According to Dr. Thomas Field, a highly successful orthodontist with more than 30 years of experience, an overbite is the amount of imbalance in a horizontal or vertical plane between the upper and lower teeth or upper and lower jaw. In other words, an overbite is when the front teeth cover the lower teeth markedly.
While most parents talk about the overbite as the amount of protusion of the upper teeth and/or jaw or retrusion of the lower teeth and/or jaw, an overbite really refers to the amount, in percentage, the upper teeth cover over the lower teeth. With a 100% overbite, the upper teeth would cover 100% of the lower teeth. An overbite can also be impinging, which means the lower teeth are pushing in to the tissue behind the upper teeth.
Basically, an overbite is a common orthodontic problem and is often easy to treat.