Evidence that the response to applied forces of continuously erupting rat incisors contains more than one component.

Forces (2.5-15 mN) applied in a direction that opposed the eruption of rat maxillary incisors made these teeth sink into their sockets at a decreasing rate. Sometimes eruption subsequently restarted from this intruded position while the force was still applied. After the forces were removed, all the incisors extruded, rapidly at first than showing to normal rates of eruption. Forces (2.5-20 mN) applied in a direction that aided the eruption made the teeth rise in their sockets, initially rapidly, then slowing to a steady rate. After the forces were removed, the incisors sank back into their sockets at a decreasing rate. These responses could be separated into two components; rapid movements occurring immediately after applying or removing the forces and slower movements occurring at rates that were maintained as long as the force was applied, which could be regarded as eruption.