<![CDATA[Introduction: Simultaneous pulpal and periodontal inflammation is referred to as an endo-periodontal lesion. (EPL). These lesions present severe diagnostic and therapeutic challenges due to their complex pathways of communication through dentinal tubules, lateral canals, and apical foramina. Standardized classification under the 2018 World Workshop framework is crucial to determining the localized prognosis, appropriate treatment sequencing, and long-term tooth preservation, especially for esthetically critical anterior teeth in young patients. Case Report: A 19-year-old male presented with severe localized periodontal destruction, dental carries, and masticatory discomfort in tooth #21. The tooth exhibited a lingering, non painful response to cold testing, was highly sensitive to percussion, and demonstrated Miller Grade 2 mobility. Deep site-specific periodontal pockets measuring 9 mm were recorded on both the mesial and buccal aspects. Radiographic examination revealed vertical bone destruction exceeding 80% of the root length. The patient-level diagnosis was Periodontitis Stage III, Grade B, with tooth #21 classified as an EPL Grade 3 (without root damage). Treatment was sequentially executed starting with Phase I periodontal therapy to resolve generalized inflammation and improve the Oral Hygiene Index Simplified (OHIS) from poor to good and endodontic treatment of tooth #21 (shaping, 2.5% NaOCl irrigation with passive ultrasonic activation, intracanal Ca(OH)2 medication for 14 days, hermetic lateral obturation, and composite coronal restoration). This was followed by Phase II Four weeks post-obturation, periodontal flap surgery was performed on the localized 3-wall intrabony defect, involving meticulous debridement, sterile saline irrigation, and localized topical application of 25% metronidazole dental gel. Discussion: At the 8-month follow-up, tooth #21 remained completely asymptomatic, and periodontal probing depths were significantly reduced to 3-4 mm on all aspects. Tooth mobility reverted to physiological levels (Grade 1), and the patient maintained excellent plaque control. Standardized periapical radiography confirmed substantial bone fill (increased radiopacity) in the vertical defect. The use of regenerative materials (bone grafting) was not necessary due to the osteogenic potential of the 3-wall defect geometry and the thorough elimination of the primary endodontic infection source. Conclusion: For complex EPL Grade 3 lesions associated with pulpal pathology, a coordinated, sequentially timed approach consisting of root canal disinfection followed by surgical flap debridement can achieve stable bone healing and successful long-term tooth preservation, avoiding the need for extraction in young individuals.]]>
