The effectiveness of the use of fifth-generation adhesive systems if changing the protocol before and after thermal cycling

Abstract

Fifth-generation adhesives are very popular in daily clinical practice. They have reduced number of components by combining a primer and an adhesive in a «single bottle». These adhesives have become more popular due to the reduction of application stages, but their adhesion strength to dentin turned out to be worse than that of the fourth-generation adhesives. The main mechanisms of adhesion of any dental material: moistening of the surface, micromechanical adhesion, chemical adhesion.Aim. To evaluate the bond strength of tooth tissues with the filling material using different fifth-generation adhesive protocols.Materials and methods. We used the 40 exctracted teeth due to orthodontic indications (molars and premolars). In preparation for the experiment the teeth were randomly divided into 2 equal groups according to the number of adhesive protocols used: control and main. The teeth surfaces (n=20) of the control group were treated according to the instructions, the surface treatment with a moistening agent was added to the protocol of teeth surfaces (n=20) in the main group before applying the adhesive. After curing of the adhesive a 3×3 steel detachable cylindrical mold was installed on the surface of the samples (n=40) of both groups filled with a composite paste. The prepared samples of the control (n=10) and main (n=10) groups of 2 subgroups were subjected to thousands (1000s) thermocycles with a temperature of (5±2) °C and (60±2) °C. Tests of the adhesive shear bond strength of the prepared (n=40) samples of the control (n=20) and main (n=20) groups before and after thermocycling were carried out on a universal testing machine SYNTHEZ 5.Conclusion: Thermocycling provides the reliable adhesion but reduces the adhesive strength of the filling material with hard tissues of the tooth. Adding of moisturizing agent into the protocol leads to a decrease in the adhesion strength up to 15% compared to 7% in protocol without it.