Comparison of Dentin Bond Strength Using Conventional Adhesive Application and Co-curing Technique

Objectives: To evaluate shear bond strength (ISO 29022) of a flowable bulk-fill composite resin bonded to dentin using two different adhesive systems which were cured either separately or simultaneously with the composite specimen.

Methods: Dentin substrates for shear bond strength testing were prepared from intact third molars, embedded in an acrylic resin and wet-polished using P600 silicon carbide paper.
Resin composite cylinders were bonded onto dentin substrates using Excite F (Ivoclar Vivadent) and Prime&Bond NT (Dentsply Sirona). For each adhesive, two groups were prepared according to the method of adhesive system application. In the first group, the adhesive system and composite were cured separately (conventional method), whereas in the second group the adhesive and composite were cured simultaneously ("co-curing" method). Specimens were stored at 37 °C in distilled water and fractured in shear mode after 1 week. The optimal sample size for reliability analysis was obtained by preparing n=20 per experimental group (total n=80 for the whole study).
Results: The highest bond strength was observed for Prime&Bond conventional (22.0 MPa) and Excite F conventional (19.2 MPa), while lower bond strength was identified when co-curing was used (16.8 and 10.9 MPa, respectively). Within each bonding system, bond strength values attained by co-curing were significantly lower than the corresponding values attained by conventional curing.Weibull moduli for Excite F decline from 3.1 for conventional application to 2.5 for co-curing technique and for Prime&Bond from 4.5 to 3.4,repectively.


Conclusions: In the experimental model adopted for this study specimens prepared with conventional application technique produced higher shear bond strength in comparison to co-curing method according to conventional statistics and reliability analysis.