Shortly before five years old the corner milk-teeth are shed, and permanent ones appear, but as shells only, having no internal walls.
At about six years old the inner wall of the corner teeth has grown up level with outer wall.
The tusks appear at about three and one half years, are matured at six, and then begin to wear away. Usually absent in mares.
Between three and five years the marks or cups in the permanent teeth are very plain.
At six the marks are well worn in centre teeth.
At seven the marks disappear from centre teeth, are well worn in the two next, but plain in corner teeth.
At eight the marks have all disappeared, except in corner teeth, in which they are worn.
At nine the marks are usually gone from all the incisor teeth in lower jaw.
The temporary incisors in upper jaw fall out usually a little earlier than those in lower jaw. The permanent incisors in upper jaw are longer and larger than the lower, and the mark is deeper and remains longer than in the lower teeth.
Beyond nine years the teeth become angular and foul, the tusks worn, and the age only to be determined accurately by much experience and observation.