- Email: [email protected]
Surface treatment of nonprecious alloys for adhesion-fixed partial dentures
COIUCLUSION The present investigation was conducted to determine the role of Mn in alloy-porcelain chemical adherence. The preferential oxidation of Mn during degassing and its migration into porcelain strongly suggest that Mn is a contributing factor in the chemical bonding between a commercial nickel-chromium alloy and dental porcelain. Alloy-porcelain chemical adherence is controlled by multicomponent oxidation, diffusion, and interaction. Thus the role of other oxidation metals in the chemical interaction should be considered in future research.
5. 6. I. 8. 9.
10.
REFERENCES 1. Sred 1R, McLean JW: The strength of metal-ceramic bonds with base metals containing chromium. Br Dent J 132~232, 1972. 2. Williams TRP, Johnson CE, Winchell PG. Phillips RW: Be, Li, and Na distribution near a porrelain/Ni alloy interface shown by ion microprobe mass analysis. J Dent Res 57~233, 1978. 3. Williams TRP, Winchell PG, Phillips RW: Dental porcelain/ Ni alloy interface reactions and their efl’ective prevemion. J Dent Kes 57:583, 1978. 4. ltnusavice KJ. Ringle RD, Fairhurst CW: Adherence comrol-
Il.
ling elements in ceramic-metal systems. II. NI II< ( I !I%,‘1 ~trms. New York, 1958, McGraw-Hill Book Co, Ini. ;’ i>-i Garter JM, AI-Mudafar J, Sorensen SIX .2dti~Tt’llw or ;, nickel-chromium alloy and porcelain. J PROSIIIET I)I.XT 41:167, 1979. Douglass DL, Armijo JS: The eflec~ of silicon ;~nti rrq.w+nesc on the oxidation mechanism of Ni-20 Cr. Oxidalitm Xle\:ds 2307, 1970. Tesk Jh: Selection and characlrristics-Nj~kel ,md itax meuls. In ‘tlternalives tn Gold Alloys in Dentistrc. I)t(EW Puhliwti0n (NIH), 1977~ p 71.
Kcprlril ,-l’c/?rc\/\ /iI: DR. N. K. SARKAR
LOUISIANA STATE UNIVERSITY SCHOOLof DENTISTRY NEW ORLEANS,LA 70119-2799
Takuo Tanaka, D.R.S., Ph.D.,* Erilca F~jiyama, D.DS.,** Mm&i Akio Takaki, D.D.S., Ph.D.,*** and M$&tru AM&a, D.D,S., P&D.****
p D*Des.,**
University of Nagasaki, School of Dentistry, Nagasaki, Japan
A
new prosthetic restoration attracting mapy dentists is the adhesion-fixed partial denture. The adhesionfixed partial denture requires minimal tooth preparation and is easier to construct and manipulate than are conventional fixed partial dentures. To attach an adhesion-fixed partial denture to abutment teeth, resin material must be bonded to the tooth and metal framework. The tooth surfaces require etching with acid while the wing portions of fixed partial dentures are perforated with small tapered h01es’~~or the inside of the metal is electroiytically etched3,4to ensure mechanical bonding with the resin. Research of adhesive resins for bonding has been *i\ssociate Professor, Department of Fixed Prasthodontics. **Research Associate, Department of Fixed Prosthodontics. *** Leclurer, Department of Fixed Prosthodontics. ****Professor and Chairman, Department of Fixed Prosthodonlics 456
intense. A new adhesive resin, MM/EMMA, with 5% weight 4-m&acryloxyetbyl trim&tate anhydride (4META), initiated by a tri-N-butyl &raz~e~,’ has been intraduced. this adhesive resin acihe~~ to tooth enamel as well as to the oxidized sua&oes of t&z& aUoys.7’” Two methods of treatmat, an&c o&Wion9 and nitfic acid dipping,’ were developed for n~q~txSous dloys. However, the adhesion from these me@+% was hot water resistant and res&s$ in c&icaf f&&we.
manganate. A bonding
APRIL
1986
VOLUME
55
NUMBER
4
NONPRECIOUS
ALLOYS
Table I. Alloys
IN ADHESION-FIXED
PARTIAL
DENTURES
used in this experiment
Commercial name of alloy Ni-Cr system Rexillium SB-Bondloy Co-Cr system Biocast Durallium JD
Component Manufacturer Jeneric Gold (USA) Towa Giken (Japan) Jeneric Gold Jelenko (USA)
Ni
Cr
co
Others
86.0 56.4
8.5 17.4
-
5.5 26.2
-
32.0 26.0
62.0 68.0
6.0 6.0
surface treatment of base metal alloys and presents examples of clinical application for the adhesion-fixed partial denture.
MATERIAL AND METHODS Fabrication of metal frames Four nonprecious alloys were used for this study, and the components are reported in Table I. The alloys were cast as flat plate metal frames, IO by IO by 2 mm, according to the manufacturer’s instructions. The surface of the cast metal frames was air brushed with alumina powder having a mean diameter of 50 pm and washed in neutral detergent solution for IO minutes and then in distilled water for I minute with ultrasonic wave. The water remaining on the metal plates was dried by clean compressed air. Half of the metal frames were tested immediately for adhesion while the remaining half was also treated with an oxidizing agent before adhesion.
