BackgroundDifferent crown-root angulations of maxillary central incisors can be assumed as a potential reason for many underscored outcomes of orthodontic treatments. The aim of this study was to determine the effects of the different crown-root angles on stress distributions in the maxillary central incisor’s periodontal ligament (PDL) during application of intrusive and retraction forces using a 3D finite element method.MethodsTwo models of a maxillary central incisor were constructed using ANSYS software: the first one with an angle of 166.7° (as a sample of the maxillary central incisor in a class II, division 2 patient) and the other one with an angle of 173.4° (normal angulation). Each of the samples was loaded twice by an intrusive force (0.25 N) and a retraction force (0.5 N) through the ideal position of brackets.ResultsFEM results showed little difference between stress distributions in the two models during intrusion (ten thousandth) compared to retraction (thousandth). In the application of retraction force, the stress concentration on the curved tooth was less than the other.ConclusionTo produce similar patterns of stress in the PDL, orthodontists can apply 1.18 times heavier retraction forces on the maxillary central incisors in class II, division 2 patients compared to class I patients.

Aim Core buildup composite resins with prefabricated posts are commonly used to restore endodontically treated teeth. This study compared the sealing ability of Core Max II and Panavia F2.0 cement with total-etch and self-etch adhesive systems. Methods and Materials Sixty recently extracted human second premolar teeth were chosen and their crowns were cut 3 mm above the CEJ. After preparing proximal boxes (4±1 mm buccolingually and 3 mm occlusogingivally dimensions) and finishing root canal therapy, the teeth were randomly divided into four groups (n=15): groups 1 and 2, Core Max II without and with total-etch adhesive; groups 3 and 4, Clearfil photocore composite, A2 shade, and Panavia F2.0 cement without and with self-etch adhesive respectively. The Dentatus posts (# 2 Long) were used in canals approximately 8 mm depth. According to manufacturer guidelines, pins were cemented and cores were restored. After keeping the specimens for 24 hours at 37°C and 100% humidity, they were thermally cycled for 500 cycles, sealed with nail varnish except 1 mm beyond the margins of restoration, and then immersed in a 0.5% fuschin basic for 24 hours. Samples were embedded in clear epoxy resin, sectioned mesiodistally, and observed at 20× magnification. The microleakage was assessed under stereomicroscope and the results were recorded in percentage of dye penetration to the whole path from the cavosurface margin of the proximal boxes to the end of the post. Analysis of variance and the Tukey test were used to evaluate the data (p=0.05). Results Groups 1 and 4 had the highest and the lowest values of microleakage respectively. Microleakage of Panavia F2.0 cement was lower than for Core Max II and for both cements using adhesive made the microleakage smaller than without it (p<0.05). Conclusion Application of adhesive using Core Max II cement and Panavia F2.0 cement is strongly recommended to decrease microleakage. Self-etch adhesive performed better than total-etch adhesive. Clinical Significance With regards to microleakage, the self-etching primer displayed better sealing than that obtained with the totaletching, two-step dental adhesive. Citation Moosavi H, Moazzami SM, Loh S, Salari S. Microleakage Evaluation of Core Buildup Composite Resins with Total-Etch and Self- Etch Adhesive Systems. J Contemp Dent Pract [Internet]. 2010 March; 11(2):009-016. Available from: http://www.thejcdp.com/journal/view/ volume11-issue2-moosavi.