Dual role of piperine: Preserving the degree of conversion of resin cement on bleached enamel and exhibiting antimicrobial activity.

Background: Piperine piperine extracted from Piper nigrun has a significant potential for use in dentistry and other areas of medical sciences. Promising results concerning this agent in in vitro tests can influence the development of new drugs, medical products, and clinical procedures. The present study aimed to extract, characterize, and evaluate the antimicrobial and antioxidant effect of piperine derived from Piper nigrun. Material and Methods: Extraction of piperine was carried out using a reflux system and confirmed by UV-Vis spectrophotometry and nuclear magnetic resonance spectroscopy. Piperine was diluted in distilled water at 0.001%, 0.002%, and 0.004%. Antioxidant activity of piperine was carried out by analyzing the degree of conversion (DC) in situ of self-adhesive resin cement applied to enamel fragments bleached with 35% hydrogen peroxide. Meanwhile, the antimicrobial activity was assessed using the broth microdilution technique. Statistical analysis of the DC was evaluated with the ANOVA and Student-Newman-Keuls test. Results: The minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC) and minimum bactericidal concentration (MBC) were performed with Kruskal-Wallis test. Level of significance adopted was p<0.05. The yield of piperine extraction was 92.86%. No statistical difference between DC values of the piperine groups (0.001%, 0.002% and 0.004%), without whitening group and withening + cemented after 7 days (p>0.05). The whitening + immediate cementation group showed the lowest DC when compared to the other groups (p<0.05). The MBC evidenced antimicrobial activity (p<0.05) at a concentration of 0.004% in comparison with the negative control, without treatment, and the positive control, using chlorhexidine 0.12%. The MFC revealed a reduction in colonies at a concentration of 0.004% when compared to the other groups and controls (p<0.05). Conclusions: Piperine exhibited antifungal and antibacterial properties and avoided the reduction in the degree of conversion of a self-adhesive resin cement applied on bleached enamel.