Structure of equine teeth ENAMEL -Enamel is the hardest and most dense substance in the body. -It has a very high (96 †98 %) mineral content making it almost translucent. -Due to the absence of cellular inclusions (unlike dentine or cement) enamel can be regarded as dead tissue. It has no ability to repair itself once its ameloblasts die off. -Enamel varies in thickness up to 3 times throughout areas of the tooth parallel to the long axis of the jaw but remains constant throughout the length of the tooth. Invaginated folds on the occlusal surface give strength to the tooth where the softer dentine becomes depressed. DENTINE -The bulk of the tooth is made up of dentine; a cream coloured softer tissue comprising of approximately 70% minerals, 30% organic compounds and water. -The type of tooth (shape and size) along with the compressibility and percentages of different organic components contributes to its overall strength. -The presence of dentine and cement dispersed between the hard enamel folds forms a very strong durable structure suitable for its purpose. -Odontoblasts can synthesize dentine throughout their lives. This prevents the occlusal surface of the tooth from exposing the pulp during normal attrition. -There is a close working relationship between dentine and pulp with some of the structures of each working through each other. This sometimes leads to them acting as a single unit. -Dentine is considered a sensitive living tissue. Young tooth before eruption. Note the presence of cement and enamel covered by the dental sac and the large pulp chamber. PULP -Pulp is soft tissue within the tooth that contains a connective tissue skeleton. --fibroblasts, --thick collagen, --connective tissue cells i.e. Odontoblasts, --numerous blood vessels, allowing for continuous dentine deposition. --nerves. -Pulp is found in large quantities in and around developing teeth. -With age more secondary dentine is laid down as development of the tooth, requiring large quantities of pulp, ends. This makes them stronger and more solid. Later in the tooth development the pulp chamber has formed two horns due to the laying down of dentine within the pulp chamber CEMENT -Cement / cementum are a cream coloured calcified dental tissue characteristically similar to bone. -Its mineral and inorganic compound make up are similar to dentine and give it its flexibility. -The extensive collagen fibres found within the inorganic component of cement are what attach the cement to the alveolar bone, stabilising the tooth. -Cement is a living tissue nourished by the vasculature of the periodontal ligament (attaches cement on tooth to socket). Mastication †the chewing cycle The horses head is Anisognathic, (a-nee-so-nay-thic). The top jaw is wider than the lower jaw. Mastication begins using the lips and incisors to nip the grass. He grinds the grass between its cheek teeth and uses his tongue and ridges on the upper pallet working the food to the back of the mouth. He does this gradually in a circular (spiral) motion and then swallows. A horse should be able to eat equally on both sides of its mouth When problems arise within the horses mouth this causes the teeth to not grind against each other (occlude) correctly. This is known as mal-occlusion. Mal-occlusion can cause: -Incorrect table angles of teeth arcades -Restricted side-to-side action of the lower jaw -Lacerations to cheeks -Uneven pressures in the temporomandibular joint (joining the two jaws) causing pain -Locking up of natural, normal movement within the horses head, creating pain and often problems when ridden. Most of these painful and performance reducing problems go unnoticed and the horses reactions, due to these problems, is put down to bad behaviour instead of a symptom of discomfort
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