Amalgam crown restorations for posterior pulpless teeth

Amalgam Clifford

crown B. Starr,

restorations

for posterior

pulpless

teeth

D.M.D.*

Wright Patterson U.S. Air Force Medical Center, Wright Patterson AFB, Ohio Cast restorations are the usual technique chosen for the restoration of posterior pulpless teeth. Complex amalgam restorations are suggested as an alternative method of treatment, and several advantages are described. Techniques to provide sufficient retention and resistance form include the use of threaded pins, amalgapins, slots and grooves, amalgam in the pulp chamber, or canals, or both, and posts cemented within the canals. The practicing clinician is advised to become familiar with these retention techniques so that difficult retention situations may be treated effectively.(J PROSTHETDEN; 1990;63:614-9.)

T he restoration

of posterior endodontically treated teeth represents an everyday challenge to the restorative dentist. While some teeth present only a conservative access cavity, many are badly mutilated, with little or no sound supragingival tooth structure remaining. The restorative challenge is to restore form and function to the tooth so that it may serve successfully for many years. Even a conservative accesscavity results in the loss of a tremendous amount of tooth structure. The roof of the pulp chamber provides much of the necessary support for the natural tooth, and its loss leaves the facial and lingual walls severely weakened and without sufficient support.‘* 2 This problem often leads to fracture of one or more cusps that may or may not be restorable. The traditional approach has been to place a cast restoration after the completion of endodontic therapy.3-7 The casting serves’to protect the remaining tooth structure from further destruction by preventing cuspal fracture while restoring proper contours, anatomic form, and function. An amalgam crown may serve as a useful alternative treatment for the restoration of the posterior endodontitally treated tooth. If a high-copper alloy is used, the amalgam crown may contain sufficient strength to resist fracture*. g while protecting the remaining cusps and restoring form and function to the affected tooth. In addition, several advantages may be inherent with the use of an amalgam technique. They include: 1. Amalgam crowns are less expensive. 2. Less chairside time may be required. 3. Only one appointment is necessary.

The opinions expressedherein are those of the author and are not to be construed as official or reflecting the viewsof the U.S. Air Force or the Department of Defense. *Lieutenant Colonel, U.S.Air Force(DC); Chairman, Department of General Dentistry end Assistant Director, General Practice Residency. 10/1/17714

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4. The time interval between tooth preparation and cementation of the restoration is avoided. 5. A temporary crown is unnecessary. 6. Dental laboratory support is eliminated. 7. The dentist has complete control over all steps of the restorative sequence. 8. Laboratory personnel are not exposed to the patient’s saliva and possible pathogens. 9. Gingival retraction techniques are usually not needed.

REVIEW

OF LITERATURE

Sorensen and Martinof? reviewed more than 6000 patient records involving 1273 endodontically treated teeth. They determined that coronal coverage significantly improved the clinical success rate for posterior teeth. They also determined that the use of a post to provide intracoronal reinforcement did not improve the success rate. They concluded that posts may be useful for the retention of crown substructures, but that posts did not favorably affect the posterior tooth’s ability to resist root fracture. Nayyar et al.,6 in their report on the use of amalgam posts for core retention, concluded that “the use of an amalgam dowel and core as a final restoration would be a compromise, since axial contours, proper contacts, and optimum occlusion would best be established with a cast restoration.” The use of amalgam crowns of definitive restorations for posterior pulpless teeth has been recommended, however, Brown et al.7 advocated placement of pin-retained amalgam crowns as definitive restorations for endodontically treated teeth. They described a technique for making pinretained amalgam restorations and listed the following indications for their use: to facilitate completion of endodontics, for teeth with a questionable prognosis, or when economics, compromised medical status, high caries rate, or difficult dowel placement contraindicated the use of a cast restoration. Gordon et allo also advocated amalgam crowns for posterior endodontically treated teeth. They routinely used precast posts as the primary retentive device for the amalgam restoration.

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1. Tooth preparation using three amalgam pins for supplemental retention.

Fig.

