1) How to lift the upper lip in a horse that doesn’t want it lifted – Many horses don’t like their upper lip fiddled with. This could come from sensitivity, a past experience with a lip twitch or both. What I do is start with gently placing your thumb on the outside of the LOWER lip and pull that down to expose the lower incisors. If you are successful, reward the horse with abundant praise (Cheer leading v Coaching) or a peanut. If you must use a sugary treat do so ONLY if the horse has earned it. When the horse is allowing you access to the lower lip, KEEP IT PULLED DOWN with your thumb while you use the index finger of the same hand to fiddle with the upper lip.
Where most people go wrong is that they only have in their mind that they want to look at or photograph or clean (etc) something under the lip. Don’t use these as reasons to lift the lip. Focus, instead, on earning the trust of the horse. Reward when earned and NEVER REWARD BAD BEHAVIOR. An example of this would be, during your attempt of raising the upper lip, the horse rejects your request and you either say “Stand still! I’m not going to hurt you.” or you say nothing but double down on your energy and strength. The result of this is more rejection.
This is not a race. Baby steps. The goal is trust. The area you want to clean will never be cleaned if you can’t earn the trust of the horse.
2) The “bone structure” is probably the tip of the tooth root as the tooth is being ejected by the diseased underlying bone.This area is dead and has no pain from it. You can’t damage it more. If there is pain, it will come from inflamed gum tissue caused by a) fermenting debris and / or b) continued inflammation from feeding grain and grain byproducts. These can be reduced by daily gentle cleaning and removing all grain / byproducts and adding Equident.
3) The best way to clean this area is through a “touches” application of body temperature water under gentle pressure (lavage) directed by you with the use of a 60ml (2 oz) dose syringe. Once cleaned, the last lavage should be with Peroxyl (Colgate) found in any pharmacy, grocery or Amazon. This is flavored hydrogen peroxide used in human oral care that will add oxygen to kill the stink causing bacteria without stinging the gum tissue.