Methods: twenty-seven permanent extracted human maxillary first molar were evaluated by using the microCT analisys (SkyScan 1072, SkyScan b.v.b.a., Aartselaar, Belgium). A scanning procedure was completed for all teeth using 100 kV, 98 µA and 15× magnification resulting in a pixel size of 19.1 × 19.1 µm (axial cross-sections), whit thickness of 38.0 µm. In all teeth were analysed and recorded number and type of root canals and apical foramina, presence of accessory canals, loops, prevalence of isthmuses and of intercanal connections, distance between radiographic and anatomic apexes.
Results: The most frequent pattern was three canals (59%) followed by four canals (41%) . Comunications between MB1 and MB2, isthmuses and intercanal connections were found mainly in the coronal and middle part of the root (63%; 55.5%), whereas accessory canals and loops were mainly found in apical third of the root (59%). Three separate apical foramina were present in 63% of the specimens, four apical foramina were present 26% of the time and in other 11% of the cases was present an apical delta. The mean distances between anatomic and radiographic apexes were 0.42±0.14 in mesiobuccal root, 0.27±0.23 mm in distobuccal root and 0.55±0.27 mm in palatal root.
Conclusions: Within the limitations of this study, it can be concluded that the maxillary first molars showed significant anatomical variations. The location and identification of the root canals were facilitated by micro-computed tomographic analysis.