Immersion in an oxidizing
solution
The oxidizing solution was composed of 3% weight aqueous sulfuric acid with 1% weight potassium permanganate. The metal frames were immersed in the oxidizing solution at room temperature for 2 minutes, washed in ultrasonic wave in distilled water for I minute, and dried for adhesion test.
Preparation of specimens for adhesion The treated surface of the metal specimen was fastened to an acrylic resin rod by the adhesive resin Orthomite Super-Bond (Sun Medical Co., Kyoto, Japan)‘, 6 and mounted to the testing machine. Fig. 1 displays the specimens for the bonding test and the circle of adhesive resin with a diameter of 5 mm. For SB-Bondloy, adhesion specimens made of the metal frames treated by the anodic oxidation device EZ-OXISOR9 (Towagiken Co., Kyoto, Japan) were used for comparison.
Measurement of tensile bonding strength Metal specimens were placed alternately in water at 4” + I” C and 60” + 2” C for 60 seconds and the thermal cycle was repeated 2000 times before testing. THE IOURNAL
OF PROSTHETIC
DENTISTRY
(wt-%) Indicated
restoration
Metal-ceramic Metal-ceramic
crown crown
Metal-ceramic crown Metal base denture
The amount of force required to separate the acrylic resin rod from the metal casting was measured at a cross-head speed of 2 mm/min with a universal testing machine (Autograph DCS-500; Shimazu Mfg. Co., Kyoto, Japan). Tests were performed on IO specimens for each test. Specimens prepared by Biocast and SBBondloy were also tested after thermal cycling 10,000 times.
RESULTS The effect of oxidation of Ni-Cr alloys with thermal cycling 2000 times is shown in Fig. 2. The adhesive durability after the thermal cycling was improved by oxidation after air brushing with alumina, and the bonding force of approximately 250 kg/cm* was maintained after thermal cycling 2000 times. The bonding strength before the thermal cycling without oxidation was 250 kg/cm2 but was reduced to less than 180 kg/cm2 after thermal cycling. A higher bonding strength and adhesive durability for Co-Cr alloys with or without oxidation is shown in Fig. 3. This differed from the Ni-Cr alloy specimens. Co-Cr alloys treated by oxidation demonstrated less adhesive durability than did untreated specimens. Bonding strength and SD of the alloys after thermal cycling 2000 times are listed in Table II. The test specimens treated by oxidation revealed the least SD. The excessive SD of SB-Bondloy with EZ-OXISOR suggested that the bonding strength of this system was unreliable. It was concluded that a stable and high bonding strength with a durable adhesion could be obtained by air brushing with alumina and supersonic wave washing for Co-Cr alloys. Results of the adhesion test under severe conditions by increasing the number of thermal cycles is shown in Fig. 4. Biocast subjected to sandblasting and supersonic wave washing produced a remarkably durable adhesion of 220 kg/cm2 after thermal cycling 10,000 times. Conversely, the bonding strength of SB-Bondloy treated by EZOXISOR was recorded at only 140 kg/cm2. Fractured surfaces of the specimens caused by the tension test after thermal cycling 10,000 times are shown in Fig. 5. Biocast specimens recorded cohesive fracture at 457
TANAKA
ET AL
TaMa IL The tensile bond stren@h (&g/cm2) dter 2df60 +hennal cycles to rtickel-chromium and c&&-chromium alloys Commercial name of alloy
Method Air brushed
Ni-Cr system Rexillium SB-Bondloy SB-Bondloy Co-Cr system Biocast Durailium JD *Oxidized
Fig. 1. Specimen for adhesion test. (A, acrylic rod for a handle; B, alloy for test; C, adhesive resin.)
the resin-metal interface whereas abundant diffusion of water from the marginal region was noted with SBBondloy.
DISCUSSiON The resin including 4-META adheres strongly to nonprecious metals (i.e., Ni-Cr alloys). The thin oxide film produced on the surface of alloys adheres with 4-META strongly. For this reason, many attempts have been made to create a suitable oxide film artificially on the surface of nonprecious alloys, particularly Ni-Cr alloys. 7,9These methods were not applicable in clinical practice because they required prolonged treatment with concentrated nitric acid. Anodic oxidation advocated by Yamashita et al.9 had a practical treatment time without volatile acids and was widely used for the adhesion-fixed partial denture. However, an effective surface treatment method for a stable oxide film has been sought because anodic oxidation provided unreliable bonding. The surface treatment suggested in this study improved the bonding strength and handling properties, with safer manipulation. This new method uses an oxidation agent of potassium manganate and dilute sulfuric acid. The oxidation agent uses potassium manganate, which precipitates an oxidation effect in an acid solution and also controls the strength of oxidation by varying the pH. The density of the sulfuric acid was 0.3% weight and 1% for potassium manganate designed 458
electrolytically
of surface
treatment -Air brushed and oxidized .._ ,_
148 * 26 186 + 41 -
243 255 292
k 13 + 30 ?x67%
+ +
241 238
+ 10 -+ 31
270 245
with
33 28
EZ-OXISOR.
