Age has no relevance on how a child acts in a dentist office. There might be a four-year old who feels just fine while he is getting a filling while a ten year old may be extremely anxious and nervous.  Sometimes sedation is necessary for certain patients.  It is recommended to start taking your child to the dentist at a very early age.  For sure by the time they are 3 and earlier is better. They will get used  to coming to the dentist with regular early visits, their teeth will be well taken care of and they will learn proper brushing techniques and how to care for their teeth.