A provisional and new crown removable partial denture

to fit into a clasp of an existing

D.A. Elledge, D.D.S., M.S.,* and B. L. Schorr, D.D.S., M.S.* University of Missouri-Kansas City, School of Dentistry, Kansas City, MO. A technique that forms an abutment crown to fit into an existing clasp of a removable partial denture by relining an acrylic resin pattern is described. The outer contour of the pattern is made within an irreversible hydrocolloid impression by use of Duralay autopolymerizing acrylic resin applied with precision dispensers. The pattern is formed before tooth preparation and is made approximately 0.4 mm thick. After tooth preparation, the shell pattern is relined with the same autopolymerizing resin and the existing removable partial denture is &ted over it. The gross pattern is trimmed and the margins refined on a die made from an elastomer impression. The refined pattern is cast and finished, avoiding reduction of the contours established. A second crown is similarly formed in tooth-colored autopolymerizing acrylic resin. It serves as a provisional restoration that allows the patient to wear the removable partial denture while the laboratory procedures are performed. (J PROSTHET DENT 1990;63:541-4.)


seof a removable partial denture (RPD) may be prolongedif a decayedabutment tooth can be restoredwith a crown that fits the clasp of the prosthesis.’ This can be accomplishedby using a direct-indirect technique. An irreversible hydrocolloid impressionis made of the treatment site without the RPD in place. This impression is usedto makea hollow shell acrylic resinpattern that duplicates the contour of the original abutment. The pattern is made before tooth preparation, with precision resin dispensersusing autopolymerizing resins. The, direct phase consistsof relining of the thin shell

pattern on the tooth with the RPD seated and in proper occlusion.The pattern is usedby the dental laboratory to preserveregionsof clasp contact that will be incorporated into the final restoration. The indirect phaseinvolves transfer of the pattern to a die and working cast for final marginal adaptation and ease of finishing. A secondpattern is used as the provisional restoration. The patient continues to wear the RPD throughout treatment.

TECHNIQUE 1. Seat the RPD, check for proper fit to the existing

*As&ant Professor, Department 10/l/18288



of Fixed Prosthodontics.

1. Irreversible hydrocolloid impressionis made.




abutment, and remove. 2. Restore fractured cusps or undercuts resulting from caries removal to proper contour with soft wax or a suitable restorative material2


2. Existing cast crown is sectioned to easeremoval,


Fig. 6. Powder blower saturates monomer layer on buccal Wall.

Fig. 3. Clasp arms and tooth preparation are checked for adequate clearance.

Fig. 4. Resin monomer is deposited on buccal wall in a uniform layer.

Fig. 7. Hollow shell is approximately

Fig. 6. Powder blower powder.

fine stream of resin

Fig. 8. Hollow shell is trimmed with slightly short margins.

3. Make an irreversible hydrocolloid impression of the correctly contoured abutment to serve as a matrix (Fig. 1). 4. Remove the defective crown if present and prepare the tooth (Figs. 2 and 3). 5. Apply one or two drops of Duralay monomer (Reliance Dental Mfg. Co., Worth, Ill.) with a monomer applica’ tar (Speedi-temp, Prairie Village Prosthetics, Prairie Village, Kan.) to the buccal wall of the impression to attain a uniform layer (Fig. 4). Pooling of monomer due

to gravity is prevented by holding the impression vertical. 6. Apply the Duralay powder with a powder blower (Speedi-temp, Prairie Village Prosthetics) in uniform layers until the tooth imprint has a dull surface (Figs. 5 and 6). 7. Alternately, reapply monomer and polymer three to four times. Build up the lingual wall in a similar manner. Overspray fills the occlusal surface. 8. Allow the resin to cure in the impression for 4 minutes





0.4 mm thick.










Fig. 9. Hollow shell is loaded with creamy mix of resin.

.I- .- --.


Fig. 12. Final cast crown with contours to fit clasp of RPD.

Fig. 10. RPD is seated before set of resin. Fig. 13. Porcelain-fused-to-metal crown for left first premolar with clasp-bearing regions primarily on metal surfaces.

is made in similar fash-

Fig. 14. Use of technique result8 in increased metal surfaces on new crown (A) when compared to existing crown (B).

or place it in a pressure curing vessel for a denser structure.” 9. Tease the hollow shell from the impression with hemostats. It should be approximately 0.4 mm thick (Fig. 7). 10. Trim the shell short of the margin with a sandpaper disk to minimize binding and facilitate seating (Fig. 8). 11. Place the hollow shell over the prepared tooth, insert the RPD, and check for a passive fit.

