Spontaneous early exposure of submerged implants: III. Histopathology of perforated mucosa covering submerged implants.

Abstract

Spontaneous early exposure of dental implants could interfere with the early healing phase of dental implants. These exposures have been clinically classified according to degree of implant exposure from 0 (intact mucosa) to IV (complete exposure). The characteristics of perforated mucosa (Class I and II) covering submerged dental implants were examined histologically in this study. Biopsy specimens of 34 Class I and II perforated mucosa covering submerged dental implants were examined histologically. Serial sections were evaluated from the periphery of the specimen to the center of each perforation lesion. Class I specimens presented hyperplastic epithelium characterized by hyperparakeratosis and acanthosis. Chronic inflammatory cells diffusely infiltrated the connective tissue. Sections closer to the perforation revealed gradual epithelial invagination; in the deepest aspect, there was a cyst-like structure in all Class I specimens examined. A thin layer of connective tissue containing necrotic material and debris formed the "cystic" wall proximal to the implant cover screw. Class II specimens presented the same epithelial patterns; however, the cystic structures were replaced by direct contact between the cover screw and the oral cavity via the perforation. Spontaneous early perforations are the sequela of either traumatic irritation or failure of the tissue flaps to produce primary healing. Most Class I perforations include epithelial invagination and the formation of a cyst-like structure. Necrosis of the base of the "cyst" or enlargement of the perforation results in direct communication between the oral cavity and the covering screw surface (Class II).