In-Vivo Comparison of Different Impression Methods in Complete Edentulous Upper Jaw

In this study, it was aimed to compare the impressions taken with different impression techniques for the production of tissue-supported complete dentures from individuals with complete edentulous upper jaws. For this purpose, 15 individuals with complete edentulism in the upper jaw were asked to participate in the study. In addition to agreeing to participate in the study after reading the consent form, these individuals should have been using tissue-supported complete dentures in the upper jaw for at least 3 months. They should also have healthy mucosa without local factors such as tissue hyperplasia, atrophic crests, allergic reaction, epulis fissuratum. A total of five final impressions will then be taken from these individuals in two sessions. Two of these impressions will be obtained with the traditional method and three with the digital method. The traditional impression group will include one-step (ALG) and two-step (ZOE) impression techniques. The digital impression group will include the digital impression taken when the artificial intelligence is deactivated (A.I OFF), the digital impression taken when the artificial intelligence is activated (A.I ON) and the modified technique (MOD). In the first appointment, the first impressions will be taken for the traditional and digital groups. Intraoral exclusion and isolation will be provided before the digital first impression. With the A.I mode of the intraoral scanner (TRIOS4; 3Shape A/S, Copenhagen, Denmark) deactivated, scanning will be performed in accordance with the scanning protocol recommended by the company. A metal stock tray suitable for the dental arch will then be selected for the preliminary impression of the traditional impression group. The impression will be taken in one step with irreversible hydrocolloid impression material. The impression will be digitized with the same intraoral scanner within the first 10 minutes after impression taking. Both impressions will be digitally transferred to the dental laboratory as stl data. Using computer aided design (CAD) software (Exocad DentalCAD 2.4 Plovdiv), an individual tray will be designed for the ZOE impression in the traditional group and a pedestal for the MOD impression in the digital impression group. The designs will be transferred to the computer aided manufacturing (CAM) unit and produced with a 3D printer using dental resin. The occlusal-rim (OR) will be prepared by adding wax on the base.

In the second appointment, the cheek and lips will be excluded in the same way before scanning. For A.I OFF and A.I ON, recordings will be taken when the artificial intelligence is deactivated and activated, respectively. Then, occlusal vertical dimension, intermaxillary relationship and aesthetic parameters will be determined with OR before scanning for the MOD group. Reference areas will be created on the buccal and palatinal walls to facilitate scanning of the OR. To avoid retention problems during scanning, a silicone-based impression material with a fluid consistency will be applied to the tissue surface of the OR and placed in the mouth. Scanning will be performed according to the protocol proposed by Lo Russo et al. For the traditional impression group, the ALG impression will be taken with a metal stock tray using irreversible hydrocolloid impression material in a single step. The impression will be digitized with an intraoral scanner within ten minutes of completion. Then, the edges of the individual tray for ZOE will be shaped with impression compound to ensure peripheral closure. The impression will be completed with zinc-oxide eugenol impression material. The impression will be digitized. These measurements will then be compared using a reverse-engineering program (Geomagic design X version 2016.1.0, 3D Systems Inc. Rock Hill, SC). Before the comparison, in the same program, the parts to be evaluated on the ZOE in the conventional group and A.I OFF in the digital group will be divided into regions. These areas will be divided into four sections as right and left vestibular region, postdam area, hard palate region, except for the A.I OFF-MOD comparison group. In the A.I OFF-MOD comparison group, it will include the right and left initial areas, including the areas where scanning starts in the second scan of the MOD method. In addition, all measurements will be compared in terms of the whole surface and all measurement boundaries including the whole measurement surface as one. The comparison groups are ZOE-ALG, ZOE-A.I OFF, A.I OFF-A.I ON, A.I OFF-MOD. The measurements in the comparison groups will be overlapped first with the initial alignment and then with the best fit alignment algorithm. All sections will be evaluated individually with the "3D compare" feature and the amount of deviation in the areas to be evaluated will be determined.