CAPACITY OF PERIODONTAL VESSELS ON PRESSURE AND TENSION SIDES OF TEETH MOVED BY ORTHODONTIC APPLIANCES

¹ Department of Anatomy, Western Reserve University, Cleveland, Ohio

In a 10-year old macaque the method of weighed paper cut-outs was used to compare the vascularity of the periodontal membrane on pressure and tension sides of teeth moved by orthodontic appliances. Though the number of vessels on opposite sides is approximately equal, the vascularity of the tension side is greater than that on the pressure side in proportion to the force applied. For example, for the upper canines moved by the fairly strong continuous force of a lingual expansion arch wire the tension sides of the periodontal membranes have respectively 6.3 and 3.7 times richer blood supply than the pressure sides. A lower first molar, subjected to the brief action of a separating wire, has 3.0 times richer blood supply on its tension side. The vascularity of opposite sides of the periodontal membranes approaches equality in the adjoining lower second molar and in incisors and premolars used as controls. In our serial sections the vessels on the tension side are markedly larger than those on the pressure side, but all vessels retain their cylindrical form. The equality of number of vessels with open lumina on opposite sides is due to greatly increased numbers of capillaries in regions of bone resorption.