Abstract: Objective: To study the effects of different impression materials and methods on the three-dimensional shape of open-mouth impression and closed-mouth impression for complete denture. Methods: Seven patients with edentulous jaws were selected to take stock tray open-mouth impression with red paste irreversible hydrocolloid alginate, custom tray open-mouth impression, and closed-mouth impression. Three groups of stone models were obtained by optical scanning chamber and converted into STL. and imported into Geomagic control 2014 software for statistical analysis after registration to evaluate whether the model registration was consistent with the clinical status. Results: The nominal value was mainly distributed in the hard area of upper jaw, the main supporting area, and the secondary supporting area. The areas with large deviation were mainly distributed in the border seal area. There were significant differences in the border seal area of the maxillary (P<0.01) and in the lingual flange area of the mandible (P<0.05). Conclusion: Differences in the three-dimensional morphology between open-mouth and closed-mouth impressions are mainly present in the buccal and lingual maxillary border areas. The edges of alginate impressions with red paste are easier to stretch, and the occlusal pressure dose not significantly affect the three-dimensional morphology of the main and accessory ramus areas.

Key words: secondary impression, dental impression technique, three dimensional