The Use Of Metallic Implants In The Study Of Facial Growth In Children

The Use of Metallic Implants in the Study o Facial f
Growth in Children : Method and Application
ARNE BJORK Orthodontic Department, Royal Dental College, Copenhagen, Denmark

ABSTRACT On the basis of experience gained over a number of years, a n account is given of the technique for insertion of the implants, the radiographic method, and the graphic procedure for preparation of growthtracings. Small pins of hard tantalum are hammered into the bone under local analgesia with a pencil-shaped instrument, in the tip of which the implant is placed. No surgical exposure is necessary. Because of remodeling resorption of the bone and eruption of the teeth, the implants can be placed only in certain places in the maxilla and mandible. In implant studies it is necessary to observe a high levelof reproducibility in positioning the head in the cephalostat. An x-ray cephalostat with a built-in image intensifier has been designed which enables the position to be monitored by televison. In the graphic procedure, drawings of the arches from dental casts are incorporated in tracings of profile radiographs; the paths of eruption of the teeth and deveIopment of the arches can then be examinedwith the metallic implants as references.

In 1951 a section was set up at the Department of Orthodontics, Royal Dental College, Copenhagen, to provide facilities for radiographic study by the metallic implant technique of the growth of the face and development of dentition in normal children, and in some cases of various pathologic forms of development. On the basis of experience over a numberof years an account is given here of the technique for insertion of the implants, the radiographic method, and the graphical procedure for making growth tracjngs.

I m p l a n t Method Small pins of hard tantalum are hammered into the bone under local analgesia with a special pencil-shaped instrument in the tip of which the implant is placed (fig. 1) (Bjork, '55, '63). No surgical exposure isnecessary. To insure that the pin will be guided straight into the bone, it must fit the instrument accurately. The instrument is made of stainless steel, and the tip, to avoid its deformation by hard bone, is designed to be replaceable (fig. 2). It is pressed through the periosteum to secure a firm basis before the pin is hammered in. By having the moving component (the piston) projecting beyondthe tip, the pin is inserted deeper into the bone (fig. 3 ) . The pins must be hard enough to resist bending, and they are now made excluh r . J PRYS. ANIHROP.,29: 243-254. .

sively of hard tantalum wire.' They are more radiopaque than those of chromecobalt alloy, and retain their position in the bone apart from displacement by the remodeling process at the bone surface or by erupting teeth. Thepins measure 1.5 mm in length and 0.5mm in diameter. As a smaller pin has also proved desirable, a new instrument has been designed which takes pins measuring 1.2 X 0.37mm.2 Because of remodeling resorption of the bone and eruption of the teeth, the implants should be placed only at selected sites in the maxilla and mandible. The mandible. Before the pins are inserted, the form of the mandible andposition of the dental germs are studied on profile radiographs. Usually, five or six pins are inserted in four regions (fig. 4) (Bjork, ' 6 3 ) . 1. One pin is placed on the anterior aspect of the symphysis, as f a r down as possible in the midline beneath the germs or root tips. This pin has proved to be highly stable, but it may be exposed by resorption if it is placed too high in thesupramental region. When inserting it, a finger is placed below the tip of the
1 Hard tantalum wire is produced by Fansteel Metallurgical Corporation, North Chicago, Ill. 2 The instrument and the pins are manufactured and supplied by 0.Dich Ltd., Holmevej 18, Hvidovre, Denmark. The pins should be boiled in 10% nitric acid before sterilization.

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ARNE BJORK

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