Oral Food Processing for Digitally Constructed Complete Dentures Versus Conventional Complete Dentures: A Randomized Crossover Study

Fourteen completely edentulous patients were participated in this study, their ages range from 50- 70 years. The participants were selected from Prosthodontics Department, Faculty of Dentistry, Mansoura University who are seeking for complete denture treatment. All participants will be completely edentulous for at least 6 months and have no previous experience with removable prosthesis. Subjects with temporomandibular joint disorders, head/neck injury, or with skeletal deformity were excluded from this study. All participants were Angel's class I maxillomandibular relation. Informed consent were written from each patient, and approval from the Faculty Ethical Committee will be obtained. The sample size was deter¬mined based on the number of chews for TOMASS test data from previous research. A computer software program (G*power, version 3.1.5, Kiel, Germany) was used for sample size calculation. 14 participants was detected with an effect size of 72%, 5% error probability, and 80% power.

Complete dentures construction:

At the first visit Direct intraoral scanning of both arches were performed with an intraoral scanner (TRIOS 3; 3Shape A/S). Cheek retractors were used to gently extend the movable soft tissues. The ridge crest were scanned first, followed by scans of the labial or buccal and palatal or lingual surfaces of the ridge. For the maxillary arch, the palate were additionally scanned. After establishing the overall contour in this manner, the remaining unscanned parts were scanned to finalize the complete arch scan. Subsequently, preliminary impressions were made with an irreversible hydrocolloid impression material.

At the second visit Definitive impressions will be made using auto-polymerizing acrylic resin custom tray. The tray will be traced using low fusing modeling green compound then zinc oxide eugenol impression will be taken. For the fabrication of conventional CDs, the record base will be fabricated with an auto-polymerizing acrylic resin. For the fabrication of digital CDs, the record base will be directly designed on the intraoral scan data by using a CAD software program (Dental System, v1.7.16.0; 3Shape A/S) and will be additively manufactured with a 3D-printing material (Next- Dent C&B; 3D Systems) and a 3D printer (NextDent 5100; 3D Systems). Following this, a wax occlusal rim were attached to the record base.

At the third visit Maxillo-mandibular relationship were recorded by using the record base and wax occlusal rim assembly with an occlusal relationship registration material for both groups, and appropriate artificial teeth will be selected. For the fabrication of digital CDs, the obtained inter-arch relationship were scanned with the intraoral scanner. Subsequently, the standard tessellation language (STL) files for both edentulous arches and the registered inter-arch relationship will be imported into a metrology software program (Geomagic Control X, v2018.0.1; 3D Systems). The maxillary portion in the STL file of the registered interarch relationship will be flipped normal, creating a new STL file, and the original maxillary edentulous STL file were superimposed over this new flipped file through a best-fit matching algorithm. The same procedure were followed with regard to the mandibular portion in the STL file of the registered inter-arch relationship. This procedure enabled accurate 3D orientation of the obtained intraoral scan data. Next, the border of the CDs will be set 1 mm shorter than the scan border within the CAD software program. The artificial teeth will be arranged virtually, and the trial dentures were additively manufactured with the3D-printing material (NextDent C&B; 3D Systems) and the 3D printer. For the conventional dentures the artificial teeth were arranged in the conventional manner.