Improving image quality of CBCT in the presence of metallic objects outside the field of view: effects of different materials and exposure parameters – an experimental study

Smallfield of view (FOV) cone-beam computed tomography (CBCT) scans are susceptible to artifacts caused by metallic objects located outside the FOV (exomass), which can degrade image quality. This study aimed to evaluate the effects of acquisition parameters on artifacts arising from common metallic materials in the exomass to determine optimal imaging conditions. This in vitro experimental study was conducted using a dry human mandible with ballistic gelatin for soft-tissue simulation. Three common dental materials, namely titanium implants, cobalt-chromium (Co-Cr) posts, and amalgam restorations, were evaluated unilaterally and bilaterally. A dipotassium phosphate solution was used as a standardized reference for quantitative gray value assessment. CBCT scans were acquired with a 5 × 5 FOV and four exposure protocols combining two tube voltage levels (60 and 90 kVp) and two tube current levels (2 and 10 mA). A total of 960 measurements were obtained. The mean gray value (MGV) and standard deviation (SD) of gray values were calculated to assess image brightness and artifacts, respectively. Data were analyzed using three-way ANOVA, factorial ANOVA, and Bonferroni post-hoc correction at a significance level of 0.05. Regarding MGV, exomass groups demonstrated no statistically significant difference compared with the control. Regarding SD, titanium produced the greatest artifacts (SD = 356.17 ± 255.17), whereas amalgam build-up did not demonstrate a statistically significant difference from the control ( P = 1.00). Increasing kVp and mA significantly reduced SD across all materials ( P < 0.001). Bilateral exomass produced significantly higher SD compared with the unilateral one ( P < 0.01). Metallic exomass materials did not significantly affect mean gray-level intensity but significantly increased artifact severity. Titanium implants produced the greatest artifacts, whereas amalgam build-up produced the least. Within the limitations of this study, increasing kVp and mA may help reduce artifact severity and improve image quality when metallic objects are present outside the FOV.