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RESIN CEMENTS AND POSTOPERATIVE SENSITIVITY
OBSERVATIONS
GORDON J. CHRISTENSEN, D.D.S., M.S.D., PH.D.
RESIN CEMENTS AND POSTOPERATIVE SENSITIVITY Postoperative tooth sensitivi-
ty has been associated with cements and crown cementation since the advent of zinc phosphate cement in the 19th century. Reports of it have increased recently with the rise in use of resin cement. When resin-reinforced glass ionomer, or RRGI, cement was introduced, tooth sensitivity was reportedly reduced or eliminated, according to the nearly unanimous observations of practitioners worldwide. But the current popularity of all-ceramic crowns and polymer crowns has created another tooth sensitivity problem. Some of these crowns require the use of resin cement for adequate strength, and practitioners report significant postoperative sensitivity with many of these cements and their respective bonding agents. A recent Clinical Research Associates report showed that when using resin cements, practitioners saw postoperative sensitivity within the first year after cementation in about 37 percent of their patients with crowns;
with some brands of cement and bonding agents, up to 11 percent of the teeth required endodontic treatment within the first year.1 These are discouraging data. So while resin cements provide more strength than conventional cements, some of them have other challenges that are disagreeable to practitioners: difficult cleanup, oxygen inhibition, frequent tooth sensitivity and potential pulpal death. In this article, I discuss the need for resin cements. I also describe how to prevent postoperative sensitivity and what to do when postoperative sensitivity occurs. NEED FOR RESIN CEMENT IN FIXED PROSTHODONTICS
Currently, most North American dentists are using RRGI cements (such as Relyx-Vitremer, 3M Dental Products; Fuji Plus, GC America; Protec Cem, Ivoclar North America) for routine cementation of porcelainfused-to-metal crowns and allmetal crowns. Only on a few occasions are dentists using a resin adhesive as their routine
cement. The major types of crowns for which resin cement is used are some types of all-ceramic crowns, polymer crowns and metal crowns needing optimum retention. Some all-ceramic crowns can be cemented with conventional cements and have acceptable strength, and some cannot. The following discussion includes the most popular nonmetal crowns and the cements needed for their use. Empress. Research has shown that Empress crowns (Ivoclar North America) are too weak to serve adequately with conventional cements.2 Resin cement must be used to provide strength. Empress 2. Crowns and fixed prostheses made of Empress 2 (Ivoclar North America) are significantly stronger than those made with the original Empress. The newer material’s greater crown strength allows it to be used with RRGI cement (the company suggests Protec Cem [Ivoclar North America]). Clinical Research Associates’ findings
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
1197
CHRISTENSEN indicate that Protec Cem has less expansion than other RRGIs: typical RRGIs have about 2 to 3 percent expansion during setting, while Protec Cem has less than 1 percent.3 Protec Cem’s lower rate of expansion on setting and its increased strength allow it to be used with Empress 2. If additional strength is desired, resin cement could be used with Empress 2. Inceram. Inceram (Vident) crowns and fixed prostheses must be cemented with resin cement for optimum strength.3 Fired porcelain. Cementing porcelain jacket crowns or porcelain veneers requires the use of resin cement to achieve adequate strength. Porcelain veneers are strongest when cemented to etched enamel. Procera. During their short history, Procera (Nobel Biocare) crowns have been accepted very well. In my opinion, one of the major reasons they have achieved popularity is that they can be successfully cemented with conventional cements. RRGI is the most popular cement for use with these crowns. PREVENTING POSTOPERATIVE SENSITIVITY
For acceptable tooth desensitization, most resin cements require adequate use of a bonding-sealing agent between the tooth preparation and the crown. This sealer prevents potentially irritating chemicals in the cement from penetrating the dentinal canals to the dental pulp. Manufacturers have suggested several ideas for preventing pulpal sensitivity. Some of these techniques work consistently, and others do not. The 1198
following list of techniques will illustrate the cementation problems experienced with resin cement and the potential methods of preventing them. (A cautionary note: there is not a significant amount of controlled research on the topic of postoperative sensitivity. It is difficult to conduct studies in humans on this subject, and animals cannot report their tooth sensitivity problems. Many of the comments below, therefore, are based on responses I have received from large groups of continuing education program
