Adequacy of mandibular premolar position despite early loss of its deciduous molar

The mandibular second premolar (MnP2) tooth is one of the most commonly impacted teeth. Early loss of its deciduous predecessor has long been suggested to be a factor in the etiology of the MnP2 impaction. In this study, panoramic roentgenograms were used to measure the angular position of the unerupted MnP2 in 85 children. The study was carried out to test whether early loss of the lower second primary molar (dM2) correlates with MnP2 malpositions that are measurably greater than those from a control sample. The results show a small and statistically insignificant difference between the mean angles in cases with (79.6 degrees) and without (83.2 degrees) dM2. To eliminate individual factors, e.g., genetics, 2 sides of the same patient, with and without dM2, were compared. The group with the missing dM2 on one side showed higher angle differences, compared with the control group. However, the differences were still small (approximately 4 degrees) and statistically insignificant. Our findings do not show a significant influence of early loss of dM2 on the inclination of the unerupted MnP2, suggesting that environmental factors may be of less significance, compared with genetic ones.