272 primary school children between the age groups of six to ten were examined and of these objects, 50 primary second molars which should be extracted, were selected and then primary first and permanent first molars were observed for six months.
The results were as follows.
1) Mesial shift of permanent first molar was 1.7mm in male, 1.2mm in female.
2) The length increase from the lingual interdental papillae of the central incisors to the mesial surface of primary first molar was 0.5mm in male, 0.2mm in female.
3) The canine to canine width was increased 0. lmm more than the arch width in both sexes.
4) The increase of arch width was 0.4mm in male, 0.3mm in female, and the case in arch length was 0. lmm in male and 0.04mm in female.
5) The primary teeth should be maintained in a healthy condition to allow proper eruption of the permanent teeth.
In case of premature loss of the primary teeth, the space maintainer should be indicated.
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