Jeffrey Caso Every CEREC dentist strives for that drop-in, dead-on, no-adjustments-needed restoration. The contacts play a huge role in achieving that goal. We need a snug fit that allows floss to pass through with a snap. Anything less than that will become a food trap and will lead to an unhappy patient. Not to mention future decay and periodontal problems.
It is extremely important to set up successful contact right from the start. First, make sure the adjacent proximal surfaces that you will be building the new restoration to are smooth, even and broad. If they are not, then use your handpiece and make them ideal.
Next, imaging is so important to accurately capture and record these same surfaces. If the software cannot see them, it cannot record them and will fabricate the proximal surface. These surfaces may be right or may be wrong. The best way to tell if you captured an area is to view the preview at the imaging step and see if the area is filled in and not see-through. Surfaces that are see-through will result in fabricated data and may lead to open or tight contacts later.
Next, make sure that you powder properly. Too much powder and snow drifting will artificially bulk out the proximal surfaces. When you set up your contact it will look great on the design screen, but the contacts will be light in the mouth. That brings up another important point, which is to design the contacts in the software so that they work for you. We all practice slightly different. For me, I like my contact area wide and broad. I make them yellow with specks of green.
There is one exception to this rule and that is when I am restoring the distal-most tooth in the arch or any tooth that has just one contact. For those contacts, I make sure I have some red in them. Just specks, not an entire red wall. This allows me to push the restoration in place tightly and get some slight movement in the periodontal ligament, which allows the crown to seat with a very tight and fully closed contact. I find that if I don't do this I can end up with a light contact.
Keep in mind on these distal-most teeth that the occlusion is critical to keeping the contact closed. If you know for sure that you had a closed contact and the patient returns complaining of food impaction, you can bet there is an occlusal hit somewhere on the distal of that tooth. This drives the tooth back during mastication, bruxing, etc. and opens up that contact. Adjust it and it closes right up.
Some other points to consider are, try not to polish off your contact, support your e.max restorations well to avoid slumping in the oven and adjust a tight contact very slightly.
We can deliver a beautiful crown to a patient and be very proud of it, but if the contact is off ever so slightly that will drive the patient crazy. With e.max being so difficult to remove, we really need to be spot-on without contacts from the start. I hope this helps to refresh us all on such an important subject.
