Histologic Investigation of Gingival Epithelium Implantation and the Nonincision Placement of Miniscrews

Purpose: This study investigated whether the nonincision placement of miniscrews could lead to ectopic implantation of epithelium at the bone-implant interface and, if so, whether the epithelial cells could survive. The fate of grafted epithelial cells was also investigated. Materials and Methods: Ten healthy male beagle dogs were included in the study and were divided into three groups. Group 1 dogs (n = 3) were implanted with miniscrews without any other procedures. In group 2, epithelial cells were collected, infected by adenoassociated virus-2 containing green fluorescent protein (GFP), and injected into pilot holes drilled before miniscrew implantation in three dogs, and one dog was injected with epithelial cells as a negative control. In group 3, tiny gingival tissue pieces were injected into pilot holes drilled before miniscrew implantation. In group 1, hematoxylin-eosin and fluorescent immunohistochemical (IHC) staining of cytokeratin were performed on both undecalcified and decalcified slices. In groups 2 and 3, IHC staining of cytokeratin and apoptotic testing were performed. Results: No ectopically implanted epithelial cells were found at the boneimplant interface of the miniscrews in group 1. In group 2, fluorescence emitted by cytokeratin antibody and by GFP was observed in specimens at 0 days, had decreased by 3 days, and had disappeared by 7 days. In group 3, areas of fluorescent cytokeratin-positive tissues were much smaller at 7 days than at 0 days, and none were found at 28 days. In groups 2 and 3, there were many apoptotic epithelial cells at the boneimplant interface at 3 days and 7 days, respectively. Conclusion: There was little possibility of implantation of epithelium into alveolar bone though placement of miniscrews with a nonincision procedure. Furthermore, even when epithelial cells or tissue was ectopically implanted, it was soon cleared through an apoptotic process. Keywords: epithelium implantation, miniscrew, nonincision placement