Comparison of the accuracy of the image registration methods for the impressions of edentulous jaws.

OBJECTIVE: The aim of present study was to investigate the accuracy of two registration methods, best fit alignment and manual multi-point alignment followed by global registration, used in edentulous jaw impressions. METHODS: Traditional complete denture impressions were taken via two methods: open-mouth and closed-mouth methods. The edentulous impression models, including maxilla:14 pairs and mandible:12 pairs, were scanned in the model scanner and saved in STL format. In the reverse engineering software Geomagic Control 2014, two registration methods, namely, best fit alignment and manual multi-point alignment combined with global registration, were used independently to align the open-mouth and closed-mouth impressions of the same patient, and the 3-dimensional (3D) deviation between the reference and test models was recorded. SPSS26.0, paired t test, significance criterion two-sided alpha = 0.05. RESULTS: The nominal value threshold area was less in the best fit alignment group (maxilla 48.58%, mandible 44.16%) than in the manual + global registration group (maxilla 70.55%, mandible 66.27%), maxilla P = 0.000 < 0.05, mandible P = 0.014 < 0.05. The root mean square (RMS), average positive deviation and average negative deviation of the best fit alignment group were greater than those of the manual + global registration group, there were significant differences in the maxillary (P < 0.05), but not significant difference in the mandibular (P > 0.05). CONCLUSION: The manual multi-point combined global registration method is more accurate than the best fit alignment used in the registration of edentulous jaw impressions and is more effective for the maxilla.