The aim of this study was to compare the intra-examiner reliability of measurements made on plaster cast and dental digital models.
Material and methods: Five young patients with different occlusal patterns were selected and their dental casts and corresponding digital models were obtained. Twenty expert orthodontists were asked to measure two times both the traditional and digital models. The measurements taken included: lower inter-canine distance, lower inter-molar distance, lower right first molar mesio-distal length, lower right lateral incisor mesiodistal length and overbite. The absolute differences between the two sets of repeated measurements were computed for each of the five couples of parameters and compared with Student's paired T tests.
Results: Four parameters showed no statistical difference when the error of measurement of the traditional models was compared to the error of measurement of the digital models. They where the lower inter-canine distance (p = 0.11), the lower inter-molar distance (p = 0.24), the lower right first molar mesio-distal length (p = 0.4), the lower right lateral incisor mesio-distal length (p = 0.39). On the contrary, the error of measurement for the overbite was lower (P < 0.001) for digital models (Mean = 0.24, SD = 0.21) compared to traditional models (Mean = 0.69, SD = 0.53).
Conclusions: Digital and traditional casts offer the same intra-examiner reliability in most cases, but for some measurements, when digital cross sections could help, digital models seem to produce a smaller error.