Subscribe to RSS
DOI: 10.1055/s-2005-858762
© Georg Thieme Verlag KG Stuttgart · New York
Kieferorthopädische Brackets in der Hochfeld-Magnetresonanz-Tomographie: Experimentelle Beurteilung magnetischer Anziehungs- und Rotationskräfte bei 3 Tesla
Orthodontic Brackets in High Field MR Imaging: Experimental Evaluation of Magnetic Field Interactions at 3.0 Tesla * Beide Autoren teilen sich die Erstautorenschaft.Publication History
Publication Date:
07 December 2005 (online)
Zusammenfassung
Ziel: Die Beurteilung der magnetischen Anziehungs- und Rotationskräfte verschiedener kieferorthopädischer Brackets an einem 3,0-Tesla-MRT-System. Material und Methoden: Es wurden 32 kieferorthopädische Brackets aus Stahllegierungen (n = 27), aus Kobalt-Chrom (n = 2), aus Keramik (n = 1), aus Keramik mit Stahleinsatz (n = 1) und aus Titan (n = 1) auf Interaktionen im statischen Magnetfeld an einem 3,0-Tesla-MRT-System untersucht. Die Bestimmung der auf die Implantate im statischen Magnetfeld wirkenden Translationskräfte Fz [mN] erfolgte mithilfe des Fadentests nach Richtlinien der American Society for Testing and Materials (ASTM) über die Bestimmung des Deflektionswinkels β [°]. Die Bestimmung der Rotationskräfte Frot erfolgte qualitativ anhand einer 5-Punkte-Graduierung (0 = keine Rotationskraft; + 4 = sehr starke Rotationskraft). Ergebnisse: Bei 18 der 32 getesteten Brackets war der Deflektionswinkel β > 45° und die Translationskraft Fz lag oberhalb der auf das jeweilige Bracket wirkenden Gravitationskraft FG (Fz: 1,2 - 45,7 mN). Die Translationskraft Fz betrug hierbei im Maximum das 68,5fache der auf das Objekt einwirkenden Gravitation (Verhältnis Fz/FG: 1,4 - 68,5). Hierzu konkordant war eine ausgeprägte Rotationskraft Frot bei diesen Objekten (Grad + 3/+ 4). Bei den übrigen 14 Objekten betrug der Deflektionswinkel β < 45° und die Rotationskräfte Frot schwankten zwischen 0 und + 2. Sowohl auf das Keramik- als auch das Titanbracket wirkten keine messbaren Translations- und Rotationskräfte. Schlussfolgerung: Die Mehrzahl der getesteten Brackets (18/32 = 56,25 %) muss nach den Richtkriterien der ASTM zur Translationskraft Fz als „nicht MRT-sicher” bei der Verwendung in einem 3T-MRT-System klassifiziert werden. Die gemessenen Translationskräfte sind jedoch deutlich geringer als typische Haftkräfte am Zahn fixierter Brackets. Die Auswirkungen dieser Ergebnisse auf MRT-Untersuchungen kieferorthopädischer Patienten bei 3 Tesla werden diskutiert.
Abstract
Purpose: To evaluate static magnetic field interactions for 32 commonly used orthodontic brackets in a 3.0 T magnetic resonance imaging (MRI) system. Materials and Methods: 32 orthodontic brackets consisting of a steel alloy (n = 27), a cobalt-chromium alloy (n = 2), ceramic (n = 1), ceramic with a steel slot (n = 1), and titanium (n = 1) from 13 different manufacturers were tested for magnetic field interactions in a static magnetic field at 3.0 T (Gyroscan Intera 3.0 T, Philips Medical Systems, Best, Netherlands). The magnetic deflection force Fz [mN] was evaluated by determining the deflection angle β [°] using the established deflection angle test according to the ASTM guidelines. The magnetic-field-induced rotational force Frot or torque was qualitatively determined using a 5-point grading scale (0: no torque; + 4: very strong torque). Results: In 18 of the 32 brackets, the deflection angle β was found to be > 45° and the translational force exceeded the gravitational force FG on the particular bracket (Fz: 1.2 - 45.7 mN). The translational force Fz was found to be up to 68.5 times greater than the gravitational force FG (Fz/FG: 1.4 - 68.5). The rotational force Frot was correspondingly high (+ 3/+ 4) for those brackets. For the remaining 14 objects, the deflection angles were < 45° and the torque measurements ranged from 0 to + 2. The static magnetic field did not affect the titanium bracket and the ceramic bracket. No measurable translational and rotational forces were found. Conclusion: Of the 32 brackets investigated for magnetic field interactions at 3.0 T, 18 (56.25 %) were unsafe in the MR environment according to the ASTM guidelines. However, the forces measured were minimal compared to the forces generally necessary for dislodging these bonded orthodontic brackets from tooth surfaces. The implications of these results for orthodontic patients undergoing MR examinations at 3 Tesla are discussed.
Key words
Orthodontic bracket - MR safety - implants - bioeffects - magnetic resonance imaging - magnetic resonance - high field
Literatur
-
1
http:// www.MRIsafety.com (1.9.2005).
