BB#1 Seating a Crown

One of the most important but often ignored skill is proper seating of a crown. In dental school, we had this old lady, I cannot remember her name, but she was one of those loyal workers who showed up every day at the clinic because she had a mission. I think she had been doing it for 50 years or so, but her job was to help us seat a crown.
I think I can recite what she said almost verbatim. At the time we were using Zinc phosphate cement that requires dissipation of the heat of mixing vs in one big blob, so she would carefully get the cement out, on a "chilled glass slab" and carefully divide it up into "nine exact proportions" and then proceded to show us how, for each of the 30 crowns I did, how to properly mix the cement, never deviating the order or tone of the words. We did all we could to trip her up by asking questions during the "presentation" and she deftly diverted our questions, and always got back right on topic.
"now first, use this pledget of cotton with hydrogen peroxide to thoroughly clean the tooth preparation. one coat, here is another and finally a third time to assure the cleanliness of the preparation "(and stop the bleeding in the sulcus from our "gingival curettage preparation of the day)
"Now, we will CAREFULLY incorporate each segment of the cement into the full liquid content like this, being careful to dissipate the heat of mixing all over the chilled glass slab we have here"
(as we are getting nervous it is taking so long, and muttering things like, just get it over, ma'am, etc) she points out to us that by doing what she is doing, she can safely and confidently be mixing the 8th and 9th segment of the divided powder knowing it will not prematurely set, since she had carefully dissipated all heat each and every time she picked up a new segment of powder to "incorporate" into the "entire mixed mass", etc

so, I got into practice and the doc I worked with immediately, of course, told me that was all hogwash and I could just use "Duralon" and besides it stuck to gold better and soothed the tooth rather than creating heat on setting.

then the glass ionomers were the newest and greatest invention (does anyone remember protech cem? I think I ended up replacing about 30 of those crowns before I wised up). After just one more crown that I cut off and replaced because the patients post operative sensitivity was so hard to fix, I finally figured it out (we as a profession) that I was drying the teeth too much and there needed to be moisture during setting, or it would always be sensitive.
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After I figured that out, I no longer had problems with this new "miracle" cement that "leached fluoride" and strengthened the tooth, then they came out with the resin ionomers.

Maybe I should have stuck to that memorized technique of the old lady. I NEVER had post op sensitivity when we did that....
Anyway, here we are where Resin Ionomer is the standard and, often with all ceramic crowns, all resin cement where we (gasp!) place acid RIGHT ON THE TOOTH! no dycal! anyway, the principles now are pretty consistent.
We have the new "self etching" cements that have that same feature that if you get the tooth too desicated, the patient will predictably have post op sensitivity (probably due to hydrolic pressure created at the dentin tubule interface where it is chronically dehydrated and creates a negative pressure)
All I am sure of is that I do not want to get any of my vital crowns too dry and make sure there is a mist of moisture at seating to allow enough water for the glass ionomer setting reaction. I also use a self etching bond and primer (currently all in one by Kerr) to increase the strength of the cement.


More later, just setting up the topics now.