Turning the Tables on Recurrent Caries

Greene Vardiman Black would be having a heyday right now. As all dentists know, Dr Black developed the first classification system for dental caries as well as the initial idea behind preparation designs.

Although dentistry is a huge amount of science with a dab of art thrown in for good measure, it needs to have standards. Well-known and universally taught standards are what helps differentiate a healthcare profession. Standards also help us provide the best possible care and give us a method to hold each other accountable.

The reason I think Dr Black would be thrilled with practicing today is because we are now in a phase where a lot of the procedures and prep designs that he created need to be updated. It’s interesting to review textbooks of operative dentistry and see how procedures and preparation designs were actually dictated by a combination of anatomy, but also the limitations of the materials of the day. When composites evolved to allow placement in posterior teeth, preparations were routinely performed using the preparation forms that doctors had learned in their training.

However, those preparation forms had been created and designed years earlier by considering the limitations of the restorative materials available. Amalgam, being the only restorative material available (other than gold) forced doctors to remove significant amounts of tooth structure to compensate for its physical properties.

There was another recommended rule from the early days of dentistry, which was that of “extension for prevention.” At the time, the prevailing thought was to prep into and remove remaining pits and fissures. The idea was that, by incorporating them into the preparation and hence the restoration, the doctor removed areas that could be sources of breakdown in the future. Since amalgam did not decay, the thought went, it was best to place it into areas that were susceptible to future decay.

The fallacy in that reasoning became apparent with the introduction of local anesthetic and fluoridation. Before anesthesia, dentistry was such a traumatic experience that doctors learned extension for prevention because the chance of getting someone to return for more treatment on the same tooth was practically nil. If a doctor got a chance to restore a tooth, it became critical to do everything possible to prevent breakdown in the future. The breakdown was also much more common before community fluoridation measures were put into effect. Stronger enamel meant less need for extension for prevention.

Novocaine was first synthesized in 1905, (Lidocaine was not discovered until 1948) and it is important to remember that local anesthesia did not gain widespread acceptance right away. Dr Black turned 70 the year novocaine was created and he published his book on operative dentistry in 1908, which means most, if not all, of his preparation rules, were created before patients were routinely receiving anesthesia. Dr Black passed away in 1915.

A Breakthrough

When the true bonded composite restoration was discovered, restorative dentistry changed dramatically. Suddenly materials could be “stuck” to enamel and dentin. As composite technology evolved and improved, preparation design evolved and improved along with it.

Once the evolution progressed to composites that could be placed reliably and long-term in posterior teeth, many began to change their preparation designs to match the changing materials. A material that chemically adhered to teeth did not absolutely require mechanical retention.

Since composites didn’t require mechanical retention, preparations could be smaller. Amalgam often required healthy tooth structure to be sacrificed because of its need for mechanical retention. It also required a certain thickness to resist fracture.

Fluoride and composite worked together to make the concepts of turn-of-the-century dentistry fairly antiquated. Suddenly there was no need for extension for prevention. Instead, our philosophy became a John Lennon-ish “give teeth a chance”.

Class II restorations began to be done as “slot preps”, where the bur went straight through the marginal ridge to create a small slot instead of dovetailing into the occlusal surface. Since teeth were not experiencing decay in a similar manner as in the past, doctors began removing only the carious area. Healthy and caries-free structures were left untouched. Adhesive dentistry began to truly save teeth.

I began to refer to this new philosophy as Zen dentistry because I thought, “When the tooth is ready to be treated, the tooth will show me where to treat it.” Why destroy the entire occlusal surface of a lower molar with a cloverleaf amalgam prep when I could simply and easily remove the caries from an occlusal pit and leave the remaining tooth structure untouched? Composites allowed us to completely rewrite large portions of our textbooks on operative dentistry.

The Awakening

There are often unforeseen consequences to our actions, and sometimes only the lens of time allows us to see those consequences clearly. With composite restorations, what dentistry found is that composites are finicky materials.

Where amalgam materials had all the problems I mentioned previously, it wasn’t really technique sensitive in placement. As long as the prep was long enough, deep enough, and was undercut, you could pack amalgam in there and it would most likely work. Composite—not so much.

We quickly discovered that composite is technique sensitive. There was more Zen to composites than we thought. Wet, but not too wet. Dry, but not too dry. Then there was control of the field that had to be mastered. No saliva, no blood, and no crevicular fluid.

I used to love to say to the reps that came into my office, “How much saliva can I get in the prep?” Of course, they would sputter, “None!” And I would reply, “Have you seen where I work?”

All jokes aside, the technique side of dentistry came back to bite us (no pun intended). Amalgams were ugly and sacrificed tooth structure, but they corroded and sealed. Their longevity was pretty darn good. Studies now show that the average 2-surface composite lasts approximately 5 years.

The Dawn of a New Age

The problem with composites is recurrent decay. Composite doesn’t corrode like amalgam to seal its margins. That means that any breakdown in the bonding process, such as contamination, poor placement, or a bad curing light, can result in poor marginal integrity. That can then progress to marginal breakdown, and then the bacteria move into those tiny gaps and create acid, which causes caries. If we could just stop the bacteria, we could greatly extend the life span of a composite. The problem, of course, is stopping the bacteria.

Now, at long last, dentistry has a material that can do just that. Imagine a composite that can kill the bacteria that cause caries. You read that correctly. By the time you read this article, you will be able to purchase Infinix composite from Nobio.

For a very long time, dentistry has had materials that promised to limit decay, but now we have a material that has actually been scientifically proven to kill the bacteria that are the enemy of our restorations. Nobio has created a molecule that is embedded into the Infinix composite that kills bacteria. It is a quaternary-ammonium silica (QASi) that is mixed into the composite material. It doesn’t wear out or become depleted over time, and it doesn’t need to be replenished or recharged. The QASi molecule is part of the composite material, and it stays there for the life of the restoration.

Bacteria that come into contact with QASi are killed, which keeps bacteria from forming on the composite and along the tooth/restorative interface. Infinix has been cleared by the US Food and Drug Administration for reduction of demineralization, which is the beginning of the caries process. By reducing demineralization and killing the bacteria that cause caries, Infinix has the potential to greatly extend the life of composite restorations. Infinix is a complete restorative system that includes a dentin primer, bonding agent, and the Infinix composite, which is available in traditional and flowable viscosities.

The Procedure

The great thing about Infinix is that it is used in the same manner dentists are used to for traditional fourth-generation bonding procedures. Placement consists of acid etch with standard 37% phosphoric acid, rinse, lightly dry, apply primer, apply bonding agent, cure, place Infinix in an incremental placement technique, and cure. If you have placed a composite, you can place Infinix. It is a simple and efficient system that is easy to handle, matches well, and has laboratory studies that show it holds up well over time.

Wrapping Up

I was fortunate enough to be approached by Nobio about 2 years ago and have watched the product develop over that time. I began placing Infinix restorations in the fall of 2021, and I am starting to see those restorations in recare exams. They look as good today as the day I placed them.

Imagine a future where composites last for a decade or more. Imagine restoring your high caries rate patients with a material that actually kills the bacteria that causes that decay. The best part is that you no longer have to imagine those scenarios. They exist right now.

Infinix composites from Nobio are available now. Let the revolution begin! Dr Black would be proud.