Tooth agenesis is the most common developmental anomaly of the human dentition. Epilepsy-like disorder (EL) mice, which have a 100% incidence of agenesis of the third molars, may be a good model for the genetic study of human tooth agenesis. Our previous congenic breeding strategy using EL mice confined a major locus for agenesis of M3, designated am3, within an approximately 1 Mega base pair (Mbp) interval on chromosome 3, which contains five known genes; Lef1, Hadh, Cyp2u1, Sgms2 and Papss1. The aim of this study was to identify the strongest candidate for am3 among the five genes using real-time PCR analysis. The tooth germs of M3 in the bud stage of EL and control mice were dissected out, and total RNA was extracted. In real-time PCR analysis, a significantly low level of expression of Lef1, which is one of the essential transcription factors for early tooth development, was observed in M3 of EL mice. In addition, a significantly low level of expression of Fgf4, which is a direct transcriptional target for LEF1 in early tooth development, was observed in M3 of EL mice. Our results suggest that the cause of M3 agenesis of EL mice may be a low level of Lef1 expression in M3 in the bud stage of EL mice.

In order to study the relations of malocclusion formation and feeding behavior as a scientific research project, we measured the 3-D morphology of 31 healthy newborns within 7 days of birth and 1 month later using dental casts. Nine characteristics were selected and the developmental changes were analyzed using specialized software for investigating palatal development in detail. The results revealed that the palatal width, 3 palatal characteristics relating to depth, maximum slope location, and mean slope increased significantly during the 1 month, but there were no significant changes observed in palate length, cuspid ratio, and maximum slope. There was a significant correlation between palate depth and maximum depth point location, suggesting that the deeper points tended to be located further back. No significant correlations were observed between newborns within 7 days of birth and 1 month after birth for cuspid ratio, maximum depth point location, and maximum slope. Our observation of inter-characteristics correlations revealed 7 significant (P < 0.01) combinations out of a total of 33 combinations were observed in newborns within 7 days of birth, while only 4 were observed in 1-month-old infants. This appears to have been because of morphological changes occurring between individuals due to growth. Thus, it was clarified that not only size but shape (cuspid ratio, maximum slope point location, and the mean slope) also changes over the first month after birth. (C) 2013 The Japanese Society of Pediatric Dentistry. Published by Elsevier Ltd. All rights reserved.