title: Experimental intrusion of rat incisors with continuous loads of varying magnitude.
abstract: The present investigation deals with the relationship between continuous intrusive loads and the rate of intrusion of rat incisors. A method for the application of constant, defined loads by means of a closed coil spring is described. In seventeen rats the left mandibular incisor was shortened to prevent occlusion. The animals were exposed to direct light, medium, and heavy intrusive loads for a period of 12 days. Light loads (1.5 to 8.0 Gm./cm.2) did not cause active intrusion of the teeth. Medium loads (12.0 to 18.5 Gm./cm.2) initially elicited marked intrusion, followed by a short rest period after which the intrusive movement progressed steadily at a daily rate of about 25 micrometers. Heavy loads (30.5 to 32.0 Gm./cm.2) brought about active intrusion, which commenced only after 8 days of force application. The medium loads, having a magnitude in the range of rat systolic blood pressure, proved to be optimal for the intrusive movement.
mesh_terms: D000818:Animals; D003799:Dental Stress Analysis; D005260:Female; D007180:Incisor / Q000502:physiology*; D009967:Orthodontic Appliances; D051381:Rats; D011919:Rats, Inbred Strains; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000379:methods*