Effect of antibacterial varnishes applied to root dentin on shear bond strength of tooth-colored restorative materials

This study investigated the effect of certain varnishes on the bond strength of different tooth-colored restorative materials applied to root dentin. One-hundred and eighty tooth slabs, including mesial and distal surfaces, were attained through dividing the teeth, then embedding them in methylmethacrylate. The root surfaces were ground flat through cementum, exposing the dentin. The samples were then randomly divided into three main groups: Group 1: Cervitec; Group 2: Fluor Protector and Group 3: No applications (control). Cervitec and Fluor Protector were applied to the root dentin surfaces according to the manufacturer's instructions. All the samples were kept in artificial saliva for six months. Each main group was subdivided into five groups of 12 teeth each: Group A: Flowable Resin Composite (Grandio Flow); Group B: Microhybrid Resin Composite (Artemis); Group C: Polyacid Modified Resin Composite (Dyract Extra); Group D: Resin Modified Glass Ionomer Cement (Vitremer) and Group E: Conventional Glass-Ionomer Cement (Ionofil Molar). Restorative materials were applied to the root dentin surfaces using a cylindrical mold. After thermocycling (1000 cycles, 5 degrees C/55 degrees C, dwell time 30 seconds), the shear bond strength of the restored samples was determined by a universal testing machine (Zwick Test Machine, Zwick GmbH & Co, Ulm, Germany) at a 5 mm/minute crosshead speed. Failure mode was determined under a stereomicroscope. The data were evaluated statistically by using one-way Analysis of Variance and Duncan tests (p< or =0.05). In the fluoride varnish group, all of the restorative materials except for Ionofil Molar, showed lower bond strengths when compared to the control group (p<0.05). In the Cervitec group, Artemis and Dyract Extra showed lower bond strengths; whereas, Ionofil Molar showed a higher bond strength than the control group (p<0.05). The highest percentage of cohesive fracture was observed in Artemis and Dyract Extra in the control group.