We’re back after a hiatus of a couple of years. Us smiling up at the top? No, that’s a mild form of dental fluorosis.

A recent report from the Centre for Disease Control and Prevention on the use of toothpaste and tooth-brushing patterns among children and adolescents (https://www.cdc.gov/mmwr/volumes/68/wr/mm6804a3.htm)suggests that young children are using and swallowing too much fluoridated toothpaste when brushing their teeth. They recommend that children under the age of 2 should use a non-fluoride toothpaste and those aged 3-6 should only use a pea-sized portion on their brushes.

Let’s dissect this advice down into its parts, or as they say these days, let’s unpack it. The prime idea here should be to do what is necessary, what is practical, and to not make compliance so difficult or complicated that it would turn some of us off from doing the right thing.

First of all, brushing is important. It should be done as soon as the teeth come into the mouth (about 6 months of age and later), preferably after each time a child eats (or drinks from the mom’s breast or a bottle), but since this is maybe impractical in some cases, like the middle of the night where mom is exhausted, do it at least once or twice a day. (Do it in the middle of the night too, if you can.) That way, bacteria won’t build up a layer thick enough to start retaining acid (from sugar breakdown by these germs) which will start to leach calcium from the tooth surface (and so cause tooth decay.)

Second, fluoride at proper levels has been shown over many years to be beneficial to tooth health, by changing the crystal structure of enamel so that the enamel is more resistant to acid. Fluoride has therefore been added to the water supply of many cities as a public health measure. Almost 200 million people in the U.S. and 300 million world-wide have fluoride added to their water supply.

Third, fluoride can enter tooth enamel in 2 ways, either when the teeth are still under the gums, and after they are already visible in the mouth. Before teeth come into the mouth, the enamel may still be forming and fluoride present in the bloodstream bathing these teeth increases the fluoride content as enamel is laid down as the outside layer of the teeth. After the teeth are already in the mouth, fluoride applied to the teeth strengthens the outer layer of enamel. Fluoride that moves from the blood into the saliva in the salivary glands also can contribute to this beneficial process.

Fourth, too much fluoride can cause white spots (see photo above) or lines on developing teeth (termed “fluorosis”), which are teeth which haven’t yet broken through the gums and entered the mouth. By the way, this growth of teeth from below the gums into the mouth is called “eruption”, sort of like a volcano erupts lava from underground onto the earth’s surface. I know, it’s a weird comparison but the term has been around for a long time, so what can you do?

If the concentration of fluoride your child is exposed to is significantly higher than 1.2 parts per million (ppm), fluorosis can result. If it is higher than that (the upper limit here is not well-defined), the enamel can be disrupted enough that surface defects, staining, and weakening of the enamel’s strength can happen. It’s therefore important that the fluoride concentration stays in the “Mama bear” zone (thanks, Goldilocks, for giving us this concept of just-rightness.) The two permanent upper front teeth, which are the most esthetically important teeth when we smile, have generally completed enamel formation between 15 to 24 months for boys, and between 21 and 30 months for girls, so fluorosis can happen to these teeth during this period.  Also, because we drink more when it’s hot, people living in a hot climate should probably have less fluoride added to their water, since they’ll drink more and absorb more fluoride, possibly producing fluorosis more easily.

Fifth, it’s clear that young children, if unsupervised, will not follow dental association guidelines (or listen to you, either.) Toothpaste, especially the fruit-flavoured children’s toothpastes, appeals to kids’ natural affinity for sweet flavours, so watch out.

Sixth, below the age of 6, children haven’t developed enough control over the swallowing reflex and the ability to spit to prevent swallowing of toothpaste. Some, if not most, will be swallowed. So, obviously, preparing the toothbrush with the right amount of fluoride toothpaste by a parent or supervising adult is very important. As for the right amount to put on the toothbrush, a very thin smear of toothpaste for kids below the age of 3, and a pea-sized blob, not more, is recommended after 3. The parent actively doing the brushing is really the best way to go.

So, finally, use of a non-fluoride toothpaste below the age of 3 is probably a good idea, and using a children’s fluoridated toothpaste, which has half the adult concentration of fluoride, from 3 to 6 years of age, is also recommended. And a parent should always be watching and helping young children brush their teeth. I hope all this is clear and convincing.

And don’t forget the dental floss (again, done by the parent), especially once the teeth next to each other are touching.