The influence of arch shape on the incidence of third molar impaction: A cross-sectional study

Impaction of third molar is a pathological problem that reduces the chance of normal eruption of tooth. The main reason for impaction is inadequate space in the maxillary and mandibular arch. The aim of this study is to investigate the relationship between arch shape and the prevalence of third molar impaction.

This cross‑sectional study was performed on patients referring to the Department of Oral and Maxillofacial Surgery between December 2023 and February 2024 to obtain an orthopantomogram (OPG). Convenience sampling was employed, and orthopantomograms were analyzed to determine impaction types. Dental arch shape variables were assessed using Budiman's analysis, with a Chi-square test employed to evaluate any significant association between arch shape and impaction type at a significance level of 0.05.

Among the 185 maxilla and 185 mandibles studied, 154 were male patients, and 216 were female patients, with a mean age of 26.75 years. A statistically significant difference was found in impacted teeth, among females having more impacted molars than males (p-value = 0.002*). However, no significant differences were found in the type of impaction, Gregory classification, or position based on the shape of the mandible on both the right and left sides (p-value > 0.05). Similarly, no significant differences were observed in Gregory's classification based on the shape of the maxilla on both the right and left sides. However, there is a statistically significant difference in the occurrence impaction based on the maxilla's shape (p-value < 0.05).

The study suggests a significant correlation between maxillary arch shape and the occurrence of third molar impaction, with a higher prevalence among females.