1. Occurrence of permanent teeth
Permanent teeth start growing at one years old and continues growing through six years of age.
2. Disappearance of cups
The disappearance of cups starts at 7 years of age and ends at 30 years of age.
3. Angle of incidence
The angle of incidence of contact changes from 160 to 180 degrees, most horses develop notch at 7.
4. Shape of the surface of the teeth
At 8-12 years the back surfaces become oval, then triangular at 15 years. At 20 years old teeth may be twice as deep to front to rear they are wide.