Accuracy of Impression Techniques and Their Effect on the Passive Fit of Screw- Retained Bar Splinting Two Interforaminal Implants

Surgical guide will be designed for completely edentulous patients. It will be inserted into the patient's mouth, stabilized against the upper denture and secured in place. dental implants will then be placed.

For bar fabrication using the first impression technique, closed-top primary impressions will be made followed by open top secondary impression. Extraoral scanning of the impression will be done followed by digital fabrication of the bar.

For bar fabrication using the second impression technique, scanning of the lower arch will be done using Omnicam intraoral scanner. Scanning will be done by a single calibrated operator who is trained on intraoral scanning techniques.

Scan bodies will be then screwed to the implants and scanning will be done. Both scans will be previewed on the computer desktop and superimposed together. A Standard tessellation language file will be then exported, downloaded and previewed in Inlab Exocad software .Implant system and the bar design will be selected from the software library. Then, the Standard tessellation Language file will be exported to the milling machine and milling of Cobalt chromium bar will be done.

For bar fabrication using the third technique, splinting of scan bodies will be done followed by intraoral scanning of the lower arch.