Page 749 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

724 CHAPTER 4

VetBooks.ir 4.3 Age-related changes in the
appearance of teeth with
eruption and ageing
The eruption ages of equine teeth are shown in
Table 4.1. These are typical for a Thoroughbred
1 1 2 2 horse and are breed and individually variable. Since
accurate ageing using records commenced (2009
in the UK), the inaccurate estimation of age using
6 6 7 7 occlusal features has become obsolete.
3 3 4 4 5 5 As the occlusal surfaces of the teeth are worn
during food prehension and mastication, their
appearance changes. The cementum and enamel
covering the surface is worn as the horse chews.
Fig. 4.3 Occlusal view of mandibular tooth This results in exposure of the primary den-
411 showing absence of infundibula and enamel, tine on the occlusal surface and the enamel takes
peripheral cement, primary and secondary dentine, on the appearance of a continuous raised ridge
overlying pulp horns numbered 1–7.
surrounding the dentine and bounded by the
peripheral cementum. In the incisors and maxil-
the tooth in the alveolus and provide compressive lary cheek teeth the infundibula become raised
elasticity and resistance during mastication. The concentric circles or crescents.
Sharpie’s fibres insert into a layer of dense lamellar In the incisor the central enamel of the infundib-
alveolar bone known as the lamina dura denta, which is ulum (dental mark) is filled with non-regenerative
radiographically identifiable (Fig. 4.4). infundibular cement and the invagination (dental
cup) becomes filled with organic material, which
Dental nomenclature undergoes oxidation leading to a dark appearance. As
The Triadan system is now in widespread use for the tooth erupts the diameter of the infundibulum
equine dental nomenclature and avoids the confu- becomes narrower and the amount of organic mate-
sion between the notation of the premolars and rial becomes reduced, resulting in gradual oblitera-
molars as the cheek teeth 1–6 (starting with the tion of the dental cup. Eventually in ageing horses
second premolar) as preferred by many authors in (9–11 years), the infundibular enamel is worn away
Europe, and the classification into premolars and in the central incisors first, followed by the middle
molars as preferred by authors in the USA. Under and corner incisors, and the dental mark eventually
this system each tooth has a unique identification disappears to leave an occlusal surface consisting
number as shown in Fig. 4.1. entirely of dentine.

4.4

Fig. 4.4 Lateral radiograph of
a hemimandible of a 7-year-old
horse showing dental roots and
mesiodistal compression at the
crown.