For acceptable tooth desensitization, most resin cements require adequate use of a bonding-sealing agent between the tooth preparation and the crown. attendees to questions about their relative success with the respective techniques.) dThe clinician can place a bonding agent on the surface of the acid-etched tooth preparation and cure it just before cementing the crown with resin cement. This technique is suggested by several companies. If carried out correctly, it can work well. However, thick layers of cured bonding resin produce resistance to proper crown seating. Another potential problem with this concept is that some practitioners do not seal the acid-etched dentinal canals well with an adequate thickness of bonding agent, and the result is a sensitive tooth. In light of the potential challenges with this procedure, this is, in my
opinion, one of the least predictable techniques. dAfter tooth preparation, the clinician can place bonding agent on the preparation after the provisional restoration is made, but before the impression is made. This technique reportedly is successful, but it is challenging because the bonding agents can contaminate the impression materials during the impression procedure. Additionally, because of the time that elapses between the tooth preparation and the crown seating, the bonding resins are relatively chemically inactive at the time of cementation. This technique can be successful if carried out well. The bonding agent’s thickness does not interfere with the seating procedure, as the impression was made with the bonding agent in place. dAfter acid etching, the clinician can place a desensitizer, then place the typical primingbonding solution, seat the restoration with resin cement, and cure the cement and the bonding agent through the restoration. This is one of the most successful techniques for seating thin indirect restorations, such as porcelain veneers or shallow inlays or onlays. It is not as strongly indicated for thick crowns, because curing through thick restorations is difficult. Desensitizing agents such as Gluma Desensitizer (Heraeus Kulzer) or Microprime (Danville Materials) can be used successfully with this technique. dThe clinician can use a selfetching primer and bond. In my opinion, which is reinforced by anecdotal reports of dentists using this technique, this is the most successful and predictable of the desensitizing crown-
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
CHRISTENSEN cementing procedures when standard resin cement is being used. The most popular material and technique in this category is Panavia 21 or Panavia F (J. Morita USA) used with the self-etching primer, ED Primer (J. Morita USA). When using this technique, the clinician does not acid-etch the tooth preparation in the conventional manner. The smear layer of the tooth preparation is left on the tooth, and the self-etching, self-curing ED Primer is incorporated into the existing smear layer. The selfetching, dual-cure product Clearfil Liner Bond 2V (J. Morita USA) is one of the most predictable desensitizing products for use in the cementation of tooth-colored inlays or onlays with resin cement. dThe clinician can use a 4methacryloxyethyl trimellitate anhydride, or 4-META, cement. C&B-Metabond (Parkell) has an unprecedented history as a crown-cementing product that does not induce sensitivity. This material has been used for many years with success. However, some practitioners find it too difficult to use for routine procedures. The new Parkell 4-META product, TotalBond, is currently being observed by clinicians to determine its potential for desensitization and adequate crown cementation. It has a longer working time and is easier to clean up than C&B-Metabond. Preliminary reports from clinicians are optimistic.
what to do about tooth sensitivity that occurs after the cementation of a crown with resin. Regardless of preventive measures taken, resin-cemented crowns can exhibit postoperative sensitivity. Unfortunately, after a crown has been cemented with resin and the tooth is sensitive, the clinician does not have many good choices. I prefer to wait for up to six weeks to determine whether the sensitivity resolves by itself. In many cases, it does. In some patients, the pain only worsens and the crowns must be removed. Subsequently, when a provisional restoration is placed with an obtundent cement— such as a zinc oxide–eugenol, or ZOE, cement—the pain often resolves in a few days or weeks. Contrary to popular belief, there is no problem in using a ZOE temporary cement on a tooth preparation that eventually will receive resin cement. However, I suggest that the ZOE cement be left in place for at least two weeks before resin cement is used. If the tooth continues to be sensitive, endodontic therapy is needed. As a result of extensive personal practice experience with the problem of tooth sensitivity, I feel strongly that postoperative tooth sensitivity after the cementation of indirect restorations with resin cement can be prevented with relative ease if the clinician uses the procedures I have described.