to treat the alloys within 2 r@nutes. Treatment may be shortened with 0.5% weight den&y sulfuric acid and increasing the concentration of the potassium manganate. If the solution of oxidation agent is left for more than 1 day, the potassium manganate is reduced to manganese dioxide resulting in a weak oxidation solution. Therefore the solution should be used within a few hours after preparation. If Ni-Cr alloys are treated with the oxidation agent, adhesion is improved substantiaIly. However, if the treatment is prolonged, the adhesion decreases dramatically. For instance, the treatment time of 10 minutes reduced the bonding strength of SB-I@~dIoy to Zt;D + 12 kg/cm2 after thermal cycling 2000 times. It is hypothesized that the extension of treatment time increases the thickness of the oxide film and a more stable structure develops, lowering the reactivity with the adhesive. Treatment of an adhesive surface by sandbIa&ng with alumina is also a critical procedure. Polishing SB-Bondloy with a Carborundum point followed by oxidation yielded the bonding strength of only 107 + 16 kg/cm2 after thermal cycling 300 times. This value is lower than 180 kg/cm2 obtained by sandblasting with alumina after thermal cycling 28&I times. The favorable result is attributed to sandblasting with alumina by roughening the surface of alloys and mech&cally removing the debris on the surface of the alloys to improve the wetting by the adhesive. However, the adhesion of Ni-Cr alloys is low if the alloys were only sandblasted (Fig. 2). A film created by oxidation is necessary. Conversely, two specimens of Co-Cr alloys sandblasted followed by ultrasonic wave washing yielded impressive adherence dur&ility (Fig. 3). The reason is that an oxide film is created an&gwn by oxygen dissolved in water during the process of ultrasonic wave washing to produce an apptip&te thickness for adhesion. Co-Cr all+ cant concentration of chromium, which for oxidation in lower ably, this oxide film possesses the capability of selfAPRIL
1986
VOLUME
55
NUMBER
4
NONPRECIOUS
ALLOYS
IN ADHESION-FIXED
300
-
Gl c
Qy.-. -.-._. o--,, -. -. .
c
PARTIAL
DENTURES
l
--a,,-
-.-._. -.
-.
_.__
---o--,-
-.
-
-.
Lit
_.-.
-.-.-.
‘@-.‘.-‘m
--__ *.
200
-@.“-‘-
-.-.
-.
l ---. n ---_ ---__
-
o-e-
iz
---_
-----____
----__
---_
‘O-,,- q ----
z mo
100
0’
-
I
’ 0
I
500
1000
I
1
1500
2000
cycles Thermal
Cycles
Fig. 2. Effect of thermal cycling on adhesion between resin and nickel-chromium alloys. (El, Rexillium air brushed with alumina; C .Rexillium air brushed with alumina and oxidized; o, SB-Bondloy air brushed with alumina; 0, SEBondloy air brushed with alumina and oxidation; @, SB-Bondloy air brushed with alumina and oxidized electrolytically.)
Thermal
Cycles
cycles
Fig. 3. Effect of thermal cycling on adhesion between resin and cobalt-chromium alloys. Q Biocast air brushed with alumina; I, Biocast air brushed with alumina and oxidized; o, Durallium JD air brushed with alumina; 0, Durallium JD air brushed with alumina and oxidized.)
repairing so the injured oxide film (during durability test) is repaired automatically by dissolved oxygen in 4” C and 60” C water.
PRCKEDVRE FOR CLINICAL
APPLICATION
The most suitable alloy-treatment method combination in this study was Biocast sandblasted with alumina followed by ultrasonic wave washing. THE JOURNAL
OF PROSTHETIC
DENTISTRY
Technique An intact second premolar and molar are appropriate abutments for a fixed partial denture. The right maxillary first molar is missing (Fig. 6). An impression was made of the prepared teeth and a working model was fabricated (Fig. 7). Reduction of the tooth surfaces was limited to the enamel at the proximal and palatal surfaces. A deeper 459
TANAKA
ET AL
kg/cm2 300
'
200
'
100
'
c Fn s L 6 u 5 al
5000
Thermal
Cycles
Fig. 4. Effect of increased number of thermal. cycles on nick&chromium (S%@ndloy) and cobalt-chromium alloy (Biocast) specimens. f o, SB&or~Iloy air brtlshed and @&%zed electrolytically; *, Biocast air brushed.)
Fig. 5. Alloy surfaces of Biocast and SB-Bondloy specimen after debond test. (A, Biocast; B, SBBondloy.)
Fig. 6. Preoperative
Fig. 7. Enamel cast.
preparation
for retainers
on working
view of loss of first molar.
APRIL
1986
VOtUME
55
NUMBER
4
NONPRECIOUS
ALLOYS
IN ADHESION-FIXED
PARTIAL
DENTURES
Fig. 9. Retainer veneered with porcelain.
