Abstract
The purpose of this study was to observe the sequence of the eruption of the permanent teeth longitudinally, using 1607 serial plaster models of maxillary and mandibular dental arch taken every three months. The materials consisted. of a total of 60 cases which included 31 with normal occlusion, and 29 with malocclusion (6 with maxillary prognathism,10 with bimaxillary prognathism and 13 with crowding).
The phenomenon observed in this study was the sequence of the eruption of all permanent teeth except the third permanent molars, and specifically in detail,1) the sequence of eruption and the occlusion of the first molars and the central incisors,2) the sequence of eruption and the occlusion of the four incisors,3) the sequence of eruption and the occlusion of buccal segments, and 4) the sequence of eruption of the second premolars and the second molars.
The results are summarized as follows:
1) Not one case out of 60 cases showed the same sequence of eruption of the 28permanent teeth, the first-emerged tooth to the second molar erupted.
2) The mandibular central incisor erupted earliest in 46.7 % of the cases, the mandibular first molar in 45.0%, and the maxillary first molar in 8.3%.
3) Regarding the sequence of the first molar and the central incisor, Type (1→6 was found in 30.0% of the cases, and Type (6→6) in 23.3%. Concerning the occlusion, normal occlusion showed Type (6→) and Type (1→) with the same percentage.
4) Regarding the sequence of eruption of the four incisors, Type (1→2→1→→ 2) was found in 58.3 % of the cases. Both normal occlusion and abnormal occlusion showed Type (1→2→1→2) in many cases.
5) Regarding the sequence of eruption of the maxillary buccal segments, Type (4→3→5) was found in 38.3% of the cases, Type (3→4→5) in 20.0% of the cases and Type (4→5→3) in 15.0% of the cases. Normal occlusion showed Type 4→3→5) in many cases. Maxillary prognathism did not show a case with Type (4→5→3). Crowding showed comparatively many cases with Type (4→5→3).
6) Regarding the sequence of eruption of the mandibular buccal segments, Type 3→4→5) appeared in 70.0 % of the cases. All of the variations of occlusion showed many cases with Type (3→4→5).
7) Cases in which the second molar erupted earlier than the second premolar were not found so frequently unilaterally in the maxillary arch (2.6%) of the cases, unilaterally in the mandibular arch (13.6%) of the cases, and bilaterall y in the mandibular arch (8.5%) of the cases.
