The effect of pure nano- metakaolinite powder reinforced type III dental stone on some mechanical and surface properties

Objective Although type III gypsum dental stones are used for the fabrication of high-strength models in dental applications, it has reported to have drawbacks like limited compressive and diametral tensile strength, brittleness, dimensional changes, and porosity. Method This study investigates the effect of nano- metakaolinite powder reinforcing type III dental stone to enhance mechanical and surface characteristics. Type III dental stone (G0 as a control group) was reinforced by various weight percentages (1%, 3%, and 5%) of pure kaolinite nanofiller (G1-G3), respectively. A total of 180 samples were fabricated. Eighty cylindrical samples were fabricated for mechanical testing (n = 40). Eighty disc-shaped samples were fabricated for surface analysis (n = 40). Each testing group was further subdivided into four subgroups according to the metakaolinite reinforcement ratio (n = 10). An additional twenty disc-shaped samples were fabricated for microstructural and elemental evaluation (n = 5). For the controlled group, the stone was mixed according to the manufacturer’s instructions with distilled water at 23 °C where as for the experimental groups, the pure nano kaolinite powder was first dehydroxylated to become nano metakaolinite (NMK), then mixed with the stone powder. All mixtures were poured in customized plastic molds and kept in the incubator for 72 hours before the testing procedure. Results and Conclusions The results reported significant increase in both compressive strength (43.25 MPa), and diametral tensile strength (9.83 MPa) of the G2 group (3% NMK) when compared with the control group (G0), with significant decrease in compressive strength and diametral tensile strength related to the G3 group (5% NMK) when compared to G2 group. The G2 group recorded the highest values for surface hardness (33.02 VHN) and surface roughness (1.36 μm). The dental stone matrix was effectively reinforced by the 3% NMK group.