Does this ever need to happen with horses? I can say I have never seen a horse with a tooth missing, but figured I might as well ask.

I don;t think so. Horse teeth are constantely growing. Any cavity or chip would quickly wear off as the tooth wears off. A break would be the same. The only one I don't know about its if a tooth splits.

Yes, horses occasionally have to have teeth removed. Unfortunately some horses have had such little dental care that problems may develop through eating none fibrous foods like alfalfa. Hooks form, the horse can't chew right, the hooks can stab into the cheeks and opposing gums. Infection can set in, abscesses, periodontal disease that leads to sinus problems, cracked and broken teeth.

So yes they can have problems and yes those problems can lead to extractions.

I had also wondered if they have sinus isses. I am dealing with some myself right now so that is what sparked the talk of it. Thanks for the answers, now I have one less question about the animals I have come to love. :)