No teeth at 10 months

My sister’s daughter has no teeth at 10 months. Is this normal since I know that a child should produce the first tooth at 6 months?  If it is not normal, what can we do about it?

Angelina (by SMS)

Babies’ teeth usually begin to appear by the age of six months. The two lower front teeth emerge first, followed by the four upper front teeth, then the remaining two lower front teeth. The rest generally arrive two at a time – one on each side of the mouth – and by the age of three, nearly all children have a complete set of 20 primary teeth. A number of factors may be responsible for a delay in a child’s tooth eruption. Sometimes, late tooth eruption is simply a family trait. Premature and low-birth weight babies may also experience delayed tooth eruption. Nutritional deficiency and Vitamin D-resistant rickets can also cause a delay, though it may be a symptom of Down’s Syndrome, hypopituitarism or a similar developmental defect. Generally, a delay in the appearance of teeth when they occur is not something to worry about except by the age of 18 months when such cases should be taken to see a dentist.