Effects of dental alloy restorers on MRI for head and neck examination

objectives:: To investigate the effects of artificial crown with alloys on MR images. MATERIALS and METHODS: Four metal crowns were made of Nickel-Chromium, Gold-Palladium, Titanium,Nickel-Chromium- titanium alloy and three dental metal bonding porcelain crowns were made with Nickel-Chromium, Nickel-Titanium, Gold-Platinum alloy, respectively. The crown was put on a narcotized monkey's right upper lateral incisor, separately. Then the monkey's head-and-neck was examined with a 2.0 T MR scanner. Four clinical routine scan sequences including spin echo (T1); fast spin echo (T2); proton density (PD); gradient echo (GRE) and one functional scan protocol (gradient echo planar image, GE EPI) were used to observe the effects of the dental metal alloys. RESULT: 1.All of the crowns were not dislocated during all the 5 scans. 2. Metal artifact around the crown was found on all images with different size and shape. On the T1, T2, PD, GRE images, the artifacts were circular. On the GE EPI images which was patch-shaped. 3. Maximal artifact was found from Nickel-Chromium alloy crown and Minimal artifact was found from Gold-Palladium alloy crown. CONCLUSION: It is safe to receive a head-and-neck MRI examination for the patients with dental metal alloy restorer and most dental meter alloy restorer result in distortion on all MR images. The distortion was different according to the scan sequence, which was less on the anatomical MR images than the functional MR images.