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Making a crown to fit accurately under an existing removable partial denture clasp assembly
Making a crown to fit accurately under an existing removable partial denture clasp assembly Carl A. Hansen, DDS,* and Melinda
M. Russell,
DDS, MSb
University of Florida, College of Dentistry, Gainesville, Fla., and University of Michigan, School of Dentistry, Ann Arbor, Mich.
The most difficult aspect of retrofitting a new crown to an existing removable partial denture clasp assembly is maintaining an accurate relationship of the prepared abutment tooth to the clasp assembly while making an impression. A procedure is presented that helps to ensure that the framework is not displaced during this critical step of the process. (J PROSTHET DENT 1994;71:206-8.)
N umerous
procedures have been proposed to con-
struct a crown under an existing removable partial denture (RPD) clasp assembly.‘-” This plethora of approaches testifies to the difficulties involved in the procedure. The complexity of the crown preparation requires an indirect impression procedure to ensure that adequate marginal fit and proper contours are achieved. A major complication that can be encountered with an indirect impression procedure is the potential for the RPD to be displaced as the impression of the tooth and removable partial denture is made. Any movement on the part of the removable prosthesis will result in an incorrect relationship between the clasp assembly and the die of the prepared tooth. The outcome will be a crown that does not fit the clasp assembly when the two are inserted into the patient’s mouth. This article presents an indirect impression procedure that greatly reduces the likelihood of the correct clasp assembly/crown preparation relationship being disturbed when an impression is made of the prepared tooth and RPD.
PI SOCEDURE 1. Ascertain that the RPD components fit the patient’s
hard and soft tissues adequately. Stabilize distal extension and large anterior bases that are not well sup-
ported by the underlying ridge by relining with a zinc oxide-eugenol or elastomeric material. Adjust direct retainers that are not retentive, to provide sufficient retention to resist dislodgment by tongue movements or gravity. Where adequate retention cannot be achieved, use a denture adhesive to aid in retaining the RPD during the impression procedure.
Fig. 1. Adequate space for proposed crown exists between clasp assembly and prepared tooth. 2. Prepare the damaged abutment tooth, which lies under the clasp assembly, in the usual manner. Verify that
BAssistant Professor, Department of Prosthodontics, University of Florida, School of Dentistry. bAssistant Professor, Department of Prosthodontics, University of Michigan, School of Dentistry. Copyright @ 1994 by The Editorial Council of THE JOURNAL OF PROSTHETIC DENTISTRY. 0022-3913/94/$1.00 + .lO
10/l/51610
sufficient space exists for the restorative material to be used for the crown (Fig. 1). 3. Seat the RPD so that the clasp assembly is related cor-
rectly to the prepared abutment tooth and flow a pattern resin such as Duralay (Reliance Dental Mfg. Co., Worth, Ill.) around the rest and onto a small area of the occlusal surface of the prepared tooth (Fig. 2).
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71
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2
NANSEN
AND RIJSSELL
Fig. 2. Pattern resin is cured around rest and onto the occlusal surface of prepared tooth.
Fig. 3. Pattern resin is in contact with stone die after recovery from impression and assembly on stone cast (arrow).
4. After the resin sets, remove the RPD from the patient’s mouth and trim the excess material to ensure that the resin contacts the occlusal surface in one small area. Verify the stability of the RPD and the contact of the pattern resin on the prepared tooth.
FEBRUARY
1994
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 4. Molar crown constructed under existing clasp assembly has passive contact with assembly components and provides support, stabilization, and retentive functions.
5. Examine the full arch impression tray intraorally to verify that it fits passively over the RPD. (When fully seated, the tray must not dislodge the RPD.) 6. Remove the RPD from the mouth and retract, the gingival tissues around the prepared abutment tooth. Inject impression material around and over the abutment tooth preparation, and seat the RPD. 7. Load the tray with light-bodied elastomeric impression material and seat it over the RPD. 8. Pick up the RPD within the full arch impression, block out undercuts on the RPD, and pour the impression in improved stone. Place dowel pin(s) into the stone in appropriate positions before the stone sets. 9. After the base of the working cast is added, recover the cast and RPD from the impression (Fig. 3). (The pattern resin should remain in contact with the stone die of the prepared tooth, thus indicating that the clasp assembly did not shift during the impression procedure.) 10. Remove the RPD from the working cast and saw the die free. (The die of the abutment tooth will have a small defect on the occlusal surface where the pattern resin 207
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OF PROSTHETIC
HANSEN
DENTISTRY
contacted the tooth. An extra layer or two of die spacer will eliminate this defect.) 11. Make the crown in the usual manner, providing passive contact with the components of the clasp assembly when the RPD is fully seated on the cast. Add a slight amount of wax to the crown pattern in the region just occlusal to the retentive terminal of the clasp before casting or, where appropriate, add porcelain at the last application to achieve the desired retentive undercut (Fig. 4).
