Factors associated with mandibular third molar eruption and impaction

Abstract

A retrospective study, using panoramic radiographs, was conducted on 152 Taiwanese (72 males and 80 females) to investigate mandibular third molar eruption and impaction. The following measurements were made: inclinations and mesiodistal crown widths of the mandibular molars, vertical and horizontal spaces between the distal surface of the second molar and the anterior surface of the ramus, lengths and widths of the mandibular ramus and body, the ramus inclination, the mandibular plane angle, and the mandibular gonial angle. Differences between non-impaction and impaction groups were studied, and the variables were analyzed with multivariate discriminatory analysis. Significant differences between the two groups were found; variables describing spaces between the anterior of the ramus and the distal of the mandibular second molar and tooth size appeared to be the primary contributors to the differences observed.

Identifying the Most Accurate Available Space Analysis Method for Predicting Mandibular Third Molar Eruption or Impaction by Means of Panoramic Radiographs

“…The determining role of this factor has been advocated by Kaya and Tsai study in which the width of first and second molar was lesser in erupted group than the impacted group (4,17). This is consistent with the observation of the current study.…”

“…No correlation was observed between this angle and MTM impaction. However, Tsai reported a lower internal gonial angle in erupted group contrary to Behbahani that defined reduced gonial angle as a risk factor of MTM impaction (4,9). The angle between the lower one-third of third molar root with the line axis of third molar (tmdra) can be affected by movements of mandible and teeth especially when the anterior border of the ramus is resorbed and the corpus mandible is enlarged (24,25).…”

“…The average age of MTM eruption has been reported about 20 years ranging from 14 to 24 years (2,3). However, in case of impaction, clinical changes in tooth position have been observed up to 32 years (4). Impacted and partially erupted teeth can be associated with various problems and pathologic conditions.…”

“…The etiology of third molar impaction is multifactorial and there is a great uncertainty with the possibility of its eruption. Factors such as insufficient space, genetics, growth direction, the effect of buccinators muscles, external oblique ridge, second molar position, bone resorbtion at the anterior border of ascending ramus, mandibular growth rotation, mesio-distal width of mandibular third molar (MTM) or its angulation and its relative depth has been denoted in the literature (4)(5)(6).…”

Surgical Extraction of Mesio-Angularly Impacted Mandibular Third Molars:An Alternative Instrument for the Osteotomy Procedure

“…[1,2] As a result of this, osteotomy of the surrounding bone is part of the surgical procedure required for their extraction. [3][4][5] The surgical methods and instruments used for the osteotomy procedure have evolved over the decades, changing in contemporary practice from use of mallet and chisel to dental drill, because most surgeons and patients prefer bone around impacted mandibular third molar to be removed with bur mounted in a hand-piece with adequate moderate speed and high torque powered by a drill.…”