Trung, N.T., Loan, H.K., Duy, H.B. and Hạnh, K.T.H. 2021. Prevalence of gingivitis and sensitivity, specificity of dental imaging with smartphone in diagnosis gingivitis among 15 - year - old students in Hung Yen . Journal of Medical Research. 143, 7 (Nov. 2021), 86-93. DOI:https://doi.org/10.52852/tcncyh.v143i7.652.