- 2 Okano Y, Yamashiro M, Kaneda T. et al . Magnetic resonance imaging diagnosis of the temporomandibular joint in patients with orthodontic appliances. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003; 177 255-263
-
3 ASTM .Designation: F2052 - 02. Standard test method for measurement of magnetically induced displacement force on medical devices in the magnetic resonance environment. Annual book of ASTM standards 2002;. 1576-1580
- 4 New P F, Rosen B R, Brady T J. et al . Potential hazards and artifacts of ferromagnetic and nonferromagnetic surgical and dental materials and devices in nuclear magnetic resonance imaging. Radiology. 1983; 177 139-148
- 5 Greatbatch W, Miller V, Shellock F G. Magnetic resonance safety testing of a newly-developed fiber-optic cardiac pacing lead. J Magn Reson Imaging. 2002; 177 97-103
- 6 Edwards M B, Taylor K M, Shellock F G. Prosthetic heart valves: evaluation of magnetic field interactions, heating, and artifacts at 1.5 T. J Magn Reson Imaging. 2000; 177 363-369
- 7 Shellock F G, Shellock V J. Metallic stents: evaluation of MR imaging safety. AJR Am J Roentgenol. 1999; 177 543-547
- 8 Kagetsu N J, Litt A W. Important considerations in measurement of attractive force on metallic implants in MR imagers. Radiology. 1991; 177 505-508
- 9 Nogueira M, Shellock F G. Otologic bioimplants: ex vivo assessment of ferromagnetism and artifacts at 1.5 T. AJR Am J Roentgenol. 1994; 177 1472-1473
- 10 Shellock F G. Metallic marking clips used after stereotactic breast biopsy: ex vivo testing of ferromagnetism, heating, and artifacts associated with MR imaging. AJR Am J Roentgenol. 1999; 177 1417-1419
- 11 Shellock F G. Biomedical implants and devices: assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imaging. 2002; 177 721-732
- 12 Sommer T, Maintz D, Schmiedel A. et al . Hochfeld-Magnetresonanztomographie: Magnetische Anziehungs- und Rotationskräfte auf metallische Implantate bei 3,0 T. Fortschr Röntgenstr. 2004; 177 731-738
- 13 Kangarlu A, Shellock F G. Aneurysm clips: evaluation of magnetic field interactions with an 8.0 T MR system. J Magn Reson Imaging. 2000; 177 107-111
- 14 Kangarlu A, Baudendistel K T, Heverhagen J T. et al . Klinische Hoch- und Ultrahochfeld-MR und ihre Wechselwirkung mit biologischen Systemen. Radiologe. 2004; 177 19-30
-
15
http:// www.fda.gov/cdrh/ (1.9.2005).
- 16 Geiger A M, Gorelick J, Gwinnett A J. Bond failure rates of facial and lingual attachments. J Clin Orthod. 1983; 177 165-169
- 17 Millett D T, Hallgren A, Cattanach D. et al . A 5-year clinical review of bond failure with a light-cured resin adhesive. Angle Orthod. 1998; 177 351-356
- 18 Newman G V. A posttreatment survey of direct bonding of metal brackets. Am J Orthod. 1978; 177 197-206
- 19 Sunna S, Rock W P. Clinical performance of orthodontic brackets and adhesive systems: a randomized clinical trial. Br J Orthod. 1998; 177 283-287
- 20 Zachrisson B J. A posttreatment evaluation of direct bonding in orthodontics. Am J Orthod. 1977; 177 173-189
- 21 Adolfsson U, Larsson E, Ogaard B. Bond failure of a no-mix adhesive during orthodontic treatment. Am J Orthod Dentofacial Orthop. 2002; 177 277-281
- 22 Shellock F G, Tkach J A, Ruggieri P M. et al . Cardiac pacemakers, ICDs, and loop recorder: evaluation of translational attraction using conventional („long-bore”) and „short-bore” 1.5- and 3.0-Tesla MR systems. J Cardiovasc Magn Reson. 2003; 177 387-397
- 23 Shellock F G. Magnetic resonance safety update 2002: implants and devices. J Magn Reson Imaging. 2002; 177 485-496
- 24 Baker K B, Nyenhuis J A, Hrdlicka G. et al . Neurostimulation systems: assessment of magnetic field interactions associated with 1.5- and 3-Tesla MR systems. J Magn Reson Imaging. 2005; 177 72-77
- 25 Reynolds I R, von Fraunhofer J A. Direct bonding of orthodontic brackets - a comparative study of adhesives. Br J Orthod. 1976; 177 143-146
-
26 ASTM .Designation: F2213 - 04. Standard test method for measurement of magnetically induced torque on medical devices in the magnetic resonance environment. Annual book of ASTM standards 2002;. 1576-1580
- 27 Shellock F G, Detrick M S, Brant-Zawadski M N. MR compatibility of Guglielmi detachable coils. Radiology. 1997; 177 568-570
- 28 Shellock F G, Shellock V J. Cranial bone flap fixation clamps: compatibility at MR imaging. Radiology. 1998; 177 822-825
- 29 Sadowsky P L, Bernreuter W, Lakshminarayanan A V. et al . Orthodontic appliances and magnetic resonance imaging of the brain and temporomandibular joint. Angle Orthod. 1988; 177 9-20
Dr. Jörn Kemper
Martinistr. 52
20246 Hamburg
Phone: ++ 49/40/4 28 03 40 29
Fax: ++ 49/40/4 28 03 38 02
Email: jkemper@uke.uni-hamburg.de