Inhibitory Properties and Shear Bond Strength of Benzalconium Chloride-containing Adhesives

Inhibition of endogenous dentin matrix metalloproteinases (MMPs) by benzalconium chloride (BAC) has shown to reduce collagen degradation by zymographic analysis. The optimal application would incorporate a given concentration of BAC into the adhesive resin.

Objective: To assess the MMP inhibitory properties of increasing concentrations of BAC by gelatin zymography, and  the shear bond strength (SBS) of etch-and-rinse adhesives modified with the same concentrations of BAC at 24h.

Methods: 1) Gelatin zymography: Extracts from concentrated demineralized human dentin powder were subjected to SDS-PAGE electrophoresis and incubated in the presence of BAC (0.25%, 0.5%, 1% and 2%). The gels were run in triplicate. Identification of MMP-2 and MMP-9 was confirmed by Western blot with specific antisera. 2) Shear bond strength: Two etch-and-rinse adhesives were modified with 0.25%, 0.5%, 1% and 2% BAC. SBS was evaluated after 24h of storage (100% humidity at 37°C) and compared against a control group, and other two commonly used protocols for antimicrobial application, Consepsis (Ultradent) and Etch-37 with BAC (Bisco) (n=20). A two-way ANOVA was used for data analysis.

Results: Complete inhibition of MMP-2 and MMP-9 was demonstrated by zymography regardless of the concentration of BAC. The adhesive type demonstrated a significant effect on the SBS (p<0.001). No significant effect of the treatment (p=0.141) or the interaction adhesive-treatment was shown (p=0.297).

 

Group	Description	Adhesive A SBS MPa(SE)	Adhesive B SBS MPa(SE)
1	H3PO4+Adhesive (control)	28.7(2.5)	18.3(1.5)
2	H3PO4+2%CHX +Adhesive	26.4(2.5)	17.8(1.9)
3	H3PO4  containing 1%BAC+Adhesive	28.3(2.8)	16.2(1.9)
4	H3PO4+Adhesive containing 0.25%BAC	26.1(2.8)	23.8(2.8)
5	H3PO4+Adhesive containing 0.5%BAC	24.3(1.7)	18.8(1.9)
6	H3PO4+Adhesive containing 1%BAC	28.8(2.1)	16.7(2.3)
7	H3PO4+Adhesive containing 2%BAC	22.7(2.7)	13.9(2.0)

Conclusion: All concentrations of BAC completely inhibited MMP-2 and MMP-9 activity as demonstrated by zymography. Incorporation of different concentrations of BAC into the etch-and-rinse adhesives did not affect early shear bond strengths to dentin.