THE PROXIMAL GOLD FOIL FILLING
INVOLVING THE INCISAL ANGLE
A. B. BUTTER, D.D.S., R. O. GREEN, D.D.S., and W. J. SIMON, D.D.S.,
Jour. A.D.A., Vol. 30, December t, 1943
TO those interested in gold foil, cavities in the proximal surfaces of the incisor teeth which involve the incisal angle present interesting possibilities. The chief objection to this type of filling from the patient's point of view is the display of gold. While it is conceded that the operation involving the incisal angle is necessarily extensive, it is possible, by judicious cutting, to develop the outline form so that the filling, when finished, will be far less conspicuous.
Contrary to the teachings of some operators, the proximal labial margin should be a straight line from the incisal edge to a point beneath the free margin of the gingiva parallel to the long axis of the tooth, and as close to the embrasure as is consistent with the principles of extension to areas of relative immunity. (Fig. 1, A.) If this cut is made otherwise, as, for instance, parallel with the proximal surface of the tooth, there will develop at the incisal angle an unsupported area of enamel which will prove a menace in condensation, and the finished result will be out of harmony with the tooth.
The amount of tooth structure cut from the incisal edge will depend on the type of tooth and the stresses placed upon the incisal angle. Ordinarily, the incisal cut is carried two-thirds of the way across the incisal edge (Fig. 1, B), thus securing a greater leverage for the filling, which will be anchored by an incisal retention form. A cut which is not past the middle lobe of the tooth places the retention form in a position which may embarrass the pulp.
By crossing the incisal edge labio-lingually, at an angle of 450, additional resistance to masticatory stresses from the lingual aspect is obtained. (Fig. 1, C ) This cutting can be done with a carborundum stone. The proximal lingual wall can be cut down to a point below the free margin of the gingiva with a straight chisel. (Fig. 1, D.) The proximo-linguo-incisal angle is well rounded off, as indicated by the dotted line in Figure 1, D.
Fig. 1. A, proximo-labial margin parallel to long axis of tooth. B, incisal cut carried approximately two-thirds of way across incisal edge. C, crossing incisal edge at an angle of 450 to obtain additional resistance to masticatory stresses from the lingual aspect. D, proximo-linguo-incisal angle well rounded off.
In cutting across the incisal edge, the stone is held in such a manner that the lingual enamel plate is reduced more than the labial plate. (Fig. 2, A.) Because of the stresses upon the tooth, the shape of the tooth and the thickness of the labial and lingual enamel plates, it is not possible to state dogmatically how much of the lingual plate should he removed. Generally speaking, it is at least twice as much as the enamel removed front the labial plate. One of the methods of reducing the lingual plates is to undermine the lingual enamel with a small single cut fissure bur. (Fig. 2, B.) With the chisel, as illustrated in Figure 2, C, the enamel is cleaved away, to effect the "incisal step." Some operators reduce the lingual enamel plate with small inverted cone stones, as shown in Figure 2, D. The "incisal step" is to be finished smoothly with special burs, stones, chisels and cuttle disks when accessible.
Fig. 2.—A, initial reduction of lingual enamel plate. B, undermining of lingual enamel plate. C, cleaving away of undermined enamel. D, finishing "incisal step."
The proximal portion of the cavity should he extended far enough to free contact with the adjacent tooth. The gingival seat should either be flat (Fig. 3, A) or should follow somewhat the curvature of the cervical line. An inverted cone bur is useful here provided care is taken that it is not brought too far labially or lingually. Primarily, the gingival seat must be so constructed that it presents a flat surface at least at right angles to the line of incisal stress.
Fig. 3.—A, gingival seat. This should be flat. B, gingivo-axial line slightly acute, as is preferable.
Substantial retentive resistance form, which is necessary for this filling, is secured by means of two point angles at the gingival portion and an incisal retention form at the far end of the incisal step. The gingival point angles are started with a small single-cut fissure bur. (Fig. 4, A.) The direction of the gingival retention forms are such that they all times to be in dentin between the bisect the point angles. The bur is at pulp and the dentino-enamel junction. The depth to which this bur is projected is a matter of judgment, depending on the size of the cavity and the stresses to be exerted on the filling.
