Conventional Multi-Slice Computed Tomography (CT) and Cone-Beam CT (CBCT) for Computer-Assisted Implant Placement. Part I: Relationship of Radiographic Gray Density and Implant Stability

Abstract

Purpose: The relationship of conventional multi-slice computed tomography (CT)- and cone beam CT (CBCT)-based gray density values and the primary stability parameters of implants that were placed by stereolithographic surgical guides were analyzed in this study. Materials and Methods: Eighteen edentulous jaws were randomly scanned by a CT (CT group) or a CBCT scanner (CBCT group) and radiographic gray density was measured from the planned implants. A total of 108 implants were placed, and primary stability parameters were measured by insertion torque value (ITV) and resonance frequency analysis (RFA). Radiographic and subjective bone quality classification (BQC) was also classified. Results were analyzed by correlation tests and multiple regressions (p<.05). Results: CBCT-based gray density values (76597.32 voxel value) outside the implants were significantly higher than those of CT-based values (668.4 +/- 110 Hounsfield unit, p<.001). Significant relations were found among the gray density values outside the implants, ITV (adjusted r(2)=0.6142, p=.001 and adjusted r(2)=0.5166, p=.0021), and RFA (adjusted r(2)=0.5642, p=.0017 and adjusted r(2)=0.5423, p=.0031 for CT and CBCT groups, respectively). Data from radiographic and subjective BQC were also in agreement. Conclusions: Similar to the gray density values of CT, that of CBCT could also be predictive for the subjective BQC and primary implant stability. Results should be confirmed on different CBCT scanners.