Electron microscopic study of the regeneration of cementum and periodontal connective tissue attachment in the cat

Regeneration of periodontal connective tissue attachment was studied at the ultrastructural level in cats following the removal of cementum and superficial dentin through a surgically created fenestration in the facial alveolar plate. Non-decalcified specimens were examined 33, 45, 70, and 105 days after surgery. In early stages of healing, fibroblasts were aligned parallel, and immediately adjacent, to the cut, irregular dentin surface; subsequently, collagenous matrix formation was observed at this site. Some regions of the defects showed surface demineralization and extension of collagen into dentinal tubules. The first indication of cementum mineralization was the deposition of small crystallites along the irregularities of the dentin surface. After further development, a well-defined zone containing c1osel packed crystallites was usually evident at the new dentin-cementum junction. Peripheral to this, collagen orientation in the calcified cementum was primarily parallel to the tooth surface, with some perpendicular orientation suggestive of Sharpey's fiber formation. Collagen-mineral patterns typical of the normal cementum surface were observed, and cementoblasts were seen in various stages of inclusion into the calcified matrix. Where the injury had not reached the dentin, collagen fibrils of new and old cementum were interwoven, and the junctional region demonstrated incomplete mineralization.