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 degreesC. 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. (C) 2003 Elsevier Ltd. All rights reserved.