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Objective: To assess the influence of windowing and metal artefact reduction (MAR) algorithms on the volumetric dimensions of high-density materials using two CBCT systems. Methods: Four cylinders of amalgam, cobalt-chromium, gutta-percha, titanium and zirconium, were manufactured and their physical volumes (PV) were measured. A polymethyl methacrylate phantom containing the cylinders was submitted to CBCT acquisitions with Picasso Trio and OP300 units with their MAR enabled and disabled. The tomographic volume (TV) of all the cylinders was obtained by semi-automatic segmentation using two windowing adjustments: W1—large window width and upper window level; W2—narrow window width and low window level. Volumetric distortion was expressed as the difference between TV and PV. Statistics comprised intraclass correlation coefficient (ICC) and analysis of variance (ANOVA) for repeated measures with Tukey post hoc test (α = 5%). Results: The ICC values ​​indicated excellent reproducibility of TV. Gutta-percha and titanium resulted in the smallest volumetric distortion. Using W1 provided less volumetric distortion for almost all experimental conditions (p < 0.05). Activating MAR algorithm of Picasso Trio underestimated gutta-percha and titanium TV (p < 0.05) and was inefficient in significantly reducing the volumetric distortion of the other materials (p > 0.05). Disabling MAR algorithm of OP300 resulted in smaller volumetric distortion for almost all experimental conditions (p < 0.05). Conclusions: The TV of gutta-percha and titanium were closer to the PV. In general, the MAR algorithms of both systems were inefficient in significantly reducing the volumetric distortion of high-density materials. We encourage the use of large window width and upper window level to evaluate high-density materials.

Objectives: To assess whether dimensional changes occur as shape distortion (unevenly), contraction or magnification (evenly) in cone beam computed tomography (CBCT) considering materials, anatomical regions, and metal artefact reduction algorithms (MAR). Methods: Four cylinders of amalgam (Am), cobalt-chromium (Co-Cr), gutta-percha (Gu), titanium (Ti) and zirconium (Zi) were inserted inside a polymethylmethacrylate phantom in anterior and posterior regions for acquisitions in Picasso Trio and OP300 with MAR enabled and disabled. Two observers measured the dimensions of each cylinder in three axes: Y (height), Z (antero posterior diameter), and X (latero-lateral diameter). Repeated measures ANOVA with Tukey post-hoc test compared the data (α = 5%). Results: Shape distortion occurred for all materials in anterior region of Picasso Trio without MAR (p < 0.05). With MAR enabled, Gu and Ti contracted, while the others showed distortion (p ≥ 0.05). In posterior region, all materials distorted in both MAR conditions (p < 0.05), except Gu, which magnified without MAR (p ≥ 0.05) and contracted unevenly with MAR (p < 0.05). In anterior region of OP300, all materials magnified without MAR, (p ≥ 0.05), and had shape distortion with MAR (p < 0.05). In posterior region, only Am showed magnification without MAR (p ≥ 0.05), while all materials presented shape distortion with MAR (p < 0.05). Conclusion: Dimensional changes of high-density materials in CBCT can be either a magnification, a contraction or a distortion; the last condition is the most prevalent. Furthermore, changes differ considering material, anatomical region and MAR condition.

AimTo assess the influence of artefacts generated by metal posts on the detection of simulated internal root resorption (IRR) in adjacent teeth using cone‐beam computed tomography (CBCT) and to verify the impact of metal artefact reduction (MAR) on these cases.MethodologyCBCT images of 14 premolar teeth were acquired before and after IRR simulation using chemical and mechanical procedures, in an OP300 Maxio unit, with and without MAR. Each tooth was placed in the socket of a human mandible and scanned under three different conditions: (i) without adjacent teeth – control group; (ii) distal adjacent tooth restored with metal post; and (iii) with both adjacent teeth restored with metal post. Five oral radiologists scored the IRR detection using a 5‐point scale. Diagnostic values were obtained for the tested groups and compared using two‐way analysis of variance (α = 0.05).ResultsThe presence of a single adjacent tooth restored with metal post did not significantly influence the diagnostic values for IRR detection (P > 0.05). The presence of both adjacent teeth with metal posts, without MAR application, was associated with a significantly lower area under the ROC curve (Az) compared to the control (P = 0.0182). In this case, the application of MAR increased Az, leading to nonsignificant differences from the control group and the group with one adjacent restored tooth (P > 0.05). Sensitivity decreased significantly when two adjacent restored teeth were present, regardless of MAR application (P = 0.0379). Specificity was not affected by the conditions tested (P > 0.05).ConclusionCBCT detection of IRR was impaired by artefacts only when both adjacent teeth restored with metal posts were present. In such cases, activation of MAR improved the performance on this diagnostic task.

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