The waterBEST study is a proof-of-concept, randomized, double-masked, placebo controlled, parallel group study evaluating dental caries-preventive effects of fluoridated bottled water compared to non-fluoridated bottled water in 4-year-old children.

This is a proof-of-concept, randomized, double-masked, placebo controlled, parallel group study evaluating dental caries-preventive effects of fluoridated bottled water compared to non-fluoridated bottled water in 4-year-old children. Children will be allocated at random to receive either fluoridated or non-fluoridated sourced from two local public water systems. The water will be packaged into 5-gallon bottles and delivered to households during a 3½ year intervention period. During the intervention period, parents/guardians/caregivers will be interviewed quarterly to monitor children's general health and a dental screening will be conducted annually. Children's fingernail and toenail clippings will be collected annually and analyzed to determine the fluoride content as a biomarker of total fluoride intake. Dental caries experience, the primary endpoint, will be determined once in a dental examination conducted by a study dentist close to the time of the child's 4th birthday. For the primary aim, a least-squares, generalized linear model will estimate efficacy and its one-tailed, upper 80% confidence limit using the number of decayed, missing and filled primary tooth surfaces as the dependent variable.

Inclusion Criteria:

• The parent/guardian/caregiver understands and consents to procedures described in parental permission and consent form.
• Child is aged 2 months to 6 months at the screening visit.
• 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/guardian/caregiver at the screening visit.

Exclusion Criteria:

• The child's primary dwelling at the screening 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 four years of life. 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.
• Child has serious illness/es requiring frequent inpatient hospitalization, as reported by the parent/ guardian/caregiver at the screening visit.
• Child's birth weight was less than 1,500 g (3 pounds 5 ounces).
• Child's gestational age was less than 34 weeks.
• Child uses fluoride supplements, as reported by the parent/ guardian/caregiver at the screening visit.
• Parent/guardian/caregiver states at the screening visit the child will initiate fluoride supplementation before the child's 4th birthday
• The parent/ guardian/caregiver anticipates that the child will move to an address more than 30 miles from Kinston, NC before the child's 4th birthday.
• 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.

Masking will be managed by the a Data Management System which will execute three tasks:

1. Study participants' treatment group allocation will be stored in a dataset accessible only to the masked data manager
2. A separate dataset will record unique identification codes that will be affixed as labels to 5-gallon bottles of water; the same dataset will also record the public water supply used to fill the bottle (New Bern or North Lenoir). After the barcode label is affixed, the processing slip indicating the bottle's source of water (New Bern or North Lenoir), will be removed, thereby masking the contents.
3. When new water bottles are to be delivered to a study participant's dwelling, the Data Management System will execute a bottle allocation routine that will retrieve the study participant's study group assignment and select from the supply of masked bottles the necessary number of masked bottles that conform with the study participant's treatment group assignment.