What are the costs of consultation or treatment?
In the Netherlands children up to 18 years are insured for dental care. The applicable dental rates that are calculated are determined by the Dutch Healthcare Authority. https://www.nza.nl/1048076/1048144/TB_CU_7135_01__Tandheelkundige_zorg.pdf
When you have a Dutch insurance, the consultation or treatment is directly invoiced to the health insurance. You do not have to pay in advance. If you do not have Dutch health insurance, you pay after the consultation. You receive a letter for the insurance which explains about the treatment and costs, so you may can get it reimbursed.
For the costs of a consultation or treatment of therapists other than dentists, you should contact the relevant practitioner.