Healing in transplanted teeth with periodontal ligament cultured in vitro

Regeneration of connective tissue attachment is the ultimate goal of periodontal therapy. It has been suggested that periodontal ligament cells possess the potential to create new connective tissue attachment. However, as cells from gingiva and alveolar bone occupy the root surface during initial wound healing, population by periodontal ligament cells is limited in vivo. We have been developing a new periodontal regeneration technique using in vitro tissue culture of periodontal ligament remaining on a periodontally involved root. The purpose of this study was to examine the periodontal healing after transplantation of teeth with reduced periodontal ligament that had been cultured in vitro. Twenty-five incisors from four beagles were used. After the teeth were extracted, the periodontal ligament and cementum were removed from coronal part of the roots and the roots were planed. The periodontal ligament of the apical part was retained. Fourteen teeth of the experimental group were transplanted following culture for 6 weeks. Eleven teeth of the control group were similarly prepared and immediately transplanted without tissue culture. Four weeks after transplantation, the specimens were prepared for histological analysis. Downgrowth of junctional epithelium on the root of experimental group was significantly less than control. Most of the root planed surfaces of experimental group were covered with periodontal ligament fibers oriented parallel or inclined to the root surfaces and limited new cementum formation was observed near the apical end of the planed root. There was no significant difference between groups in observations on the root surface with remaining periodontal ligament. From the above results, it was concluded that periodontal tissue culture of teeth with root planed surface and remaining periodontal ligament could reduce the extent of epithelium downgrowth and increase connective tissue adhesion on the root planed surface, as well as minimize damage to remaining periodontal ligament, after transplantation of teeth.