<P> During birth, fontanelles enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal . The ossification of the bones of the skull causes the anterior fontanelle to close over by 9 to 18 months . The sphenoidal and posterior fontanelles close during the first few months of life . The closures eventually form the sutures of the neurocranium . Other than the anterior and posterior fontanelles, the mastoid fontanelle and the sphenoidal fontanelle are also significant . </P> <P> In humans, the sequence of fontanelle closure is as follows: </P> <Ol> <Li> The posterior fontanelle generally closes 2 to 3 months after birth; </Li> <Li> The sphenoidal fontanelle is the next to close around 6 months after birth; </Li> <Li> The mastoid fontanelle closes next from 6 to 18 months after birth; and </Li> <Li> The anterior fontanelle is generally the last to close between 18--24 months . </Li> </Ol> <Li> The posterior fontanelle generally closes 2 to 3 months after birth; </Li>

When do the anterior and posterior fontanelles close
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