Some people do not develop all of their baby teeth or permanent teeth or both. They may be a born with a condition which causes them to have fewer baby/adult teeth. In dentistry, hypodontia is the condition at which the patient has missing teeth as a result of the failure of those teeth to develop (also called tooth agenesis). Hypodontia describes a situation where the patient is missing up to 5 permanent teeth, excluding the 3rd molars. Having more than 6 permanent teeth missing is known as oligodontia.
Extra Tooth or Supernumerary Tooth
While a single excess tooth is relatively common, multiple hyperdontia is rare in people with no other associated diseases or syndromes. Many supernumerary teeth never erupt, but they may delay eruption of nearby teeth or cause other dental or orthodontic problems. Molar-type extra teeth are the rarest form. 
People with extra teeth can encounter several problems. The supernumerary teeth usually displace the adjacent teeth.
Although they are called wisdom teeth, many people do not see any wisdom in them. Often these teeth are troublemakers that decide to turn crooked, refuse to grow in completely, or become misshapen.
Also called third molars, wisdom teeth are the rearmost teeth on each side of your top and bottom jaws. Commonly, they arrive between ages 17 and 21.
Because these teeth arrive last, they may enter a jaw that is already crowded. As a result, the last teeth in usually don't get a seat on your gums. And if they do manage to squeeze in, often little or none of each tooth rises above the gums, becoming what dental professionals call impacted. There are a number of possible risks associated with leaving impacted wisdom teeth, such as infection of the gum and surrounding bone.
Impacted teeth do not always cause problems, but it is important to visit your dentist regularly so that he or she can monitor their arrival. 
Cleaning the Teeth with Braces
Cleaning the teeth with braces can be challenging, but it is very important to do it properly. The video below demonstrates the proper way to do it:
Seeing the pediatric dentist more frequently during the time of wearing braces is highly recommended because of food build-up and plaque around the braces. Daily rinsing with fluoride mouthwash or using prescribed toothpaste can help to prevent decay on teeth.