Underbite Teeth: What an Underbite Is, Causes and Treatment

In a normal bite the upper front teeth sit slightly over the lower ones. In an underbite the relationship is reversed: the lower front teeth bite in front of the upper ones. Dentists describe it as a Class III bite, which is one of the groups in our guide on malocclusion.

People who search for a protruding jaw often mean this. The lower jaw may look prominent, the chin strong, or the upper lip and cheeks flat. Other people feel their upper jaw is underdeveloped instead of the lower one being too large. A dentist decides which.

A dental underbite comes from the position of the teeth: upper teeth tilted back, or lower teeth tilted forward, with jaws of normal size. These are the easier ones to correct with braces.

A skeletal underbite is about the jaws themselves, with a lower jaw that is large, an upper jaw that is small, or both. It is often inherited. Teeth cannot fully compensate for a skeletal difference, so treatment depends on the age of the patient.

Early assessment matters. In a growing child, appliances may be used to guide the upper jaw, and this works best while growth is still going on. Our guide on the best age for braces explains why a first check around age 7 is sensible.

For adults, jaw growth is complete. A mild underbite caused by the position of teeth can be treated with braces alone. A clear skeletal difference may need braces to line the teeth up before and after surgery to move the jaw, planned between a dentist and a surgeon. Some adults choose to leave a mild underbite alone if it causes no trouble.

See braces and orthodontics for what treatment involves, and our guide on what an overbite is for the opposite problem.

Teeth may wear unevenly, chewing can feel awkward, and some people have jaw joint discomfort or difficulty biting with the front teeth. Speech is seldom much affected. A dentist can tell you if yours needs treatment or only monitoring.