Prevalence and pattern of third molars impaction in a large Yemeni sample: a retrospective study

The prevalence of teeth impaction varies substantially between different populations, and the impaction of third molars is the most commonly recorded. This study aimed to explore the prevalence and pattern of the third molars impactions among Yemeni population. This was a retrospective radiographic study conducted in Yemen between 2022 and 2023. The digital panoramic radiographs were collected from two major X-ray centers in Yemen. The angular position and depth of the impacted third molars were assessed according to the classifications of Winter and of Pell and Gregory, respectively. All radiographs were evaluated twice by one investigator in a two-week interval, and Kappa test was used for intra-rater reliability. Gender-wise differences, differences between both sides, and differences between maxilla and mandible were analyzed using Chi-squared tes with odds ratio (OR) for the risk of impaction. A P-value < 0.05 was considered significant. Panoramic radiographs of 6338 individuals were included. Their mean age was 35.1 ± 13.3 years andand 63.9% were females. A total of 25,352 sites (quadrants) were screened for the presence of thirds molars. Among which, 14,003 third molars (55.3%) were present in one or more sites. There were 1440 individuals (23%) with a total of 2828 impacted third molars (20% of the existing third molars). Females were less likely to have third molar impaction (OR = 0.46, CI_95% = 0.4-0.52). Impaction of the mandibular third molars was significantly more frequent than the maxillary ones (OR = 1.15, CI_95% = 1.04-1.26; P = 0.005). Horizontal and mesioangular impactions were statistically more frequent in the lower molars compared to the upper ones (P < 0.001 each). Contrastingly, vertical (P = 0.015), distoangular, and other impactions (P < 0.001 each)were statistically more frequent in the maxilla. Levels A and B were more frequent in the lower third molars, while level C was predominating in the upper molars (P < 0.001 each). The prevalence of third molars impaction is more frequent in males and mandibular arch. The angulation and level of impaction seem to be more complicated in the maxillary arch.