Cementoenamel junction: microscopic analysis and external cervical resorption.

There is a lack of data regarding the shapes and distribution of the mineralized tissue that composes the cementoenamel junction. A sample of 198 permanent human teeth was analyzed by optical microscopy and scanning electron microscopy. Scanning electron microscopy showed three types of tissue interrelations: enamel overlapped by cementum; enamel and cementum edge-to-edge; and a gap, revealing a strip of exposed dentin. Using optical microscopy, a fourth type of cementoenamel junction was observed: cementum overlapped by enamel. The distribution of the hard tissues found at the cementoenamel junction is unpredictable and irregular both for any tooth type (e.g. on cuspids) and on any one individual tooth. Based on these results and on analysis of the mechanisms involved in cervical root resorption, it is possible to consider the cervical region as prone to external resorption.