Influence of different beverages on the microhardness and surface roughness of resin composites

This study assessed the influence of different beverages on the microhardness and surface roughness of microfilled (A110, 3M/ESPE), hybrid (Z250 3M/ESPE) and flowable (Flow, 3M/ESPE) resin composites, over time. Twenty-four disc-shaped specimens (10 mm; 2-mm thick) of each resin composite were fabricated, thereby forming three groups (n=24). Knoop microhardness and surface roughness (Ra) were analyzed at predetermined evaluation periods: 24 hours, and 7, 30 and 60 days after specimens fabrication. The 24-hour measurements were recorded after storage in artificial saliva. Next, each group (n=24) was divided into four subgroups (n=6) according to the test beverages: Coca-Cola, sugar cane spirit, coffee and artificial saliva (control). Control specimens were kept in saliva throughout the experiment (60 days). For experimental specimens, a 60-day testing cycle was carried out: specimens were initially stored in saliva for four hours, then submitted to a five-minute immersion in the beverages (Coca-Cola, sugar cane spirit, coffee) intercalated by immersions in saliva three times daily. Microhardness/roughness measurements were done at 7-, 30- and 60-day intervals. Data were submitted to three-way ANOVA and Scheffée test (p<0.05). It was observed that the tested beverages somewhat altered (p<0.05) the composites' microhardness and/or surface roughness. Knoop microhardness-for all resin composites, microhardness remained stable up to the 30-day record, decreasing significantly at the 60-day evaluation. During the interaction beverage X evaluation period, it was observed that the microhardness of materials immersed in coffee and Coca-Cola remained stable up to the seven-day measurement, showing a decrease at the 30-day record and a more accentuated drop at the 60-day evaluation (p<0.05). Specimens immersed in sugar cane spirit exhibited no significant change in microhardness up to the seven-day measurement, increasing significantly at the 30-day record and later decreasing at the 60-day evaluation. Surface Roughness--For all resin composites, surface roughness increased at the seven-day measurement, while decreasing at the 30-day record and even more at the 60-day record. In the interaction beverage X evaluation period, the surface roughness of specimens immersed in test beverages increased at the seven-day measurement, showing a gradual decrease at the following records (30- and 60-day evaluations). The findings of the reported research disclosed that all beverages altered, to some degree, the microhardness and/or surface roughness of the tested resin composites. The alterations' effects ranged from slightly adverse to a markedly negative impact on the composites' microhardness and surface roughness, depending on the characteristics of the materials, type of beverage and the evaluated period. Generally, the greater number of immersions in beverages resulted in a more accentuated impact on the resins' properties.