Dental Formula
Deciduous Permanent
Horse 2 ( Di 33 Dc 33 Dp 33 ) = 24 2 ( I 33 C 11 P 3-43 M 33 ) = 40-42
Cow, Sheep, Goat 2 ( Di 03 Dc 01 Dp 33 ) = 20 2 ( I 03 C 01 P 33 M 33 ) = 32
Pig 2 ( Di 33 Dc 11 Dp 33 ) = 28 2 ( I 33 C 11 P 44 M 33 ) = 44
Dog 2 ( Di 33 Dc 11 Dp 33 ) = 28 2 ( I 33 C 11 P 44 M 23 ) = 42
Cat 2 ( Di 33 Dc 11 Dp 32 ) = 26 2 ( I 33 C 11 P 32 M 11 ) = 30
Shape of the incisor teeth is often used; the occlusal surface is a long oval in young animals, but as the teeth wear, it becomes round and then triangular, with the apex toward the lingual side. Additionally, the angle of the incisors changes from nearly perpendicular to more or less parallel as the animal ages and the teeth wear.

The more useful signs are arranged chronologically in the following list:

5 yr : I 1 and I 2 level, labial border of I 3 in wear.
6 yr : Cup gone from I 1.
7 yr : All lower incisors level. Cup gone from I 2. Hook in upper I 3. Cement has worn off, changing the color from yellow to bluish white.
8 yr : Dental star appears in I 1. Cup gone from I 3.
9 yr : I 1 round.
10 yr : I 2 round. The distal end of Galvayne’s groove emerges from the gum on upper I 3.
13 yr : The enamel spot is small and round in the lower incisors. The dental stars are in the middle of the table surfaces.
15 yr : Dental stars round, dark, and distinct. Galvayne’s groove halfway down.
16 yr : I 1 triangular.
17 yr : I 2 triangular.Enamel spots gone from lower incisors.
 
Cattle : As in horses, signs of wear are much less reliable than eruption for estimation of age. Eruption times of the permanent incisors are often used to estimate the age of calves, particularly show calves. Except for very aged animals, the teeth are rarely used to determine the age of adult cattle.
 
5 yr : All incisors are in wear. The occlusal surface of I 1 is beginning to level; that is, the ridges on the lingual surface are wearing out and the corresponding border of the occlusal surface is becoming a smooth curve instead of a zigzag line.
6 yr : I 1 is leveled and the neck is visible.
7 yr : I 2 is leveled and the neck is visible.
8 yr : I 3 is leveled and the neck is visible.
9 yr : C is leveled and the neck is visible.
 
Dogs : The data given below were found reliable in ~90% of large dogs. Small dogs (especially “toy” breeds) and dogs with undershot or overshot jaws are more variable.
 
1½ yr : Cusps worn off lower I 1.
2½ yr : Cusps worn off lower I 2.
3½ yr : Cusps worn off upper I 1.
References:
Philippine Veterinary Drug Directory (PVET) 16th Edition. (2014). Medicomm Pacific, Inc.