Objective: to investigate glass infiltrating rates (depth/time) within dental CAD/CAM alumina at different temperatures. Methods: micron α-alumina powder was prepared with cold isostastic pressure at 250 MPa and sintered at 1450°C. The presintered alumina specimens were then infiltrated with special glass at 1150°C, 1200°C and 1250 °C. The infiltrating depths and time to form the infiltrate at the different temperatures were evaluated. Results: As the infiltrating temperature increased, the viscosity of the infiltrating glass decreased, and the infiltrating depth increased. A 1 mm infiltration depth into the presintered alumina at 1150°C, 1200°C and 1250°C required 95 min, 22 min and 8 min, respectively. Conclusion: An optimal infiltrating time required to reach a suitable infiltration depth into the presintered alumina was observed at 1200°C, an important finding for clinical applications at this commonly used furnace temperature.