Many parents wait until there is a problem, but the better approach is to start early. Most children's dentists recommend a first visit by age one, or within six months of the first tooth appearing. At that stage the goal is not much treatment — it is to get the child used to the clinic and let the dentist check that everything is developing normally.
The dentist will usually look at the teeth and gums, check how the bite is developing and talk through brushing, diet and any habits like thumb-sucking. It is short and gentle, and the child often sits on a parent's lap. This low-stress start makes later visits much easier.
In Singapore there are many practices that specialise in children, with play areas and staff trained to put nervous kids at ease. Choosing one of those for the first few visits is often worth a little extra travel.