SUMMARY A method was described that uses a small pattern resin projection attached to the occlusal rest of a clasp assembly to increase the stability of an RPD while an impression for a new crown under a clasp assembly is made. Other factors that might contribute to the retention and stability of the RPD during the impression procedure were also discussed.
AND
RUSSELL
2. Hill GM. Construction of a crown to fit a removable partial denture clssp. 3 PRDSTXETDOT 1977;38:226-9. 3. Thurgood BW, Thayer KE, Lee RE. Complete crowns constructed for an existing partial denture. J PFKXTHET DENT 19X&29:507-12. 4. Teppo KW, Smith FW. A technique for restoring abutments for removable partial dentures. J PROSTHET DENT 1978;4&398-401. 5. Elledge DA, Schorr BL. A provisional and new crown to fit into a clasp of an existing removable partial denture. J PROSTHET DENT 1990; 63541-4. 6. Samani Sl, Mullick CA. A new crown for an existing removable partial prosthesis. Quintessence Int 19’79;4:35-40. 7. Warnick ME. Cast crown restoration of a badly involved abutment to fit an existing removable partial denture. Dent Clm North Am 1970;14:631-44. 8. Ewing JE. The construction of accurate full crown restorations for an existing clasp by using a direct metal pattern technique. J PROSTHET DENT 1965;15:889-99.
9. Kahl RE. A cast restoration to fit an existing partial denture. Dent Dig 1963;69:250-3. 10. Barrett DA, Pilling LD. The restoration of carious clasp-bearing teeth. J PROSTHET DENT 1965;15:309-11. 11. Killebrew RH. Crown construction for broken down partial denture abutments. J PROSTHET DENT 1961;11:93-4. Reprint requests to: DR. CARPA. HANSEN DEPARTMENT OF PROSTHODONTICS
HNIVEFLSITY OF FLORIDA
REFERENCES 1. Goldberg A, Jones RD. Constructing cast crowns to fit existing removable partial denture clasps. J PROSTHET DENT 1976;36:382-6.
Availability
COLLEGE OF DENTISTRY PO Box 100435 GAINESVILU, FL 32610-0435
of JOURNAL back issues, 1987-1992
Back issues of THE JOURNALOFPROSTHETICDENTISTRYare available for purchase from the publisher, Mosby, at a cost of $7.50 per issue. (Foreign postage is not included.) The following quantity discounts are available: 25 % off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to Mosby, Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (800)325-4177, ext. 4351, or (314)453-4351 for information on availability of particular issues for that period from 1987 to 1992. If unavailable from the publisher, photocopies of complete issues are available from University Microforms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)7614700.
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M. Russell,
DDS, MSb
University of Florida, College of Dentistry, Gainesville, Fla., and University of Michigan, School of Dentistry, Ann Arbor, Mich.
The most difficult aspect of retrofitting a new crown to an existing removable partial denture clasp assembly is maintaining an accurate relationship of the prepared abutment tooth to the clasp assembly while making an impression. A procedure is presented that helps to ensure that the framework is not displaced during this critical step of the process. (J PROSTHET DENT 1994;71:206-8.)
N umerous
procedures have been proposed to con-
struct a crown under an existing removable partial denture (RPD) clasp assembly.‘-” This plethora of approaches testifies to the difficulties involved in the procedure. The complexity of the crown preparation requires an indirect impression procedure to ensure that adequate marginal fit and proper contours are achieved. A major complication that can be encountered with an indirect impression procedure is the potential for the RPD to be displaced as the impression of the tooth and removable partial denture is made. Any movement on the part of the removable prosthesis will result in an incorrect relationship between the clasp assembly and the die of the prepared tooth. The outcome will be a crown that does not fit the clasp assembly when the two are inserted into the patient’s mouth. This article presents an indirect impression procedure that greatly reduces the likelihood of the correct clasp assembly/crown preparation relationship being disturbed when an impression is made of the prepared tooth and RPD.
PI SOCEDURE 1. Ascertain that the RPD components fit the patient’s
hard and soft tissues adequately. Stabilize distal extension and large anterior bases that are not well sup-
ported by the underlying ridge by relining with a zinc oxide-eugenol or elastomeric material. Adjust direct retainers that are not retentive, to provide sufficient retention to resist dislodgment by tongue movements or gravity. Where adequate retention cannot be achieved, use a denture adhesive to aid in retaining the RPD during the impression procedure.
Fig. 1. Adequate space for proposed crown exists between clasp assembly and prepared tooth. 2. Prepare the damaged abutment tooth, which lies under the clasp assembly, in the usual manner. Verify that
BAssistant Professor, Department of Prosthodontics, University of Florida, School of Dentistry. bAssistant Professor, Department of Prosthodontics, University of Michigan, School of Dentistry. Copyright @ 1994 by The Editorial Council of THE JOURNAL OF PROSTHETIC DENTISTRY. 0022-3913/94/$1.00 + .lO
10/l/51610
sufficient space exists for the restorative material to be used for the crown (Fig. 1). 3. Seat the RPD so that the clasp assembly is related cor-
rectly to the prepared abutment tooth and flow a pattern resin such as Duralay (Reliance Dental Mfg. Co., Worth, Ill.) around the rest and onto a small area of the occlusal surface of the prepared tooth (Fig. 2).
