In the last two days I have heard some really wonderful presentations on implant dentistry. From treatment planning to cementation I have lots of new ideas to take back to my patients that I will share in the next few blog posts. One such idea was addressed cementation of the final crown over an implant abutment. One of the reasons we see changes in the soft tissue and bony topography after placing an implant restoration is cement remaining below the restoration margin. This cement situated between the abutment and the junctional epithelium acts as an irritant. The results can range from gingival irritation to osseous recontouring around the fixture.
One of the inherent challenges of cementing a final restoration over an implant abutment is cleaning off the excess cement. We do have special plastic hygiene instruments designed not to damage the head of the fixture or abutment. Unfortunately, they can be ineffective when trying to remove fully set cements. Several of the lecturers presented the concept of placing a single cord prior to cementation as a way to facilitate cementation. Utilize cord that is not impregnated with and vasoconstrictors. The cord should be placed carefully positioning the top just below the crown margin on the abutment. Heavy pressure will place the cord far to deep, which makes it ineffective int his technique and difficult to retrieve.Trim the ends of the cord so that they just meet in the sulcus and no tail is left hanging out. This prevents a gap from being present where the cement can sneak down deeper into the sulcus.
With the cord in place follow your cementation protocol. Clean the cement thoroughly with the cord in place. When ready tease one end up and pull the cord up toward and out of the sulcus. When we seat restorations, we aim to have enough cement so that some is extruded at the margins. The pressure from seating will drive the cement between the abutment and the tissue into the sulcus. The cord acts as a barrier and drives the excess cement up out of the sulcus where we can see it and easily remove it. When you remove the cord you will see a quantity of cement that has set on the cord. The last step is to make sure to remove any thin layer of cement that was just where the top of the cord touched the abutment just below the crown margin. Ideally, this should be just below the free gingival margin, but we will look at margin placement and abutment design in another blog.