What is the most common reason for the impaction of the second molar?

The most common reason for the impaction of the second molar is arch length discrepancy. This occurs when there is insufficient space in the dental arch for the tooth to emerge properly.

As the second molars typically erupt around ages 12 to 13, any crowding or lack of arch length can lead to the second molar being pushed into a position that prevents it from fully breaking through the gums. Such crowding often arises due to the presence of other teeth in the arch, impacted teeth, or other developmental factors that result in a mismatch between the size of the teeth and the available arch space.

Understanding the significance of arch length is crucial, as it directly influences the positioning of newly erupting teeth, including the second molars. Other factors, while they can contribute to tooth impaction, are less frequently the primary cause compared to the issues stemming from arch deficiencies.