Mesial force from unerupted third molars

Thomas E. Southard, Karin A. Southard, Lawrence Weeda

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Erupting mandibular third molars are implicated as a cause of anterior crowding of mandibular teeth. The goal of this two-part investigation was to measure the mesial force exerted by unerupted mandibular third molars. We hypothesized that such a force increases the tightness of all proximal posterior tooth contacts mesial to the mandibular second molar, and that surgical removal of third molars relieves the tightness by eliminating this force. The contact tightness between mandibular posterior teeth was measured bilaterally in 20 patients with bilateral unerupted mandibular third molars, immediately before and after unilateral removal of a third molar. We found unexpectedly that mean proximal tightness decreased bilaterally in all contacts that were measured after unilateral removal of a third molar, and we did not detect a mesial force exerted by unerupted third molars. We suspected that this bilateral relief of contact tightness resulted from placing the patients in a supine position for surgery. The second part of the experiment was conducted to determine the effects of postural change on proximal contact tightness where no surgery had been performed. For ten subjects we discovered a mean decrease in the tightness of all mandibular posterior contacts 2 hours after the patient had been moved from an upright to a supine position. The greatest mean decrease (-32%, p < 0.0001) was found at the most posterior tooth contact. We conclude that surgical removal of unerupted mandibular third molars does not significantly reduce proximal contact tightness, but that simple movement from an upright to a supine position relieves such tightness dramatically. The effects of posture overwhelm any effects from erupting third molars on interdental forces. There are many valid reasons for removing unerupted mandibular third molars. However, the results of this study indicate that removing these teeth for the exclusive purpose of relieving interdental pressure and thereby preventing mandibular incisor crowding appears to be unwarranted.

Original languageEnglish (US)
Pages (from-to)220-225
Number of pages6
JournalAmerican Journal of Orthodontics and Dentofacial Orthopedics
Volume99
Issue number3
DOIs
StatePublished - Jan 1 1991

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Third Molar
Supine Position
Tooth
Malocclusion
Incisor
Posture
Pressure

All Science Journal Classification (ASJC) codes

  • Orthodontics

Cite this

Mesial force from unerupted third molars. / Southard, Thomas E.; Southard, Karin A.; Weeda, Lawrence.

In: American Journal of Orthodontics and Dentofacial Orthopedics, Vol. 99, No. 3, 01.01.1991, p. 220-225.

Research output: Contribution to journalArticle

Southard, Thomas E. ; Southard, Karin A. ; Weeda, Lawrence. / Mesial force from unerupted third molars. In: American Journal of Orthodontics and Dentofacial Orthopedics. 1991 ; Vol. 99, No. 3. pp. 220-225.
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