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[Computer aided design and 3-dimensional printing for the production of custom trays of maxillary edentulous jaws based on 3-dimensional scan of primary impression].

OBJECTIVE
To establish a digital method for production of custom trays for edentulous jaws using fused deposition modeling (FDM) based on three-dimensional (3D) scans of primary jaw impressions, and to quantitatively evaluate the accuracy.


METHODS
A red modeling compound was used to make a primary impression of a standard maxillary edentulous plaster model. The plaster model data and the primary impression tissue surface data were obtained using a 3D scanner. In the Gemomagic 2012 software, several commands were used, such as interactive drawing curves, partial filling holes, local offset, bodily offset, bodily shell, to imitate clinical procedures of drawing tray boundary, filling undercut, buffer, and generating the tray body. A standard shape of tray handle was designed and attached to the tray body and the data saved as stereolithography (STL) format. The data were imported into a computer system connected to a 3D FDM printing device, and the custom tray for the edentulous jaw model was printed layer upon layer at 0.2 mm/layer, using polylactic acid (PLA) filament, the tissue surface of the tray was then scanned with a 3D scanner. The registration functions of Geomagic 2012 was used to register the 3-dimentional surface data, and the point-cloud deviation analysis function of the Imageware 13.0 system was used to analyze the error. The CAD data of the custom tray was registered to the scan data, and the error between them was analyzed. The scanned plaster model surface was registered to the scanned impression surface and the scanned tray data to the CAD data, then the distance between the surface of plaster model and the scanned tissue surface of the custom tray was measured in Imageware 13.0.


RESULTS
The deviation between the computer aided design data and the scanned data of the custom tray was (0.17±0.20) mm, with (0.19±0.18) mm in the primary stress-bearing area, (0.17±0.22) mm in the secondary stress-bearing area, (0.30±0.29) mm in the border seal area, (0.08±0.06) mm in the buffer area; the space between the tissue faces of the plaster model and the scanned tissue surface of custom tray was (1.98±0.40) mm, with (1.85±0.24) mm in the primary stress-bearing area, (1.86±0.26) mm in the secondary stress-bearing area, (1.77±0.36) mm in the border seal area, (2.90±0.26) mm in the buffer area.


CONCLUSION
With 3D scanning, computer aided design and FDM technology, an efficient means of custom tray production was established.