FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / O objetivo deste estudo in vitro foi avaliar a resistÃncia de uniÃo atravÃs de teste de microtraÃÃo (RUÂT) e a observaÃÃo do padrÃo de fratura atravÃs de anÃlise com microscÃpio Ãtico (MO) de dois sistemas adesivos: XP Bond (Dentsply) e Prime & Bond NT (Dentsply), aplicados sobre dentina de dentes humanos com aplicaÃÃo prÃvia de hipoclorito de sÃdio (NaOCl) a 10% e oxalato monopotÃssio mono-hidrogenado 3% (BisBlock - Bisco). Trinta e dois terceiros molares humanos hÃgidos recÃm extraÃdos tiveram suas coroas seccionadas no terÃo oclusal, prÃximo à junÃÃo amelo-dentinÃria, onde a dentina foi exposta e planificada usando lixas de SiC de granulaÃÃo 600 atravÃs de uma politriz giratÃria refrigerada a Ãgua. Posteriormente os dentes foram separados aleatoriamente em 8 grupos a saber: G1 (XP) - XP Bond; G2 (XPH) â NaOCl 10% + XP Bond; G3 (XPO) - oxalato de potÃssio + XP Bond; G4 (XPHO) â NaOCl 10% + oxalato de potÃssio + XP Bond; G5 (PB) Prime & Bond NT; G6 (PBH) â NaOCl 10% + Prime & Bond NT; G7 (PBO) - oxalato de potÃssio + Prime & Bond NT, e G8 (PBHO) â NaOCl 10% + oxalato de potÃssio + Prime & Bond NT. ApÃs a aplicaÃÃo dos tratamentos, foram confeccionadas coroas com compÃsitos Esthet X (Dentsply), cor A-2. Essas coroas foram confeccionadas atravÃs de incrementos de 2 mm de espessura, com fotoativaÃÃo de 20 s por incremento, atà atingirem 6 mm de altura. Os dentes foram submetidos a ensaio de microtraÃÃo e anÃlise do padrÃo de fratura foi realizada atravÃs de MO. As fraturas foram classificadas como: adesiva, coesiva e mista. Os resultados obtidos, MÃdia(DP) no ensaio de microtraÃÃo (RUÂT) foram: XP â 35,225(15,470)Aa, XPH â 23,405(12,425)Ba, XPO â 15,492(9,168)Cb, XPHO â 16,389(11,108)Cb, PB â 27,589(11,265)Ab, PBH â 25,457(12,044)Aa, PBO â 31,631(14,391)Aa e PBHO â 26,263(8,912)Aa. ApÃs anÃlise estatÃstica (Kruskal-Wallis, Dunn e Mann-Whitney, α=0,05), verificou-se que o adesivo XP Bond apresentou maior resistÃncia de uniÃo (RU) que o Prime & Bond NT; O uso de NaOCl 10% e oxalato de potÃssio interferem negativamente no XP Bond e nÃo causaram alteraÃÃes na RU do Prime & Bond NT quando aplicados tanto conjuntamente como isolados. A anÃlise microscÃpica do padrÃo de fratura mostrou que a maioria dos espÃcimes fraturou na interface adesiva. / 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 (ÂTBS), 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) â 10% sodium hypochlorite + XP Bond; G3 (XPO) - potassium oxalate + XP Bond; G4 (XPHO) â 10% sodium hypochlorite + potassium oxalate + XP Bond; G5 (PB) - Prime & Bond NT; G6 (PBH) â 10% sodium hypochlorite + Prime & Bond NT; G7 (PBO) â potassium oxalate + Prime & Bond NT, e G8 (PBHO) â 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 ÂTBS. 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 ÂTBS, Means(SD), were: XP â 35.225(15.470)Aa, XPH â 23.405(12.425)Ba, XPO â 15.492(9.168)Cb, XPHO â 16.389(11.108)Cb, PB â 27.589(11.265)Ab, PBH â 25.457(12.044)Aa, PBO â 31.631(14.391)Aa and PBHO â 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.