Impaction of Lower Third Molars and Their Association With Age: Radiological Perspectives

Soukaina Ryalat; Saif Aldeen AlRyalat; Zaid Kassob; Yazan Hassona; Mohammad H. Al-Shayyab and Faleh Sawair


BMC Oral Health. 2018;18(58) 

In This Article


The main referral center for third molar teeth extraction for university students, of which the age group range of this study was selected, is the maxillofacial department at our university hospital. The decision of extraction of third molar teeth may be affected by the surgeon's opinion on the eruption potential of the tooth. A tooth that may appear impacted at the age of 18 years may have as much chance as 30 to 50% of erupting fully, except horizontally impacted molars.[9] The selected group of age (18 years to 26 years) that were included by the study covers the age range that most likely to show significant lower third molar movement.[9]

The study showed no significant differences between male and female patients in all calculated values (p > 0.05). This finding supported by several studies, except that they found an earlier eruption of third molars compared with males.[10] The lower third molar teeth in this study showed a significant increase in angulations between the ages 20–23 years, in which studies from Europe and United States of America had similar findings.[11–13]

The mesioangular impaction was the most frequent impaction by 66.1%, while the horizontal impaction was the least common 15.1%. mesioangular impaction was also found to be the most common in Turkey, Singapore, and China.[14–17] In Sweden, vertical impaction was found to be the most common,[18] whereas the vertical impaction was 18.8% in our population.

More vertically angled third molars are seen in older age group, this angulation is the significant point the surgeon looks for when deciding to extract, taking into consideration patient's age. In this study, the prevalence of vertical impaction in patients older than 20 years was significantly higher (21.4%) and the prevalence of horizontal impactions was significantly lower (11.7%) than that in younger patients whose incidences were (14.0%) and (21.3%), respectively. Additionally, as found by others,[19,20] a constant pattern of an increase in the retromolar space was noticed with increasing age of patients (P < 0.001). This was reflected in a constant pattern of increase in Pell-Gregory ramus class 1 with increasing age, which will have a big effect to reduce surgical complications since the tooth may favor eruption. This signifies the importance of re-evaluating patient's radiograph considering the possible changes of impacted lower third molar teeth that could occur with time, especially for younger patients.[1] Moreover, third molars remain impacted after the age of 25 may still change in position afterward.[21]

We believe this study has limitations that should be considered in future projects. Following patients' clinical and radiological data in a cohort study design or retrospectively in a case-control design will provide a quality evidence on the prophylactic removal, complications, and outcome of third molars.