Efeitos da quantidade de núcleos metálicos, das ligas metálicas e dos cimentos na formação dos artefatos em tomografia computadorizada de feixe cônico

Abstract

This study aimed to evaluate, subjectively and objectively, the effect of the number of metallic posts, metallic alloys and cements on the presence of artifacts in Cone Beam Computed Tomography (CBCT). This is an experimental in vitro study, with a sample composed of 20 human lower premolars, divided into four groups according to the metallic alloy and cement used for dental restoration: Ni-Cr/zinc phosphate; Ni-Cr/resin cement; Pd-Ag/zinc phosphate; Pd-Ag/resin cement. For scanning, the sample was placed on a dry partially dentate skull, covered with #7 wax and immersed in water to simulate a clinical condition. The sample was scanned, before and after post insertion and cementation, using CS 9000 3D with four exposure parameters – 85 kV (6.3 and 10 mA)/90 kV (6.3 and 10 mA) and i-CAT (120 kV, 5 mA). Teeth were also scanned with four different oral conditions: 1) a single tooth; 2) Two teeth on opposite sides; 3) Two teeth on the same side; 4) three teeth, two on the same side and one on the opposite side of the arch (CS 9000 3D with 85 kV/6.3 mA and i-CAT with 120 kV/5 mA). The presence of artifact was subjectively assessed by two previously calibrated observers and the objective analysis was performed by a trained observer using ImageJ software (National Institutes of Health, Bethesda, MD, USA). The Mann-Whitney test was used to compare the presence artifact between the alloys and between the cements. The Wilcoxon test was used to compare the exposure parameters and the different devices. Friedman's test with Dunn's correction was used to compare oral conditions. All analyzes were performed using the Statistical Package for the Social Sciences software (SPSS for Windows, version 25.0, IBM Corp., Armonk, NY, USA) with a significance level of 5%. For the subjective analyses, AgPd presented more hypodense and hyperdense lines than NiCr (p<0.001), and more hypodense halos for i-CAT (p<0.05). 10 mA presented hypodense halos, hypodense and hyperdense lines greater than 6.3 mA (p<0.05). 85 kV presented more hypodense halos than 90 kV (p<0.05). CS 9000 3D presented more hypodense and hyperdense lines than i-CAT (p<0.001). For objective analyses, AgPd showed higher hyperdense and hypodense artifacts than NiCr (p<0.05). Posts cemented with zinc phosphate showed higher hyperdense artifacts when scanned with CS 9000 3D (p<0.05). The CS 9000 3D presented higher artifacts than the i-CAT (p<0.05). The percentage of hypodense artifacts was significantly higher in the presence of two teeth on opposite sides of the arch (p<0.001); however, there was no significant difference in artifact area between the presence of two restored teeth and the presence of three restored teeth regardless of their position in the arch. Conclusion: High atomic number alloys, higher tube current and lower tube voltages can increase the artifacts present in CBCT images. Artifact area is increased by the presence of an extra restored tooth in the arch; however, the presence of more than two restored teeth in the arch may have little influence on the increase in artifact intensity, regardless of its position in the arch.