Dental: Overview of Dental Filling Materials
By Joseph C. Kern, DDS
Amalgam is the least expensive material for filling a cavity. It is also very strong and durable. It is relatively easy to place and somewhat forgiving of an imperfect environment during placement. Since amalgam does not bond to the tooth, it is held in place with mechanical retention. This requires the removal of more tooth structure than the other materials available. Enamel seems to crack around amalgam restorations more than other materials, which may lead to tooth fracture and the need for a crown. Amalgam is unesthetic and gets more unesthetic as it ages (and turns from silver to black).
Amalgam is an alloy composed of several metals, specifically mercury and some combination of silver, tin, copper, and zinc. Mercury makes up 40-50% of the alloy. A small amount of mercury is released throughout the lifespan of the restoration. Opinions vary about whether or not this poses a health risk.
Pros: Least expensive, very durable, easy to place, least technique-sensitive, forgiving of imperfect conditions during placement
Cons: Not esthetic, requires removal of more tooth structure, contains mercury
Composite resins comprise most of the “white” or “tooth colored” fillings and are, essentially, plastic. While the materials are constantly evolving and improving, there currently are no composite resins that are as strong and durable as amalgam, gold, or porcelain. This means that a composite resin filling will fail sooner and need to be replaced sooner than an amalgam, gold, or porcelain restoration. Composite resins require perfect conditions for successful placement. If the tooth cannot be kept perfectly dry during placement, the restoration will fail. Since composite resin chemically bonds to the tooth, it is not necessary to remove as much tooth structure when preparing a tooth for a composite resin filling, as compared to an amalgam filling. While a composite resin restoration is very esthetic, it will discolor over time and may need to be replaced if it is in an area of esthetic concern.
Pros: Very esthetic, requires removal of less tooth structure
Cons: Not as durable, very technique-sensitive, requires perfectly dry conditions to be placed successfully.
Glass Ionomer is similar to composite resin and, like composite resin, bonds well to the tooth. However, It is not as strong or durable as composite resin. It is also not as esthetic as composite resin and will discolor more easily. Glass Ionomer is, however, easier to place than composite resin and is more forgiving of less than perfect conditions. This makes it a good choice for fillings in primary teeth. Glass Ionomers have the added benefit that they release fluoride for a time after placement and continue to absorb and release fluoride during the lifespan of the filling.
Pros: Esthetic, not as technique-sensitive as composite resin, more forgiving of imperfect conditions during placement, absorbs and releases fluoride.
Cons: Not very durable
There are no materials available today with the longevity of gold. Gold is very durable but, obviously, not esthetic. If esthetics are not a concern, there is no better material for restoring a tooth. Gold restorations are difficult and technique-sensitive. They require two appointments because the restoration is fabricated at a dental laboratory. Also, the material itself is expensive. For these reasons, gold restorations are very expensive. Gold restorations are generally not feasible on a primary tooth.
Pros: Very durable (the best non-esthetic restoration)
Cons: Very expensive, requires two appointments, very technique-sensitive
Porcelain is the most esthetic of the tooth colored restorations and it does not discolor or stain like composite resin or glass ionomer. Porcelain is very strong and much more durable than composite resin or glass ionomer. It also bonds very well to the tooth. Porcelain is actually harder than enamel so it may cause premature wear of the tooth opposing the porcelain restoration. Porcelain restorations are difficult and technique-sensitive. They also, like gold, usually require two appointments because the restoration is made at a dental laboratory. The exception would be a CEREC restoration, which is a porcelain restoration that is milled at the dental office in one appointment. While porcelain itself is not as expensive as gold, the restorations are more difficult and, therefore, more expensive to produce. For this reason, porcelain restorations are usually the most expensive of all restorations. Porcelain restorations are also not feasible on primary teeth.
Pros: Very durable, very esthetic (the best esthetic restoration)
Cons: Very expensive, requires two appointments (unless done with a CEREC), very technique sensitive, may cause wear of opposing tooth.
What is the best filling for primary teeth?
For small, one or two surface cavities composite resin or glass ionomer would be acceptable. The larger the restoration, the more likely it will fail. Primary teeth with large two or three surface cavities should be restored with stainless steel crowns. Posterior primary teeth that require a pulpotomy should also be restored with stainless steel crowns. A pulpotomy is the removal of the pulp (or nerve) in the primary tooth and is necessary if the pulp is exposed when the decay is cleaned out.
Why do pediatric dentists use amalgam and stainless steel crowns?
Amalgam is the cheapest, strongest, and easiest to place filling material for primary teeth. Also, in most states, Medical Assistance will not pay for composite resin fillings on posterior primary teeth. So the dentist either must place an amalgam restoration or place a more expensive composite resin restoration at the cost of the amalgam (which is already discounted substantially for Medical Assistance).
Pediatric dentists treat the most difficult pediatric cases: children who are very young, have extensive dental needs, or have developmental disabilities. Many of these children require sedation or general anesthesia in order to restore their teeth. When a pediatric dentist restores a tooth on a child that requires sedation or general anesthesia, he/she is going to use the strongest restoration available -- which is a stainless steel crown. This is to minimize the chance of needing to expose the child to the risks of sedation/anesthesia again in the future if the restoration fails. Pediatric dentists tend to treat primary teeth more aggressively than general dentists. A general dentist will tend to place a composite resin filling in a primary tooth with two surfaces of decay -- a pediatric dentist will place a stainless steel crown. Again, this is to try to avoid having to treat the same tooth again in the future if the restoration fails.
Bisphenol-A (BPA) is a synthetic chemical resin found in many consumer plastic products, such as plastic bottles, the lining of some canned foods, toys, plastic tableware, and infant bottles. Recently there has been concerns raised about BPA in dental sealants and composite resin fillings. BPA is rarely used directly in the manufacturing of dental materials but is the starting ingredient in the formation of two monomers that are widely used in dental resins: bis-GMA and bis-DMA. The majority of dental resins are formulated with bis-GMA and research has shown that bis-GMA does not hydrolyze into BPA. Resin materials containing bis-DMA can break down into BPA after coming into contact with salivary enzymes. The detectable levels, though, are 2 to 5 times lower than the daily exposure from food and the environment.