This study aimed to analyze the effect of different matrix metalloproteinase (MMP) inhibitors on the microtensile bond strength (microTBS) of an etch-and-rinse and a self-etching adhesive after 9 months of aging. Methods and Materials : Flat human dentin surfaces were bonded either with an etch-and-rinse adhesive (Optibond FL) or a self-etching adhesive (Clearfil SE Bond). Dentin surfaces were left untreated or were pretreated with MMP inhibitors (2% chlorhexidine digluconate [CHX], 0.05% green tea extract, 1 mM ferrous sulfate, or 0.2 mM galardin) prior to application of the adhesive. Composite buildups were made incrementally. Pretreated groups were tested after 9 months of storage in artificial saliva (37°C) and compared with untreated groups, which were tested immediately (initial microTBS) and upon aging (9-month microTBS). Data were analyzed by linear mixed-model regression. Failure mode analysis was performed microscopically and statistically analyzed by repeated-measures analysis of variance (p<0.05). Results : MicroTBS of the etch-and-rinse adhesive but not of the self-etching adhesive was significantly decreased by aging. For Optibond FL, pretreatment with 2% CHX, 0.05% green tea extract, and 0.2 mM galardin revealed bond strength values (MPa) similar to the initial microTBS (32.1±14.8) and significantly higher compared with the microTBS (20.3±13.6) of aged untreated dentin. No significant differences were observed between groups bonded with Clearfil SE Bond (initial microTBS: 28.3±12.4; 9-month microTBS: 25.3±11.8). Application of the MMP inhibitors decreased the number of adhesive failures compared with untreated controls after 9 months of aging, but this effect was not significant. Conclusion : The MMP inhibitors prevented the decrease in microTBS upon aging of the etch-and-rinse but not of the self-etching adhesive.