Tin and Gold - Part 2
Fillings which present rough surfaces or imperfectly finished margins invite' recurrence of caries, by reason of the fact that these imperfections give lodgement to alimentary debris, where if it remains undisturbed it is soon attacked by the zymogenic bacteria, lactic acid is formed, and sooner or later secondary caries is established. The importance, therefore, of perfectly finishing all fillings cannot be over-estimated if the best results are to be obtained.
In order to secure a surface in a gold filling that will receive a fine finish thorough condensation is of the greatest importance. Fillings which are imperfectly condensed cannot be made to take a smooth and highly polished surface, while after a little time the surfaces exposed to wear will become rough and pitted.
In order to insure a good surface that will finish smoothly, many operators are in the habit of using heavy foils for the last few layers of the filling. After the surface has been thoroughly condensed the burnisher should be vigorously applied, especially to the margins, in order to obtain perfect contact of the gold at these lines and to secure a compact and hard surface. Hand-burnishers or those revolved by the dental engine may be used for this purpose. The latter are made of various shapes, some having smooth surfaces, others corrugated surfaces, as shown in images.
In all fillings the cavity should be filled a trifle fuller than the margins of the surface in which they are located, that there may be opportunity for a proper shaping of the surface of the filling to harmonize with the normal lines of contour.
This shaping or dressing of simple cavities in the morsal surface of the bicuspids and-molars may be accomplished by finishing-burs.
The "cut" of these burs is much finer than that of cavity burs, and gives the urface of the filling a finish similar to that given to a flat surface with a fine file.
The gold should be cut away until the margins of the cavity have been reached and all overlapping portions have been removed. The occlusion of the teeth should next be noted, and the surface of the filling made to conform to the occluding points or eminences of the morsal surface of the opposing teeth. As soon as a natural occlusion is obtained the surface of the filling should be polished, using fine powdered pumice and water, with a suitable wood point, as shown in the bottom image, mounted in an engine porte-carrier. If the operator desires to give a burnished surface to the filling, this may be accomplished with a suitable engine-burnisher, lubricated with a solution of fine toilet soap in water.
This is an instructive summary of the qualifications and the duties of the present day Dental Assistant -- The Diplomat standing between the dentist and lost income. | read more |