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.

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.