Passive Fit of Implant-Supported Frameworks: Digital vs Conventional Impressions

Full-arch implant-supported fixed prostheses require a high degree of passive fit to avoid mechanical and biological complications. While digital impression workflows are increasingly used as alternatives to conventional splinted impressions, evidence directly comparing their clinical accuracy for complete-arch implant frameworks remains limited, particularly for the IO-Connect non-calibrated splinting system and the Reverse Scan Body technique.

Eight completely edentulous patients with at least four mandibular implants will be enrolled. Using a crossover design, each patient will undergo all three impression techniques: Group I (IO-Connect splinted scan bodies), Group II (Reverse Scan Body technique), and Group III (conventional splinted open-tray impression with polyvinyl siloxane and Type IV stone casts). For each technique, a corresponding implant-supported framework will be fabricated and evaluated for passivity of fit using the Sheffield one-screw test and periapical radiographs taken with a paralleling device to assess microgaps at the implant-framework interface.

Inclusion criteria

• Completely edentulous patients requiring full-arch implant-supported fixed prosthesis
• Age 35-70 years
• Adequate mandibular bone to place at least four implants without major grafting
• Ability to undergo digital scanning and radiographic evaluation
• Signed informed consent

Exclusion criteria

• Systemic conditions affecting healing (uncontrolled diabetes, immunosuppression)
• History of head/neck radiotherapy or bisphosphonate therapy
• Active oral infection or severe bruxism
• Strong gag reflex preventing accurate scanning
• Poor compliance or unwillingness to attend follow-up visits