The significance of coronal growth of periodontal ligament tissue for new attachment formation.

The present study was designed to examine whether coronal growth of granulation tissue originating from the periodontal ligament is a prerequisite for new attachment formation. In each of 4 monkeys, 1 central incisor and 2 first molars in the maxilla and the mandible were selected for experimentation. Angular bony defects were surgically produced to the mid-root level around each single root after crown resection and root separation of the multirooted teeth. The periodontal ligament tissue and the root cementum were removed to the bottom of the bony defects. In half the number of the teeth, an elastic ligature was placed tightly around each root at the bottom of the defects (test roots). In the remaining teeth, an elastic ligature was placed loosely around each root at the same level (control roots). All roots were subsequently covered by laterally displaced flaps. After 3 months of healing, the animals were sacrificed and the jaws removed and placed in fixative. Following decalcification, histological sections of the experimental roots and their surrounding periodontal tissues were produced. The histological analysis disclosed that new attachment had former to a level coronal to the elastic ligature in 10 of 14 control roots but in only 1 of 18 test roots. The results indicate that the repopulation of a detached root surface by cells from the periodontal ligament is a prerequisite for new attachment formation.