Compound Cavities - Part 1
Compound cavities are those which involve two or more surfaces of the tooth, and, by reason of this, present the greatest difficulties in the operation of filling.
Cavities which, involve the mesio-labial and disto-labial surfaces of the incisors and cuspids are the least difficult of the series to fill, from the fact that an unobstructed view can be obtained of every part of the cavity by direct light and unaided vision. Each portion of the cavity should be so shaped as to give it an independent retentive form. Cohesive foil is best for filling this class of cavities, as the welding property is valuable in binding the fillings together, giving to them a proper contour and a more highly finished surface. Foil cut in ribbons and freshly annealed or crystal gold should always be used in this class of cavities. In starting these fillings the general rule of beginning all fillings at the point farthest from the operator holds good. When the approx'imal cavity is about two thirds full the filling in the labial cavity should be started and connected with the approximal filling, and the whole then treated as one filling; in this way both fillings are bound solidly together, and dislodgement is impossible except by fracturing the tooth.
As these fillings are constantly exposed to view, the greatest pains should be taken to give them an artistic form and finish by restoring the natural contour of the tooth, avoiding peculiar marginal lines, and so finishing the surface of the gold as to make it as little conspicuous as possible.
Mesio-lingual and disto-lingual cavities in the incisors and cuspids may be filled in precisely the same manner as those cavities last described, care being taken that the retentive form of each cavity is such as to secure independent anchorage, and the gold so prepared that its welding property will be at its maximum degree.
Cavities involving the mesio-morsal and disto-morsal surface of the incisors and cuspids are among the most difficult fillings to make substantial by reason of their form and exposed position to stress and leverage. The greatest care must therefore be exercised in securing firm anchorage, and if this cannot be done within the formed cavity, it should be extended in some direction which will secure this without unnecessarily weakening the tooth.
The bottom images represent such methods of extension for anchorage. In teeth having a broad morsal edge, additional anchorage may be secured by slightly grooving the labial and lingual walls at this point.
Cohesive gold is best adapted to the requirements of such a filling, and used in such form as to preclude the possibility of the gold clogging underthe instrument, as air-spaces resulting from imperfect consolidation of the foil are an element of weakness in the filling.
The filling should be started at the cervical border and built up from this point, keeping the surface of the gold as nearly fiat as possible, and restoring the contour as the filling progresses, care being taken to secure perfect adaptation of the gold to the labial and lingual enamel margins. An electric or engine mallet greatly facilitates the rapidity of the operation, and insures more perfect consolidation of the gold than can be obtained by band-pressure or the hand-mallet without the expenditure of an infinite amount of time and labor. To guard against bruising, or flaking of the morsal edge of the filling, thorough condensation of the gold must be secured. Heavy foil, No. 20 or No. 30, if each piece'is thoroughly welded to the surface of the filling before another is added, will make the hardest surface obtainable with gold.
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 |