Page 750 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.1 The upper gastrointestinal tr act 725

VetBooks.ir Table 4.1 Eruption ages of equine teeth

TOOTH TRIADAN NUMBER ERUPTION AGE IN WEAR
Deciduous incisors
Central 501 3 days
Middle 502 3 weeks
Corner 503 3 months
Deciduous premolars
1 cheek tooth 506 birth
st
2 cheek tooth 507 birth
nd
rd
3 cheek tooth 508 birth
Permanent incisors
Central 101 (2, 3, 401) 2.5 years
Middle 102 3.5 years
Corner 103 4.5 years
Canines 104 5 years
Permanent premolars
st
1 premolar (wolf tooth) 105 2–2.5 years
2 premolar (1 cheek tooth) 106 2–2.5 years 2.5–3 years
st
nd
3 premolar (2 cheek tooth) 107 3–3.5 years 3.5–4 years
nd
rd
rd
th
4 premolar (3 cheek tooth) 108 4 years 4.5 years
1 molar (4 cheek tooth) 109 1–1.5 years 1.5–2 years
th
st
2 molar (5 cheek tooth) 110 2–2.5 years 2.5–3 years
th
nd
3 molar (6 cheek tooth) 111 3–3.5 years (later in miniature breeds) 3.5–4 years
rd
th
As the occlusal surface is worn the pulp cavity unreliable. The angle between the upper and lower
would eventually be exposed. Odontoblasts lin- incisors becomes more acute with age and this is
ing the pulp chamber produce secondary dentine reflected in changes in the shape of the occlusal sur-
in the pulp cavity, which maintains the separation face from oval in young horses, to triangular or trap-
of the pulp from the oral cavity. The secondary ezoid in geriatric horses and ponies. Some variation
dentine becomes darkly stained and appears rostral has also been described between different breeds of
to the ‘dental mark’ as a ‘dental star’, which appears horse.
between 8 and 10 years of age commencing at the Eruption of the cheek teeth with age results in
central incisors. The exact age at which the appear- some modelling of the maxilla and mandible as the
ance changes varies between individuals and breeds tooth erupts. In horses aged 2–4 years old the tooth
and it is generally accepted that in contrast to histor- is growing in length at its apical aspect and in the
ical belief, these changes are not sufficiently accurate process of erupting, which results eventually in
or reliable to be used as definitive means of ageing the exfoliation of the deciduous premolars. During
the animal. Knowledge of such changes is useful for this time the tooth exhibits its maximal length and
checking documentation and can be used to place occupies the full depth of the bone in which lies the
an individual in an age range based on the appear- alveolus. In 2- and 3-year-old horses and ponies,
ance of incisors. Other features such as the timing the mandibular medulla is full to its depth with
of appearance of ‘hooks’ and ‘Galvayne’s groove’ are the reserve crowns of the erupting -07s and –08s,