Comparing Eruption Space of the Lower Third Molar in Unerupted and Erupted Teeth via Digital Anoramic Radiography in Patients Referring to Yazd Dental College during 2011-13

The aim of this study is to determine and compare the eruption space of unerupted and erupted third molars by the means of digital panoramic radiography in patients referring to Yazd dental college during 2011-2013. In this cross-sectional descriptive study, 150 archived digital panoramic radiographies in radiology department were evaluated with Romexis software under the standard circumstances. The radiographic pictures belonged to 73 men and 77 women with the average age of 21.18±1.67 years. In patients with erupted third molars as well as unerupted third molars (mesio-angular and vertical), several parameters were examined including: angle of the tooth axis of second and third molar, Gonial angle, the width of third molar, retro-molar space and its ratio to the width of third molar, the development stage of third molar root as well as the distance between the center of ramus and the most distal point of second molar. The data related to age, sex and the eruption situation of lower third molar- unerupted or erupted- were extracted from the patient’s log. The data were analyzed by SPSS (ver.17) via applying descriptive tests and T-test. A statistically significant difference was observed between the two groups in regard with the average angle between second and third molar, the mean space of retro-molar and its ratio to the width of third molar as well as the mean distance between centers of ramus and second molar (P=0.0001). Moreover, no significant difference was observed in Gonial angle mean (P=0.213) and the width of third molar (P.value=0.348). Increasing the angle between second and third molar as well as inadequate space of retro-molar can lead to impaction of lower third molar, but the width of third molar and the Gonial angle size did not reveal any significant role in determination of impaction or eruption of third molar.