Study aim: Determination the effect of metanolic green tea، green coffee extract and chlorhexidine on Streptococcus mutans in preschool children with early childhood caries by the PCR Design: In this clinical trial study, there will be 90 children aged 4-6 who will be matched for demographic data. Children are randomly divided into 3 groups of 30 people and assigned a code to each participants. -------------------------------------------------------------------------------- Settings and conduct: ّFirst explain aims to parents, thenwritten informed consent is taken. A questionnaire including the demographic data of the child (age, sex, history of drug use, history of systemic disease, etc.) is also completed.Then, how to observe oral hygiene and brushing explain to all parents and wanted brush without toothpaste to their children for 2 days.During study, dont use gums containing Xylitol and any type of mouthwashes containing chlorhexidine and flouride. Upon completion of the two-day period, Which is considered as a washout period, children are randomly divided into 3 groups of 30 people. After taking saliva sample,too determining Streptococcus mutans, transfer samples to labrator Participants/Inclusion and exclusion criteria: The entering criteria including children without any sysytemic disease and during the past month dont take antibiotic and topical flouride and dont have any orthodontic appliance. dont take gums containing Xylitol and any mouthmoush or gel containing flouride at least 3 weeks before study, dont have any soft tissue lesion in their mouth and do not have active and severe periodontal disease. Intervention groups: Chlorhexidine, Green Tea and Green Coffee Main outcome variables: Streptococcus mutans