| Fossil samples dating back as far as 55 million | | | | swallows. |
| years ago can help us determine how long horses | | | | Horses can only chew on one side of their mouth |
| (on average) lived. 55 million years ago the | | | | at a time, changing from one side to the other |
| average longevity of the hyracotherium was 5 | | | | would mean they would drop the food. |
| years of age. 20 million years ago during the | | | | A horse should be comfortable to eat on both |
| Miocene, analysis indicates longevity of up to 15 | | | | sides of their mouth. |
| years. 10 million yeas ago during the Pliocene | | | | A horse has a great amount of lateral excursion |
| period Equus population was thought to live up to | | | | (sideways movement) within their jaw. When |
| 25 years. | | | | eating lush feeds there is a greater amount of |
| Horses are herbivores and there teeth are | | | | movement than when the horse eats dry feeds. |
| designed for breaking down the hard structures | | | | The temporomandibular joint |
| like cellulose found commonly in the horses diet. | | | | This is the joint joining the lower jaw to the head. |
| They have what are known as hypsodont teeth, | | | | It enables the jaw to move and laterally has a |
| meaning continuous eruption of the reserve | | | | great range of movement; up and down the |
| crown of the tooth. This matches the loss of | | | | movement is limited. Unlike carnivores horses |
| tooth from the grinding down caused during | | | | have a transverse power stroke in a lingual |
| mastication. | | | | direction (towards the tongue), associated with |
| Numbers of teeth | | | | their mastication cycle. Joints should wear evenly. |
| Horses have 24 deciduous teeth (non permanent) | | | | If horses' teeth wear unevenly, it can cause pain |
| and 36 to 44 permanent. The numbers of | | | | within this joint due to uneven pressures being |
| permanent teeth can vary mainly depending on | | | | placed on it. |
| gender. Male horses normally have 4 canine teeth; | | | | Structure of equine teeth |
| mares are often seen without any. 4 wolf teeth | | | | ENAMEL |
| can sometimes be seen in horses although 2 on | | | | Enamel is the hardest and most dense substance |
| each arcade on the upper jaw are most common. | | | | in the body. It has a very high (96 - 98 %) |
| Male and female horses alike can show wolf teeth. | | | | mineral content making it almost translucent. Due |
| Types of teeth | | | | to the absence of cellular inclusions (unlike dentine |
| There are 5 different teeth that can be found | | | | or cement) enamel can be regarded as dead |
| within horses' mouths. | | | | tissue. It has no ability to repair itself once its |
| INCISORS | | | | ameloblasts die off. Enamel varies in thickness up |
| These are the teeth situated at the very front of | | | | to 3 times throughout areas of the tooth parallel |
| the horses' mouth. They are used in a pincer like | | | | to the long axis of the jaw but remains constant |
| action for nipping biting and defence. There are 12 | | | | throughout the length of the tooth. Invaginated |
| in total, 6 on the top jaw 6 on the lower jaw. | | | | folds on the occlusal surface give strength to the |
| Incisors are used to age horses. The occlusal | | | | tooth where the softer dentine becomes |
| surface of each tooth changes in appearance | | | | depressed. |
| dependant on how old the horse is. Initially these | | | | DENTINE |
| teeth are more oval in shape but as the horse | | | | The bulk of the tooth is made up of dentine; a |
| ages the shape of the incisors become triangular. | | | | cream coloured softer tissue comprising of |
| The Galvaynes Groove is seen on the corner | | | | approximately 70% minerals, 30% organic |
| incisor teeth. This is a longitudinal line that appears | | | | compounds and water. The type of tooth (shape |
| also used when ageing horses | | | | and size) along with the compressibility and |
| CANINES | | | | percentages of different organic components |
| Canine teeth are situated caudally to the incisors. | | | | contributes to its overall strength. |
| There can be 4 in total. They are curved in shape | | | | The presence of dentine and cement dispersed |
| with most of the tooth still under the gum line. | | | | between the hard enamel folds forms a very |
| They can be up to 7cm in length. They are | | | | strong durable structure suitable for its purpose. |
| relatively simple teeth that the ancestors of | | | | Odontoblasts can synthesize dentine throughout |
| today's horses' would have used for defence. | | | | their lives. This prevents the occlusal surface of |
| FIRST PREMOLAR (WOLF TOOTH) | | | | the tooth from exposing the pulp during normal |
| The wolf tooth is a small simple brachydont tooth, | | | | attrition. |
| (short crown) although it can range in size from | | | | There is a close working relationship between |
| 1-25cm. There can be 4 in total. The roots of this | | | | dentine and pulp with some of the structures of |
| tooth can vary from being non existent to being | | | | each working through each other. This sometimes |
| up to 30mm in length. These teeth can | | | | leads to them acting as a single unit. Dentine is |
| sometimes be found to erupt in varying places | | | | considered a sensitive living tissue. |
| throughout the horse's mouth although more | | | | Young tooth before eruption. Note the presence |
| commonly they are situated just in front on the | | | | of cement and enamel covered by the dental sac |
| first cheek tooth. | | | | and the large pulp chamber. |
| PREMOLARS AND MOLARS (CHEEK TEETH) | | | | PULP |
| Cheek teeth form 4 rows of 6 teeth that are | | | | Pulp is soft tissue within the tooth that contains a |
| accommodated in the maxillary (top jaw) and | | | | connective tissue skeleton consisting of |
| mandibular (bottom jaw) bones. These teeth are | | | | fibroblasts, thick collagen, connective tissue cells i.e. |
| more rectangular in shape when a cross section is | | | | Odontoblasts, numerous blood vessels, allowing for |
| taken (down the transverse plane). The teeth on | | | | continuous dentine deposition and nerves. |
| the maxillary arcades (rows) are wider and | | | | Pulp is found in large quantities in and around |
| squarer than teeth on the mandibular arcades | | | | developing teeth. With age more secondary |
| which are narrower and more rectangular. Ridges | | | | dentine is laid down as development of the tooth, |
| are seen on the buccal (outside) edges of the | | | | requiring large quantities of pulp, ends. This makes |
| maxillary arcades in particular. Many dental | | | | them stronger and more solid. |
| overgrowths are a common occurrence here. | | | | Later in the tooth development the pulp chamber |
| Tooth growth is seen on average at 2-4mm per | | | | has formed two horns due to the laying down of |
| year. The occlusal surfaces of these teeth are | | | | dentine within the pulp chamber. |
| ridged to increase the amount of surface area for | | | | CEMENT |
| breaking down food. These teeth are used to | | | | Cement / cementum are a cream coloured |
| grind foodstuffs in a circular sideways action. | | | | calcified dental tissue characteristically similar to |
| Mastication (the chewing cycle) | | | | bone. Its mineral and inorganic compound make up |
| The horses head is Anisognathic, | | | | are similar to dentine and give it its flexibility. The |
| (a-nee-so-nay-thic). Basically the top jaw is wider | | | | extensive collagen fibres found within the inorganic |
| than the lower jaw. Mastication begins using the | | | | component of cement are what attach the |
| lips and incisors to nip the e.g. grass. The horse | | | | cement to the alveolar bone, stabilising the tooth. |
| whilst grinding the grass between its cheek teeth | | | | Cement is a living tissue nourished by the |
| uses its muscular tongue and ridges on the upper | | | | vasculature of the periodontal ligament (attaches |
| pallet to gradually work the food to the back of | | | | cement on tooth to socket). |
| its mouth in a circular (spiral) motion and then | | | | |