Eruption was studied by experimentally impacting and releasing permanent premolars in puppies. Eruption rates of both normal and experimentally delayed teeth were calculated from weekly radiographs. The rate of normal eruption is triphasic and similar to a normal growth curve. It has an initial slow exponential rate which changes to a more rapid exponential rate followed in turn by a terminal plateau. All of the teeth released from impaction erupted and their rates exceeded or equaled the normal rate.
The morphology of the bony trabeculae beneath the erupting teeth and the relative amount of soft tissue between the bone and teeth are expressions of the eruptive rate. The trabeculae around rapidly erupting teeth are thinner, more delicate and more widely separated from one another than those of slowly erupting teeth. Trabecular orientation aligns with the direction of eruption, showing not only its vertical component, but also whether the tooth moved mesially or distally during eruption.