AVALIAÇÃO IN VITRO DA PERMUTA QUÍMICA ENTRE RESTAURAÇÃO DE CIMENTO DE IONÔMERO DE VIDRO E DENTINA DECÍDUA PARCIALMENTE DESMINERALIZADA TRATADA COM NAF A 2%

Abstract

This in vitro study evaluated the effect of pretreatment action of a neutral solution of sodium fluoride (NaF) 2% and a glass ionomer cement (GIC) of high viscosity (Ketac Molar Easymix ®) in primary sound dentin and demineralised dentin, with Knoop hardness test, Energy Dispersive Spectroscopy (EDS) and micro-Raman. In 40 primary molars class I cavities were created, these teeth being divided into groups 1 and 2 (pH cycling) and groups A and B (NaF). After pH cycling (n = 20) the cavity half was isolated with nail varnish, obtaining two sites, one in direct contact with the GIC and other control. The cavities of 20 teeth (G1B, G2B) received topical fluoride application before restoring. The G1A, G1B, G2A and G2B groups were formed. The restored teeth were sliced (n=3) in mesiodistally for testing the hardness and mineral exchange. The hardness data were analyzed using paired t-test, and the contact areas (C) and non-contact (SC) and ANOVA 2 criteria considering factors dentin (sound and demineralised), treatment (with and without fluoride) and interaction (and treating dentin). The level of significance used was 5% (α = 0.05). The data EDS and micro-Raman spectra were analyzed qualitatively by groups. Significant difference was found between the Knoop hardness factor for dentin (sound and demineralised) and in the contact area of the restorative material (p <0.0001). The gain in G1A dentin hardness was 63 to 79 KHN, G1B of 68 to 80 KHN, from 34 to 51 KHN G2A and G2B KHN 33 to 53 KHN. Changes in hardness occurred by direct contact of the restorative material with dentin surface in both conditions (dentin and treatment). The treatment factor not reflected in a significant difference for the factor dentin in both areas without contact (p=0.358) and contact (p=0.642). The interaction between factors and dentin treatment did not affect significant change in the hardness of dentin, with no significant difference in both the non-contact area (p=0.309) and contact (p=0.751). The results G1A and G2A groups showed increased hardness of dentin, with 21% sound dentin and 33% in demineralised dentine. In groups G1B and G2B, pretreatment with NaF was not effective and gain hardness of 15% in sound dentin and 36% demineralised dentin was related to contact with the GIC. The demineralised dentin was the most reactive substrate. Mineral evaluation EDS, contact with the GIC determined in a sound dentin increase of calcium and fluoride in demineralised dentin. In the evaluation of micro-Raman, direct contact with the restorative material in dentin (sound and demineralised dentin) reflected in increased peak phosphate, represented by calcium hydroxyapatite. Ionic exchanges between GIC and demineralised dentin determine improvement in the quality of this substrate without pretreatment with NaF.