Retention of complex amalgams as either a crown substructure or as the definitive restoration can be a difficult task. Pin retention was first introduced by Markleyll and became widely used after Going’9 introduction of self-threading pins. Lovdahl and Nicholls5 compared pin-retained amalgam cores with cast gold posts and cores. Sixty-five teeth received a force applied lingually at an angle of 130 degrees to the long axis. The amalgam cores were found to be superior with respect to resistance to fracture. This finding may surprise many dentists who believe that threaded pins are contraindicated in endodontically treated teeth because of the stresses created during their placement.13r I4 Several alternatives to the threaded pin retention technique for complex amalgam restorations have been advocated. Shavel115~16described a technique using amalgam channels called “amalgapins” to retain complex amalgam restorations (Fig. 1). Davis et all7 determined that four, six, or eight amalgapins provided the same resistance to fracture as six or eight Regular TMS pins (Whaledent International, New York, N.Y.). Outhwaite et alla studied the effect of a dentinal retention slot and determined that a circumferential slot provided as much retention and resistance form as four TMS Minim pins (Whaledent International) (Fig. 2). Plasmans et al.lg evaluated four amalgam pins, four amalgam slots, a circumferential amalgam slot, and four TMS Minim pins for resistance to fracture. No significant differences were found for amalgam pins, amalgam slots, and TMS Minim pins when subjected to an oblique load. The circumferential slot offered significantly greater resistance to fracture. Birtcil and Venton20 advocated axial boxes and grooves rather than pins for the retention of complex amalgam restorations (Fig. 3). They also used parallelism of all cavity preparation walls to obtain the required retention form. Nayyar et al6 recommended that the pulp chamber, as

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2. A, Preparation with four threaded pins and one retention groove. B, Three retention grooves, one threaded pin, and pulp chamber are used for retention.

Fig.

3. Three axial boxes and cemented post were used to provide sufficient retention and resistance form.

Fig.

well as amalgam posts placed into the canals 2 to 4 mm, be used to retain amalgam cores (Fig. 4). They reported over 400 restorations where this technique provided adequate retention for amalgam cores under cast restorations. Kane

615

STARR

Fig. 4. A and B, Radiographs illustrate use of pulp chamber and canals for retention. C and D, Radiographs illustrate use of one threaded pin to increase retention provided by pulp chamber. et a1.21studied the effect of remaining pulpal wall height on the need for placing amalgam posts into canals. They determined that amalgam need be placed into canals only to increase retention if less than 4 mm ‘of pulpal wall height remained.* The use of preformed posts to increase retention for crown substructures has been widely advocated,22-26and a large variety of products are currently available (Figs. 5 and 6).

DIS(XJSSION Numerous studies have been undertaken to determine the ideal way to restore endodontically treated teeth. Most concentrate on the post and core to serve as a substructure for’s cast restorations.28-33 There are no direct studies regarding the suitability of complex amalgam restorations as definitive treatment for posterior endodontically treated teeth. There are, however, many clinical factors that support their use. Perhaps the greatest advantage of amalgam restorations is that the dentist has complete control over making the restoration, and reliance on laboratory support is elimi-

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nated. Another advantage is that no laboratory personnel are exposed to the patient’s saliva, which may be contaminated with pathogens if the patient is carrying a communicable disease. Amalgam crowns may provide a relatively inexpensive alternative for the restoration of posterior pulpless teeth, since less chairside time is required and no laboratory fees are involved. Patient treatment time can be used efficiently when an amalgam crown is planned as the final restoration; a temporary crown is not needed. Also, gingival retraction techniques are usually not needed for amalgam crowns. The study by Sorensen and Martinoff supports the contention that cuspal coverage is necessary for predictable restorative success of endodontically treated posterior teeth. Some dentists may believe that amalgam crowns are unsuitable as definitive restorations for endodontically treated teeth because they are not strong enough to withstand occlusal forces or they will not last long enough in the oral environment. However, high-copper amalgam restorations contain sufficient strength to withstand occlusal forces and protect the tooth from fracture.8,g Lieberman et al.8 investigated the effect of occlusal

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Fig. 5. A, Mandibular molar after completion of endodontic therapy. B, Pulp chamber and amalgam pin offer insufficient resistance to distal displacement of restoration. C, Precast post is cemented into distal canal to increase resistance to distal displacement. D, Radiograph of cemented post and final restoration. E, Completed amalgam crown.

forces on amalgam overlay restorations and cast gold onlay restorations. They found that gold castings luted with zinc phosphate cement and high-copper amalgam restorations were both of sufficient strength to withstand occlusal forces, since none of the restorations fractured under the conditions of their in vitro study.

