Optimizing MRI Protocols with Metal Artifact Reduction Sequences in Dental Implants: An In Vitro Study on Dry Human Skull at 1.5 T

Abstract

Background: Dental implants can produce artifacts in magnetic resonance imaging (MRI), reducing image quality and diagnostic accuracy. The severity of artifacts can vary depending on implant characteristics and the MRI sequence used. Metal artifact reduction sequences (MARS) have been developed to mitigate artifacts, but their effectiveness across different implant types and sequences requires further investigation. Objectives: To quantify MRI artifacts from titanium (Ti), titanium-zirconium (Ti-Zr), and zirconia (Zr) implants across multiple sequences, with and without MARS, in the anterior and posterior maxilla using a dry human skull model. Materials and Methods: Implants were embedded in agar within a dry human skull at anterior (left lateral maxilla) and posterior (left second molar) positions. The MRI scans comprised ten sequences: T1-weighted (T1W), T2-weighted (T2W), proton density-weighted (PDW), and their 3-dimensional (3D) variants, each performed with and without MARS. Artifact volumes (signal loss and pile-up) were measured using Imalytics Preclinical software. Statistical analysis included ANOVA and Tukey’s HSD test (α = 0.05). Results: Artifact volumes varied significantly by implant material (P < 0.001), being largest for Ti, intermediate for Ti-Zr, and smallest for Zr. The MARS significantly reduced artifacts in metallic implants (Ti and Ti-Zr, P < 0.001). Importantly, MARS paradoxically increased artifacts in Zr implants. Without MARS, PDW sequences produced the fewest artifacts, while 3D T1W sequences generated the most (P = 0.03). Anterior implants showed greater signal loss than posterior implants (P < 0.001), with slightly higher pile-up, whereas total artifact differences were not significant (P = 0.263). Conclusion: Artifact severity strongly depends on implant material, with Ti producing the most and Zr the least artifacts. The PDW imaging minimizes artifact extent. While MARS effectively reduces artifacts in metallic implants, it paradoxically worsens artifacts in Zr, emphasizing the need for careful protocol selection for non-metallic implants.