Bonded Silver Amalgam Restorations Michael Balanko, D.M.D."
Although silver amalgam is a strong, stable, technique-insensitive material, its use requires the removal of more intact tooth structure than adhesive materials in order to provide long-term retention. Thus remaining tooth structure is weakened rather than strengthened. Bonded silver amalgam restorations, on the other hand, have excellent retention, don't require pins. strengthen remaining tooth structure, eliminate the likelihood of cuspal fracture, and eliminate postoperative sensitivity.
S
ilver amalgam has been used successfully in dentistry for over a century (Fig. 1).The reasons for the demonstrated success of silver amalgam are many. It is a high strength, dimensionally stable material with excellent physical properties and is totally insoluble in mouth fluids. Further, silver amalgam is a highly "techniques-insensitive"material. That is,it will forgivemany more "manipulative abuses" than other restorative materials including composite resin. In addition, silver amalgam is relatively simple to use. and it is the only "self sealing" restorative material available. One of the major limitations of silver amalgam as a restorative material is that since it is not a bondable material it requires the removal of considerably more intact tooth structure than adhesive materials in order to provide long-termretention. Accordingly.silver amalgam weakens remaining tooth structure rather than strengthening it. This is the main reason that cuspal fracture is fairly common with long-standing silver amalgam restorations. The recent introduction of resin adhesive bonding materials such asAmalgam Bond (Parkell,Farmingdale. NY), AUBond (Liner F)(BiscoInc., Itasca, IL). and Geristore (Den Mat, Santa Maria, CA) for silver amalgam has been greeted with a high degree of enthusiasm by the profession since they allow the opportunity of effecting both amalgam to amalgam repairs and bonded amalgam restorations. Amalgam Bond consists of a 10 percent citric acid/3 percent ferric chloride as a dentin conditioner.aqueous hema (hydroxyethylmethacrylate) as a wetting agent, and 4-META. hema, and methyl methacrylate as the bonding agent.' Allbond Liner F makes use of either 10 percent phosphoric acid or succinic anhydride and hema as dentin conditioning
Figure 1. A 10-year silver amalgam restoration.
agents, NTG-GMA in acetone as a primer, and a proprietary base/catalyst fluoride containing bonding resin. Although a great deal of research has not yet been reported on these systems, DeSchepper et al (1991) have reported mean tensile bond strengths of amalgam to dentin using Allbond range from 10to 11megapascals and comparably very low to nonexistent bond values with the Amalgam Bond system. Roeder et al (1991) reported amalgam to amalgam bond strengths of 3.4to 8.8 megapascals with Allbond and little if any bond strength with Amalgam Bond.2Nonetheless, in a study carried out at the University of Manitoba involving 40 premolar and molar teeth with fractured buccal or lingual cusps in association with preexistent silver amalgam restorations repaired with new amalgam using Amalgam Bond adhesive, no failures were observed over a 1-year recall period. Any one of the three aforementioned materials may be used successfully for amalgam to amalgambonded repairs with a high degree of clinical reliability, and also bonded amalgam restorations may also be fabricated.
*Assistant hfessor. Faculty of Dentistry. University of Manitoba, Winnipeg. Manitoba Address =print requests to Michael Balanko. D.M.D.. Faculty of Denustry. University of Manitoba. Winnipeg.Manitoba M E OW3. 0 1992 Decker Periodicals Inc.
54
Bonded Silver Amalgam Restorations
BONDED AMALGAM RESTORATION Figure 2 shows a maxillary first premolar with severely weakened buccal and lingual cusps. Close examination of the preparation showed a near exposure of the disto-axial wall. Nevertheless, pulp protection is usually unnecessaly since the biologic acceptability of Allbond and Amalgam Bond are very high. All Etch was injected to cover all of the dentin and enamel surfaces of the preparation (Fig. 3) for a 15 to 20-second period followed by washing and drying (Fig. 4). The All Etch etches the enamel, removes the smear layer from the dentin, and opens the dentinal tubules (Fig. 5)without causing pulpal irritation. A moist cotton pledget is then wiped over the dentin surface (Fig. 61, since All Bond bonds better to moist surfaces. All Bond Primer A and B are then mixed and three to five successive coats are applied to the enamel and dentin with a fine-tipped soft brush (Fig. 7) followed by gentle warm air drying and visible light curing. The dentin and enamel surfaces should appear glossy and highly reflective at this stage (Fig. 8). If they do not, another three layers of primer should be applied. The mixed primer totally seals the dentinal tubules and bonds to the dentin with a bond of 22 to 33 mega pascal^.^ Allbond Liner F is then applied to the dentin-enamel surface (Fig. 9) using a fine-tipped soft brush, and after 30 seconds it is gently air blown (Fig. lo). After a metal matrix band is placed and wedged, silver amalgam alloy is incrementally condensed after which the matrix band is removed and the silver amalgam restoration is carved to anatomic detail (Fig. 11)(alternate materials: Etch N Seal/Tenure Bond, Amalgam Bond).
