Wisdom teeth are third molars. Normally people have three permanent molars that develop in each quadrant of the mouth. The third molars usually will try to grow in at around age 18 to 20 years. Wisdom teeth are actually no different than any other tooth except that they are the last teeth to erupt. They are just as useful as any other tooth if they grow in properly, have a proper bite relationship, and have healthy gum tissue around them. Unfortunately, this does not always happen.When wisdom teeth are prevented from erupting into the mouth properly, they are referred to as impacted. A dentist must examine a patient's mouth and corresponding x-rays to determine if the teeth are impacted or will not grow in properly. Impacted teeth may cause problems. Here are several common problems that occurs when the impacted wisdom teeth are not removed: bacteria and plaque build-up, decay of adjacent teeth, formation of cysts (a fluid- filled sac) or tumors from follicle, tumor development, infection, jaw and gum disease. Erupted wisdom teeth may need to be removed. The dentist may recommend wisdom tooth removal if wisdom tooth: interferes with the bite, non-functional, badly decayed, involved with or at risk for periodontal diseas, interferes with restoration of an adjacent tooth.