How is age determination done by examining the teeth?
Age determination in animals is the practice used to estimate an animal’s age when birth records are unavailable. These practices are based on examining the structure, number, and wear of the teeth; the horns; the bones’ structure; and the epiphyseal plate. In this blog post, we will explore how age determination is done by examining the teeth.
Tooth Groups According to Their Location
1. Dentes incisivi (Incisors): These teeth, located at the front of the mouth, are used for cutting food to make it easier to chew. In ruminants, they are used to cut grass.
2. Dentes canini (Canines): These sharp teeth are located next to the incisors in the front part of the mouth. In carnivorous animals, they are used to tear tough food.
3. Dentes premolares (Premolars): Known as bicuspids in humans, these teeth are located just in front of the molars.
4. Dentes molares (Molars): Located at the back of the mouth, molars are used to crush and grind food during chewing.
Teeth are divided into two categories: deciduous (Dentes decidui) and permanent (Dentes permanentes), which replace the deciduous teeth after they fall out. The structure and number of teeth vary between animal species.
Carnivores have ‘Brachydont’ teeth with well-developed roots. Tooth development stops once the teeth have fully erupted. Since the upper dental arch is wider than the lower arch, the upper teeth are larger than their counterparts in the lower jaw. In carnivores, deciduous teeth begin to emerge around the 3rd week after birth and are fully erupted by the 3rd month.
Dental Formula in Dogs:
– Deciduous Teeth: 2 (I3/3, C1/1, P3/3) = 28
– Permanent Teeth: 2 (I3/3, C1/1, P4/4, M2/3) = 42
In dogs:
– 2-3 months: The deciduous incisors begin to separate from one another, and wear starts to appear on the teeth.
– 3-4 months: Flattening is observed on the facies incisal surfaces of the incisors.
– 4-5 months: Deciduous teeth start to fall out, and permanent teeth emerge around 6-7 months.
The first premolar (DP1) erupts at 4-5 months and remains as a permanent tooth throughout life.
– At 6 months: The dentition of deciduous teeth is completed by 6-8 weeks.
– At 1.5 years: The protrusions on the lower incisors (I1) disappear. At 2.5 years, they also disappear on the lower I2 incisors.
– At 3.5 years: The protrusions on the upper I1 incisors disappear. At 4.5 years, they also disappear on the upper I2 incisors.
– At 5 years: The surfaces of the I1 and I2 teeth become rectangular, and light wear is observed on the lower I3 incisors.
– At 6 years: The lower I3 incisors lose their protrusions, and the canine teeth start to wear down.
– At 12 years: The I1 teeth fall out, and by 16 years, all incisors are lost. At 20 years, canine teeth also begin to fall out.
Dental Formula in Cats:
– Deciduous Teeth: 2 (I3/3, C1/1, P3/2) = 26
– Permanent Teeth: 2 (I3/3, C1/1, P3/2, M1/1) = 30
In cats, deciduous teeth start to emerge at 2-3 weeks of age, with the incisors being the first to appear and completed by 4 weeks. Permanent teeth begin to emerge at 15-17 weeks, and the canines at 4-5 months. By 6 months, all permanent teeth are fully erupted, and by 7 months, the development is complete.
Tiger tooth anatomy
Horse Dental Formula:
– Deciduous Teeth: 2 (I3/3, P3/3) = 24
– Permanent Teeth: 2 (I3/3, C1/1, P3/3, M3/3) = 40
Stallions have 40 teeth, while mares have 36, as females generally lack canines, though they can appear as rudimentary. Horse teeth are of the ‘Hypsodont’ type, meaning they continue to grow throughout life. Therefore, dental rasping may be required when necessary. Age determination in horses is done by examining deciduous and permanent teeth between the ages of 0-4, and wear patterns during chewing in later years. The infundibulum, dental star, and Galvayne’s groove (for ages 10-30) are important for evaluating wear.
Deciduous incisors are smaller and have a whitish color. When touched, they are loose and wobbly. Permanent teeth, on the other hand, are larger, yellowish in color, and slightly curved forward. The front surface of permanent teeth features a groove running along the tooth.
In horses:
– At 0-2.5 years: Deciduous teeth emerge, and the infundibulum on these teeth begins to wear away. At 2.5 years, the lower front deciduous incisors fall out.
– At 3 years: Permanent lower front incisors emerge. At 3.5 years, the lower middle deciduous incisors fall out.
– At 4 years: Permanent lower middle incisors emerge. By 5 years, the permanent lower back incisors appear.
– Between 5-8 years: The infundibulum on the lower incisors disappears. After 8 years, the infundibulum on the upper incisors disappears, and changes occur in the dental star and groove.- If the infundibulum is worn away on the upper front incisors, the animal is approximately 9 years old; if it is worn away on the middle incisors, the animal is around 10 years old; and if it is worn away on the last incisors, the animal is about 11 years old.
– After 15 years, the wear surface on all lower incisors begins to take on a triangular shape, and the dental groove reaches halfway down the tooth.
– At 20 years old, the dental star is square-shaped, and the groove reaches the full size of the tooth.
Dental Formula in Cattle:
– Deciduous Teeth: 2 (I0/3, C0/1, P3/3) = 20
– Permanent Teeth: 2 (I0/3, C0/1, P3/3, M3/3) = 32
In cattle, there are no upper incisors. Deciduous teeth are smaller and whiter compared to permanent teeth, loosely attached to the jaw, and mushroom-shaped. Permanent teeth are more yellow, sturdier, and rectangular/square-shaped, making it easy to differentiate them from deciduous teeth. The replacement of deciduous teeth with permanent ones is referred to as ‘cap shedding‘ and typically occurs after 2 years of age.
– At 1.5 years, the deciduous teeth have fallen out or are about to fall out, and the first permanent incisors begin to emerge.
– By 2 years, the permanent front incisors are fully erupted. At 2.5 years, the first middle deciduous incisors fall out, and by 3 years, the permanent middle incisors come in.
– At 3.5 years, the second set of middle deciduous incisors fall out, and by 4 years, the permanent second middle incisors emerge.
– At 4.5 years, the last set of deciduous incisors fall out, and by 5 years, they are replaced by the permanent last incisors.
– In cattle, age determination based on teeth becomes unreliable after 6 years, but it can be done accurately up to 6 years of age.
Dental Formula in Sheep:
– Deciduous Teeth: 2 (I0/3, C0/1, P3/3) = 20
– Permanent Teeth: 2 (I0/3, C0/1, P3/3, M3/3) = 32
Sheep share the same dental formula as cattle. Deciduous teeth emerge at birth or shortly after and remain until about 1 year old. The first pair of permanent teeth appear at 1-1.5 years, the second pair at 1.5-2 years, the third pair at 2.5-3 years, and the fourth pair at 3.5-4 years. By age 6, notches form between the front incisors.
Teeth, which vary between species, are not only important for age determination but are also crucial for the overall health of our pets. Therefore, regular dental check-ups for our pets should not be neglected.
This blog post has been verified by Doctor of Veterinary Medicine Esma Hande SEVİŞ.
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