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3-D Force and Moment Analysis of Repulsive Magnetic Appliances to Correct Dentofacial Vertical Excess

The Maurice and Gabriela Goldschleger School of Dental Medicine, Department of Orthodontics, Tel Aviv University, Tel Aviv 69978, Israel

C. Bourauel

Poliklinik fur Kieferorthopadie, Rhein, Friedrich-Wilhelms-Universität, Welschnonnenstr. 17, 5300 Bonn 1, Germany

D. Drescher

Poliklinik fur Kieferorthopadie, Rhein, Friedrich-Wilhelms-Universität, Welschnonnenstr. 17, 5300 Bonn 1, Germany

G.P.F. Schmuth

Poliklinik fur Kieferorthopadie, Rhein, Friedrich-Wilhelms-Universität, Welschnonnenstr. 17, 5300 Bonn 1, Germany

Repulsive magnetic appliances can intrude posterior teeth, but create a lateral shift of the mandible and also decrease in force as the mouth opens. To model their optimal use, the 3-D spatial force/displacement (F/D) and moment/ displacement (M/D) diagrams of four magnetic repulsive appliances in diverse overlapping arrangements were characterized and compared. In this orthodontic measurement and simulation system, only the medial eccentric magnetic arrangement, of the four compared, partially met the criteria of an optimal repulsive force system, i.e., keeping a constant intruding force and excluding shearing force. The moment analysis found that eccentric arrangements, however, developed high Z-moment. Thus, a perplexing point was reached where the force analysis favored medial centric arrangement and the moment analysis favored centric arrangement. When the gap between juxtaposed magnets increased over 2 mm, the repulsive force declined and the attractive force was favorably eliminated. At gap distances of 3 to 6 mm, the intrusive force was almost constant. These data suggest that centric arrangement is indicated clinically when the gap is minute and Müller prongs are used to prevent deleterious lateral shearing forces.

Key Words: Orthodontic Appliances • Dental Models • Force and Moment Analyses

Journal of Dental Research, Vol. 73, No. 1, 67-74 (1994)
DOI: 10.1177/00220345940730010901


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