The following changes in the shape and appearance of the incisor teeth of
the average horse occur in the different years. Unless otherwise mentioned,
the statements made regarding the appearance and wear on the table surfaces
apply to the lower incisor teeth.

SIX YEARS.--The table surfaces form the most accurate guide. The cups of
the nippers tend to an oval form. The corner teeth have been in wear one
year at this time. The cup is deep and the posterior margin may show little
wear. It is not uncommon to meet with corners that possess irregularly
developed tables, and have cups with posterior margins that are thin and do
not come into wear until later. For this reason, it is not best to depend
on the appearance of the corner teeth alone.

SEVEN YEARS.--The teeth are usually whiter than the previous year. The
profile of the upper corner teeth shows a notch in the posterior portion of
the table surface. This is due to the superior corners overhanging the
inferior corner teeth posteriorly, resulting in this portion not wearing
away. This notch is sometimes slightly in evidence the previous year. The
cups in the corners are smaller and the worn surface larger than at six.
The nippers show oval table surfaces and the dividers are beginning to take
on this shape. The shifting of the cups toward the posterior portion of the
tables of the nippers and dividers is noticeable.

EIGHT YEARS.--As viewed from the side, the profile of the teeth shows a
very noticeable increase in the obliquity with which they meet. The
posterior borders of the corners show considerable wear. The notch in the
superior corners is still present, but as the teeth come more nearly in
apposition it may begin to disappear. All of the inferior tables are level.
The nippers and dividers are oval in shape, and the cups have become