Articles

Deciduous Teeth in Horses

by Larry Kimberlin, D.V.M. FAVD, CVPP,

DAVDC

A very big issue for every horse under five years of age is the eruption of the baby or deciduous teeth and the formation of a full set of permanent teeth. This is also one of the ways that the age of a young horse can be determined. The first five years are very busy years in the horse’s mouth. There can be up to forty four teeth that erupt and grow into occlusion. This includes twelve incisors, four canine teeth, fourteen premolars and twelve molars. There are so many teeth coming and going, it is hard to tell what is what without a scorecard! The foal is usually born without incisors (the front teeth that are seen when you lift up the lip). Horses have twelve incisors – three upper pair and three lower pair. The first incisors usually break through the skin in about one week. These are the central incisors. The next pair – the middle incisors – erupt at about eight weeks and the last pair – called the lateral incisors – come in at about eight months. By one year of age all the incisors are in. The deciduous incisors are much smaller than the permanent incisors that will take their place. The permanent incisors are a good way to age a young horse. The permanent incisors come in at 2 1/2 years, 3 ½ years and 4 ½ years respectively. This photo illustrates a 4 year old horse with permanent central and middle incisors and deciduous lateral incisors (arrows point to deciduous teeth). The young horse is born with twelve deciduous premolar cheek teeth. These teeth are also replaced by the permanent premolars in a similar fashion to the incisors. These teeth come in at about 2 years, 2 ½ years and 3 years. These times are approximate and can vary by 2-4 months ( depending on the breed) - but are pretty consistent . This picture illustrates the permanent premolars coming in below the deciduous. When permanent teeth come in they push the deciduous tooth out of the way – disrupting its blood supply and causing it to loosen and “shed”. The baby teeth sometimes do not shed as they should and remain attached to the permanent tooth. These are called caps and cause pain and chewing problems due to the uneven surface similar to having a popcorn kernel caught in your teeth. The timely shedding and eruption of the permanent teeth is very important to the long term health of the mouth. If deciduous teeth do not shed at the proper time the permanent teeth that are to replace them will become impacted and come in crooked. This will cause bite problems and discomfort for the horse. By knowing when the permanent and baby teeth come in you can tell the age of a young horse within a few months. Whenever an owner complains of chewing problems or bitting problems in a horse under five years of age the first thing we look for are retained caps. The picture below shows a skull with a view of caps and the permanent teeth coming in underneath. It is very important to have your horse’s teeth checked yearly during these formative years. If there are problems with retained deciduous teeth or impaction you may need to have them checked two to three times a year. Just as in human dentistry it is much better to correct tooth problems when they are forming than to correct them later. It is better to get braces in junior high than in college! We don’t have space to cover all there is to know about aging and orthodontics in this article, but this will give our readers the basics of how the dentition works and hopefully stimulate interest in having the young horse checked by a qualified dentist to promote health and prevent problems. If you have questions you can contact your dentist or contact me. Dr. Kimberlin is the Co-author of Atlas of Clinical Imaging and Anatomy of the Equine Head