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Summitt and Robbins reviewed over 10,000 patient records and evaluated 171 complex amalgam restorations, which they defined as replacing at least one cusp. They found the mean life expectancy to be 11.5 years for complex amalgam restorations. This evidence suggests that complex amalgam restorations exhibit surprising durability and

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Fig. 6. A, Remaining tooth structure offers insufficient retention and resistance form. B, Precast post is cemented into distal canal. C, Two threaded pins are added for additional retention and resistance. D, Restoration complete. E, Amalgam crown after final polish.

may contain sufficient strength to protect the remaining tooth structure. Clinical studies are required to determine the long-term prognosis for amalgam crown restorations of posterior pulpless teeth.

viewed. The practicing dentist should become familiar with all the retention techniques discussed so that they may be used alone or in combinstion for difficult retention situations.

SUMMARY The advantages of complex amalgam restorations as definitive treatment for posterior endodontically treated teeth were described. Techniques to provide sufficient retention and resistance form to ensure success were re618

REFERENCES 1. Johnson JK, Schwartz NK, Blackwell RT. Evaluation and restoration of endodontically treated posterior teeth. J Am Dent Assoc 1976;93:597605. 2. Weine FS. Endodontic therapy. 3rd ed. St Louis: CV Mosby, 1982.

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3. Shillingburg HT, Kessler JC. Restoration of the endodontically treated tooth. Chicago: Quintessence Publishing, 1982. 4. Sorensen JA, Martinoff, JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J PROSTHET DENT 1984;51:760-4.

5. Lovdahl PE, Nicholls JI. Pin retained amalgam cores vs. cast-gold dowel-cores. J PROSTHET DENT 1977;38:507-14. 6. Nayyar A, Walton RE, Leonard LA. Amalgam coronal-radicular dowel and core technique for endodontically treated posterior teeth. J PROSTHET DENT 1980;43:511-5.

7. Brown BR, Barkmeier WW, Anderson tally treated posterior teeth with

RW. Restoration of endodontiamalgam. J PROSTHET DENT

1979;41:40-4.

8. Lieberman R, Judes H, Cohen E, Eli I. Restoration of posterior pulpless teeth: amalgam overlay versus cast gold onlay restoration. J PROSTHET DENT 1987;57:540-3.

9. Summitt JB, Robbins JW. Longevity of complex amalgam restorations [Abstract]. J Dent Res 1987;66:329. 10. Gordon M, Judes H, Laufer BZ, et al. An immediate dual purpose restoration of posterior root-filled teeth (the amalgam crown). Dent Med 1984;2:22-6. 11. Markley MR. Pin reinforcement and retention of amalgam foundations and restorations. J Am Dent Assoc 1958:56:675-9. 12. Going RE. Pin-retained amalgam. J Am Dent Assoc 1966;73:619-24. 13. Dilts WE, Welk DA, Laswell HR, George L. Crazing of tooth structure associated with placement of pins for amalgam restorations. J Am Dent Assoc 1970;81:387-91. 14. Galindo Y. Stress-induced effects of retentive pins. A review of the literature. J PROSTHET DENT 1980;44:183-6. 15. Shave11 HM. The amalgapin technique for complex amalgam restorations. Calif Dent Assoc J 1980,8:48-55. 16. Shave11 HM. Updating the amalgapin technique for complex amalgam restorations. Int J Perio Res 1986;5:23-35. 17. Davis SP, Summitt JB, Mayhew RB, et al. Self-threading pins and amalgapins compared in resistance form for complex amalgam restorations. Oper Dent 1983;8:88-93. 18. Outhwaite WC, Garman TA, Pashley DH. Pin vs slot retention in extensive amalgam restorations. J PROSTHET DENT 1979;41;396-400. 19. Plasmans PJJM, Kusters ST, de Jange BA, van ‘t Hof MA, Vrijhoef

