Effect of Different Adhesive Application Approaches on Bond Strength in Over-Etched Dentin

Phoebe Burrer^a*(phoebe.burrer@zzm.uzh.ch) | Shpresa Simoni^a | Paula Zwicky^a | Thomas Attin^a | Tobias T. Tauböck^a

^aClinic of Conservative and Preventive Dentistry, Center for Dental Medicine, University of Zürich, Zürich, Switzerland

Objectives: To investigate the effect of over-etching and subsequent use of different adhesive application approaches including active, double, preheated, and ultrasonic application on dentin bond strength.

Methods: Dentin specimens from sound human third molars were prepared and allocated into six groups (n = 10 per group). In group 1 (negative control), the dentin specimens were over-etched with phosphoric acid for 30 s, and a two-step etch-and-rinse adhesive (Prime & Bond XP; Dentsply Sirona) was applied for 20 s according to the manufacturer's instructions. In test groups 2–5, the application of the adhesive varied: In group 2, the adhesive was actively rubbed into the dentin surface, whereas in group 3, a second adhesive layer was applied after light-curing of the first one. In group 4, the adhesive was heated to 68°C prior to application, and in group 5, the adhesive was ultrasonically activated. Acid- etching for 15 s and adhesive application for 20 s was performed in the positive control group (group 6) according to the manufacturer's instructions. After light-curing and composite build-up (Ceram.x Spectra ST (HV); Dentsply Sirona), microtensile bond strength and fracture types were determined. Data were statistically analyzed by Kruskal-Wallis rank test, followed by post-hoc pairwise comparisons using Conover tests and p-value adjustment according to Holm (α = 0.05).

Results: Active, double, preheated, or ultrasonic adhesive application showed no significant effect on dentin bond strength when compared to the control groups. Predominantly adhesive adhesive failures were observed in all groups.

Conclusion: A modification of adhesive application by using active, double, preheated, or ultrasonic application does not improve bonding to accidentally over-etched dentin.

Funding/Conflict of Interest: The authors declare that they have no conflict of interest.

Keywords: adhesion, microtensile bond strength, phosphoric acid etching, preheating, ultrasonic-assisted application

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