الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 155 |  |  |
| | | from | 155 | | |
Abstract
The acquisition technique of the edentulous maxilla was evaluated. Two techniques were studied either desktop scanning of the physical impression or direct intraoral scanning of the arch for the construction of maxillary denture base. Twelve patients were recruited in this crossover study fulfilling the eligibility criteria to participate in this study and enrolled in both intervention and control groups.
Two digital maxillary denture bases were made for each patient using two different acquisition techniques and the same manufacturing technique. group I (Desktop scanning): The maxillae of the patients were captured indirectly by scanning the physical definitive impression extra orally by a desktop scanner. while group II (Intraoral scanning): the maxillae of the patients were scanned directly in their mouth by an intraoral scanner.
Primary impressions were made in properly selected and modified stock trays for group I (Desktop scanning). Definitive impressions were made in custom made acrylic trays with rubber base border molding and final wash impression. Maxillary and mandibular definitive Impressions were scanned before pouring by 3Shape E2 desktop Scanner to get the STL files for maxillary secondary impressions. The physical models and the mounted jaw relation for each patient were also scanned using 3Shape E2 Desktop Scanner.
For each Patient, the maxilla was scanned using an intraoral scanner (TRIOS 4 color, 3Shape A/S) in the same day before the conventional definitive impressions. 45˚degree manual finger retraction was used during scanning for retraction of lip and cheek muscles within the physiologic limit. The scanning followed a 4-swipe strategy for the maxillary ridge as follows: the center of the residual ridge from one tuberosity to the other on the opposing side, the palate with a zigzag path from one side to the other and toward the soft palate, the right buccal side, then the left buccal side.
The design of the denture bases was done using the Blender For Dental software. For each patient, two STL files were exported from the Blender Software, one for the denture base of physical impression group (group I) and the other for the denture base of intraoral scanning group (group II). Both were milled from pink pre-polymerized polymethyl methacrylate blanks by CORITEC 350i PRO, which is a 5-axis CNC milling machine.
A digital force meter device was used to evaluate the retentive force values of the upper denture bases, while the adaptation was evaluated by Geomagic Control X software.
It was found that both acquisition techniques produced clinically acceptable maxillary denture bases regarding retention and adaptation. However, the denture bases constructed from desktop scanning of definitive impression (group I) showed better retentive force values and less deviation from their reference model than intraoral scanning of the maxilla (group II).