Procedural Effects on the µTBS of Self Etching Primers

Objectives: The purpose of this study was to determine the influence of deviations from the manufacturers’s instructions on the µTBS of two single stage self-etching primers. Methods: The materials used were Xeno III (DENTSPLY) and Adper Prompt L-Pop (3M ESPE). Thirty extracted human third molars were randomly divided into two groups of fifteen teeth each and each group was then subdivided into three groups of five teeth each. Xeno III was used in the first group (15 teeth), and APLP was used in the second group (15 group). Resin composite (Pertac-Hybrid. 3M ESPE) was bonded to flat, mid-coronal dentine using the adhesives strictly according to the respective manufacturer’s instructions in the first five teeth group. The second group of five teeth was subjected to a bonding procedure of three coats of adhesive with a light cure for 20 sec in between each coat. The third group of five teeth was subjected to a bonding procedure of three coats of the adhesive without a light curing in between coats. Bonded specimens were sectioned into stick shapes of approximately 0.8 mm2 cross-sectional area and subsequently subjected to a µTBS test at a crosshead speed of 0.5 mm/min. Results: Multiple layer application with light cure in between each layer resulted in reduction of µTBS of APLP (28 MPa to 14.5 MPa) and Xeno III (31.5 MPa to 24.3 MPa) self-etch primers. There was a significant increase in µTBS of Xeno III (41 MPa) after multiple layers application without light curing in between layers, whereas there was no significant change for APLP (32.5 MPa). Conclusions: Deviation from manufacturers’ instructions can significantly influence the µTBS of single stage self-etching primers to human dentine. The application of multiple layers of self-etching primer with light curing in between each layer is not recommended.