Study on volunteer to detect MRI artifacts caused by FPDs

OBJECTIVE: The purpose of this study was to evaluate MRI artifacts in a human (volunteer) oral cavity caused by several kinds of fixed partial dentures (FPDs) made of different alloys or different amounts of crowns. MATERIALS AND METHODS: Chosen was the volunteer who was a 23-year-old female graduate student of med school, with no lost-tooth or prosthesis in her mouth. She signed consent form voluntarily and agreed to participate in the study. 16 samples were divided into two groups --- non-precious alloy group and noble alloy group. There were eight samples in each group. Every sample was placed in the same volunteer oral cavity with a special device and subject to T2-weight Spin Echo sequence (T2-SE) scans by MR apparatus (1.5 Tesla, Signa Twinspeed, GE, America). The extent of MRI artifacts were measured and analyzed. SAS 8.2 was used for T test or analysis of variance (ANOVA). RESULTS: The maximum of artifacts caused by all samples ranged from 0.35cm to 7.25cm in MR images. There was statistically significant difference in the magnitude of artifacts between non-precious alloy crowns and noble alloy crowns (T test, P<0.01). Artifacts caused by non-precious alloy crowns would create more distortions in MR images of the oral and maxillofacial region, while artifacts caused by gold alloy crowns were less and more localized. There was statistically significant difference in the magnitude of artifacts among single crown, three-unit crowns and five-unit crowns (ANOVA, P<0.01). CONCLUSION: All samples could produce artifacts in MR images. Artifacts caused by non-precious alloy crowns are greater than those caused by noble alloy crowns and the size of artifacts was closely related to the amount of dentures.