The following is an excerpt from my e-book, The TMJ and Occlusal Adjustment, which is available for immediate download. The book tells the story of the occasional patient who has a temporo-mandibular disorder (TMD) that we can clearly link to an occlusal problem. This specific disease, also known as occlusal-muscle disorder, can be effectively treated in your office as long as you know the fundamentals. I review the essential anatomy, function, and dysfunction of the TMJ and share my philosophy of occlusion over the course of 40 pages.
In this excerpt we examine the occlusal marks left by articulating paper on posterior teeth. What the heck should those dots look like?
Posterior Harmony
There are two popular theories of posterior occlusion that I will discuss.
Here are a maxillary right first molar and second bicuspid:
Figure 11: Maxillary teeth without occlusal marks.
My first study of occlusion was a philosophy known as tricuspidization. The theory is that the most stable system for teeth is one in which three surfaces around the cusp tips occlude with the opposing teeth. The cusp tips themselves to not occlude at all. This results in a lot of dots left by articulating paper.
Figure 12: Typical marks for tricuspidization.
As you might imagine, this is not a simple occlusal philosophy. There are dentists that will defend it to the death and have achieved great success with it for their patients. However I believe it is very challenging to create and maintain this occlusal scheme. This is especially true when we consider a popular alternative: cusp-fossa occlusion.
Cusp-fossa occlusion is the occlusal philosophy adopted by many leading dentists, including The Dawson Academy and The Pankey Institute. It is successful, simple to understand and easy to equilibrate.
Instead of the marks left by articulating paper representing contacts around a cusp, these dots represent the cusp tips themselves. As we know, the supporting cusps are the maxillary palatal cusps and the mandibular buccal cusps. So in our example we’d expect to see a mark on each of the three cusp tips:
Figure 13: Marks on the maxillary palatal cusps.
Of course, there will also be marks left by the supporting cusps of the opposing teeth, in this case, the mandibular buccal cusps. Supporting cusps occlude in the opposing teeth in one of three areas: the central fossa, the mesial marginal ridge, or the distal marginal ridge.
Figure 14: Marks left by the mandibular supporting cusps.
So when a patient bites down on articulating paper, we should only see marks on the supporting cusps and the marks left by the opposing teeth’s supporting cusps. Combining both Figures 13 and 14, we see what cusp-fossa occlusion should look like:
Figure 15: Cusp-fossa occlusion, occlusal view.
Figure 16: Cusp-fossa occlusion, sagittal view
I think you’ll agree that cusp-fossa is much easier to visualize and equilibrate than tricuspidization. Just to drive the point home, here’s a picture of the two philosophies superimposed:
Figure 17: Comparison of tricuspidization (red) and cusp-fossa (black). Note that the red marks form a tripod around the black marks representing the cusp tips or marks left by opposing cusp tips.
This concludes our excerpt. If you’re keen to learn more, check out The TMJ and Occlusal Adjustment on this site.