Magnitude of beam-hardening artifacts produced by gutta-percha and metal posts on cone-beam computed tomography with varying tube current

Abstract

Purpose: This study was performed to evaluate the magnitude of artifacts produced by gutta-percha and metal posts on cone-beam computed tomography (CBCT) scans obtained with different tube currents and with or without metal artifact reduction (MAR).

Materials and methods: A tooth was inserted in a dry human mandible socket, and CBCT scans were acquired after root canal instrumentation, root canal filling, and metal post placement with various tube currents with and without MAR activation. The artifact magnitude was assessed by the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) at the various distances from the tooth. Data were compared using multi-way analysis of variance.

Results: At all distances, a current of 4 mA was associated with a higher SD and a lower CNR than 8 mA or 10 mA (P<0.05). For the metal posts without MAR, the artifact magnitude as assessed by SD was greatest at 1.5 cm or less (P<0.05). When MAR was applied, SD values for distances 1.5 cm or closer to the tooth were reduced (P<0.05). MAR usage did not influence the magnitude of artifacts in the control and gutta-percha groups (P>0.05).

Conclusion: Increasing the tube current from 4 mA to 8 mA may reduce the magnitude of artifacts from metal posts. The magnitude of artifacts arising from metal posts was significantly higher at distances of 1.5 cm or less than at greater distances. MAR usage improved image quality near the metal post, but had no significant influence farther than 1.5 cm from the tooth.

Keywords: Artifacts; Cone-Beam Computed Tomography; Gutta-Percha; Metals.

Fig. 1. A. A line was drawn perpendicular to the mandibular body and through the center of the artifact-generating object. B. 20°-step lines were drawn above and below the perpendicular line, and 5 concentric semicircles were created with different radii (0.5-cm intervals). C. In the regions of intersection between the lines and the semicircles, 24 square regions of interest (ROIs) of the same size were established. A square ROI of the same size as the others was established in the silicone block, serving as the control area.

Fig. 2. Axial images represent intracanal materials (control in the first row, gutta-percha in the second row, and metal post in the third row) with different tube currents (4 mA, 8 mA, and 10 mA) and without and with the application of a metal artifact reduction tool.