Composite vs Amalgam Fillings

When teeth have cavities or are broken, in some cases they can be restored with a simple filling. Fillings have limitations and in order to be successful a certain amount of strong tooth is needed to support the filling.

There are two types of filling materials. One type is a tooth colored resin material that bonds to the tooth. The other type is a mercury filling that is silver in color. Many dentists today will not use or recommend the mercury based fillings. You should discuss this with your dentist before the filling is placed in your tooth.

Tooth Colored Fillings:

The concept of “filling” is replacing and restoring tooth structure that is removed due to decay or fracture with a material. With today’s technology, you no longer have to suffer the embarrassment of unsightly silver/mercury fillings or metal margins of the past. Space-age, state-of-the-art, tooth-colored resin or porcelain adhesive materials are used to replace dark, looking amalgam fillings.

Silver vs. White Fillings

The “silver” fillings are really silver amalgams containing a mixture of silver-tin alloy, copper and mercury that sets up hard and silver-colored.

White fillings are either composite resin (not to be confused with true porcelain) containing a mixture of acrylic plastics, quartz fillers and colorants or true porcelain. True porcelain filling are called inlays (if they fit inside the cavity less than one third the width of the tooth) or onlays (if they replace or support the cusps tips). These porcelain restorations were generally made in a lab with two or more office visits, but with CEREC® 3D, we now precision-mill them from factory manufactured uniform blocks in one visit in our office. Both of these true porcelain type fillings are cemented or bonded into place and are much more precise and biocompatible than silver or composite which are pressed into the prepared hole (cavity) in your tooth.

The cheapest and most common choices for filling small cavities are silver amalgams (a mixture of silver-tin alloy, copper and mercury that sets up hard and silver colored) and composite resin (a mixture of acrylic plastics, quartz fillers and colorants). There are several differences besides the obviously more esthetic results of composites over amalgams. A big difference, which insurance companies seem to consider the most important, is longevity. Amalgams last up to 20% longer than similar composite restorations.

For large cavities where more than half the width of the tooth is involved, these cheaper filling materials (silver and composite) are prone to breakdown. Generally, studies and my personal experience find these fillings break down (to the point they need to be drilled out and redone) in the range of 3 to 5 to 7 years when filled with composite while large amalgam fillings last a bit longer but may lead to tooth fracture. Due to the need for more stringent moisture control and more technique-sensitive procedures to place composite, in most dental offices white composite fillings cost more than silver amalgam.

These two factors make silver fillings more economical than the more natural looking composites, so that is why insurance companies rarely approve of a composite filling in the back teeth. (They will substitute payment for the cheaper amalgam when they receive a claim for posterior composites — just look at any Explanation of Benefit forms for composite filling you may have received.)

Besides being virtually invisible, composites have a property of bonding to the tooth structure. This bonding can protect and increase the overall strength of the tooth being restored, but if the bonding stays intact on the biting (occlusal) surface but breaks down as it usually does in between teeth where it is thicker and flexes more when you bite and chew food, new decay may progress deeply before it is detected. Sometimes, the first sign of this hidden leakage under composite fillings is the sudden onset of severe pain of a root canal nerve infection.

The choice of which restorative material to use in your mouth depends on balancing the factors of appearance, longevity, strength of the tooth involved, and cost. You have to decide with your dentist’s guidance as to the size of the filling and your goals/expectations for the filling.

Which to Choose?


Silver has been used as a filling for teeth for over one hundred years. While there is mercury present in the silver filling material, called amalgam, in the past century there has been no evidence showing that silver fillings are harmful to patients. Just like the cyanide in crazy glue where the cyanide is compounded with other ingredients that make it harmless, the mercury in amalgam is compounded with silver, tin, and copper to make it just as harmless. Studies about the release of mercury from normal wear of chewing and grinding show that 5 fillings release about the same amount of mercury as is found in a tuna fish sandwich.

Silver is a strong filling agent lasting longer than comparable composite fillings. It also costs significantly less than composite fillings (up to 25% less in some cases). The main argument against the use of silver fillings is esthetic. Depending on where the tooth to be filled is located in the mouth, the appearance of a silver filling may be less attractive than a more natural-looking composite filling. Also, for some patients the feeling of metal in the mouth may be displeasing. Over time, like most metals, silver fillings will eventually corrode and even leak causing decay to reoccur underneath the fillings. There is also a slow expansion that amalgam undergoes and the part of the tooth next to the filling may fracture over time, necessitating a much larger filling, a crown or even extraction of the tooth if the fracture is vertically down the root below the bone.

Composite Fillings:

Composite fillings are primarily a resin which has been “filled” with other inorganic materials. This compound makes a composite filling more resistant to wear, color adjustable, and easier to polish. The advantages of choosing a composite filling include a more natural appearance, frequently a strengthening of the filled tooth, and a bonding of the filling to the tooth creating a better seal. This bonding also means that the filling can often be made smaller than a comparable silver filling since silver requires certain size criteria be met to resist breaking or falling out. The disadvantages are that composite fillings themselves are weaker and may last a shorter period than a silver filling. In addition, a composite filling may cost about 25 % more than the same silver filling.

Composites suffer from what is called dissolution. They will actually dissolve slowly over time in your mouth regardless of whether you eat on them directly or not. In addition, they can discolor over time acquiring a yellowish tinge. Composite fillings also may get pitted leaving pinholes on the surface, which may pick up discoloring and stain permanently. Because composite has the largest coefficient of thermal expansion, after being repeated exposed to cold foods such as ice cream, cold beverages which cause the composite filling to shrink more than the tooth and then to hot foods, including coffee, tea, soups, and heated foods which cause the composites to expand more than the tooth, the bonded joint between the filling and the tooth will breakdown and allow fluid, food and bacteria to get in and form recurrent decay.

CEREC® 3D Porcelain Inlays and Onlays

In the cases of large cavities, we generally feel that CEREC® 3D Porcelain inlays and onlays or partial crowns are FAR SUPERIOR to either composite or amalgam since they should last 20+ years and avoid the controversies of amalgam and composite breakdown and possible toxic byproducts.

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