Discrepancy in Root Apex Closure Timing of Maxillary First Molars: CBCT Study

This study determined whether there are differences in the timing of apical closure in maxillary first molars among different roots and investigated the chronological age at which each root reaches a closed apex. This study included 155 boys and 158 girls. Radiographs of Korean children aged 7 - 11 were recorded. Using cone-beam computed tomography (CBCT) images, the apical diameters (AD) of the mesiobuccal root (MB), distobuccal root (DB), and palatal root (P) of the left and right maxillary first molars were measured using the INFINITT PACS software. We examined whether the mean AD was significantly smaller than 0.5 mm. The age at which the AD was significantly smaller than 0.5 mm was 9 for the MB and DB of the maxillary first molars (p < 0.0001) and 11 for the P (p < 0.0001). The results were consistent for both the left and right sides. We proposed 0.5 mm as an apical diameter criterion for an open apex. When the age of apical closure of the maxillary first molars, which is difficult to observe on panoramic and periapical radiographs, was investigated using CBCT, it was observed that the age of apical closure was 9 for the buccal roots and 11 for the palatal roots, indicating a difference of 2.