You can see from the picture o f the skull that the upper rows of cheek teeth are wider than the lower rows of cheek teeth. The horse eats on one side of its mouth at a time,in the following motion:
1. The lower jaw drops and moves out to the side.
2. The lower jaw is closed, crushing the food, so that the outside edge of the upper row of cheek teeth and the outside edge of the lower row of cheek teeth is in line.
3. The jaw is then moved back to the starting position, and the food is ground between the teeth.
The sahrp edges are caused when the lower jaw is not moved far enough to the side and the outsied edge of the upper chhek teeth and inside edge of the lowr cheek teeth receives insufficient wear and becomes protuberant. When the horse is fed hard food, it has been proven that this sideways movement is reduced and so the sharp edges develop more quickly. This is the most common dental problem and will develop in ost horses if they do not receive dental attention which can cause ulcers on the cheeks and the tongue. In extreme cases, the horse may drop food (quid) or lose condition, but generally, as they have to eat or be hungry, they will suffer in silence.
Hooks and Ramps
Hooks develop due to a mis-alignment of the upper and lower cheek teeth row, resulting in the front or back tooth in a row, receiving insufficient wear due to having nothing to war against. This commonly happens when a horse is overshot (parrot mouth), and the upper row of cheek teeth will be further forwards than the lower row of cheek teeth. This means that the upper front cheek tooth and the lower rear cheek tooth have no opposition and will overgrow. Hooks can however be located at the front or back of th emouth, on the upper or lower teeth. A ramp is similar to a hook except that it has a more gentle slope. It does however cause teh same problems.
Any overgrowth will affectthe forwrad and back movement of the lower jaw, which is essential when the horse is asked to lower its head, as the lower jaw must be free to slide forwards. If there is a block to this movement the horse will resist the bit of open its mouth to enable the jaw to move. In all to many cases an owner will put on atight noseband to prevent this, causing further resistance as the horses is unable to do what is asked of it. theis forwrad and back movement is alos important when the horse eats as there is a small movement is this direction during the mastication cycle. If this movement is blocked, the horse is forced to eat in an unnatural manner, and this can cause urther problems.
As with the sharp edges, hooks especially will cause trauma to the soft tissues of the mouth and if very large, can even puncture the upper or lower jaw.
Waves
A wave is seen when the whole row of teeth in uneven as you can see in the picture.
The cause of a wave is often due to uncorrected problems when the horse was young. A common cause is due to angle of the number 11 cheek tooth (At back of mouth, on the left of the picture). This causes the 09's and 10's to hav etoo littl eroom to erupt, with the result that they often erupt late. The upper 09's and 10's erupt at the normal time and so they become protuberant as we can see in the picture.
Another cause is due to caps not shedding at the correct times, or as a result of other dental problems such as missing teeth, offset teeth or gaps between teeth and associated food pocketing in these gaps, causing teeth to erupt more slowly than normal.
Steps
This condition is where one tooth is higher than the rest of the teeth and when the inside of teh mouth is examined, the tooth literally steps up. This is usually caused by a missing tooth or as a result of a tooth that has been extracted. The 'step' tooth has no opposition and so will become protuberant. This can also be caused in the young horse, when one cap is retained and the eruption of the adult tooth is delayed.
Shear Mouth
This is when the angle of the occlusal (chewing) surface of the tooth is greater than about 45 degrees. It occurs as a result of other dental problems tht have not been corrected, causing the horse to eat in anincorrect manor.
This condition is often seen in a horse that has a slant to its incisors. In these caes, teh horse will be eating normally on one side of its mouth, but on the other side, will have virtually no sidewyas movement of the lower jaw when eating. This causes the inside edges of teh upper cheek teeth and the outside edge of the lower cheek teeth to be excessively worn, causing the angle of the entire occlusal surface to become shear.
It can aslo occur as a result of sharp edges that are not corrected. Thes edges will tend to become larger and as they do so, will spread across the entire surface of the tooth.
Diastema
A diastema is a gap between adjacent teeth. This is a very common problem and unfortunately one that is also very painful. As the horse eats, food packs into the gap and causes pockets of food below the gum line. As the food breaks down it produces bacteria that cause inflammation of the gums and eventually, the alveolar bone where the root of the teteh are situated to break down.
There will usually be a ridge in the tooth opposite a diastema as this area of the tooth has no opposition and will not be worn down. This ridge will tehn exacerbate the problem as it keeps forcing food down into the diastema. The treatment of this condition is to remove these ridges, and possible to widen the diastema so that food deos not become trapped.
Retained Decidous Teeth (Caps)
The decidous teeth are lost between the ages of about 2 1/2 and 4 1/2 years. The caps should be shed by the adult teeth as they erupt behind them but in some cases these caps become trapped and have to be removed. As we have already seen, the late shedding of caps can cause problems to the teeth which will develop if they are not corrected. Additionally, the horse may also have trouble eating when the caps are shedding as tehy can be quite painful when they are loose and move when the horse is eating.
