Retention of Computer Aided Design and Computer Aided Manufacturing Titanium Versus Cobalt/Chromium Maxillary Single Denture Bases: A Randomized Clinical Trial.

The study will be carried out in the department of prosthodontics-cairo university. Patients will be selected from the out-patient clinic according to the inclusion criteria, The primary impression will be made with alginate (cavex-normal set) and will be border-molded to get the acceptable extension and border thickness, a tray will be prepared with self-activated acrylic resin over the study cast. A secondary impression will be made with heavy putty consistency as a border molding material and the final impression will be made with light rubber base (3M) impression material, Then Pouring of the final impressions with type 4 Hydrocal dental stone (Hydrocal Dental stone, Bayer, and Germany). Master casts will be optically scanned using 3 shape optical scanner. Duplication of master casts will be done using silicone duplicating material. Titanium and cobalt/chromium metallic bases will be milled using 3shape milling machine to cover the palate with mesh extension over the ridge. They will be tried intra-orally regarding sitting and stability. Occlusal rim will be set on titanium metallic base then face bow record will be recorded then mounting the maxillary master cast. Centric relation will be registered then mounting of the mandibular cast will be done. The same will be done for the duplicate cast with the Cobalt/Chromium metallic base. Then Setting of the anatomical teeth for both master casts then try-in stage will be checked intra-orally then packing of cast and duplicate cast with conventional heat cured acrylic resin (Dentsply, Dentsply limited, Weybridge, Surrey. England) after flasking each denture will be finished.

The dentures will be delivered, then the assessment will be immediately and after 1 week then after 3 months that a hook screw with its nut (Digital force gauge instrument, model 475044) will be secured in the polished mid-palatal surface of the upper denture using metallic adhesive to record the amount of the force required for dislodgment. The pull end of the digital force gauge device will be connected to the hook positioned at maxillary dentures for one type of the two dentures and will be pulled vertically until denture dislodgement occurred, then the patient will take off his first type of denture for 2 weeks as a washout period then the second type of denture will be delivered and the same assessment will be done.