Abstract: PURPOSE: To compare the mucosal morphological difference in distal-extension area of mandibular dentition defect taken by intra-oral digital scanning and selective pressure impression techniques. METHODS: Seventeen patients with Kennedy Class I and Class II dentition defect in lower jaw were included, including twenty-two distal-extensions. Intraoral digital scanning and functional impression technique were taken in each patients, respectively. Laboratory cast scanner was used to scan the plaster casts made from the selective pressure impression to obtain the three-dimensional data. All the data were stored in STL format. The 3D data collecting from intra-oral digital scanning and selective pressure impression from the same patient were compared by Geomagic Control 2014 software. Root mean square of 2.5mm diameter area was calculated in 5,10,15 mm from terminal tooth. Pearson's correlation test was used to analyze the correlation of the distance and morphological difference with SPSS 20.0 software package. RESULTS: Mean mucosal morphological difference of jaw distal-extension edentulous area taken by intra-oral digital scanning and selective pressure impression techniques was (0.37±0.12) mm. There was positive correlation between distance from terminal tooth and mucosal morphological difference(P<0.05). Morphological differences in 5, 10, 15 mm from terminal tooth were (0.14±0.11) mm, (0.22±0.13) mm and (0.39±0.16) mm, respectively. CONCLUSIONS: In this study, there was positive correlation between the length of distal-extension edentulous area and mucosal morphological difference, while the kind of ridge defect and mucosal thickness may also affect the morphological difference quantity.

Key words: Intra-oral digital scanning, Selective pressure impression, Dentition defect, Distal extension