Periodontal wound healing in the absence of periodontal ligament cells.

This experiment was designed to study the ability of mucoperiosteal flap connective tissue to form new attachment on partially demineralized roots as well as nondemineralized roots in a wound-model where periodontal ligament (PDL) cells are absent, and ingrowth of bone granulation tissue is controlled. After reflecting mucoperiosteal flaps, bone was removed circumferentially around the distal root of mandibular second premolars and the mesial root of mandibular third premolars in five beagle dogs. The roots were completely denuded from the cementoenamel junction to the apex and curetted to remove PDL and cementum. Following root canal filling, the denuded roots on one side were conditioned with citric acid while the contralateral roots served as controls. To prevent bone-derived granulation tissue from contacting denuded roots, sheets of Nuclepore membrane were placed over the exposed bone margins and secured in place with steel ligatures. The flaps were coronally positioned and sutured. Histologic examination was made after three months of healing accompanied by regular plaque control. Both the experimental (acid conditioned) and control roots showed epithelium extending into the apical third of denuded roots and root resorption confined to the root apices. Some experimental specimens showed connective tissue adhesion in the apical third of roots without any new cementum or oriented fibers. Inflammatory cell infiltrate was seen extending to the apical third of denuded roots in both groups. In this model, the flap connective tissue cells failed to form new cementum and inserting fibers. Whether this was the result of inflammation and epithelial downgrowth or the inability of flap connective tissues to form new attachment could not be concluded from the study.