Static strength of molar region direct technique glass fibre-reinforced composite fixed partial dentures

The aim of this study was to determine static fracture force of fibre-reinforced composite (FRC) fixed partial dentures (FPD) with different retainer designs. The fabrication simulated the process to make directly made 3-unit maxillary molar FPD. Four types of retainers were tested (n = 5): conventional crown preparation (1.2 mm axially and 2.0 mm occlusally), slot preparation (3.5 mm high x 3.5 mm wide x 1 mm deep), no preparation with broad fibre abutment contact, and combination of the slot and broad fibre contact were performed. The FPD contained unidirectional E-glass FRC veneered with particulate reinforced composite. Dimensions of the FPDs were homogenized. FPDs were stored at 1 week 37 degrees C deionized water, thermocycled between 5 degrees C and 55 degrees C (5000 cycles, dwell time 10 s) and statically loaded to failure. The slot retainer design yielded the lowest mean load to initial and final failure (FF) (1284 and 1313 N, respectively), the crown retainer the highest mean load to initial failure at 1755 N, and the combination retainer resulted in the highest mean load to FF (1836 N) (ANOVA, P < 0.001; Tukey multiple comparisons, 0.05 significance level). The results of this study suggest that the fabrication of direct FRC FPD does not necessarily require extensive preparation for the retainers.