Análise de sobrevida e resistência à fratura de raízes fragilizadas restauradas com diferentes pinos intrarradiculares

Abstract

Objectives: To evaluate the survival analysis and the fracture resistance of weakened (W) and not weakened (NW) roots restored with different intracanal systems posts. Methods: Eighty teeth were sectioned in 16mm and prepared in 12mm with a custom drill. Fifty roots were weakened with a tapered diamond drill and 30 kept without weakening. The specimens were embedded with acrylic-resin in PVC cylinders until 3mm coronal (bone limit) and the periodontal ligament was simulated with polyether material. The experimental design was: G1 and G2: cast and post core (Golden Alloy) with (CPC-GL W) or without (CPC GL NW) weakened roots, respectively; G3 and G4: cast and post core (Ni-Cr alloy) with (CPC Ni W) or without (CPC Ni NW) weakened roots, respectively; G5 and G6: fiber-posts with (FP NW) or without (FP W) weakened roots; G7: fiber-posts especially designed for weakened roots (FP-E W); G8: fiber-posts relined with composite-resin for weakened roots (FP-CR). All posts were adhesively cemented. All of the restored specimens were submitted to the mechanical cycling (37ºC, 45º, 130N, 2.2Hz and 1.5 million pulses) and follow up intervals between cycles 5x104 evaluating the presence of the event "crack". The specimens that survived the mechanical cycling were subjected to the fracture-resistance test under load application on palatal zone at 45º-inclination (cross-head speed = 1 mm/min) until failure. Failure mode was classified in favorable (above the simulated bone limit) and catastrophic (below the simulated bone limit). Survival rates were estimated using the technique of Kaplan-Meier method and survival rates according to the study groups were analyzed using the log-rank test (p≤0.05). Fracture resistance data were analyzed by the one-way ANOVA and Tukey test (p=0.05). Results: The post-hoc comparisons showed differences between specimens in groups FP-E and CPC (p=0.004). For fracture resistance statistical differences (p<0.0001) were depicted among the weakened groups: CPC-GL 541.4227.4A, CPC-Ni 642.6219.5A, FP- 282.264.7B, FP-E- 274.151.3B, FP-RC- 216.663.6B. No differences were observed for groups without weakening: CPC-GL- 459.3111.1A, CPC-Ni- 422.0151.9A and FP- 347.991.8A, with majority of favorable failures. Conclusions: weakened roots restored with CPC promoted high values of fracture toughness and failure rates unfavorable. There was higher survival rate for FP-E in relation to CPC (GL / Ni).