Antibacterial effects of different low-level doses of double antibiotic paste on multispecies biofilms in regenerative endodontics: A confocal laser microscopy study

Aim: This research aimed to assess the comparative efficacy of various concentrations of double antibiotic paste used on multispecies biofilms in regenerative endodontic procedures. Methodology: Seventy caries-free human teeth with a single root that were extracted for orthodontic purposes were gathered. A total of 900 μL of bacterial suspension was prepared, comprising three bacterial species: E. faecalis (ATCC 43146), A. naeslundii (ATCC 10556), and S. sanguinis (ATCC 29212). Six experimental groups (n=10/group) were randomly created with the infected dentin slices: 0.125 mg/ml, 0.25 mg/ml, 0.5 mg/ml, 1 mg/ml, 5 mg/ml, 10 mg/mlof double antibiotic paste and a control group. Confocal laser scanning microscopy (CLSM) analysis was conducted to evaluate the antimicrobial activity. Two samples from each group were analyzed with a scanning electron microscope. The live/dead bacteria percentages were analyzed via Kruskal–Wallis test. The tests were conducted with a significance level of 5%. Results: Greater live/dead bacteria ratios were observed in the control group, and the differences compared to other groups were statistically significant. Additionally, the numbers of live/dead bacteria observed after the 0.5 mg/mL and 1 mg/mL DAP doses were applied were significantly higher compared to the 10 mg/mL DAP concentration. All DAP doses exhibited some degree of antibiofilm activity; however, 5 mg/mL and 10 mg/mL were the most effective. Conclusion: In regenerative endodontics, the 5 mg/mL and 10 mg/mL doses of DAP demonstrated more effective activity against multispecies biofilms than lower doses.