Periodontal attachment responses to surgical injury in the cat. Removal of buccal bone with and without placement of foreign body at ligament periphery.

Recently, PDL progenitor cells were claimed essential for the establishment of new connective tissue attachment to root surface. To further test new periodontal attachment after surgical injury, portions of the buccal alveolar plate were removed from the canines of 4 cats. Removal of bone was carried out with or without removal of the underlying PDL, and in half of the experimental sites, dental amalgam was placed at ligament periphery. Tissue blocks were prepared for routine histologic evaluation (H & E) and specific collagen stains (Mallory Trichrome and Mallory PATH). Exfoliation of amalgam was noted in 6 experimental sites during the healing period. At all sites, plaque accumulation and marginal gingivitis were observed before sacrifice. Histologic observation demonstrated limited new connective tissue attachment to root surfaces at PDL periphery where bone, PDL and cementum had been removed. Where PDL was retained, connective tissue attachment was present which appeared to be the result of fiber interdigitation between root-inserted fiber ends and gingival wound edge fibers. "Blockage" of PDL cell migration by amalgam could not be well controlled. However, the placement of amalgam seems to have interfered with new connective tissue attachment and/or cementogenesis. In 5 specimens, root resorption had progressed into dentin. At these sites, collagen tufts appeared to arise from dentin. These tufts were in intimate contact with zones of dense inflammatory cellular infiltrate and connective tissue elements. We suggest that this observation may be a further tissue response to injury, namely: root resorption with the unmasking of dentinal collagen, which may finally lead to fiber interdigitation.