Do Wisdom Teeth Really Cause Crowding?

“It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so.” -Mark Twain

Despite popular belief amongst patients and dentists, wisdom teeth do not contribute to lower incisor crowding in adulthood. Blasphemy!, Copernicus!, Leviticus 24:15!, you say? Amazingly, the belief that wisdom teeth contribute to lower incisor crowding is based on an antecdotal statement from a single research paper more than 50 years-old.

In 1961, orthodontist Leroy Vego, published an article, "A Longitudinal Study of Mandibular Arch Perimeter" which examined the role of wisdom teeth on lower incisor crowding. Vego evaluated plaster stone models of 65 individuals who have never had orthodontic treatment; 40 individuals with lower wisdom teeth present and 25 patients with lower wisdom teeth congenitally absent (never born with wisdom teeth), over six years from ages 13 to 19. He reported that there was a significantly greater degree of crowding in [those individuals] with wisdom teeth. Vego concluded: "that the erupting lower third molar can exert a force on approximating teeth."

From this statement, the theory formulated that lower wisdom teeth "push" the teeth in front of them as they come into the mouth, contributing to incisor crowding. As such, general dentists, orthodontists, and oral surgeons recommended the prophylactic extraction of wisdom teeth to prevent against the relapse of crowding after orthodontic treatment.

Ample research exists (References 1-8) which disprove Vego's theory that wisdom teeth exert enough pressure on teeth to move them forward. In fact, numerous elements play a role in crowding, irrespective of whether the individual has wisdom teeth. Most notably, lower incisors tend to drift forward through the bone in the direction of our main chewing muscles (masseter and temporalis). Additionally, bone is continually remodeling and bone in the lower anterior region happens to resorb throughout life. Other factors such as tooth-size, tooth-shape, and original tooth-position also play a significant role. Therefore, little rationale exists for the extraction of third molars solely to minimize present or future crowding.

Nonetheless, timely removal of wisdom teeth is still encouraged. Wisdom teeth may develop cavities, gum inflammation (pericoronitis), root resorption of the second-molar, cysts or tumors, impede orthodontic tooth movement, or interfere with proper occlusion, and therefore should be extracted in many patients. In our office, we encourage the extraction of wisdom teeth during late adolescence, prior to the child leaving for college. As the patient reaches greater skeletal maturity, jaw bones become increasingly more dense, which may result in higher post-operative pain following wisdom tooth removal. Typically, after the age of 25, asymptomatic wisdom teeth are not extracted and simply monitored with routine periodic x-rays.

I hope this has provided some helpful information on wisdom teeth. Please feel free to respond with any questions or comments or requests for additional information.

Respectfully,
Dr. Kravitz
South Riding, Virginia
www.kravitzorthodontics.com


References:
1. Fastlicht (1970) found that in orthodontically treated subjects, only 11% had wisdom teeth present but 86% still had a relapse of lower anterior crowing after treatment.
2. Kaplan (1974) concluded that the presence of third molars does not produce a greater degree anterior crowding after the cessation of retention.
3. Little (1981) observed that 90% of patients treated orthodontically with extractions relapsed with lower anterior crowding.
4. Lifshitz (1982) evaluated lower anterior crowding in patients with lower premolar extraction in the presence or absence of lower third molars, and concluded that a relapse of crowding occurs after treatment regardless of whether lower premolars were extracted or third molars were present.
5. Linqvist and Thilander (1982) reported that patients with prophylactic removal of wisdom teeth had similar relapse of lower anterior alignment than those with wisdom teeth present.
6. Ades et al. (1990) reported no difference in mandibular growth pattern whether wisdom teeth were erupted, impacted, or missing, and concluded that there is no basis for recommending third molar extractions to alleviate or prevent mandibular incisor crowding.
7. Southard et al. (1991) found that the surgical removal of third molars did not have an effect on contact tightness.
8. Pirttiniemi et al. (1994) evaluated the effect of removal of impacted wisdom teeth on subjects in their third decade of life (30-39 years of age) and found that wisdom tooth extraction had no significant change in the lower anterior area.