Methods: 99 extracted human upper premolars were prepared using Pro‑Taper Ni-Ti (Dentsply‑Maillefer, Switzerland), and obturated using one of the following techniques: lateral condensation of master GP points (LC n=33, Kerr, U.K. Ltd. & Dentsply‑Maillefer, Switzerland), continuous wave technique (CW, n=33, using System B and Obtura‑III), or single cone technique (SC, n=33) with Tubliseal (Kerr, Italy).
Teeth were scanned using the in-house designed MuCAT2 XMT scanner post‑instrumentation and post‑obturation at 30 µm voxel side length. The two scans were superimposed and the percentage of total void volume within the root canal space was measured for each sample, and the patterns, sizes, and frequencies of the voids were assessed 3-dimensionally using custom software. Data were statistically analysed (non-parametric test, significant level at p<0.05).
Results: Pattern, size and frequency of voids were different in canals obturated by the three techniques. There was a significant difference in void volume percentage among the three filling techniques. SC had significantly higher total void volume (1.86%) than LC (0.75%), while CW (0.55%) had significantly the least total void volume.
The majority of teeth that presented with a void at the apical regions were from the SC group (14 teeth) followed by LC and CW (6 and 5 teeth respectively).
Conclusion: XMT, being a non-destructive technique, allows 3‑dimensional, sequential investigations. This technique can be regarded as the current gold standard for in vitro investigations of RCT with regard to void quantification, allowing current and future obturation techniques to be properly assessed.