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Lab talk, the good, the bad, and the ugly
Zirconium
Question on translucency measurements on zirconia pucks and finding the correct puck
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<blockquote data-quote="richgreen" data-source="post: 336830" data-attributes="member: 1232"><p>Your Majesty,</p><p>Translucency is a function of grain shape, grain size, and sintering temperature. Manufacturers typically use a specific thickness sample to determine translucency. As I am sure you have observed, thicker crowns may not be as translucent as thinner crowns. So a 50% translucent crown that is say 6mm on buccal surface (implant crown) will not look as translucent as a 50% 1.5mm thick crown. So crown thickness plays a part.</p><p>Lets talk about 3y-5y zirconia. The 3y zirconia is a highly tetragonal zirconia. 3 mol percent yttria is used to stabilize the zirconia in its tetragonal phase. Due to the shape of the grains there is a considerable amount of light scattering, resulting in an inherently lower translucency material. 5y zirconia has more cubic zirconia in the formula, which requires more yttria to stabilize it in that phase. Because cubic zirconia refers to the shape of the grain e.g. cubic, its shape allows for more transmission of light and less scattering.</p><p>To determine the "perfect" zirconia for your needs you may have to obtain 2-3 sample disks to mill units from and compare the out comes post sinter. Your sintering oven may treat the zirconia in a slightly different fashion from the manufactures oven. Be sure to run any test samples at the manufacturers guidelines. You may still need to adjust but its a good starting point. Rich</p></blockquote><p></p>
[QUOTE="richgreen, post: 336830, member: 1232"] Your Majesty, Translucency is a function of grain shape, grain size, and sintering temperature. Manufacturers typically use a specific thickness sample to determine translucency. As I am sure you have observed, thicker crowns may not be as translucent as thinner crowns. So a 50% translucent crown that is say 6mm on buccal surface (implant crown) will not look as translucent as a 50% 1.5mm thick crown. So crown thickness plays a part. Lets talk about 3y-5y zirconia. The 3y zirconia is a highly tetragonal zirconia. 3 mol percent yttria is used to stabilize the zirconia in its tetragonal phase. Due to the shape of the grains there is a considerable amount of light scattering, resulting in an inherently lower translucency material. 5y zirconia has more cubic zirconia in the formula, which requires more yttria to stabilize it in that phase. Because cubic zirconia refers to the shape of the grain e.g. cubic, its shape allows for more transmission of light and less scattering. To determine the "perfect" zirconia for your needs you may have to obtain 2-3 sample disks to mill units from and compare the out comes post sinter. Your sintering oven may treat the zirconia in a slightly different fashion from the manufactures oven. Be sure to run any test samples at the manufacturers guidelines. You may still need to adjust but its a good starting point. Rich [/QUOTE]
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Lab talk, the good, the bad, and the ugly
Zirconium
Question on translucency measurements on zirconia pucks and finding the correct puck
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