If the slow feeder is made with the proper materials it will not hurt or damage the horse’s teeth, however, there are a few materials that are used when making slow feeders that can cause a significant amount of damage to the horse’s teeth.
Slow feeders that have metal grates may create some damage to the horse’s teeth and possibly other areas of the mouth, particularly if the horse has to push against it to access the hay.
Also, the height at which the slow feeder is placed can affect the way your horse’s teeth wear down. The most natural position for a horse to eat in is with the head lowered. Pulling and chewing hay from a raised slow feeder can cause uneven wearing of the teeth.