RESUMO
A core restoration is often required after tooth fracture or extensive caries removal. The core should posses sufficient fracture toughness to resist occlusal and to be retained in tooth structure
Objectives: The aim of this work was to compare the torque fracture resistance of four core build-up materials. The effect of water aging on torque fracture resistance of these material was also, studied
Materials and Methods: Four direct core build-up materials were tested: [1] Vietremer [resin-modified glass-ionomer], [2] Arabesk Top [glass-ceramic microhybrid composite], [3] Build-It FR [Fiber-reinforced, fluoride-releasing, resin composite], [4] Fluorocore [fluoride-releasing, resin composite]. Notched disc test specimens of 5 mm diameter and 2 mm depth with a 90[degree sign] notch angle were prepared in specially designed Teflon mold. 20 specimens from each material were prepared according to manufacturer's instruction and then stored in distilled water at 37[degree sign] C until the time of testing. Half the specimens of each material [n=10] were tested after 1 day, and the other half were tested after 7 days. Fracture was accomplished in a Shimadzu testing machine with a 3 mm diameter roller in a two-point opening [Mode I] tensile load at a crosshead speed of 1 mm/min. The maximum loads were determined from which the torque to fracture values [T] were calculated. Data was analyzed by one-way ANOVA and post hoc Tukey tests among the materials and two-independent sample tests between aging intervals were performed at a preset alpha of p<0.05
Results: The mean torque fracture resistance [T] values in N/mm obtained, after 1 day and 7 days, were as follows: [1] Vitremere, 6.4 and 9.4; [2] Arabesk Top, 20.5 and 20.4; [3] Build-It FR, 24.4 and 23.8; [4] Fluorocore, 39.8 and 38.9. There was significant difference in T values among all materials either at 1 day or 7 days. After conditioning in water for 7 days, only the T value of Vitnemer was significantly increased, while that of Arabesk Top, Build-It FR, and Fluorocore was not affected
Conclusions: Fluorocore had the highest torque fracture resistance values and Vitremer had the lowest, while Build-It FR and Arabesk Top yielded intermediate values, either at 1 days or 7 days. Only, the torque fracture resistance of vitremer was significantly increased with water storage for 7 days