Simple Cavities upon Exposed Surfaces - Part 2
Caries rarely attacks the morsal edge of the incisors and cuspids, except as the result of imperfections in development, from mechanical abrasion, or from traumatic injuries which fracture the enamel. Consequently the operation of filling is usually confined to artificial cavities, made -for the purpose of protecting the morsal edges against the loss of tooth-substance from mechanical or chemical abrasion, or for lengthening the teeth when it is desired to "open the bite."
Cavities prepared for this purpose must have strong retentive form, as fillings of this class are constantly subjected to great stress. Many operators are in the habit of inserting a couple of "Mack" screws in the artificially formed cavity, one near each extremity. These add very greatly to the retentive strength of the cavity and make it very difficult to dislodge such a filling.
Care must be exercised in setting the screws not to encroach upon the pulp.
Cohesive gold only should be used for building up these fillings. It may be either foil or crystal gold, as suits the fancy or the ability of the operator to manipulate one form of gold better than another. In making the choice he should always select that form of gold with which he is confident the best filling can be made. In starting the filling it is advisable to begin at one extremity of the cavity by anchoring the gold in the undercut or retaining-pits, then repeat the process in the other extremity, and afterwards connect them together by a narrow ribbon laid upon the bottom of the cavity and folded back and forth, each fold being thoroughly condensed upon the preceding one, care being taken to accurately fill the undercut before the building process is begun.
Fillings in these locations must be thoroughly condensed with the mallet in order that they may obtain the greatest hardness possible to pure gold, as they are subjected to severe wear, which might result in abraded edges and flaking of the layers of gold.
Platinum-gold in narrow ribbons of No. 20 or No. 30 is preferred by some operators for all of that part of the filling which extends, beyond the walls of the retaining cavity. The Bonwill electric 'mallet or the/engine mallet are invaluable for packing the gold in these cases.
Cavities occurring in the fissures and sulci of the morsal surface of the bicuspids and molars are the most accessible, and from their location offer the least difficulty to the introduction of gold fillings. Such cavities, if prepared with perpendicular or slightly undercut walls, need no other retentive shaping to insure firm anchorage of the filling. These cavities can be most rapidly and substantially filled with non cohesive foil; in fact, this is one of the most favorable locations for the use of non-cohesive foil. The gold can be introduced in the form of narrow ribbons, small cylinders, or small spindle-shaped pellets.
In introducing ribbons, one end should be grasped with the foil-pliers and carried to the bottom of the cavity, at that point which is farthest from the operator,- this is a safe rule to follow in starting all classes of fillings,- and secured in place by a point held in the left hand, while with the pliers the ribbon is folded upon itself and carried again to the bottom of the cavity, and the fold packed firmly against its walls with a wedge-shaped,or a foot-shaped.plugger, but permitting the outer end of the ribbon to project a little beyond the walls of the cavity. A second ribbon is now introduced in the same manner and packed against the wall nearest the operator. A third ribbon is introduced in the same manner and packed against the two opposite uncovered walls, and the operation completed by driving ribbons of cohesive foil into the filling, and finishing with heavy foil.
Or, cylinders may be introduced instead of ribbons, placing them on end in the cavity and packing them against the walls, finishing in the centre with a hard-rolled pellet/and then thoroughly condensing the projecting ends of the cylinders. Or the spindle-shaped pellets may be used, the tip of one end of which should be annealed by passing it in the flame of the spirit-lamp, and the annealed ends allowed to project slightly beyond the walls of the cavity. These are packed against the walls of the cavity after the same manner as cylinders, the centre finally receiving a pellet of cohesive gold. The ends of the pellets which project beyond the walls of the cavity are then condensed, and the surface finished with mats of cohesive foil, which welds without flaw to the surface formed by the annealed ends of the pellets. By this method the danger of the surface of the filling scaling off is obviated. Scaling off of the surface of the filling often occurs when the union of the cohesive gold with the. balance of the filling is only mechanical. All fillings upon the morsal surfaces of the teeth should be made as hard as possible by thorough but judicious malleting.
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 |