Abstract
The influence of the third molars on mandibular incisor crowding has been extensively studied but remains controversial. The purpose of this study was to ascertain whether, in Mongolian subjects, the lower third molar can affect anterior crowding and/or the inclination of teeth in the lower lateral segments. Panoramic radiographs, 45° oblique cephalograms, and dental casts were taken from Mongolian subjects (age range 18.3–24.1 years, mean 21.0 years) exhibiting impaction of all four third molars and an Angle Class I molar relationship. The Ganss ratio was calculated using panoramic radiographs, whereas the gonial angle and angulation of lower canines, premolars and molars were measured using 45° oblique cephalograms. Little’s index of irregularity was calculated using dental casts. Significant relationships between the angulation of the third and second molars and between the first molars and second premolars were found. Conversely, there was no significant correlation between the angulation of third molars, first premolars and canines. The Ganss ratio calculations showed that the lower first and second molars and the second premolars inclined mesially if there was insufficient space for the lower third molars. However, there was no significant correlation between Little’s index of irregularity and third molar angulation. Furthermore, although the third molar influences the lateral segments, no obvious relationship between the third molar and anterior crowding was observed. Therefore, the angulation of the third molar appears not to cause anterior crowding.
Similar content being viewed by others
References
Chimge N, Batsuuri J. Interethnic genetic differentiation, HLA Class I antigens in the population of Mongolia. Am J Hum Biol. 1999;11:603–18.
Scott RG, Turner CG II. The anthropology of modern human teeth. Cambridge, England, Cambridge university press; 1997. p. 270–1.
Hasegawa Y, Terada K, Kageyama I, Kuroki H, Sano N, Tsuchimochi W, Nakahara S. Influence of shovel-shaped incisors on the dental arch crowding in Mongolian females. Okajimas Folia Anat Jpn. 2009;86:67–72.
Vego L. A longitudinal study of mandibular arch perimeter. Angle Orthod. 1962;32:187–92.
Richardson ME. The role of the third molar in the cause of late lower arch crowding: a review. Am J Orthod Dentofacial Orthop. 1989;95:79–83.
Bishara SE. Third molars: a dilemma! Or is it? Am J Orthod Dentofacial Orthop. 1999;115:628–33.
Lindauer SJ, Laskin DM, Tüfekçi E, Taylor RS, Cushing BJ. Orthodontists’ and surgeons’ opinions on the role of third molars as a cause of dental crowding. Am J Orthod Dentofacial Orthop. 2007;132:43–8.
Ganss C, Hochban W, Kielbassa AM, Umstadt HE. Prognosis of third molar eruption. Oral Surg Oral Med Oral Pathol. 1993;76:688–93.
Kamegai T. Studies on the position of canines, premolars and molars by forty-five degrees oblique cephalometric roentgenography. Jpn J Orthod. 1973;32:23–46.
Little RM. The Irregularity index: a quantitative score of mandibular anterior alignment. Am J Orthod. 1975;68:554–63.
Dahlberg G. Statistical methods for medical and biological students. London: George Allen and Unwin Ltd; 1940.
Dudhia R, Monsour PA, Savage NW, Wilson RJ. Accuracy of angular measurements and assessment of distortion in the mandibular third molar region on panoramic radiographs. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2011;111:508–16.
Dahlberg AA. The changing dentition of the man. J Amer Dent Assoc. 1945;32:676–90.
Sofaer JA, Bailit HL, MacLean CJ. A developmental basis for differential tooth reduction during hominid evolution. Evolution. 1971;25:509–17.
Perera PSG. Rotational growth and incisor compensation. Angle Orthod. 1987;57:39–49.
Elsey MJ, Rock WP. Influence of orthodontic treatment on development of third molars. Br J Oral Maxillofacial Surg. 2000;38:350–3.
Saysel MY, Meral GD, Kocadereli I, Taşar F. The effect of first premolar extractions on third molar angulations. Angle Orthod. 2005;75:719–22.
Haavikko K, Altonen M, Mattila K. Predicting angulational development and eruption of the lower third molar. Angle Orthod. 1978;48:39–48.
Kaplan RG. Mandibular third molars and post-retention crowding. Am J Orthod. 1974;66:411–30.
Zachrisson BU. 20. Zachrisson BU. Mandibular third molars and late lower arch crowding—the evidence base. World J Orthod. 2005;6:180–6.
Niedzielska I. Third molar influence on dental arch crowding. Eur J Orthod. 2005;27:518–23 (Epub 2005 Aug 2).
Acknowledgments
The support of the research staff at both the Health Science University of Mongolia and the Nippon Dental University School of Life Dentistry Tokyo and Niigata are gratefully acknowledged.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hasegawa, Y., Terada, K., Kageyama, I. et al. Influence of third molar space on angulation and dental arch crowding. Odontology 101, 22–28 (2013). https://doi.org/10.1007/s10266-012-0065-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10266-012-0065-2