Nano-hydroxyapatite/polyamide 66 as a direct pulp capping agent has effects on histological changes of odontoblasts and microvessels / 中国组织工程研究

ABSTRACT

BACKGROUND:Previous studies have demonstrated that nano-hydroxyapatite/polyamide 66 (nHA/PA66) composites as a root canal filing material possess the basic physical and chemical properties, have antibacterial properties against the infection of medulary cavity, and have no cytotoxicity. However, it is rarely reported as a direct pulp capping agent. OBJECTIVE: To observe the histological reaction of nHA/PA66 composites as the pulp capping agent. METHODS:The first and second molars from 12 Wistar rats were selected to prepare class I cavities by exposing the dental pulp. Then, these rats were randomized into three groups and subjected to dental pulp capping using nHA/PA66 composite, nHA and calcium hydroxide, respectively, folowed by filing with glass ionomer cement. At 7 and 30 days after filing, histological changes of odontoblasts and microvessels in the dental pulp were observed using ink perfusion method. RESULTS AND CONCLUSION: At 7 days after filing, significant changes in dental pulp fibroblast proliferation, predentin thickening, dilation of blood vessels were observed in the nHA/PA66 group; only dental pulp fibroblast proliferation with no predentin thickening and dilation of blood vessels was found in the nHA group; in the calcium hydroxide group, the pulp tissues in the pulp chamber were mostly damaged, and obvious hyperplasia in dental pulp fibroblasts and certain inflammatory cel infiltration with vascular necrosis were observed. At 30 days after filing, predentin thickness was increased further, dental pulp fibroblasts proliferated, the number of odontoblasts increased, and dilation of blood vessels was observed in the nHA/PA66 group; predentin thickening and dilation of blood vessels were obviously visible in the nHA group; pulp necrosis was found on the pulp surface below the pitting pore, odontoblasts grew actively at the pulp junction, with no obvious thickening of the predentin, and there were dense vessels below the necrotic area. These findings indicate that the nHA/PA66 composite can induce the regeneration of dental pulp cels.