Third molars, commonly called "wisdom teeth", usually come in during a person's late teens or early twenties. If there is not enough room in the jaw for these teeth, or the angulation is improper, wisdom teeth may be "impacted" meaning a tooth has failed to emerge fully into its expected position. Why this lack of space exists is not fully understood. However, there does seem to be a correlation between large tooth size and inadequate jawbone space. Impacted teeth are very difficult to clean effectively and commonly have reoccurring infections. This not only places the wisdom tooth at risk, but the tooth next to the wisdom tooth, too. Decay or infection in the wisdom tooth can extend to the adjacent tooth and require its removal along with the wisdom tooth. For these reasons, it is important to diagnose and remove impacted teeth before they become a problem.