[Study of the mucosal morphological difference of distal-extension of mandibular dentition defect impressions taken by intra-oral digital scanning and selective pressure impression technique].

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.

[Study of the morphological difference of upper jaw impressions taken by intra-oral digital scanning and functional impression technique].

PURPOSE: To compare the difference in distal-extension models taken by intra-oral digital scanning and functional impression technique. METHODS: Twenty patients with dentition defect in upper jaw, including 10 Kennedy Ⅰ defect and another 10 Kennedy Ⅱ defect, were chosen to treat with intraoral digital scanning and functional impression technique respectively. Laboratory cast scanner was used to scan the plaster casts made from the functional 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 functional impression from the same patient were compared by Geomagic Qualify 12 software, and the trueness of the difference on free end morphology were analyzed. Paired t test was used to analyze the difference of the alveolar mucosa variable with SPSS 20.0 software package. RESULTS: There was no significant difference between the group of Kennedy I defect and Kennedy Ⅱ defect(P>0.05） regarding the two methods of impression. All the cases presented the tendency that with distance from distal teeth increasing, the average RMS also increased. CONCLUSIONS: Whether using intra-oral digital scanning or functional impression technique, the type of dentition defect was not obviously related to the difference of RMS in distal-extension tissues. In addition, there is positive correlation between the length of distal-extension edentulous area and difference of RMS, which needs further studies with more cases.