: This study was carried out to detect the distribution of Streptococcus mutans with dental caries in Iraqi's patient samples. Out of 100 patient's samples only (22) with age (3-17) years old were found to be effected with Streptococcus mutans. DNA was extracted amplified by Gradient PCR and then sequenced. vicR was showed highly conserved with no mutation while vicK showed that these were silent mutation and four isolates have missense mutation from eight isolate. Material & Method : In this

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... udy, 22 from clinical S. mutans strains were isolated from caries-children to sequence the vicR, vicK and 16s rRNA genes. Genomic DNA was extracted from S. mutans strains and amplified using Gradient PCR. The PCR products were purified and then sequenced. Result : The molecular study include vicR, vicK and 16S rRNA, genes by Gradient PCR. The result of sequencing appear that no mutation in vicR genes, although in 16S rRNA present transion and tranvesion mutation . Finally the sequencing of vicK gene appear silent mutation and four isolates have missense mutation from eight Conclusion the result of molecular study of vicR gene were appear no mutation in all isolates while 16S rRNA although have transition and transvertion mutation, the Sequence of vicK gene that note more of mutation was silent mutation but some of them was missense mutation.