Enamel thickness of maxillary canines evaluated with microcomputed tomography scans

Three-dimensional mapping of the enamel thickness on the labial surface of maxillary and mandibular incisors

STATEMENT OF PROBLEM

Within-enamel preparation provides higher bond strength in minimally invasive esthetic treatment. However, determining the distribution of enamel thickness on the labial surface of human incisors remains difficult.

PURPOSE

The purpose of this in vitro study was to reconstruct and map the labial enamel thickness of the maxillary and mandibular incisors.

MATERIAL AND METHODS

Sixty human incisors, including 20 maxillary central incisors (MxCIs), 20 maxillary lateral incisors (MxLIs) and 20 mandibular incisors (MdIs), were scanned using microcomputed tomography. The labial enamel was reconstructed into 3-dimensional models and divided into 9 segments (mesial-cervical, central-cervical, distal-cervical, mesial-middle, central-middle, distal-middle, mesial-incisal, central-incisal, and distal-incisal segments). The enamel thicknesses of different segments of the labial enamel were measured and analyzed. Statistical analysis was performed using the paired t test and analysis of variance (α=.05).

RESULTS

The enamel thickness of MxCIs was 0.461 to 0.966 mm, the enamel thickness of MxLIs was 0.346 to 0.984 mm, and the enamel thickness of MdIs was 0.343 to 0.792 mm. The labial enamel thickness was significantly different between the maxillary and mandibular incisors (P<.05). In all incisors, the enamel was thickest in the incisal region and significantly thinner in the cervical region (P<.05). The distal enamel was significantly thicker than the mesial enamel in MxCIs (P<.01), whereas the central enamel was thicker than the mesial enamel in MdIs (P<.01).

CONCLUSIONS

The labial enamel thickness was significantly different between the maxillary and mandibular incisors (P<.05). Horizontally, the mesial enamel was thinner than the distal enamel in the MxCIs, whereas the central enamel was thicker than the mesial enamels in the MdIs. Vertically, the labial enamel thickness increased from the cervical region to the incisal region in all incisors.

Assessing Enamel Thickness to Estimate Interproximal Reduction: A CBCT-Based Study

OBJECTIVES

The aims of this study were to (1) estimate the mesial and distal proximal enamel thickness available (PETa), (2) estimate the proximal enamel thickness remaining (PETr) on the basis of planned IPR, and (3) assess PETr-associated risks with varying IPR amounts.

MATERIALS AND METHODS

A cross-sectional study was conducted using CBCT scans. PETa was estimated using on-demand software. Mesial and distal PET were measured at the middle third of the crown. The means and 95% confidence intervals (CIs) of the PETa and PETr data are reported. Differences between the mesial and distal PETa values were compared.

RESULTS

A total of 1615 teeth were analyzed via CBCT. The mean PETa values ranged from 0.96 to 1.29 mm (mesial) and from 0.98 to 1.25 mm (distal). Differences between mesial and distal PETa were statistically significant, averaging 0.10 mm proximally (p < 0.050). In particular, these differences were observed in cuspids, including tooth 13 (1.18 ± 0.24 vs. 1.25 ± 0.28; p = 0.021), tooth 23 (1.25 ± 0.26 vs. 1.15 ± 0.28; p < 0.001), tooth 33 (1.22 ± 0.26 vs. 1.10 ± 0.23; p < 0.001), and tooth 43 (1.29 ± 0.24 vs. 1.13 ± 0.20; p < 0.001). The mean PETr values for single-site IPRs < 0.4 mm were 0.58 mm (mesial) and 0.57 mm (distal). Exceeding a single-site IPR of 0.20 mm significantly increased the proportion of interproximal sites classified as moderate or high risk, particularly in teeth with thinner enamel (< 0.7 mm).

CONCLUSIONS

PETa and PETr are critical for determining safe and individualized IPR. CBCT-based PETa evaluations are strongly recommended when single-site IPRs exceeding 0.20 mm are planned to increase precision and reduce the risk of excessive enamel reduction.

Clinically oriented automatic three-dimensional enamel segmentation via deep learning

BACKGROUND

Establishing accurate, reliable, and convenient methods for enamel segmentation and analysis is crucial for effectively planning endodontic, orthodontic, and restorative treatments, as well as exploring the evolutionary patterns of mammals. However, no mature, non-destructive method currently exists in clinical dentistry to quickly, accurately, and comprehensively assess the integrity and thickness of enamel chair-side. This study aims to develop a deep learning work, 2.5D Attention U-Net, trained on small sample datasets, for the automatical, efficient, and accurate segmentation of enamel across all teeth in clinical settings.

