Short dentin etching with universal adhesives: effect on bond strength and gingival margin adaptation.

Background: Short dentin etching, a relatively recent technique, aims to improve resin-dentin bonding by preserving hydroxyapatite crystals within the collagen spaces. This study explores short dentin etching's potential in mitigating over-etching issues in deep proximal dentin/cementum margins, an aspect not previously investigated. This study evaluates the microtensile bond strength (μTBS) and marginal adaptation of two universal adhesives using different etch-and-rinse strategies (15-second and 3-second etching) and self-etch strategies, both immediate and post-thermal cycling and mechanical loading.

Methods: Eighty-four molars underwent μTBS testing, categorized by the universal adhesive type (Tetric Uni and Prime&Bond Uni) (n = 42) and adhesive strategy (n = 14) with half tested after 24 h and the rest post aging. Forty-two molars received occluso-mesial preparations with proximal margins in dentin/cementum and were restored accordingly. Scanning electron microscope (SEM) examination of epoxy replicas for the restoration/gingival dentin interfaces was conducted after 24 h and aging. Dentin etching patterns were assessed using SEM. A three-way ANOVA evaluated μTBS data, while a two-way ANOVA and paired sample t-test analyzed marginal adaptation data (significance level is α = 0.05).

Results: Adhesive type, strategy, and aging significantly influenced μTBS. After aging, Tetric Uni subgroups displayed higher bond strength compared to Prime&Bond Uni subgroups. Marginal adaptation was unaffected by adhesive type or strategy, although aging reduced bond strength and adaptation for both adhesives.

Conclusions: The etch-and-rinse protocol yielded higher μTBS results for the HEMA-free isopropanol-based adhesive (Prime&Bond Uni). Marginal integrity was similar for both adhesives. The 3-second and 15-second etching times produced consistent results in all tests and for both adhesives.

Clinical significance: The adhesive protocol for bonding universal adhesives to dentin is contingent on the adhesive composition.