[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.