On a weekly basis I seem to have at least one conversation with a patient about white fillings. Recently, someone asked me why their old white fillings done by a previous dentist were failing while some of their old silver fillings from childhood were still going strong. Here's a brief explanation.
White fillings have a life expectancy of 2 to 25 years. Silver fillings will usually last 15 to 30 years. The reason there's such a wide discrepancy in white fillings is that they're very technique-sensitive — and there are many types of materials and bonding agents in use. Silver fillings, on the other hand, are far less technique-sensitive, and there's basically only one type.
The longevity of a white filling material is determined by numerous factors, but two are especially important:
Polymerization shrinkage rate is measured as a percentage. The lower the shrinkage rate, the lower the chance of a cavity developing under the filling. The shrinkage percentage can range from as low as 1.4 percent to as high as 5 percent. Lower is better.
Compressive strength measures the ability of the filling to withstand chewing and grinding. The higher the compressive strength, the less likely the filling will be crushed. Measured in MPa, this ranges from 100 to 500 MPa. Higher is better.
The bonding agent matters too. The bonding strength to enamel can range from 10 to 38 MPa, and to dentin from 5 to 44 MPa. A stronger enamel bond doesn't always mean a stronger dentin bond — the dentist must choose the right agent for each case.
There are over a hundred different kinds of composite material and over fifty different kinds of bonding agents. Better materials cost more. New materials and bonding agents are introduced every few years — so a dentist has to keep up to date if they want to provide the best level of care.
We use the best bonding agents and white filling materials on the market, and we change them out for better products regardless of cost on a regular basis. We use a variety of bonding agents and filling materials depending on the type of cavity or tooth we're working on.
I spend hundreds of hours every year researching dental materials. Most dentists have no idea how their material rates against others. Some dentists will only use the material that gets them the best bang for their buck, or the material they used in dental school — which leads to more failed fillings.
As of today, the white filling material we use has a polymerization shrinkage rate of 1.48% and a compressive strength of 500 MPa. Our bonding agent has an enamel bonding strength of 35 MPa and a dentin bonding strength of 44 MPa. We can be specific about these numbers because we measure.
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- fillings
- clinical
- materials