The influence of different etching modes and etching time periods on micro-shear bond strength of multi-mode universal adhesives on dentin

Introduction
Simplifying single-bottle adhesive technology to satisfy clinicians’ demand for adhesive procedures, particularly in terms of making the techniques faster, less technically sensitive, and more user friendly, has led to the development of multi-mode universal adhesives, which were designed to bind to tooth structures via the etch-and-rinse, the self-etch, and the selective-etch modes using a single bottle of adhesive solution.

Objectives
The aim of this study was to determine the dentin bonding ability of multi-mode universal adhesive systems in relation to different etching modes and etching time periods using micro-shear bond strength analysis.

Material and methods
Three multi-mode universal adhesives and one etch-and-rinse adhesive were assessed in this study. Micro-shear bond strengths (μSBS) to dentin were obtained in etch-and-rinse (etching 5 s/10 s/15 s) and self-etch modes. For each test condition, 10 specimens were prepared for each group. A scanning electron microscope (SEM) was used to examine representative bonded specimens, treated dentin surfaces, and the resin/dentin interface for each test condition.

Results
Multi-mode universal adhesives showed the lowest μSBS results in etch-and-rinse mode for 10-s and 15-s etching (p < 0.05). Universal adhesives and self-etch adhesives showed similar μSBS values in self-etch mode (p > 0.05).

Conclusions
Analysis concluded that phosphoric-acid etching for time periods greater than 5 s significantly reduced the efficacy of bonds when using multi-mode universal adhesives.