This letter is addressed to all owners of horses, ponies, donkeys, mules, (Equines) with regard to health and well being through good dentition.
The equine in its natural environment is a highly specialised grazing animal, evolved over millions of years to be able to feed on a fibrous/herbaceous diet which must be masticated (chewed) thoroughly before entering the stomach. Today we find that most of domesticated equines in a stabled or managed environment eating processed feeds, (this includes hay) although probably better for the equines system, does not help wear the teeth as nature intended.
The feet, body condition and other things we can see will usually get our immediate attention and care, but because the equines dentition is out of sight many problems can occur without being immediately recognised (out of sight, out of mind). If one could unzip the side of the mouth and take a look inside, you would probably be seeking help from your veterinary surgeon or someone who specialises in equine dental care, or both. I would certainly not advocate that equine owners go putting their hands into their horse’s mouths; this would be most foolish and very dangerous! However what the equine owner can do is look for tell tale signs that all is not well in their equines mouth. Here are just some of them.
Signs to Look For
* Head throwing problems while riding.
* Head tilting while eating or riding.
* Lack of condition, when all other good maintenance programs are in place.
* Bleeding from the mouth
* Bad breath from the mouth or nostrils
* Inability to shift lower jaw from side to side.
* Dribbling of feed.
* Weight loss.
* Excessive salivation or drooling.
* Troubled facial expression.
* Bumps or enlargements of the jaw or face.
* Bad general attitude.
Mastication is the name to describe the process by which the equine chews its food. If you watch the equine eating in a grass paddock for instance, you will see the way it grasps the grass with its lips, then nips the grass with its Incisors (the six upper and six lower teeth just behind the lips) then passing it back onto the Molars (cheek teeth) for grinding. The molars of the lower jaw (Mandible) moving from first one side in a downward outward then upward and inward motion taking up the rotating pattern of chewing once again, downward, outward, upward and inward depositing food once again upon the tongue from the other side until the equine is satisfied the food is
chewed enough and mixed with enough saliva (up to five gallons of saliva per day in an average size horse) to be introduced into the equines digestive tract.
Structure of Teeth
The tooth structure of the equines teeth is made up of three main substances, enamel, dentine, and cementum. There is also a chamber inside the tooth called the pulp chamber which is filled with a gelatinous tissue which contains blood vessels and nerves to feed and nourish the tooth. The long crowned, or Hypsodent teeth of the equine have a generous amount of surplus or reserve crown beneath the gum line (up to two and a half inches molar length below the gum in an average size horse). These grow and then erupt at the same rate as they wear. They have most of their length by the time the horse reaches five years of age, but continue to develop and lay down some new enamel and fill with dentin from the inside. The teeth will continue to lengthen somewhat as they continue the eruption process which is closely correlated to the rate of wear until the animal reaches the age of around twenty five years of age at which time the reserve crown of the tooth is mostly used. The teth get harder with age until the reserve crown of the molars which contains most of the enamel expires, leaving mostly dentin and a root which has little capacity for wear or feeling.
Formation of Dentition
There are four types of horse teeth.
Starting from the front of the mouth;
1. INCISORS (Deciduous/Milk and Permanent).
4. PREMOLARS (Deciduous/Milk and Permanent).
The adult horse (5 years old and up) has twelve incisors, six on the upper jaw (Mascilla) and six on the lower jaw (Mandible) just behind the lips. The male horse has four canine teeth; two on the upper jaw and two on the lower jaw. The female horse may show poorly developed canine teeth. These may be Wolf teeth present (a vestigial first premolar). There are three premolars on each side of the upper and lower jaws, and three permanent molars each side of the upper and lower jaws. The premolars and permanent molars when classed together are called Cheek Teeth. The first and sixth cheek teeth on each side of the upper and lower jaw are angled towards each other so as to squeeze the cheek teeth tightly together to prevent food accumulating between them.
Polydontia. Extra teeth from the normal dentiteum, usually found as seventh cheek tooth but also as an extra incisor. These extra teeth can also be classed as supernumerary teeth.
Problems Associated With Wear.
These can vary between individual equines due to size and shape of head, congenital defects: i.e. parrot or sour mouth, diet, trauma.
Because the lower jaw is narrower than the upper jaw and molar tables (grinding surface of the tooth) of the upper and lower molars are set at an angle to each other sharp points or hooks develop on the outside edge of the upper molars (Buccal edge) and inside edge of the lower molars (Lingual edge). These points and sharp edges on the buccal margins can cause pain and trauma to the sensitive tissue inside of the horse’s cheek. The same can be said about the lingual margins causing pain and trauma to the tongue. These sharp edges can be quite easily removed by having the teeth rasped. In a horse with very sharp and long buccal/lingual margins will change the way a horse tries to eat its food. Later excursion will decrease (sideways travel of the mandible). The mandible will move in a more up and down motion.
