- Email: [email protected]
An alternative to cast etched retainers
An alternative to cast etched retainers Mohsen Taleghani, D.M.D.,* Karl F. Leinfelder, Akram M. Taleghani, Ph.D., M.P.H.***
D.D.S., M.S.,** and
University of Alabama at Birmingham, School of Dentistry, Birmingham, Ala.
0
ne of the most significant advances in prosthodontics is the development of the resin-bonded retainers or “Maryland Bridge”.‘-3 This system precludes the need for extensive preparation of the abutment teeth. Other advantages include reduced patient treatment and laboratory time and cost. Clinical studies have demonstrated the effectiveness of this treatment,4 which is used in several countries around the world.5, 6 Recently a growing number of dentists in the United States have reported that the restoration is not as effective as previously believed.’ The problem seems to be a separation of the restoration from the prepared abutment teeth. Some patients have been reported to have aspirated or swallowed the restoration. The failure generally occurs at the metal-resin interface with several potential problems. These include improperly etched surfaces of the metal retainer, contamination of the surface before cementation, and incomplete seating of the restoration during the cementation process. Contamination can result from saliva or manual contact with etched surface. Under either condition the luting agent may not flow into the detailed microstructure generated by the electrolytic or chemical etching process. Recently, two alternatives have been recommended for the chemical or electrolytic etching technique. The first consists of placing small crystals of sodium chloride on the surface of the die stone cast in the region where the pattern will be developed.8 The pattern is generated over the small crystals, and the salt crystals in turn are washed away before the investing procedure. This method generates an irregular surface that, after casting, is capable of retaining the cement. Because a number of variables are involved with this technique, it has engendered little interest. Another promising method involves the use of a mesh pattern with a design similar to woven screen wire.9 The pattern is placed on the surface of the cast where the pattern is to be made. Wax is added to this surface and
*Formerly Assistant Professor, General Dentistry Clinic, Division of Patient Services; Currently Associate Professor, General Dentistry Department, Baylor College of Dentistry, Dallas, Tex. **Professor and Director of Clinical Dentistry and Biomaterials Research. ***Assistant Researcher, Department of Oral Biology.
424
Table I. Materials
included
Material
Manufacturer
Harmony
Hard
Mowrey
No. 25
Rexillium
III
Comspan Duralingual
in the study
Bond
Williams Cold Co., Albany, N.Y. W.E. Mowrey Co., St. Paul, Minn. Jeneric Gold Co., Albany, N.Y. L.D. Caulk, Milford, Del. Unitek Corp., Monrovia, Cafif.
TYP@ Type III gold alloy Ag-Pd Base metal Resin Luting Resin Luting
agent
agent
cast in a conventional manner. The routine and periodic location of small undercuts on the surface provide an excellent means for mechanically holding the luting agent. One of the basic advantages of this system is that it can be used with all presently available dental alloys. Electrolytic or chemical etching, on the other hand, can be used on only a limited number of alloys. This study was conducted to determine the effectiveness of this method on the retention of resin luting agents compared with conventional etching techniques.
METHODS AND MATERIAL Three different types of alloys were included in the study. These and the various luting agents used in conjunction with the bonding tests are included in Table I.
Specimen preparation Patterns for all of the specimens were generated from a sheet of baseplate wax by using a cork borer. The resultant disks were 11.5 mm in diameter and 2 mm thick. The Duralingual mesh patterns were then attached to one side of the disks. A scanning electron micrograph of one of these patterns is illustrated in Fig. 1. Next the patterns were sprued in multiples of five, treated with a wetting agent, and invested under vacuum. A gypsum-bonded investment was used in conjunction with the gold alloy, and a phosphate-bonded investment was used for the base metal and silver-palladium alloys. All of the investments were burned out and cast in accordance with the manufacturer’s recommendations. The gold alloy was cast by using an electric springOCTOBER
1987
VOLUME
58
NUMBER
4
AN ALTERNATIVE
TO CAST ETCHED
Fig. 1. SEM photograph tion X50.)
RETAINERS
of mesh pattern.
(Magnifica-
Fig. 3. Mounting ian device.
Fig. 2. III.
