Effects of incorporating chlorhexidine into all-in-one adhesives

Objectives: It is known chlorhexidine(CHX) does not lower micro-tensile bond strengths (mTBS) even after 500 days, when it is applied between priming and bonding with SE Bond. We reported that up to 2% CHX was the optimum concentration in all-in-one adhesives because higher concentrations of CHX in those adhesives caused lower degrees of polymerization that resulted in lower bond strengths. The purpose of this study is to evaluate the mTBS of AQ Bond Plus with or without CHX after immersion in water for 2 years.

Methods: AQ Bond Plus (Sun Medical, Japan) and two experimental all-in-one self-etching adhesives containing 1 or 2% CHX were used in this study. Three teeth in each were treated with one of the self-etching adhesive for 20 sec followed by resin composite built-up to 5 mm thick with Clearfil AP-X.  Resin-bonded teeth were vertically sectioned into slabs after 24 hours or 2 years in water. Each slab was cut to dumbbell shape for mTBS.

Results: The mTBS of AQ adhesive without CHX fell 50% after 2 years was not different than the same experimental adhesive after 24h, experimental adhesive containing 2% CHX after 2 years were lower than after 24h. (Two-way ANOVA, Tukey's test; p<0.01)

	AQ Bond Plus (MPa)	Experimental AQ Bond Plus (1% CHX)	Experimental AQ Bond Plus (2% CHX)
24 hours after bonded	65.8 ± 9.6a	53.2 ± 8.2c	53.8 ± 8.6c,a
2 years after bonded	33.1 ± 8.0b	46.9 ± 13.3c	33.9 ± 9.1b

Incorporating 1 or 2% CHX into AQ adhesive inhibited the mTBS seen in nonCHX controls after 2 years. However, when 2% CHX was incorporated in AQ Bond Plus, the polymerization was lower, causing lower mTBS after 2 years.

Conclusion: The addition of 1% CHX in AQ Bond Plus did not lower mTBS even after 2 years.