Void Volumes in Obturated Root Canals Viewed by X-Ray Microtomography

Objectives:  To compare total void volume percentage left within root canal filling in maxillary premolars detected using microtomography at two resolutions of 15 and 30µm voxel side‑length, to determine whether the higher resolution would improve sensitivity in detecting void volume percentage with the associated longer scanning‑time. This study is part of a larger project comparing voids left after root canal obturation with different techniques. In order to maximize utilisation of the limited recourses of the experimental equipment, there was a need to assess the disparity in void volumes captured at two different resolutions.

Methods:  14 extracted human upper premolars were prepared with Pro‑Taper (Dentsply Maillefer, Switzerland) and  randomly filled with either Lateral Condensation of master GP points (LC,  n=7,  Kerr, U.K. Ltd.) or the Continuous Wave technique (VC, n=7, using System B and Obtura III). Tubliseal (Kerr, Italy) was used as the sealer. Void volume percentages were compared between the X-ray microtomography scans taken for each tooth at two resolutions.

The teeth were scanned post‑instrumentation at 30µm voxel side-length to define the space left to be filled. Teeth were then scanned post-obturation with 30µm and 15µm voxel side-length, from which the filled areas were calculated. The percentage of total void volume for each sample was quantified using custom software. The data were statistically analysed (non-parametric test, p<0.05).

Results: There was a statistically significant difference in void volume percentage between 15µm (1.83±0.85 and 6.25±1.89) and 30µm (1.25±0.47 and 5.59±1.49) in both LC and VC respectively.

Conclusions: Improving resolution (15µm) shows better detection of voids left after root canal obturation. However, the difference between the two groups was not better resolved at 15µm and thus 30µm was considered sufficient to measure relative void volume (as a function of technique) even though the total volume may be underestimated.