The graphic representation on the
right shows the 'step' behind the 3rd molar (called the 4th premolar).
The typical cause of this is the fracture of one or more caps or teeth
followed by irregular wear. Another common cause is the retention
of one or more caps. If a cap stays on top of a permanent tooth for
much longer than it should, the opposing tooth will be worn more than it
would if the cap was shed nomally. Sadly, fracture of teeth is often
caused by people attempting to examine the mouth. In order to keep
the mouth open some individuals use a rod with a steel 'prop' which is
wedged between the molars; the horse risks fracturing one or more teeth
when it bites on such a device. Those attempting to use the device
should be prevented from doing so.