The most common filling materials are amalgam and composite (also known as resin). Our office has decided to no longer provide amalgam fillings because we prefer working with composites and have achieved great clinical success with them. It’s important for you to be aware that some insurance policies only cover amalgam fillings on back teeth because that is the less expensive material. If this is the case for you, please talk to one of our receptionists about how this may affect your copay. Below you will find some information about amalgam and composite. If you still have questions, please feel free to ask the dentist during your appointment.
Amalgam is an alloy composed of mostly silver, but also contains small amounts of other metals. Some people have concerns about mercury in amalgam fillings, but it is important to note that when the material is mixed before it is placed in your tooth, all the mercury is bound chemically to the silver, and so there is no free mercury in your filling. Over time, normal grinding and wearing down of an amalgam filling can release a small amount of free mercury, which is so small that it cannot be traced in the body and has no effect on the body. In fact, research has shown that if someone had an amalgam filling in every tooth in their mouth, and ground their teeth against each other for 12 hours every single night, the amount of free mercury that would be released is less than that from eating 1 can of tuna fish a week. An amalgam filling stays in your tooth based on the shape of the cavity preparation; it is essentially locked in place mechanically, but it does not bond chemically to your tooth. Amalgam is a very strong material and resists compressive forces – in fact, it is stronger and more resistant than tooth structure, which is why sometimes teeth with old amalgam fillings crack or break but the amalgam stays intact. When you bite hard against an amalgam filling, the filling is very hard and does not flex, but the tooth structure can flex underneath it; this can lead to cracks in tooth structure under and around amalgam fillings.
Fillings & Cosmetic Dentistry
Composites are tooth colored restorations that are bonded directly to your tooth structure. Today’s composites are not quite as hard or resistant to compressive force as amalgam, but they are very close. Composites flex more similarly to tooth structure, absorb biting forces better, and therefore do not cause cracks in the tooth structure around the filling. In fact, the composites are chemically bonded into the tooth structure, so they strengthen the tooth by holding the walls together instead of wedging the cavity walls apart like amalgam. Rarely, some of the chemicals in the bonding agents and in composites can irritate the tooth and result in transient sensitivity in the tooth after a filling. In order to minimize this, we often use bases or liners underneath our composite fillings. Composites come in many different shades and can often be matched perfectly to your tooth so that they are visually undetectable. The formation of the chemical bond that holds composite fillings in your teeth is technique sensitive – this means that the bond can be disrupted by things like blood, saliva, or water. The tooth structure needs to be clean and dry in order to bond to the composite.
In instances where the tooth cannot be kept dry during the restoration, or when the filling is being placed on the root surface, a resin-modified glass ionomer filling material would be preferred. These materials bond better on root surfaces and in wet environments. Resin modified glass ionomers also release fluoride at the filling margin which helps prevent future cavities.
