This video illustrates a relatively unusual dental problem in horses, which is unfortunately becoming more common with the increase in the use of power floating tools by non-professional "horse dentists".
The horse in the video is a 5yo standardbred racehorse, whose teeth have been regularly attended to while in training. His wolf teeth were removed before breaking in as an early 2yo, and caps removed regularly along with sharp points.
Sharp points develop on the cheek teeth (grinding teeth) of horses due to ridges on the outer surface of the upper teeth and the inner surface of the lower ones. As the horse ages, the occlusal surfaces of the cheek teeth are constantly worn away by the grinding action top against bottom during chewing, leaving sharp points of the hard enamel that formed the ridges against the cheeks (top teeth) and the tongue (bottom teeth).
One of the main aims of routne dentistry in horses is to remove these sharp points from the edges of the cheek teeth arcades, eliminating the discomfort and ulceration they cause.
With the horse's mouth "at rest", the top and bottom incisors (or front teeth) sit flush against one another, but the top and bottom cheek teeth actually have a small gap between them. This gap is on a slant, as the top cheek teeth are longer on the outside and bottom ones longer on the inside.
Normal chewing action involves the lower jaw (mandible) moving in a circular motion against the upper - i.e. to one side, then forwards, then to the other side, then backwards to the starting position.
The side-to-side phase of this movement closes the gap between upper and lower cheek teeth on one side and then the other, engaging the occlusal surfaces and grinding the food between them.
Sometimes over-zealous grinding down of sharp points can lead to removal of significant amounts of the normal occlusal surface of the cheek teeth, such that they no longer engage properly during chewing.
Equine dental vets measure this by moving the lower jaw of the sedated horse sideways, and determining the number of incisor teeth widths the top and bottom jaws overlap by before the teeth engage. A normal healthy mouth should only overlap 1.5 incisor-widths - any greater distance than this indicates cheek teeth ground down too far.
The horse in the video has this problem. Sometime in the past, probably on several occasions, his teeth have been ground down by a well-intentioned dentist to ensure no sharp points develop and in the process too much has been taken off the occlusal surfaces, making it difficult for the horse to successfully chew small grains such as oats.
This picture shows the point at which the cheek teeth engage when the lower jaw is moved sideways - more than two incisor-widths - confirming that too much has been removed from the occlusal surface of the cheek teeth.
This horse eats bulkier feeds - such as grass and hay - with no problem at all, and will eventually finish up all his oats. The issue, however, is that he probably does not grind his hard food adequately and won't be able to digest it properly, wasting a significant portion of the nutrients.
With careful veterinary dental attention the problem should eventually resolve, as the cheek teeth are continually pushed into place out of the jaw to wear against one another over the horse's lifetime.
Equine dental vets have the knowledge, experience and skill to care for each horse's mouth without the danger of this and similar problems occurring.
Other consequences of over floating include incorrect occlusion, mouth infections, pulp exposure, and death of teeth necessitating extraction.