Some considerations on the role of cementum in periodontal disease.

The protective role of cementum against root resorption is discussed in relation to buried teeth, orthodontic treatment, replantation and periodontal disease. The essential feature seems to be a layer of partially calcified precementum or vital cementoblasts. Root resorption close to the epithelial attachment, although not common, is probably the result of death of cementoblasts caused by irritants from bacterial plaque, and the presence of severe of prolonged inflammation. Cementum exposed in the pocket can be affected in different ways by these irritants, and rendered unacceptable for re-attachment to periodontal tissue. Successful re-attachment procedures involve either the removal of the affected cementum or its treatment with agents partially to decalcify such as acids, or detoxify by phenol for example. Examples of treatment embodying some of these principles are illustrated by two case histories of localised gingival recession and one of intra-bony pocketing associated with an acute lateral periodontal abscess. In this case a follow-up radiograph taken 16 years later is presented as evidence of the permanence of repair which can be achieved. Root resorption which often follows the use of fresh autogenous bone from the ilium is then discussed and the conclusion reached that the vital cells in the transplant discourage the migration of cementoblasts from the adjacent periodontium. The cementum and dentine thus remain unprotected and susceptible to resorption.