Novel evaluation method of dentin repair by direct pulp capping using high-resolution micro-computed tomography

Objectives: We evaluated a novel micro-computed tomography (micro-CT) assessment for quality and quantity of dentin repair, which is difficult to visualize by histological analysis, after direct pulp capping under standardized cavity preparation. Materials and methods: Standardized cavities were prepared on Wistar rats and direct pulp capping was performed using two commercial bioceramics, ProRoot MTA, and iRoot BP Plus. After 2 or 4 weeks, quality and quantity of tertiary dentin formation were evaluated using high-resolution micro-CT analyses including dentin mineral density, dentin mineral contents, compactness and integrity of tertiary dentin, and dentin volume with/without void space. Reproducibility of micro-CT analyses was confirmed by histological evaluation of the same specimen. Results: The exposed pulp area sizes were similar between iRoot BP Plus and ProRoot MTA. Micro-CT analysis of 2-week samples showing compactness of tertiary dentin was significantly higher in iRoot BP Plus than ProRoot MTA (p < 0.05). Tertiary dentin volume without void space, dentin mineral contents, and density were not significantly different between the groups. In 4-week samples, a significant increase was observed in dentin mineral density, compactness, and dentin volume with/without void space induced by iRoot BP Plus (p < 0.05). Micro-CT analysis of tertiary dentin integrity demonstrated that some ProRoot MTA specimens had small defects and lacked continuity (6/512 images). No defects were observed with iRoot BP Plus. Conclusions: Micro-CT analysis was confirmed as an accurate, objective, and inclusive approach for evaluating quality and quantity of dentin repair. Clinical relevance: These multifaceted approaches to evaluate pulp capping materials may accelerate review processes, ultimately improving vital pulp therapy.