SEM-EDS nanoleakage evaluation of universal-adhesive-systems with etch-and-rinse and self-etch approach

Abstract

Introduction: For adhesive systems to be considered efficient they should maintain restorations stable and with adherence. They also should be capable to seal restorations margins against oral fluids and microorganisms for a long period [1,2]. Adhesive interface permeability to water and other oral fluids is possible even in restorations without detectable pores since their entry can be done through nanometric defects [2,3]. This adhesive interface degradation by hydrolysis can negatively affect adhesion durability leading to an adhesive interface degradation, process that Sano in 1995, called nanoleakage [4,5]. The aim of this study was the nanoleakage evaluation of universal adhesive systems, by SEM-EDS with Etch-and-rinse and Self-Etch approach.

Materials and methods: This work was approved by the IUEM Ethics Committee. 24 intact human molars extracted for orthodontic or periodontal reasons were randomly divided into 12 groups (n = 2), 6 control and 6 experimental. Three universal adhesive systems, Futurabond® U, Prime & Bond^® Active™ and Scotchbond™ Universal, were tested in their etch-and-rinse and self-etch approaches. Teeth were cut in a hard tissues microtome to expose superficial dentin and were polished with a 400 grit SiC paper. Adhesives were applied according to manufacturer’s instructions and resin build-ups were obtained with Filtek Z250 resin (colour A2) with 2 mm increments up to a maximum of 6–8 mm. Samples were sectioned in the X direction on a hard tissue microtome in order to obtain slices of 0.7 mm. 10 slices were selected for each group. In the control groups samples were stored in 5 ml of oil (VV Lubricant) for 3 months in an oven at 37 °C in order to avoid the hydrolytic degradation process and the experimental groups were stored in 5 ml of deionized water for 3 months in an oven at 37 °C so that it was possible to observe the hydrolytic degradation. After the incubation period samples were prepared and subjected to SEM-EDS nanoleakage tests. Statistical analyses with a Mixed Linear Model (MM), with Akaike (AIC), Hurvich andTsai (AICC), Bozdogan (CAIC) and the Bayes and Schwarz (BIC) information criteria were done.

Results: No significant differences were found between universal adhesives. However, there was a significant difference concerning the adhesion strategy. The previous acid conditioning caused a greater expression of the nanoleakage.

Discussion and conclusions: In our study we verify that when universal adhesives were applied with the etch-and-rinse approach the adhesive interface percentage infiltrated with silver nitrate is significantly higher that when adhesives were applied in the self-etch approach. These results are in accordance with other studies found in literature. Marchesi et al. [6] observed that nanoinfiltration was significantly reduced when Scotchbond Universal adhesive was applied as self-etch. In another study Luque-Martinez et al. [7] studied three universal adhesives: Scotchbond Universal, All-Bond Universal e Prime&Bond Elect and found that all presented significantly higher nanoinfiltration when applied as etch & rinse. The same results were found by Muñoz et al. [8] for the All-Bond Universal and G-Bond adhesives. The self-etch application of these universal adhesives seemed to contribute to the stability and durability of the adhesive interface.