Microtensile Bond Strength of Adhesives Applied with an Electric Device

Objectives: Aim of this study was to analyse the microtensile bond strength of two adhesive systems applied using a disposable sponge or using a novel electric device (US Patent 6,641,396 B2) to layer the adhesive agent on the tooth surface. Methods: Ten non carious recently extracted human teeth were selected for the study. Middle dentin was exposed with a diamond saw under water cooling and standard smear layer was created. Specimens were then longitudinally cut in two parts. Adhesives were applied on one side of the tooth following manufactures' instructions and on the other side using the new tested electric device. The selected adhesives were: (1) One Step Plus (OSP) and (2) Prime & Bond NT (P&B NT). A 4 mm resin restoration Filtek Z 250 (3M) was built up on the bonded surfaces. Specimens were sectioned and processed for microtensile test. The results were calculated in MPa (allowing for differences in bond area) and ANOVA and Multiple Range (LSD) tests were applied. Results: The mean of microtensile bond strength value for OSP is 27,83MPa (without electric device) and 36,48MPa (with electric device). For P&B NT the mean is 26,07 (without electric device) and 38,26 MPa (with electric device). For each adhesive there is a statistically significant difference between the groups (p<0.01). For both adhesives no statistically significant difference was observed in fracture mode between the groups. Conclusions: The use of electric impulses created by a new device for the application of dental bonding systems increase bond strength to middle/deep dentin substrate of adhesive systems applied following the total etching procedure. This may be related to the piezoelectric characteristics of the collagen fibrils exposed by the etching procedures. How much this electric device contributes to improve the long term stability of bonding should be further investigated.