Endo-perio syndrome is a common name for pathologic conditions that affect both the pulp and periodontium. The pulp and periodontium closely communicate through embryologic, anatomic and functional relationships (4). That is the reason that all pathologic conditions of the pulp can directly and indirectly affect the periodontium and vice versa . Many various factors participate in developing the endo-perio syndrome. These factors can either be of microbial or non-microbial origin. Microbial pathogens are bacteria, viruses and fungi and their by-products, while non-microbial causes are inadequate endodontic treatment, coronal leakage, traumatic injuries, root perforations and development malformations (7). The pulp and periodontium communicate through the apical foramen, lateral and accesory canals such as through dentinal tubules. Communication is also possible through furcation canals, palatogingival, development and apical grooves and anachoresis (19). The most commonly used classification system for the endo-perio syndrome was suggested by Simon, Glick and Frank in 1972. The classification system includes five different categories: 1. primary endodontic lesions 2. primary endodontic lesions with secondary periodontal involvement 3. primary periodontal lesions 4. primary periodontal lesions with secondary endodontic involvement 5. true combined lesions (23)