Hey everyone. I'm a doctor in a big group practice with an internal lab, and I'm the liaison between the doctors and the lab. I was hoping you could help me out with this. Our lab mills zirconia crowns, the after they're sintered, they trim back the margins manually. Whenever there's a margin issue, my doctors say that the error is caused by the manual trimming, and that other labs don't do that. Our lab says that of course everyone does that - that's the only way it can be done. So who's right? Does everyone trim back their margins manually, and does that tend to be a big source of margin error?
. That's where the real talent comes into play. Blending in the margin, maintaining at least 2 mm of blend of contour with emergence profile of underlying preparation. "Ring around the collar" (Tanaka) impressions give you that Really required anatomic reference to blend with.
Simply a term he uses for a succesful full margin capture impression. Also picks up anatomy of the tooth structure below the margin to assist in guiding emergence profile of the restoration to proper form. Good tissue management is essential to achieve this result.