12. Coat the exposed dentin with Barrier cavity liner (Teledyne Getz, Elkgrove Village, Ill.) to minimize exposure to resin components.4 13. Apply a drop of mineral oil U.S.P. asa separating medium. 14. Fill the hollow resin shell with a creamy mix of Duralay resin and partially seat over the tooth (Fig. 9). 15. Seat the RPD quickly over the pattern and have the

Fig. 11. Provisional restoration ion with tooth-colored resin.









18. 19.



22. 23.

24. 25. 26.

patient close firmly into centric occlusion to complete the seating (Fig. 10). Remove and reseat the pattern and RPD before final set of the resin to avoid locking. The precured shell minimizes warpage during handling. Inspect the pattern, trim the margins, and selectively grind to relieve binding due to polymerization shrinkage of the resin. Coat the pattern with an evaporation curing clear resin glaze (George Taub Co., Jersey City, N.J.) for a smooth finish. Reseat the pattern on the tooth and check for accuracy and fit. Use a blue pen to identify regions of clasp contact on the pattern. They must not be altered during the indirect phase. Make an elastomer sectional impression and necessary jaw relation records for convenient laboratory finishing. Repeat steps 5 through 18 with tooth-colored acrylic resin for construction of the provisional restoration (Fig . 11) .5-7 Cement the provisional restoration and return the RPD to the patient. Send the relined resin pattern, the cast retrieved from the elastomer impression, the jaw relation records, and a work authorization to the dental laboratory. In the laboratory, seat the pattern on the trimmed die and rewax the margins. Cast the resin pattern and modify the polishing procedure to preserve contours in clasp-contacting regions. Deliver the new crown after the laboratory phase (Fig. 12).

DISCUSSION The direct-indirect powder-blower technique offers advantages over other techniques. It does not require that the margins be completed in the resin pattern.* It does not require that the RPD be sent to the dental laboratory or taken from the patient.s The hollow shell pattern can be made before tooth preparation to minimize chair time. The pattern can be handled with minimal warpage during the reline, and the technique does not require a coping.8 The disadvantage of this technique is that a porcelain-



veneered crown requires clasp-bearing zones to be on metal surfaces (Fig. 13). This may overextend the metal into esthetic regions (Fig. 14). Clasp-bearing zones that are to remain on porcelain-veneered surfaces will require laboratory procedures that necessitate having the RPD for construction of the crown in an indirect technique.4* 5

SUMMARY A provisional restoration and new crown are fitted to an existing RPD clasp. With precision resin dispensers, autopolymerizing acrylic resin patterns for a cast crown and a provisional restoration are made before tooth preparation. The technique allows the RPD to be seated and centric occlusion verified. The axial and occlusal contours are preserved by a hollow shell pattern that is subsequently relined. The technique is best suited for a complete cast crown. The pattern is not cut back in the regions that are contacted by the clasp if veneering is required. The restoration is completed in two visits and the patient can continue to wear the RPD during the laboratory phase. REFERENCES 1. Samani SI, Mullick C. A new crown for an existing removable partial prosthesis. Quintessence Int 1979;4:35-40. 2. Tepo KW, Smith FW. A technique for restoring abutments for removable partial dentures. J PROSTHET DENT 1978;40:398-401. 3. Craig RG. Restorative dental materials. 6th ad. St Louis: CV Mmby Co, 1980;380-1. 4. Tjan AH, Grant BE, Nemets H. The efficacy of resin-compatible cavity varnishes in reducing dentin permeability to free monomer. J PROSTHET DENT


5. Goodkind RJ, Baker JL. Theory and practice of precision attachment removable partial dentures. St Louis: CV Mosby Co, 1981;102-8. 6. Elledge DA, Hart JK, Schorr BL. A provisional restoration technique for laminate veneer preparations. J PROSTHET DENT 1989;62:139-42. 7. Elledge DA, Mixon JM, Cowan RD, Horvath G. Predicting esthetics of laminate veneers without tooth preparation. Quintessence Int 1990; 21:15-8.

8. Warnick ME. Cast crown restoration fit an existing removable partial 1970;14:631-44. Reprint


of a badly involved abutment to denture. Dent Clin North Am










A provisional and new crown to fit into a clasp of an existing removable partial denture.

A technique that forms an abutment crown to fit into an existing clasp of a removable partial denture by relining an acrylic resin pattern is describe...
686KB Sizes 0 Downloads 0 Views