T h e e f f e c t s o f a l l o y s u r f a c e t r e a t m e n t s a n d r e s i n s on t h e retention of resin-bonded retainers M. H. E l - S h e r i f , B.D.S., M.Sc.D.,* A. E I - M e s s e r y , B.D.S., M.Sc.D., Ph.D.,** a n d M. N. H a l h o u l , B.D.S., M . S c . D . , Ph.D.***
University of Tanta, Faculty of Dentistry, Tanta, Egypt This study e v a l u a t e d the effects on retention of three metal surface textures and four resin luting materials by m e a s u r i n g the m a g n i t u d e of the force required for the r e m o v a l of resin-bonded fixed partial denture retainers. The results of the study indicate that a retainer air-abraded with 250 # aluminum oxide, used with any of the resins tested, should provide sufficient retention for single pontic posterior resin-bonded fixed partial dentures. (J PROSTHET DENT 1991;66:782-6.)
A
steady evolution in resin-bonded retainers has developed since Rochette's description of perforated "wing" retainers for periodontal splints in 1973.1 Although the perforated "wing" has been used since that time, 25 investigators have experimented with alternate methods designed to improve the retention of this restoration. An electrochemical etching technique used by Tanaka et al. 6 to produce pitting corrosion of metal for retaining acrylic resin facings on metal copings was adapted by Livaditis and Thompson 7 to etch the internal surfaces of base metal retainers for resin-bonded fixed partial dentures. Moon s and Hudgins et al. 9 produced particle-roughened retainers by incorporating salt crystals into the retainer patterns to produce roughness on their inner surfaces. Tanaka et al. 1° examined the use of air abrasion with 50 ~m aluminum oxide to provide a sufficient resin-to-metal bond when used with an oxidation treatment, and Wiltshire 11 used 250 tim aluminum oxide to treat the alloy surface. This study evaluated the force required for the removal of base metal alloy retainers whose internal surfaces had been treated by three different techniques. Because composite resins play such an important role in the retention of resin-bonded fixed partial dentures, four resin bonding materials were used in this study. MATERIAL
AND
METHODS
One hundred twenty caries-free human maxillary premolars were collected and stored in 10% formalin solution. Tooth preparation was accomplished with a high-speed turbine handpiece and assorted diamond points. The tooth preparation used in the study was described by Thompson et al. 12 Axial reduction ran from the mesiofacial line angle
*Formerly Special Fellow, Department of Fixed Prosthodontics, University of Oklahoma, College of Dentistry, Oklahoma City, Okla. Presently Lecturer, Department of Restorative Dentistry. **Assistant Professor, Department of Restorative Dentistry. ***Professor, Department of Restorative Dentistry. 10/1/27920
782
Fig. 1. Abutment preparation covering one proximal surface and extending around lingual cusp. Occlusal rest extends from proximal surface reduction.
on one proximal surface to the opposite side of the lingual cusp, with no grooves. An occlusal rest extended from the proximal reduction approximately to the middle of the tooth mesiodistally (Fig. 1). A wax pattern was made for each specimen with a U-shaped 10-gauge loop on each pattern. The wax loop served both as a sprue and later as an attachment for removal during testing (Fig. 2). All casting was done in an induction casting machine (Ticomatic, Ticonium Company, Albany, N.Y.) using a nickel-chromium alloy (Rexillium III, Jeneric Gold Co., Wallingford, Conn.). Castings for the 120 specimens were divided into three groups of 40 each. The internal surface treatment of the castings in the group to be electrochemically etched and the group to be air abraded with aluminum oxide was done after the retainers had been cast. Retainers with the particle roughened ("Virginia") finish were made from patterns into which the roughness had been incorporated. The metal castings to be electrochemically etched were
J U N E 1991
VOLUME 65
NUMBER 6
EFFECTS OF SURFACES AND RESINS
t F i g . 2. Nickel-chromium retainer with loop bonded to each prepared tooth.