Figure 3. Application of All Etch.
Figure 4. The etched preparation is washed and air dried.
Figure 6. SEM of dentin surface after application of All Etch (courtesy of Byoung Suh,Bisco Inc.).
Figure 2. Maxillary premolar with weakened cusps.
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JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2 March/April 1992
pieure 6. The preparation moistened with water.
Pygure 9. All Bond Liner F.
Flgrue 7. Application of five coats of mixed primer to the preparation.
Figure 10. Application of All Bond Liner F.
CONCLUSION The bonded silver amalgam restoration has a number of advantages such as: 1. Retention is excellent. 2. There is no need for pins. 3. The remaining cusps are strengthened due to the bonding process and accordingly, future cuspal fracture is highly unlikely (Fig. 12) since bonded amalgam restorations strengthen cusps in much the same manner as bonded composites (Fig. 13). 4. There is no postoperative sensitivity since marginal leakage is totally eliminated.
Figure 8. Highlyreflective, glossy appearance ofdentin-enamel after insertion of mixed primer.
56
Bonded Silver Amalgam Restorations
pisure 11. Completed bonded amalgam restoraqon.
Pigun 13. 8.Bonded composite restoration.
REFERENCES 1. DeSchepper EJ. Cailleteau J G , Roeder L, Powers JM. In uitro tensile bond strengths of amalgam to treated dentin. J Esthet Dent 1991: 3:117-120. 2. Roeder LB. DeSchepper EJ, Powers J M . In uitro bond strength of repaired amalgam with adhesive bonding systems. J Esthet Dent 1991: 3:126-128. 3. Suh BI. AllBond-fourth generation dentin bonding system. J Esthet Dent 1991: 3:139-147.
Figure 12. Polished bonded silver amalgam restoration supPod-
Figure 13. A, Premolar preparation for bonded composite.
57
Although silver amalgam is a strong, stable, technique-insensitive material, its use requires the removal of more intact tooth structure than adhesive materials in order to provide long-term retention. Thus remaining tooth structure is weakened rather than strengthened. Bonded silver amalgam restorations, on the other hand, have excellent retention, don't require pins. strengthen remaining tooth structure, eliminate the likelihood of cuspal fracture, and eliminate postoperative sensitivity.
S
ilver amalgam has been used successfully in dentistry for over a century (Fig. 1).The reasons for the demonstrated success of silver amalgam are many. It is a high strength, dimensionally stable material with excellent physical properties and is totally insoluble in mouth fluids. Further, silver amalgam is a highly "techniques-insensitive"material. That is,it will forgivemany more "manipulative abuses" than other restorative materials including composite resin. In addition, silver amalgam is relatively simple to use. and it is the only "self sealing" restorative material available. One of the major limitations of silver amalgam as a restorative material is that since it is not a bondable material it requires the removal of considerably more intact tooth structure than adhesive materials in order to provide long-termretention. Accordingly.silver amalgam weakens remaining tooth structure rather than strengthening it. This is the main reason that cuspal fracture is fairly common with long-standing silver amalgam restorations. The recent introduction of resin adhesive bonding materials such asAmalgam Bond (Parkell,Farmingdale. NY), AUBond (Liner F)(BiscoInc., Itasca, IL). and Geristore (Den Mat, Santa Maria, CA) for silver amalgam has been greeted with a high degree of enthusiasm by the profession since they allow the opportunity of effecting both amalgam to amalgam repairs and bonded amalgam restorations. Amalgam Bond consists of a 10 percent citric acid/3 percent ferric chloride as a dentin conditioner.aqueous hema (hydroxyethylmethacrylate) as a wetting agent, and 4-META. hema, and methyl methacrylate as the bonding agent.' Allbond Liner F makes use of either 10 percent phosphoric acid or succinic anhydride and hema as dentin conditioning
Figure 1. A 10-year silver amalgam restoration.
