Influência da técnica restauradora na distribuição de tensões, resistência à fratura e deformação de cúspides de pré-molares tratados endodonticamente

Abstract

The aim of this study was to evaluate the fracture resistance, cuspal deformation and stress distribution of endodontically treated maxillary premolar, with direct and indirect MOD preparation and restored with amalgam, composite resin, laboratorial resin and ceramic, and to correlate these methodologies. Seventy human maxillary premolar with similar dimensions were selected and insert in polystyrene resin, simulating the periodontal ligament. The teeth received endodontic treatment and were divided in 7 groups (n=10): H - (control) sound teeth; PD - teeth with preparation mesio-ocluso-distal type (MOD) for direct restorations; PI - teeth with MOD preparation for indirect restorations; AM - teeth with MOD preparation, restored with amalgam; RCD - teeth with MOD preparation, restored with composite resin; RCI - teeth with MOD preparation restored with laboratorial resin; CE - teeth with MOD preparation restored with ceramics. The mechanical test had been submitted the axial of compression-load at 0.5mm/minute until the fracture. The fracture patterns was classified in 4 types. The data of fracture resistance was obtained in Kgf, submitted to the analysis of variance using one-way ANOVA and Tukey´s test (p<0.05). For the cuspal deformation test, 21 teeth used in previous study of resistance to the fracture with average dimensional standard of the samples had been selected (n=3). Two strain gauges were fixed parallel to the long axis of the tooth on the face buccal and palatine of the tooth. The mechanical test had been submitted the axial of compression at 0.5mm/minute continuous until 150N. Data obtained with maximum application of 150N for analysis of the association of buccal and palatine cusp submitted to the variance analysis and test of Dunnet (p<0.05). For analysis for the finite element method, 7 corresponding numerical models had been generated 2D that had been analyzed in software Ansys 7,1; using criterion of von Mises for analysis of the distribution of tensions. Fracture resistance values were: H- 114,7 ± 23,60A; RCD- 94,3 ± 20,61B; RCI- 93,0 ± 18,40B; CE- 78,7 ±13,11C; AM- 41,5 ± 16,38D; PD- 38,7 ± 15,11D; PI- 22,9 ± 14,21E. Cusp deformation results were: PI-636,20A; PD- 529,87A; AM- 462,72; RCI- 144,99B; RCD- 102,01B; H- 59,15B e CE- 56,74B. Finite elements analysis showed that the removal of structure and the type of restorative materials had modified the standard of distribution of tensions of the numerical models. Teeth with loss removal of structure and presence of adhesive restorations presented high values of fracture resistance, teeth with indirect resin restorations, amalgam and non-restored they presented catastrophic type of fracture; however, sound and restored teeth with ceramics presented less severe fracture. The type of preparation and restorative material directly influences in the cuspal deformation and stress distribution. The adhesive restorations had presented greater similarity with the biomechanic behavior of sound teeth, strengthening the dental structure, while that the amalgam restorations had presented more similar behavior to teeth nonrestored.