Follicular cysts of mandibular third molar teeth: radiological evaluation of enlargement.

To test the hypothesis that follicular (dentigerous) cyst enlargement arises from impeded tooth eruption, data from standardized Orthopantomographs of 30 uninfected, wholly intracortical cysts associated with mandibular third molar teeth were analysed. Cyst areas were measured with a computer-aided image analyser (Magiscan 2, Joyce Loebl, Gateshead, UK). Two size categories, small and large, each comprising 15 cases, were distinguished. These were correlated with the radiographic variables of cyst relationships to tooth crown, and angulation and nature of impaction of associated tooth. Cyst enlargement is most active in the third and fourth decades of life. Smaller cysts were associated with teeth impacted against adjacent tooth or bone, whereas larger cysts developed predominantly from horizontally angulated teeth intruded endosteally. These findings lend support to the haemodynamic concept of follicular cyst enlargement linked with dysfunctional eruptive forces.