Cast mesh patterns
specimen
with
wound casting machine; the remaining alloys were cast with an induction casting unit. After removal from the investment, the castings were sandblasted with fine particles of alumina (Fig. 2), cut from the sprue, and cleaned with a 15% solution of HCl. Each specimen was cleaned ultrasonically for at least 15 minutes. The samples were then washed in deionized water and dried in preparation for storage. Each of the compositions were divided into three groups and subjected to each of the following conditions: (1) chemically etching with the cast screen mesh on the surface, (2) chemical etching without the cast screen mesh on the surface, and (3) the cast screen mesh on the unetched surface. The gold alloy was not subjected to etching because no etching solution for this alloy is available. The silverpalladium alloys were electrolytically etched for 3 minutes in the following electrolyte: 4 ml water, 10 gm NaF, 10 gm NaNO,, and sufficient water to make 200 OF PROSTHETIC
DENTISTRY
of modified
Kemper/Kil-
Rexillium Fig. 4. ratus.
THE JOURNAL
cylinders
Close-up of specimen in bond-alignment
appa-
ml. The current was held constant at 250 mA/cm’. The castings were then cleaned ultrasonically in a solution consisting of 10 ml each of concentrated sulfuric and phosphoric acid and 180 ml of water, washed with deionized water, and stored for subsequent bonding. The base metal alloys were electrolytically etched in a 10% solution of sulfuric acid for 3 minutes at 300 mA/cm’. They then were cleaned ultrasonically for 15 minutes in an 18% solution of HCI, washed in deionized water, and stored for subsequent bonding. Bonding
procedure
The bond strengths of the two resin luting agents to the different alloys were determined by using a modified Kemper/Kilian device. ‘O The system was designed to maintain a proper and constant alignment during 425
TALEGHANI,
Fig. 5. SEM photograph of cast mesh surface of Rexil-
lium III using debubbleizer. (Magnification
x50.)
LEINFELDER,
AND
TALEGHANI
Fig. 7. SEM photograph of cast mesh surface of silver palladium. (Magnification x50.)
RESULTS
Fig. 6.
SEM photograph of cast mesh surface of Rexillium III without using debubbleizer. (Magnification x50.)
cementation and debonding (Fig. 3). A close-up of the specimen-holding device is shown in Fig. 4. After the disk was inserted in the sample holder, the metal surface was coated with the appropriate bonding agent. The opposing brass cup was filled with one of the resin luting agents and placed in position. A weight of 500 gm was placed on top of the assembly and maintained for at least 10 minutes as the luting agent polymerized. All of the bonded samples were then thermocycled 500 times in water at temperatures of 5” and 50” C. The alignment device was used and each specimen was transferred to the Instron Universal testing machine (Instron Corp., Canton, Mass.) for debonding at a crosshead speed of 0.5 cm/min. The results of the various combinations were subjected to a NewmanKeuls multiple range test. 426
The successin obtaining a satisfactory reproduction of the mesh configuration on the casting surface depended on the use of a wetting agent. Scanning electron micrographs of the cast mesh surface with and without the use of the “debubbleizer” or wetting agent are shown in Figs. 5 and 6. As expected, the use of the wetting agent resulted in a more detailed surface because the wax mesh surface is not easily wetted by casting investment. The base metal alloy consistently generated a more detailed surface than either the silver-palladium or the gold alloy (Fig. 7). The bond strength values for the two different luting agents and the various alloys for each of the three different treatments are shown in Figs. 8 through 10. Standard deviations are given at the top of each histogram. No values are given for the gold in the etched condition because no agents are available for this purpose. All other conditions, however, are represented by bar graphs. The unetched meshed surfaces generally were as effective as those that were etched only. Furthermore, the effect of alloy type had little influence on bond strength. These relationships can best be demonstrated by comparing the data on an individual basis as seen in Tables II through V. The effect of the surface conditioning on the base metal alloy is shown in Table II. The values for the meshed surfaces were at least as good as for the other conditions included in the study. In general, the values obtained with the Comspan luting agent were higher than those obtained with the Duralingual bonding agent, although the differences were not statistically significant & CO.05). The effect of surface conditioning silver-palladium alloy was essentially the same as those with the base metal compositions (Table III). With Rexillium base metal, the bond strength values for the Ag-Pd alloys
OCTOBER
1987
VOLUME
58
NUMBER
4
AN ALTERNATIVE
TO CAST ETCHED
RETAINERS
COYSPAN DURALINGUAL
3. 1
0 m
50
40 h
ii
8 a
4o 30
9.1
20
9 10 3
1
L ETCH
2 d
3o
IJJ
20
ii P
10
MESH
ETCH
MESH/ETCH
COMSf’AN q n
DURALINGUAL
MESH
MESH/ETCH
SURFACE CONDITION
SURFACE CONDITION
Fig. 8. Histogram demonstrating bond strengths of Rexillium III subjected to various surfacing treatments. Values are given for two different luting agents. Standard deviations values in pounds are given at top of each bar.