SENSITIVITY AFTER CROWN CEMENTATION WITH RESIN: WHAT TO DO
CONCLUSIONS
Dentists commonly ask me
Postoperative tooth sensitivity after the cementation of crowns with resin cement is a
common problem in dentistry. It appears that the reason for the sensitivity is Dr. Christensen is failure to seal co-founder and senthe dentinal ior consultant of Clinical Research tubules that Associates, 3707 N. have been Canyon Road, Suite No. 7A, Provo, Utah opened by the 84604, and is a typical “totalmember of JADA’s editorial board. He etch” procehas a master’s dedure. If dentigree in restorative nal surfaces dentistry and a doctorate in education have been and psychology. He etched before is board certified in prosthodontics. cementation, Address reprint practitioners requests to Dr. should learn Christensen. how to seal the dentinal canals at the time of cementation. One of the most logical desensitizing concepts is to leave the smear layer on tooth preparations and impregnate the existing smear layer with a layer of self-etching primer. This concept has been one of the most predictable and successful to date. As the sensitivity problem is common, continuing clinical and basic science research is needed in this area. ■ The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the American Dental Association. Educational information on topics discussed by Dr. Christensen in this article is available through Practical Clinical Courses and can be obtained by calling 1-800-223-6569. 1. Clinical Research Associates. Filled polymer crowns: 1- and 2-year status reports. CRA Newsletter 1998;22(10):1-3. 2. Clinical Research Associates. Resin-reinforced glass ionomer (RRGI) cements, allceramic crown fracture. CRA Newsletter 1996;20(11):3. 3. Clinical Research Associates. Two new cements: compomer and hybrid ionomer. CRA Newsletter 1999;23(2):4.
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
1199
GORDON J. CHRISTENSEN, D.D.S., M.S.D., PH.D.
RESIN CEMENTS AND POSTOPERATIVE SENSITIVITY Postoperative tooth sensitivi-
ty has been associated with cements and crown cementation since the advent of zinc phosphate cement in the 19th century. Reports of it have increased recently with the rise in use of resin cement. When resin-reinforced glass ionomer, or RRGI, cement was introduced, tooth sensitivity was reportedly reduced or eliminated, according to the nearly unanimous observations of practitioners worldwide. But the current popularity of all-ceramic crowns and polymer crowns has created another tooth sensitivity problem. Some of these crowns require the use of resin cement for adequate strength, and practitioners report significant postoperative sensitivity with many of these cements and their respective bonding agents. A recent Clinical Research Associates report showed that when using resin cements, practitioners saw postoperative sensitivity within the first year after cementation in about 37 percent of their patients with crowns;
with some brands of cement and bonding agents, up to 11 percent of the teeth required endodontic treatment within the first year.1 These are discouraging data. So while resin cements provide more strength than conventional cements, some of them have other challenges that are disagreeable to practitioners: difficult cleanup, oxygen inhibition, frequent tooth sensitivity and potential pulpal death. In this article, I discuss the need for resin cements. I also describe how to prevent postoperative sensitivity and what to do when postoperative sensitivity occurs. NEED FOR RESIN CEMENT IN FIXED PROSTHODONTICS
Currently, most North American dentists are using RRGI cements (such as Relyx-Vitremer, 3M Dental Products; Fuji Plus, GC America; Protec Cem, Ivoclar North America) for routine cementation of porcelainfused-to-metal crowns and allmetal crowns. Only on a few occasions are dentists using a resin adhesive as their routine
cement. The major types of crowns for which resin cement is used are some types of all-ceramic crowns, polymer crowns and metal crowns needing optimum retention. Some all-ceramic crowns can be cemented with conventional cements and have acceptable strength, and some cannot. The following discussion includes the most popular nonmetal crowns and the cements needed for their use. Empress. Research has shown that Empress crowns (Ivoclar North America) are too weak to serve adequately with conventional cements.2 Resin cement must be used to provide strength. Empress 2. Crowns and fixed prostheses made of Empress 2 (Ivoclar North America) are significantly stronger than those made with the original Empress. The newer material’s greater crown strength allows it to be used with RRGI cement (the company suggests Protec Cem [Ivoclar North America]). Clinical Research Associates’ findings
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
1197
