This article describes four cases having submerged primary teeth in the mixed dentition and mesial inclination of the first permanent molars adjacent to these teeth, which caused a space shortage for eruption of the succedaneous permanent teeth. Space regainers were utilized for up-righting the first permanent molars and creating the space for eruption of the submerged primary teeth and consequent eruption of the succedaneous permanent teeth. Longitudinal clinical evaluations using the X-ray pictures and the study models were performed on these four cases to verify the space regaining for the submerged primary teeth.
The following findings were obtained.
In Case 1, the submerged upper left second primary molar re-erupted to such an extent as to obtain the occlusal relationship with the antagonistic tooth after up-righting the adjacent first permanent molar. In Case 2, the submerged upper left second primary molar re-erupted up to the whole exposure of the occlusal surface after up-righting the adjacent first permanent molar. In Case 3, the submerged teeth were the lower left first and second primary molars. After up-righting the first permanent molar, the root resorption of these teeth were observed with the development of the succedaneous permanent teeth which erupted in the normal position of the dentition. In Case 4, the bimaxillary left second primary molars were severely submerged, and the mandibular second primary molar was completely embeded. During the space regaining for these teeth, the upper second primary molar exhibited some extent of pre-eruptive movement with the succedaneous permanent tooth, and root resorption of the lower second primary molar was observed in accordance with development of the succedaneous permanent tooth.
In summary, these observations suggest that the submerged second primary molars in the mixed dentition period should be treated with the space regaining procedure involving up-righting the adjacent first molar, since this facilitates re-eruption of the submerged primary molars as well as eruption of the succedaneous permanent teeth.