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.

Evaluation of mechanical properties of different polyetheretherketone endodontic post systems: an in vitro study.

BACKGROUND: Survival of endodontically treated teeth depends on an efficient restoration of the missing tooth structure. OBJECTIVES: This study aimed to investigate the mechanical properties of different endodontic post systems. MATERIALS AND METHODS: Human permanent maxillary central incisors (no.=58) were decoronated and root-filled. The specimens with prepared root canals were randomly divided into Group P: Polyether Ether Ketone (PEEK) post and composite core and Group C: custom-made post-core of PEEK. The cementation of the posts was carried out using self-adhesive resin cement. Nano-hybrid composite resin was used for core fabrication. After cementation, the specimens from each group were randomly divided into two subgroups according to the types of tests utilized: 14 from each group were for the fracture strength test, which was restored with IPS e-max CAD crown, and 15 from each group for the pullout resistance test. A universal testing machine was used for the test performance. RESULTS: The fracture resistance test showed that the values significantly differed among tested posts (P = 0.013). Group P showed the highest fracture resistance. Group C exhibited higher mean pullout resistance values than the other group (P) (P = 0.059). In the two-piece PEEK post and composite core, the predominant type of failure was a core fracture, while in the one-piece PEEK post-core, most types of failures were either in the crown or in the post. CONCLUSIONS: The prefabricated posts are more resistant to fracture than the custom-made posts, with fracture and displacement mainly of the core. In contrast, both showed similar pullout resistance.

Evaluation of video teaching on resident competency for all-ceramic crown tooth preparation.

PURPOSE: This study aimed to analyze the impact of live video instruction using digital evaluation of residents' performance in full ceramic crown preparation. METHODS: Digital evaluation using CEREC computer-aided design/computer-assisted manufacturing (CAD/CAM) 5.1.3 software was conducted of preparation on a typodont for all-ceramic crowns of mandibular first molars (MFMs) with a radial shoulder finish line, carried out by 30 residents. Each participant prepared two MFMs: group A prepared the right side without live video instruction, and group B prepared the left side after instruction. All prepared teeth were scanned by Dentsply Sirona chairside CAD/CAM system with Omnicom to assess the inter-occlusal space, undercut, the finish line of the preparation, and surface texture. The data were analyzed using Pearson Chi-square, Wilcoxon signed-rank test, and paired t-test. P-values less than 0.05 were considered to be statistically significant in all tests. RESULTS: Based on the Pearson Chi-square test, there were significant differences between the two groups in terms of inter-occlusal space on the buccal and lingual surface of the prepared tooth, in the presence of rough surfaces before and after the preparation, and difference in the type of finish line. The Wilcoxon signed-rank test revealed a significant difference in convergence angle buccolingually and the remaining height of the prepared teeth before and after the video instruction. CONCLUSIONS: The use of educational live video instruction can be helpful to residents in learning the principles of tooth preparation.