Fig. 9. Histogram demonstrating bond strength of silver palladium subjected to various surfacing treatments. 40 -
generally were higher for Comspan resin compared with Duralingual bond. Again, differences in values for the gold alloys with the two different luting agents were also detected. Differences in values for the various conditions were not significant at p <.05. The pooled values of the different types of luting agents used in conjunction with the different alloys and different surface conditions are shown in Table IV. Highest bond strength values were obtained with the base metal alloy in which the mesh was used with or without electrolytically etching. In both instances the values for these two conditions were not significant. The pooled values for the different surface treatment used in conjunction with the different bonding agents are given in Table V. In pooling the data no significant differences among the alloys could be detected for either bonding agent. Furthermore, the differences in bond strengths for the two luting agents were not statistically significant.
DISCUSSION From the results of this study it is apparent that the mesh system used is an acceptable method for bonding resin to metal surfaces. Indeed, the bond strength was always at least as great as that when the metal surfaces were only etched. The meshed surface offers a number of advantages over conventional methods. First, the system provides a means for bonding virtually any resin material to any type of dental casting alloy. Although chemical and electrolytic etching are used routinely with good results, the number of alloy systems that respond to etching is limited. Alloys of gold, palladium-silver, and some of the newer alloys cannot be etched adequately.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
COMSPAN 30 -
DURALINGUAL
0
n
T 03 3
20 -
8
MESH
SURFACE CONDITION
Fig. 10. Histogram demonstrating gold alloy.
bond strength of
Another advantage to the mesh system is that a properly conditioned surface is recognizable at relatively low magnification and perhaps with the unaided eye. Conventional etched surfaces, cannot be examined readily to determine their potential for bonding. The mesh system eliminates the need for equipment and processes associated with chemical or electrolytic etching. Finally, the potential for variability in preparing an appropriate surface is reduced. Examination by scanning electron micrography showed that the use of a wetting agent improved the castability of the mesh pattern with more detail and greater depth, enhancing the retentive characteristics of the resin luting agent. In general, the bond strengths associated with the two different resin luting agents were different. The values of Comspan resin were greater than those for the Duralingual agent regardless of the metal tested. Examination of
427
TALEGHANI,
LEINFELDER,
AND
TALEGHANI
Table II. Effect of surface treatment strength (lbs) of base metal alloy Metal Cement Comspan Duralingual
on bond
conditioning
Etched
Mesh
Mesh & etched
34.2 25.6
42.4 33.0
41.8 31.8
Table III. Effect of surface treatment bond strength (lbs) of Ag-Pd alloy Metal Cement Comspan Duralingual
Surface treatment Alloy
Etched
Mesh
Mesh + etch
Base metal Ag-Pd Gold
29.9 32.6 -
37.7 27.8 30.0
36.8 33.0 -
on
conditioning
Etched
Mesh
Mesh & etched
34.0 31.2
32.0 23.6
37.0 28.2
the fractured interfaces with scanning electron microscopy showed no. significant differences. Consequently, it ‘is possible that the differences in bond strengths could be related to the mechanical properties inherent in the luting agents themselves. The uses of electrolytic etching in conjunction with the mesh tended to enhance the retentive characteristics of the Ag-Pd alloys but not those made of the base metal. The improvements, although not statistically significant (p <.05), could .be attributed to the additional defects created by the etching process. CONCLUSIONS The results of this study demonstrated that the cast mesh surface can serve as an alternative to chemical or electrolytic etching. Furthermore, the mesh systems permits the dentist to bond any metal to etched enamel surfaces, especially gold alloys and those with a high palladium content, which have no etchants. Another advantage is the dentists’ ability to determine the appropriate surface conditioning of the metal. In using electrolytic etching, it is difficult for the dentist or dental technician to determine whether the surface is appropriately prepared for retention of the resin luting agent.‘In addition, the elimination of the etching process is an advantage from the standpoint of cost, time, and possible health hazards. Finally, from a clinical point of view, it should be noted that the grey discoloration commonly transmitted through the enamel when cast etched retainers are used was not apparent with the mesh system. The reason may
428
Table IV. Pooled bond strengths (lbs) of two cements for the three alloys after different surface treatment
Table V. Pooled bond strengths (lbs) for the different surface treatments used in conjunction with the three alloys Alloy
Comspan
Rexillium Ag-Pd Au
Duralingual
39.5 34.6 34.8
31.1 27.0 25.2
be related to a lack of complete metal contact on the lingual surface to which the retainer is attached. REFERENCES 1. 2.
