ROUGHNESS VARIATION OF A NANOHYBRID COMPOSITE RESIN SUBMITTED TO ACID AND ABRASIVE CHALLENGES.

The present study aimed at assessing the surface roughness of a nanohybrid composite after finishing and polishing, and at evaluating the roughness variation of the material after submitting it to the action of hydrochloric acid and toothbrushing. The material used in the study was Filtek Z550 (3M ESPE). 15 cylindrical samples were randomly divided into three groups, corresponding to three different systems (SofLex, Optrafine, Astropol). The samples were subjected to hydrochloric acid in two one-hour cycles, then immediately submitted to toothbrushing in three consecutive cycles (1,000, 2,000, 4,000 cycles). The results showed variations in surface condition after each step. The surface condition of restorations is related to the type of finishing system. Hydrochloric acid influences the surface roughness of a composite resin restoration, changing its values, even at limited exposure. The effect of brushing after acidic challenge increases the surface roughness of the composite resin. [ABSTRACT FROM AUTHOR]