Functional orthopedic magnetic appliance (FOMA) II-Modus operandi

Alexander D. Vardimon*, Jeanne J. Stutzmann, Thomas M. Graber, Lawrence R. Voss, Alexandre G. Petrovic

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A new functional appliance (FA) to correct Class II dentoskeletal malocclusions is introduced. The functional orthopedic magnetic appliance (FOMA) II uses upper and lower attracting magnetic means (Nd2Fe14B) to constrain the lower jaw in an advanced sagittal posture. In vitro, a special gauge transducer measured the magnetic attractive path and forces. In vivo, 13 prepubertal female Macaca fascicularis monkeys received facial implants and were treated for 4 months with the following appliances: conventional FA (four subjects), FOMA 11 (five subjects), a combined FOMA II + FA (two subjects), and sham (control) appliance (two subjects). The in vitro results showed the following: vertico-sagittally displaced upper and lower magnets attracted ultimately along an oblique line with a terminal horizonal slide to become fully superimposed; the functional performance improved when the magnetic interface acted as a magnetic inclined plane; and the magnetic force was able to guide and constrain the mandible toward the constructive protrusive closure position (CPCP) (1.2 mm, F = 570 gm) from levels below the habitual rest positon (3 mm, F = 219 gm) and the electromyographic (EMG) relaxed position (8.5 mm, F = 45 gm). The in vivo results demonstrated the following: functional performance increased in FOMA II (22%) and in the combined FOMA II + FA (28%) over the conventional FA; mandibular length increased significantly in the treated animals (X = 2.83 ± 0.70 mm) over the_ control animals (X = 0.43 ± 0.08 mm); incisor proclination was lower in magnetic appliances (X = 4.57 ± 1.76°) than in the conventional FA (X = 8.75 ± 1.85°); mandibular elongation and condylar posterior inclination resulted from posterosuperior endochondral growth (increased cell proliferation and/or hyperplasia of functional chondroblasts) and by bony remodeling of the condylar neck (apposition posterior border, resorption anterior border), respectively; virtually no anterior displacement of the postglenoid spine (X = 0.19 ± 0.68 mm) nor the articular eminence (X = 0.36 ± 0.69 mm) was found. Increased lower posterior alveolar height (X = 1.71 ± 0.82 mm) is a major impediment in the correction of excessive lower anterior facial height. The results of the study highly recommend the exploration of the clinical application of the FOMA II.

Original languageEnglish
Pages (from-to)371-387
Number of pages17
JournalAmerican Journal of Orthodontics and Dentofacial Orthopedics
Issue number5
StatePublished - May 1989
Externally publishedYes


FundersFunder number
American Association of Orti-odontists
National Institute of Dental Research
National Institutes of Health
National Institute of Dental and Craniofacial ResearchR01DE007787
U.S. Public Health Service5 ROl DE 07787-02
American Academy of Ophthalmology


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