Changes in gloss after simulated generalized wear of composite resins

Statement of problem

Generalized wear of composite resins in the noncontact area may result in changes of gloss, which can influence esthetics of restorations.

Purpose

The purpose of this study was to determine the changes in gloss of composite resins after generalized wear simulation. Surface roughness and amount of wear were measured for comparison.

Material and methods

Generalized wear simulation was performed with a wear tester for 400,000 cycles with 6 composite resins (Estelite Σ, Esthet X improved, Filtek Supreme, Heliomolar, Renamel Microfill, and Tetric-Ceram). Composite resin was placed into a mold (8 mm in diameter, 3 mm in depth) in an acrylic resin block, and 8 specimens were prepared per group. A flat-planed stylus made with polyacetal was loaded perpendicularly. Gloss was measured after every 100,000 cycles with a glossmeter in gloss units (GU). Average surface roughness (R_a) of each specimen before and after 400,000 cycles of wear was determined. The amount of wear was measured with a 3-dimensional profilometer. Changes in gloss were analyzed by repeated-measures analysis of variance, and mean values were compared by Fisher's PLSD interval (α=.05).

Results

Gloss was influenced by the number of wear cycles and the composite resin, and there was a significant interaction (P=.000) between the number of wear cycles and the brand of composite resin. There were no significant correlations between the wear depth and the gloss or changes in gloss after 400,000 cycles.

Conclusion

Generalized wear simulation for approximately 3 years of clinical use resulted in gloss changes of 36 to 64 GU, and maximum wear depth was in the range of 35 to 75 μm. Change in gloss varied among the composite resins, but average surface roughness was not influenced by the various composite resins.