Composite resin reinforced with pre-tensioned glass fibers. Influence of prestressing on flexural properties

Objectives. This investigation evaluated the flexural properties of two composite resins, and the influence of unidirectional glass fiber reinforcements, with and without pre-tensioning. Methods. Two composite resins (Q: Quixfil and A: Adoro) were used to fabricate 2 mm x 2 mm x 25 mm beams (N = 10), reinforced with two fiber bundles along the long axis of the beam and pre-tensioned under a load equivalent to 73.5% of its tensile strength (groups QPF and APF). In two other experimental groups, the bundles were similarly positioned but without pre-tension (groups QF and AF). Two more groups were included without fiber reinforcement ( control groups Q and A). After 24 h storage, specimens were subjected to a three-point flexural bending test to establish the flexural module, the deflection at initial failure and the flexural strength. Data were analyzed using a two-way analysis of variance ( composite resin system and fiber reinforcement type) and the Tukey HSD post hoc tests (alpha=.05). Results. The results showed that prestressing increased the flexural module of Adoro specimens (p<.001) but not Quixfil (p=.17). Prestressed beams reached greater deflection at initial failure than those conventionally reinforced (p<.001), namely .85-1.35 mm for Adoro and .66-.90 mm for Quixfil. Prestressing also significantly increased the flexural strength of beams (p<.001) in both Adoro and Quixfil groups, from 443.46 to 569.15 MPa and from 425.47 to 568.00 MPa, respectively. Significance. Pre-tensioning of unidirectional glass fibers increased both deflection until initial failure and flexural strength of Quixfil and Adoro composite resins, however, with limited effects on the flexural modulus. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.