Antibacterial Efficacy and Discoloration Effect of a Novel Intracanal Antibiotic Dressing

Abstract

Various antibiotics have been used an intracanal medicaments for endodontic therapy. Although some of them are effective, they have unfavorable effects such as coronal discoloration and cytotoxicity of stem cells. However, there is a gap in knowledge regarding the potential discoloration effect of different concentrations of antibiotics as an intracanal medicament as well as their efficacy as intracanal medicaments. Thus, the aims of this study were 1) to determine, in vitro, the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) of Augmentin, tigecycline, and triple antibiotic mix (TAP) (Metronidazole, ciprofloxacin, and minocycline) against selected common endodontic pathogens, 2) to determine, ex vitro, the antibacterial efficacy of Augmentin, tigecycline, and TAP at different concentrations using a slow release hydrogel scaffold, and 3) to evaluate, ex vitro, the potential discoloration effect of these antibiotics compared to TAP at high concentration (1 g/mL). Methods: A biofilm of F. nucleatum, P. gingivalis, S. intermedius, and E. faecalis were grown in extracted single rooted teeth in an anaerobic condition for three weeks. TAP (1g/ml), as well as TAP, Augmentin, and tigecycline all at different concentrations (0.1 mg/ml and 1mg/ml) were incorporated into a slow release degradable hydrogel scaffold and used as intracanal medicaments. One group received no antibiotics (Control group). Antibacterial efficacy was evaluated using colony forming unit (CFU) counts. Coronal discoloration was evaluated spectrophotometerically 1, 2 and 3 weeks after treatment with antibiotics groups. ANOVA followed by Tukey's HSD tests were used for statistical analysis. Results: All samples from the control group (no antibiotics) showed a bacterial growth. Significant differences were found when comparing the log 10 CFUs of the seven experimental groups (p ≤ .0005). The mean CFUs for 1mg concentration group were significantly lower than the control group and 0.1 mg/ml concentration antibiotics groups. TAP at 1g/ml concentration group resulted in no bacterial growth. There were no significant differences in CFUs between TAP (0.1 mg/ml), Tigecycline (0.1 mg/ml), and Augmentin (0.1 mg/ml) and no significant differences in CFUs between TAP (1 mg/ml), Tigecycline (1 mg/ml), Augmentin (1 mg/ml) and TAP (1g/ml). For the one-week coronal color change, teeth treated with Augmentin at 0.1 mg/ml and 1mg/ml concentrations had significantly lower color change than the other five experimental groups. On the other hand, teeth treated with TAP at 1g/ml concentration had significantly higher color change than other groups. (p ≤ .0005). At 2 weeks post-treatment, Augmentin at 1 mg/ml concentration had the lowest color change followed by TAP and Tigecycline at 1 mg/ml. The highest color change was recorded for teeth treated with TAP at 1 g/ml concentration. (p <.0005). Similarly, at 3 weeks post-treatment, Augmentin at 1 mg/ml concentration had the lowest color change followed by Tigecycline and TAP at 1 mg/ml. The highest color change was recorded for the TAP at 1 g/ml group. (p <.0005). At all time periods, TAP at high concentration (1g/ml) resulted in the highest coronal color change compared to other antibiotics groups. (p ≤ .0005). Conclusion: TAP at high concentration (1g/mL) was the most efficacious antibiotic against common endodontic bacteria biofilms. However, it resulted in the highest discoloration of teeth structure. On the other hand, TAP, Augmentin and tigecycline at low concentration (1 mg/ml) reduced bacterial growth significantly with minimum teeth color change when applied for 1 week.