Influence of mechanical and chemical degradation on surface gloss of direct and CAD-CAM resin composite materials.

PURPOSE: To compare the gloss retention of four resin based materials, two direct resin composites (Tetric EvoCeram and Filtek Supreme) and two indirect resin composite CAD-CAM blocks (Tetric CAD and Lava Ultimate). METHODS: 36 samples of 1 mm thickness were readied of each test material and manually polished with polishing discs (Sof-Lex) up to the finest grit size. Three gloss measurements per sample were taken (one every 120 degrees of sample rotation) by means of a glossmeter (Novo-Curve) for a total of 60 values obtained per tested material. Samples of each material were then randomly divided into three equal groups and aged with 75% alcohol (Group 1), amine fluoride gel (Elmex gelée) (Group 2) or mechanical brushing (Group 3). Another set of gloss measurements was performed on all samples after 1 hour of aging. Gloss values were statistically evaluated by means of repeated measures ANOVA and Fisher's LSD post-hoc tests. RESULTS: Gloss retention values ranged from 59.0 (Tetric EvoCeram) to 70.9 (Lava Ultimate) for alcohol, from 59.3 (Filtek Supreme) to 67.5 (Lava Ultimate) for Elmex gelèe and from 33.3 (Tetric EvoCeram) to 53.4 (Lava Ultimate) for mechanical brushing. Statistical analysis revealed: (1) significant difference between intial and final gloss values for all materials and groups; (2) significant difference between final gloss values of all the materials in the alcohol group; (3) significant difference between final gloss values of Lava Ultimate and all the other materials in the Elmex gelèe group; (4) significant difference between final gloss values of Lava Ultimate and Tetric CAD with the other tested materials in the brushing group. CLINICAL SIGNIFICANCE: Direct resin composites in general are widely used, and CAD-CAM resin composite materials are becoming progressively more accessible. Making the choice between direct and indirect techniques is still a challenge, and understanding the advantages of CAD-CAM resin composites in the form of higher gloss retention, which translates into higher durability of esthetics, may be one the parameters facilitating the decision.