Tips to minimize occlusal corrections
You work very hard to build the perfect occlusal surface you’re proud of, you remove the rubber dam, and… huge occlusal correction is needed. So you start correcting it, you have to grind down the fossae and marginal ridges you were so enthusiastic about and you start to feel annoyed. Your work is just being put in rubbish.
One of the most difficult challenges during functional- anatomical direct restoration of the posterior teeth is achieving correct static and dynamic occlusion. We always try to avoid the need for corrections, because it affects the anatomical build-up negatively. In this article, I am giving a few useful tips about how you can preserve the result of your hard efforts to sculpt a nice occlusal surface.
Check contacts before start.
Use a thin (12 or 20 microns) articulating paper as the very first step of your restorative protocol even prior to anesthesia. This way you can see where the contact points are, in which areas you have to be very careful during the sculpting of the final layer. You can also inform about the type of occlusion, possible crossbite, etc. You can quickly make a photo with the marks in place to record it, so you can have a look at it during the restoration as well.
Always isolate more than one tooth.
Even in cases in which I am planning to restore a single class I only, landmarks on the adjacent teeth give me guidance about position of cusps and groves, shapes, cuspal inclination, etc. To use every possible information, I (almost) always put the rubber dam on the adjacent teeth as well, sometimes on the whole quadrant even. This way it is possible to use all the information the adjacent healthy teeth can give me (if present). On top of all that, I have a better view and access to the operatory field.
Pay attention to the adjacent teeth
Anatomy of the adjacent healthy teeth can always serve you as a guide during your build up. You can watch the position and depth of fossae, height and position of cusp tips, height, posititon and morphology of marginal ridges, further small details like wear facets, etc. If the contralateral tooth is healthy, it is a further source of informations from the original form.
Many times the improper angulation of the cusp slopes can cause premature contacts after fiishing the restorations. Isolating the whole sextant lets us see the adjacent teeth,. This way we can have anatomical landmarks to help us building up the proper anatomical structures.
Know the anatomy.
The most effective tool for minimal occlusal corrections is to be familiar with the teeth you are restoring. Every tooth is individual, but they are all built around sam basic structures. This image is highlighting the characteristics of upper premolars.
The most convenient way to learn these charasteristics is to observe nature. Make pictures, impressions of natural teeth, look at them carfully and you can find the similarities. It is a good excersise to take pictures of healthy teeth and make drawings over them (right hand side image) to mark tooth outline, cusp tip positions, primary and secondary grooves. You will find that teeth of different patients have the basic characteristics in common, what is all driven by function. Once you find these common rules, it will be much easier to sculpt the correct anatomy and the need for occlusal correction will drop dramatically.
After learning anatomy, the next step is recreating it. Modeling teeth in wax is a very good excercise to become familiar with teeth shapes. This is a wax up that was done by the author in 2008.
Teeth are created perfectly functional by nature: every groove, fossa and ridge have their role in functional contacts and movements. If you know these rules, you will know how to reconstruct occlusal surfaces and minimise the need for possible corrections.
The concept of the occlusal compass was created to visualize functional movements of opposing teeth, to help understand the relationship between anatomy and function.
The occlusal compass in case of a lower molar tooth. The central green point is indicating the cusp of the antagonist tooth. The arrows show movement of antagonist cusp during different jaw movements. If you look carefully you can observe, that every fossa, primary and secondary groove is there for a reason, to allow room for opposing cusp movement and ensure an effective chewing function.
The initial situation of an easy example. The whole posterior area was isolated with the rubber dam.
The cleaned cavity. The remaining anatomical structures help a lot in sculpting the proper anatomy.
Selective etching of the enamel.
Control the size of resin increments.
Even during the layering of the dentin masses, it is important to control the amount of material were inserting at once. Besides the problem of polimerization shrinkage and stress, the incorrect size of resin can lead to incorrect size of cusps and position of grooves, which can easily result in premature contacts at the end. The same appears for the enamel layer application even more.
Avoid overfilling the cavity beyond the margins
In the experience of the author, the majority of direct composite restorations are extended beyond the margins of the cavity. As this tooth surface is not conditioned by the bonding agent per se, this area is more susceptible for discolorations and secondary decay. Furthermore, the overfills frequently cause premature contacts during static and dynamic occlusion. This problem can be difficult to control, as after the polimerisation of the bonding the cavity margin will be hard to visualize.
Schlichting et al. described a technique to avoid this, but it is difficult to perform during everyday procedures. With good magnification and some extra attention however, the limits of the cavity can be visualized and the extension of the final enamel layer can be controlled.
The finished restoration after initial polishing.
Immediately after rubber dam removal.
Occlusion check. Minimal adjustments needed, the anatomy was not influenced.
The restoration after 1 month in function.
Direct restoration of posterior teeth is a frequent treatment for the restorative dentist. This treatment option also has a few challenges, one of them is to create proper anatomic surfaces free hand.
If the clinician has the right anatomical knowledge, collects and uses all available information to his benefit, than it will be simple to recreate anatomical structures, thereby minimizing the need for occlusal corrections.