Management of a Rare 4-Rooted Maxillary First Molar With 5 Canals and an Endo-Periodontal Lesion: A Case Report.

BACKGROUND Endo-periodontal lesions (EPL), particularly those manifesting as primary periodontal lesions with secondary endodontic involvement, pose unique clinical challenges when accompanied by odontogenic maxillary sinusitis (OMS). Furthermore, limited case reports document the nonsurgical management of such complex conditions in maxillary molars exhibiting rare multi-rooted and multi-canal variations (prevalence <0.103%). CASE REPORT A 31-year-old woman presented with pain and grade III mobility in the right maxillary first molar, with an intact crown, a deep palatal periodontal pocket, and a negative cold testing response on clinical examination. Periapical radiography indicated multi-rooted anatomy and extensive bone loss, and cone beam computed tomography (CBCT) confirmed 4 separate roots (mesiobuccal, distobuccal, mesiopalatal, distopalatal), a fifth centrally located pulp chamber canal orifice, a periapical lesion communicating with a periodontal defect, and ipsilateral maxillary sinus mucosal thickening. Nonsurgical root canal treatment for all 5 canals was performed under a dental operating microscope with ultrasonic activation (3% NaOCl) and bioceramic sealer, combined with concurrent supportive periodontal therapy. At the 8-month follow-up, the tooth was asymptomatic with reduced mobility and probing depths; CBCT revealed marked reduction in periapical lesions and significant improvement in maxillary sinus mucosal thickening (ENT consultation advised). CONCLUSIONS This case unequivocally demonstrates that meticulous nonsurgical endodontic treatment with ultrasonic activation and bioceramic sealer, in conjunction with targeted periodontal therapy and occlusal management, is a highly effective tooth-preserving strategy for maxillary molars with complex anatomic variations complicated by primary periodontal lesions with secondary endodontic involvement and secondary OMS, achieving excellent clinical and radiological outcomes.