agents, NTG-GMA in acetone as a primer, and a proprietary base/catalyst fluoride containing bonding resin. Although a great deal of research has not yet been reported on these systems, DeSchepper et al (1991) have reported mean tensile bond strengths of amalgam to dentin using Allbond range from 10to 11megapascals and comparably very low to nonexistent bond values with the Amalgam Bond system. Roeder et al (1991) reported amalgam to amalgam bond strengths of 3.4to 8.8 megapascals with Allbond and little if any bond strength with Amalgam Bond.2Nonetheless, in a study carried out at the University of Manitoba involving 40 premolar and molar teeth with fractured buccal or lingual cusps in association with preexistent silver amalgam restorations repaired with new amalgam using Amalgam Bond adhesive, no failures were observed over a 1-year recall period. Any one of the three aforementioned materials may be used successfully for amalgam to amalgambonded repairs with a high degree of clinical reliability, and also bonded amalgam restorations may also be fabricated.
*Assistant hfessor. Faculty of Dentistry. University of Manitoba, Winnipeg. Manitoba Address =print requests to Michael Balanko. D.M.D.. Faculty of Denustry. University of Manitoba. Winnipeg.Manitoba M E OW3. 0 1992 Decker Periodicals Inc.
54
Bonded Silver Amalgam Restorations
BONDED AMALGAM RESTORATION Figure 2 shows a maxillary first premolar with severely weakened buccal and lingual cusps. Close examination of the preparation showed a near exposure of the disto-axial wall. Nevertheless, pulp protection is usually unnecessaly since the biologic acceptability of Allbond and Amalgam Bond are very high. All Etch was injected to cover all of the dentin and enamel surfaces of the preparation (Fig. 3) for a 15 to 20-second period followed by washing and drying (Fig. 4). The All Etch etches the enamel, removes the smear layer from the dentin, and opens the dentinal tubules (Fig. 5)without causing pulpal irritation. A moist cotton pledget is then wiped over the dentin surface (Fig. 61, since All Bond bonds better to moist surfaces. All Bond Primer A and B are then mixed and three to five successive coats are applied to the enamel and dentin with a fine-tipped soft brush (Fig. 7) followed by gentle warm air drying and visible light curing. The dentin and enamel surfaces should appear glossy and highly reflective at this stage (Fig. 8). If they do not, another three layers of primer should be applied. The mixed primer totally seals the dentinal tubules and bonds to the dentin with a bond of 22 to 33 mega pascal^.^ Allbond Liner F is then applied to the dentin-enamel surface (Fig. 9) using a fine-tipped soft brush, and after 30 seconds it is gently air blown (Fig. lo). After a metal matrix band is placed and wedged, silver amalgam alloy is incrementally condensed after which the matrix band is removed and the silver amalgam restoration is carved to anatomic detail (Fig. 11)(alternate materials: Etch N Seal/Tenure Bond, Amalgam Bond).
Figure 3. Application of All Etch.
Figure 4. The etched preparation is washed and air dried.
Figure 6. SEM of dentin surface after application of All Etch (courtesy of Byoung Suh,Bisco Inc.).
Figure 2. Maxillary premolar with weakened cusps.
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JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2 March/April 1992
pieure 6. The preparation moistened with water.
Pygure 9. All Bond Liner F.
Flgrue 7. Application of five coats of mixed primer to the preparation.
Figure 10. Application of All Bond Liner F.
CONCLUSION The bonded silver amalgam restoration has a number of advantages such as: 1. Retention is excellent. 2. There is no need for pins. 3. The remaining cusps are strengthened due to the bonding process and accordingly, future cuspal fracture is highly unlikely (Fig. 12) since bonded amalgam restorations strengthen cusps in much the same manner as bonded composites (Fig. 13). 4. There is no postoperative sensitivity since marginal leakage is totally eliminated.
Figure 8. Highlyreflective, glossy appearance ofdentin-enamel after insertion of mixed primer.
56
Bonded Silver Amalgam Restorations
pisure 11. Completed bonded amalgam restoraqon.
Pigun 13. 8.Bonded composite restoration.
REFERENCES 1. DeSchepper EJ. Cailleteau J G , Roeder L, Powers JM. In uitro tensile bond strengths of amalgam to treated dentin. J Esthet Dent 1991: 3:117-120. 2. Roeder LB. DeSchepper EJ, Powers J M . In uitro bond strength of repaired amalgam with adhesive bonding systems. J Esthet Dent 1991: 3:126-128. 3. Suh BI. AllBond-fourth generation dentin bonding system. J Esthet Dent 1991: 3:139-147.
Figure 12. Polished bonded silver amalgam restoration supPod-
Figure 13. A, Premolar preparation for bonded composite.
57
