comparison of the danger zone thickness in the mesial canals of the mandibular first molar in cbct images at intervals of 3, 4, 5 mm below the orifice of the canal

background: the mandibular first molar teeth are the most common teeth that undergo endodontic treatment and are anatomically very challenging. adequate knowledge of the danger zone in the mesial root of the first mandibular molars helps reduce the risk of misdiagnosis of perforation during treatment. the aim of this study was to compare the dentin thickness of the danger zone in the mesial canals of the mandibular first molar in cbct(cone beam coomputed tomography) images at intervals of 3, 4, 5 mm below the orifice canal. methods: in this study, cbct images of 144 mandibular first molars from 74 patients aged 18 to 66 years were examined. mean orifice to furcation was calculated and mean distal dentin thickness of mesiobuccal and mesiolingual canals was measured at 3, 4 and 5 mm below the orifice. the mean thickness of the distal dentin was examined in terms of age, sex and maxillary side.results: the lowest mean distal wall thickness of mesiobuccal and mesiolingual canals was 5 mm below the orifice of the canal. the mean distal wall thickness of mesiobuccal and mesiolingual canals were higher in men than women (p <0.05). the mean distal wall thickness did not show a significant relationship with age. (p=0.745) except in the area of 3 and 5 mm below the orifice in the mesiobuccal canal which was significantly associated with age (p=0.01). no statistically significant difference was observed between the two mandibular sides (p=0.543) except in the 4 mm area below the orifice in the mesiolingual canal (p <0.05).conclusion: the present study showed that the danger zone is observed in the distal dentin of the mesiobuccal and mesiolingual canals of the mandibular first molar teeth in men and women 5 mm below the orifice of the canal. the mean dentin thickness of the distal wall was lower in women than in men.