Composite Fillings vs. Siver Amalgam Fillings

The following article was adapted and modified with permission from the Academy of General Dentistry web site.

What is a composite restoration?
A composite resin is a tooth-colored plastic mixture filled with glass (silicon dioxide). Introduced in the 1960s, dental composites were confined to the front teeth because they were not strong enough to withstand the pressure and wear generated by the back teeth. Since then, composites have been significantly improved and can be successfully placed in the back teeth as well. Composites are not only used to restore decayed areas, but are also used for cosmetic improvements of the smile by changing the color of the teeth or reshaping disfigured teeth.

How is a composite placed?
Following preparation, the dentist places the composite in layers, using a light specialized to harden each layer. When the process is finished, the dentist will shape the composite to fit the tooth. The dentist then polishes the composite to prevent staining and early wear.

How long does it take to place a composite?
It takes the dentist about 10-20 minutes longer to place a composite than a silver filling. Placement time depends on the size and location of the cavity-the larger the size, the longer it will take.

What is the cost?
Prices vary, but composites average about one-and-a-half to two times the price of a silver filling. Some dental insurance plans cover the cost of the composite up to the price of a silver filling, with the patient paying the difference. As composites continue to improve, insurance companies are more likely to increase their coverage of composites.

What are the advantages of composites?
Esthetics is the main advantage, since dentists can blend shades to create a color nearly identical to that of the actual tooth. Composites bond to the tooth to support the remaining tooth structure, which helps to prevent breakage and insulate the tooth from excessive temperature changes. Composites often allow a dentist to prepare a cavity much smaller than can be achieved with gold, porcelain or silver amalgam fillings. Making a smaller filling is very important to the strength of a tooth and for increasing the amount of time a filling will wear. Composites work very well with laser prepared cavities. Amalgam, gold or porcelain fillings cannot be used with laser or air abrasion prepared fillings. The ability to do laser prepared fillings often makes it possible to not have to use “shots” or drilling to fill a cavity. Composite bonding on the front teeth can be made very beautiful and natural looking. Composites can be used to seal a tooth in young people to prevent the most common pit and fissure decay. Composites can many times be repaired instead of having to remove the whole filling if part of it has failed.

What are the disadvantages?
Composites are technique sensitive and intolerant of any moisture when being placed. It is sometimes impossible to keep a cavity dry to place a composite. Also, the shade of the composite can change slightly if the patient drinks tea, coffee or other staining foods. Composites tend to wear out sooner than silver fillings in larger cavities, although they hold up as well in small cavities.

How long will a composite last?
Studies have shown that composites last 7-10 years, which is comparable to silver fillings except in very large restorations, where silver fillings last longer than composites.

What Is Dental Amalgam?
Most people recognize dental amalgams as silver fillings. Dental amalgam is a mixture of mercury, and an alloy of silver, tin and copper. Mercury makes up about 45-50 percent of the compound. Mercury is used to bind the metals together and to provide a strong, hard durable filling. After years of research, mercury has been found to be the only element that will bind these metals together in such a way that can be easily manipulated into a tooth cavity.

Is mercury in dental amalgam safe?
Mercury when combined with silver, tin and copper in dental amalgam is not harmful to the health. When mercury is combined with other materials in dental amalgam, its chemical nature changes, so it is essentially harmless. The amount released in the mouth under the pressure of chewing and grinding is extremely small and no cause for alarm. In fact, it is less than what patients are exposed to in food, air, and water.

Ongoing scientific studies conducted over the past 100 years continue to support the conclusion that amalgam is not harmful. Claims of diseases caused by mercury in amalgam are anecdotal, as are claims of miraculous cures achieved by removing amalgam. These claims have not been proven scientifically.

Why do dentists use dental amalgam?
Dental amalgam has withstood the test of time, which is why it is, at times, the material of choice. It has a 150-year proven track record and is still one of the safest, most durable and least expensive materials to fill a cavity. It is estimated that more than 1 billion amalgam restorations (fillings) are placed annually. Dentists use dental amalgams because it is easier to work with than other alternatives. Some patients prefer dental amalgam to other alternatives because of its safety, cost-effectiveness, the ability to be placed in the tooth cavity quickly and under conditions which would not allow for the use of white composite fillings due to a difficult location and inability to keep the area dry while filling. Some insurance carriers have coverage limits on the back teeth for dental amalgam and do not cover the increased costs for composite fillings, and thus some patients request amalgams for this reason too.

(Note: Placing amalgams because insurance carriers place financial barriers to composite restorations is generally a bad idea, because often amalgams require a larger hole be prepared into a tooth than a composite filling would require. This unnecessarily weakens a tooth if a smaller white filling could have been placed. This is now often true with laser prepared cavities, which are very small indeed. Amalgam is just not the right thing to do for this kind of laser prepared cavity or any very small filling.)

Why don't some dentists use alternatives to amalgam?
Alternatives to amalgam, such as cast gold restorations, porcelain, and composite resins are more costly. Gold and porcelain restorations take longer to make and can require two appointments. Composite resins, or white fillings, are esthetically appealing, but require a longer time to place the restoration. White composite filling materials tend to wear a little faster than amalgam but that short coming is improving quickly. While composite fillings tend to bond the tooth sides to the filling and can increase the resistance to fracturing, silver fillings seem to work better when a cusp is built completely from amalgam than does a white composite.

What about patients allergic to mercury?
The incidence of allergy to mercury is far less than one percent of the population. People suspected of having an allergy to mercury should be tested by qualified physicians, and, when necessary, seek appropriate alternatives. Should patients have amalgam removed out of concern about mercury? No. To do so, without need, would result in unnecessary expense and potential injury to teeth.

Are dental staff workers occupationally exposed?
Dentists are using pre-mixed capsules, which reduce the chance of mercury spills. And newer, more advanced dental amalgams are containing smaller amounts of mercury than before. An interesting factor can be brought into this: Dentists and staff have been shown to excrete 4 to 5 times more mercury in the urine than the average person. Because dental staff members are exposed to mercury more often, one would expect dental personnel to have higher rates of neurological diseases, such as multiple sclerosis. They, in fact, do not.

What are other sources of mercury?
Mercury can be found in air, food, fish, and water. We are exposed to higher levels of mercury from these sources than from a mouthful of amalgam.

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