LAUSR

tps://doi.org/10.1016/j.jds.2020.11. 91-7902/a 2020Association for Denta e CC BY-NC-ND license (http://creati C-shaped root configuration is most common in mandibular second molars, especially in Asian populations. When it comes to maxillary molars, the prevalence of C-shaped root configuration is only 1.1% for first molars and 3.8% for second molars; however, this low prevalence highly increases the complexity of treatment. The present article aimed to report a case of apical microsurgery on a left maxillary first molar (tooth 26) with C-shaped root configuration. A healthy fifty-year-old male, who had non-surgical root canal treatment on his tooth 26 several years ago, had suffered from a sinus tract on buccal gingiva of the tooth for a period of time. With diagnosis of chronic apical abscess of tooth 26, root canal retreatment was performed (Fig. 1A, B). During the treatment, cone-beam computed tomography (CBCT) scan was performed due to failure to locate and negotiate distobuccal and second mesiobuccal canal. The CBCT scan showed fusion between mesiobuccal, distobuccal, and palatal root of tooth 26 at the middle third, but the palatal root separated from the fused C-shaped root at the apical third, forming a semilunar buccal root and an isolated palatal root (Fig. 1F, G). Additionally, an extensive apical radiolucency associated with the buccal root and a small radiolucency associated with the palatal root apex were observed. The image also revealed severe obstruction in the apical 5 mm of