Effect of Restorative Materials and Occlusal Loading on Cuspal Deflection

Objectives: The aim of this study was to evaluate the fracture resistance of human maxillary premolars restored with direct and indirect materials measuring cuspal deflection under occlusal load. Methods: Sixteen premolars were selected and distributed according with their bucco-lingual and mesio-distal dimensions in six groups: G1 - intacts teeth; G2 - prepared; G3 - restored with direct composite; G4 - restored with indirect resin ; G5 - restored with ceramics IPS Empress and G6 - restored with inlays produced by CAD CAM system. After cementation all the restorations received measurers from tension (strain-gauge) Modelo 060BG - Excel Sensory - Brazil) bonded to the buccal and lingual surfaces of the cusps of each tooth and were subject to a compressive axial load in a Universal testing machine at 0.5 mm/min contacting only the inner aspects of the buccal and lingual cusps. Measurements in µstrain had been made before and after the mechanical loading procedures frequently of 1Hz. Results: An exploratory data analysis was performed to determine the most appropriate statistical test. Analysis of Variance (ANOVA) for repeated measures and test of Tukey was carried before and after the mechanical loading procedures. Dunnett test was used to compare each treatment with the control Group. The results before the mechanical loading procedures in µstrain had been: G1- 577,02±2,70; G2- 583,37±2,76; G3- 579,16±3,92; G4- 578,12±1,38; G5- 578,68±1,57 and G6- 577,53±1,93 and the results had after been: G1- 577,02±2,70; G2- 584,38±0,827; G3- 579,24 ±0,976; G4- 578,24±1,05; G5- 578,74±0,788 and G6- 580,54±0,99. Conclusion: After analysis these results demonstrated that direct and indirect materials could reestablish the cuspal deflection returning partially the resistance fracture of intact teeth and it did not have significant difference between the direct and indirect materials before the mechanical loading.