ABSTRACT In vivo study that was conducted to assess the degree of candida colonization on maxillary single dentures fabricated from two different denture base materials one of them was fabricated from rapid heat cured acrylic resin and the other fabricated from conventional heat cured acrylic resin modified with titanium dioxide nanoparticles. Seventeen patients with completely edentulous maxilla were randomly selected according to inclusion and exclusion criteria, each patient received two dentures made of rapid heat cured acrylic denture base and modified conventional heat cured acrylic denture base with titanium dioxide nanoparticles then candida samples were taken from the surface of oral mucosa at the crest of the ridge using sterile cotton swabs. Statistical analysis was performed using SPSS 20®1, Graph Pad Prism®2 and Microsoft Excel 20163. Data was represented as mean and standard deviation for quantitative data, Data were explored for normality by using Shapiro Wilk and Kolmogorov Smirnov normality test which revealed that all data is parametric data (P-value > 0.05). Accordingly, comparison between two groups was performed by Independent t test, while comparison between before and after was performed using Paired t -test. In this study we concluded that: addition of titanium dioxide nanoparticles will decrease candida colonization on dentures. Keywords: In vivo study, Maxillary single dentures, Acrylic resin.