Objective To analyze the relationship between inorganic ingredien（ts Ca, P and F）concentration of plaque residues in the primary teeth and caries status，sugar exposure frequency. Methods Subjects were 93 of 3- 5 years old children living in Beijing area. According to their caries status, they were classified into two groups: Severe early childhood cari（es S- ECC）group and caries fre（e CF）group. Plaque samples were collected from subjects respectively. Ca, P and F concentration of plaque residues was measured by atomic absorption spectroscopy, spectrophotometer and fluoride electrode respectively. The information of daily sugar exposure frequency of children was obtained from a standardized questionnaire filled by their parents. The relationship between inorganic ingredients （ Ca, P and F） concentration of plaque residues and daily sugar exposure frequency was analyzed and the relationship between inorganic ingredien（ts Ca, P and F）concentration of plaque residues and caries status in the SECC group was also analyzed. Results The mean values for Ca, P and F concentration of plaque residues were lower in the S- ECC group, but the difference was not statistically significan（t P>0.05）. The daily sugar exposure frequency in the S- ECC group was higher than that in the CF group. There were no relationships between Ca, P and F concentration of plaque residues and caries stat（us dmft, dmfs）, sugar exposure frequency in the primary dentition. Conclusion Plaque residues from CF subjects did not contain a greater pool of calcium, inorganic phosphorus, and fluoride ions than that from S- ECC subjects.
