Objective To compare the fracture resistances of teeth restored with 3 different posts-core and failure modes. Methods 54lower premolarsendodontically treated teeth were selected for thisstudy and divided into three groups randomly (without ferrule, 1 mm ferrule and 2 mm ferrule). Each group was then divided into 3 sub-groups (6 teeth in each group) and restored with cast post-core, glass fiberpost-core, andceramic post-core respectively. After thermocycling specimens , the fracture resistance was measured using a cyclic fatigue testing machine. Data were analyzed with 2-way ANOVA (α = 0.05). Results Fiber post-core group exhibited significantly higher resistance to fracture compared with groups of cast post-core and ceramic post-core (P<0.05). Preparing dentin ferrules increased significantly fatigue resistance (P < 0.05). Conclusions Glassfiber posts were able to preserve and reinforce the remaining tooth structures. Dentin ferrule preparation is necessary to enhancefractureresistance.

Objective To investigate human pulpal response to mineral trioxide aggregate (MTA) and calcium hydroxide (CH) as pulp capping agents. Methods This study was conducted on 90 intact first and second premolars of human maxillary and mandibular teeth of 30 volunteers. The patients were randomly assigned into three groups with 10 in each group. Under local anesthesia, the teeth were exposed and capped either with MTA, or CH. After 30, 60, and 90 days, 10 teeth of each group were extracted and prepared for histologic ob-servation. The data were analyzed with Wilcoxon rank sum test and paired t-tests (α = 0.05). Results MTA had a higher success rate and resulted in less pulpal inflammatory response and more predictable hard dentin bridge formation than CH (P < 0.05). Conclusion MTA appears to be a suitable replacement for CH in direct pulp capping.

Objective To investigate the differences of tooth bending force of three kinds of fiber post in front teeth repair. Methods The number of incisor teeth in the upper jaw was 36. Immediately after dealing with the root canal filling and removing crown in the four groups:group A CAD/CAM integration of glass fiber post , group B plastic fiber pile + resin cores ,advance into the fiber pile group C + resin cores ,group D as control metal crown repair directly after root canal treatment. And the first three samples were selected by using casting metal crown. After recording and repairing the test data ,and analyzing its failure form ,the test results were analyzed by the single factor analysis. Results In the antifold test,the anti-folding force of(247.4±24.43)N, (203.5 ± 24.46)N ,(197.4 ± 25.09)N and (260.4 ± 33.43)N was observed in group A to D ,respectively. After statistical analysis,group A was better than group B and group C(P < 0.05),but with no significant difference between group A and D ,and between group B and C. It was observed that the fracture mode of each group was damaged in the neck of the tooth. Conclusion The anti-folding force of the integrated glass fiber core is better than that of the preformed glass fiber pile and the plastic fiber pile ,which is similar to the anti-folding perfor-mance of the natural tooth structure.