[Influence of implant depth and scanning rod length on accuracy of digital impression for mandibular posterior single-tooth implant restoration].

Objective: To study the influence of implant depth and scanning rod lengths on the accuracy of digital impression for single-tooth implant restoration of the mandibular posterior teeth.

Methods: Five standard dental cast models with missing right mandibular first molar (46) were prepared with the subgingival implant depths of 0, 1, 3, 5 and 7 mm. ITI RC and ITI RC H11 scanning rods were connected to the replacement body and placed into the seating tract for scanning. The reference data were obtained using a 3D dental scanner, and the experimental data were obtained by 10 scans of each model using a digitized intraoral scanner. Geomagic Wrap 2021 was used to analyze the model data to test the trueness and precision of the models.

Results: The trueness did not differ significantly among the groups (P > 0.05). The implant depth of 1 mm achieved the highest impression precision (66.81±2.45 μm), and the depth of 0 mm resulted in a significantly lower precision (95.60±3.04 μm) than the depth of 1 and 3 mm. Starting from the subgingival depth of 1 mm, the precision of the scan decreased progressively with the increase of the implant depth. At the subgingival implant depth of 5 or 7 mm, the use of an extended rod significantly improved the scan precision.

Conclusion: For single-tooth implant restoration of the mandibular posterior teeth, the implant depth can substantially affect the accuracy of digital impression, which decreases as the implant depth increases. For a deep implant, the use of a longer scanning rod can improve the scanning accuracy.