METHODS

We propose a fully automated computer-aided enamel segmentation model based on an instance segmentation network, 2.5D Attention U-Net. After data annotation and augmentation, the model is trained using manually annotated segmented enamel data, and its performance is evaluated using the Dice similarity coefficient metrics. A satisfactory image segmentation model is applied to generate a 3D enamel model for each tooth and to calculate the thickness value of individual enclosed 3D enamel meshes using a normal ray-tracing directional method.

RESULTS

The model achieves the Dice score on the enamel segmentation task of 96.6%. This study provides an intuitive visualization of irregular enamel morphology and a quantitative analysis of three-dimensional enamel thickness variations. The results indicate that enamel is thickest at the incisal edges of anterior teeth and the cusps of posterior teeth, thinning towards the roots. For posterior teeth, the enamel is thinnest at the central fossae area, with mandibular molars having thicker enamel in the central fossae compared to maxillary molars. The average enamel thickness of maxillary incisors, canines, and premolars is greater than that of mandibular incisors, while the opposite is true for molars. Although there are individual variations in enamel thickness, the average enamel thickness graduallly increases from the incisors to the molars among all teeth within the same quadrant.

CONCLUSIONS

This study introduces an automatic, efficient, and accurate 2.5D Attention U-Net system to enhance precise and efficient chair-side diagnosis and treatment of enamel-related diseases in clinical settings, marking a significant advancement in automated diagnostics for enamel-related conditions.

Quantitative Evaluation of Enamel Thickness in Maxillary Central Incisors in Different Age Groups Utilizing Cone Beam Computed Tomography a Retrospective Analysis

Background/Objectives: The presence of enamel on the tooth surface is crucial for the long-term success of minimally invasive adhesive restorations such as dental veneers. Our study aims to evaluate the enamel thickness in the incisal, middle, and cervical portions of the labial surface of the upper central incisors using cone beam computed tomography (CBCT). This imaging method provides detailed and accurate three-dimensional images with a low radiation dose, allowing an accurate assessment of enamel thickness. The analysis aims to identify variations in enamel thickness depending on the age and different levels of the labial tooth surface. Methods: 800 CBCT scans performed for diagnostic or therapeutic purposes on patients aged 18-60 years were analyzed. The data were gathered from the imaging archives of private practitioners from Targu Mures and the "George Emil Palade" University of Medicine, Pharmacy, Science, and Technology of Targu Mures. Enamel thickness measurements were conducted using the OnDemand3D Communicator CBCT evaluation program, with subsequent statistical analysis performed using GraphPad Instat Prism software. Results: Results showed significant variation in enamel thickness between the incisal, middle, and cervical segments of the labial surface of the upper central incisors. A decrease in enamel thickness with age has been observed. In patients aged 18-40, mean values of enamel thickness 1 mm and 3 mm above the cementoenamel junction (CEJ) were 0.48 ± 0.092, respectively, 0.819 ± 0.158. In patients over 40, the mean values were 0.454 ± 0.116 and 0.751 ± 0.067 at 1 mm, respectively, 3 mm above the CEJ. Statistically significant differences were found between the two age groups at 1 mm and 3 mm above the CEJ, with p < 0.0001 and p = 0.0214. Conclusions: A statistically significant decrease can be observed in enamel thickness in almost the entire labial surface of the upper central incisors with aging. The varied thickness of the enamel at different tooth levels requires individualized planning for each patient to maximize the long-term aesthetic and functional results.

Age and sex related change in tooth enamel thickness of maxillary incisors measured by cone beam computed tomography

BACKGROUND

To measure adequate enamel thickness of maxillary incisors in planning enamel reduction for a porcelain laminate veneer restoration in relation to chronological age and sex by using cone beam computed tomography (CBCT) in an Iraqi subpopulation.

