Acrylic resin teeth: An aid in f~xed partial denture construction Dominick C. Larato, D.D.S.*
United States Veterans Administration Hospital, New York, N.Y.
V a l u a b l e chairside and laboratory time can be saved by using stock acrylic resin teeth in crown and fixed partial denture procedures. Acrylic resin teeth can be formed into a basic fracture-proof pattern for casting gold pontics and post crowns. Alteration of the anatomy of stock acrylic resin teeth makes them useful in constructing temporary crowns and partial dentures, and in repairing and creating veneer facings. CONSTRUCTING A PATTERN FOR A CAST CROWN WITH A POST
Prepare the root face and canal for a cast post and crown. Select a plastic dowel which fits loosely in the canal, and extends two-thirds of the length of the root preparation, and 5 to 6 mm. beyond the canal orifice. Lubricate the canal with a thin film of Microfilm.t Cover the plastic dowel with a thin layer of sticky wax. Apply softened inlay wax over the sticky wax~ and insert the dowel into the canal while the wax is soft The wax impression should be an accurate registration of the shape of the prepared canal. Measure the length and width of the space to be filled by the finished crown. Select an acrylic resin tooth of the desired shape and a size to correspond with these recorded measurements. Grind the resin tooth so it is hollow (Fig. 1, A and B). If a tooth of the right size is not available, a larger tooth is reduced to the desired size. Fill the hollowed stock tooth with soft cold-curing acrylic resin, and seat the crown firmly over the root face and plastic dowel (Fig. 1, C). Allow the resin to set, and then remove the crown and post as a unit. Remove any excess resin from the gingival collar of the crown. Any deficient areas in the impression are corrected by adding softened inlay wax or cold-curing resin, and reseating the pattern on the tooth. For a veneer cro~vn, a window is prepared with undercuts, and gold loops are added for retention (Fig. 1, D and E). The pattern is then sprued, invested, and cast as one unit. ~Career Resident in Periodontia. ~'Kerr Manufacturing Company, Detroit, Mich. 346
Acrylic resin teeth
Volume18 Number 4
A, A stock acrylic resin tooth. B, A proximal view of a stock acrylic resin tooth. The dotted lines indicate the part of the tooth to be hollowed out. C, The post crown pattern in position; (a) hollowed acrylic resin tooth, (qsr) cold-curing acrylic resin, (d) plastic dowel, (w) inlay wax, (r) root, and (rc[) root canal filling. D, The labial view of a post crown pattern; (gl) gold loops, (wi) "window" in the acrylic resin pattern, (w) inlay wax around, and (d) the plastic dowel. E, A proximal view of a post crown pattern; (wi) window.
CONSTRUCTION OF A TEMPORARY POST CROWN
Use the same measurements as for making the pattern, and select and hollow out another acrylic resin tooth. Fit a stock metal dowel into the prepared root canal so that it extends 5 to 6 ram. beyond the canal orifice. Fill the crown with cold-curing acrylic resin of the same color as the tooth, and seat the crown over the dowel until the acrylic resin is set. Remove the post crown as a unit, and trim away the excess resin. Temporarily cement the crown and post in the canal with a zinc oxide and eugenol cement. CONSTRUCTING TEMPORARY PARTIAL DENTURES WITH ACRYLIC RESIN TEETH
Mount the diagnostic casts on an adjustable articulator. Select the proper stock acrylic resin teeth to replace the teeth missing from the diagnostic cast. Roughen the ridge laps of the acrylic resin teeth, and add cold-curing acrylic resin to the roughened surface. Shape this resin to make a ball contact between the acrylic resin tooth and the edentulous surface of the diagnostic cast (Fig. 2, A, B, and C). Close the articulator and check the occlusion. Attach the gingival ends of the acrylic resin teeth to the cast with sticky wax, and then join the ends at the contact areas by means of cold-curing acrylic resin. After the acrylic resin is set, cut a continuous trough into the occlusal surface of the pontics with a No. 37 inverted cone bur (Fig. 2, D ) , and let cold-curing acrylic resin flow into the trough, thereby forming a reinforcing bar of acrylic resin (Fig. 2, E). After the abutment teeth are prepared, make a sectional impression (in irreversible hydrocolloid) of the teeth and acrylic resin pontics on the diagnostic cast (Fig. 2, F). Remove the impression and place the acrylic resin teeth into it. Remove
j. Pros. Dent. October, 1967
A, A proximal view of a stock acrylic resin tooth. B, Cold-curing acrylic resin (qsr) is added to the ridgelap of the tooth in order to form a ball contact on the ridge. C, A stock acrylic resin tooth with the modified cervical end. D, An occlusal view of the joined stock acrylic resin teeth. The dotted lines outline the part to be cut out to form a trough. E, Cold-curing acrylic resin is painted into the trough to form a continuous bar. F, The acrylic resin teeth (shaded areas) joined together and filling the edentulous region.
