AMALGAM FAILURES

WHERE IS THE FAULT: IN THE ALLOY OR IN THE OPERATOR?

¹ Chicago, Illinois

Proportions of alloy and mercury need not be exact, but mercury should always be in perceptible excess during the mixing. A considerable excess during the mixing will do no harm, but a slight insufficiency is dangerous.

The best and only dependable guide to insure a complete mix and adaptable plasticity is accurate timing.

Plasticity free from crepitus during the procedure of orderly packing is imperative to make a non-leaking filling.

Fillings must be placed and built by tamping (not condensation). Following tamping we condense to remove the unattached tin and excess mercury, and drive and wedge the amalgam into pressure-contact with the cavity walls.

Orderly packing and stepping the cavity walls has proved the best procedure to insure equal condensation and the most complete removal of excess mercury, and is the most effectual technic to make air-tight adaptation as the final detail of the packing procedure.

The use of a good alloy does not guarantee a good amalgam. The dentist makes the amalgam, not the manufacturer of the alloy, and the amalgam is only as good as the mixing and packing process applied by the operator. Weak packing force will always make a soft, unstable filling, however good the amalgam used. A soft filling loses its margins by wear, developing the black ditch, which many have considered due to spheroiding or to excessive shrinkage.

However good the alloy used, we must pack with an orderly applied force of nine to sixteen pounds to make a uniformly perfect filling.

The strength and stability of the finished filling is in proportion to the amount of tin and excess mercury expressed, in the packing. The more tin and mercury expressed, the stronger and more stable the filling.

The average sized mesio- or disto-occlusal cavity filled with a medium- or slow-setting alloy will require as much of the operator's time as would be taken when restored with a gold inlay. If this be true, how can we justly charge a reduced fee for our amalgam service?

Average sized proximo-occlusal fillings can be inserted and finished at one sitting of fifteen to twenty-five minutes when quick setting alloys are used. The same cavity filled with a medium- or slow-setting alloy would require forty to sixty minutes, necessitating a second appointment to make an equally good finish. To make it possible to collect a just fee for our professional service, under these circumstances, we must learn to use the quick setting alloys to reduce justly the cost of our service to the public.

Incomplete mixing and insufficient plasticity will make a leaking filling that may be strong in its resistance to crushing stress and flow if packed with force.

Weak packing makes a soft filling that will develop every fault characteristic of bad amalgam work.

A correct amalgam procedure, that will assure a uniformly perfect filling, is dependable upon the application of the following order of procedure: Proper cavity preparation; the use of a perceptible excess of mercury in the mixing;thorough mixing for two to three minutes; a plasticity free from crepitus during orderly packing, for all except small and shallow cavities; thorough, orderly, and forcible packing; stepping the cavity walls; proper proximal and occlusal form and finish; a firmly-held matrix wedged at the gingiva, when the use of one is necessary; protection of the pulp from packing pressure in all deep cavities.

You may jar amalgam into an impression, using the pressure of the finger as you jar it for five to ten seconds, and make a 100 per cent perfect model without failure; but you cannot secure air-tight adaptation by this procedure, because it will not develop pressure-contact of the amalgam to cavity walls. We must drive and wedge amalgam against cavity walls to secure pressure contact.

It has been the germicidal power of most good amalgams that has saved the teeth, not our operative skill and care.

Amalgam is the most generally used and the most abused of filling materials, representing more than 50 per cent of the income of the average dentist. Why not honor our profession by its more intelligent use?