Introduction: Research the topic "Research in caries prevention using fluoride gel". Objectives: To describe the current status permanently tooth decay early stage of 7-8 year-old students in primary school Dong Ngac A, Tu Liem, Hanoi, 2009. Methods: The study described, cross-sectional analysis of over 320 students 7-8 years of age, randomly selected from the list of East Elementary School students wonder A Hanoi. Examination to detect cavities, tooth decay early permanent normal by observation under ICDAS system and Laser fluorescence device Diagnodent 2190. Collect information on the decay rate of children with permanent pre-designed form. Results: (78.8 percent) students 7-8 years of age with permanent caries early from level D1 injury or, (48.4 percent) decay from 02, (20.3 percent) decay from the D3
DMFT index (2.21 + or - 1.52), DT (2.19 + or - 1.52), FT (0.02 + or - 0.21)
DMFS index is (2.83 + or - 2.23), DS (2.82 + or - 2.25), FS (0.06 + or - 0.48). Discussion: The difference in the decay rate found in this study is using the new criteria ICDAS system combines with Lazer fluorescence to support the diagnosis, help avoid missed more than 50 percent of the lesions pennanent tooth decay early, lead to a better appreciation of the prevalence of this disease in the community, on the basis of which the measures to prevent and treat appropriately. Conclusion: The rate of decay pennanently early stage of 7-8 year-old student at Elementary School Dong Ngac A, Tu Liem, Hanoi is very high.