The bur is also drawn up the labio-axial and linguo-axial line angles approximately a third of their length. These line angles are now emphasized and accentuated by the use of small monangle hoes. (Fig. 4, B.)
Fig. 4.—A, gingival point angles started with small single cut fissure bur. B, line angles accentuated by means of rnonangle hoes
Probably not more than a third of the linguo-axial line angle can be used for retentive resistance forms, but that portion which is available must be utilized to the fullest extent.
The labio-axial line angle, while it may be generally obtuse, should be prepared in a definite manner. For example, Figure 5, A is a transverse section at the gingival seat, showing a retentive labio-axial and linguo-axial line angle which is definitely an acute angle. At the junction of the gingival third and the middle third, the labio-axial and linguo-axial line angles approximate a right angle. (Fig. 5, B.) In the middle third (Fig. 5, C), both line angles are obtuse and, in the incisal third (Fig. 5, D), the line angle fades out, leaving as much dentin as possible to support the enamel plates.
Fig. 5.—A, labio-axial and linguo-axial line angles, which are definitely acute angles. B, line angles approximating right angle. C, line angles obtuse. D, line angles fading out.
The incisal step presents a flat ledge on the lingual aspect, which is all-important in the resistance of the filling to masticatory stress. The labial wall of this step is cut parallel with the long axis of the tooth, a triangular portion of dentin remaining to support the labial plate. Retention is further secured by cutting a rectangular form at the far end of the incisal step. Usually, this retention is made with a small single cut fissure bur slightly undercutting the mesial and distal walls as indicated by the letter X in Figure 3, B. This incisal retention form should he cut as large as is consistent with the area involved. Generally, it is made too small for the purpose for which it is intended. The incisal retention form should he directed gingivally parallel to the labio-incisal plate of enamel, keeping well within dentin and away from the lingual enamel plate. (Fig. 6.)
The cavosurface angles of the cavity should he planed and disked when accessible. The gingival ,cavosurface is beveled with a monangle hoe. Any other part of the cavity in which there is any doubt regarding unsupported enamel is also beveled. There should never be any angles as such in the outline form to disturb the harmony of tooth outline form.
Fig. 6. Incisal retention form directed gingivally parallel to labio-incisal plate of enamel.
The completed cavity is presented in Figure 7, from various aspects in recapitulation of some of the key points of the cavity preparation.
Fig. 7.—A, proximolabial aspect of finished cavity, showing proximolabial margin parallel to long axis of tooth and incisal cut carried approximately two-thirds of way across incisal edge. B, proximal aspect, illustrating "incisal step" and accentuation of labia-axial and linguo-axial angles from retention forms. C, proximolingual aspect; The proximolingual incisal angle is well rounded off. D, proximo-incisal aspect of finished cavity, showing incisal retention form and acute gingivo-axial line angle.
CONDENSING AND FINISHING
To condense-gold foil properly, the force should be in as nearly a direct line as possible to the long axis of the tooth, so that the peridental membrane may resist the pressure demanded in filling. The plugger points should be cleansed frequently and the serrations freed of gold adhesions. The amount of force applied in condensing gold foil will be governed not only by the surface area of the plugger points, but also by the tolerance of the patient. In the cavity preparation herein described, the approach is toward the incisal aspect. Regardless of the type of plugger point, the gold foil is being wedged continually between the labio-axial wall and the linguo-axial wall. (Fig. 8, A.) The foil should be stepped continually from the center of the mass of previously condensed gold foil toward one of the walls.
The gold foil is started in both of the gingival point angles, building up the axial wall at an angle of 450 (Fig. 8, B), care being taken to carry the foil out to the full contour as we proceed. If this is not done at this time, it will be difficult to go back and fill in the deficiencies later. When the filling has reached the "incisal step," the foil is started in the incisal retention form and condensed across the incisal to meet the proximal portion. (Fig. 8, C.) The incisal portion and the proximal portion are welded together and, by maintaining condensation in line with the long axis of the tooth, the filling is built up to full contour. (Fig. 8, D.)
