Self-etching Primers: Influence of Different Application Procedures on Etch Patter Formation and Shear Bond Strength

Objective: The introduction of self-etching primers in adhesive dentistry, seem to be a promising approach for reducing technique sensitivity. Since the acidic monomer is not rinsed away, it has to be immobilized by polymerisation. There has been some concern that demineralization and mechanical interlocking is quite reliable and not technique sensitive. In this study the effect of rubbing the primer into a cavity or to wait without agitation on etch-patter formation and shear bond strength of two self-etching, self-curing primers was compared. Methods: A commercially available self-etching self-curing primer system (Panavia-21, Kuraray) and an experimental system (Experimental, Ivoclar Vivadent) were used. For each group 5 bovine incisors were polished with 1000 grit to expose dentin respectively enamel. The primers were either applied and left undisturbed for 15s respectively 60s or rubbed on the surface for 15s. The composite were built up to a 4-mm height and after 24h of storage SBS were measured according to ISO/TS11405. ANOVA were used to determine inter-group differences. Results: On dentin shear bond strength values are significantly higher (p<0.05) in the case of agitation compared to no agitation at short application time. For longer application time and on enamel the agitation has minor influence. Short application time with agitation results in comparable shear bond strength as longer application time without agitation. Same results are obtained by SEM investigation regarding on tag formation on dentin and enamel surface morphology.

SBS (MPa) using different application protocols

Means with same superscript are statistically different.

Conclusion: Mechanical agitation of self-etching primers during application is advantageous with regard of time saving and bond strength on enamel and dentin.