Abstract: For the selection of orthodontic appliances in clinic and the guidance of demineralizing prevention, the streptococcus was studied in attachment and cleaning ratio and ratio from brackets. In vitro, two groups of many kinds of brackets were cultivated in streptococcus culture medium for 48 h. The brackets in attachments group were dried and weighed up and in the cleaning group were churned up in puddler and weighed up. In comparison of the two groups, result displayed that the cleaning rate of stainless steel brackets was higher(the brackets made abroad were 88.29% and those made in China were 83.54%). Ceramic brackets were 80.95% and the plastic ones were 14.28%. So the stainless steel brackets are recommended to patients whose oral hygiene is not good and who live in easy-carious areas.

Key words: brackets, plaque, adhesive