Fig. 10. Air-brushing at 5 atm.
treatment
with high air pressure
rest was prepared to serve as an insertion guide and reduce the excessive occlusal stresses. A metal framework for an adhesion-fixed partial
denture cast with Biocast is shown in Fig. 8. The alloy was cast with a high-frequency dissolution casting machine (Argoncaster; Shofu Mfg. Co., Kyoto,
Japan). The completed fixed partial denture framework with a porcelain-fused-to-metal pontic is shown in Fig. 9. After the trial fit of the metal casting, a sandblast treatment is provided to the interior surface of the metal wing (Fig. IO). Sandblasting with alumina with a particle size of 50 pm, under 5 atmospheric pressure, is essential for adhesion. It is recommended that the veneered porcelain or resin be prewrapped by a soft plastic film (Laboratory film; American Can Co., Greenwich, Conn.) to preclude damages. The adhesion-fixed partial denture was cleaned in a neutral detergent for 10 minutes and by an ultrasonic wave in distilled water for 1 minute and dried with clean compressed air (Eigs. 11 and 12). The interior surface of the treated metal wing must be handled with care to avoid contamination.
THE JOURNAL
OF PROSTHETIC
Fig. 11. After air brushing, restoration is ultrasonically cleaned in a neutral detergent solution to create an oxidation film inside of metal lingual wings.
DENTISTRY
Fig. 12. Finished treatment
of retainer
for adhesion.
Adhesion was accomplished with Orthomite SuperBond after the abutment tooth was acid etched according to acceptable methods. A completed adhesion-fixed partial denture with a porcelain-fused-to-metal pontic 1 year after surgery is shown in Fig. 13. There have been 230 adhesion-fixed partial dentures prepared by this method from 1 month to 3 years with six restorations failing. However, additional adhesionfixed partial dentures have been placed to continue the longitudinal study. This treatment method is also effective for the combination of 4-META (Metadent, Sun Medical Co.) denture resin and Co-Cr denture bases. Superior results can be realized when the surface treatment is applied before relining of a metal base and the portion of a clasp embodied in the denture resin. CONCLUSION In this study a suitable method with durable bonding and ease of manipulation was suggested for treating the 461
TANAKA ETAI.
SES 1. 2.
3.
of a splint to enamel of lower anterior R&ette AL: At&went tee&J !%.¶TRET DWT %k418,1973. Howe DF, Denehy GE: Anterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J PRCSTEFET DENT 37:28, 1977. Livaditis GJ, Thompson VP: Etched castings, i\n improved retentive mechanism for resin-bonded retainers. J PROSTHET
D~~~47:52,1982. 4.
5.
Fig. 13. Completed adhesive restoration 1 year surgery.
after
interior surface of the adhesion-fixed partial denture coaticted with Ni-Cr and Co-G alloys. The following conclusions were drawn. 1. Two Ni-Cr alloys for metal/ceramic crowns developed suIz&rior bo&ng strength and adhesive durability after sandblasting with alumina and oxidation. The oxidizing agent used in this study was 1% weight of potassium maqanate in 3% sulfuric acid. 2. Suf%ient bonding strength and adhesion were obtained for the Co-Cr metal/ceramic crowns and metal base dentures by merely sandblasting and ultrasonic wave washing. The oxidizing treatment was extraneous (i.e., Co-& metal ceramic crowns demonstrated a bonding strength of 220 kg/cm2 after thermal cycling 10,000 times).
Rkhard M. Lakw, U.S. Air Force Medical
Keesler,
Biloxi,
Miss.,
lic~mn / rcqueslr lo; DR. TAKUO TANAKA NAGASAKI UNIVERSITY SCHOOL OF DENTISTRY 7-1, SAKAMOTO-CHO NAGASAKI, JAPAN
A
The opinions expressed herein are those of the reflect the views of the U.S. Air Force or Defense. *Chairman, Department of Periodontics, U.S. Center Keesler. **Chief, Clinical Dentistry, Dental Investigative Force Base.
DA&D., M&+*
and Brooks Air Force Base, San Antonio,
relatively new air abrasive prophylaxis device has been in use for the past several years. The Prophy-Jet
462
107x.
‘I’akeyama M, Kashibuchi S, Nakabayashi N. hiasuhara E. Studies on dental self-curing resin (17), adhesion of PMM:2 with bovine enamel or dental aiioys. J Jpn SW Dent Appar Mater 19:179, 1978. 7. Tanaka T, Takeyama M, Atsuta M, Nakabayashi N. Masuhara E: 4-META opaque resin-A new resin strongly adhesive to nickel-chromium alloy. J Dent Res 60:3697. 1981. 8. Tanaka T, Nagata K, Takeyama M, Nakabayashi N, Masuhara E: Heat treatment of gold alloy to get adhesion with resin. J Jpn Sot Dent Appar Mater 21:96, 1980. 9. Yamashita A, Yamami S, Ishii M, Yamaguchi ‘I’. Uramoto T: Procedure for applying adhesive resin (MMA-TBB) to crown and hridge restorations. J Jpn Prostbodont Sor 26~1118, 1982. 10. Greene ND: Metallic Corrosion. Kent. 1961. Butterworth 8i Co (Publishers) Ltd, p 113. 6.
