A deep understanding of the relationship between root morphology and periodontal destruction is crucial to successful periodontal care. Most mandibular molars have two roots (one mesial and the other distal) and three canals. The major variant of this tooth type is the presence of an additional third root distally or mesially or a supernumerary lingual root. This article presents a case report of a 14-year-old girl with mandibular first molar having three roots bilaterally which is contributing to the periodontal destruction. There were three walled defect distal to first molar with Grade II furcation involvement distally. Regenerative surgeries were performed and patient was kept under maintenance. The relationship between additional third root and periodontal destruction seldom has been described clearly. This paper has been presented in 34(th) national conference at Dharwad.