In Vitro Evaluation of Bond Strength of Adhesive Systems to Dentin and Stability of the Hybrid Layer
Ana Torres Muñoz, José F. Bartolomé, Carlos Oteo Calatayud, Guillermo J. Pradíes Ramiro, Óscar González‐MartínABSTRACT
Objective
Contemporary dental adhesives demonstrate strong durable adhesion to enamel while long‐term bonding stability to dentin remains uncertain. This in vitro study aimed to compare conventional dentin conditioning protocols supplemented with protease inhibition and chelate‐based conditioning protocols.
Materials and Methods
Four groups of extracted teeth were subjected to four different protocols. Groups A and B were conditioned as conventional etching techniques: in group A orthophosphoric acid 37%, chlorhexidine 0.20%, and adhesive, group B self‐etch two‐step adhesive and chlorhexidine 0.20%, followed by a composite layer. Groups C and D were treated using extrafibrillar demineralization techniques: Group C ethylenediaminetetraacetic acid (EDTA) (17%) and a self‐etch two‐step adhesive process, and Group D polyacrylic acid salt solution (225 kDa) and adhesive, followed by a composite layer. Shear bond strength tests, scanning electron microscopy evaluations, and zymography were conducted to evaluate the adhesion forces, stability and proteolytic activity of the hybrid layer before and after accelerated aging. Data were analyzed with two‐way ANOVA and Tukey tests for SBS analysis. Non‐parametric Mann–Whitney test and an Aligned Rank Transformation model were performed for the zymography analysis. The Weibull distribution test assessed each type of failure.
Results
No statistically significant differences in bond strength were observed immediately after adhesion among groups ( p ≥ 0.05). After aging, significant differences appeared ( p < 0.05). Groups A and D showed stability in bond strength. Proteolytic activity differed significantly between conventional and extrafibrillar groups both immediately and after aging ( p < 0.05). Group D showed no significant changes pre‐ or post‐aging ( p > 0.05). Group C had higher stability than groups A and B.
Conclusions
Compared with conventional conditioning protocols combined with protease inhibition, the evaluated chelate‐and‐rinse protocols showed improved maintenance of bond strength and reduced proteolytic activity over time under the conditions of this in vitro study.
Clinical Significance
The application of a novel extrafibrillar demineralization method represents a significant improvement in dentin bonding protocols, as it preserves collagen structural integrity and reduces proteolytic activity. This results in a more stable adhesive interface over time, with no loss of bond strength after aging, potentially increasing the longevity of restorations. Clinically, this strategy may enhance the predictability and durability of adhesive procedures. In the context of esthetic dentistry, improved bond stability contributes to better marginal integrity, reduced risk of discoloration and microleakage, and longer‐lasting esthetic outcomes, ultimately leading to more reliable and visually stable restorations over time and patient comfort.