Pre-eruptive movements of the mandibular third molar.

1. It would appear that the developing mandibular third molar is continually changing its angular position relative to the mandibular plane and adjacent teeth. 2. For normal uprighting and eruption to occur growth at the mesial root must dominate. 3. In the absence of sufficient space, uprighting movements of the mandibular third molar may result in mesioangular impaction. 4. Vertical and distoangular impactions can be explained by continued growth at the mesial root while the crown is prevented, at its distal surface, from erupting. 5. If growth at the distal root becomes more influential, severe mesioangular or horizontal impaction may occur.