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Analysis of YY/T 0631-2008 Test Method for Color Stability of Dental Materials
Scope: This standard specifies a method for the determination of the color stability of dental materials after exposure to water immersion light. Test device: Xenon lamp with medium pressure light source, color temperature between 5000K and 10000K. Measured according to GB16422.2, the illuminance in the sample should reach 150000lx±15000lx. Other light sources equivalent to xenon lamps may also be used. The luminous intensity of xenon lamp and UV filter will change due to aging after 1500 hours of use, and should be replaced in time. Get a suitable illuminometer to measure the illuminance and adjust the contrast accordingly. The UV filter is made of optical glass (borosilicate glass), the transmittance of light waves below 300nm should be less than 1%, and the transmittance of light waves above 270nm should be greater than 90%. Test chamber circulating water bath distilled water or deionized water, the temperature is maintained at (37±5) ℃, the water surface is on the sample (10±5) mm, the sample is placed parallel to the bottom of the testing-equipment' target='_blank'>test chamber. Specimen holders are made of opaque material, preferably metal, and can be used to hold specimens up to 50mm in diameter. Figure 1 shows a suitable specimen holder. Test steps: ① Sample preparation Each dental material standard control sample size, sample preparation method and conditions and the products of the control sample are specified. These standards should be used in conjunction with this standard. ②Half of the irradiated test specimen is clamped with specimen clamps (see detailed standard), or wrapped with tin or aluminum foil. For dental specimens, wrap half of the tooth vestibule with tin or aluminum foil parallel to the long axis of the tooth. Install the UV filter, put the sample into a water bath, and irradiate the sample with a xenon lamp (24±1) h. Take care to avoid shadows on the specimen. Evaluation - Color Comparison: Three examiners with normal color vision, orally observe any difference in color between the irradiated half of the sample and the unirradiated half and from the unirradiated sample. Examiners with normal color vision should be checked and verified by a doctor or other appropriately trained person. Colorless vision correction glasses may be worn. The comparison shall be made under bright diffused sunlight that is not in direct sunlight in the north direction, or under a xenon lamp with an illuminance of 1000 lx~2000 lx or an equivalent lamp conforming to CIED65 without any obvious color reflection. The disk-shaped sample is placed against a diffuse white background with a reflectivity of about 90%. The background is the same size as the disc, and the surrounding reflectivity is (30±5)% diffuse gray background around. Tooth-shaped sample, with reflectivity (30±5)% diffuse gray background. Let three observers observe for no more than 2 s at a distance of 200 mm to 300 mm from the sample. The comparison results of the three observers were recorded separately. If the observation conclusion is in dispute, the majority result shall prevail.
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