抄録
The object of this study was to know what changes take place on the buccal segment during the period of change of dentition, and the following conclusions can be made from its result. 1) The space for the alignment of the permanent buccal teeth changes during the period of change of dentition in buccal segment. The main increase of this space occurs during the period of eruption of the permanent canine and some of the permanent first premolar. These kinds of increase make it possible for the permanent canine and the permanent first premolar to align normally. The main decrease of this space takes place through the replacement of the deciduous second molar by its predecessor. 2) As the permanent canine positions more mesially than its predecessor, the permanent first molar is able to migrate mesially more than the amount of the leeway space between the crown diameters of the deciduous buccal teeth and those of their permanent successors. 3) The leeway space is not always necessary for the permanent buccal teeth to align, and it is a part of available space for the alignment of the permanent buccal teeth.
