Etiology and Classification of Endodontic-Periodontal Lesions

The periodontium and the dental pulp are closely associated, sharing embryonic, functional, and anatomical interrelationships. Consequently, the relationship of endodontic and periodontal lesions has stirred confusion and debate as dental practitioners have become gradually further aware of the possible associations between the periodontium and the dental pulp. Like other periodontal and endodontic pathologies, the main etiology of endodontic-periodontal lesions is infection caused by microbial pathogens. These lesions may be caused by endodontic infections that have spread coronally, thus involving the marginal periodontium; by marginal periodontal infections that have spread apically and subsequently affected the dental pulp; or by a combination of the above. These possible causes have led to the common classifications of these lesions that are based on the origin of the infection, i.e., primary endodontic lesions, primary periodontal lesions, and combinations of the above. However, it has been claimed that these common classifications are too academic and theoretical and may not be clinically practical. This chapter will review the etiological factors of endodontic-periodontal lesions, the common classifications of these pathologies, and will suggest a novel and clinically practical classification for these intriguing clinical scenarios.