Retention of fiber-post not affected by cements but cyclic loading

Abstract

Objective: To compare the micro-push-out bond strengths of a fiber-post cemented with two dentine adhesive systems in extracted human teeth with and without simulated occlusal loading. Methods: Human extracted, single-rooted teeth were decoronated above the CEJ to a standard length, root canal-treated, and then randomly divided into four groups (n=16 each). A fiber-reinforced root canal post system (Radix; Dentsply Maillefer) was cemented either with a chemically cured (Panavia F; Kuraray) or a self-etch self-adhesive resin composite cement (SmartCem2; Dentsply Maillefer) according to the manufacturer instructions, followed by a resin composite build-up to a standard shape. A layer of silicon sealant was painted over the root surface to about 2 mm below the CEJ, to imitate the periodontal ligament before embedding the root in mold for simulated occlusal loading. A total of 120,000 load cycles up to 70 N were applied for each tooth. Then, the roots were horizontally sectioned into slices of about 1 mm thick. Push-out test was performed at a cross-head speed of 1 mm/min in a universal testing machine (Instron). Data was analyzed using one-way ANOVA and two-sample t-test, where appropriate, at a significance level of 0.05. Results: No significant difference was found in the micro-push-out bond strengths at various horizontal levels for specimens of each individual group (ANOVA, P > 0.05). Panavia and SmartCem2 demonstrated similar bond strengths without loading (14.0±5.3 and 15.5±7.2 MPa, respectively). There was a significantly reduction in bond strength for both materials due to the simulated loads (P < 0.05). After loading, Panavia (5.9±3.3 MPa) showed a significantly lower bond strength than SmartCem2 (13.0±7.8 MPa) (P < 0.001). Conclusion: While the “static” bond strength for retaining a fiber-post is comparable, the two types of resin cement are both adversely and significantly affected by functional loads, but to different extents.