Abstract
We surveyed the progression of permanent molar eruption to analyze its difference between the right and left side of the jaw. A total of 476 children were selected among children who visited our clinic, based on specific criteria for this study.
Results
1. The tooth germ of the first molar started moving for eruption at 3-4 years old intramandible, and at 4-5 years intra maxilla. Then the first molar was going to erupt and reached the occlusal plane at 7 years old in mandible, and at 8-9 years old in maxilla although there were individual variations.
2. The cases with differential progression between right and left sides in first molar eruption occupied 13.2%. Unexpectedly, however, the cases with such difference in first molar formation occupied only 7.4%. This suggests that tooth eruption is only partially correlated with its formation and, therefore,additional factors might play a role in tooth eruption, which remains to be elucidated in this study.
3. In most 6-year old children, the root of mandibular first molar completed up to 2/3 of the mature root length, while 1/2 in maxilla. Individual variations were also seen in maxilla.
4. In some cases with the delayed eruption of first molar, the second molars were also delayed to erupt. These first and second molars were not always side by side.
We clinically encounter many cases with a differential progress between the right and left sides in permanent molar eruption. It is not feasible to diagnose these cases as physiological variations or abnormal eruptions. The data presented here will give helpful information to determine whether any treatments are required for these cases.
