Abstract : Aim: The present study was done to evaluate and compare streptococcus mutans and sanguinis bacterial count on ceramo-metallic crowns and monolithic zirconia ceramic crowns at zero and 90 days follow up period. Materials and methods: Twenty healthy patients were chosen according to inclusion and exclusion criteria's and randomly distributed into two groups (n=10) according to material of the crown. A streptococcus mutans and sanguinis bacterial count (CFU/ml) were collected at zero- and 90-days interval from plaque, salivary swab and salivary collection samples. Results: No significant difference between the two groups except S. sanginus was significantly higher in plaque sample of zirconia crowns after 90 days follow up. Conclusions: Physical nature of bacteria may affect their adherence as Streptococcus sanguinis showed higher count on zirconia crowns than ceramo-metallic crowns after 90 days of follow up.