Dunn's tests. All groups showed statistically significant differences (P = 0.007). MO exhibited significantly greater Ra values at the coronal, middle, and apical root levels than OO (P = 0.007, 0.009, and 0.046, respectively). There was no significant change in Ra values at various root levels within each group at P = 0.091, 0.819, 0.819, and 0.549 for the EDTA, saline, MO, and OO groups. Considerable (IRD) surface roughness analysis makes Moringa extract a promising herbal endodontic irrigant alternative to the NaOCl plus EDTA regimen.

Finite element analysis of Neanderthal and early Homo sapiens maxillary central incisor

Neanderthal anterior teeth are very large and have a distinctive morphology characterized by robust 'shovel-shaped' crowns. These features are frequently seen as adaptive responses in dissipating heavy mechanical loads resulting from masticatory and non-masticatory activities. Although the long-standing debate surrounding this hypothesis has played a central role in paleoanthropology, is still unclear if Neanderthal anterior teeth can resist high mechanical loads or not. A novel way to answer this question is to use a multidisciplinary approach that considers together tooth architecture, dental wear and jaw movements. The aim of this study is to functionally reposition the teeth of Le Moustier 1 (a Neanderthal adolescent) and Qafzeh 9 (an early Homo sapiens adolescent) derived from wear facet mapping, occlusal fingerprint analysis and physical dental restoration methods. The restored dental arches are then used to perform finite element analysis on the left central maxillary incisor during edge-to-edge occlusion. The results show stress distribution differences between Le Moustier 1 and Qafzeh 9, with the former displaying higher tensile stress in enamel around the lingual fossa but lower concentration of stress in the lingual aspect of the root surface. These results seem to suggest that the presence of labial convexity, lingual tubercle and of a large root surface in Le Moustier 1 incisor helps in dissipating mechanical stress. The absence of these dental features in Qafzeh 9 is compensated by the presence of a thicker enamel, which helps in reducing the stress in the tooth crown.

In vitro study on the preventive effect of children's toothpastes on erosive tooth wear of primary bovine enamel and dentin

This in vitro study aimed to analyse the effect of various children's toothpastes on erosive tooth wear of primary bovine enamel and dentin. Enamel and dentin specimens (n = 12) were cyclically eroded (6 × 60 s/d, citric acid, pH 2.4) and brushed (2 × 15 s/d, 2 N) over 5 days. Nine fluoride toothpastes (500 to 1450 ppm) and eight toothpastes containing no fluoride or other active ingredients (hydroxyapatite and/or xylitol) were tested. Unbrushed specimens served as control. Tissue loss was quantified using widefield confocal microscopy and statistically analysed using two-way and one-way ANOVAs followed by Scheffe's (enamel) or Tamhane's (dentin) post-hoc tests (p < 0.05). Only one fluoride toothpaste (1400 ppm) was able to reduce erosive wear of enamel significantly by 15% compared to the control (p_adj. = 0.002). All fluoridated toothpastes reduced dentin surface loss significantly by 32 to 69% compared to the control (p_adj. ≤ 0.001), while fluoride-free toothpastes were unable to reduce dentin loss significantly (p_adj. ≥ 0.971). Most fluoridated toothpastes caused less erosive wear compared to fluoride-free toothpastes. Children toothpastes containing fluoride were more effective in reducing erosive wear compared to toothpastes containing no fluoride or other active ingredients.

Effects of long-term cinnamaldehyde immersion on the surface roughness and color of heat-polymerized denture base resin

STATEMENT OF PROBLEM

Cinnamaldehyde has been successfully used for the short-term disinfection of dentures; however, its long-term effects on the surface and color properties of denture base materials remain unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of simulated immersion in cinnamaldehyde for up to 5 years on the surface roughness and color parameters of a heat-polymerized denture resin.

