Influence of common orthodontic appliances on the diagnostic quality of cranial magnetic resonance images

Introduction: The aim of this study was to evaluate cranial magnetic resonance (MR) image distortion caused by various orthodontic brackets. Methods: Ten subjects received 5 consecutive cranial MR scans. A control scan was conducted with Essix trays (GAC International, Bohemia, NY) fitted over the maxillary and mandibular teeth. Four experimental MR scans of the head were conducted with plastic, ceramic, titanium, and stainless steel brackets incorporated into the Essix tray material. Each MR scan consisted of 4 sequences: sagittal T1-weighted spin echo (T1 sagittal), axial T2-weighted spin echo (T2 axial), gradient echo, and diffusion-weighted imaging. Three board-certified neuroradiologists examined the MR images for distortion in predetermined regions of the head. Results: The paired Wilcoxon signed rank test showed a statistically significant difference between the mean distortion scores of stainless steel brackets and the mean distortion scores of the other experimental MR scans (P <0.0001). Interrater and intrarater agreement was high (kappa statistic and associated 95% confidence intervals). Conclusions: The study showed that plastic, ceramic, and titanium brackets cause minimal distortion of cranial MR images (similar to the control). On the other hand, stainless steel brackets cause significant distortion, rendering several cranial regions nondiagnostic. Areas with the most distortion were the body of the mandible, the hard palate, the base of the tongue, the globes, the nasopharynx, and the frontal lobes. In general, the closer the stainless steel appliance was to a specific anatomic region, the greater the distortion of the MR image.