T a b l e I. Means and s t a n d a r d deviations of removal forces, in kilograms of force, of 12 combinations of surface finishes and bonding materials (n = 10) ElectroBonding
material
Comspan Conclude Microfill pontic Panavia EX
Surface finish
chemical etching
26.9 (_+8.4) 11.8 ( _+4.2) 10.6 (_+_4.0) 17.8 (+4.5)
Particle-
A1203 air
roughened
abrasion
34.7 (_+6.9) 34.1 ( _+10.0) 31.7 (_+7.2) 43.7 (_+8.4) 7
51.1 (_+9.0) 39.8 ( _+7.3) 45.3 (_+9.5) 52.5 (_+11.3)
Standard deviations are shown in parentheses.
treated in a device made specifically for this purpose (Ult r a - E t c h Machine, Jeneric Gold Company). Each metal framework was mounted on an electrode (anode) and all surfaces not to be etched were masked with sticky wax. The metal framework was immersed in a 10 % sulfuric acid solution opposite a stainless steel electrode (cathode). A current density of 300 mA/cm 2:of surface to be etched was used for 3 minutes. The black debris layer present following etching of the castings was removed in an 18% solution of hydrochloric acid in an ultrasonic b a t h for 15 minutes. After etching, each retainer was immediately bonded to its tooth. The cast metal retainers were air abraded with fresh 250 tLm aluminum oxide (Dentablast, A T A Abrasive Products, Inc., Oklahoma City, Okla.) just prior to cementation. To use the particle-roughened ("Virginia") technique, an impression was made of each tooth preparation and a
THE JOURNAL OF PROSTHETIC DENTISTRY
F i g . 3. Testing a p p a r a t u s on an Instron universal testing machine with universal joints above and below casting to ensure direction of forces along long axis of tooth preparation.
master cast was poured in die stone. The outline of the framework was drawn on the die with a wax pencil. Sieved salt ranging in size from 149 to 250 um was sprinkled over the outlined area after the application of lubricant (Virginia Technique Kit, Richmond, Va.). Mold release spray was applied to secure the crystals. A 0.5 m m wide, crystalfree margin was left around the outlined surface. An acrylic resin p a t t e r n was made on the die. After removal from the cast, the surface of the pattern, which had contacted the stone, was abraded for 2 to 3 seconds with 50 tLm aluminum oxide. Then the p a t t e r n was rinsed in t a p water to dissolve the salt, leaving a rough surface pattern. The free margin was waxed with blue inlay wax to ensure a well-fitting pattern. Groups of 10 of each surface finish type were bonded to the tooth surface using four resin-bonding materials (Cornspan, L. D. Caulk Co., Milford, Del.; Conclude, 3M Co., St. Paul, M!inn.; Microfill pontic, Kulzer & Co., GmbH, Friedrichsdorf, Germany; and Panavia EX, K u r a r a y Co., Ltd., Osaka, Japan). Each specimen was seated and held with a 1 kgf load for 3.5 minutes after cementation. The specimens were k e p t in water at room t e m p e r a t u r e for 72 hours before testing. Twelve groups of 10 specimens each
783
EL-SHERIF, EL-MESSERY, AND HALHOUL
F i g . 4. Comparison of removal force of retainers prepared by three alloy t r e a t m e n t techniques and bonded by four resins.
50 ~
30 26.9
43.7 I
25 t(D 0 0 LL
"" 401 34.7
t-
34.1 31.7
.m
20
17.8
30~
I
15
11.8
0~ > 0 10
0
!
•-~
20 L
IJ_
10.6
E
:
> 0
E
r~
IX:
5 ~,
0
Comspan
Panavia
Conclude
10i 0 =
Microfill
Panavia
Comspan Conclude
Resins
Resins
F i g . 5. Comparison ofremoval force ofretainers prepared by electrochemical etching technique.
Table
Microfill
F i g . 6. Comparison of removal force of retainers produced by particle-roughened technique.
II. A n a l y s i s of v a r i a n c e : D e p e n d e n t v a r i a b l e - - k g f Source
DF
SS
MS
F value
PR > F
Model Error Corrected Total Source Group
11 108 119
22421.35 6727.89 29129.24
2038.30 62.30
32.72
0.0001 Root MSE 7.90
DF 11
ANOVA SS 22421.35
F value 32.72
PR > F 0.0001
R square
0.77
C.V.
23.78 Kgf mean 33.33
SS, Sum of squares; MS, mean squares; CV, coefficient of variation; MSE, mean standard error.
784
JUNE 1 9 9 1
VOLUME 65
NUMBER 6
EFFECTS
OF SURFACES
AND RESINS
60
60 r 52.5
D~ X~ .C_ v
51.1
50 ~
!
