Introduction:

The study planned is an analysis of existing data within the Avon Longitudinal Study of Parents and Children (ALSPAC). The aim is to examine the growth rates of children with and without dental caries from birth until the age of five years.

The hypothesis-generating observation that stimulated the proposed study was that weight and body mass index appeared to increase following removal of diseased teeth (1). The proposed study is required because in the original observational study it was not possible, for ethical reasons, to have a control group i.e. the ethical committee found it unacceptable to observe disease in children's mouths without offering a treatment service to them. Since funding to provide such a service was unavailable the study had to utilize population data for the reference group. The best reference population data available was the UK 90 growth reference data. However, the findings of the study have such profound policy implications that it is important to explore the hypothesis of a caries/growth association with high quality data such as ALSPACs as the weaknesses in the former study cast doubt upon the crucially important findings.

Method:

The growth measurements of the children will be converted to percentiles and SD scores. L grow software will then be used to calculate longitudinal norms and to judge the growth pattern of the participants. The average velocity of growth calculated from their height, weight and body mass index at 4, 8, 12 monthly and 6 monthly thereafter until the age of five for each individual will be correlated with their measured dmfts. The children's gender, maternal and partner social class, maternal education, maternal age, maternal and partner height, breast feeding, ethnic group on growth and their effect on caries rates will also be determined.

Thus the relationship between growth and dental caries can be established as well as the extent to which poor oral health is associated with either abnormal body mass index or acceleration/ deceleration in growth.

Sample Size: the number of children will be between 300 (with complete data) and 800 with data on some measurement occasions

Percentile curves on growth charts are spaced 0.67 of a SD apart. The sample size is therefore calculated for a change in SD score of 0.67 units (one percentile space) assuming a correlation between the SD measure on two occasions of 0.80.

A sample size of 20 in each of two groups would have 96% power to detect a difference in means of 0.67 assuming the common standard deviation was 0.63 using a two group t test with two sided significance. Thus in order to allow analysis and comparison of up to 5 sub groups, a sample size of 200 is suggested.

sample. (1) Childhood Growth and Dental Caries. Mohammadi M and Kay E Comm Dent Hlth (in press)