RESUMO
OBJECTIVE: This study was developed to evaluate the influence of voxel size on bone measurements for implant planning. MATERIALS AND METHODS: The research was performed by using edentulous synthetic human mandibles with different levels of bone resorption. For each mandible, height and bone thickness were measured with a digital caliper. The PaX-i3d device was used to acquire the volumes of the five mandibles, with 50kVp, 4 mA, and a voxel size of 0.08 mm. After the acquisition, the images were reconstructed in the software CS three-dimensional Imaging, with four different sizes of voxels: 0.1, 0.2, 0.3, and 0.4 mm. All volumes were analyzed by a single evaluator who performed measurements to obtain bone height and thickness, using the reference points that were considered in obtaining the gold standard. The data were analyzed by ANOVA with a significance level of 5%. RESULTS: There was no significant difference in the measurements obtained with different voxel sizes, both for bone height measurements and bone thickness. There was no statistically significant difference in measurements in thickness in comparison to the gold standard. CONCLUSION: When necessary, to measure height and bone thickness, it is possible to recommend voxel images of larger size (0.40 mm) without compromising the quality of the patient's clinical planning.
RESUMO
PURPOSE: To evaluate the influence of low-dose protocols, with different numbers of basis images, on the precision of linear bone measurements in CBCT images. MATERIALS AND METHODS: Five polyurethane mandibles, with different levels of bone resorption, were used in this in vitro study. To obtain the reference standard, landmarks were made in the mandibular superior and buccal cortices, and then a digital caliper was used to measure the bone height and thickness at these regions. CBCT images were obtained with the PaX-i3D (Vatech) unit set at 50 kV, 4 mA, 0.2-mm voxel size and 50 × 50-mm field of view. Keeping these parameters fixed, each mandible was scanned twice, with different protocols: Low dose (L) had an acquisition time of 24 seconds and 720 basis images, and ultralow dose (UL) had an acquisition time of 15 seconds and 450 basis images. Then, measurements of bone height and thickness were performed on the images, using the previously determined landmarks as reference. The obtained data were submitted to statistical analysis, with a significance level of .05. Analysis of variance, Student t test, and intraclass correlation coefficient were employed. RESULTS: Regarding bone height, there were no significant differences between the measurements obtained with the L and UL protocols (P = .8648). Additionally, the L and UL protocols did not differ in relation to the reference standard (P = .8717 and P = .9928, respectively). Likewise, there were no significant differences between the measurements obtained with the L and UL protocols (P = .7969) for bone thickness, nor between these protocols and the gold standard (P = .7455). CONCLUSION: Considering the great demand for precise measurements in implantology, protocols of low-dose radiation can be used without compromising clinical planning.