Mouth Conformation and How to Assess it
Mouth conformation is assessed when the horse is relaxed and with his mouth shut. Gently part the lips at the side and observe if the tongue is bulging through the teeth. If it is, this indicates that the tongue is large and in my experience, a large tongue is anatomically the most common form of mouth discomfort if it is not accommodated with the correct design of mouthpiece. The outer edges of the tongue are far more sensitive than the centre and obviously these parts of the tongue are going to experience increased pressure with certain bits - especially with the traditional straight armed, single jointed bit.
See if you can check out the room between the tongue and the roof of the mouth, you may slip a finger in through the bars and feel how much (if any) clearance there is. This should be done initially without the bit in. This will obviously determine what shape of bit and which port if any, we would use. Then fit your bit, look at it at rest, take up a contact with your reins at the same angle as if you were on board, and see how it shifts position and what pressure points it is using within the mouth. We have lately noticed a higher incidence of Lampus - this is where the roof of the mouth is soft and swollen. Thankfully we now have many bits at our disposal that are designed specifically to accommodate the larger tongue and not interfere with the upper palate. If you are at all concerned regarding any trauma that you find within the mouth it is advisable to contact your Equine Dentist or Veterinary Surgeon.
Teeth do need regular attention - at least once per year - by a fully qualified Equine Dentist or Veterinary Surgeon. It is also advisable to have the back checked by a reputable Equine Physiotherapist and the fit of the saddle assessed (especially if the horse has changed shape) - again at least once per year.
You are probably the only person that has the opportunity to check your horse's mouth on a regular basis for anything unusual including any signs of bruising, cuts, etc. Check underneath the tongue as ulcers and trauma can occur here. Check out the upper and lower palate and bars for any sign of rubbing and do not forget to look inside the cheeks in case the flesh has been pushed into the teeth by the cheek of the bit. This is not an uncommon injury and is often only found by the Dentist.
Another common injury is rubbing - obviously if the corners of the lips are rubbed this is clearly apparent. A major cause of this is due to lack of salivation - if there is not sufficient saliva to act as a lubricant then there will be surface friction. Another common factor is an ill fitting bit - a tight loose ring may nip in this area, also any mouthpiece that is too wide will slide back and forth across the mouth potentially causing rubbing. A further common injury which, again, is only found by the Dentist is caused by the French Link. The French link is a flat central plate as opposed to a rounded lozenge. If the inside rein is not supported when changing direction, the mouthpiece of the French link will slide across and the flat plate will impact on the inside of the gum. This trauma often results in permanent proud flesh.