DA&D., MS.,* and Robert L. Cwhy, Center
Thompson VP, Castillo ED, Livaditis GJ: Resin-bonded retainers. Part 1: Resin bond to electrolytically etched nonprecious alloys. J PROSTHET DENT 50~771,1983. Nakabayashi N, Masuhara E, Mochida E: Development 01 adhesive pit and fissure sealants using a MM.4 resin initiated by a tri-N-butyl borane derivative. J Biomed Mater Res 12:149,
authors and do not the Department of Air Force Medical Service, Brooks Air
Tex
(Dents& International Inc., York, Pa.) pro&ccs a powerful spray of air, powder of sodium b&a highly &e&e in the M& ofstudies have evaluated the tissues. Willmann et al.’ instrument on enamel su pared with other proph$axis infzoncl~ive. Weaks et al.* romped the.&&vL of the Prophy-Jet device to prophylaxis paste in removing APRIL
1986
VOLUME55
NUMBER4
5. 6. I. 8. 9.
10.
REFERENCES 1. Sred 1R, McLean JW: The strength of metal-ceramic bonds with base metals containing chromium. Br Dent J 132~232, 1972. 2. Williams TRP, Johnson CE, Winchell PG. Phillips RW: Be, Li, and Na distribution near a porrelain/Ni alloy interface shown by ion microprobe mass analysis. J Dent Res 57~233, 1978. 3. Williams TRP, Winchell PG, Phillips RW: Dental porcelain/ Ni alloy interface reactions and their efl’ective prevemion. J Dent Kes 57:583, 1978. 4. ltnusavice KJ. Ringle RD, Fairhurst CW: Adherence comrol-
Il.
ling elements in ceramic-metal systems. II. N
Kcprlril ,-l’c/?rc\/\ /iI: DR. N. K. SARKAR
LOUISIANA STATE UNIVERSITY SCHOOLof DENTISTRY NEW ORLEANS,LA 70119-2799
Takuo Tanaka, D.R.S., Ph.D.,* Erilca F~jiyama, D.DS.,** Mm&i Akio Takaki, D.D.S., Ph.D.,*** and M$&tru AM&a, D.D,S., P&D.****
p D*Des.,**
University of Nagasaki, School of Dentistry, Nagasaki, Japan
A
new prosthetic restoration attracting mapy dentists is the adhesion-fixed partial denture. The adhesionfixed partial denture requires minimal tooth preparation and is easier to construct and manipulate than are conventional fixed partial dentures. To attach an adhesion-fixed partial denture to abutment teeth, resin material must be bonded to the tooth and metal framework. The tooth surfaces require etching with acid while the wing portions of fixed partial dentures are perforated with small tapered h01es’~~or the inside of the metal is electroiytically etched3,4to ensure mechanical bonding with the resin. Research of adhesive resins for bonding has been *i\ssociate Professor, Department of Fixed Prasthodontics. **Research Associate, Department of Fixed Prosthodontics. *** Leclurer, Department of Fixed Prosthodontics. ****Professor and Chairman, Department of Fixed Prosthodonlics 456
intense. A new adhesive resin, MM/EMMA, with 5% weight 4-m&acryloxyetbyl trim&tate anhydride (4META), initiated by a tri-N-butyl &raz~e~,’ has been intraduced. this adhesive resin acihe~~ to tooth enamel as well as to the oxidized sua&oes of t&z& aUoys.7’” Two methods of treatmat, an&c o&Wion9 and nitfic acid dipping,’ were developed for n~q~txSous dloys. However, the adhesion from these me@+% was hot water resistant and res&s$ in c&icaf f&&we.
manganate. A bonding
APRIL
1986
VOLUME
55
NUMBER
4
NONPRECIOUS
ALLOYS
Table I. Alloys
IN ADHESION-FIXED
PARTIAL
DENTURES
used in this experiment
Commercial name of alloy Ni-Cr system Rexillium SB-Bondloy Co-Cr system Biocast Durallium JD
Component Manufacturer Jeneric Gold (USA) Towa Giken (Japan) Jeneric Gold Jelenko (USA)
Ni
Cr
co
Others
86.0 56.4
8.5 17.4
-
5.5 26.2
-
32.0 26.0
62.0 68.0
6.0 6.0
surface treatment of base metal alloys and presents examples of clinical application for the adhesion-fixed partial denture.
MATERIAL AND METHODS Fabrication of metal frames Four nonprecious alloys were used for this study, and the components are reported in Table I. The alloys were cast as flat plate metal frames, IO by IO by 2 mm, according to the manufacturer’s instructions. The surface of the cast metal frames was air brushed with alumina powder having a mean diameter of 50 pm and washed in neutral detergent solution for IO minutes and then in distilled water for I minute with ultrasonic wave. The water remaining on the metal plates was dried by clean compressed air. Half of the metal frames were tested immediately for adhesion while the remaining half was also treated with an oxidizing agent before adhesion.
Immersion in an oxidizing
solution
The oxidizing solution was composed of 3% weight aqueous sulfuric acid with 1% weight potassium permanganate. The metal frames were immersed in the oxidizing solution at room temperature for 2 minutes, washed in ultrasonic wave in distilled water for I minute, and dried for adhesion test.
