Zirconia Impurity – Cause Analysis and Solution of White and Black Spots
In the production of zirconia dentures, which part of the impurity has appeared? Is it white? Or still black? Is it attached to the surface or deep inside?
From the production process, it generally appears before and after sintering, after polishing and after glazing. Zirconia and white impurities after sintering.
Phenomenon: Dots or flakes attached to the surface.
Reason: Adhesion of zirconia denture powder before sintering.
Recommendation: Use 50 micron alumina at 2.0MPa for sandblasting.
Preventive measures: First use a brush to remove dust, clean up particles with strong adhesion, and then use a pure air gun to blow away fine particles on the surface.
Phenomenon: Dots or flakes attached to the surface or deep into the zirconia 0.1~0.3mm.
Reason: The zirconia denture was not cleaned before sintering.
Suggestion: Small areas can be treated by sanding or dyeing with special colors.
Preventive measures: Use an oil-free and water-free air source to clean the zirconia dentures to ensure that the air source is pure; try to wear gloves when touching the dentures. If you do not have gloves, do not apply hand cream and keep your hands clean.
Phenomenon: Different dots or flakes and 0.1~1mm deep into zirconia
Reason: The zirconia denture was contaminated during sintering
Suggestion: Small and shallow ones can be treated by sanding or dyeing with special colors.
Preventive measures: Put the lid on the crucible for sintering; clean the zirconium beads regularly, if the color of the zirconium beads is severely yellow, it is recommended to replace them; check whether the furnace chamber is clean, whether the silicon carbide rods and silicon molybdenum rods are smooth, and whether there is peeling phenomenon; clean the furnace chamber regularly.
White impurities after zirconia polishing.
Phenomenon: White or black dots or flakes
Reason: The grinding head is too thick or too strong during grinding.
Suggestion: Use a finer sanding head for sanding
Preventive measures: choose a suitable grinding head (thinner), the speed is less than 15000 rpm, light pressure or no pressure, and the grinding direction keeps the same direction.
White impurities after zirconia glazing
Phenomenon: white or black dots or flakes
Reason: The white spots are not found in the previous process, there are impurities in the glaze, the tooth surface is not cleaned, the sintering curve is wrong, and the glaze is not completely crystallized.
Preventive measures: Clean the teeth before glazing, check whether the teeth are clean; check whether the glaze is clean; check whether the sintering curve is correct, whether the vacuum setting is wrong, mix the glaze paste with suitable viscosity, apply it evenly on the surface of the denture, and dry it in time.