Peg lateral teeth, or peg lateral incisors, are terms used to describe a condition where the lateral incisors (the second tooth on either side of the front teeth) are undersized and appear smaller than normal. This situation occurs when the permanent lateral incisors do not fully develop. Sometimes, the permanent adult lateral incisor teeth do not develop at all, leaving only the baby teeth (primary or deciduous teeth) in their place. A true peg lateral incisor is a term reserved for the under-developed adult permanent tooth that erupts after the deciduous tooth has been lost.

There are several ways to treat and correct this condition. If the roots are strong but the visible teeth are undersized, the peg lateral incisors can be covered with porcelain crowns or porcelain veneers. Porcelain veneers are the most common treatment for peg lateral incisors, and require little or no tooth preparation. A porcelain shell is simply bonded over the smaller peg laterals making the teeth appear normal in size.

The second method is to remove the weak tooth and replace it with an all porcelain or porcelain-fused-to-gold bridge. When the bridge is constructed, the tooth on either side of the space where the peg lateral was is prepared for a crown. An impression is taken and sent to a dental laboratory, and a final bridge is returned to the dentist and inserted at a second visit. During the time period while the bridge is being fabricated at the laboratory, a temporary plastic bridge is placed in the mouth to provide function and cosmetic improvement for the missing tooth. When the final bridge is returned, the temporary plastic bridge is removed and replaced with the permanent porcelain bridge.

The third method is to remove the weak tooth and replace it with a dental implant.