No abstract

As denture cleansers should be able to reduce biofilm accumulation without changing the acrylic resin surface structure, this study evaluated the effect of denture cleansers on surface roughness of acrylic resin and on biofilm accumulation. It was conducted a crossover study of three phases of 4 days each and 13 volunteers wore palatal appliances containing four specimens of acrylic resin of known surface roughness which were extra-orally submitted once a day to three groups of separated treatments: (i) negative control, (ii) enzymatic commercial solution (Ortoform) or (iii) 0.5% sodium hypochlorite (NaOCl). The appliances were immersed eight times a day in a 20% sucrose solution to enhance biofilm formation. On morning of the fifth day of each phase, the amount of biofilm formed on the specimens was estimated by the amount of protein extracted with alkali and the surface roughness of the specimens was again measured. New palatal appliances with new specimens were worn by the volunteers in the following phases, but the treatments were changed. The roughness of the resin increased after the treatments (P < 0.05) but the difference among the cleansers was not statistically significant (P = 0.85). The lowest amount of biofilm formed on acrylic resin specimens was found for the treatment with NaOCl (P < 0.05) but the enzymatic product did not differ from the negative control group (P > 0.05). The data suggest that the roughness of acrylic resin was not changed by the cleansers, but the ability to reduce biofilm accumulation depended on the product used.

Extracted human teeth are frequently used for research or educational purposes. Therefore, it is necessary to store them in disinfectant solutions that do not alter dental structures. Thus, this study evaluated the influence of storage solution on enamel demineralization. For that purpose, sixty samples were divided into the following groups: enamel stored in formaldehyde (F1), stored in thymol (T1), stored in formaldehyde and submitted to pH cycling (F2), stored in thymol and submitted to pH cycling (T2). All samples were evaluated by cross-sectional microhardness analysis and had their percentage of mineral volume versus micrometer (integrated area) determined. Differences between groups were found up to 30-µm depth from the enamel surface (p < 0.05), where samples from group T2 were more demineralized. It was concluded that the storage solution influenced the reaction of a dental substrate to a cariogenic challenge, suggesting that formaldehyde may increase enamel resistance to demineralization, when compared to demineralization occurring in enamel stored in thymol solution.

The aim of this study was to evaluate surface free energy (SFE), surface roughness (SR) and surface hardness (SH) of two commercially available materials for fabricating dental implant abutments. In addition, the specimens were investigated by scanning electron microscopy (SEM) to determine the surface morphology. Twenty five discs (5 x 2 mm) of Ti-6Al-4V and Tilite (Ni-Cr-Ti) alloys were used in this study. Surface free energy was determined by the contact angle formed between a drop of distilled, deionized water and the surface of the specimen of each material. The surface roughness was measured with a mechanical profilometer and the surface hardness was evaluated by means of the Vickers hardness micro indentation test. SFE, SR and SH data were analyzed using one-way ANOVA (p < 0.05). Statistical differences (p < 0.05) were found between Ti-6Al-4V (36.2 erg x cm(-2); 0.2 microm) and Tilite (30.9 erg x cm(-2); 0.16 microm) for SFE and SR. However, the differences between the surface hardness values of Ti-6Al-4V (325.0 kg/mm(2)) and Tilite (324.3 kg/mm(2)) were not statistically significant (p > 0.05). Evaluations by SEM revealed different surface morphology. Within the limits of this study, it can be concluded that the Ti-6Al-4V and Tilite alloys showed differences in surface properties, except for surface hardness, suggesting that both alloys may be considered appropriate for producing abutments. Further studies are, however, necessary to elucidate the biological responses to implant abutments made with these alloys.