any impression material that separates the acrylic resin teeth from the abutments. Paint a thin shell of cold-curing acrylic resin into the impression of the unprepared abutment teeth, and attach the resin to the acrylic resin pontics. Allow the resin shell to set, and then let cold-curing acrylic resin flow into the abutment shells, and seat the impression firmly in the patient's mouth until the resin becomes doughy. Remove the impression, and then reseat it for a few seconds. Repeat this step until the resin is fully set. Separate the acrylic resin fixed partial denture from the impression, and check the occlusion in the mouth. Remove any flash, and add cold-curing acrylic resin to any surfaces where it is deficient. Polish all rough surfaces prior to temporary cementation. IMMEDIATE TEMPORARY FIXED PARTIAL DENTURES FOR ESTHETICS When a number of anterior teeth are to be removed and replaced by a fixed restoration, a temporary fixed partial denture can be made by using acrylic resin teeth. Cut the teeth that are to be extracted from the diagnostic cast (Fig. 3, A), and carve the cast in this region as you would for an immediate denture (Fig. 3, B). Select acrylic resin teeth that correspond in size, shape, and color to the natural
Acrylic resin teeth
Vo]umel8 Number 4
Fig. 3 A, A pre-extraction cast showing the abutment teeth, and the incisor teeth diagnosed for extraction. B, The incisor teeth have been removed from the cast. C, The stock acrylic resin teeth (shaded areas) are waxed in position on the cast to construct the immediate temporary fixed partial denture.
teeth. Grind the ridge laps of the teeth to fit the form of the cast, and fasten the teeth in position on the cast with sticky wax at their cervical ends. Then allow cold-curing acrylic resin to flow between the teeth at the contact areas. This joins the ponfics together (Fig. 3, C). Cut a continuous trough into the incisolingual aspect of the resin teeth with an inverted cone bur, and let cold-curing acrylic resin of the same color flow into the trough, and allow the resin to harden. Prepare the natural abutment teeth, and then extract the teeth to be replaced. After bleeding has stopped, make an irreversible hydrocolloid impression of the modified diagnostic cast including the unprepared abutments, with the acrylic resin teeth in place. Remove the impression from the cast with the acrylic resin teeth in place in it. Then clean out any impression material from between the acrylic resin teeth and the abutments. Paint a thin shell of cold-curing acrylic resin into the impression of the unprepared abutment teeth in order to form the outer surface of the temporary abutment crowns, and to attach the resin to the pontics. Allow the resin to set, and then let cold-curing acrylic resin flow into the acrylic shells, and seat the impression in the patient's mouth. When the resin reaches the doughy stage, remove the impression, and then reseat it for a few seconds. Repeat this procedure until the resin is fully set. Remove the temporary restoration from the impression, and trim away the flash and polish. The fixed
J. Pros. Dent. October, 1967
partial denture may now be temporarily cemented over the prepared abutment teeth with a zinc oxide and eugenol temporary cement. PATTERNS FOR PARTIAL DENTURE PONTICS MADE FROM STOCK ACRYLIC RESIN TEETH
Select a stock acrylic resin tooth that fits the edentulous space it is expected to fill. If the stock tooth is not wide enough to make adequate contact with the abutment teeth, add softened inlay wax, or cold-curing acrylic resin, to it. If the tooth is larger than the edentulous space, cut it to fit. If the edentulous span is long, join the required number of acrylic resin teeth together with sticky wax or cold-curing acrylic resin placed at the contact area. Shape the ridge lap of the tooth (or teeth) to the ridge contour by adding softened inlay wax to the cervical end of the acrylic resin tooth (Fig. 4, A), and pressing it gently over the ridge on the master cast (Fig. 4, B). Adjust the occlusion of the pontic pattern by grinding or adding softened inlay wax to the occlusal surface o~ the acrylic resin tooth. If the pontic is to be restored with a veneer, hollow out the buccal or labial surface of the acrylic resin tooth, and make undercuts in the proximal corners of the recessed surface. Small gold loops may be attached to the window (recessed surface) with sticky wax to help retain the veneer facing (Fig. 4, C). Then invest and cast the pattern. It usually requires 15 minutes at 1280 ° F. to burn the acrylic resin pattern out of the mold before it is cast. MAKING A VENEER FROM AN ACRYLIC RESIN TOOTH
