Why dentists are abandoning amalgam
1. When first invented, amalgam was great stuff. It still is, in fact, but it isn’t any greater now than it was 150 years ago. Technical improvements in it over the years have made minor differences in its physical properties, but other than the addition of trace elements to the mix for the purpose of reducing tarnishing, speeding the setting time and changing minor physical parameters, it really hasn’t changed much since it was invented. On the other hand the technology involved in composite formulations has made tremendous strides in improving the wear, strength, appearance, setting characteristics, water miscibility, and numerous other less obvious qualities. They continue to improve yearly. The newest generation of composite filling materials has finally overcome most of the difficulties which prevented their widespread use in restoring back teeth.
2. Composite fillings are routinely BONDED to the tooth structure. This takes the place of the water resistant layer of corrosion that seals amalgam fillings. It also helps to retain the filling inside the tooth while amalgam fillings depend on the use of undercuts in the cavity preparation to retain them. Amalgam fillings must engage undercuts within the cavity preparation so they will not dislodge. Amalgam also requires a minimum depth of a millimeter and a half in order to form its crystalline structure while composite fillings have no minimum depth. (If they are not deep enough, the amalgam will be too thin and tends to crack.) The use of bonded composites has made possible the use of very small fillings that do not have the mechanical retention necessary to retain an amalgam. It has also made possible the use of shallow and thin cavity preparations which do not require the use of anesthetic to cut due to their very small size.
Note that it IS possible to bond amalgam fillings to the tooth. However, the process takes so long that the cost of such a bonded amalgam filling is actually greater than the cost of the comparable bonded composite. While most US dentists still use amalgam, very few of them bond it to the tooth.
3. There is NO comparison between the appearance of a composite filling and an amalgam. The results are so aesthetically superior, that most people opt for the slightly more expensive composite over the less expensive amalgam. Since many people have quite a few fillings in their back teeth, the difference between a mouth with composite fillings versus the same mouth with amalgams is striking. After a year or so of offering both to my patients and explaining these differences to them, I discovered that my amalgam was approaching its maximum shelf life, so I discarded it and never bought any more.
4. Composite restorations can be repaired while most amalgam restorations cannot. A tooth has five surfaces that can become decayed. The size (and cost) of a filling is judged by the number of surfaces it encompass. When a filling covers, say, 2 surfaces, that leaves three other surfaces untouched. But if the patient returns a year or two later with decay in one of those other surfaces, it is usually necessary to replace the entire amalgam that was done previously in order to place one that encompass the new decay. But since composite bonds reasonably to itself, the dentist can usually simply add the new surface to the old filling and avoid the trauma to the nerve that replacing the entire filling would entail. It is also less expensive to the patient. (In order to save time, many dentists DO repair old amalgam fillings, but the interface between the old and new materials is not chemically sealed as it is when repairing composite fillings.)
5. Before the advent of composite filling materials, many damaged teeth could not be repaired unless a root canal, post and core and crown were done. This was because the working characteristics of amalgam required stringent techniques which were absolutely necessary, but not always achievable under real circumstances. Once modern composites became available, it became possible to repair some of these teeth using “freehand” techniques impossible with amalgam. Repair of these teeth is often not technically “perfect”, but it offers an affordable alternative to the stark choices of extraction or a very expensive series of steps like root canals, posts and crowns.
Q. Should I have all my amalgam fillings replaced with composites?If aesthetics is of major concern to the patient, then you should request the replacement of all your amalgams with composites, or porcelain crowns. But beware! Every time you remove one filling and put another in its place, you run the risk of killing the nerve of the tooth and then needing a root canal