When we cement crowns on natural teeth, the tendency is to slather a heaping pile of the stuff to fill up the crown and then seat it with a satisfying smoosh. The excess spills over and we clean it up before it sets.
My cementation technique
I exaggerate, of course, but there have been some studies that show a very wide range of cementation techniques and amounts of cement applied to our crowns, especially when it comes to implant crowns.
You see, cementing an implant crown should be handled very differently then cementing a crown on a natural tooth. Gingiva have weak, pseudo-attachment (some would say adherence) to implants whereas gingva firmly attach to cementum. This means that excess cement can be pushed deeper around the implant sulcus and cause all sorts of trouble. Excess cement that is left around an implant can lead to pain, bleeding, redness, and pus, a condition called peri-implant mucositis. If the cement is left to really do some damage, it can lead to these symptoms plus loss of the crestal bone, a condition called peri-implantitis. Now we’re talking about potentially losing the implant. For more on peri-implant disease, check out this post.
There are currently three popular techniques recommended specifically for cementing implant crowns. The real thought leader on this subject is our colleague, Dr. Chandur Wadhwani from the University of Washington.
(1) The Copy Abutment
Dr. Wadhwani introduced an interesting technique in 2012 that is illustrated here. Essentially, we place a spacer inside the crown, fill it with a quick-set PVS, and thus produce a copy abutment. We can then fill the crown with cement, seat it on the copy abutment, and remove the excess easily since it’s outside the mouth. Next, we quickly place the crown on the abutment intraorally before it sets.
I haven’t used this technique because I find it challenging to place a spacer (typically plumber’s tape) inside the crown. Has anyone had success with this?
(2) Vent Holes
In a recent article, Dr. Wadhwani advocates preparing two vent holes in the abutment about 180 degrees apart and also leaving the screw access hole open. This leaves space for the excess cement to flow into and can even add to the retention of the crown as there is more surface area covered by cement. Here’s a link to the article. It’s important to remember that these vent holes are placed in the abutment, not the crown.
(3) Ring Near the Margin
Personally, I like to place a ring of cement about 1-2 millimeters from the margin. I squirt the cement on a mixing pad and then carefully apply it to the crown with a microbrush. I haven’t had any problems with this technique, although I’m intrigued to use it in conjunction with vent holes to further reduce the risk of excess cement.
Here’s a video showing some of this in action.