I --- 50-
45.3 39.8
40~
47.2
~d
I •-
40!
36.1
(D
o
o 0 30 ~ U_ i
O 30 ~ 1.1_ > 0
20 ~
> 0
E
E
¢v
10
I 20 ~
16.8
or10~
0¸
Panavia
Comspan
Microfill
Conclude 0 . . . . . . .
Resins
•
Air Abrasion
F i g . 7. Comparison ofremoval force ofretainers prepared by aluminum oxide air abrasion technique.
.
.
.
.
.
Particle Roughened
.
.
Electrochemical
Surface Treatment F i g . 8. C o m p a r i s o n o f r e m o v a l f o r c e o f r e t a i n e r s p r e p a r e d by three alloy t r e a t m e n t techniques.
T a b l e III. Duncan's multiple range test Group Mean
12 9 11 8 10 5 6 7 1 4 2 3 52 51 45 44 40 35 34 31 27 18 12 11
50 I ---
Any groups with common underscoring are not significantly different (p < 0.05).
40
38
37.6
t29.2
30
of surface t r e a t m e n t / b o n d i n g material combinations resulted. Before testing, each specimen was mounted in an acrylic resin base. The casting was fitted in an Instron Universal testing machine (model 1135, Instron Corp., Canton, Mass.) with universal joints to allow proper alignment. The U-shaped loop of the retainer was attached to the other m e m b e r of the Instron machine by a hook (Fig. 3). Tensile loading was applied at a crosshead speed of 1.3 m m per minute. The force required to separate the retainer from the tooth was recorded. RESULTS Twelve product/surface t r e a t m e n t s were compared. The means and s t a n d a r d deviations of the d a t a are given in Table L The analysis of variance (ANOVA) and a specific comparison test for the d a t a are shown in Table II. The F value for the ANOVA was 32.72 (df = 11,108; p = 0.0001). A Duncan's multiple range test (Table III, p = 0.05) showed t h a t aluminum oxide air abrasion was the superior surface finish for the products tested and electrochemical etching was the least effective with respect to bond force removal values.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
28.6
0 IJ_
"~ 2o0
E 12:10
0
.
Panavia
Comspan
.
.
.
.
.
Microfill
.
.
.
.
Conclude
Resins F i g . 9. Comparison of removal force of retainers bonded by four resins.
An overall comparison of the 12 groups is shown in Fig. 4. Comspan material was significantly more retentive t h a n Panavia EX, Conclude, and Microfill pontic materials with the electrochemical etching technique (Fig. 5). When the particle-roughened technique was used, Panavia E X material was superior to Comspan, Conclude, and Microfill pontic materials (Fig. 6). Panavia E X and Comspan mate-
785
EL-SHERIF, EL-MESSERY, AND HALHOUL
rials performed significantly better than Microfill pontic and Conclude materials when they were used with the aluminum oxide air abrasion technique (Fig. 7). The aluminum oxide air abrasion technique with 250 ~m particles was statistically superior to electrochemical etching and the particle-roughened technique (Fig. 8). Without regard to the surface finish, the bond strength values for Panavia EX and Comspan luting resins were significantly greater (using Duncan's multiple range test) than those for Conclude and Microfill pontic materials (Fig. 9). DISCUSSION The results agree with those of Pegoraro and Barrack, 13 who postulated that resin-bonded fixed partial denture retainers that have been air-abraded and cemented with Panavia EX material could successfully retain posterior fixed partial dentures. The 250 #m aluminum oxide particles used in the present study are the same size as those used by Wiltshire.11 The results of this study disagree with those of Dhillon et al. 14 and Ferrari et al., 15who found that electrochemical etching produced a stronger bond than air abrasion of the metal. Some suggested advantages of the aluminum oxide air abrasion technique are: (1) the lack of a need for special equipment; (2) the treated specimens possess adequate retention; (3) the procedure can be done clinically by the dentist or the dental assistant during the same appointment as the try-in; (4) if the cement fails, the fixed partial denture can be cleaned, reabraded, and recemented in one visit; and (5) the technique requires minimal time. SUMMARY
AND CONCLUSIONS
This study evaluated the effects of three metal surface finishes and four bonding materials on the retention of resin-bonded nickel-chromium alloy retainers. Retainer surfaces prepared by air abrading with 250 ~ aluminum oxide were superior in retention to those made by the particle-roughened and electrochemical etching techniques. Under the conditions of this study, air abrading with 250 #m aluminum oxide used with any of the resins tested should provide sufficient retention for posterior resinbonded fixed partial denture retainers.
