Flexure strength of methacrylate- and ormocer-based bulk fill resin composites: effect of material thickness and distance to photo-polymerization device

Abstract

This study evaluated the effect of thickness and photo-polymerization distance on flexure strength of two bulk fill resin composites. In total, 96 rectangular-shaped resin composite bars were divided into eight experimental groups (n = 12/group) according to the three experimental factors; Factor 1: Material (X-tra fil and Admira Fusion X-tra), Factor 2: Thickness (2 mm and 4 mm) and Factor 3: photo-polymerization distance (2 mm and 8 mm). The bars were prepared with fixed 2 mm width and 2 mm length but differed in thickness (2 mm or 4 mm). The bars were light cured either at 2 mm or 8 mm distances. Flexure strength test was run at a crosshead speed of 0.5 mm/min. Data were analyzed using 3-Way ANOVA/Student t-test. Methacrylate-based resin composite exhibited significant higher flexure strength (p < 0.001). At 2 mm distance, there was no significant difference between 2 mm and 4 mm thicknesses for X-tra fil and Admira Fusion X-tra (p = 0.726 and p = 0.486, respectively). At 8 mm distance, both materials showed significantly higher flexure strength with 4 mm thickness compared to 2 mm thickness (p ˂ 0.001). Only X-tra fil with 2 mm thickness had no statistically significant difference on the flexure strength at 2 mm and 8 mm distances (p = 0.437). X-tra fil in 2 mm thickness cured at 8 mm distance and Admira Fusion X-tra in 4 mm thickness cured at 2 mm distance revealed the highest reliability. Methacrylate-based resin composite tested in this study had superior flexure strength compared to ormocer-based resin composite, regardless of the increment thickness and photo-polymerization distance.

Keywords:

• Thickness
• photo-polymerization distance
• bulk fill composite
• methacrylate composite
• ormocer composite
• flexure strength

Acknowledgments

The authors would like to thank VOCO GmbH, Cuxhaven, Germany for supplying the materials tested in this study.

Disclosure statement

The authors did not have any commercial interest in the materials used in this study.