A 2-year in vitro evaluation of a chlorhexidine-containing acid on the durability of resin-dentin interfaces.

OBJECTIVE: This study evaluated the effect of 2% chlorhexidine-containing acid (Ac/CHX) and 2% chlorhexidine digluconate solution (CHX) on immediate (IM) and 2-year (2Y) resin-dentin bond strength (BS) and silver nitrate uptake (SNU) for two simplified etch-and-rinse adhesives.

METHODS: Forty-two caries-free extracted molars had a flat dentin surface exposed. In the control groups (groups 1), the surfaces were acid etched with conventional phosphoric acid and the adhesives Prime&Bond NT (PB) or Adper Single Bond 2 (SB) was applied after rinsing, drying and rewetting with water. In groups 2, Ac/CHX groups the adhesives were applied in a similar manner; however a 2% CHX-containing acid was previously applied. In groups 3, the adhesives were applied according to the control group; however the rewetting procedure was performed with an aqueous solution of 2% CHX for 60s. Composite build-ups were constructed incrementally and microtensile specimens (0.8mm(2)) were prepared for microtensile bond strength testing in the IM or 2Y periods at 0.5mm/min. For SNU, 2 bonded sticks from each tooth were coated with nail varnish, placed in the silver nitrate, polished down with SiC papers and analysed by EDX-SEM. The data from each adhesive was submitted to a two-way repeated measures ANOVA and Tukey's test (α=0.05).

RESULTS: After 2Y, significant reductions of BS were observed for both adhesives in the control group (p<0.05). In Ac/CHX or CHX groups the BS remained stable for both systems. SNU was more evident in the control than in the experimental groups (p<0.05) both in IM and 2Y periods. The use of CHX in an aqueous solution or associated with the acid conditioner was effective to reduce the degradation of dentin bonds over a 2-year period.

SIGNIFICANCE: The addition of CHX digluconate in the acidic conditioner may be an excellent tool to increase the long-term stability of collagens fibrils within the hybrid layer against host-derived metalloproteinases without the need for additional steps for the bonding protocol.