Effectiveness of 3Mix-MP Paste as Pulp-Capping Agent in Murine Molars

Objectives: The combination of Metronidazole, Ciprofloxacin and Minocycline, also known as 3Mix, has been proved to be effective against oral bacteria in vitro and in vivo. Although extensive evidence supports the effectiveness of 3Mix in endodontic treatments of deciduous and immature permanent teeth, the biological response of the dental pulp following its use as capping agent remains to be clarified. This study aims to analyze the pulpal responses to capping with 3Mix-MP in murine molars, compared with those to calcium hydroxide cement.
Methods: Thirty-eight 6-week-old Crlj:CD1(ICR) mice were used in this study. Under intraperitoneal anesthesia, class I cavities were prepared on the upper first molars to expose the dental pulp. Teeth were maintained without further treatment for 24 hours to induce the contamination of the dental pulp. Next, the exposed molars were capped with 3Mix dissolved in a mixture of macrogol and propylene-glycol (3Mix-MP), or calcium hydroxide cement (CH), in addition to macrogol and propylene glycol alone as a negative control (MP), followed by a restoration with a self-cured glass ionomer cement. Materials were collected at weeks 1, 2 and 3 after operation and processed for hematoxylin-eosin and immunohistochemistry for nestin and Ki-67, as well as TUNEL assay.
Results: 3Mix-MP accelerated cell proliferation at Weeks 1 and 2, favoring the survival and/or differentiation of newly-differentiated odontoblast-like cells, and tertiary dentin deposition at the injury site. In contrast, in the CH group, the healing process was still delayed at Week 3; whereas the highest rate of dental pulp necrosis was seen in the MP group.
Conclusions: The use of 3Mix-MP paste as a pulp-capping agent effectively improve the regeneration process of the contaminated dental pulp in mice molars compared with calcium hydroxide cement. Further investigations should address the responses to 3Mix-MP paste at cellular and gene levels following severe pulpal injuries.