Correlação entre o diâmetro dos canais de molares superiores e dimensões de diferentes instrumentos mecanizados, por meio de análise de imagens de microtomografia computadorizada

Abstract

The complex root canal anatomy of maxillary molars is one of the main challenges in Endodontics and may compromise the effectiveness of mechanized instrumentation. This study evaluated the largest and smallest diameters of the mesiobuccal (MB), distobuccal (DB), palatal (P), and mesiobuccal 2 (MB2) canals of maxillary molars, at every millimeter along the root, correlating them with the size and taper of mechanized endodontic instruments through micro-computed tomography (micro-CT) images. Seventy maxillary molars were scanned by micro-CT, and measurements of the largest and smallest diameters were performed using CTAn software, with 0 mm adopted as the cut corresponding to the complete closure of the apical foramen. Statistical analysis included the Shapiro-Wilk test, Friedman test, and pairwise comparisons with Bonferroni correction (p < 0.05). A progressive increase in diameters was observed in the apex-to-crown direction in all evaluated canals, with statistically significant differences along the cuts. In the MB canal, the largest diameter ranged from 0.38 to 1.34 mm and the smallest from 0.23 to 0.59 mm; in the DB canal, from 0.38 to 1.01 mm and from 0.21 to 0.59 mm; in the palatal canal, from 0.53 to 1.26 mm and from 0.32 to 0.95 mm; and in the MB2 canal, from 0.32 to 0.65 mm and from 0.17 to 0.25 mm. Cross-sections were predominantly circular in the apical region, especially in the palatal and DB canals, whereas the MB and MB2 canals showed greater flattening in the middle and coronal thirds. Correspondence with mechanized instruments varied according to root level, being determined by tip diameter at apical levels and by taper at coronal levels. It is concluded that instrument selection should be individualized for each root canal, since compatibility with the smallest diameter alone does not ensure complete preparation of the dentinal walls.