3.
4. 5. 6. 7. 8. 9.
10.
Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PRO.STHETDENT 1973;30:418-23. Howe DF, Denehy GE. Anterior fixed partial denture utilizing the acid-etch technique and a cast metal framework. J PRO~THET DENT 1977;37:28-31. Livaditis GJ, Thompson VP. Etched castings: an improved retentive mechanism for resin-bonded retainers. J PROSTHET DENT 1982;47:52-8. Livaditis GJ. Resin-bonded cast restorations: clinical study. Int J Periodontics Restorative Dent 1981;1:70-9. Goto G. Adhesive bridge characteristics and clinical considerations. Shikai Tenlo 1982;60:687-94. Rossein K. An alternative bridge. Quintessenz 1982;33:193341. Gratton E. Acid-etch resin-retained bridge success reported. Ont Dent 1983;60:9-19. Hudgins TL, Moon PC, Knap FJ. Particle-roughened resinbonded retainers. J PROSTHETDENT 1985;53:471-6. Shen G, Forbes J, Boettcher R, Dvivedi N, Morrow R. Resin-bonded bridge bond strength using a cast mesh technique [Abstract]. J Dent Res 1983;62:221. Kemper RM, Kilian KJ. New system for tensile bond strength testing [Abstract]. J Dent Res 1976;55:138.
Reprint requests to: DR. MOHSEN TALEGHANI BAYLORCOLLEGEOF DENTISTRY 3302 GA.STONAVE. DALLAS, TX 75246
OCTOBER
1987
VOLUME
58
NUMBER
4
D.D.S., M.S.,** and
University of Alabama at Birmingham, School of Dentistry, Birmingham, Ala.
0
ne of the most significant advances in prosthodontics is the development of the resin-bonded retainers or “Maryland Bridge”.‘-3 This system precludes the need for extensive preparation of the abutment teeth. Other advantages include reduced patient treatment and laboratory time and cost. Clinical studies have demonstrated the effectiveness of this treatment,4 which is used in several countries around the world.5, 6 Recently a growing number of dentists in the United States have reported that the restoration is not as effective as previously believed.’ The problem seems to be a separation of the restoration from the prepared abutment teeth. Some patients have been reported to have aspirated or swallowed the restoration. The failure generally occurs at the metal-resin interface with several potential problems. These include improperly etched surfaces of the metal retainer, contamination of the surface before cementation, and incomplete seating of the restoration during the cementation process. Contamination can result from saliva or manual contact with etched surface. Under either condition the luting agent may not flow into the detailed microstructure generated by the electrolytic or chemical etching process. Recently, two alternatives have been recommended for the chemical or electrolytic etching technique. The first consists of placing small crystals of sodium chloride on the surface of the die stone cast in the region where the pattern will be developed.8 The pattern is generated over the small crystals, and the salt crystals in turn are washed away before the investing procedure. This method generates an irregular surface that, after casting, is capable of retaining the cement. Because a number of variables are involved with this technique, it has engendered little interest. Another promising method involves the use of a mesh pattern with a design similar to woven screen wire.9 The pattern is placed on the surface of the cast where the pattern is to be made. Wax is added to this surface and
*Formerly Assistant Professor, General Dentistry Clinic, Division of Patient Services; Currently Associate Professor, General Dentistry Department, Baylor College of Dentistry, Dallas, Tex. **Professor and Director of Clinical Dentistry and Biomaterials Research. ***Assistant Researcher, Department of Oral Biology.
