In Vitro Study Comparing Fracture Strength Recovery of Teeth Restored with Three Esthetic Bonding Materials Using Different Techniques

Reattachment of the fractured fragment of a traumatized tooth (whenever available and usable) has become the treatment of choice in cases of uncomplicated crown fractures. Despite the presence of various bonding materials and techniques, laboratory data evaluating the biomechanical aspects of such procedures is largely lacking in the literature. The objective of this in vitro study was to evaluate the fracture strength recovery of incisors, following fragment restoration with three different esthetic bonding materials using three different techniques. A total of 90 extracted human maxillary central incisors were subjected to crown fracture under standard conditions. This was carried out by applying a compressive force from the buccal aspect of the clinical crown using a universal strength testing machine. The fractured teeth were equally distributed in three groups, defined on the basis of the technique used for reattachment: i) overcontour, ii) internal dentinal groove and iii) direct buildup. Each group was further subdivided into three subgroups on the basis of the intermediate restorative material used for reattachment, namely: i) hybrid composite (Filtek Z100 Universal Restorative), ii) nanocomposite (Filtek Z350) and iii) Ormocer (Voco Admira). Following reattachment, the crowns were re-fractured under standard conditions. The force required for fracture was recorded and was expressed as a percentage of the fracture strength of the intact tooth. The data was analyzed using two-way ANOVA and Bonferroni tests for pair-wise comparison. The results showed no statistically significant differences in fracture strength between the three groups (P >0.05). However, comparison of the subgroups revealed statistically significanty higher strength recovery percentages for the hybrid and the nanocomposite compared with the Ormocer material (P 0.05). It was concluded that material properties have a significant influence on the success of reattachment procedures.