Preparation of specimens for adhesion The treated surface of the metal specimen was fastened to an acrylic resin rod by the adhesive resin Orthomite Super-Bond (Sun Medical Co., Kyoto, Japan)‘, 6 and mounted to the testing machine. Fig. 1 displays the specimens for the bonding test and the circle of adhesive resin with a diameter of 5 mm. For SB-Bondloy, adhesion specimens made of the metal frames treated by the anodic oxidation device EZ-OXISOR9 (Towagiken Co., Kyoto, Japan) were used for comparison.
Measurement of tensile bonding strength Metal specimens were placed alternately in water at 4” + I” C and 60” + 2” C for 60 seconds and the thermal cycle was repeated 2000 times before testing. THE IOURNAL
OF PROSTHETIC
DENTISTRY
(wt-%) Indicated
restoration
Metal-ceramic Metal-ceramic
crown crown
Metal-ceramic crown Metal base denture
The amount of force required to separate the acrylic resin rod from the metal casting was measured at a cross-head speed of 2 mm/min with a universal testing machine (Autograph DCS-500; Shimazu Mfg. Co., Kyoto, Japan). Tests were performed on IO specimens for each test. Specimens prepared by Biocast and SBBondloy were also tested after thermal cycling 10,000 times.
RESULTS The effect of oxidation of Ni-Cr alloys with thermal cycling 2000 times is shown in Fig. 2. The adhesive durability after the thermal cycling was improved by oxidation after air brushing with alumina, and the bonding force of approximately 250 kg/cm* was maintained after thermal cycling 2000 times. The bonding strength before the thermal cycling without oxidation was 250 kg/cm2 but was reduced to less than 180 kg/cm2 after thermal cycling. A higher bonding strength and adhesive durability for Co-Cr alloys with or without oxidation is shown in Fig. 3. This differed from the Ni-Cr alloy specimens. Co-Cr alloys treated by oxidation demonstrated less adhesive durability than did untreated specimens. Bonding strength and SD of the alloys after thermal cycling 2000 times are listed in Table II. The test specimens treated by oxidation revealed the least SD. The excessive SD of SB-Bondloy with EZ-OXISOR suggested that the bonding strength of this system was unreliable. It was concluded that a stable and high bonding strength with a durable adhesion could be obtained by air brushing with alumina and supersonic wave washing for Co-Cr alloys. Results of the adhesion test under severe conditions by increasing the number of thermal cycles is shown in Fig. 4. Biocast subjected to sandblasting and supersonic wave washing produced a remarkably durable adhesion of 220 kg/cm2 after thermal cycling 10,000 times. Conversely, the bonding strength of SB-Bondloy treated by EZOXISOR was recorded at only 140 kg/cm2. Fractured surfaces of the specimens caused by the tension test after thermal cycling 10,000 times are shown in Fig. 5. Biocast specimens recorded cohesive fracture at 457
TANAKA
ET AL
TaMa IL The tensile bond stren@h (&g/cm2) dter 2df60 +hennal cycles to rtickel-chromium and c&&-chromium alloys Commercial name of alloy
Method Air brushed
Ni-Cr system Rexillium SB-Bondloy SB-Bondloy Co-Cr system Biocast Durailium JD *Oxidized
Fig. 1. Specimen for adhesion test. (A, acrylic rod for a handle; B, alloy for test; C, adhesive resin.)
the resin-metal interface whereas abundant diffusion of water from the marginal region was noted with SBBondloy.
DISCUSSiON The resin including 4-META adheres strongly to nonprecious metals (i.e., Ni-Cr alloys). The thin oxide film produced on the surface of alloys adheres with 4-META strongly. For this reason, many attempts have been made to create a suitable oxide film artificially on the surface of nonprecious alloys, particularly Ni-Cr alloys. 7,9These methods were not applicable in clinical practice because they required prolonged treatment with concentrated nitric acid. Anodic oxidation advocated by Yamashita et al.9 had a practical treatment time without volatile acids and was widely used for the adhesion-fixed partial denture. However, an effective surface treatment method for a stable oxide film has been sought because anodic oxidation provided unreliable bonding. The surface treatment suggested in this study improved the bonding strength and handling properties, with safer manipulation. This new method uses an oxidation agent of potassium manganate and dilute sulfuric acid. The oxidation agent uses potassium manganate, which precipitates an oxidation effect in an acid solution and also controls the strength of oxidation by varying the pH. The density of the sulfuric acid was 0.3% weight and 1% for potassium manganate designed 458
electrolytically
of surface
treatment -Air brushed and oxidized .._ ,_
148 * 26 186 + 41 -
243 255 292
k 13 + 30 ?x67%
+ +
241 238
+ 10 -+ 31
270 245
with
33 28
EZ-OXISOR.
