to find the clinical relation between caries experience in primary teeth and first permanent molar in mixed dentition stage using def index for primary teeth , DMF index for first permanent molars and to find the clinical relation between caries prevalence in the selected children in relation with other associated factors such as age, sex tooth brushing frequency, dietary habits and mother's attitude toward child's oral health.

the problem for which the study held is lacking of data about relation between prevalence of dental caries in primary teeth and first permanent molar of the same child in mixed dentition stage, incidence of dental caries is influenced by number of risk factors such as age, sex dietary and oral hygiene habits identifying high risk individuals helps development of systemic approaches for preventive oral care programs world wide Dental caries is the major public health problem in most high income countries, affecting 60-90%of school children and the vast majority of adults. it also the most prevalent oral disease in several Asian and Latin American countries Although for the moment it appears to be less common and less severe in the greater part of Africa, the WHO report 2003 anticipates that in light of changing living conditions and dietary habits, the incidence of dental caries will increase in many of that continent's low income countries(WHO,2006)

Inclusion Criteria:

• egyptian children
• children without systemic disease syndromes and disabilities
• first permanent molars fully erupted and in occlusion
• acceptance of the children's parents to participate in the study

Exclusion Criteria:

• any of first permanent molars aren't fully erupted or not in occlusion
• children suffering from any systematic disease that affect teeth development

children are selected from from children attending the diagnosis clinic of Department of pediatric dentistry and Dental public health