Restorative dentistry: How to avoid the class II apocalypse
When I see a quadrant of MOD composites on my schedule, I hang my head. Why, oh why, are my radiographs so clear that I saw that interproximal decay and told the patient? The Four Horsemen of the posterior composite apocalypse—proximal contour, contact area, gingival adaptation, and contact tightness—are the foes we conquer every day. I will present some tips on how to make it easier on us, our teams, and—most importantly—our patients. Full confession: I don’t hate quadrant class II composites, but when each failed composite restoration costs $292 plus patient anguish, I want to be sure I get it right the first time.
In the early 1990s, my dad wanted to experiment with that “white stuff” for occlusal fillings. In dental school, in the early 2000s, only the top students even got to consider placing a posterior composite. My dental school operative head said, “Why would you do a disservice to your patient like that and not place an amalgam?” But with my dad being in private practice, I knew I would be placing composites when I got into the real world. The trick was preparing a proper prep, as we had been taught G. V. Black’s principles of amalgam preps, and then obtaining the four attributes I mentioned previously. Some companies were experimenting with different composites to make them “amalgamlike,” while others were creating matrices that were better than flat, circumferential Tofflemire bands.
Now, for the Four Horsemen that are coming for you. Proximal contour refers to the natural curve of the interproximal tooth. You must make sure the curve is not overly convex, concave, or flat. The location of the contact area needs to be as it is in nature. If it’s too occlusal, you will get widened gingival embrasures and food traps. If it’s too gingival, you will get occlusal food traps. The contact area is usually located in the upper middle third of most teeth. Gingival adaptation is important to prevent leakage and isolation for long-term predictability, as well as to prevent overhangs, voids, and gingival col irritation. Finally, the scariest is contact tightness. I hate light contacts and food traps for both my sake and the patient’s. I had one once. It’s terrible. Contact tightness has been the most difficult part in the evolution of posterior class II composites. But thanks to the innovative contributions in matrix systems, we can conquer the impending composite apocalypse.
The three key components are the matrix band, the wedge, and the ring. Many companies provide a system, and they range in price. I am more than willing to spend a bit more if I get a better outcome. I am currently using Palodent Plus (Dentsply Sirona) and Composi-Tight 3D Fusion (Garrison Dental).
The matrix band is usually made of precurved metal that adapts to the natural curve of the tooth. It has to be thin enough to account for space to ensure contact tightness, but strong enough that it doesn’t crumple under pressure and produce concave contacts. Have a variety of heights, widths, and some matrix bands for subgingival situations on hand. Not all tooth sizes and preps are universal.
The wedge takes advantage of the stretch inherent in the tooth periodontal ligament (PDL). A strong wedge application allows us to overcome the space a matrix band takes. The wedge also allows for a strong seal with the proximal box and prevention of leakage and future recurrent decay, as well as the prevention of an overhang or void. Plastic wedges compress when inserting, expand when in place, prevent crushing of the gingiva, and have little plastic cilia to prevent them from backing out. Wooden wedges still work to create a seal and separation, and prevent fluid leakage. Not every gingival embrasure is created equal, so it is important to have a variety of sizes and shapes.
The last component of a matrix system, the ring, is where we have seen the biggest advancement. The advent of NiTi metal rings, with their inherent natural springiness, allowed for adaptation of the metal matrix and separation, but there are disadvantages. If not contoured correctly, the ring will “crunch” the metal matrix, especially in wide preps. The NiTi rings stretch out and need to be replaced often. Finally, in a quadrant full of MODs, you can’t stack the rings. However, the addition of V-shaped plastic tines, in addition to the metal rings, has made it possible to overcome these disadvantages. The tines have extra width and enable the ring to contact more of the tooth structure buccally and lingually, especially in wide preps, and their different heights accommodate the different sizes of patients’ teeth.
With improvements in matrix system materials and designs, you can rest assured that the Four Horsemen will not come for you in the Last Judgment. You can get good contact area, good contour, good gingival seal, and good tight contact predictably. Remember, the matrix system is a workhorse in your practice, so invest in a quality system so you won’t have to replace composites you just completed. With efficient, predictable matrix systems, you can fight off any enemy and look forward to conquering that quadrant of class II composites.
