Compound Cavities - Part 3
These are no different from the class just described except in their location, which adds very much to the difficulties in filling. All fillings of this class have to be made by the aid of reflected light, while the progress of the operation is viewed from the reflected image in the mirror.
When the cavities are located in the posterior part of the mouth, as, for instance, in the second molars the difficulties of obtaining unobstructed light and vision are considerably enhanced.
The operation of filling may be greatly simplified by the adjustment of a suitable matrix, thus converting a complicated operation into a simple one.
If the cavity has been given a proper retentive form, grooves and retain-ing-pits will not be needed, and the filling may be started with non-cohesive cylinders, mats, or pellets, thoroughly condensed against the cervical border and the matrix, which must be firmly fixed in position. After the cervical third of the cavity has been filled with non-cohesive gold, the balance can be completed with cohesive gold in the manner described in the preceding class.
Cavities occurring upon the morsal and buccal surfaces unite to form : morso-buccal cavities. This class of compound cavities is usually confined to the lower molars and the upper third molars. They can usually be given a good retentive shape without forming grooves or retaining-pits. In the deep cavities non-cohesive gold can be used for the base of the filling and then finished with, cohesive foil or crystal gold. In the shallower cavities it is best to use cohesive gold throughout subjected to great stress and wear 5 they should therefore, be made as solid and hard as possible, that they may not be dislodged or battered by the occlusion of the opposing tooth.
Cavities involving the morsal and lingual surfaces are usually confined to the first and second superior molars.
From the fact that these cavities are generally shallow, they should be filled throughout with cohesive gold. Their position makes them fairly easy of access. The morsal cavity is usually the deepest, and may be quite large, while the lingual cavity is narrow and shallow. In this case the morsal cavity being the largest should be filled first, the smaller cavity and the channel uniting them being filled by carrying ribbons of foil, which are first attached to the main filling, over into the channel and to the cervical extremity of the lingual cavity.
Cavities situated upon the mesial, distal, and morsal surfaces of the bicuspids and molars, uniting to form mesio-disto-morsal cavities, are of not uncommon occurrence. These cavities might be filled by the methods described for filling the same class of cavities occurring in the incisors and cuspids. Such operations, however, may be greatly simplified when made in the bicuspids and molars by the adjustment of a matrix to the distal surface. The band-matrix is sometimes used, but this is not so satisfactory, as it obstructs the light and vision to a considerable extent. Non-cohesive gold can be used to good advantage in forming the base, while cohesive foil should be used for the bulk of the filling.
The filling should be started with a large, soft-rolled cylinder placed at the disto-cervical border and malleted into place. Others may be added until the entire floor of the cavity and mesio-cervical border are well covered, after which cohesive gold may be used to complete the filling.
When the buccal and liggual walls are frail and likely to fracture under the stress of mastication, the cusps may be cut away and the whole morsal surface restored with gold. This operation decreases the liability to fracture and, if well done, restores the tooth to its original form and preserves it for many years of usefulness.
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