Abnormal Wear of Teeth

Introduction

Abnormal wear of teeth in herbivores may result from irregular grinding of molars as well as from periodontal disease. This is especially a problem in horses but occurs in any animal with continuously-growing teeth.

In horses, some common stereotypical behaviours such as crib biting or wind sucking may also have an impact on tooth wear.

Pathophysiology

The horse's upper cheek teeth extend as much as one-half the width of a tooth outside the lower cheek teeth. Chewing wears the teeth where they contact each other, and if the jaw excursions are not wide enough, sharp edges can form on the lingual aspect of the mandibular teeth and on the buccal aspects of the maxillary molars and may cause quite severe oral lacerations.

A condition sometimes known as “shear mouth” can occur when the grinding surfaces of all cheek teeth are severely sloped with extremely sharp points and an abnormal chewing motion.

Loss of a tooth can also cause problems as the opposing tooth is not worn down and may become too long and hinder chewing.

Malocclusion of teeth may also occur as a result of malformations of the jaws.

Mandibular brachygnathism (parrot mouth): horses tend to have hooks at the front of the first upper cheek teeth and at the back of the last lower cheek teeth.

The opposite occurs in horses with mandibular prognathism (sow mouth).

Vices such as crib biting will lead to characteristic abnormal wear patterns such as increased wear of the upper front incisors due to the horse biting down on the stable door or other objects.

Treatment

Treatment of wear disorders and overgrowths in horses generally involves rasping or floating of the teeth by hand or using motorised equipment. Molar cutters or burrs may also be used for larger hooks.

Floating of sharp points using hand rasps follows several rules:

the blades of the rasps should be in solid tungsten carbide as these can be re-sharpened and can last a long time

different handles with different angulations are needed to reach all parts of the mouth. For the maxillary teeth, open-angled tools are used at the front of the mouth, straight rasps in the middle and closed-angled tools at the back. For the mandibular teeth, straight rasps should be used for the front and then upward-curving rasps for the back.

For larger hooks which require more rasping, several aspects are important:

a good light source is necessary, usually a head torch

the tool should only be used for short periods of time in the same place as otherwise excessive heat is created which can damage the tooth

pulp exposure should be avoided by regularly checking the aspect of the tooth which is being burred.

teeth occlusal angle should be restored to 10-15°

Any vices should be declared by the vendor if the horse is being sold. If the abnormally worn teeth are causing injury to the horse, floating can be performed to rasp away any sharp edges. Behavioural therapy may be necessary in some cases. Excessive crib biting can lead to tooth fractures and permanent damage to the upper incisors.

Rabbits

Incisor Overgrowth

Cheek Teeth Malocclusion

Abnormal Wear of Teeth Learning Resources
Flashcards Test your knowledge using flashcard type questions	Veterinary Dentistry Q&A 14 Veterinary Dentistry Q&A 19

References

Pascoe, R. (2009) Equine Dentistry RVC Student Notes

Lewis, L. D. (1995) Equine Clinical Nutrition: Feeding and Care Wiley-Blackwell

Furr, M. (2008) Equine Neurology John Wiley and Sons

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