REEMBASADORES RESILIENTES PARA BASE DE PRÓTESE: RUGOSIDADE SUPERFICIAL E ANÁLISE HISTOPATOLÓGICA EM MODELO ANIMAL

Abstract

The aim of this study was to evaluate in vivo the effect of a post-polymerization heat treatment in the biocompatibility of resilient denture base liners, and to investigate the changes on their surface roughness after 14 days of use in animals. Fifty adult rats (Wistar, females), aged sixty days, and body mass of 150g - 200g were divided in five groups according to the materials tested: one group used an acrylic plate made with Lucitone 550 (G2), and five groups tested received one of the following lining materials on the Lucitone 550 plates: Dentusoft (G3), Dentuflex (G4) or Trusoft (G5) and Ufigel P (G6); and one control group (G1) was kept without plates in the same conditions. For the groups G2, G3, G4 and G5 were used 10 rats, when half of the animals from each group (n=5) used plates with no post-polymerization (NT), and the other half received a heat water-bath post-polymerization (HT) before insertion. After 14 days the animals were killed and the palates were fixed in 10% buffered formalin. Sections of 5 μm, stained with hematoxylin and eosin, were analyzed by computerized planimetry to quantitatively assess the keratin layer thickness (KC), the total epithelium thickness (ET) and the basal layer interface lenght (BL). Surface roughness (Ra) of the relined dentures materials tested was recorded immediately after reline (IRa groups) or 14 days after fixing the palatal plates on animals (FRa groups), for the groups G3, G4, G5 and G6. Normality of residuals and homogeneity of the variances were examined by Shapiro-Wilk and Levene’s tests, respectively. ANOVA and Tukey’s test were used to the morpho- histometric data. Animal weight initially and after 14 days were compared using Wilcoxon signed rank sum test. Post hoc power analysis was performed for the Ra data (μm) and analyzed by 2-way ANOVA and Tukey’s test. All the statistical inferences for the histological quantitative analyses and surface roughness were performed assuming a 5% significance level. For NT, there were no statistical differences for the tissue parameters among the groups G2, G3, G4 and G5, nor either when comparing each one with G1 (p ≥ 0.05). For HT, G4 showed less elongated ridges at the basal membrane interface (p = 0.037) than G2. When comparing NT and HT, G2 showed a significant decrease in the KC and ET (p < 0.05). IRa means (2.92 ± 0.87 μm) and FRa means (3.35 ± 0.65 μm) were significantly different (P = 0.016). Ufi Gel showed a lower (p = 0.01) Ra mean (2.1 ± 0.52 μm) than Dentuflex (3.94 ± 0.81 μm), Trusoft (4.12 ± 0.64 μm) and Dentusoft (3.27 ± 0.64 μm). Trusoft was rougher than Dentusoft (p > 0.05). The post-polymerization heat treatment for Lucitone 550 was an effective method to reduce the morpho-histometric changes in the rat palatal mucosa. By means of quantitative data, in this study the resilient chairside lining materials tested did not cause significant histopathologic changes in the rat palatal mucosa for the tested period. Dentuflex, Trusoft and Dentusoft showed greater changes in their surface roughness after 14 days when compared to Ufi Gel P. The period of 14 days in vivo resulted in changes in the surface roughness of the materials tested.