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Comparison between different concentrations of fluoride toothpaste for preventing tooth decay in children and adolescents
[...] Although none of the trials included in the review looked at fluorosis or mottling of the children's teeth, fluorosis may be an unwanted result of using fluoride toothpaste in young children and a Cochrane review on this topic has also been published. The possible risk of fluorosis should be discussed with your dentist who may recommend using a toothpaste containing less than 1000 ppm fluoride.
This review confirms the benefits of using fluoride toothpaste in preventing caries in children and adolescents when compared to placebo, but only significantly for fluoride concentrations of 1000 ppm and above. The relative caries preventive effects of fluoride toothpastes of different concentrations increase with higher fluoride concentration. The decision of what fluoride levels to use for children under 6 years should be balanced with the risk of fluorosis.
Cochrane review on fluorosis which may be an unwanted result of using fluoride toothpaste in young children
Is the use of fluoride toothpaste during early childhood associated with discolouration/mottling of teeth?
[...] There is some evidence that brushing a child's teeth with a toothpaste containing fluoride, before the age of 12 months, may be associated with an increased risk of developing fluorosis. There is stronger evidence that higher levels of fluoride (1000 parts per million (ppm) or more) in toothpaste are associated with an increased risk of fluorosis when given to children under 5 to 6 years of age. However, for some children (those considered to be at high risk of tooth decay by their dentist), the benefit to health of preventing decay may outweigh the risk of fluorosis. In such circumstances, careful brushing by parents/adults with toothpastes containing higher levels of fluoride would be beneficial.
There should be a balanced consideration between the benefits of topical fluorides in caries prevention and the risk of the development of fluorosis. Most of the available evidence focuses on mild fluorosis. There is weak unreliable evidence that starting the use of fluoride toothpaste in children under 12 months of age may be associated with an increased risk of fluorosis. The evidence for its use between the age of 12 and 24 months is equivocal. If the risk of fluorosis is of concern, the fluoride level of toothpaste for young children (under 6 years of age) is recommended to be lower than 1000 parts per million (ppm).
More evidence with low risk of bias is needed.