Problems Related to Eruptions.
When talking of eruption in equines teeth, this describes the rate at which the crown of the tooth erupts above the gum line. The rate of a permanent tooth’s eruption is adjusted to match the rate of the wear upon the grinding surface of the tooth. The equine starts to shed its deciduous/milk cheek teeth (premolars only) from the age of two and a half years (first cheek teeth) second cheek teeth at three years of age, and third cheek teeth at around three and a half years of age. The incisor milk teeth start to shed at two and a half years. Centrals (front two, upper and lower). Intermediates shed at three and a half and inner incisors at four and a half years. The lower canines start to erupt at around four years, and the upper incisors at around four and a half.
It is during this process that these milk teeth (also known as Caps) which would normally shed themselves can become retained or trapped between the crowns of adjacent teeth. This can lead to oral pain and delay the eruption of the permanent tooth and can cause bumps or swellings called dental cysts, usually on the mandible.
These cysts will normally regress as the jaw elongates and teeth erupt. A retained cap can cause molars and incisors to become displaced and cause teeth to rotate. Another quite common problem with eruption is with the fifth lower cheek teeth in a horse with a small head or excessive curvature of spee of the mandible where it becomes trapped or impacted between the fourth and sixth cheek tooth. Because the opposing tooth has no opposing molar able to wear against it becomes protuberant or “HIGH”. Taking this one step further imagine an equine that for some reason had a missing molar or incisor, the opposite tooth would hyper erupt into this open space. These protuberant teeth need to be regularly maintained to keep them in balance with the rest of the dentition.
Problems Related to Performance.
When we ask our horses to perform for us, be it a quiet hack, jumping, driving, dressage or any competition work at the highest level, our aims should be the same. A horse that is happy, willing, confident and going forward into the hand.
Today you can purchase and use a myriad of different bits, their size, shape, action, use of different metals, rubber bits, etc. schooling aids such as draw reins, side reins, auxiliary reins with pulley systems. What ever sort of bit we use it creates pressure on the horse’s sensitive mouth to allow us to control direction, position of the head and speed.
Where the problem arises for the horse is when pressure is applied to the cheeks, tongue, gums and sensitive tissue lying over the bars of the mouth.
The pressure on these sensitive parts of the mouth can create pain which in some cases will make the horse do the opposite to what is being asked.
Eventually the horse will learn how to avoid contact with the riders hand, or lean on the hand, be stiff in its jaw, this can make the horse stiff at the poll, the neck and back.
For a horse to be free in its jaw it has to have full lateral excursion of the incisors, correct incisor table height and angles, correct molar table angles, no protuberant molars, no dorsal, ventral hooks, no accentivated transverse ridging, float Buccal and lingual margins, no wolf teeth, and install bit seats.
Rasping/Floating of Teeth.
It never ceases to amaze me how most equines tolerate having their teeth examined and rasped without much fuss. Equines that do get a bit fractious can be sedated by the owners veterinary surgeon, making the procedure less stressful for all concerned, and means you can work in relative safety. The design of dental instruments has not changed much in 150 years.
The materials have, Stainless steel means that instruments do not rust, they are more hygienic and can be sterilised. Rasp blades of today are made from tungsten carbide, second in hardness to diamonds.
These blades can be very expensive but because they are so sharp can do an excellent job in the right hands. In equine dentistry today, electrically powered rasps, burrs, diamond cut-off wheels are also used to great effect.
The frequency of rasping depends upon any individual equines situation. It might be every six months or annually or less than six months, it all depends on the situation.
The Importance of Good Equine Dentistry.
Today there is no need for any equine to suffer in silence because of bad dentition or lack of knowledge.
The past twenty years or so has brought back a resurgence of old skills and techniques lost in the 1920’s due to the car and the tractor taking over the role of the equine.
The old skills and techniques added with today’s knowledge, study, better instrumentation, structured training and teaching programs means that good dentistry should be available to all equines.
I train over in America at Dale Jeferys Academy of equine dentistry along with fellow students from all over the world.
These students include human dentists wanting to cross over to into equine dentistry, veterinary surgeons wanting to enhance their knowledge and skills, and lay people like myself, probably from an equine background wanting a new career making the equines like a better one.
Students are taught about very exciting aspects of equine dentistry such as:
* Head and neck anatomy.
* Anterior-Posterior movement of the mandible.
* Accentuated Transverse Ridging.
* Axial Flow of food through the molar tables.
* The importance of lateral excursion.
* (S.C.O.) Simultaneous centric Occlusion/Three Point Balance.
* Mastication Patterns.
* Air Flow.
* Mandible and Maxilla cheek tooth rehabilitation.
* Incisor Alignment and Adjustment.
And Much Much More.
By Tom Phillips 01778 426150