Electron and Light Microscopic Study of Pulp Polyps

Chronic hyperplastic pulpits or pulp polyps is a rare and curious phenomenon of the dental pulp. They are a unique response of the exposed pulp to the oral environment. The exposure of the vital pulp to the irritating oral environment usually causes necrosis and loss of vitality of the pulp with the attending sequellae. Pulp polyps, however, are a form of pulpitis that occur in teeth with exposed pulps in which the connective tissues have retained their full vitality. Objective: To investigate the cellular makeup, innervations are possible changes the pulp polyps undergo in their development. Methods: Twenty-two polyps were obtained for this investigation from patients ranging in age from 18 months to 45 years. Half of each polyp was prepared for light and electron microscopic evaluation. In the light microscopy study serial sections were stained alternately with Hemotoxilin and Eosin for general histology observation and Bodian's stain for nerve distribution. Results: Microscopically, four types of polyps were found in relation to their surface appearance 1) parakerotinized epithelium, 2 keratinized epithelium, 3) inflammatory cell covering, and 4) no cell covering. The epithelized polyps appeared similar to oral epithelium with a normal appearing basal lamina and cellular appearance. Melanocytes were present in the basal layer. The connective tissue stromas contain many lymphocytes, PMN cells, plasma cells and fibroblast cells. Nerve distribution was found throughout the polyp stroma. No interepithelial nerves were observed. Conclusions: Melanocytes and some odontoblast cells have been found to originate from embryonic neural crest tissue. Therefore, we propose that the epithelium covering is formed by the pulp polyp and not from oral epithelium, as reported in the literature.