Effect of benzalkonium chloride on resin-dentin bond durability

Objectives: The resin-dentin bond is degraded by endogenous dentinal proteinases activated by acidic compounds contained in dental adhesive systems. Several compounds have been suggested to neutralize these proteinases, including benzalkonium chloride (BAC). The objective is to evaluate the effect of incorporating various concentrations of BAC on the short and intermediate bond strength of a one-step self-etch adhesive. Methods: Forty-eight human molars stored in 0.5% chloramine solution were used within 3mo of extraction and randomly assigned to 4 groups (n = 12). Flat dentin surfaces were prepared with a water-cooled, low-speed diamond saw (Isomet1000, Buehler). A standardized smear layer was prepared using 600-grit wet sandpaper. Three experimental one-step self-etching adhesives (Bisco Inc.) were formulated with 0.1%, 0.2% and 0.5% BAC in Groups 1, 2 and 3, respectively. A non-modified version served as the control, Group 4. Adhesives were applied following manufacturer's guidelines. A three increment build-up of approximately 5mm was made using resin composite Estelite Sigma Quick (Tokuyama). Each increment was light cured (690-730 mW/cm²) for 20sec with an Optilux 500 (Demetron-Kerr). After storage in artificial saliva at 37^oC, the resin-dentin specimens were sectioned to obtain six rectangular sticks from the central part of the bonded surface with a cross section area of approximately 0.8mm. At random, two sticks from each group were subjected to tension at a crosshead speed of 1.0mm/min using a Zwick testing machine at 1wk and two sticks at 10wks. Results: A two-way repeated measures ANOVA was used to evaluate differences among the groups by adhesive and storage time at alpha 0.05. There was no statistically significant difference among groups (p > 0.05).  Storage time and BAC concentrations did not affect microtensile bond strength. Conclusions: The incorporation of BAC did not affect the bond strength of the experimental one-step self-etch adhesive.

Tensile strength mean (sd) in MPa
	1wk	10wk
Exp 1:  0.1% BAC	15.9 (8.1)	17.9 (10.1)
Exp 2:  0.2% BAC	20.5 (13.1)	17.1 (13.7)
Exp 3:  0.5% BAC	16.1 (6.3)	14.8 (10.1)
Exp 4:  No BAC (control)	16.7 (6.8)	19.0 (11.0)