Conservative review Rill Fort

G. Banks, Walton

Beach,

posterior D.D.S.,

ceramic

MMA. In vitro resistance of extensive amalgam restorations using various retention methods. J PROSTHETDm 1987;57:16-20. 20. Birtcil RF, Venton EA. Extracoronal amalgam restorations utilizing available tooth structure for retention. J PROSTHET DENT 1976;35:1718. 21. Kane JJ, Burgess JO, Summitt JB. Fracture resistance of amalgam coronal-radicular restorations [Abstract]. J Dent Res 1988;67:344. 22. Miller AW. Post and core systems: which one is beat? J PROSTHET DENT 1982;48:27-38.

23. Caputo AA, Standlee JP. Pins and posts-wby, when and how. Dent Clin North Am 1976;20:299-311. 24. Deutsch AS, Musikant BL, Cavallari J, Lepley JB. Prefabricated dowels: a literature review. J PR~~THET DENT 1983;49:498-503. 25. Shillingburg HT, Fisher DW, Dewhurst RB. Restoration of endodontitally treated posterior teeth. J PROSTHET DENT 1970;24:401-9. 26. Hudis SI, Goldstein GR. Restoration of endodontically treated teeth: a review of the literature. J PROSTHET DENT 1986;55:33-8. 27. Goerig AC, Mueninghoff LA. Management of the endodontically treated tooth. Part I: concept for restorative designs. J PRO~THET DENT 1983;49:340-5.

28. Goerig AC, Mueninghoff LA. Management of the endodontically treated tooth. Part II: technique. J PRCISTHET DENT 198’&4Sz491-7. 29. Hoag EP, Dwyer TG. A comparison evaluation of three post and core techniques. J PROSTHET DENT 1982;47:177-81. 30. Chan RW, Bryant RW. Post core foundations for endodonticallytreated posterior teeth. J PR~~THET DENT 1982;48:401-6. 31. Kantor ME, Pines MS. A comparative study of restorative techniques for pulpless teeth. J PROSTHET DENT 1977;38:405-12. 32. Desort KD. The prosthodontic use of endodonticaby treated teeth; theory and biomechanics of post preparation. J PROSTHET DENT 1983;49:203-6.

33. Standlee JP, Caputo AA, Hanson EC. Retention of endodontic dowels: effects of cement, dowel length, diameter, and design. J PROSTHJFT DENT 1978;39:401-5. Reprint requests to: DR. CLIFFORD B. STARR 4062 QUAIL BUSH DR. DAYTON, OH 45424

restorations:

A literature

M.S.

Fla.

Conservative ceramic restorations have much to offer to improve appearance and strengthen posterior teeth. The advent of resin bonding makes possible many designs for inlays, onlays, and partial coverage crowns. This review discusses conventional porcelain, Optec HSP porcelain, Dicer, and Cerapearl with emphasis on strengthening mechanisms, principles-of preparations, accuracy of fit, and indications.(J PROSTRET DENT 1990;63:619-26.)

C

eramic inlays have generated extreme interest in the past few years because of public demand for esthetic restorative materials. Nevertheless, many of the materials

Presented at the Academy pus Christi, Tex.

of Denture

Prosthetics

10/l/18540

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meeting,

Cor-

in use and under development are merely technologic refinements of porcelain systems that originated more than 100 years ago.i In 1339, Land as reported by Marra,2 or& inated the porcelain inlay. Porcelain inlays and crowns were developed by Wain in 1923 as reported by Jones3 in which molten porcelain (glass) was cast into a refractory mold by use of an ordinary gas blowpipe to melt the I;bFcelain. In the 1930s a multishaded, commercially available

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