Changes in color and staining of dental composite resins after wear simulation

Abstract

OBJECTIVES: The objectives were to measure the discoloration as well as the change in staining of composite resins after wear simulation. METHODS: Generalized wear simulation was performed with a three-body wear testing device for 400,000 cycles for six composite resins. A flat-planed stylus made with polyacetal resin was loaded perpendicularly under a load of 76-80 N. Color of nonworn and worn areas was measured with a spectrophotometer before and after staining with 0.5% methylene blue solution. Nonworn surface served as a control. Differences in color between nonworn and worn surfaces were calculated to indicate the change in color due to wear. Color change after staining with 0.5% methylene blue solution for nonworn and worn surfaces was calculated to observe the changes in staining. RESULTS: Color difference (DeltaE(*) (ab)) between nonworn and worn surfaces was in the range of 0.8-1.4 before staining, which increased to 1.1-3.9 after staining. Color change by staining with methylene blue in nonworn surface was 6.8-20.6, and that in worn surface was 5.2-17.8. Therefore, staining in nonworn surface was higher than that in worn surface (p < 0.05). Generalized wear simulation for approximately 3 years of clinical service resulted in acceptable color change before staining (DeltaE(*) (ab) < 3.3). After staining, color difference between nonworn and worn surface increased to not-acceptable value in one composite resin investigated.