How antimicrobial nanotechnology is set to empower composites

Last year, Dr. Lou Shuman wrote a Clinical Deep Dive article about a new nanotechnology that could change restorative dentistry forever (“A Composite Technology to Prevent Secondary Caries,” August 2018).

He interviewed the founder and CEO of Nobio, a company that’s working on a nanotechnology that kills bacteria on the tooth surface without affecting the rest of the bacteria in the mouth. Nobio’s founder Dr. Ervin Weiss and CEO Yoram Ashery discussed in detail how the technology works and what applications might benefit from this technology.

Nearly a year later, researchers presented the findings of two studies that featured Nobio’s nanoparticle at the 2019 International Association for Dental Research (IADR) General Session in Vancouver. The session was held in June. Attendees heard about an in vitro and an in vivo study on Nobio’s technology.

The research showed this composite formulation is comparable to current market leaders in strength and other physical qualities, but it also offers patients antibacterial protection.

For any clinicians who weren’t in the audience (or for those who are interested in a recap), here are the summaries.

In vitro study

Dr. Weiss presented the findings of a study titled “Mechanical and Antibacterial Performance of Novel Resin-Based Restorative Material.” Researchers performed the study to see if there were any significant differences in the qualities of three formulations: two from Nobio and one commercial product from 3M™ (Filtek™ Supreme Flowable). The two formulations from Nobio included one with the antibacterial nanoparticle (quaternary ammonium bound to silica, or QASi) and one without.

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Both the Nobio formulation without the QASi particles and the Filtek Supreme Flowable composite acted as control groups in this study. The researchers found all three composites were comparable in accordance with the ISO 4049:2009 specifications. In terms of flexural strength, radiopacity, depth of cure, water sorption and water solubility, there were no statistically significant differences. There was a significant difference in the reduction of E. faecalis when the QASi particle was present in the composite.

Researchers concluded the addition of QASi to the composite resulted in an antibacterial composite that has comparable physical characteristics to the commercial product.¹

In vivo study

Michal Dekel Steinkeller, of Tel-Aviv University, School of Dental Medicine, presented the results of another study titled “In-Vivo Performance of Antibacterial Flowable Composite.” In this study, researchers aimed to assess the antibacterial activity of Nobio’s QASi composite after six and 12 months use in vivo. They measured the ratios of live versus dead bacteria on plaque removed from composites attached to the mandibular premolars of healthy volunteers by using a live/dead stain ex vivo and analyzing the results through fluorescent microscopy.

The control group in this study was again the Filtek Supreme Flowable from 3M. The control (Filtek) sample was attached to a premolar on one side of the mouth, and the experimental (Nobio) composite to the opposite premolar on the other. After six months, biofilm was collected from each restoration with a periodontal curette, spread on a microscope slide, and stained to reveal dead bacteria (red) and live bacteria (green).

Researchers found live bacteria on control (3M) composite were about 70 percent of all bacteria, compared to only 35 percent on Nobio composite, at both six and 12 months. These results indicate the Nobio flowable composite offers long-lasting antibacterial activity.²

What this means for dentistry

I spoke with Dental Products Report’s technology editor, Dr. John Flucke, to get his take on what this could mean for dentists, patients and the industry as a whole.

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“I think knowing that you can put a material in the mouth and not really worry about it is huge,” Dr. Flucke says. “It reminds me of when we were using amalgams; you didn’t see a lot of amalgams come back with recurrent decay because they would seal themselves by corroding and kill the bacteria. It probably wasn’t very healthy or pretty, but it worked.”

Composite restorations are more prone to failure for that reason, Dr. Flucke says. They’re also technique sensitive, so any missteps in the preparation or placement of the restoration could lead to micro-gaps, which are susceptible to bacterial penetration and ultimately restoration failure.

“Knowing that Nobio technology in the composite will kill the bugs is tremendous,” he adds.

“Dentists have always had two choices to prevent restoration failure: local delivery of antimicrobials either through syringes, through a Waterpik®, or with oral rinses like chlorhexidine; or systemic options like tetracycline. But there is nothing like putting the material directly into the site where it needs to work; there is no better place to put the antimicrobial than where the microbes were two minutes before. Plus, it doesn’t have to be recharged like fluoride with glass ionomers.”

Other researchers have tried to address the issue of the micro-gap, but nothing looks quite as promising. Dr. Flucke outlined Dr. Rella Christensen’s recent research and protocol development for placing composites with glutaraldehyde, such as with Gluma® from Kulzer. Dr. Christensen showed two one-minute applications of a glutaraldehyde product will kill bacteria in the restorative area, but there are major drawbacks to this technique: it’s time-consuming and expensive. (A 5 mL bottle of Gluma is $152 from Henry Schein.)

“Using a composite with Nobio’s nanoparticle integrated into it would be a great thing because you wouldn’t have to change your process,” Dr. Flucke adds. “If you’re already doing the steps of etch, bond, place filling, you don’t change anything; you just etch, bond, and place filling with Nobio. You’ll get those results of eliminating bacteria in your preparation without the extra step or cost, and I think that’s a great idea.”

Dr. Flucke speculates the technology can be incorporated into a variety of dental materials and procedures such as varnishes, dentures or retainers.

“If it works as advertised, the sky’s the limit!”

References:

1. Zaltsman N, Zinger A, Malka E, Weiss EI. Mechanical and Antibacterial Performance of Novel Resin-Based Restorative Material.

2. Steinkeller MD, Salzman N, Weiss EI. In-Vivo Performance of Antibacterial Flowable Composite.