Polish of Rough Composite Surfaces by Tooth Brushing

Objectives: Bulk fill (BF) resin-based composite (RBC) manufacturers until recently have sacrificed esthetic properties for high depth of cure (DOC), low polymerization shrinkage stress, and adequate mechanical properties. This study reports change in polish, an important property of esthetic dental materials, of pre-roughened composites over 0, 1500, 3000, 4500, and 6000 tooth brushing cycles. Five common BF-RBCs are compared, including 3M™ Filtek™ One Bulk Fill Restorative (FO), 3M™ Filtek™ Bulk Fill Posterior Restorative (FBFP), Kerr SonicFill™ 2 (SF2), Ivoclar Tetric EvoCeram® Bulk Fill (TECBF), and VOCO Admira® Fusion x-tra (AFX). 3M™ Filtek™ Supreme Ultra Universal Restorative (FSU) is included in the study as a control, as it has been previously reported that roughened surfaces of it are polished by tooth brushing. Gain or loss in polish is hypothesized to be dictated by the filler used in the composite.
Methods: Composites were pressed in molds (n=5) at 10,000 lbs for > 1 minute, light cured at 800 mW/cm² for 20 seconds on each side, and abraded to a uniform roughness with 600 grit sandpaper. Three gloss measurements were made on each sample using a Novo Curve Gloss Meter and averaged after toothbrushing for 0, 1500, 3000, 4500, and 6000 cycles, and compared using ANOVA with Tukey Pairwise Comparison.
Results: Nanofilled composites FO, FBFP, and FSU increase significantly in gloss after 6000 brushing cycles, while the three (nano)hybrid BF-RBCs tested decreased significantly in gloss. Superscripts in the 6000 brushing cycles column denote statistical grouping via ANOVA with Tukey’s comparison with 95% confidence.
Conclusions: Tooth brushing significantly polishes a roughened surface of the nanocomposite materials tested, while the roughened surfaces of nanohybrid composites tested became lower in gloss. This positive gloss development behavior of the nanocomposite materials highlights the esthetic benefits of their nanoparticulate fillers.