Malformations of deciduous teeth occur is very rare, because of their primitive forms. The abnormality of the roots of deciduous teeth as well as of crowns is rare. This case report is the supernumerary roots of deciduous molar with congenitally missing teeth in a 12-year 10-month old male. The findings are as follows : 1)In the upper right second primary molar, the supernumerary root was formed beneath a protoconule which developed without complications. 2) The lingual cusps of the upper bilateral first premolar were poorly formed. Four roots of the lower bilateral first molar and no lower bilateral second premolar were established with X-ray photographs. 3) Histologically, no fused line of enamel and dentin of the upper right second primary molar was observed. In the enamel, there was degeneration of enamel lamellae, tufts and paragons, and hypocalcification. In the dentin, degeneration of dentin tubules and hypocal cification were observed, whereas no interradicular crista and no dentin nucleus as often found in the multiple roots were observed. We report here the supernumerary roots of deciduous molar with congenitally missing teeth. The malformation may have occurred due to factors related to the process of development from the stage of the deciduous tooth buds to the permanent tooth buds.
