Occlusal migration of the maxillary first primary molars subsequent to the loss of antagonists.
The purpose of this study was to observe the vertical changes in unopposed maxillary first primary molars longitudinally. The subjects of this study were 17 children whose lower first primary molars had to be extracted. Space closure were prevented by crown-loop space maintainers for all these children. Plaster casts were made every 4 months for 16 to 24 months after the extraction. These series of casts were standardized, and vertical changes of the maxillary first primary molars against the occlusal plane were measured using a micro-reader. The mean changes indicated that maxillary first primary molars without intercuspidation tend to drift toward the extraction space. On the control side with antagonists, the maxillary first molars seemed to move reversed to apical throughout the observation period. Accordingly, the results of this study showed new trends after the premature loss of primary molars. The vertical changes toward extraction space varied from -0.40 mm to 1.43 mm at the 16 months after extraction. Mean changes were small, but there were some individual differences in reaction, giving negative values. However, we should always be concerned about loss of arch length and also occlusal drift of unopposed teeth, because the vertical changes were greater than 1 mm at 16 months after extraction in some cases.
Yonezu
T
T
Department of Pediatric Dentistry, Tokyo Dental College, Chiba, Japan.
Machida
Y
Y
D002648:Child; D002675:Child, Preschool; D003766:Dental Occlusion; D006801:Humans; D008137:Longitudinal Studies; D008334:Mandible; D008437:Maxilla; D003765:Models, Dental; D008963:Molar / Q000503:physiopathology* / Q000601:surgery; D013027:Space Maintenance, Orthodontic / Q000295:instrumentation; D013997:Time Factors; D014081:Tooth Extraction; D014085:Tooth Migration / Q000209:etiology* / Q000503:physiopathology; D014094:Tooth, Deciduous / Q000503:physiopathology* / Q000601:surgery