424
Table I. Materials
included
Material
Manufacturer
Harmony
Hard
Mowrey
No. 25
Rexillium
III
Comspan Duralingual
in the study
Bond
Williams Cold Co., Albany, N.Y. W.E. Mowrey Co., St. Paul, Minn. Jeneric Gold Co., Albany, N.Y. L.D. Caulk, Milford, Del. Unitek Corp., Monrovia, Cafif.
TYP@ Type III gold alloy Ag-Pd Base metal Resin Luting Resin Luting
agent
agent
cast in a conventional manner. The routine and periodic location of small undercuts on the surface provide an excellent means for mechanically holding the luting agent. One of the basic advantages of this system is that it can be used with all presently available dental alloys. Electrolytic or chemical etching, on the other hand, can be used on only a limited number of alloys. This study was conducted to determine the effectiveness of this method on the retention of resin luting agents compared with conventional etching techniques.
METHODS AND MATERIAL Three different types of alloys were included in the study. These and the various luting agents used in conjunction with the bonding tests are included in Table I.
Specimen preparation Patterns for all of the specimens were generated from a sheet of baseplate wax by using a cork borer. The resultant disks were 11.5 mm in diameter and 2 mm thick. The Duralingual mesh patterns were then attached to one side of the disks. A scanning electron micrograph of one of these patterns is illustrated in Fig. 1. Next the patterns were sprued in multiples of five, treated with a wetting agent, and invested under vacuum. A gypsum-bonded investment was used in conjunction with the gold alloy, and a phosphate-bonded investment was used for the base metal and silver-palladium alloys. All of the investments were burned out and cast in accordance with the manufacturer’s recommendations. The gold alloy was cast by using an electric springOCTOBER
1987
VOLUME
58
NUMBER
4
AN ALTERNATIVE
TO CAST ETCHED
Fig. 1. SEM photograph tion X50.)
RETAINERS
of mesh pattern.
(Magnifica-
Fig. 3. Mounting ian device.
Fig. 2. III.
Cast mesh patterns
specimen
with
wound casting machine; the remaining alloys were cast with an induction casting unit. After removal from the investment, the castings were sandblasted with fine particles of alumina (Fig. 2), cut from the sprue, and cleaned with a 15% solution of HCl. Each specimen was cleaned ultrasonically for at least 15 minutes. The samples were then washed in deionized water and dried in preparation for storage. Each of the compositions were divided into three groups and subjected to each of the following conditions: (1) chemically etching with the cast screen mesh on the surface, (2) chemical etching without the cast screen mesh on the surface, and (3) the cast screen mesh on the unetched surface. The gold alloy was not subjected to etching because no etching solution for this alloy is available. The silverpalladium alloys were electrolytically etched for 3 minutes in the following electrolyte: 4 ml water, 10 gm NaF, 10 gm NaNO,, and sufficient water to make 200 OF PROSTHETIC
DENTISTRY
of modified
Kemper/Kil-
Rexillium Fig. 4. ratus.
THE JOURNAL
cylinders
Close-up of specimen in bond-alignment
appa-
ml. The current was held constant at 250 mA/cm’. The castings were then cleaned ultrasonically in a solution consisting of 10 ml each of concentrated sulfuric and phosphoric acid and 180 ml of water, washed with deionized water, and stored for subsequent bonding. The base metal alloys were electrolytically etched in a 10% solution of sulfuric acid for 3 minutes at 300 mA/cm’. They then were cleaned ultrasonically for 15 minutes in an 18% solution of HCI, washed in deionized water, and stored for subsequent bonding. Bonding
procedure
The bond strengths of the two resin luting agents to the different alloys were determined by using a modified Kemper/Kilian device. ‘O The system was designed to maintain a proper and constant alignment during 425
TALEGHANI,
Fig. 5. SEM photograph of cast mesh surface of Rexil-
lium III using debubbleizer. (Magnification
x50.)
LEINFELDER,
AND
TALEGHANI
Fig. 7. SEM photograph of cast mesh surface of silver palladium. (Magnification x50.)
RESULTS
Fig. 6.
