05/11/2025
A diastema is a gap between teeth. This can happen because the teeth are mis-aligned, a tooth is missing part of the crown, or most commonly, it can happen as part of age-related drift.
By the time horses are about 5 years old, they have all the tooth they will ever have. However, at that young age, the majority of their teeth are hiding under the gumline as reserve crown. As those teeth wear at the chewing surface, more reserve crown erupts from the gum to keep the chewing surface level. When horses make their teeth, the reserve crown closer to the roots is slightly narrower than the reserve crown that is in the mouth. As that narrower reserve crown erupts into the mouth as horses age, the angle of the teeth is supposed to push those teeth together and prevent gaps. But sometimes the system fails, either because the teeth are not angled properly, the gaps are too big for the angles to overcome, or some sort of trauma, misalignment, or overgrown opposing tooth prevents those gaps from closing.
The horse in this picture has a very deep, wide diastema (yellow arrows.) In the first picture, you can see in the mirror and looking straight in the mouth that the diastema is packed with feed. The feed was relatively fresh close to the chewing surface, but as we flushed it out, the feed deeper down was rotting and stinky since it had been stuck in the gap for much longer.
Rotting feed stuck in diastemata will erode the gingiva and rot the teeth, leading to tooth extractions if not caught early. Sometimes these lead to exactions anyway. In this case, we could actually see the tooth roots in the diastema. When things are less advanced, diastemata can be treated by burring them out, packing them, or proper floating to allow them to close.
In the second photo, you can see the diastema (yellow arrows) clearly in the mirror but it is difficult to see when just looking in the mouth. This is why we always use the dental mirror for a thorough oral exam. Sometimes, without it, we can miss stuff.
This horse ended up having the tooth in front and behind this diastema extracted because the roots were exposed and for several other reasons that were particular to him. We hope he will continue to be a good eater and provide his mom with much less stress than he has recently. π