Biting Force and Chewing Efficiency of Complete Dentures.

The aim of this study was to compare the MBF and chewing efficiency of complete denture bases fabricated by conventional, 3D printing and milling techniques. The research hypothesis was that, there are no signiﬁcant differences in MBF and chewing efﬁciency in complete dentures fabricated by the three methods.

Participant selection and treatment This study will include a clinical experiment with a cross-over clinical trial design. For this study, 27completely edentulous participants with age range of 50-65 were selected from the outpatient clinic of the Removable Prosthodontic Department, Faculty of dentistry, Kafr Elsheikh University, Egypt. All participants had Angle class I jaw relation maxillomandibular relationship, normal alveolar ridge volume, no temporomandibular joint disorders, no heart disease, and no systemic diseases that affect the complete denture treatment procedures.

To reduce the effect of order of treatment on MBF, were successively given the following prosthesis i) complete dentures fabricated by the conventional technique ii) 3D printed complete dentures iii) milled complete dentures in a random order.

Construction of the CADCAM 3D printed denture The same steps of the conventional technique will be performed till the adjustment of occlusion rims then in the dental laboratory, the maxillary and mandibular definitive casts and the occlusal rims will be prepared for scanning with scan spray. Scanning will be performed with an optical 3D scanner . The files from the laser-scan will be translated into stereolithography (STL) files and the CDs are virtually designed in ExoCad software. After minor modifications in the positions of teeth were made, fabrication of the dentures will be approved and the digital denture base will be fabricated using 3D printing technique from Dental Pink resin

Construction of the CAD/CAM milled denture Once the complete denture has been virtually designed in CAD software (ExoCad software) a preview will be sent for evaluation using 3D viewing software. After minor modifications in the positions of teeth were made, fabrication of the dentures will be approved. The digital denture will be fabricated by the command software of the milling machine (ExoCad 5x milling machine) from prepolymerized resin acrylic pucks and the teeth (TSM Acetal Dental) were milled into template .After that the denture will be finished and polished according to the traditional procedures For all groups, after placement, clinical evaluations of the fit, retention, stability, occlusal relationship, esthetics, and phonetics were performed. Assessment of the occlusion was made with articulating paper, chairside adjustments were made and premature contacts were corrected. The patient was given a proper program for denture insertion and oral hygiene measures.

Assessment of biting force

* This will be made by using a custom-made device composed of Flexiforce A 301® force sensor and Arduino microcontroller with a crystal display. The sensor is calibrated by known weight object for several times, and the sensor is covered by 3 mm layer of putty rubber base material.
* Readings will be performed at 1 week, 1 month and 3 months follow-up periods. Assessment of chewing efficiency The chewing efﬁciency will be evaluated according to the procedure described by Schimmel et al. (2007) using a chewing gum. Specimens will be prepared from two colored gums one with the ﬂavor "Sour Berry" (white color) and the other with the ﬂavor "Fancy Fruit" (orange color). Two strips of a standard size (30 9 18 9 3 mm) will be cut from each gum and manually stuck together. Patients will be instructed to chew ﬁve samples of gum on their preferred chewing side for 5, 10, 20, 30 and 50 cycles, respectively. Between the different tests, an interval of at least 1 min will be imposed to reduce the effect of fatigue. The total duration of the experiments was approximately 8 min.

After chewing, the samples will be then spat into transparent plastic bags, which The samples will be then scanned from both sides with a of resolution 500 dots per inch. The numbers of selected pixels will be recorded from the histogram for each side, and mean of those ﬁgures will be calculated. To assess the reproducibility of chewing, the subjects will be available to repeat the experiments on a different day.

Eligibility Criteria:
Inclusion Criteria:

* Angle class I jaw relation maxillomandibular relationship
* Normal alveolar ridge volume
* No temporomandibular joint disorders
* No heart disease
* No systemic diseases that affect the complete denture treatment procedures

Exclusion Criteria:

* Abnormal jaw relation
* TMJ disorders
* Any systemic disease interfering with complete denture treatment