Comparison of Two Techniques for Selection of Master Gutta-Percha Cone Using Micro-Computed Tomography

This study used micro-computed tomography (micro-CT) to evaluate the fit of the master gutta-percha cone at time of cone fit, gutta-percha volume in the filling material, and the filling material volume in relation to the canal at the apical limit of the working length. Root canals of 20 maxillary central incisors were prepared with rotary instruments and distributed into two groups (n=10). The gutta-percha cone tip was either plasticized (apical thermal impression technique - ATI) or not (conventional technique - CT), and its apical fit was checked. The apical 1 mm of working length was examined with a micro-CT, canals were filled with gutta-percha and sealer, and new micro-CT scans were obtained. In CT, gutta-percha filled 35.83 ± 15.05% of the canal at cone selection and 38.72 ± 11.64% after filling. In ATI, these values were 23.14 ± 7.74% and 26.98 ± 20.40%, respectively. Gutta-percha volume in the filling material, and filling material volume in relation to the canal were, respectively, 61.28 ± 11.64% and 87.76 ± 9.98% for CT, and 73.00 ± 20.41% and 89.96 ± 9.08% for ATI. No significant difference was found between cone selection and after canal filling, for either CT (p=0.593) or ATI (p=0.4975). The techniques did not differ significantly with respect to gutta-percha volume in the filling material (p=0.132) and filling material volume in relation to the canal (p=0.612). An ideal fit of the master gutta-percha cone at working length was not achieved regardless of the cone selection technique, and the material-filled area was similar for both techniques. Este estudo utilizou microtomografia computadorizada (micro-CT) para avaliar a adaptação do cone de guta-percha no momento da sua seleção, o volume de guta-percha no material obturador, e o volume do material obturador em relação ao canal no limite apical do comprimento de trabalho. Canais radiculares de 20 incisivos centrais superiores foram preparados com instrumentos rotatórios e distribuídos em dois grupos (n=10). A ponta do cone de guta-percha foi plastificada (técnica de impressão térmica apical - TIT) ou não (técnica convencional - TC), e seu ajuste apical foi verificado. O milimetro apical do comprimento de trabalho foi examinado em micro-CT, os canais foram preenchidos com guta-percha e cimento, e novas imagens em micro-CT foram obtidas. Na TC, a guta-percha preencheu 35,83 ± 15,05% do canal no momento da seleção do cone e 38,72 ± 11,64% após a obturação. Na TIT, estes valores foram de 23,14 ±