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 sample was composed of 1198 patients (566 males, 632 females) with a total of 1810 impacted lower third molar teeth (1224 bilateral impactions, 586 unilateral impactions) with an age range between 18 and 26 years. The majority of impactions (66.1%) were mesioangular, followed by vertical impactions (18.8%), and horizontal ones (15.1%). The radiographic average width of the impacted molars was 10.1 ± 1.4 mm (range: 8–16.5 mm), (Table 1).

The prevalence of vertical impaction in patients older than 20 years old was significantly higher (21.4%) and the prevalence of horizontal impactions was significantly lower (11.7%) than that in younger patients (14.0%) and (21.3%), respectively (P < 0.001). The third molar angulation changed significantly between age groups, however, there was no constant pattern from year to year. When age groups were studied, the angulation of lower third molar teeth was significantly higher in patients older than 20 years old (46.2 ± 26.8) compared to younger patients (38.4 ± 25.1), (P < 0.001).

A constant pattern of an increase in the retromolar space was noticed with increasing age of patients (P < 0.001), the space was close to the average width of the lower third molar teeth after the age of 25 years. This was reflected in a constant pattern of increase in Pell-Gregory ramus class 1 with increasing age, as prevalence of class 1 was 0% at age 18 years compared to 54.9% at the age of 26 years.

The mesial and distal roots' lengths increased significantly with age as shown in (Figure 3), (P < 0.001). This was revealed by a constant pattern of decrease in the distance of the tooth to the occlusal line with increasing age of patients (P < 0.001) and a statistically significant increase in the prevalence of Pell-Gregory ramus level B with increasing age (P < 0.001).

Figure 3.

Increase in length of mesial and distal roots of lower third molar teeth with age