Resumo Este estudo avaliou o impacto de suco de laranja na resistência de união (RU) de sistemas adesivos dentinários (SAD) à superfície do esmalte após a simulação com uma ciclagem erosiva in situ/ex vivo. Cento e noventa e dois fragmentos de esmalte bovino (4x4x2mm) foram obtidos e randomizados considerando a microdureza superficial, e distribuídos em dispositivos palatinos para 8 voluntários, em três fases (uma para cada SAD), contendo 8 blocos, os quais foram alocados em 4 pares. Diariamente, esses pares eram submetidos às seguintes condições extraoralmente: CONT- sem desafio erosivo ou abrasivo; ERO- desafio erosivo somente; ABR- desafio abrasivo somente; e ERO+ABR- com desafio erosivo e abrasivo. A ciclagem erosiva (imersão em suco de laranja, 3 vezes/dia/5 min/5 dias) e/ou ciclagem abrasiva (escova dentária elétrica, 3 vezes/dia/1 min/5 dias) foram feitas. Após estas ciclagens, todos os espécimes foram restaurados com os sistemas adesivos Adper Scotchbond Multi Purpose (MP), Adper Single Bond 2 (SB) ou Clearfil SE Bond (SE), e com a resina composta Filtek Z250. Após 7 dias, palitos (área ≈1 mm) eram obtidos e submetidos ao teste de resistência de união por microtração (μTBS) a 0,5 mm/min. Os dados foram estatisticamente analisados por ANOVA e teste de Tukey (a=0,05). Os modos de fratura foram determinados utilizando um microscópio digital (40×). SAD foi o único fator estatisticamente significante. SE foi o único SAD não afetado por qualquer desafio, enquanto o MP e o SB apresentaram um desempenho de acordo com o cenário. As fraturas do tipo mista e adesiva foram predominantes em todos os grupos. O desempenho geral sugeriu que RU ao esmalte após desafio erosivo/abrasivo por suco de laranja não foi afetada e foi material-dependente.

Abstract This study evaluated the impact of orange juice on the bond strength (BS) of dentin bonding systems (DBSs) to enamel surface after simulation with an in situ/ ex vivo erosive cycling. One hundred and ninety two bovine enamel fragments (4x4x2mm) were obtained and randomized regarding superficial microhardness and distributed to palatal devices for 8 volunteers, in three phases (one for each DBS), containing 8 blocks, which were, allocated in 4 pairs. Daily, these pairs were subjected extraorally to the following conditions: CONT- neither erosive nor abrasive challenge; ERO- erosive challenge only; ABR- abrasive challenge only and ERO + ABR- with erosive and abrasive challenges. Erosive cycles (immersion in orange juice, 3 times/day/5 min/5 days) or/and abrasive challenges (electric toothbrush, 3 times/day/1 min/5 days) were performed. After these cycles, all specimens were restored with the adhesive systems Adper Scotchbond Multi Purpose (MP), Adper Single Bond 2 (SB) or Clearfil SE Bond (SE), and the composite resin Filtek Z250. After 7 days, sticks (area ≅1 mm2) were obtained and subjected to the microtensile bond strength test (μTBS) at 0.5 mm/min. Data was statistically analyzed by ANOVA and Tukey tests (a=0.05). Failure modes were determined using a digital microscope (40´). DBS was the only statistical significant factor. SE was the unique DBS not affected in any challenge, whereas MP and SB performed according to the scenario. The adhesive and mixed failures were predominant in all groups. Overall performance suggested that BS to enamel after erosive /abrasive challenged by orange juice was not affected and it was material-dependent.

Concern has been raised about the bonding of restorative procedures to an erosive lesion, given the change in organic and inorganic composition and structure of this substrate. This in vitro study evaluated the effect of erosive drinks and an enzyme inhibitor (2% chlorhexidine digluconate – 2% CHX) on bond strength to dentin. Sixty sound human third molars were selected, and the occlusal enamel was flattened, exposing the dentin surface. The specimens were randomly divided into three groups: AS-Artificial saliva (control group), RC- Regular Cola and ZC- Zero Cola. Twenty specimens were immersed in their respective solution for 1 minute, 3 times a day, over the course of 5 days. After acid etching and before bonding with Adper Single Bond 2, half of the samples of each group (n = 10) were treated with 2% CHX, whereas the other half (n = 10) were not, forming the control group (CONV). All the specimens were restored with Filtek Z250 composite resin filled in Tygon tubes (0.48 mm2), yielding six microcylinders for microshear bond strength testing. Three composite resin microcylinders of each specimen were tested after 1 month, and the remaining microcylinders were tested after 6 months. Failure modes were determined using a stereomicroscope (40x). The data were statistically analyzed by three-way ANOVA and Tukey tests (α = 0.05). Overall bonding was reduced after 6 months, regardless of treatment. The 2% CHX enhanced bond strength after 1 month only in the ZC group, and did not enhance bonding performance to demineralized dentin by erosive protocol after 6 months in any group.