The reliability in flexural strength testing of a novel dental composite

Objectives. To investigate the reliability of bi-axial flexure and three-point flexure testing of an experimental, low-shrink oxirane-based dental composite, EXL596 compared with two conventional methacrylate based restoratives, Z250 and Z100. Methods. Specimens (n=20) of a novel oxirane-based composite and two commercially available methacrylate based composites were fabricated for flexural testing to evaluate mean bi-axial flexure strengths, three-point flexure strengths and the associated Weibull moduli (m) following 24 h immersion in a lightproof waterbath maintained at 37±1 °C. Results. Mean bi-axial flexure strengths and the associated m of EXL596, Z250 and Z100 were 168±11 MPa (m=16.2±4), 140±12 MPa (m=11.9±3) and 126±13 MPa (m=10.2±2), respectively. Three-point flexure strengths and the associated m of EXL596, Z250 and Z100 were 113±15 MPa (m=9.2±2), 92±10 MPa (m=8.5±2) and 79±16 MPa (m=6.3±1), respectively. Conclusions. The present investigation suggests that bi-axial flexure strength testing of dental resin-based composites provides a more reliable testing method than three-point flexure. The increased reliability was considered in terms of the associated Weibull moduli following bi-axial flexure testing as a result of the elimination of the additional induced variability introduced during the curing regime of three-point flexure specimens.