Abstract
Purpose: We have established a potential cell therapy for pulp regeneration in a canine pulpitis model harnessing autologous dental pulp stem cells (DPSCs). Complete disinfection is essential for complete pulp regeneration in periapical disease. Our previous study suggested that medicaments could be delivered deeply into the dental tubules using nanobubbles together with ultrasound leading to rapid disinfection of the intracanal space. Thus, this study was performed in a canine periapical disease model to examine complete disinfection of the root canal system and complete pulp regeneration by the same cell therapy as in a pulpitis model.
Methods: The most suitable conditions for ultrasound and nanobubbles of less than 1 μm in diameter were examined to deliver medicaments deeper into the dentinal tubules of root canals. The canine root canal was kept open for 14 days to construct a periapical disease model. Vibramycin was applied in the root canal with or without ultrasound and nanobubble treatment every week, and the change in the number of bacterial colonies was examined during the root canal treatment. The transplantation of autologous DPSCs and a migration factor in the root canal was performed after four times of treatment, followed by morphological examination 2 weeks after transplantation.
Results: The most suitable condition of the ultrasound was a voltage 32 V, 1.12 MHz and for 120 seconds to deliver medicaments to the depth of over 1,000 μm from the dentinal wall. Two times of medication using ultrasound with nanobubbles decreased the number of bacterial colonies under the limit of detection in the canine periapical disease model, demonstrating a significant difference compared to the root canal dressing only. A significantly higher volume of regenerated pulp and periapical tissue was demonstrated two weeks after cell transplantation in the ultrasound treated teeth compare to that in untreated teeth and there was no inflammatory cell infiltration.
Conclusion: It is suggested that enhanced delivery of medicaments using ultrasound with nanobubbles has potential utility for pulp regeneration and root canal treatment.
