A large number of liquid oral medicines contain sugars and there is concern for the dental health of children requiring this medication long-term for chronic medical problems. Ninety-four chronically sick children aged 2-17 years taking sugar-based or sugar-free liquid oral medication for 1 year or more, and their 92 siblings were dentally examined. The medical problems of the sick children included epilepsy, cystic fibrosis, chronic renal failure, asthma, recurrent urinary tract infections, cardiac disease and chronic constipation. Ordinal logistic regression analysis compared differences between sick children and their healthy siblings and showed the only significant confounding factors related to dental health to be age (for dmfs p = 0.013, DMFS p < 0.001) and exposure to fluoridation (for DMFS p = 0.0097, DFS (approximal) p = 0.013). Children taking long-term liquid oral medicines had significantly more caries of deciduous anterior teeth than their siblings (p = 0.046).