to treat the alloys within 2 r@nutes. Treatment may be shortened with 0.5% weight den&y sulfuric acid and increasing the concentration of the potassium manganate. If the solution of oxidation agent is left for more than 1 day, the potassium manganate is reduced to manganese dioxide resulting in a weak oxidation solution. Therefore the solution should be used within a few hours after preparation. If Ni-Cr alloys are treated with the oxidation agent, adhesion is improved substantiaIly. However, if the treatment is prolonged, the adhesion decreases dramatically. For instance, the treatment time of 10 minutes reduced the bonding strength of SB-I@~dIoy to Zt;D + 12 kg/cm2 after thermal cycling 2000 times. It is hypothesized that the extension of treatment time increases the thickness of the oxide film and a more stable structure develops, lowering the reactivity with the adhesive. Treatment of an adhesive surface by sandbIa&ng with alumina is also a critical procedure. Polishing SB-Bondloy with a Carborundum point followed by oxidation yielded the bonding strength of only 107 + 16 kg/cm2 after thermal cycling 300 times. This value is lower than 180 kg/cm2 obtained by sandblasting with alumina after thermal cycling 28&I times. The favorable result is attributed to sandblasting with alumina by roughening the surface of alloys and mech&cally removing the debris on the surface of the alloys to improve the wetting by the adhesive. However, the adhesion of Ni-Cr alloys is low if the alloys were only sandblasted (Fig. 2). A film created by oxidation is necessary. Conversely, two specimens of Co-Cr alloys sandblasted followed by ultrasonic wave washing yielded impressive adherence dur&ility (Fig. 3). The reason is that an oxide film is created an&gwn by oxygen dissolved in water during the process of ultrasonic wave washing to produce an apptip&te thickness for adhesion. Co-Cr all+ cant concentration of chromium, which for oxidation in lower ably, this oxide film possesses the capability of selfAPRIL
1986
VOLUME
55
NUMBER
4
NONPRECIOUS
ALLOYS
IN ADHESION-FIXED
300
-
Gl c
Qy.-. -.-._. o--,, -. -. .
c
PARTIAL
DENTURES
l
--a,,-
-.-._. -.
-.
_.__
---o--,-
-.
-
-.
Lit
_.-.
-.-.-.
‘@-.‘.-‘m
--__ *.
200
-@.“-‘-
-.-.
-.
l ---. n ---_ ---__
-
o-e-
iz
---_
-----____
----__
---_
‘O-,,- q ----
z mo
100
0’
-
I
’ 0
I
500
1000
I
1
1500
2000
cycles Thermal
Cycles
Fig. 2. Effect of thermal cycling on adhesion between resin and nickel-chromium alloys. (El, Rexillium air brushed with alumina; C .Rexillium air brushed with alumina and oxidized; o, SB-Bondloy air brushed with alumina; 0, SEBondloy air brushed with alumina and oxidation; @, SB-Bondloy air brushed with alumina and oxidized electrolytically.)
Thermal
Cycles
cycles
Fig. 3. Effect of thermal cycling on adhesion between resin and cobalt-chromium alloys. Q Biocast air brushed with alumina; I, Biocast air brushed with alumina and oxidized; o, Durallium JD air brushed with alumina; 0, Durallium JD air brushed with alumina and oxidized.)
repairing so the injured oxide film (during durability test) is repaired automatically by dissolved oxygen in 4” C and 60” C water.
PRCKEDVRE FOR CLINICAL
APPLICATION
The most suitable alloy-treatment method combination in this study was Biocast sandblasted with alumina followed by ultrasonic wave washing. THE JOURNAL
OF PROSTHETIC
DENTISTRY
Technique An intact second premolar and molar are appropriate abutments for a fixed partial denture. The right maxillary first molar is missing (Fig. 6). An impression was made of the prepared teeth and a working model was fabricated (Fig. 7). Reduction of the tooth surfaces was limited to the enamel at the proximal and palatal surfaces. A deeper 459
TANAKA
ET AL
kg/cm2 300
'
200
'
100
'
c Fn s L 6 u 5 al
5000
Thermal
Cycles
Fig. 4. Effect of increased number of thermal. cycles on nick&chromium (S%@ndloy) and cobalt-chromium alloy (Biocast) specimens. f o, SB&or~Iloy air brtlshed and @&%zed electrolytically; *, Biocast air brushed.)
Fig. 5. Alloy surfaces of Biocast and SB-Bondloy specimen after debond test. (A, Biocast; B, SBBondloy.)
Fig. 6. Preoperative
Fig. 7. Enamel cast.
preparation
for retainers
on working
view of loss of first molar.
APRIL
1986
VOtUME
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NONPRECIOUS
ALLOYS
IN ADHESION-FIXED
PARTIAL
DENTURES
Fig. 9. Retainer veneered with porcelain.
Fig. 10. Air-brushing at 5 atm.
treatment
with high air pressure
rest was prepared to serve as an insertion guide and reduce the excessive occlusal stresses. A metal framework for an adhesion-fixed partial
denture cast with Biocast is shown in Fig. 8. The alloy was cast with a high-frequency dissolution casting machine (Argoncaster; Shofu Mfg. Co., Kyoto,
Japan). The completed fixed partial denture framework with a porcelain-fused-to-metal pontic is shown in Fig. 9. After the trial fit of the metal casting, a sandblast treatment is provided to the interior surface of the metal wing (Fig. IO). Sandblasting with alumina with a particle size of 50 pm, under 5 atmospheric pressure, is essential for adhesion. It is recommended that the veneered porcelain or resin be prewrapped by a soft plastic film (Laboratory film; American Can Co., Greenwich, Conn.) to preclude damages. The adhesion-fixed partial denture was cleaned in a neutral detergent for 10 minutes and by an ultrasonic wave in distilled water for 1 minute and dried with clean compressed air (Eigs. 11 and 12). The interior surface of the treated metal wing must be handled with care to avoid contamination.
