Background and Objective: Thermoplastic resins and co-polymer have many advantages over conventional powder and liquid resin system. Thermoplastic resins have to some extend a predictable long-term performance. They are stable, exhibit high creep resistance, high endurance, as well as excellent wear characteristcis and solvent resistance denture plaque serves as a source of infection oral material available for aspiration particularly in persons with limited salivary flow.Materials and Methods:For this study twenty completely edentulous patient were divided into two equal groups the first group received conventional denture and the second received flexible denture a comparative study for microbial evaluation was done in order to detect the amount of plaque accumulation between the two groups.Results: it is founded that the amount of plaque accumulation on bre-crystal flexible denture is less than that is found on conventional denture, at which after one mouth the mean log10 CFU value were 3.53 with SD 0.13 for conventional denture, while for bre-crystal the mean log10 CFU value were 3.22 with SD 0.10 Conclusion: Bre-crystal flexible denture base material is much better when compared to conventional denture base material in terms of reduced plaque accumulation in patients wearing complete denture.