When a person has decay there are multiple choices on how to correct the hole in the tooth and restore the tooth back to function.
When a tooth has decay it may become sensitive and if not treated quickly enough may become tender. There are options for the restoration but the amount of tooth remaining is a major determining factor as to the best way to restore the tooth.
Amalgam or silver are one means of restoring decay in a tooth. The filling requires enough of the tooth to be strong enough to hold the restoration in place. Dental amalgam is a dental filling material used to fill cavities caused by tooth decay. It has been used for more than 150 years in hundreds of millions of patients around the world.
Dental amalgam is a mixture of metals, consisting of liquid (elemental) mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50% of dental amalgam is elemental mercury by weight. The chemical properties of elemental mercury allow it to react with and bind together the silver/copper/tin alloy particles to form an amalgam.
When placing dental amalgam, the dentist first removes the decay and then shapes the tooth cavity for placement of the amalgam filling. The softened amalgam putty is placed and shaped in the prepared cavity, where it rapidly hardens into a solid filling. This is shaped to be able to function during chewing for long-lasting results.
Amalgam restorations are stronger and last longer than composites, but they can also break down with time. The average life expectancy of an amalgam filling is 8-10 years, but smaller ones can last up to 20 years.
Composite fillings are tooth-colored and are placed in the tooth in a manner that they are bonded to the tooth, so they help “hold the tooth together.” This is a major benefit of these restorations. The layer between the composite and the tooth is the potential weak point of these restorations as can be observed in the following electron microscope image.
The weaker the bond between the tooth and the composite leads to leakage and failure of the restoration. The average life expectancy of a composite filling is between 5 to 7 years. The smaller the filling, the smaller the tooth surface to composite surface and the greater the probabilty of success. The other problem with the composite is it is a combinarion of a granular material for hardness and wear and a more liquid part for adaptation to the tooth surface. The granular nature makes it harder to keep this clean below the gum tissue.
Gold restorations are the best means of restoring the biting surface of the tooth as they last the longest and are the strongest restoration. An inlay fits inside of the tooth, while an onlay covers one or more of the cusps of the tooth as observed here. The material is strong enough that it can withstand all of the biting force during chewing and the average life expectancy is 25 years or more. I have these in my mouth and they have been there for more than 40 years.
Ceramic inlays or onlays are another example of ways to rebuild a tooth with decay. This is a restoration that is made from a model of the tooth, or an image of the tooth and is made to fit the tooth as precisely as possible, but the edges of the restoration / tooth are not as precise as the gold inlay / onlay. The color advantage is obvious when compared to the metal restoration.
Here we can see the breakdown of the margins of the silver fillings and how these are more accurately and permanently restored with inlays. The edge of the amalgam is the weak area of the filling and decay occurs here, where this is not the problem with inlays.