CHANGES IN BLOOD-CIRCULATION IN TEETH AND SUPPORTING TISSUES INCIDENTTO EXPERIMENTAL TOOTH MOVEMENT

Fluorescent microspheres (FM) were used to semi-quantify the effect of orthodontic forces on blood flow in oral tissues in young rats. Forty -five animals had an orthodontic appliance inserted on the first maxil lary molar on one side exerting a mesial force of approximately 50 g. Ten animals served as unoperated controls. On days 1, 3, 7, 14, and 21 after the start of the experiment, FM were injected into the left ven tricle through an abdominal approach in the experimental and control a nimals. FM were counted in serial sections from the jaws in the period ontal ligament, pulp, and alveolar bone in a fluorescent microscope. T he number of FM per tissue volume and/or tissue weight was taken as a measure of blood flow. The experimental side had significantly lower n umbers of FM/mm(3) in the periodontal ligament of the first and the se cond molar on the first day, compared with the contralateral side. How ever, a steady, significant increase in the number of FM/mm(3) in the periodontal and pulpal tissues, and FM/mg in the alveolar bone could b e observed on the third and seventh days on the experimental side of t he first, second, and third molars compared with the contralateral sid e, while in the later stages the values of the two sides approached ea ch other. The results of this study indicate that a localized experime ntal tooth movement initiates a more generalized blood flow response i n the periodontal ligament, dental pulp and alveolar bone.