Is detection accuracy of buccal bone level at implants in CBCT dependent on bone thickness

Background CBCT is very accurate in terms of distances and dimensions of bone defects. However, use of CBCT to assess bone in close proximity to dental implants (i.e. bone-to-implant contact) is questionable, because of compromised image quality due to beam hardening artifacts from the implant restoration. Several factors have been identified to influence the accuracy of CBCT in regards with the buccal bone at implant sites; e.g. implant-abutment material or the number of implants in the field of view. Aim/Hypothesis To investigate the impact of buccal bone thickness on the detection accuracy of buccal bone level (i.e., the extent depth of a buccal bone dehiscence) at implants in CBCT. Material and Methods Two implant beds (i.e., one for a narrow- and one for a standard diameter implant) have been prepared in each of 36 bone blocks of dry pig jaws. The implant beds were positioned at variable distances from the buccal bone surface, thus resulting in 3 groups of buccal bone thicknesses, i.e. >0.5–1.0; >1.0–1.5; >1.5–2.0 mm. In half of the blocks, a buccal bone dehiscence of random extent (“depth”) was additionally created. Implants were mounted either with a titanium abutment and a metal-ceramic crown or with a zirconia abutment and an all-ceramic zirconia crown. On longitudinal cross-sectional CBCT images, passing through the center of the implant, the distance from the implant shoulder to the buccal bone crest was measured by two masked and calibrated examiners. The distance measured on the CBCT images was then compared to the distance obtained by direct measurements with a digital caliper of the bone blocks. Results Abutment crown material and implant diameter had no effect on the detection accuracy of the buccal bone level at dental implants in CBCT scans. In contrast, buccal bone thickness was found to have a highly significant impact on detection accuracy of the buccal bone level. Specifically, when buccal bone was thin (i.e., >0.5–1.0 mm), presence absence of buccal bone dehiscence was judged wrongly in 48.5% of the cases. Among those cases with a buccal bone dehiscence, the average measurement error of the distance from the implant shoulder to the buccal bone crest was 1.6 mm. Conclusion and clinical implications The thickness of the buccal bone has a major impact on the correct diagnosis of the buccal bone level at dental implants made in CBCT images. Specifically, in cases of buccal bone ≤ 1 mm thick, detection of the buccal bone level is largely inaccurate.