In vitro evaluation of micro-leakage of a universal adhesive used with different etching modes in compomer restorations

Introduction
In order to obtain a good prognosis in resin restorations, a strong adhesion not allowing leakage between tooth tissues and restoration should be provided. Effectiveness of universal adhesives on leakage in primary teeth compomer restorations has not been studied.

Objectives: The objective of this study was to evaluate sealing ability of a universal adhesive used with different etching modes after 1- and 3-year of artificial aging in compomer restorations of primary teeth.

Material and methods
Sixty-three extracted mandibular primary second molars were used in the study. Class II box cavities (3 mm × 3 mm × 1.5 mm) were prepared in each tooth. Then, teeth were divided into three groups (n = 21), including total-etch, self-etch, and selective-etch modes. All teeth were restored with compomer (Dyract Extra, Dentsply; Konstanz, Germany) after universal adhesive (Prime & Bond Elect Universal, Denstsply; Milford, USA) application. Teeth were divided into three sub-groups (n = 7) with the following three different aging protocols: 24 h water storage, 1-year aging, and 3-year aging with chewing simulator (Esetron Chewing Simulator; Ankara, Turkey). 50% silver nitrate solution was applied as a tracer, and its’ penetration was analyzed in mm3 using micro-computed tomography system (SkyScan 1275; Kontich, Belgium). Data was analyzed with Kruskal-Wallis H and Friedman tests.

Results
One-year aging significantly increased the leakage in self-etch group of samples (0.197 ± 0.49 mm3) compared to the total-etch (0.001 ± 0.000 mm3) and selective-etch (0.001 ± 0.000 mm3) groups (p < 0.05). There was no difference between the groups at baseline and after the 3-year artificial aging (p > 0.05).

Conclusions
Self-etch mode of adhesive revealed higher micro-leakage levels at all examination intervals; however, the difference was only significant after the 1-year aging. It can be concluded that universal adhesives can be used with all etching modes in compomer restorations.