After burnishing the gold over the margins, the surplus is trimmed off with knives, chisels, files, stones, disks and strips and the filling brought to shape and contour. In the final finishing of the proximo-incisal gold foil, it is essention not only to recover the original esthetic outline created, but to restore the harmonious proportions in the varying curves and angles of the tooth.
There are other methods of treating cavities in the proximal surfaces of incisors in which the incisal angle has become involved. Every operator wishes to display as little gold as is commensurate with the stresses placed upon the filling. In cases of marked overjet, it is possible to prepare cavities which do not display any gold in the incisal edge. A cavity of this type is illustrated in Figure 9, A and B.
In delicately shaped incisors with a short labio-lingual diameter, the operator will experience difficulty in finding sufficient dentin between the labial and lingual plates of enamel for the incisal retention form. In this type of case, the incisal retention form is cut through the lingual enamel plate and undercuts are made in the mesial and distal wall of the incisal dovetail in dentin for retention. (Fig. 10)
In incisors with a short labio-lingual diameter, the incisal retention form is cut through the lingual enamel plate and undercuts are made in the mesial and distal walls of the "incisal" dovetail in dentin for retention. (Fig.10) Another method of treating a proximal cavity which involves the incisal angle is to prepare the proximal portion in the orthodox manner, but, in place of cutting down the incisal edge for resistance, prepare a lingual dovetail for additional anchorage and resistance. (Fig. 11 ) This cavity can be prepared only in teeth which have a marked labio-version. In teeth with a linguo-version, it is definitely contraindicated. This lingual dovetail should be placed as close to the incisal edge as is consistent with the bulk of the tooth structure to prevent undue leverage from damaging the incisal angle.
In short teeth that are thick labio-lingually, it is occasionally possible to prepare a cavity involving the incisal angle without any special treatment other than establishing a bulky incisal retention form. (Fig. 12.) The involved incisal angle is slightly rounded to protect the enamel rods on the incisal edge. This preparation can be used only in those cases in which the lateral excursions of the opposing teeth do not place undue stress on the filling.
While the preparation illustrated in Figure 12 is considered in certain cases, it has been observed that gold foil under heavy stress has a tendency to pull away from the axial wall and to open at the incisal margin.
In preparing a proximo-incisal cavity for gold foil in the lower incisors, a consideration of masticatory stress is important. In cases of overbite, both normal and abnormal, it will be necessary to remove more of the labial enamel plate than the lingual enamel plate in lower incisors. (Fig. 13.)
The anatomic form of a lower incisor is of such nature that frequently the linguo-axial wall need not be extended for the access desirable in an upper incisor. Likewise, in lower incisors, it is the linguo-axial line angle that is accentuated in much the same manner as the labio-axial line angle in upper incisors. In the lower incisors, the incisal retention form is placed in dentin between the labial enamel plate and the lingual enamel plate. This requires discretion, since it is very easy to involve a pulp in a lower incisor.
The cavity illustrated in Figure 13 is considered the normal cavity. It too is subject to variations depending on the form of the tooth in question and the relationship of the tooth to the adjacent and opposing teeth.
In the past, the masters of the gold foil art have shrouded the proximo-incisal foil cavity preparation with a veil of complexity. In reality, the proximo-incisal foil cavity is less difficult to prepare than the strict proximal foil cavity, largely because it is readily accessible. All gold foil cavity preparation is based upon fundamental principles, which may be varied in singular cases. The condensing of gold foil into a proximo-incisal cavity is exacting, requiring skill which is acquired only by perseverance. Perfectly condensed, properly contoured gold foil fillings in a proximo-incisal cavity of harmonious proportions have no equal.
This Article was scanned & edited by Dr. John R Sechena 11/2004