What are wolf teeth, and why don't all the horses have them?

Also, why do they have to come out now rather than earlier or later? The majority of yearlings that are being broken will have wolf teeth, probably about 75-80%. Wolf teeth are the first upper pre-molars, and they are vestigial, which means they are not as fully formed as the other pre-molars and don't really have a function in the horse today like they probably did thousands of years ago. They are located at the back of the interdental space-the space between the incisors and the molars. Usually they are located just in front of the upper (maxillary) second pre-molar, which is the first tooth that actually looks like a molar. I've never seen a wolf tooth on the lower jaw (mandible), but there are reports in the literature of them being there. The bottom arcade is where the bit lies in most performance horses, but in racehorses the bit tends to be up in that interdental space and hits those wolf teeth in the upper arcade and can cause the horse problems. Tradition has dictated that ...  more