Roughness and morphology of composites: influence of type of material, fluoride solution, and time

This study evaluated the effect of fluoride solutions on surface roughness and morphology of composites in the short and long term. Specimens were randomly assigned to experimental groups (n=5) according to type of composite (nanofilled, microhybrid, microfilled) and immersion media (artificial saliva, 0.05% sodium fluoride solution, Fluordent Reach, Oral-B, and Fluorgard). Roughness was evaluated at time intervals: T 0 after 24 h in artificial saliva (baseline); T 60 after being in assigned immersion media for 1 min daily over 60 days; and T final after artificial aging (20,000 thermal cycles, 1,200,000 mechanical loading cycles, and continuous immersion for 1,825 min). Surface morphology was qualitatively analyzed by scanning electron microscopy (SEM) at T 60 and T final. Roughness data were submitted to analysis of variance for mixed repeated measures, Sidak, and Tukey tests at α=0.05. Micro-filled resin showed the highest roughness values. Fluoride solutions had no influence on roughness. Higher roughness values were observed after artificial aging. In SEM observations after the artificial aging, the specimens showed surface degradation, irrespective of immersion medium or type of composite. Nano-filled resin showed higher loss of resin matrix and protrusion of filler particles. Roughness was not influenced by fluoride solutions; however, it is material dependent and increases over time.