Scientists Discover Why Teeth Form in a ...(al program outside of the normal tooth r...),Health

Why Extra Teeth Formed

When we lose our baby teeth, the permanent teeth grow in to replace them, but permanent teeth when lost are lost for good. U.S. adults aged 20 years and older are missing an average of four teeth due to gum disease, trauma or congenital defects. Tooth loss makes chewing difficult, causes speech problems, accelerates oral disease, and disfigures the face. Current treatments for missing teeth include dentures or dental implants, but each procedure comes with disadvantages. The idea of growing teeth to replace missing ones has captured the imaginations of scientists, with many labs investigating ways to regenerate teeth.

In the current study, Jiang and colleagues generated mice that lacked the oddskipped related-2 (Osr2) gene, which encodes one of many transcription factors that turn genes on or off. "Knocking out" (deleting) the Osr2 gene resulted in cleft palate, a birth defect where the two halves of the roof of the mouth fail to join up properly, leaving a gap. Secondly, and surprisingly, the Osr2 "knockout" mice developed teeth outside of the normal tooth row. Jiang decided to focus his research first on the effect of Osr2 on teeth patterning (vs. cleft palate) because much more was known at the time about teeth development pathways.

Although teeth usually do not become visible until after birth, their formation starts early in development. Teeth develop from the epithelium and mesenchyme, two key tissue layers within the mammalian embryo. The first sign of tooth development in mammals is the thickening of the epithelium along the jaw line to form a band of cells called the dental lamina. Because all teeth subsequently form from the dental lamina, the assumption was that some sp
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