Eruption process of the second molar

The second molar is located at the distal of the first molar, and we must b e aware of its stage of development when we plan to move the first molar di stally. Few researchers have investigated the development of second molars. The purpose of this study was to observe the eruption process of the maxil lary and mandibular second molars by using 238 panoramic radiographs. The d evelopmental stages of the second molar were divided into four stages: the whole crown calcified = stage 1;beginning root formation = stage 2; initial formation of the radicular bifurcation = stage 3; and the root length is e qual to the crown height = stage 4. The mesiodistal crown width of the firs t and second molars, axial inclination and eruption rate of the second mola r, and the space available for emergence of the second molar at each stage were measured, and the statistical analysis was made to assess the developm ental changes. It was learned that the mandibular second molars began to er upt at stage 3 and the maxillary second molars at stage 2. The axial inclin ation of the mandibular second molars maintained almost the same angle and the maxillary second molars were uprighted gradually from stage 1 to 4. The available space increased significantly from stage 1 to 2 in both second m olars. It is suggested that the space available for emergence of the second molar is prepared before stage 2, and then the tooth begins to erupt. As t he maxillary second molars, there was further increase in the available spa ce after stage 3. Negative correlation was seen between the mesiodistal cro wn width of the mandibular second molar and the available space in stage 2. Positive correlation was seen between the mesiodistal crown width of maxil lary second molar and the available space in stage 3. It is suggested that greater increase in the space available for emergence of the second molar c ould be expected in the maxillary dental arch, if the mesiodistal crown wid th of the second molar required it.