Some Histopathologic Changes in the Hamster as the Result of a Continuously Acting Orthodontic Appliance

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Abstract
An orthodontic band with an eyelet was contoured to encompass and cemented onto both mandibular central incisors of hamsters. Retraction coil springs consisting of 13 turns of 0.009 inch stainless steel spring wire with a 0.030 inch core were constructed and fastened to the eyelet and looped around the first mandibular molar. Each coil spring was activated to apply 4 ounces of applied force to each of the 2 first molar teeth. Post-operative periods consisted of 1,2,3,5,7, and 9 days with 5 animals in each group. Serial, 10-u, longitudinal sections through the mandibular molar region were made and studied. During the first 3 days orthodontic tooth movement was instituted on the first molar teeth. This was evidenced by an area of pressure necrosis in which the tissue was devoid of cell nuclei in the upper 20% of the peridental membrane adjacent to the alveolar crest of the interseptal bone mesial to the first and the interradicular bone mesial to the distal root. The aleveolar bone surrounding the 2d and 3d molars was undisturbed. During the period of 5 to 9 days the pressure necrosis associated with the 1st molar persisted. The alveolar bone surrounding the 2nd and 3d molars, however, indicated that there had been a reversal of the normal distal drift to a mesial drift.