The influence of fiber reinforcement of composites on shear bond strengths to enamel

Abstract

Statement of Problem. Fiber-reinforced composites (FRC) are used in direct intra-oral applications as periodontal splints and chairside tooth replacement by bonding them to etched enamel with resin adhesives and composites. There is little information regarding the effect of FRC on the shear bond strength of composite to etched enamel. Purpose. The purpose of this study was to examine the effect of resin preimpregnated and non-preimpregnated fiber-reinforced composites on enamel to composite shear bond strength (SBS). Material and Methods. Specimen groups (n = 12) consisted of a control (composite with no fiber reinforcement), Ribbond, Splint-It Unidirectional, Splint-It Woven, and Connect, which were bonded to 37% phosphoric acid etched Prime and Bond NT adhesive-treated bovine enamel surfaces on a bed of Tetric Flow composite. Specimens were thermocycled 1000 times between 5° and 55°C and loaded on a universal testing machine in shear at a linear increasing load until fracture (MPa). The fractured surfaces of the debonded specimens were evaluated to determine the nature of the fracture with a light binocular microscope (×10). Shear bond strength data were subjected to analysis of variance (ANOVA) and Student-Newman-Kuels tests (P <.05). Results. Mean MPa ± SD for the test groups were as follows: Control, 15.6 ± 2.4; Splint-It Unidirectional, 15.3 ± 2.4; Splint-It Woven, 16.5 ± 1.8; Connect, 18.8 ± 1.5; and Ribbond, 15.8 ± 2.2. The Connect FRC group had significantly higher (P <0.05) enamel SBS than all other groups. Fracture analysis showed varying types of failures among the groups, with cohesive fractures within the fiber reinforcement of Splint-It Unidirectional and Connect, cohesive fractures within the bonding resin/flowable composite for Ribbond and the control, and adhesive fracture at the fiber reinforcement interface with Splint-It Woven. Conclusion. Within the limitations of this study, no differences in SBS were observed with the addition of 3 of the 4 FRCs compared to composite without FRC, with the exception of the Connect product which provided significantly higher SBS values. (J Prosthet Dent 2003;89:388-93.)