Yttria-based zirconia material (Y-TZP) widely used in dentistry, may degrade in a humid, low-temperature environment such as that in the oral cavity. The aim of this study was to compare the degradation of a new silica doped Y-TZP material with that of conventional Y-TZP by using accelerated aging tests at 200°C. The results of the accelerated tests revealed that after 50 hours of aging, the conventional Y-TZP samples had damaged surfaces that were weakened by 50 to 60%, while the silica-doped Y-TZP samples were only weakened by less than 20%. The monoclinic content of the conventional Y-TZP samples increased substantially to 62.7%, however, that of silica-doped Y-TZP samples was 18.9% after 5 hours of aging. It was concluded that a new type of silica-doped Y-TZP, created by adding a small amount of silica to Y-TZP, will be more resistant to low temperature degradation than conventional Y-TZP.