Diagnosis, prognosis and decision-making in the treatment of combined periodontal-endodontic lesions.

Exposed dentinal tubules in areas of denuded cementum may serve as communication pathways between the pulp and periodontal ligament (Fig. 1). Exposure of dentinal tubules may occur due to developmental defects, disease, or periodontal procedures. In the root, dentinal tubules extend from the pulp to the dentinocemental junction (73). They run a relatively straight course and range in size from 1 to 3 mm in diameter (126). The diameter of the tubules decreases with age or as a response to a continuous low grade stimuli by the apposition of highly mineralized peritubular dentin. The number of dentinal tubules varies from approximately 8,000 at the dentinocemental junction to 57,000 per square millimeter at the pulpal end (126). In the cervical area of the root there are about 15,000 dentinal tubules per square millimeter (73). These tubules may be denuded of their cementum coverage as a result of periodontal disease, surgical procedures or developmentally when the cementum and enamel do not meet at the cemento-enamel junction (CEJ) thus leaving areas of exposed dentin. Patients experiencing cervical dentin hypersensitivity are an example of such a phenomena. Scanning electron microscopic studies have demonstrated that dentin exposure at the CEJ occurrs in 18% of teeth in general and in 25% of anterior teeth in particular (132). Furthermore, the same tooth may have different CEJ characteristics with dentin exposure on one side while the other sides are covered with cementum (162). This area becomes important in assessing the progression of endodontic pathogens (Fig. 2), as well as the effect of root scaling and planing on cementum integrity, and bleaching-induced root resorption following the use of 30% hydrogen peroxide (50, 78, 153, 154). Other areas of dentinal communication may be through developmental grooves, both palatogingival and apical (173).