A mouth guard is made from a mould of your own teeth. That is the whole difference between one that works and one that does not. The generic boil-and-bite kind from a pharmacy rarely fits well enough to protect anything, and an ill-fitting guard tends to stay in the drawer anyway.
For sport, a guard absorbs the impact that would otherwise fracture a front tooth. For night grinding, it takes the wear instead of your enamel. It does not stop the grinding itself, but it stops the damage, and the damage is the part that costs you teeth.
Grinding is worth mentioning here because most people who do it have no idea. Waking with a sore jaw or a headache that fades by mid-morning is the usual clue, and we often see the flattened edges before the patient has noticed anything at all.
Teeth reshaping is a separate and much simpler thing. Gentle contouring removes a small amount of enamel to smooth a chipped or uneven edge, then polishes it. No anaesthesia for most cases, and you see the result the same visit. It will not fix real misalignment or change tooth colour, and we will tell you plainly when reshaping is not going to be enough.
