Quote:
Originally Posted by PGguy
Here's another one for everybody,
What do people do about the trans spot left from the sprue? I try to sprue on the lingual if possible to hide it, but if the only place is facial and your using stain technique, I find this a pain in the butt!!
Thanks,
PGguy
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As Chris stated above, to keep it really simple, you want to always sprue off the incisal edge. For the super scientific explanation read on:
This optical phenomenon is a result of the flow characteristics of the material. The cylindrical shape of the litihium disilicate crystals promotes an alignment of the crystal structures in the direction of flow. This is kind of like logs floating down a river. The logs will always float end to end and never side to side.
This crystal alignment refracts light in a specific pattern which gives the material a brighter look when viewed laterally (more light refraction) than when viewed from the end (more light penetration). This is not a problem when spruing is accomplished from the incisal edge as detailed in their instructions for use because all the crystals are aligned along the axial surfaces. However, when sprued from the facial, the crystals will remain aligned with the sprue for a distance into the axial wall of the restoration before changing direction to align with the axial surfaces. This creates an optical illusion that there is a difference in the material at the sprue attachment site. This phenomenon will be more pronounced with thick restorations and less pronounced in thin walls where the directional change of the lithium dislicate crystals occurs almost immediately upon the material entering the wall of the restoration.