THE JOURNAL
OF PROSTHETIC
Fig. 11. After air brushing, restoration is ultrasonically cleaned in a neutral detergent solution to create an oxidation film inside of metal lingual wings.
DENTISTRY
Fig. 12. Finished treatment
of retainer
for adhesion.
Adhesion was accomplished with Orthomite SuperBond after the abutment tooth was acid etched according to acceptable methods. A completed adhesion-fixed partial denture with a porcelain-fused-to-metal pontic 1 year after surgery is shown in Fig. 13. There have been 230 adhesion-fixed partial dentures prepared by this method from 1 month to 3 years with six restorations failing. However, additional adhesionfixed partial dentures have been placed to continue the longitudinal study. This treatment method is also effective for the combination of 4-META (Metadent, Sun Medical Co.) denture resin and Co-Cr denture bases. Superior results can be realized when the surface treatment is applied before relining of a metal base and the portion of a clasp embodied in the denture resin. CONCLUSION In this study a suitable method with durable bonding and ease of manipulation was suggested for treating the 461
TANAKA ETAI.
SES 1. 2.
3.
of a splint to enamel of lower anterior R&ette AL: At&went tee&J !%.¶TRET DWT %k418,1973. Howe DF, Denehy GE: Anterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J PRCSTEFET DENT 37:28, 1977. Livaditis GJ, Thompson VP: Etched castings, i\n improved retentive mechanism for resin-bonded retainers. J PROSTHET
D~~~47:52,1982. 4.
5.
Fig. 13. Completed adhesive restoration 1 year surgery.
after
interior surface of the adhesion-fixed partial denture coaticted with Ni-Cr and Co-G alloys. The following conclusions were drawn. 1. Two Ni-Cr alloys for metal/ceramic crowns developed suIz&rior bo&ng strength and adhesive durability after sandblasting with alumina and oxidation. The oxidizing agent used in this study was 1% weight of potassium maqanate in 3% sulfuric acid. 2. Suf%ient bonding strength and adhesion were obtained for the Co-Cr metal/ceramic crowns and metal base dentures by merely sandblasting and ultrasonic wave washing. The oxidizing treatment was extraneous (i.e., Co-& metal ceramic crowns demonstrated a bonding strength of 220 kg/cm2 after thermal cycling 10,000 times).
Rkhard M. Lakw, U.S. Air Force Medical
Keesler,
Biloxi,
Miss.,
lic~mn / rcqueslr lo; DR. TAKUO TANAKA NAGASAKI UNIVERSITY SCHOOL OF DENTISTRY 7-1, SAKAMOTO-CHO NAGASAKI, JAPAN
A
The opinions expressed herein are those of the reflect the views of the U.S. Air Force or Defense. *Chairman, Department of Periodontics, U.S. Center Keesler. **Chief, Clinical Dentistry, Dental Investigative Force Base.
DA&D., M&+*
and Brooks Air Force Base, San Antonio,
relatively new air abrasive prophylaxis device has been in use for the past several years. The Prophy-Jet
462
107x.
‘I’akeyama M, Kashibuchi S, Nakabayashi N. hiasuhara E. Studies on dental self-curing resin (17), adhesion of PMM:2 with bovine enamel or dental aiioys. J Jpn SW Dent Appar Mater 19:179, 1978. 7. Tanaka T, Takeyama M, Atsuta M, Nakabayashi N. Masuhara E: 4-META opaque resin-A new resin strongly adhesive to nickel-chromium alloy. J Dent Res 60:3697. 1981. 8. Tanaka T, Nagata K, Takeyama M, Nakabayashi N, Masuhara E: Heat treatment of gold alloy to get adhesion with resin. J Jpn Sot Dent Appar Mater 21:96, 1980. 9. Yamashita A, Yamami S, Ishii M, Yamaguchi ‘I’. Uramoto T: Procedure for applying adhesive resin (MMA-TBB) to crown and hridge restorations. J Jpn Prostbodont Sor 26~1118, 1982. 10. Greene ND: Metallic Corrosion. Kent. 1961. Butterworth 8i Co (Publishers) Ltd, p 113. 6.
DA&D., MS.,* and Robert L. Cwhy, Center
Thompson VP, Castillo ED, Livaditis GJ: Resin-bonded retainers. Part 1: Resin bond to electrolytically etched nonprecious alloys. J PROSTHET DENT 50~771,1983. Nakabayashi N, Masuhara E, Mochida E: Development 01 adhesive pit and fissure sealants using a MM.4 resin initiated by a tri-N-butyl borane derivative. J Biomed Mater Res 12:149,
authors and do not the Department of Air Force Medical Service, Brooks Air
Tex
(Dents& International Inc., York, Pa.) pro&ccs a powerful spray of air, powder of sodium b&a highly &e&e in the M& ofstudies have evaluated the tissues. Willmann et al.’ instrument on enamel su pared with other proph$axis infzoncl~ive. Weaks et al.* romped the.&&vL of the Prophy-Jet device to prophylaxis paste in removing APRIL
1986
VOLUME55
NUMBER4