786
REFERENCES 1. Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PROSTHETDENT 1973;30:418-23. 2. Howe DF, Denehy GE. Anterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J PROSTHET DENT 1977;37:28-31. 3. Denehy GE, Howe DF, Donald FH. A conservative approach to the missing anterior teeth. Quintessence Int 1979;7:23-9. 4. Livaditis GJ. Cast metal resin-bonded retainers for posterior teeth. J Am Dent Assoc 1980;110:926-9. 5. Denehy GE. Cast anterior bridges utilizing composite resin. Pediatr Dent 1982;4:44-7. 6. Tanaka T, Atsuta M, Uchiyama Y, Kawashima I. Pitting corrosion for retaining acrylic resin facings. J PROSTHETDENT 1979;42:282-91. 7. Livaditis GJ, Thompson V. Etched castings: an improved retentive mechanism for resin-bonded retainers. J PROSTHETDENT 1982;47:52-8. 8. Moon PC. The Virginia resin bonded bridge: a restorative material report. Va Dent J 1984;61:9-11. 9. Hudgins JL, Moon PC, Knap FJ. Particle-roughened resin-bonded retainers. J PROSTHETDENT 1985;53:471-6. 10. Tanaka T, Fujiyama E, Shimizu H, Takaki A, Atsuta M. Surface treatment of nonprecious alloys for adhesion-fixed partial dentures. J PROSTHET DENT 1986;55:456-62. 11. Wiltshire WA. Tensile bond strengths of various alloy surface treatments for resin-bonded bridges. Quintessence Dent Technol 1986;10:227-33. 12. Thompson V, Barrack G, Simonsen R. Posterior design principles in etched cast restorations. Quintessence Int 1983;14:311-8. 13. Pegoraro LF, Barrack G. A comparison of bond strength of adhesive cast restorations using different design, bonding agents, and luting resins. J PROSTHET DENT 1984;57:133-8. 14. Dhillon M, Fenton AH, Watson PA. Bond strengths of composite to perforated and etched metal surfaces [Abstract]. J Dent Res 1983;62:304. 15. Ferrari M, Cagidiaco MC, Breschi R. Evaluation of resin-bonded retainers with the scanning electron microscope. J PROSTHET DENT 1988;59:160-4. Reprint requests to: DR. M. H. EL-SHERIF FACULTYOF DENTISTRY UNIVERSITYOF TANTA TANTA EGYPT
Contributing authors H. T. S h i l l i n g b u r g , Jr., D.D.S., Professor and Chairman, Department of Fixed Prosthodontics, University of Oklahoma, College of Dentistry, Oklahoma City, Okla. M. G. Duncanson, Jr., D.D.S., Ph.D., Professor and Chairman, Department of Dental Materials, University of Oklahoma, College of Dentistry, Oklahoma City, Okla.
JUNE 1 9 9 1
VOLUME 65
NUMBER 6
University of Tanta, Faculty of Dentistry, Tanta, Egypt This study e v a l u a t e d the effects on retention of three metal surface textures and four resin luting materials by m e a s u r i n g the m a g n i t u d e of the force required for the r e m o v a l of resin-bonded fixed partial denture retainers. The results of the study indicate that a retainer air-abraded with 250 # aluminum oxide, used with any of the resins tested, should provide sufficient retention for single pontic posterior resin-bonded fixed partial dentures. (J PROSTHET DENT 1991;66:782-6.)
