Fluoride in the mouth is regulated in much the same way by both systemic and topical fluoride, but the way fluoride amounts are retained in the mouth differs. Fluoride from the water source is absorbed and stored in bone, which serves as a reservoir.
Bone is a living, continually remodeling material that is broken down and replaced as part of natural bodily activity. Fluoride is absorbed back into the bloodstream during this process, where it is then released into saliva and available to work on tooth surfaces. Toothpaste with fluoride improves fluoride supply at the tooth surface.
The amount of fluoride consumed is what decides whether it is healthy. If ingested by small children, topical fluorides, such as those used in toothpaste, may have a systemic effect. The only way to avoid dental fluorosis is to use a pea-sized volume of toothpaste with controlled brushing.
Fluoride levels of 0.05-0.07 milligrams per kilograms of body weight per day are commonly considered to be optimal. For every two pounds, this equates to around a tenth of the weight of a grain of salt.
However, because of the wide range of fluoride amounts in various foods and drinks, calculating the optimum dose is nearly impossible. For example, a person living in a non-fluoridated water culture cannot be believed to be consuming low quantities of fluoride because fluoride is often consumed by large volumes of soft drinks or juices.
Still, people should know approximately how much fluoride they are ingesting since they have a better awareness of their diet. It is better to avoid excessive intake.