Association between third mandibular molar impaction and degree of root development in adolescents

Abstract

Objective: To compare the root development and the growth rate of the mandibular third molar (M3 inf) in individuals where the M3 inf erupted vs individuals exhibiting M3 inf impaction. Materials and Methods: Serial standardized intraoral radiographs (Eggen technique) were taken annually of the mandibular third molar region from 132 subjects (71 male and 61 female) from 15 to 20 years of age. Based on the films, 264 lower third molars were classified into an eruption and an impaction group. Root development was recorded according to a quantitative method described by Haavikko (1970), and the eruption status was analyzed using logistic regression. Results: In total, 155 (59%) of the M3 inf erupted, and 109 (41%) were impacted at age 20. In 44 (33%) patients both M3 inf were impacted, in 21 (16%) patients one tooth was erupted and the contralateral tooth impacted, and in 67 (51%) patients both M3 inf were erupted. The more mature a tooth was at age 15, the higher was the probability of eruption (odds ratio: 3.89, P , .001). The growth rate of the root development stage was statistically significantly associated with the probability of eruption (odds ratio: 10.50, P 5 .041). Conclusions: Delayed mandibular third molar root development is associated with impaction. Radiographs taken at age 15 may predict the risk of impaction and thereby guide decision making for the orthodontist or the oral and maxillofacial surgeon. (Angle Orthod. 2013;83:3-9.)

Association between mandibular third molar formation and retromolar space

“…8 While the effect of premolar extraction (for orthodontic purposes) on eruption of the third molar was investigated in many studies, 16,17 the effect on third molar formation has not been addressed. Our study's main contribution of a high correlation between third molar formation and space availability encompasses the previous conclusions in a more basic biological tenet that may apply to other teeth (eg, canines) and to dental development in general.…”

“…Some observations relate to tooth formation: erupted third molars were at a slightly more advanced stage of development at a younger age 6,8 ; late mineralization and delayed root development were associated with high risk of impaction. 8,9 A great number of publications relate to available space for eruption: impaction or eruption was correlated with the retromolar space, a higher chance of eruption occurring with an increased space 10 ; impaction was more likely to occur with early physical maturation (and corresponding limitation of mandibular growth, and thus a decrease in retromolar space).…”

“…Some observations relate to tooth formation: erupted third molars were at a slightly more advanced stage of development at a younger age 6,8 ; late mineralization and delayed root development were associated with high risk of impaction. 8,9 A great number of publications relate to available space for eruption: impaction or eruption was correlated with the retromolar space, a higher chance of eruption occurring with an increased space 10 ; impaction was more likely to occur with early physical maturation (and corresponding limitation of mandibular growth, and thus a decrease in retromolar space). 8,9 Other findings relate to the provision of additional space through the extraction of teeth within the arch: third molars in the earlier stages of development at the time of extraction of adjacent second molars are likely to take longer to erupt, 11 and development of the mandibular third molar was accelerated on the side on which the first molar was extracted.…”

“…8,9 A great number of publications relate to available space for eruption: impaction or eruption was correlated with the retromolar space, a higher chance of eruption occurring with an increased space 10 ; impaction was more likely to occur with early physical maturation (and corresponding limitation of mandibular growth, and thus a decrease in retromolar space). 8,9 Other findings relate to the provision of additional space through the extraction of teeth within the arch: third molars in the earlier stages of development at the time of extraction of adjacent second molars are likely to take longer to erupt, 11 and development of the mandibular third molar was accelerated on the side on which the first molar was extracted. 12,13 Confounding the evaluation of available space in comparison to other permanent teeth is the potential for mandibular growth to affect arch size.…”

Effect of orthodontic treatment involving first premolar extractions on mandibular third molar angulation and retromolar space

“…Third molar root formation starts at the age of 15 and the tooth erupts at the age of 20; if formation is delayed, this will produce a risk of impaction (7). Third molar impaction is associated with a range of pathologies, and so the presence and development of these teeth should be monitored by means of panoramic x-rays (8).…”