Abstract
Mandibular second molars with a single root canal present a distinctive anatomical variation. This case report aims to present a rare morphological variation of mandibular second molar characterized by a single canal diagnosed with a peri-apical radiograph and orthopantomogram. A 43-year-old Saudi Arabian woman was referred to the dental clinic complaining of discomfort and pain while chewing on the right back region of her mouth. A fixed partial denture was noted on clinical examination that spanned from the right mandibular second premolar (tooth #45) to the right mandibular second molar (tooth #47). The right mandibular second molar (tooth #47) had no mobility but was sensitive to percussion. The periapical radiograph revealed the existence of one root canal with apical radiolucency associated with this tooth. The final diagnosis of the tooth under consideration was pulpal necrosis with symptomatic apical periodontitis. This case confirms the presence of a single root and root canal in a second mandibular molar. Root canal treatment was done for the symptomatic tooth. Furthermore, longitudinal follow-up of the treated tooth for four years after the root canal procedure, both clinically and radiographically, demonstrated complete resolution of the peri-apical lesion. This case report unveils a unique and infrequent variation in the root canal system of a mandibular second molar: a single root associated with a single root canal. For optimal dental care management, clinicians must vigilantly acknowledge the potential for variations in the root canal systems of mandibular molars.

Key words: Mandibular molar, Single-root, Single canal, Case report, Root canal treatment