The use of silver fillings in baby teeth and children under the age of 15 will be restricted from Monday.
The move comes following an EU directive and restricts the use of the amalgam fillings in children except when strictly necessary.
The directive is part of an EU push to reduce the release of mercury into the environment.
It also restricts amalgam fillings for pregnant or breastfeeding women, again unless deemed necessary by the dental practitioner.
Northern Ireland's Chief Dental Officer Simon Reid said dentists across the UK have been avoiding amalgam when treating pregnant women for the last 20 years.
"The new EU directive is not a reflection on any specific safety concerns and there is no evidence of any real direct health risk from amalgam," he said.
"Methods used by dentists in its preparation, use, and disposal, already reduce any exposure to mercury.
"Your dental professional will be able to offer you the best advice for your situation and explain what filling material is most appropriate for your needs.
"This may still be amalgam. It is still an effective filling material for particular situations, and the EU and UK Regulations allow exemptions when amalgam can be safely used in the same way that it has for many years."
Mr Reid added people should work to prevent the need for fillings by minimising dental decay.
"Firstly, reduce the consumption of food and drinks that contain sugars, particularly at bedtime," he said.
"Secondly, brush at least last thing at night, and another time during the day with a fluoride toothpaste. Your dental team can advise on toothpaste strength and quantity.
"Thirdly, visit your dentist regularly, taking your children from a very early age."