CHRISTENSEN indicate that Protec Cem has less expansion than other RRGIs: typical RRGIs have about 2 to 3 percent expansion during setting, while Protec Cem has less than 1 percent.3 Protec Cem’s lower rate of expansion on setting and its increased strength allow it to be used with Empress 2. If additional strength is desired, resin cement could be used with Empress 2. Inceram. Inceram (Vident) crowns and fixed prostheses must be cemented with resin cement for optimum strength.3 Fired porcelain. Cementing porcelain jacket crowns or porcelain veneers requires the use of resin cement to achieve adequate strength. Porcelain veneers are strongest when cemented to etched enamel. Procera. During their short history, Procera (Nobel Biocare) crowns have been accepted very well. In my opinion, one of the major reasons they have achieved popularity is that they can be successfully cemented with conventional cements. RRGI is the most popular cement for use with these crowns. PREVENTING POSTOPERATIVE SENSITIVITY
For acceptable tooth desensitization, most resin cements require adequate use of a bonding-sealing agent between the tooth preparation and the crown. This sealer prevents potentially irritating chemicals in the cement from penetrating the dentinal canals to the dental pulp. Manufacturers have suggested several ideas for preventing pulpal sensitivity. Some of these techniques work consistently, and others do not. The 1198
following list of techniques will illustrate the cementation problems experienced with resin cement and the potential methods of preventing them. (A cautionary note: there is not a significant amount of controlled research on the topic of postoperative sensitivity. It is difficult to conduct studies in humans on this subject, and animals cannot report their tooth sensitivity problems. Many of the comments below, therefore, are based on responses I have received from large groups of continuing education program
For acceptable tooth desensitization, most resin cements require adequate use of a bonding-sealing agent between the tooth preparation and the crown. attendees to questions about their relative success with the respective techniques.) dThe clinician can place a bonding agent on the surface of the acid-etched tooth preparation and cure it just before cementing the crown with resin cement. This technique is suggested by several companies. If carried out correctly, it can work well. However, thick layers of cured bonding resin produce resistance to proper crown seating. Another potential problem with this concept is that some practitioners do not seal the acid-etched dentinal canals well with an adequate thickness of bonding agent, and the result is a sensitive tooth. In light of the potential challenges with this procedure, this is, in my
opinion, one of the least predictable techniques. dAfter tooth preparation, the clinician can place bonding agent on the preparation after the provisional restoration is made, but before the impression is made. This technique reportedly is successful, but it is challenging because the bonding agents can contaminate the impression materials during the impression procedure. Additionally, because of the time that elapses between the tooth preparation and the crown seating, the bonding resins are relatively chemically inactive at the time of cementation. This technique can be successful if carried out well. The bonding agent’s thickness does not interfere with the seating procedure, as the impression was made with the bonding agent in place. dAfter acid etching, the clinician can place a desensitizer, then place the typical primingbonding solution, seat the restoration with resin cement, and cure the cement and the bonding agent through the restoration. This is one of the most successful techniques for seating thin indirect restorations, such as porcelain veneers or shallow inlays or onlays. It is not as strongly indicated for thick crowns, because curing through thick restorations is difficult. Desensitizing agents such as Gluma Desensitizer (Heraeus Kulzer) or Microprime (Danville Materials) can be used successfully with this technique. dThe clinician can use a selfetching primer and bond. In my opinion, which is reinforced by anecdotal reports of dentists using this technique, this is the most successful and predictable of the desensitizing crown-
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
CHRISTENSEN cementing procedures when standard resin cement is being used. The most popular material and technique in this category is Panavia 21 or Panavia F (J. Morita USA) used with the self-etching primer, ED Primer (J. Morita USA). When using this technique, the clinician does not acid-etch the tooth preparation in the conventional manner. The smear layer of the tooth preparation is left on the tooth, and the self-etching, self-curing ED Primer is incorporated into the existing smear layer. The selfetching, dual-cure product Clearfil Liner Bond 2V (J. Morita USA) is one of the most predictable desensitizing products for use in the cementation of tooth-colored inlays or onlays with resin cement. dThe clinician can use a 4methacryloxyethyl trimellitate anhydride, or 4-META, cement. C&B-Metabond (Parkell) has an unprecedented history as a crown-cementing product that does not induce sensitivity. This material has been used for many years with success. However, some practitioners find it too difficult to use for routine procedures. The new Parkell 4-META product, TotalBond, is currently being observed by clinicians to determine its potential for desensitization and adequate crown cementation. It has a longer working time and is easier to clean up than C&B-Metabond. Preliminary reports from clinicians are optimistic.
