The average human grows 20 baby teeth, which eventually fall out and are replaced with 32 permanent teeth. Permanent (adult) teeth include: eight incisors, four canines, eight premolars and 12 molars (including four wisdom teeth). Because many adults have had their wisdom teeth removed, it is common for many people to have only 28 teeth. Usually all adult teeth have formed and erupted into the mouth by the time a person is 21 years old (except for the wisdom teeth, which sometimes don’t have space to erupt). However, some people don’t develop all of their permanent teeth. Often, these people are born with a fairly common condition called hypodontia, where some teeth fail to develop.
Hypodontia is a developmental abnormality in which six or fewer permanent teeth fail to develop. Studies suggest that hypodontia is usually an inherited trait, but environmental factors during tooth development may also play a role. Having more than six permanent teeth missing is known as oligodontia, and a total absence of adult teeth is referred to as anodontia. Researchers estimate that as many as 20 percent of adults are born with at least one missing tooth, making hypodontia one of the most common developmental oral health conditions. Most individuals are missing only one or two permanent teeth, with very few missing more than six.
Missing wisdom teeth are the most common, followed by premolars (located between the canines and molars), upper lateral incisors (located on either side of the central incisors, or “front teeth”), and lower central incisors (front bottom teeth).
Many studies have demonstrated a strong genetic influence in hypodontia. Researchers believe that hypodontia results from complex interactions between genetic and environmental factors, though they still debate why those changes occur.
Besides genetic causes, experts suggest that advanced maternal age, low birth weight, maternal smoking, incidences of rubella, and other hormonal, environmental and infectious conditions may also be linked to missing teeth. Hypodontia is more prevalent in women than in men and appears at a higher than average rate in identical twins.
Your child’s dentist can monitor his or her oral development and check for missing permanent teeth. Generally, you should take your child to the dentist soon after the first baby tooth erupts, and no later than the child’s first birthday. If you notice that your child has lost a baby tooth and no permanent tooth has taken its place, do not panic. Many cases of missing teeth in children are actually due to delayed eruption.
Less than 1 percent of children are born with a congenitally missing baby tooth. Where baby teeth are missing, the adult teeth below will also be missing 30-50 percent of the time. Children with missing teeth may also have problems with the eruption of the teeth near the location of the missing tooth, and issues with the size or shape of other teeth. Regular visits to your child’s dentist will help to check for missing permanent teeth, monitor growth and development progress, and provide advice for appropriate timing and treatment options for managing missing or poorly erupting teeth.
Fortunately, there are effective ways to treat missing teeth, including implants, dental prosthetics and orthodontic braces and appliances. Fixed porcelain ceramic bridges or removable partial dentures can fill in the spaces left by missing teeth, in order to create an attractive dental appearance. Braces can often be used to realign the teeth to close the gap, though this may require reshaping of adjacent teeth.
When the gap between teeth is small, the dentist can sometimes close the space by bonding tooth colored fillings to the teeth on either side of the space. Dental implants are another option for adults with healthy gums and jawbones. Implants are placed below the gums in your jawbone. Unlike dentures, implants fuse to the bone and act as a base for replacement teeth.
Since their jaws are still growing, children are not good candidates for dental implants. Dentists might recommend preserving the existing primary tooth for a child with permanent tooth hypodontia. With no underlying adult tooth to push the baby tooth out of its place, a primary tooth can sometimes remain in the mouth for a lifetime, when cared for.
If preserving the baby tooth is impossible, the dentist may be able to close the space with braces. In this case, braces draw an existing tooth into the space, which may be reshaped to resemble the absent tooth. If orthodontics is not possible, the dentist has other options to maintain the space until the child is old enough for a bridge or implants. The timing of treatment can be important when planning for and managing missing permanent teeth in children. It is important for your child to see a dentist regularly, and for the dentists to keep you informed about treatment timing and options.
Meta-Analysis of Observational Studies on the Most Commonly Missing Permanent Dentition (Excluding the Third Molars) in Non-Syndromic Dental Patients or Randomly-Selected Subjects, and the Factors Affecting the Observed Rates. Rakhshan V. J Clin Pediatr Dent. 2015 Spring;39(3):199-207.
Hypodontia: An Update on Its Etiology, Classification, and Clinical Management. Al-Ani AH, Antoun JS, Thomson WM, Merriman TR, Farella M. Biomed Res Int. 2017;2017:9378325.
Tooth agenesis: from molecular genetics to molecular dentistry. Matalova E, Fleischmannova J, Sharpe PT, Tucker AS. J Dent Res. 2008 Jul;87(7):617-23.
Maternal smoking during pregnancy is associated with offspring hypodontia. Al-Ani AH, Antoun JS, Thomson WM. J Dent Res.2017 96 (9): 1014–1019.
Prevalence of hypodontia and associated factors: a systematic review and meta-analysis. Khalaf K, Miskelly J, Voge E, Macfarlane TV. J Orthod. 2014 Dec;41(4):299-316.