Influência da remoção do colágeno e do uso de oxalato de potássio na resistência de união de adesivos simplificados à dentina

Abstract

The aim of this in vitro study was to evaluate two adhesive systems: XP Bond (Dentsply) and Prime & Bond NT (Dentsply), applied on human tooth dentine with previous application of sodium hypochlorite (NaOCl) 10% and potassium oxalate (BisBlock - Bisco), by means of test of microtensile bond strength (µTBS), and standard of fracture analysis through optical microscope (OM). Thirty two non-carious human third molars were selected and had its oclusal enamel removed to produce flat dentin surface which was prepared using sandpapers (SiC) of granulation 600 through a politriz with the intention of standardize the smear layer. After that the teeth were divided in 8 groups: G1 (XP) - XP Bond; G2 (XPH) – 10% sodium hypochlorite + XP Bond; G3 (XPO) - potassium oxalate + XP Bond; G4 (XPHO) – 10% sodium hypochlorite + potassium oxalate + XP Bond; G5 (PB) - Prime & Bond NT; G6 (PBH) – 10% sodium hypochlorite + Prime & Bond NT; G7 (PBO) – potassium oxalate + Prime & Bond NT, e G8 (PBHO) – 10% sodium hypochlorite + potassium oxalate + Prime & Bond NT. After the treatments had been performed, crowns with resin composite Esthet X (Dentsply), color A-2 were built. These crowns were done through increments of 2 mm of thickness, with photo polymerization of 20 s for increment, until reaching 6 mm of height. The samples then had been parted for the attainment of beams with transversal section of 0.8 mm, to be performed under µTBS. The mechanical assay was carried through a machine of universal assay. The beams used in the microtensile test had been used later for the analysis of the standard of breaking through an OM. The results gotten in µTBS, Means(SD), were: XP – 35.225(15.470)Aa, XPH – 23.405(12.425)Ba, XPO – 15.492(9.168)Cb, XPHO – 16.389(11.108)Cb, PB – 27.589(11.265)Ab, PBH – 25.457(12.044)Aa, PBO – 31.631(14.391)Aa and PBHO – 26.263(8.912)Aa. After the values had been submitted to the statistical analysis (Kruskal-Wallis, Dunn e Mann-Whitney, α=0.05), was verified that XP Bond had better bond strength than Prime & Bond NT (control groups), and the 10% NaOCl treatment and potassium oxalate usage had decreased the bond strength of XP Bond and did not cause any statistical interference on Prime & Bond NT, even its usage was either together or isolated. The microscopic analysis of the breaking standard showed that almost all os specimens had adhesive fractures.