IADR Abstract Archives
Influence of sample size on micro-computed tomography
Objectives: The aim of this study was to compare mineral concentration of whole sound human teeth and 6-mm samples, at different integration-time, by micro-computed tomography (micro-CT).
Methods: A commercial polychromatic fan-beam micro-CT (µCT20; SCANCO Medical AG; Switzerland) was operated at 50kVp, 160µA, 30µm (spatial-resolution) and 250ms (integration-time). Ten crowns of caries-free human molars were divided into two experimental groups: whole-crowns samples(G1) and 6-mm thickness cut samples(G2). All samples were scanned with 1mm aluminium-wire (99,999%-purity) for calibration purpose. Mean mineral concentration was calculated for all groups after selection of enamel by regions of interest. Student t test was used to measure the significance between groups (p<0.05). The experiment was repeated enhancing integration-time to 350ms. Nevertheless, group G1 at 350ms was eliminated of statistical analysis due to high level of artefacts on all images, except by one. Noise level was estimated calculating coefficient of variation from linear attenuation-coefficient at one voxel of aluminium-wire after six consecutive scan procedures at 250ms and 350ms.
Results: The values of mineral concentration between G1 and G2 at 250ms showed no statistically significant difference (p=0.151). When the effect of integration-time was evaluated on G2 at 250ms and 350ms, the difference found was at the borderline of statistical significance (p=0.071). The noise level at 250ms and 350ms was estimated to be 0.40 and 0.13.
|
|
Mineral Concentration (g/cm3) |
|
|
Integration-time |
250ms |
350ms |
|
G1-whole teeth |
2.60 (±0.09) |
2.66 (n=1) |
|
G2-6mm samples |
2.69 (±0.07) |
2.76 (±0.03) |
Conclusion: Although results showed no statistically significant differences, absolute values from G2 (350ms) were in very good agreement with mineral concentration from the literature. The use of higher integration-time resulted on lower noise level. The suggested approach for quantitative experiments, by using this commercial micro-CT, is the use of 6-mm samples at 350ms of integration-time with the specified set conditions.
Luedemann, T.N.R.C is supported by CAPES/Brasília-Brazil.