effect of horizontal pin on fracture resistance of composite restored endodontcally treated teeth

Restoration of endodontically treated teeth by a simple method, with low cost in a short time is one of the major problems in dentistry. The purpose of this study was to evaluate the effect of horizontal pins in fracture resistance of endodontically treated maxillary premolars restored with composite. In this study, 48 sound, closed apex, maxillary human premolars, without crack, extracted for orthodontic reasons, were randomly divided into 3 groups of 16 as follows; Group 1: intact [unprepared] teeth. Group 2; composite restoration without horizontal pin. Group 3: composite restoration with 2 horizontal pins in buccal cusp. In groups 2,3 after preparation of the standard access cavity and endodontic treatment, the palatal cusp was reduced to 1.5 mm coronal to the CEJ, leaving the remaining buccal cusp 3mm in buccolingual thickness at the height of contour. After thermocycling, each tooth was loaded in compression until fracture occured. Data were analyzed with one-way ANOVA and Tukey test. The pattern of fracture was analyzed by Chi-Square test. The mean fracture resistance in groups 1-3 were 689.59 +/- 179, 632.86 +/- 119 and 533.49 +/- 168 [in N] respectively. The differences between group 1 and group 3 were statistically significant [p<0.05]. Among patterns of fracture, the maximum number of favourable fractures occured in group 1 and the minimum number was in group 3. 1] Composite restoration with dentin bonding agents in endodontically treated maxillary premolars increased resistance to fracture. 2] Horizontal pins caused statistically significant reduction in fracture resistance of teeth. 3] The use of horizontal pins did not result in favorable fracture pattern

effect of mechanical surface conditioning methods on the shear bond strength of repaired composites

Considering the cost and quantity of tooth loss in the process of cavity preparation, repairing composite restorations instead of replacing them would be much more efficient. The aim of this study was to evaluate and compare the effectiveness of different mechanical surface treatment methods on the shear bond strength [585] between old and new composites. In this experimental in vitro study, 80 cylindrical specimens were fabricated from Tetric Ceram Composite [A[1], vivadent] and were preserved in 37°C distilled water. They were divided into 4 groups according to the surface treatment method: control [no treatment], roughening by a diamond bur, polishing with Sof-Lex disks and air-abrasion. All specimens were thermocycled [0.5-55°C, 500 cycles] prior to testing for SBS. An Instron Universal Testing Machine [5mm/mm Cross head imm] was used to evaluate the SBS of the specimens. Data were analysed by one-way ANOVA and Duncan tests. The highest to lowest shear bond strengths were seen in the Sof-Lex disk, air abrasion, diamond bur and control groups, respectively. A significant difference was observed between all three experimental groups [air abrasion diamond bur, Sof-Lex-disk] and the control group. There were no significant differences between the air abrasion and diamond bur groups, but the other groups revealed a significant difference when compared as pairs. Adequate wetting and induction of a microretentive surface, may explain the high SBS observed in the Sof-Lex group. The results of this study emphasize the importance of mechacinal surface conditioning prior to composite restoration repair