Aim: To measure the root canal area and the reduction of the mesial and buccal/lingual wall thickness at the level of the coronal interference in mesial roots of mandibular molars after instrumentation with a crown-down or a simultaneous root canal preparation technique.
Methodology: Twenty mesial roots of first mandibular molars with a moderate root canal curvature were embedded in resin and sectioned horizontally at the level of the coronal interference, using a modification of the Bramante technique. After scanning and processing, the sections were reassembled. One root canal of each root was prepared using ProTaper instruments, while Mtwo instruments were used in the other root canal of the same mesial root. After scanning and processing, the data obtained were analysed for two parameters: changes in root canal area after instrumentation (Delta A) and reduction of the mesial and buccal/lingual wall thickness (Delta T). The data were subjected to Student's t-tests for statistical analysis at a significance level of P < 0.05.
Results: No statistically significant differences were found between the two groups with respect to the changes in the areas (Delta A) at the level considered (P = 0.410). No statistically significant differences were noticed between the two groups for dentine thickness (Delta T) of both the mesial wall (P = 0.077) and the buccal or lingual wall (P = 0.171).
Conclusions: There was no difference between the ProTaper and Mtwo groups for the amount of dentine removed.