Bonding to Beveled vs Non-Beveled Enamel at the Gingival Margin

Objectives: To compare the in–vitro microtensile enamel adhesive bond strength of three adhesives to beveled vs non-beveled gingival enamel margins of class II resin composite preparations.

Methods: After IRB approval, eleven extracted human third molars were randomly distributed into three adhesive treatment groups; (Clearfil-SE (self-etch), Excite (total-etch) and PQ1 (total-etch)). Each tooth received two class II preparations, (proximal-box depth=3.0 mm). One preparation had its gingival margin beveled and the other was not beveled. After adhesive placement two 1.5 mm increments of resin composite (Z250-3M-ESPE^TM) were added for all groups. All materials were cured with a quartz halogen light per manufacturer's instructions. Twenty-four hours later teeth were sectioned to obtain rectangular specimens (surface area ~0.5 mm²) that were tested on a Bisco microtensile tester at a crosshead speed of 2.0 mm/min. A light microscope (50x) was used to characterize the modes of failure as either adhesive or cohesive. Debonded samples were not included in the strength calculations. A separate Chi Square test analyzed debonds.

Results:

A two-way ANOVA found a statistically significant difference for bond strength between adhesives (p<0.01). A post-hoc Tukey HSD Test showed weaker bonds for Clearfil-SE vs. the other adhesives (p<0.05). Moreover, the adhesive bond strength to beveled preparations were greater than non-beveled preparations (p<0.001). In addition, there were more debonds to non-beveled preparations, (N=50, Χ²=40.72, p< 0.001).

Conclusion: Greater bond strengths were obtained with total etch adhesives compared to a self-etch adhesive. Greater bond strengths were obtained bonding to beveled gingival enamel margins in class II resin composite preparations. Funded in part by USPHS Grant K23-DE016324. purkj@umkc.edu