Uprighting Mesially Impacted Lower Third Molars with Skeletal Anchorage.

T impaction of lower third molars is a common clinical finding, with a prevalence between 9.5% and 39% among different populations.1 Previous studies have indicated that normal eruption of lower third molars may be facilitated by extraction of the premolars before orthodontic treatment.2 Nonextraction therapy has been associated with more “abnormal” eruption of lower third molars compared to extraction treatment.3 Therefore, the presence of third-molar germs is sometimes considered when making decisions about premolar extractions. Even if it is not impacted, a third molar will often erupt in a mesial direction against the adjacent second molar. Partially erupted third molars are evident in the post-treatment records of 51% of orthodontic patients and in 35% of untreated individuals.4 Compared to unerupted third molars, mesially erupted third molars have an increased risk of pericoronitis, as well as a higher incidence of caries on the adjacent second molars.5,6 For these reasons, clinicians often decide to extract third molars before, during, or at the end of orthodontic treatment. Although the morbidity of third-molar extractions is fairly low, there is a risk of injury to the inferior alveolar nerve7 and of complications such as dry socket during healing of the extraction site.8 In addition, third-molar extraction is a risk factor for TMD.9 Complications are more likely to occur in cases of mesioangular7 and horizontal impactions.10 Mesioangular impaction is the most common type, occurring in 43% of the cases involving lowermolar impactions.10 Although uprighting of mesially tipped or impacted third molars would be an alternative to extraction, it is usually not feasible before debonding due to the late development of third molars. Skeletal anchorage offers the potential to upright molars separately with localized mechanics. Lee and colleagues used miniscrew-anchored sectional mechanics to upright lower second molars,11 but that method requires free access to the third molar’s buccal crown—which is impossible if only the distal cusps have fully erupted. In such a case, treatment mechanics must be modified, as described in this article, to avoid the need for surgical exposure of the buccal tooth surface.