VOLUME
71
NUMBER
2
NANSEN
AND RIJSSELL
Fig. 2. Pattern resin is cured around rest and onto the occlusal surface of prepared tooth.
Fig. 3. Pattern resin is in contact with stone die after recovery from impression and assembly on stone cast (arrow).
4. After the resin sets, remove the RPD from the patient’s mouth and trim the excess material to ensure that the resin contacts the occlusal surface in one small area. Verify the stability of the RPD and the contact of the pattern resin on the prepared tooth.
FEBRUARY
1994
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 4. Molar crown constructed under existing clasp assembly has passive contact with assembly components and provides support, stabilization, and retentive functions.
5. Examine the full arch impression tray intraorally to verify that it fits passively over the RPD. (When fully seated, the tray must not dislodge the RPD.) 6. Remove the RPD from the mouth and retract, the gingival tissues around the prepared abutment tooth. Inject impression material around and over the abutment tooth preparation, and seat the RPD. 7. Load the tray with light-bodied elastomeric impression material and seat it over the RPD. 8. Pick up the RPD within the full arch impression, block out undercuts on the RPD, and pour the impression in improved stone. Place dowel pin(s) into the stone in appropriate positions before the stone sets. 9. After the base of the working cast is added, recover the cast and RPD from the impression (Fig. 3). (The pattern resin should remain in contact with the stone die of the prepared tooth, thus indicating that the clasp assembly did not shift during the impression procedure.) 10. Remove the RPD from the working cast and saw the die free. (The die of the abutment tooth will have a small defect on the occlusal surface where the pattern resin 207
THE
JOURNAL
OF PROSTHETIC
HANSEN
DENTISTRY
contacted the tooth. An extra layer or two of die spacer will eliminate this defect.) 11. Make the crown in the usual manner, providing passive contact with the components of the clasp assembly when the RPD is fully seated on the cast. Add a slight amount of wax to the crown pattern in the region just occlusal to the retentive terminal of the clasp before casting or, where appropriate, add porcelain at the last application to achieve the desired retentive undercut (Fig. 4).
SUMMARY A method was described that uses a small pattern resin projection attached to the occlusal rest of a clasp assembly to increase the stability of an RPD while an impression for a new crown under a clasp assembly is made. Other factors that might contribute to the retention and stability of the RPD during the impression procedure were also discussed.
AND
RUSSELL
2. Hill GM. Construction of a crown to fit a removable partial denture clssp. 3 PRDSTXETDOT 1977;38:226-9. 3. Thurgood BW, Thayer KE, Lee RE. Complete crowns constructed for an existing partial denture. J PFKXTHET DENT 19X&29:507-12. 4. Teppo KW, Smith FW. A technique for restoring abutments for removable partial dentures. J PROSTHET DENT 1978;4&398-401. 5. Elledge DA, Schorr BL. A provisional and new crown to fit into a clasp of an existing removable partial denture. J PROSTHET DENT 1990; 63541-4. 6. Samani Sl, Mullick CA. A new crown for an existing removable partial prosthesis. Quintessence Int 19’79;4:35-40. 7. Warnick ME. Cast crown restoration of a badly involved abutment to fit an existing removable partial denture. Dent Clm North Am 1970;14:631-44. 8. Ewing JE. The construction of accurate full crown restorations for an existing clasp by using a direct metal pattern technique. J PROSTHET DENT 1965;15:889-99.
9. Kahl RE. A cast restoration to fit an existing partial denture. Dent Dig 1963;69:250-3. 10. Barrett DA, Pilling LD. The restoration of carious clasp-bearing teeth. J PROSTHET DENT 1965;15:309-11. 11. Killebrew RH. Crown construction for broken down partial denture abutments. J PROSTHET DENT 1961;11:93-4. Reprint requests to: DR. CARPA. HANSEN DEPARTMENT OF PROSTHODONTICS
HNIVEFLSITY OF FLORIDA
REFERENCES 1. Goldberg A, Jones RD. Constructing cast crowns to fit existing removable partial denture clasps. J PROSTHET DENT 1976;36:382-6.
Availability
COLLEGE OF DENTISTRY PO Box 100435 GAINESVILU, FL 32610-0435
of JOURNAL back issues, 1987-1992
Back issues of THE JOURNALOFPROSTHETICDENTISTRYare available for purchase from the publisher, Mosby, at a cost of $7.50 per issue. (Foreign postage is not included.) The following quantity discounts are available: 25 % off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to Mosby, Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (800)325-4177, ext. 4351, or (314)453-4351 for information on availability of particular issues for that period from 1987 to 1992. If unavailable from the publisher, photocopies of complete issues are available from University Microforms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)7614700.
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71
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2