A
steady evolution in resin-bonded retainers has developed since Rochette's description of perforated "wing" retainers for periodontal splints in 1973.1 Although the perforated "wing" has been used since that time, 25 investigators have experimented with alternate methods designed to improve the retention of this restoration. An electrochemical etching technique used by Tanaka et al. 6 to produce pitting corrosion of metal for retaining acrylic resin facings on metal copings was adapted by Livaditis and Thompson 7 to etch the internal surfaces of base metal retainers for resin-bonded fixed partial dentures. Moon s and Hudgins et al. 9 produced particle-roughened retainers by incorporating salt crystals into the retainer patterns to produce roughness on their inner surfaces. Tanaka et al. 1° examined the use of air abrasion with 50 ~m aluminum oxide to provide a sufficient resin-to-metal bond when used with an oxidation treatment, and Wiltshire 11 used 250 tim aluminum oxide to treat the alloy surface. This study evaluated the force required for the removal of base metal alloy retainers whose internal surfaces had been treated by three different techniques. Because composite resins play such an important role in the retention of resin-bonded fixed partial dentures, four resin bonding materials were used in this study. MATERIAL
AND
METHODS
One hundred twenty caries-free human maxillary premolars were collected and stored in 10% formalin solution. Tooth preparation was accomplished with a high-speed turbine handpiece and assorted diamond points. The tooth preparation used in the study was described by Thompson et al. 12 Axial reduction ran from the mesiofacial line angle
*Formerly Special Fellow, Department of Fixed Prosthodontics, University of Oklahoma, College of Dentistry, Oklahoma City, Okla. Presently Lecturer, Department of Restorative Dentistry. **Assistant Professor, Department of Restorative Dentistry. ***Professor, Department of Restorative Dentistry. 10/1/27920
782
Fig. 1. Abutment preparation covering one proximal surface and extending around lingual cusp. Occlusal rest extends from proximal surface reduction.
on one proximal surface to the opposite side of the lingual cusp, with no grooves. An occlusal rest extended from the proximal reduction approximately to the middle of the tooth mesiodistally (Fig. 1). A wax pattern was made for each specimen with a U-shaped 10-gauge loop on each pattern. The wax loop served both as a sprue and later as an attachment for removal during testing (Fig. 2). All casting was done in an induction casting machine (Ticomatic, Ticonium Company, Albany, N.Y.) using a nickel-chromium alloy (Rexillium III, Jeneric Gold Co., Wallingford, Conn.). Castings for the 120 specimens were divided into three groups of 40 each. The internal surface treatment of the castings in the group to be electrochemically etched and the group to be air abraded with aluminum oxide was done after the retainers had been cast. Retainers with the particle roughened ("Virginia") finish were made from patterns into which the roughness had been incorporated. The metal castings to be electrochemically etched were
J U N E 1991
VOLUME 65
NUMBER 6
EFFECTS OF SURFACES AND RESINS
t F i g . 2. Nickel-chromium retainer with loop bonded to each prepared tooth.
T a b l e I. Means and s t a n d a r d deviations of removal forces, in kilograms of force, of 12 combinations of surface finishes and bonding materials (n = 10) ElectroBonding
material
Comspan Conclude Microfill pontic Panavia EX
Surface finish
chemical etching
26.9 (_+8.4) 11.8 ( _+4.2) 10.6 (_+_4.0) 17.8 (+4.5)
Particle-
A1203 air
roughened
abrasion
34.7 (_+6.9) 34.1 ( _+10.0) 31.7 (_+7.2) 43.7 (_+8.4) 7
51.1 (_+9.0) 39.8 ( _+7.3) 45.3 (_+9.5) 52.5 (_+11.3)
Standard deviations are shown in parentheses.
treated in a device made specifically for this purpose (Ult r a - E t c h Machine, Jeneric Gold Company). Each metal framework was mounted on an electrode (anode) and all surfaces not to be etched were masked with sticky wax. The metal framework was immersed in a 10 % sulfuric acid solution opposite a stainless steel electrode (cathode). A current density of 300 mA/cm 2:of surface to be etched was used for 3 minutes. The black debris layer present following etching of the castings was removed in an 18% solution of hydrochloric acid in an ultrasonic b a t h for 15 minutes. After etching, each retainer was immediately bonded to its tooth. The cast metal retainers were air abraded with fresh 250 tLm aluminum oxide (Dentablast, A T A Abrasive Products, Inc., Oklahoma City, Okla.) just prior to cementation. To use the particle-roughened ("Virginia") technique, an impression was made of each tooth preparation and a
THE JOURNAL OF PROSTHETIC DENTISTRY
F i g . 3. Testing a p p a r a t u s on an Instron universal testing machine with universal joints above and below casting to ensure direction of forces along long axis of tooth preparation.
