EFFECTS OF AXIALLY-DIRECTED EXTRUSIVE LOADS ON MOVEMENTS OF THE MANDIBULAR INCISOR OF THE RABBIT

Using a variable capacitance displacement transducer to record tooth movements continuously, the effects of applying axially-directed extrusive loads of up to 200 g (2 N) on movements of the mandibular incisors of 6 male Californian rabbits (average weight 3.4 kg) were studied. On applying a load of 1 g (0.01 N) or more, a biphasic movement of the tooth was recorded which could be clearly distinguished from eruptive movements. Initially, a rapid, almost instantaneous, extrusive phase was observed, followed by a 2nd phase during which there was a more graudal extrusion. A similar, but intrusive, biphasic recovery response was observed on removing the load. The responses to the extrusive loads were force-dependent. Immediately after the animals were killed, responses were similar to those in live animals.