METHODS

From 81 CBCT images, 324 maxillary incisors were examined. Enamel thickness was measured at both mesial and distal regions of the tooth in three different levels: cervical, middle, and incisal (occlusal) 1/3 at a sagittal section. Measurements were made for the following tooth areas using CBCT: facial enamel thickness at 1, 3, and 5 mm from the cementoenamel junction (CEJ), palatal enamel thickness at 5 mm from the CEJ (5 mm P), facial and palatal enamel thickness at the incisal edge (IFP), mid incisal enamel thickness (IET), and the incisal edge enamel-pulp distance (IEPD). Relationships of enamel thickness with age and sex were evaluated using Independent t-test, Mann-Whitney U-test and the Pearson correlation coefficient, a simple linear regression analysis used for statistical analysis.

RESULTS

Significant differences (P < 0.05) were found in terms of an inverse association between enamel thickness and chronological age at all measurements above the CEJ and the regression model for the mid-incisal enamel thickness was (R2 of 0.4). In contrast, there was an increase in IFP, palatal, and IPED enamel thickness with age. Also, significant differences were found in enamel thickness between males and females, the enamel being thicker in females in relation to facial enamel thickness, enamel palatal thickness above CEJ and IET, while for IEPD, the enamel thickness was greater in males compared to females.

CONCLUSION

The measurements for enamel thickness outcome variables in relation to chronological age revealed significant differences for each measured distance and there were statistically significant differences in enamel thickness between males and females at all measurements except at IFP. These results demonstrate that CBCT can be used for noninvasive, accurate measurements of enamel thickness in both sex.

Proximal enamel thickness of the permanent teeth: A systematic review and meta-analysis

INTRODUCTION

This systematic review aimed to identify, evaluate, and provide a synthesis of the available literature on the proximal enamel thickness (PET) of permanent teeth.

METHODS

The eligibility criteria were studies that assessed the PET of the permanent teeth. A search of studies in Medline (via PubMed), the Cochrane Library, Scopus, Web of Science, Embase, and Lilacs databases that measured PET was conducted until August 31, 2020. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias for systematic reviews involving cross-sectional studies. The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations approach. PET data generated from the systematic review were summarized by random-effects inverse-generic meta-analysis.

RESULTS

From 1388 potentially eligible studies, 11 were considered for systematic review and meta-analysis. The measurement of PET was done with radiographs, microscopes, microtomographs, or profilometers. In total, 4019 mesial and distal surfaces involving 2118 teeth were assessed. All included studies showed low to moderate risk of bias, whereas GRADE revealed that the level of evidence was low. Greater mesial and distal enamel thickness was observed for the premolars and molars, whereas it was least for the mandibular central incisors. The least difference of 0.02 mm (95% confidence interval [CI], -0.07 to 0.11 and -0.06 to 0.09, respectively) between mesial and distal sides was observed for the maxillary and mandibular second molars, whereas the maximum difference of 0.12 mm (95% CI, 0.07-0.17 and 0.07-0.16, respectively) was observed for the maxillary central incisors and maxillary first premolars. The meta-analysis indicated a moderate level of heterogeneity (I² of 45%). The funnel plot revealed minimal publication bias.

CONCLUSIONS

The summary effect of the meta-analysis revealed that the thickness of the enamel on the distal aspect was greater than on the mesial aspect by an average of 0.10 mm (95% CI, 0.09-0.12). This finding would be of relevance to all disciplines of dentistry and especially for the clinician planning interproximal reduction, a procedure that is routinely done for clear aligner therapy.

Non-Invasive Optical Coherence Tomography Data-Based Quantitative Algorithm for the Assessment of Residual Adhesive on Bracket-Removed Dental Surface

The aim of this study was to quantitatively assess the residual adhesive on orthodontic ceramic bracket-removed dental surface. In orthodontic process, ceramic bracket was repeated debonding physically, then the adhesive remained on the dental surface. The residual adhesive caused a lack of adhesive strength between dental and ceramic bracket. Since commonly used adhesive in orthodontics is translucent, residual adhesive is hard to be detected with conventional microscopes. Therefore, 1310 nm center wavelength swept-source OCT system based on laboratory customized image processing algorithm was used for the precise detection of residual adhesive on tooth surface. The algorithm separates residual adhesive from dental surface by comparing the height of adjacent B-scan images, while providing color-scaled images emphasizing the thickness information of residual adhesive. Finally, the acquired results were compared with microscopic and adhesive remnant index scoring gold standards, while the comparison confirmed the potential merits and the improvements of the proposed method over gold standards.