Pathogenesis of apical periodontal cysts: guidelines for diagnosis in palaeopathology

Apical periodontal cysts are benign lesions developing in relation to the apices of non‐vital teeth due to inflammatory response from the infective pulp. These are epithelium‐lined bony cavities containing fluid. Despite being widely reported in medical/dental literature, this common condition is poorly diagnosed and documented in the archaeological literature. We aim to clarify the correct terminology, demonstrate bony manifestations at different stages of pathogenesis of chronic periapical dental lesions into granuloma and apical periodontal cysts, and to describe diagnostic criteria which would provide practical guidelines for the diagnosis of these conditions. Three identified skulls from the International Exchange Collection, housed in the Anthropological Museum at the University of Coimbra, are used to identify the progression of this condition from a small periapical granuloma to a large apical periodontal cyst with expansion of alveolar and facial bones. The pathogenesis of this condition is described, together with its surgical management in the early 20^th century in Portugal, which is the period in which these individuals lived. Confusion resulting from the different terminologies can be avoided if the term periapical granuloma is used to define apical bony lesions smaller than 3 mm at their maximum intra‐bony diameter, and the term apical periodontal cysts for the larger lesions. We recommend that these terminologies and parameters be used as a standard in future studies. This will make inter‐observer and inter‐population comparisons more accurate. Copyright © 2007 John Wiley & Sons, Ltd.