Enamel hypoplasia is a defect of the enamel that only occurs while teeth are still developing. Still, it can affect both baby teeth and permanent teeth. The condition results in thin enamel, which makes your teeth vulnerable to dental decay. Enamel hypoplasia caused by environmental factors carries the same symptoms as hereditary enamel hypoplasia, but can be caused by a variety of factors, such as premature birth, malnutrition, bacterial and viral infections, or trauma to newly developing teeth and mouth.