Measure on the master cast the length and width of the abutment teeth to be restored. Select a stock acrylic resin tooth of that size, or one slightly smaller. Grind the lingual surface of the tooth away until there is a space of 1 ram. between the die and the stock tooth (the facing), and until it is esthetically correct. Grind the cervical end of the facing to fit the shoulder or chamfer on the die. The facing should be just shy of contact with the adjacent teeth in order to allow for an adequate thickness of gold. This is done by beveling the incisal and proximal surfaces of the resin facing. Attach the resin facing to the die with sticky wax so that it is in the desired position, and standing about 1 mm. away from the die (Fig. 5, a ) . Apply a thin film of petroleum jelly over the labial surfaces of the adjacent teeth on the master cast, but not over the facing. Make a buccal or labial core of quick-setting plaster about ½ inch thick. Remove the core, and with it in the desired position, lute the facing to the core by means of sticky wax. Coat the lingual surface of the facing and the labial surface of the die with Microfilm, and reseat the core on the cast. Let softened inlay wax flow between the facing and the die. Form the window, and then wax up the remainder of the crown pattern on the die (Fig. 5, B). Gently withdraw the plaster core and the facing away from the labial surface of the cast. Separate the facing from the core, and place the facing back in the "window" of the wax pattern on the die. The "window" should cover the cervical, incisal, and proximal surfaces of the acrylic resin facing in order to protect the veneer.
Volume 18 Number 4
Acrylic resin teeth
Fig. 4 A pontic. A, The dotted line shows the inlay wax added to the ridgelap (cervical end) of a stock acrylic resin tooth. B, The pontic with the modified ridgelap. C, A proximal view of the window cut into the pattern; (gl) gold loops, and (u) undercuts cut into the pattern. Fig. 5 An acrylic resin veneer crown. A, (d) the die, (arf) the acrylic resin facing, and (sw) sticky wax. B, (d) the die, (p) the plaster core, (w) inlay wax, and (ar[) acrylic resin facing. C, The facing in position; (ar[) the acrylic resin facing, (w) the wax pattern, and (s) the space between the facing and the wax pattern. D, The completed crown; (gc) the gold casting, (ar[) the acrylic resin facing, (h) the heat-cured acrylic resin, and (gl) gold retention loops.
Remove the facing and reduce the thickness of the wax "window" as much as possible, to allow for the thickness of the opaque resin and for a layer of heatcuring acrylic resin that will attach the facing to the "window" in the final packing (Fig. 5, C). Carve undercuts in the "window," and attach small gold loops to the pattern to help retain the acrylic resin facing. Roughen the lingual surface of the facing with a bur in order to secure a better bonding of the heat-curing acrylic resin to the facing. After the crown pattern is cast, polished, and fitted in the mouth, seat the facing in the "window" of the crown with softened white wax. Flask the crown with the resin facing in position, and then separate the flask, and boil out the wax in the usual manner. Paint opaque resin of the proper shade over the window and allow it to dry. Then apply a thin layer of heat-curing acrylic resin in the window under the facing, and close the flask for final heat curing (Fig. 5, D ) . REPLACING A LOST VENEER FACING WITH A GROUND STOCK ACRYLIC RESIN TOOTH Measure the width and length of the gold window in the crown, and select a slightly smaller acrylic resin tooth. Grind the lingual surface of the tooth as thin as possible, without altering the color of the tooth being converted into a facing. Adjust the cervical, incisal, and proximal surfaces of the facing until it fits into the "window" of the crown. Make undercuts around the margins of the "window" with an inverted cone bur, and then cement the facing in the "window" with cold-curing acrylic resin of the desired color. When the acrylic resin has reached the dough stage, trim away the excess with a sharp blade. The crown can be polished after the resin has completely set.
j. Pros. Dent. October, 1967
Acrylic resin teeth can be used in the construction of many types of crown and partial denture restorations. Their use simplifies the fabrication of crowns, posts, and pontics. A pattern made from an acrylic resin tooth is precarved, can be easily modified to the desired contour, and does not fracture when it is handled. Temporary partial dentures and crowns can be constructed quickly with a good esthetic result, and lost crown facings can be easily replaced by grinding a selected acrylic resin tooth to fit the "window" in the metal restoration. VETERANS ADMINISTRATION HOSPITAL FIaST AVENUE AT EAST 24TH STREET NEW YORK, N. Y. 10010