Original and repair bond strength of fiber-reinforced composites in vitro

Abstract

Objective: A great benefit of FRC technology is that, in case of minor failure events, restorations can be repaired or reinserted. However, various FRC materials are available, that differ in matrix composition and fiber pre-treatment. The aim of this investigation was, therefore, to evaluate original and repair bond strength of FRC materials.

Methods: Five fully pre-impregnated, unidirectional FRCs were selected, one semi-interpenetrating polymer network FRC and four cross-linked-polymer FRCs. The primary endpoint was the evaluation of shear bond strength (SBS) between FRC and composite resin, which was performed by a universal testing machine. For each FRC specimens were divided into control (original SBS, resin to fresh FRC with oxygen inhibition layer (OIL), n=30) and test groups (repair SBS, resin to FRC after removal of OIL and adhesive infiltration, n=30).

Results: The cross-linked-polymer FRC GrandTec(®) (12.4±5.4 MPa) yielded the highest control SBS, followed by the semi-interpenetrating polymer network FRC (everStick(®), 9.2±3.5 MPa). With everStick(®), repair led to a significant increase in the test SBS (14.6±5.8 MPa, p=0.01).

Significance: Control SBS was best with GrandTec(®) indicating that the material is superior in direct clinical application. Test SBS was significantly increased with everStick(®) which points at potential reparability and advantages in semi-direct or indirect fabrication of fiber-reinforced fixed partial dentures.

Keywords: Cross-linked polymer; Interdiffusion; Repair; Resin matrix; Semi-interpenetrating polymer network; Shear bond strength.