Inclusion Criteria:  UCSF Pediatric Dental Clinic patients New patient exam or recall exams Caregiver and child speak English, Spanish or Chinese Ages 5-10 years San Francisco residents Non-acutely ill (healthy enough to attend school, no fever and no systemic conditions)  Exclusion Criteria:  Child and caregiver do not speak English, Spanish or Chinese Not a San Francisco resident Under age 5 years Over age 10 years Child unwilling to accept randomized drink assignment Child unable or unwilling to drink water or apple juice Child unable or unwilling to give saliva Child is presenting to the dental clinic for an operative procedure Acute illness, fever, infection or condition that would prevent the child from attending school No remaining space in study group (weight-specific recruitment is complete).