SEM photograph of cast mesh surface of Rexillium III without using debubbleizer. (Magnification x50.)
cementation and debonding (Fig. 3). A close-up of the specimen-holding device is shown in Fig. 4. After the disk was inserted in the sample holder, the metal surface was coated with the appropriate bonding agent. The opposing brass cup was filled with one of the resin luting agents and placed in position. A weight of 500 gm was placed on top of the assembly and maintained for at least 10 minutes as the luting agent polymerized. All of the bonded samples were then thermocycled 500 times in water at temperatures of 5” and 50” C. The alignment device was used and each specimen was transferred to the Instron Universal testing machine (Instron Corp., Canton, Mass.) for debonding at a crosshead speed of 0.5 cm/min. The results of the various combinations were subjected to a NewmanKeuls multiple range test. 426
The successin obtaining a satisfactory reproduction of the mesh configuration on the casting surface depended on the use of a wetting agent. Scanning electron micrographs of the cast mesh surface with and without the use of the “debubbleizer” or wetting agent are shown in Figs. 5 and 6. As expected, the use of the wetting agent resulted in a more detailed surface because the wax mesh surface is not easily wetted by casting investment. The base metal alloy consistently generated a more detailed surface than either the silver-palladium or the gold alloy (Fig. 7). The bond strength values for the two different luting agents and the various alloys for each of the three different treatments are shown in Figs. 8 through 10. Standard deviations are given at the top of each histogram. No values are given for the gold in the etched condition because no agents are available for this purpose. All other conditions, however, are represented by bar graphs. The unetched meshed surfaces generally were as effective as those that were etched only. Furthermore, the effect of alloy type had little influence on bond strength. These relationships can best be demonstrated by comparing the data on an individual basis as seen in Tables II through V. The effect of the surface conditioning on the base metal alloy is shown in Table II. The values for the meshed surfaces were at least as good as for the other conditions included in the study. In general, the values obtained with the Comspan luting agent were higher than those obtained with the Duralingual bonding agent, although the differences were not statistically significant & CO.05). The effect of surface conditioning silver-palladium alloy was essentially the same as those with the base metal compositions (Table III). With Rexillium base metal, the bond strength values for the Ag-Pd alloys
OCTOBER
1987
VOLUME
58
NUMBER
4
AN ALTERNATIVE
TO CAST ETCHED
RETAINERS
COYSPAN DURALINGUAL
3. 1
0 m
50
40 h
ii
8 a
4o 30
9.1
20
9 10 3
1
L ETCH
2 d
3o
IJJ
20
ii P
10
MESH
ETCH
MESH/ETCH
COMSf’AN q n
DURALINGUAL
MESH
MESH/ETCH
SURFACE CONDITION
SURFACE CONDITION
Fig. 8. Histogram demonstrating bond strengths of Rexillium III subjected to various surfacing treatments. Values are given for two different luting agents. Standard deviations values in pounds are given at top of each bar.
Fig. 9. Histogram demonstrating bond strength of silver palladium subjected to various surfacing treatments. 40 -
generally were higher for Comspan resin compared with Duralingual bond. Again, differences in values for the gold alloys with the two different luting agents were also detected. Differences in values for the various conditions were not significant at p <.05. The pooled values of the different types of luting agents used in conjunction with the different alloys and different surface conditions are shown in Table IV. Highest bond strength values were obtained with the base metal alloy in which the mesh was used with or without electrolytically etching. In both instances the values for these two conditions were not significant. The pooled values for the different surface treatment used in conjunction with the different bonding agents are given in Table V. In pooling the data no significant differences among the alloys could be detected for either bonding agent. Furthermore, the differences in bond strengths for the two luting agents were not statistically significant.
DISCUSSION From the results of this study it is apparent that the mesh system used is an acceptable method for bonding resin to metal surfaces. Indeed, the bond strength was always at least as great as that when the metal surfaces were only etched. The meshed surface offers a number of advantages over conventional methods. First, the system provides a means for bonding virtually any resin material to any type of dental casting alloy. Although chemical and electrolytic etching are used routinely with good results, the number of alloy systems that respond to etching is limited. Alloys of gold, palladium-silver, and some of the newer alloys cannot be etched adequately.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
COMSPAN 30 -
DURALINGUAL
0
n
T 03 3
20 -
8
MESH
SURFACE CONDITION
Fig. 10. Histogram demonstrating gold alloy.
