In this investigation an attempt has been made to determine the relationship 
between the staining of permanent teeth by tetracycline administered during the 
period of tooth formation with the dosage of the drug and the duration of 
therapy. Of 238 subjects whose hospital records indicated ingestion of stated 
doses of tetracycline, some 49 were seen to have staining which was confirmed by 
fluorescence, and a further six had staining which did not fluoresce and hence 
could not be confirmed. A definite relationship between total dosage and 
staining and duration of administration and staining was established; the 
condition occurred with greater frequency (in more than one-third of the 
children) when the total dosage exceeded 3 g. or the duration of treatment was 
longer than 10 days. However, as staining was seen at all dosage levels, 
whatever the duration, physicians should continue to follow previous advice and 
prescribe other antibiotics where possible for children under 8 years of age or 
for women in the last trimester of pregnancy.