Abstract
The study aimed to evaluate the quality of the hybrid layer form by three different adhesive systems. Class V cavities were prepared on the buccal surface of fourty extracted human premolars. The prepared teeth were randomly assigned into four groups according to the adhesive system and application mode. The systems were: Optibond S (OS, total-etch); Optibond Versa (OV, two-bottles, self-etch); Single Bond Universal (SBU, one-bottle, self-etch) and Single Bond Universal with etchant (SBU + etchant). All cavities were restored with composite (Filtek Z350XT). The samples were sectioned, polished and pretreated to remove minerals, protein and water prior to SEM evaluation. From the images, thickness of the hybrid layers was measured. Present of resin tags and adaptation failure were also recorded. The data obtained were analyzed using ANOVA, Dunnett’s T3, Kruskal-Wallis and Mann-Whitney tests. OS group showed the highest average hybrid layer thickness (4.34 μm), followed by SBU + etchant (3.06 μm), OV (1.91 μm) and SBU (0.95 μm). Both adhesive and cohesive failures were observed in SBU group. Present of prominent resin tags were seen in both OS and OV groups. In conclusion, all the investigated adhesive systems were able to perform distinguishable actions as shown in micro-morphological alteration and hybrid layer thickness. Two-bottles, self-etch adhesive (OV) was proven to produce negligible adaptation failure compared to other adhesive systems in the present study. Combined all-in-one adhesive (SBU) was found to render a superior bonding performance in total-etch mode comparing to self-etch mode.
Highlights
In the past four decades, adhesive dentistry has revolutionized restorative dental practice with the progressive improvement in adhesive materials
Total-etch adhesives (OS, Group 1) showed a significantly greater hybrid layer thickness compared to self-etching adhesive systems (OV and SBU)(Table 2), This observation was in agreement with previous similar studies [24,25] and could be due to the complete dissolution of the smear layer and smear plug following greater depth of dentine demineralization promoted by the 37.5% phosphoric acid [25]
Resin tags were detected in all the adhesive systems except in SBU
Summary
In the past four decades, adhesive dentistry has revolutionized restorative dental practice with the progressive improvement in adhesive materials. The acid etchant completely removed the smear layer and smear plugs which allows capillary penetration of adhesives into the etched enamel surfaces to form resin tags. Bonding of resin to dentine was proven to be more complicated than bonding to enamel [3]. This is due to the complex morphology and chemical composition of the dentine, with respect to its moisture and high organic content. The interface between the dentine and adhesive is called ‘hybrid layer’. This layer was first described by Nakabayashi [6] in order to explain the phenomenon of dentine bonding
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