Influence of Layering Technique on an “All-In-One”, Self-Etch Adhesive

Methods: Flat enamel and dentin surfaces were prepared with SiC paper, grit 80 through 500. In all groups (n=8), the dwell time (30s each) and light curing time(s) (20s each/layer) were standardized. The adhesive application techniques in each group varied as follows; (A) apply one layer, dwell, evaporate solvent, cure. (B) apply first layer, dwell, evaporate solvent, cure, apply second layer, evaporate solvent, cure. (C) apply three consecutive layers, dwell, evaporate solvent, cure. (D) apply first layer, dwell, evaporate solvent, apply second layer, evaporate solvent, apply third layer, evaporate solvent, cure. (E) apply three consecutive layers, dwell, evaporate solvent, cure, apply another three consecutive layers, evaporate solvent, cure. Following adhesive application, VENUS composite (HERAEUS Kulzer) was bulk filled via standardized cylindrical plastic molds (ULTRADENT) and cured for 20s with a halogen light. SBS was determined after 24h storage of specimens in 37°C tap water. Statistical analysis was done by ANOVA and Duncan (p<0.05). Adhesive layer thickness was analysed with light microscopy (x500) on perpendicular sections through the bonding interface. Results: SBS [MPa] on enamel/dentin: (A) 19.9^A/15.9^a,b, (B) 18.8^A/21.1^b,c, (C) 19.5^A/26.7^c, (D) 18.7^A/19,9^a,b, and (E) 16.8^A/13.5^a. Adhesive layer thickness [µm]: (A) 7.0^A, (B) 13.4^C, (C) 10.0^B, (D) 9.7^B, and (E) 16.8^D. Same upper- and lower-case letters indicate values that are not significantly different.

Conclusions: Variation of the adhesive application technique did result in statistically significant differences in adhesive layer thickness. There were no statistically significant differences found in the SBS to enamel, however, the SBS to dentin was influenced by the technique of adhesive layer application.