You’re hoping to cement a full-coverage crown for a patient and it’s going well so far. The margins are closed, the interproximal contacts are flossing nicely, and the esthetics are looking pretty. Finally it’s time to check the occlusion. You have the patient bite down on articulating paper and you see a bunch of dots.
The patient says the crown feels a little high, so you carefully grind away until the patient is comfortable. Are we ready to cement? Not yet. We need to take a closer look at those other dots to make sure they aren’t going to cause us trouble down the line. There are good dots and bad dots, and we need to go “bad dot hunting.”
Here are the three kinds of bad dots to look out for:
(1) The Outliers
Let’s say your patient has a normal Class I occlusion and there are no cross bites or other unusual jaw and tooth relationships. If you’re inserting a maxillary first molar crown, there should not be any occlusal marks on the buccal cusps when the patient bites. Those centric stops should be on the palatal cusps for a maxillary tooth, of course. Conversely, you shouldn’t see dots on lingual cusps of mandibular restorations.
Although cusp-fossa occlusion is relatively easy to set up for a patient, I don’t do full mouth equlibrations for patients who are only getting a single new crown. Or a new bridge, for that matter. For more on my philosophy on when to equilibrate, check out this article here.
But I digress. So the cusp-fossa picture is a useful guide, but unless you’ve set up the whole mouth to occlude in that fashion, we must think outside the box. Just look at the dots on the other teeth in the quadrant and compare to the dots on your new crown. Any major differences? You’ll probably want to get rid of those on your new crown.
Dots on the buccal cusps of a crown on a maxilalry first molar. You can clearly see that these marks are not present on the adjacent teeth.
(2) Unsupported Porcelain
Similar story to the point made above. Are we inserting a non-monolithic crown? Monolithic crowns are made from a solid piece of material, like gold, lithium disilicate, or zirconia. Non-monolithic crowns have a strong core of material that adapts to the die and then is veneered with a nicer-looking layer of material, usually porcelain. Your standard porcelain-fused-to-metal (PFM) crown is a common example of a non-monolithic crown.
For non-monolithic crowns, we should examine the design of the coping in relation to the overlaying porcelain. If there is an area of veneering porcelain that is not directly supported underneath by the core, then we don’t want any occlusal marks in this spot. This could lead to porcelain fracture.
(3) Symptoms Develop
Articulating paper is good for revealing the location of dots, but it is lousy at showing us the intensity of the bite. Even if you see a nice, balanced occlusion in the whole quadrant, it’s possible that the bite is just a little bit heavier on your new crown. You may not pick that up just by looking at the dots.
If a patient develops cold sensitivity and/or throbbing on a tooth that just received a new restoration, I almost always adjust the occlusion first. Even if all the dots are where they’re supposed to be, I will at least attempt to lighten their impact.
For more information about the TMJ and occlusion, check out my e-book, “The TMJ and Occlusal Adjustment”