Influence of toothbrush abrasion on the surface characteristics of CAD/CAM composite resin blocks with shade gradations.

Crown restorations in anterior region are recommended highly color-reproductivity because of aesthetic reason. Composite resin block with several shade gradations is especially produced for anterior restorations. To clarify the durability of an aesthetic, the effect of toothbrush abrasion on surface properties was performed. Composite-resin blocks without shade gradation and a ceramic block were used as controls. All specimens were prepared using #2000 SiC paper and polished using an aluminum oxide polishing paste. Toothbrush abrasion tests were carried out for 20,000 cycles at a frequency of 2 Hz with 2.0 N load. Gloss and surface roughness were measured before and after toothbrush abrasion. The number of repetitions was set to five. It was clarified that tooth brushing caused to decrease in the gloss and to increase in the surface roughness with significant negative correlations between these results not only in composite-resin blocks without shade gradation but also in those with gradation.