Influence of Erosive and Abrasive Cycling on Bonding of Different Adhesive Systems to Enamel: An In situ Study

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.

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.

Bond strength of a resin composite and a resin-modified glass-ionomer cement associated or not with chlorhexidine to eroded dentin / Resistência de união de uma resina composta e um cimento de ionômero de vidro modificado por resina com e sem a aplicação de clorexidina à dentina erodida

Objetivo: Apesar da resina composta e o cimento de ionômero de vidro serem amplamente usados para restaurações cervicais, sob condições erosivas estas podem desgastar mais rapidamente. Este estudo objetivou comparar a resistência adesiva ao microcisalhamento de uma resistência de união (RC) e um cimento de ionômero de vidro modificado por resina (RMGIC) à dentina erodida associada à Clorexidina 2% num período de até 6 meses. Material e Métodos: Oitenta terceiros molares humanos foram cortados e uma dentina regular foi obtida, e subsequentemente, foram inclusos com resina acrílica em tubos de PVC. Os dentes foram divididos em dois grupos, de acordo com o tratamento recebido: Adper Single Bond 2 + RC Filtek Z250 (Z) ou RMGIC Vitremer (V). Metade dos corpos de prova foram imersos em saliva artificial (AS) por 24 h (grupo controle) e metade foi erodido artificialmente 3x/1 min diariamente com Coca Cola ®-RC por 5 dias. Metade dos corpos de prova, para cada condição descrita, recebeu água e outra metade a clorexidina 2% por 1 min, antes da restauração. Para todos os grupos, os corpos de prova foram armazenados em saliva artificial renovada semanalmente até os testes. A resistência de união ao microcisalhamento foi avaliado após 1 e 6 meses. Os resultados foram analisados com teste ANOVA 4 critérios e Tukey (p < 0,05). Resultados: Os fatores materiais, substrato e tempo foram estatisticamente significantes, além da interação entre o material e o tempo. O tratamento (água X clorexidina) não foi um fator significante. As restaurações com Z demonstraram resistência de união significantemente maior comparada ao V, em todas as situações. Conclusão: Tanto para a dentina sadia quanto erodida, a resina composta apresentou maior resistência de união comparada ao cimento de ionômero de vidro. O tempo e uso da clorexidina não interferiu na resistência de união. A resina composta demonstrou maior resistência adesiva quando comparada ao cimento de ionomero de vidro.

Objective: Although resin composites and glassionomer cements are widely used for dental cervical region restorations, under erosive condition they can wear out quickly. This study aimed to compare, by means of microshear bond strength, the performance of a resin composite (RC) and a resin-modified glassionomer cement (RMGIC) to eroded dentin and its association with 2% chlorhexidine (CHX) up to 6 months. Material and Methods: Eighty sound third molars teeth were cut to obtain flat coronal dentin, which were subsequently embedded in self-curing acrylic resin circular molds. Teeth were divided into two groups, according to the treatment with the Adper Single Bond 2 + RC Filtek Z250 (Z) or the RMGIC Vitremer (V). Half of the specimens were immersed in artificial saliva-AS (control groups) and half subjected to 3x/1 min daily immersion in Regular Coca Cola ®-RC for 5 days. Half of the specimens for each described condition were treated with water and half with 2% chlorhexidine for 1 min prior the restoration. For all groups, the specimens were stored in artificial saliva weekly renewed up to tests. The microshear bond strength was evaluated after 1 month and 6 months. Data, in normal distribution, were analyzed with four-way ANOVA and Tukey (p < 0.05). Results: The factors materials, substrate and time were statistically significant and also the interaction between material and time. Treatment (water x CHX) was not a significant factor. Restorations with Z showed significantly higher bond strength compared to V in all situations. There was a reduction in bond strength values over time for all tested conditions. Conclusion: For both sound and eroded dentin, the resin composite presented higher bond strength compared to resin-modified glassionomer material. The bond strength performance was overall reduced with time and the use of chlorexidine itself did not interfere on bond strength through time...

How erosive drinks and enzyme inhibitors impact bond strength to dentin

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.