Influência do tamanho do FOV e voxel na avaliação da espessura dentinária radicular em molares inferiores: estudo em tomografia computadorizada de feixe cônico

Abstract

The danger zone concept (DZ) was established in 1980 by Abou-Rass et al., when he suggested the anti-curvature instrumentation technique for the preparation of curved root canals. The DZ is a specific region of the root more susceptible to perforation and strips in case of excessive removal of dentin during mechanical preparation. The aim of this experimental study was to verify whether the assessment of the danger zone (ZD) of mandibular molars is affected by the size of the FOV and voxel in cone-beam computed tomography (CBCT) scans, compared to standard micro-CT images. of reference. Thus, forty mandibular first and second molars were selected. Teeth were scanned on a computed microtomography (micro-CT) device to establish reference standard images. Then they underwent CBCT scans varying the field of view (FOV) (10 x 5.5 cm; 5 x 5.5 cm) and voxel size (0.4, 0.2, 0.15, 0.075 mm). The images were evaluated by two endodontists regarding the dentin thickness of the lower molars, in axial sections at 2, 4 and 6 mm from the root furcation. The smallest dentin thickness of the mesiobuccal and mesiolingual canals was measured on the distal outer surface of the mesial root. All assessments were performed under standardized conditions. The collected data were analyzed using descriptive and inferential statistics (intraclass correlation coefficient (ICC) and paired t test) (p<0.05). As a result of this study, we found that all measurements overestimated root dentin thickness compared to the reference standard (p<0.001). When using a voxel size of 0.4 mm with a FOV of 5 x 5.5 cm, the dentin thickness value was more overestimated (p = 0.007) when comparing the FOVs. In contrast, the dentin thickness with voxel size of 0.075 mm and FOV of 5 x 5.5 cm was significantly smaller and presented the best ICC value with the reference standard (0.936). Given the above, we concluded that CBCT overestimates the dentin thickness of the DZ of lower molars, regardless of FOV and voxel sizes. The 5 x 5.5 cm FOV performed best with the voxel size of 0.075 mm, while it performed poorly with the voxel size of 0.4 mm.