Table 1 Inclusion and exclusion criteria

The child’s primary dwelling is in Lenoir County, NC (the primary target population) or one of three neighboring counties (Wayne, Craven, and Pitt).

Child has a serious illness/es requiring frequent inpatient hospitalization, as reported by the parent at the screening visit.

The child’s parent understands and consents to procedures described in the parental permission and consent form.

Child’s birth weight was less than 1500 g (3 pounds 5 ounces).

Child is aged 2 months to 6 months at the screening visit.

Child’s gestational age was less than 34 weeks.

Child either drinks water (either plain water or water mixed with something) or is expected to drink water by their first birthday, as reported by the parent at the screening visit.

Child uses fluoride supplements, as reported by the parent at the screening visit.

The child’s primary dwelling at the enrollment visit has tap water that contains > 0.60 mg/L F and the parent/guardian/caregiver expresses a preference that the child drink tap water, not bottled water, for the child’s first 4 years of life. Fluoride concentration of a sample of the dwelling’s tap water is measured at Dr. Godebo’s laboratory using the Ion Selective Electrode method. For children who live at more than one dwelling, the primary dwelling is defined as the one at which they usually sleep at least four nights per week.

Parent states at the screening visit the child will initiate fluoride supplementation before the child’s 4th birthday.

The parent anticipates that, before the child’s 4th birthday, the child will move to an address more than 30 miles from their address at the time of enrollment.

The investigators determine that a child living at the same primary dwelling has already been enrolled in the study. (This means that if two or more children fulfilling the inclusion criteria live at the primary dwelling, the parent will be asked to select one such child to be the study participant.)

Anything that, in the opinion of the principal investigator, would place the participant at increased risk or preclude the participant’s full compliance with or completion of the study.