Dear Dr. D.,
Do Fillings Cause Cracks in my Teeth?
Yes, yes, yes, but mostly just the silver fillings and only if they’re plus-sized. The silver fillings are 50% mercury, and a lot of people are worried about the poisonous effects, but the jury is still out about whether or not mercury locked in a solid state is harmful. However, the physical properties of mercury are not in doubt.
The old-time thermometers were made with a mercury insert because mercury responded quickly to temperature changes. Even one degree of increased heat would make the mercury swell and “rise” in the thermometer.
Cold would make the mercury shrink in size and “fall” in the thermometer. Enamel, the outer layer of tooth structure, is basically a crystal and does not react to temperature changes. So let’s put the two together.
Imagine putting a large swimming pool of solid-state mercury (a filling) in the middle of a crystal (your tooth). Then have a cup of coffee. The filling is going to expand, and there are only two ways to go – up or out. When the filling expands out, the tooth is going to crack. If the filling expands up, the opposing tooth will rub against it, and both teeth will eventually adjust, or it will shrink back into position as the temperature normalizes.
The larger the filling is, the more it will expand outward. If there is plenty of enamel (usually 2/3 of the width of the tooth), then the expansion is upward. Outward means cracks and new restorations if they’re caught in time. If they’re not caught early, the cracks will turn into fractures and loss of that tooth.
Silver fillings are still placed by dentists because they are cheaper and faster. If placed properly, they can last a long time, but nothing will stop it from being ugly.