 This is because there is clear evidence that optimal concentrations of fluoride provide protection against cavities, both in children and in adults.The scientists or doctors who oppose water fluoridation argue that it has no or little cariostatic benefits, may cause serious health problems, is not effective enough to justify the costs, and is pharmacologically obsolete.Arvid Carlsson has argued that fluoridation violates modern pharmacological principles and doesn't take into account individual variations in response, which can be considerable even when the dosage is fixed.