Accuracy of different definitive impression techniques with the all-on-4 protocol

Area of Science:

• Dental implantology
• Prosthodontics
• Digital dentistry

Background:

• A passive fit of implant-supported restorations is crucial for long-term success.
• Limited data exists on the fit accuracy of various impression techniques for the all-on-4 protocol.

Purpose of the Study:

• To digitally evaluate and compare the accuracy of four impression techniques for the all-on-4 protocol.
• To assess the impact of different angulations of distal multiunit analogs on impression accuracy.

Main Methods:

• Four maxillary definitive cast models with multiunit analogs at varying angulations (0-30 degrees) were used.
• Four impression techniques (closed tray without cap, closed tray with cap, splinted open tray, sectioned resplinted open tray) were tested (n=10 each).
• Definitive and duplicate casts were scanned, and angular/linear deviations were calculated using specialized software.

Main Results:

• Open-tray techniques demonstrated reduced linear and angular deviations compared to closed-tray techniques in angulated groups.
• Increased angulation of posterior analogs led to higher deviations with closed-tray methods.
• Mean angular deviations ranged from 0.03 to 0.16 degrees; linear deviations ranged from 0.10 to 0.75 mm.

Conclusions:

• Open-tray impression techniques provide superior accuracy for the all-on-4 protocol, particularly with angulated posterior implants.
• The angulation of posterior implants significantly influences the accuracy of closed-tray impression techniques.
• Digital evaluation aids in understanding and optimizing impression techniques for complex implant restorations.