Author/Authors :
Hosseinzadeh Nik، Tahereh نويسنده Department of Orthodontics and Dental Research Center,
Dentistry Research Institute, Faculty of Dentistry, Tehran
University of Medical Sciences, Tehran, IR Iran , , Jalayer، Toktam نويسنده Department of Radiology, Dental School, Shahed University, Tehran, IR Iran , , Beymouri، Amine نويسنده Private Practice, Tehran, IR Iran , , Saffar Shahroudi، Atefe نويسنده Department of Orthodontics, Faculty of Dentistry, Lorestan University of Medical Sciences, Khorramabad, IR Iran , , Eftekhari، Armin نويسنده Private Practice, Tehran, IR Iran ,
Abstract :
Background Third molar impaction is a major problem facing the
dental profession and its impacts on the dentition has long been a major
concern. Third molar is the most frequently impacted tooth. The
prevalence of mandibular third molar impaction has been reported from 18
to 32 percent which varies between populations and races. Objectives
This study was designed to determine the best retromolar space analysis
from available methods with the highest correlation with mesio-distal
width of mandibular third molar (MTM) in order to predict its eruption
or impaction. Patients and Methods Measurements were carried out on
digital panoramic radiographs of 98 Iranian patients. One hundred and
seventy mandibular third molars were divided into 4 groups: impacted
females, impacted males, erupted females and erupted males. Twenty eight
points and 24 planes were marked on the radiographs: 11 points in
relation to retromolar space analysis and the mesio-distal width of MTM;
and 17 points in relation to some anatomic variables assumed to be
related to MTM eruption or impaction. Using these landmarks, different
methods were tested for analyzing the retromolar space and its relation
to the width of the MTM. Student’s t-test was applied for comparison
between erupted and impacted groups and ROC curve was drawn to determine
the method with the highest specificity and sensitivity. Results Among
the performed retromolar space analysis, the method that measured the
distance between distal surface of second molar and the anterior border
of ramus parallel to functional occlusal plane had the highest
correlation with the MTM width. Also, the impact of some anatomic
factors including posterior ramus height, upper body length, etc. on MTM
eruption or impaction was observed. Conclusions Retromolar space
analysis on panoramic radiographs can be a relatively precise predictor
for mandibular third molar eruption or impaction. This study also
supports the multifactorial concept about third molar impaction.
