Introduction: Nanomaterials are mainly used in ceramics, resins, and metals, providing a huge space for the improvement and innovation of dental materials. Nanoceramic materials have a small grain size, and a greatly reduced inherent porosity of materials. Aim: This study aims to do an evaluation and comparison of the dimensional changes and teeth movement of acrylic resin maxillary complete dentures reinforced with silica dioxide and zirconia nanoparticles before and after thermocycling. Methods: In vitro study using a special software to measure denture adaptation and teeth movement in twenty maxillary dentures , ten of them reinforced with zircon oxide nanoparticles and ten with silica dioxide nanoparticles before and after 5000 cycle of thermocycling process at temperarture ranges from 5 to 55o C. Results:Regarding the adaptation, silica showed a significantly more adaptation (130%) as compared to zirconia (932.4%) which showed less adapatation , Regarding teeth movement silica revealed a significantly lower movement (0.019mm) as compared to zirconia which showed (0.035mm). Conclusion: Within the limitations of this study, it could be concluded that, There is a change in teeth position in Zro and SiO2 reinforced maxillary dentures before and after thermocycling but teeth movement happened in SiO2 reinforced maxillary dentures is less than the changes in Zro reinforced maxillary dentures.Regarding denture adaptation of both groups before and after thermocycling, there a changes in denture adaptation happened in Zro reinforced denture bases before and after thermocycling, and changes in SiO2 reinforced denture bases before and after thermocycling according to paired samples t-test. Regarding comparison between both groups before and after thermocycling there is a difference in denture base adaptation, but silica group showed a more adaptation as compared to zirconia group which showed less adaptation.