What may suggest that treatment is necessary?

when upper front teeth stand very much in front compared to those below
when upper front teeth completely cover up lower teeth
when upper front teeth are behind lower teeth
when front teeth do not touch (i.e. there is a gap)
when teeth are crooked
when the upper and lower jaws do not fit together
when a child is still ‘sucking’ something (e.g. a thumb or an object) beyond 8 years
when chewing is difficult
when lower jaw slides to one side
when there are spaces between teeth