Factors Affecting Impaction of Wisdom Teeth and Their Mechanisms
As the food chain changes in human evolution, the human maxilla went through obvious degeneration, but the number and size of teeth within the jaw did not change. As the maxilla and maxillary dentition occlude with the mandibular dentition, the mandibular teeth are constrained by the maxillary teeth; in the meantime, the maxillary teeth limit the mandibular expansion and lateral growth. Therefore, the maxillary teeth/bone mass ratio is less than the mandibular teeth/bone mass ratio. However, the impaction rate of the wisdom tooth in the upper jaw is far less than that in the mandible.