Abstract
Stages of bone healing in mandibular fractures are evaluated mainly based on clinical symptoms and x-ray appearance. However, the above evaluations are thought to be subjective by nature. An experimental and a clinical studies on the stages of healing process of mandibular fractures were performed based on Coherence function analysis utilizing a vibration test, in order to develop an objective method to analyse the healing process in the mandibular fractures.
Intermaxillary fixations with steel wires were placed in 19 male monkeys (about 6kg body weight, with permanent dentition) soon after the mandibles were intentionally fractured. Observations on the stages of healing process were performed weekly with x-ray and checking the level of vibration for 12 weeks after the intermaxillary fixation. The monkeys were sacrificed weekly and sections were prepared for a histological examination. The level of vibration frequency on the fracture site was consistently lower than that of the non-fracture site soon after the intermaxillary fixation. The vibration frequency of the fracture site, however, increased to almost the same level as that of the non-fracture site in the fourth week. Bone unions at the fracture site were histologically evident on the fourth week after the intermaxillary fixation and increased gradually. Clinical observations on the healing process of mandiblar fractures, based on Coherence function analysis employing the vibration test, were also performed on 60 patients who were treated in the Department of Oral Surgery, Dental Clinics of Hokkaido University. The vibration frequencies of the fracture sites in the mandibles were almost the same levels as those of the non-fracture sites four to five weeks after the intermaxillary fixation. The intermaxillary fixations were removed based on the results of Coherence function analysis, and no clinical problems were encountered. Follow up observations also revealed mandibular functions to be satisfactory.
The above mentioned data suggests that Coherence function analysis employing the vibration test is a valuable method in evaluating the stages of healing process in mandibular fractures.
