Identification of various orthodontic materials as foreign bodies via panoramic radiography, cone beam computed tomography, magnetic resonance imaging, and ultrasonography: an in vitro study

Objectives We evaluated the in vitro detection sensitivity of orthodontic materials (serving as foreign bodies) using panoramic radiography, cone beam computed tomography (CBCT), magnetic resonance imaging (MRI), and ultrasonography. Methods Five different orthodontic materials served as foreign bodies: titanium-molybdenum alloy wire (TMA; ORMCO, Orange, CA, USA; 0.017 x 0.025 in in cross-sectional dimensions and 1 cm long); stainless steel bracket tooth #34 (American Orthodontics, Sheboygan, WI, USA); a monocrystalline, sapphire ceramic bracket tooth #34 (Skyortho Dental Supplies Medical, China); a polycrystalline alumina clear bracket, Damon clear bracket tooth #34 (ORMCO); and a 1 x 1 x 0.1 cm polyurethane-based thermoplastic material, Invisalign clear aligner (Align Technology, San Jose, CA, USA). Panoramic radiography, CBCT, MRI, and ultrasonography were used, and four observers scored all findings independently. Results The TMA and stainless steel bracket were visualised in all fields by panoramic radiography and CBCT. The sapphire and Damon brackets were very clear on CBCT. The Invisalign in air was evident only on CBCT. MRI was unable to identify any material in muscle. Ultrasonography detected the TMA, sapphire bracket, and the Invisalign in muscle but only the TMA on bone. Conclusions Panoramic radiography does not reveal nonmetallic orthodontic equipment in air and reveals them only poorly in muscle. CBCT was the optimal imaging modality for all materials in all fields except for the Invisalign in muscle and bone. CBCT was the only method that revealed the Invisalign in air. MRI and ultrasonography should be used to detect orthodontic materials in muscle.