The upper and lower jaws of some persons do not directly register with each other, and hence mal-occlusion of those jaws can exist. In some instances the mal-occlusion of the jaws is of such a nature and of such an extent that the application of a yieldable force to those jaws over a prolonged period of time can eliminate the mal-occlusion. Some orthodontists have urged persons, who have correctable mal-occlusions, to attach rubber bands to hook-equipped metal orthodontic bands that are affixed to their teeth; because those rubber bands could supply repositioning forces which could reduce or eliminate the mal-occlusions. Unfortunately, rubber bands must be replaced several times a week or even daily; and many persons do not replace them. Other orthodontists have connected the ends of springs to the jaws of persons in an effort to reduce or eliminate mal-occlusions of those jaws; but the repositioning forces applied by those springs frequently were too large, and portions of those springs were occasionally bitten by the teeth of those persons.