MATERIAL AND METHODS

Eighty Ø10×5-mm disk-shaped specimens were prepared from microwave heat-polymerized polymethylmethacrylate (PMMA) and immersed in 4 solutions (n=20): TW-tap water (control), SH - 0.5% sodium hypochlorite, PX-alkaline peroxide, and CA-cinnamaldehyde (27 μg/mL). The immersion protocol simulated 104 cycles (3.5 months), 913 cycles (2.5 years), and 1825 immersion cycles (5 years) of a daily immersion cleaning protocol, with immersion times ranging from 10 to 20-minutes. Surface roughness (Sa) and the color parameters of CIELab (L∗ a∗ b∗, ΔEab), CIEDE2000 (ΔE00), and the National Bureau of Standards (NBS) were analyzed at baseline (t=0) and after the immersion cycles. The data were analyzed by 2-way analysis of variance (ANOVA) for repeated measures and the Tukey post hoc test (α=.01).

RESULTS

Sa was significantly increased in all groups after 1825 cycles compared with baseline (P<.01), regardless of the solution. Only the time factor significantly affected ΔEab, ΔE00, and NBS parameters, which were below the perceptibility and acceptability thresholds. After a simulated 5-year immersion, the surface roughness and color values of CA-treated specimens were not statistically different from those of the other groups (P>.01).

CONCLUSIONS

Cinnamaldehyde solution (27 μg/mL) produced minor effects on the surface roughness and color parameters of a heat-polymerized denture base resin similar to those of 0.5% sodium hypochlorite and alkaline peroxide after a 5-year simulated immersion.

Three-Dimensional Surface Texture Analysis of Fluoride's Effect on Enamel Erosion

Enamel erosion has become a common clinical finding that often impairs dental esthetics and function. In the current study, we aimed to implement the three-dimensional surface texture analysis (3DST) method to explore the protective effect of fluoride on surface texture prior to erosive conditions. For each of the 50 teeth used in this study, the polished buccal enamel surface was divided into three separate areas: the first area was untouched polished enamel, the two other surfaces were immersed in 0.3% citric acid for 30 s. One was treated with high-concentration (19,000 ppm) sodium fluoride (NaF) solution prior to acid attack, and the other had no treatment prior to acid exposure. Enamel surface texture and step height measurements were obtained using a high-resolution disk scanning confocal microscope, and SEM images were also acquired. Surfaces treated with fluoride showed fewer variations in 3-D surface texture parameters than the eroded surface compared to the control group (p = 0.001). This was in accordance with the SEM descriptive images. The findings indicate that pre-fluoridated enamel areas were less affected by the acid and showed similar features to the untouched enamel. Moreover, a protective effect of the fluoride treatment against irreversible enamel damage was noted as the surface loss (step-height) was significantly reduced (p = 0.03). The study showed that 3DST analysis is a valuable methodology for detecting and quantifying subtle differences between the surfaces. When exploring the combination of all surface texture parameters, it was revealed that the pre-fluoridated eroded enamel surfaces showed considerable similarity to the untouched enamel.

Effects of different irrigation protocols on dentin surfaces as revealed through quantitative 3D surface texture analysis

The combination of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) has been advocated as an effective irrigation methodology to remove organic and inorganic matter in root canal therapy. Yet, it was suggested that both solutions might lead to structural changes of the dentinal wall surface, depending on the order of application which might affect sealer mechanical retention. This study aims to evaluate the effect of different irrigating protocols on dentin surface roughness using quantitative 3D surface texture analysis. Data stems from 150 human root dentin sections, divided into five groups, each prepared according to one of the following protocols: Negative control; 17% EDTA; 17% EDTA followed by 5.25% NaOCl; 5.25% NaOCl; and 5.25% NaOCl followed by 17% EDTA. Each dentin sample was examined for its three-dimensional surface texture using a high-resolution confocal disc-scanning measuring system. EDTA 17% and the combined EDTA 17% with NaOCl 5.25% showed considerably higher roughness properties compared to the control and to NaOCl 5.25% alone. However, the irrigation sequence did not affect the dentin roughness properties. Therefore, mechanical retention is probably not dependent upon the selection of irrigation protocol sequence.