what to do about tooth sensitivity that occurs after the cementation of a crown with resin. Regardless of preventive measures taken, resin-cemented crowns can exhibit postoperative sensitivity. Unfortunately, after a crown has been cemented with resin and the tooth is sensitive, the clinician does not have many good choices. I prefer to wait for up to six weeks to determine whether the sensitivity resolves by itself. In many cases, it does. In some patients, the pain only worsens and the crowns must be removed. Subsequently, when a provisional restoration is placed with an obtundent cement— such as a zinc oxide–eugenol, or ZOE, cement—the pain often resolves in a few days or weeks. Contrary to popular belief, there is no problem in using a ZOE temporary cement on a tooth preparation that eventually will receive resin cement. However, I suggest that the ZOE cement be left in place for at least two weeks before resin cement is used. If the tooth continues to be sensitive, endodontic therapy is needed. As a result of extensive personal practice experience with the problem of tooth sensitivity, I feel strongly that postoperative tooth sensitivity after the cementation of indirect restorations with resin cement can be prevented with relative ease if the clinician uses the procedures I have described.
SENSITIVITY AFTER CROWN CEMENTATION WITH RESIN: WHAT TO DO
CONCLUSIONS
Dentists commonly ask me
Postoperative tooth sensitivity after the cementation of crowns with resin cement is a
common problem in dentistry. It appears that the reason for the sensitivity is Dr. Christensen is failure to seal co-founder and senthe dentinal ior consultant of Clinical Research tubules that Associates, 3707 N. have been Canyon Road, Suite No. 7A, Provo, Utah opened by the 84604, and is a typical “totalmember of JADA’s editorial board. He etch” procehas a master’s dedure. If dentigree in restorative nal surfaces dentistry and a doctorate in education have been and psychology. He etched before is board certified in prosthodontics. cementation, Address reprint practitioners requests to Dr. should learn Christensen. how to seal the dentinal canals at the time of cementation. One of the most logical desensitizing concepts is to leave the smear layer on tooth preparations and impregnate the existing smear layer with a layer of self-etching primer. This concept has been one of the most predictable and successful to date. As the sensitivity problem is common, continuing clinical and basic science research is needed in this area. ■ The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the American Dental Association. Educational information on topics discussed by Dr. Christensen in this article is available through Practical Clinical Courses and can be obtained by calling 1-800-223-6569. 1. Clinical Research Associates. Filled polymer crowns: 1- and 2-year status reports. CRA Newsletter 1998;22(10):1-3. 2. Clinical Research Associates. Resin-reinforced glass ionomer (RRGI) cements, allceramic crown fracture. CRA Newsletter 1996;20(11):3. 3. Clinical Research Associates. Two new cements: compomer and hybrid ionomer. CRA Newsletter 1999;23(2):4.
JADA, Vol. 131, August 2000 Copyright ©1998-2001 American Dental Association. All rights reserved.
1199