Chapter 11A: Underbite and Class III Growth Patterns

While an overjet (Chapter 10) describes the upper front teeth protruding ahead of the lower ones, some children show the reverse pattern — the lower jaw growing ahead of the upper jaw, causing the lower front teeth to sit ahead of the upper front teeth. This is often called a Class III relationship or, informally, an underbite.

Why This Pattern Gets Special Attention

Class III growth patterns are often more strongly genetic than other bite discrepancies and can continue to worsen throughout a child's entire growth period, including the adolescent growth spurt, rather than settling on their own. This is one of the clearest cases where early orthodontic evaluation and monitoring is particularly valuable, since a mild Class III tendency identified early can sometimes be managed with growth-modification appliances, while a severe pattern identified only in the late teenage years, after jaw growth has mostly finished, may require a combination of orthodontics and jaw surgery in adulthood.

Interceptive Approaches

What Parents Should Know

Because Class III patterns can continue evolving throughout growth, ongoing monitoring through the teenage years is especially important even after successful interceptive treatment, so that the treatment team can catch and address any continued unfavorable growth as early as possible.