bond strength of
Another advantage to the mesh system is that a properly conditioned surface is recognizable at relatively low magnification and perhaps with the unaided eye. Conventional etched surfaces, cannot be examined readily to determine their potential for bonding. The mesh system eliminates the need for equipment and processes associated with chemical or electrolytic etching. Finally, the potential for variability in preparing an appropriate surface is reduced. Examination by scanning electron micrography showed that the use of a wetting agent improved the castability of the mesh pattern with more detail and greater depth, enhancing the retentive characteristics of the resin luting agent. In general, the bond strengths associated with the two different resin luting agents were different. The values of Comspan resin were greater than those for the Duralingual agent regardless of the metal tested. Examination of
427
TALEGHANI,
LEINFELDER,
AND
TALEGHANI
Table II. Effect of surface treatment strength (lbs) of base metal alloy Metal Cement Comspan Duralingual
on bond
conditioning
Etched
Mesh
Mesh & etched
34.2 25.6
42.4 33.0
41.8 31.8
Table III. Effect of surface treatment bond strength (lbs) of Ag-Pd alloy Metal Cement Comspan Duralingual
Surface treatment Alloy
Etched
Mesh
Mesh + etch
Base metal Ag-Pd Gold
29.9 32.6 -
37.7 27.8 30.0
36.8 33.0 -
on
conditioning
Etched
Mesh
Mesh & etched
34.0 31.2
32.0 23.6
37.0 28.2
the fractured interfaces with scanning electron microscopy showed no. significant differences. Consequently, it ‘is possible that the differences in bond strengths could be related to the mechanical properties inherent in the luting agents themselves. The uses of electrolytic etching in conjunction with the mesh tended to enhance the retentive characteristics of the Ag-Pd alloys but not those made of the base metal. The improvements, although not statistically significant (p <.05), could .be attributed to the additional defects created by the etching process. CONCLUSIONS The results of this study demonstrated that the cast mesh surface can serve as an alternative to chemical or electrolytic etching. Furthermore, the mesh systems permits the dentist to bond any metal to etched enamel surfaces, especially gold alloys and those with a high palladium content, which have no etchants. Another advantage is the dentists’ ability to determine the appropriate surface conditioning of the metal. In using electrolytic etching, it is difficult for the dentist or dental technician to determine whether the surface is appropriately prepared for retention of the resin luting agent.‘In addition, the elimination of the etching process is an advantage from the standpoint of cost, time, and possible health hazards. Finally, from a clinical point of view, it should be noted that the grey discoloration commonly transmitted through the enamel when cast etched retainers are used was not apparent with the mesh system. The reason may
428
Table IV. Pooled bond strengths (lbs) of two cements for the three alloys after different surface treatment
Table V. Pooled bond strengths (lbs) for the different surface treatments used in conjunction with the three alloys Alloy
Comspan
Rexillium Ag-Pd Au
Duralingual
39.5 34.6 34.8
31.1 27.0 25.2
be related to a lack of complete metal contact on the lingual surface to which the retainer is attached. REFERENCES 1. 2.
3.
4. 5. 6. 7. 8. 9.
10.
Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PRO.STHETDENT 1973;30:418-23. Howe DF, Denehy GE. Anterior fixed partial denture utilizing the acid-etch technique and a cast metal framework. J PRO~THET DENT 1977;37:28-31. Livaditis GJ, Thompson VP. Etched castings: an improved retentive mechanism for resin-bonded retainers. J PROSTHET DENT 1982;47:52-8. Livaditis GJ. Resin-bonded cast restorations: clinical study. Int J Periodontics Restorative Dent 1981;1:70-9. Goto G. Adhesive bridge characteristics and clinical considerations. Shikai Tenlo 1982;60:687-94. Rossein K. An alternative bridge. Quintessenz 1982;33:193341. Gratton E. Acid-etch resin-retained bridge success reported. Ont Dent 1983;60:9-19. Hudgins TL, Moon PC, Knap FJ. Particle-roughened resinbonded retainers. J PROSTHETDENT 1985;53:471-6. Shen G, Forbes J, Boettcher R, Dvivedi N, Morrow R. Resin-bonded bridge bond strength using a cast mesh technique [Abstract]. J Dent Res 1983;62:221. Kemper RM, Kilian KJ. New system for tensile bond strength testing [Abstract]. J Dent Res 1976;55:138.
Reprint requests to: DR. MOHSEN TALEGHANI BAYLORCOLLEGEOF DENTISTRY 3302 GA.STONAVE. DALLAS, TX 75246
OCTOBER
1987
VOLUME
58
NUMBER
4