Rare earth magnets and impaction

Abstract

Aberration in the eruption process was found to be a prime etiologic factor in inducing impaction. Thus an ideal treatment approach should attempt to mimic the normal eruption modus. However, conventional traction methods have been found to be associated with gingiva inflammation, bone recession, reduced attached gingiva, periodontal pockets, exposed cementoenamel junction, and root resorption of the impacted and adjacent teeth. These side effects are the result of premature exposure of the impacted tooth to the oral cavity through a nonself-cleansing pathway and an uncontrolled force system. The present study introduces a new, magnetic attraction system, with a magnetic bracket bonded to an impacted tooth and an intraoral magnet linked to a Hawley type retainer. Vertical and horizontal magnetic brackets were designed, with the magnetic axis magnetized parallel and perpendicular to the base of the bracket, respectively. The vertical type is used for impacted incisors and canines, and the horizontal magnetic bracket is applied for impacted premolars and molars. A three-dimensional analysis of the magnetic force system, by means of the OMSS apparatus, found the small magnetic bracket combined with a large pole surface area of the intraoral magnet to exhibit the most efficient convergent guidance. For this report the magnetic eruption device was examined on one animal subject and four patients. The Nd2Fe14B magnets were coated with parylene and/or encapsulated in stainless steel housings. In deep impaction, the magnetic bracket was cold-sterilized before surgery, and the surgical mucoperiosteal flap was then sutured over the bonded magnetic bracket. Attraction was initiated 1 to 2 weeks after healing. Thus tooth emergence into the oral cavity replicated normal eruption conditioning. The system operated at an attractive force level of 0.2 to 0.5 N. Adjustment was accomplished by temporarily interposing a magnetic spacer between the two magnetic units. No side effects were observed in this restricted number of treated cases, and treatment time was reduced. The study recommends the application of magnets in the treatment of impaction on the grounds of less invasive surgical procedure, effective attractive forces at short distances, and controlled spatial guidance.