The horse's normal chewing cycle results in balanced dental wear which, in the absence of dental abnormalities, serves the horse well. The process of domestication and the advent of processed feedstuffs have significantly altered the duration and biomechanics of mastication. These factors have contributed to the appearance of dental diseases of the soft tissues of the mouth.
The problem with dental disease is that once it becomes severe, it is often irreversible, and so the horse never regains its ability to chew properly. A horse in the paddock will eat grass for between 10 to 18 hours a day. Unlike ruminants a horse will only chew its food once and thus it is important that they crush and shred it into small enough pieces to aid in digestion.
The adult horse has 12 incisors that are used to bite off grass and hay, and 24 cheek teeth which are packed tightly together to act as a single chewing unit. The horse's lower dental arcade is straighter and narrower than the upper arcade. Also the upper cheek teeth are larger with a greater surface area. The chewing cycle of the horse involves the mandible (lower jaw) moving in an oval shaped and side to side pattern across the maxilla (upper jaw), as a result, sharp enamel points appear on the outside of the upper cheek teeth and the inside of the lower cheek teeth. Management of these sharp points remains an important aspect of a healthy horse's mouth but these days equine dentistry has developed significantly and extends to a wide range of procedures and techniques.
Dental pathology can upset the normal chewing pattern and result in the horse moving its jaw in and abnormal manner. One of the problems with the change in chewing pattern is that it reduces the mouth's ability to "self clean". Instead of the food particles moving in a smooth auger-like path through the mouth cavity, they can become trapped in various parts of the mouth. Food stuck in small places for long period leads to fermentation and the production of acids. These acids result in gingivitis (inflammation of the gums) . which, if not arrested and corrected, will progress to the more severe condition of periodontal disease. which is painful and often irreversible. Periodontal disease has the short term effect of being uncomfortable to the horse, but in the long term it will lead to premature loss of teeth, and thus a shortening of the life of the horse.
Periodontal disease can be found in approximately 60% of horses over the age of 15 years. In humans, women with periodontal disease are 7 times more likely to either abort their pregnancy, or to have a low birth weight child. This relationship has not been proven in the horse, however if it does occur then this alone supports regular dental care of the broodmare. It is also important to consider the effectiveness of chewing in food conversion and the cost of poorly digested or wasted food.
Therefore if you are simply doing routine dental rasping ("floating") on your broodmares without a thorough dental examination you may only be dealing with a small piece of the puzzle and not correcting some pathology that may have very significant consequences.