Effect of Scanning Techniques on Accuracy of Mandibular Fixed Detachable Prostheses

This prospective crossover clinical trial is designed to evaluate and compare the accuracy and passive fit of three different intraoral scanning techniques used for the fabrication of mandibular implant-supported fixed detachable prostheses in completely edentulous patients.

The study will include completely edentulous participants rehabilitated with four osseointegrated implants placed in the mandibular arch. Each participant will undergo digital implant impression procedures using three different scanning .

The three scanning techniques being compared are:

• Splinted Scan Bodies: Implant scan bodies will be splinted using composite resin before intraoral scanning.
• Horizontal Non-Calibrated Scan Bodies (IO Connect): Digital impressions will be obtained using the IO Connect horizontal scan body system.
• Auxiliary Geometric Devices: Digital impressions will be acquired using 3D-printed auxiliary geometric devices attached to the scan bodies to provide additional geometric reference landmarks during scanning.

Digital datasets generated from each scanning technique will be analyzed and compared. Verification jigs will be fabricated using CAD/CAM technology and clinically evaluated.

The primary outcomes of the study are scanning accuracy, assessed by measuring linear deviation (µm) and angular deviation (degrees) between implant positions obtained from the different scanning techniques, and three-dimensional surface deviation analysis, assessed through root mean square (RMS) values and median surface deviation obtained from STL file superimposition.

The secondary outcome is passive fit , which will be evaluated using the Sheffield one-screw test and intraoral periapical radiographic assessment.

The findings of this study will help identify the scanning technique that provides the highest accuracy and best passive fit for mandibular implant-supported fixed detachable prostheses and may contribute to improving digital workflows in complete-arch implant rehabilitation.

Inclusion criteria

• Completely edentulous patients with age between 40-60 years.
• Adequate bone height to fulfill the criteria for implant placement.
• Patients should have a class I Angle's classification.

Exclusion criteria

1-. Insufficient vertical inter-arch space to accommodate the restorative components.

• Presence of psychiatric or neurological conditions. 3. Any systemic diseases that may affect implant bone osteointegration.