Dental caries, better known as cavities, are one of the most common dental problems. Almost everyone has a filling or two in their teeth, and even with great oral hygiene, your genetics can still put you at risk.
The increase in sugar consumption in Western diets has also played a role, but dental caries still present one of the most widespread non-communicable human diseases.
Traditionally, dental fillings have been made from any of a variety of materials. Non-reactive, corrosion-resistant metals like gold and silver have a long history of use in dentistry, although modern fillings are more likely to be made from composite materials that mimic the color of actual teeth. But in the very near future, the majority of fillings will be made from a totally new material: microscopic nanoparticles.
Why Microscopic Nanoparticles Make Great Dental Fillings
The fillings of the future may be made from something totally different from what’s been used in the past. Instead of metal amalgams or composite resin, dentists may soon begin using microscopic nanoparticles to fill in dental caries. These particles of silica and zirconia are unbelievably small — anywhere from 1 to 100 nm. They share their size scale with things like DNA (2.5 nm) and viruses (30-50 nm), and are significantly smaller than most bacteria.
Their small size means that masses of these nanoparticles can fit into nooks and crannies inside a cavity. Their surface free energy is massive, enabling them to bond very strongly both to one another, and to other materials.
Inorganic nanoparticles that could be used in dentistry include silver, gold, titanium, zinc, and other metals that have been known for centuries for their antimicrobial properties. Although silver is toxic to humans in high concentrations, tiny nanoparticles of silver have lower toxicity — along with improved effectiveness as a bactericidal agent. Silver is inert in its plain metallic state, but as it reacts with moisture in the human body, it becomes ionized. This ionized silver is very reactive, and can cause cell death in bacteria. The ionized silver nanoparticles have effects on the cell wall, the plasma membrane, bacterial DNA, and bacterial proteins. Ultimately, its disruption of essential cellular processes leads to lysis.
Interestingly, these materials also have antimicrobial properties. This means that not only do they repair cavities, but they may also help prevent future tooth decay. Microparticles composed of metal oxides are capable of killing bacteria that come into contact with them. Not only that, but they’re also capable of killing viruses and fungi. Because metallic nanoparticles are so incredibly small, large surface areas of each particle are able to come into contact with a bacteria. For example, the contact surface area for a 10 nm particle is a 10^9 increase over the contact surface area of a 10 micrometer particle. This greatly enhances the material’s ability to eliminate bacteria.
Another advantage is that bacteria do not develop resistance to inorganic nanoparticles. This is important, because currently, there’s an ongoing antibiotic resistance crisis, attributed at least in part to widespread overuse of antibiotic drugs in previous decades. The ability of metallic nanoparticles to kill bacteria could help prevent future infections, as well as warding off tooth decay.
The Future of Dental Nanotechnology
Today, the major barriers to implementing these new dental nanotechnologies are that they haven’t been extensively tested in humans. Pre-clinical and clinical trials will be needed before these products can safely go to market. But eventually, nanoparticles may very well become the standard material for dental fillings.