A premature loss of deciduous molars is one of the problems in the dental health program for the deciduous and mixed dentition period.
In recent years, there have been reports that the effect ofprematqre loss of deciduous molars on the developmental malocclusion in permanent dentition was determined by the tooth-to-denture base discrepancy. The reports are very important for the dental health management at Pedodontic clinics.
The present study was aimed at confirming the reports in regard to hte relationship between tooth-to denture-base discrepancy and malocclqsion.
The data were taken from the longitudinal dental casts of 300 school children who were surveyed over a period of seven years, and Roentogenographic cephalograms at the stage of permanent dentition.
The results obtained were as follows:
1. A significant relationship between the premature loss of secondary deciduous molar and the sever scale of the irregurality of permanent dental arch was not found.
2. The migration patterns of the first permanent molars were not significantly related to premature loss of secondary deciduous molars and the measured value in accordance with the method of Tweed. Also it could not be considered that the mesial migration of the first permanent molar principally caqsed the irregurality of the permanent dental arch.
3. The significant relationship between the sever scale of irregurality of the dental arch and the measured value according to the measurement with the exception of the Head Plate Correction from the method of Tweed, (A. L. -R. A. L. ) was found.
4. A significant relationship between a status of craniofacial (ANS-ptm, A'-ptm', S'-ptm' and pog-GO) and the severe scale of the irregurality of the permanent dental rch was found. It was suggested that the effects of premature loss of deciduous molars on the development of malocclsuion in the permanent dentitin were small, and were determined by tooth-to-denture-base discrepancy, based on a mass evaluation.