Cement Retained Implant Restorations
It’s Monday morning and you have to cement an implant crown. Soon the patient gets to go home with a new tooth in his mouth that is worth a lot of money. Both the dentist and the patient are happy that the work will be completed after many months or years of waiting. However, if the protocol of cementing a crown is not very meticulous, it can lead to disastrous results in as little as 4 months or as long as 10 years.
Is there a standard protocol for cementing implant crowns? No, there isn’t, unfortunately. Everybody does it differently. Some people fill the crown all the way up with cement, others paint it with a brush inside the crown, while very few place a rim of cement around the margin of the crown. It seems the least amount of cement is expressed under the gingival tissues with the last method.
Cement retained implant crowns fail due to cement left underneath the gum line most of the time. It’s important to probe the implants and clean the cement whenever you find it. If there is a saucer-like appearance on the PA, take a BW or a PA at a different angulation for a different perspective and hopefully you will see the cement. The most radiopaque cements are Tempbond original and Tempbond NE because they contain zinc. You want to see on the xray if the cement got expressed under the gingival tissues. Durelon is a zinc-phosphate cement, but it deteriorates titanium, so it should not be used on implant crowns.
Here are some advices I found useful. Have the margin of the abutment supragingival and place a rubber dam when you have to cement an implant crown. Use only 6 mm3 of cement ( the size of a No.6 round bur) around the crown margin so you don’t get a lot of cement under the gum line.