Headgear is often used to correct an excessive overbite. This is done by placing pressure against the upper teeth and jaw, which holds the teeth in position or help them move into better positions. The severity of the problem determines the length of time it needs to be worn.
The key to success with this appliance is consistency. Headgear must be worn a certain number of hours per day, and if not, it must be made up the following day. If it isn’t worn enough, the case won’t be as successful as envisioned.
They should never be worn while playing sports and should also be removed while eating or brushing your teeth. (And it probably shouldn’t be worn when you have your school pictures taken!)