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Influence of chlorhexidine concentration on the durability of etch-and-rinse dentin bonds: a 2-month in vitro study.
Commentary by Howard E. Strassler, DMD
Breschi L, Cammelli F, Visintini E, et al. J Adhes Dent. 2009;11:191-198.
PURPOSE: To investigate the effect of 0.2% and 2% chlorhexidine (CHX) used as a therapeutic primer on the long-term bond strengths of two etch-and-rinse adhesive systems.
MATERIALS AND METHODS: Adper Scotchbond 1XT (SB1) and XP-Bond (XPB) were evaluated. Etched dentin substrates were assigned to 6 treatment groups: (1) 0.2% CHX + SB1; (2) 2% CHX + SB1; (3) SB1 (control); (4) 0.2% CHX + XPB; (5) 2% CHX + XPB; (6) XPB (control). Composite buildups were made and beams prepared for microtensile bond strength testing. Beams were divided into 3 subgroups and either immediately pulled to failure or stored in artificial saliva for 6 or 12 months prior to testing. Data were evaluated with three-way ANOVA. Additional adhesive interfaces were prepared to investigate nanoleakage expression by TEM.
RESULTS: SB1 and XPB showed similar immediate bond strength values with or without CHX pretreatment (P > .05). After 12 months, bonds fell from 43.9 +/- 9.5 MPa to 20.1 +/- 5.4 MPa and from 39.6 +/- 9.4 MPa to 14.2 +/- 5.0 MPa in control specimens for SB1 and XPB respectively, while bond fell only from 41.9 +/- 9.6MPa to 33.2 +/- 8.3 MPa and 38.3 +/- 8.9 MPa to 26.5 +/- 10.9 (for SB1 and XPB, respectively) when 0.2% CHX was previously used. CHX concentration did not affect bond strength values (0.2% vs 2%, P > .05). Nanoleakage increased during aging in controls, but reduced silver deposits were found in CHX-treated specimens.
CONCLUSION: Chlorhexidine significantly reduced the loss of bond strength seen in control bonds. Since no bacterial growth was present in the aging conditions, the results of this study suggest that endogenous factors thought to degrade the adhesive interface can be inhibited by CHX. Further in vivo trials should confirm the role of CHX in bond durability.
Because it has been speculated that matrix metalloproteinases (MMPs) may be partially responsible for hybrid layer degradation, the use of a reagent that inhibits MMPs could decrease the degradation of the resin-collagen fibril network. It has been known that chlorhexidine (CHX) inhibits MMPs, so the researchers hypothesized that CHX decelerates the loss of resin-dentin bonds. The results of this study suggest that endogenous factors thought to degrade the adhesive interface can be inhibited by CHX. While there is need for further in vivo trials to confirm the role of CHX in bond durability, what should you do? From speaking to research colleagues and other articles on the topic, my recommendation would be to have your pharmacy mix up a 2% CHX solution. After etching (etch and rinse), as a pretreatment before adhesive application, apply a 2% CHX solution on a cotton pellet for 60 seconds, blot dry, apply adhesive, light-cure, and restore.
About the Author
Howard E. Strassler, DMD
Professor, Division of operative Dentistry
Department of endodontics, Prosthodontics and operative Dentistry
University of Maryland Dental School