Cavities are far less common today than they were in the past. Fluorinated water and toothpaste has helped us combat the damaging effects of bacteria in our mouths. However, poor brushing habits, genetics, dietary choices, tobacco/drug use, and certain strains of bacteria still result in teeth forming cavities. Fortunately, dentists can often repair cavity damage by applying a filling.
Fillings are inlays, onlays, or moldable material applied to decayed teeth that restore the teeth to their normal function. Fillings also prevent bacteria from further damaging the teeth.
Types of Cavity Fillings
Cavity fillings are made from one of four materials: gold, porcelain, composite resin, or amalgam. Which filling is best for you depends on your preferences, budget, and even which teeth were damaged.
Gold fillings (inlays or onlays) are, overall, the best material for posterior (back) dental filings. Gold fillings well tolerated and can last decades, if not a lifetime. They won’t crack or fracture. And they have approximately the same coefficient of expansion as natural teeth, which means gold expands and contracts with your teeth in response to temperature changes.
For these reasons, among others, many dentists consider gold the best material for fillings.
The primary drawbacks to gold are its price and the fact that it takes more than one visit to apply it. During the first visit, the dentist will prepare the tooth and take an impression or scan of the area that needs filled. They’ll then place an order with a dental lab to have the gold filling made. It will take a few days before the filling is then ready. During the second visit, the dentist applies the filling. It is because of these steps that gold fillings are more expensive than other treatment options.
Another drawback is the color. Gold stands out against teeth’s natural color, and lab technicians cannot change the color of gold. Dentists usually don’t recommend gold for cavities in front teeth because of this.
Porcelain fillings (inlays or onlays) are excellent choices for anterior (front) teeth. Like gold, porcelain inlays and onlays are produced in a lab, and they cost about the same as gold.
The process of getting and producing this filling is the same as gold. But unlike gold, technicians can alter the color of porcelain to match the color of the surrounding teeth.
Also unlike gold, porcelain can crack. It also doesn’t wear at the same rate as natural teeth, so over time it can look less natural. Porcelain can also wear surrounding teeth if it rubs against them.
Amalgam (also called “silver” or “mercury”) has been used for dental fillings for more than 150 years. It is one of the most common, and oldest, materials used to fill cavities. It’s relatively inexpensive and resists wear and tear well, which is why it has remained so popular.>
Amalgam is made from mercury, silver, tin, and copper, which the dentist mixes right before applying the filling. Amalgam may also include small amounts of zinc, indium, or palladium. When the materials used for amalgam come together, they form a soft alloy a dentist can shape. The amalgam hardens after a few minutes.
Concern about mercury’s safety have increased in recent years. In 2009, the FDA moved amalgam from a class I (least risk) medical device to a class II (more risk) due to concerns about mercury poisoning. The FDA still considers it safe enough to use, however, and the ADA, among others , have declared amalgam safe after research and after reviewing studies. Other groups disagree.
People who have had a cavity filled with amalgam shouldn't worry that they will suddenly wake up with mercury poisoning, however. Although amalgam contains mercury, the mercury in it bonds with the other materials and therefore doesn’t “leak”. The mercury is locked in the filling; all but an extremely tiny amount (less than that in fish) gets into your body. It is this tiny amount, however, that concerns people, as mercury builds up in people’s bodies over time.
Other concerns with amalgam don’t have to do with the material itself. The World Health Organization and the World Dental Federation have called for a decreased use of amalgam because of the amount of mercury getting into the environment.
Besides concerns about safety, amalgam’s main drawback it its color. It’s easy to notice and does not look as “clean” as gold. For this reason, it’s not often used for front teeth. A secondary drawback is its coefficient of expansion, which doesn’t match teeth as well as gold. This can eventually lead to cracked teeth, though studies show that this rarely happens.
Composite resins are likewise very common materials for fillings. Resin fillings are made using tiny pieces of silica, which plastic (resin) surrounds. Dentists using composite resin match it to the color of the patient’s teeth, and the resin is often indistinguishable from natural tooth material once installed.
Resins aren't ideal for filling a large cavitiy because they can chip or wear over time. They also stain differently than natural teeth, and they do not tend to last as long. Dentists and patients have also noted concerns with BPA in dental resins, though not all resins contain BPA.
Dental resins are continually improving, however. They’re useful because they bond directly to teeth, so less healthy material needs removed than for other filling materials. Also, dentists can apply a resin filling in one visit.