Bars are the empty space between a horse’s incisors and molars. The soft gum tissue in this area is sensitive. The bit is placed so that it rests in this part of the mouth. Pressure exerted by the bit pressing on the bars causes discomfort and is used to slow a horse’s pace, change his direction, or change his head or body carriage.
At maturity, horses have six upper and six lower incisors (front) and a total of 12 permanent molars behind the bars. Incisors cut grass and molars chew it prior to swallowing. Behind the incisors sit the canine teeth – often more pronounced in males. They can grow quite long and look very formidable. Mares frequently don’t have any canines at all.
Right in front of the premolars you may find the wolf teeth: tiny tusks that may or may not erupt through the gum line (not visible in the skull photos), which can cause discomfort when the horse is wearing a bit. Non-erupted wolf teeth often cause more problems than erupted ones. Generally young male horses have wolf teeth. However, few female horses (about 25%) have them, and those that do have only 1 or 2 that are sometimes not erupted through the gum and are usually on the upper jaw.
Wolf teeth are not canines as the name suggests, but vestigial (evolutionarily left-over – no longer useful) premolars. This skull shows canine teeth just behind the incisors, but no wolf teeth in front of the premolars.
Horses, like humans, get two sets of teeth: baby teeth and permanent teeth. If they are not lost naturally, the baby teeth (and wolf teeth) are often pulled depending on whether they are likely to interfere with the horse’s use of a bit.
All permanent teeth are generally in by about 5-6 years old. Wolf teeth appear between about 6 months and 3 years of age. Canines between 3-1/2 yrs to 6 years of age. Young horses sometimes appear to have a lumpy lower jaw, as the roots of their teeth are long and well-embedded below the gum line giving an irregular look to the jaw line. The teeth continue to grow at a rate of about 1/8 inch per year as the surface is worn off due to grinding and new tooth grows up to keep the tooth the proper length. However, this replacement from the root stops as the horse enters old age. First the lumpy lower jaw becomes smooth. In old age the teeth begin to actually fall out and the jaw may appear to be a little concave as its tooth roots give no form to it.
Stallions frequently keep their wolf teeth. This little Caspian stallion is 9 years old and still has all 4 of his canine teeth, but you can’t see any wolf teeth if he has them. (He is yawning, not threatening.)
Interestingly, horse teeth have no pulp or nerves near the surface of the tooth, so keeping a horse’s mouth in good shape is a generally painless procedure that involves filing the sharp points off of the molars that can grow into spikes that bore into the jaw or make wearing the bit painful when the sharp tooth is pressed against the cheek.
We have been watching a tiny Caspian foal as we imprint train her. It is interesting that she was born toothless but started pushing incisors through the gums in only 2-3 days. A curious nibble could actually be painful by 4 days old.
Here are some pictures of a horse with a “wry” mouth. The jaw is slightly offset to the right and the incisors have grown to match the offset so that he has no trouble eating or drinking. Since it does not interfere with his health, it is not considered severe. With good dental care over a couple of years to file and even the bite, this horse will probably do quite well. However, without it, his mouth may become worse over time. A bit? If his mouth seems to present problems wearing a bit, he should be ridden in a bitless manner.
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