Influence of different tooth preparation and bonding techniques on the fracture resistance of tooth fragment reattachment

PURPOSE: comparing the influence of different tooth preparation and bonding techniques on the fracture resistance of tooth fragment reattachment. MATERIALS AND METHOD: Ninety bovine central incisors were selected. Fifteen teeth act as a control (Group A). Experimental specimens were sectioned at the mesial-incisal proximal edge 3 mm from the incisal edge in a labio-lingual direction at 25degree inclination apically. Experimental specimens were then divided into five groups according to the tooth reattachment techniques utilized; Group B: no tooth preparation + Cured bond + Flowable composite; Group C: no tooth preparation + Uncured bond + Flowable composite; Group D: Bevel + bond + Flowable composite; Group E: Over-contouring + bond + Nanohybrid composite; Group F: Over-contouring + bond + Flowable composite. Specimens were subjected to thermocycling between 5 °C and 55 °C for 500 cycles with 30 sec. dwell time. Fracture strength was evaluated using universal testing machine. Data was analyzed using One-way ANOVA. RESULTS: There was a statistically significant difference between Group A and all the experimental groups, p < .001. Group E showed the highest statistically significant fracture resistance mean value compared to other experimental groups, while the lowest mean value was found in Group B. CONCLUSION: Though, none of the tested techniques resulted in fracture resistance similar to that of intact teeth, over-contouring technique with nanohybrid composite application showed better performances compared to the other techniques tested in the current study. Bonding plus flowable resin composite application with no additional tooth preparation and placement of a bevel are not suggested due to the low fracture strength achieved.