Fillings and Tooth Decay

Fillings/restorations are placed in teeth to repair areas of damage caused by trauma (like a hockey puck or "cavities").

Silver fillings were invented in New York in the 1830’s by two brothers who ground up silver coins and mixed them with mercury which then set into a very stable BENIGN INERT metal complex. The ratio of silver fillings is now 70% silver to 28% mercury. Silver fillings are rarely used now used because of concerns about the mercury content and they slowly form an oxidation layer on the surface which is dark grey and is aesthetically displeasing.  Silver is still occasionally used in special situations where the area of damage cannot be kept dry long enough to place a white filling or the area does not allow a curing light to penetrate and activate the catalyst that sets the filling. 

There are lots of anecdotal opinionated internet posters that make all kinds of unsubstantiated claims about the evils of silver fillings.

Silver fillings can last as long as 50 years or more in some cases. There are no scientific studies that show any harmful effects from it on patients of the dental teams. This information is included because if a silver filling fills in the damaged area and is not leaking then there is no need to rush into getting it replaced. It is unethical for a dentist to suggest replacing it. The owner of the silver filling(s) may decide to replace it because of esthetics, or because they do not like the idea of the mercury content but the dentist should NOT be putting this spin on the situation.

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Silver polishes beautifully.

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This filling needs to be replaced

White fillings (aka Composite resin)
What the world is using to fill teeth with now. They have been around for about 40 years in their present form but it is only in the past 10-15 years that the formulations have become much better in terms of not shrinking and leaking. A dental composite typically consists of a resin-based oligomer matrix, such as a bisphenol A-glycidyl methacrylate (BISGMA), urethane dimethacrylate (UDMA) or [(semi-crystalline polyceram)] (PEX), and an inorganic filler such as silicon dioxide (silica) – to oversimplify, a resin plus tiny quartz particles. Life spans of these are typically 10 to 25 years. They have a light-activated catalyst in them that makes the material instantly harden when exposed to a bright light. They come in different shades of white.

Tooth decay (aka Caries or "Cavities")
Mouth bacteria have got through the fairly thin outer layer of Enamel into the layer under that called the Dentin layer. Looking at the X-sectioned eye tooth below the outer whiter enamel layer and the inner yellower dentin layer can be seen. Enamel is the hardest substance in the body, much harder than bone. It is very tough stuff. It is made of 98% Calcium. Bacteria cannot live off this layer. The only way they can damage it is by certain kinds of normal mouth bacteria releasing excess acid that erodes a hole through it. Once the enamel layer has been breached the bacteria can migrate through it into the softer dentin layer. Dentin is the second hardest substance in the body. It is 65% Calcium but 35% organic material. This 35% organic portion is food for bacteria. Bacteria will eat away the inside of the tooth until the enamel caves in and/or it gets into the “nerve” (pulp chamber) of the tooth and cause pain and abscesses which are cured by extraction and root canals.

Prevention (SUGAR IS THE ENEMY)
With a sugar free diet people do not get cavities. Excess sugar in our mouths for extended period acts as food for certain kinds of naturally occurring bacteria. They eat this sugar for their own energy and then release it break down products as ACID. This acid likes to accumulate in the grooves of the biting surfaces, between the teeth just below where the push against each other, and along the gum lines of teeth, especially on the cheek sides. This is where "cavities" occur most frequently. Sugar creates acidic conditions in the mouth by lowering the pH. 

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On the left of the left picture there is some damage only to the enamel which does not need a repair yet. It is arrestable by majorly reducing the amount of sugar in the diet.  In the right picture in the lower teeth this initial enamel decalcification can be seen on the x-ray. Again, this does not need a filling yet if the diet is changed.

The right side of the left picture and the upper teeth areas circled in red show areas where the bacteria are through and are having a food fest inside the teeth. These areas need intervention/fillings.

Diet
This is not to say you cannot eat sugar. Just do not allow your teeth to be exposed to it for prolonged periods. It is OK to have a chocolate bar or a bowl of ice cream. Your might have some water afterwards to wash away some of the sugar or you might even brush. But sucking on candies, including throat lozenges, unless it has a safe sugar substitute is not good. Pop, especially the Colas, which are syrupy and acidic, are especially destructive to teeth. Sugar is everywhere as it sells food for the food industry. Ketchup can have as much as 29% sugar in it. Besides being bad for your teeth it is also hard on your body. Honey is natural sugar but bacteria do not differentiate natural from refined sugars. Fruit is great but fruit juices are not. Use common sense and read labels. 

Flossing
Does nothing to reduce tooth decay! It does let a little oxygen under your gums though but does nothing to prevent tooth decay.

Dry Mouth
Another cause of decay – bacteria coat the teeth and are not diluted and washed away. This is especially a risk for seniors who are on medications. The most common side effects of medications are dry mouth and many seniors are on multiple medications. And then if they are in a care facility they may be getting excess feel good sugar food and may not be able to clean their teeth properly – a recipe for problems for the person and the family.

Decay removal and repair
The areas of bacterially invaded tooth structure changes colour to darker yellow or orange or brown or black and the area gets soft. These areas are removed with a drill bit (aka a bur) until there is only hard white tooth left and then the filling is placed. The filling has to fit against the opposing tooth meaning it cannot be so high that it hits before the other teeth of these two teeth will get sensitive to temperature and sore to bite on. They must butt up against the adjacent teeth of this area will be a food trap which is more than just annoying, it is also bad for the gum and can lead to re-decay if there is always food jammed in there.