A Longitudinal Assessment of the Retromolar Space

Introduction: The size of the retromolar space – the distance between the mandibular terminal molar and the anterior border of the ramus – is one of the factors in the etiology of lower third molar impaction. It also plays an important role in decisions regarding dental extractions. Objective: This study aims to examine growth of the retromolar space in a large, longitudinal dataset. Methods: Our sample comprises 99 subjects with lateral cephalometric radiographs from three growth studies (Denver, Iowa and Oregon) taken from AAOF Craniofacial Growth Legacy Collection with data collected at 5 ages (8, 10, 12, 14, 18 years). Retromolar space was measured as the distance between the distal of the mandibular terminal molar and the anterior border of the ramus. Findings: Average retromolar space increased 8.73mm from 8 to 18 years old. The trend of growth is slightly different in that females tend to have larger retromolar spaces through age 12. Females show more growth earlier but a younger cessation. At Age 14, both sexes diverge, with males showing larger magnitude of growth going forward. There is also a non-significant trend towards larger retromolar spaces in patients with Class 1A/1B 3rd molars. Significance for practice: This information can help with space management during treatment planning in orthodontics. Conclusions: The amount of retromolar space growth seen in our study was in line with previous work. Our results failed to provide clear support for previous work, which has shown sex differences retromolar space size. We also failed to find a statistically significant relationship between third molar classification and retromolar space. Ours findings add to the body of literature establishing the typical amount of retromolar space growth to be expected at a given age.