Dental examination and interview of all 185 pupils of third and fourth grade at 9-10 years old who have had full first permanent molars and have had full 4 permanent incisors in Phung Chau primary school, Chuong My, HanoI showing effects of eary losing molar deciduous on tooth deviation: - Change of the occlusal relation between the upper and lower first molars: Make more increasing in rate of type II and type III occlusion than group not having early losing deciquous molars, that has statistical meaning. - There is narrow space available in the children early losing deciduous molars in both lower jaw and upper jaw. - There is rotation of primary first molars: In the upper jaw: 77,28 percent ; In the lower jaw: 60,00 percent. - Rate of malposition of permanent premolars is 72,73 percent .
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