master cast was poured in die stone. The outline of the framework was drawn on the die with a wax pencil. Sieved salt ranging in size from 149 to 250 um was sprinkled over the outlined area after the application of lubricant (Virginia Technique Kit, Richmond, Va.). Mold release spray was applied to secure the crystals. A 0.5 m m wide, crystalfree margin was left around the outlined surface. An acrylic resin p a t t e r n was made on the die. After removal from the cast, the surface of the pattern, which had contacted the stone, was abraded for 2 to 3 seconds with 50 tLm aluminum oxide. Then the p a t t e r n was rinsed in t a p water to dissolve the salt, leaving a rough surface pattern. The free margin was waxed with blue inlay wax to ensure a well-fitting pattern. Groups of 10 of each surface finish type were bonded to the tooth surface using four resin-bonding materials (Cornspan, L. D. Caulk Co., Milford, Del.; Conclude, 3M Co., St. Paul, M!inn.; Microfill pontic, Kulzer & Co., GmbH, Friedrichsdorf, Germany; and Panavia EX, K u r a r a y Co., Ltd., Osaka, Japan). Each specimen was seated and held with a 1 kgf load for 3.5 minutes after cementation. The specimens were k e p t in water at room t e m p e r a t u r e for 72 hours before testing. Twelve groups of 10 specimens each
783
EL-SHERIF, EL-MESSERY, AND HALHOUL
F i g . 4. Comparison of removal force of retainers prepared by three alloy t r e a t m e n t techniques and bonded by four resins.
50 ~
30 26.9
43.7 I
25 t(D 0 0 LL
"" 401 34.7
t-
34.1 31.7
.m
20
17.8
30~
I
15
11.8
0~ > 0 10
0
!
•-~
20 L
IJ_
10.6
E
:
> 0
E
r~
IX:
5 ~,
0
Comspan
Panavia
Conclude
10i 0 =
Microfill
Panavia
Comspan Conclude
Resins
Resins
F i g . 5. Comparison ofremoval force ofretainers prepared by electrochemical etching technique.
Table
Microfill
F i g . 6. Comparison of removal force of retainers produced by particle-roughened technique.
II. A n a l y s i s of v a r i a n c e : D e p e n d e n t v a r i a b l e - - k g f Source
DF
SS
MS
F value
PR > F
Model Error Corrected Total Source Group
11 108 119
22421.35 6727.89 29129.24
2038.30 62.30
32.72
0.0001 Root MSE 7.90
DF 11
ANOVA SS 22421.35
F value 32.72
PR > F 0.0001
R square
0.77
C.V.
23.78 Kgf mean 33.33
SS, Sum of squares; MS, mean squares; CV, coefficient of variation; MSE, mean standard error.
784
JUNE 1 9 9 1
VOLUME 65
NUMBER 6
EFFECTS
OF SURFACES
AND RESINS
60
60 r 52.5
D~ X~ .C_ v
51.1
50 ~
!
I --- 50-
45.3 39.8
40~
47.2
~d
I •-
40!
36.1
(D
o
o 0 30 ~ U_ i
O 30 ~ 1.1_ > 0
20 ~
> 0
E
E
¢v
10
I 20 ~
16.8
or10~
0¸
Panavia
Comspan
Microfill
Conclude 0 . . . . . . .
Resins
•
Air Abrasion
F i g . 7. Comparison ofremoval force ofretainers prepared by aluminum oxide air abrasion technique.
.
.
.
.
.
Particle Roughened
.
.
Electrochemical
Surface Treatment F i g . 8. C o m p a r i s o n o f r e m o v a l f o r c e o f r e t a i n e r s p r e p a r e d by three alloy t r e a t m e n t techniques.
T a b l e III. Duncan's multiple range test Group Mean
12 9 11 8 10 5 6 7 1 4 2 3 52 51 45 44 40 35 34 31 27 18 12 11
50 I ---
Any groups with common underscoring are not significantly different (p < 0.05).
40
38
37.6
t29.2
30
of surface t r e a t m e n t / b o n d i n g material combinations resulted. Before testing, each specimen was mounted in an acrylic resin base. The casting was fitted in an Instron Universal testing machine (model 1135, Instron Corp., Canton, Mass.) with universal joints to allow proper alignment. The U-shaped loop of the retainer was attached to the other m e m b e r of the Instron machine by a hook (Fig. 3). Tensile loading was applied at a crosshead speed of 1.3 m m per minute. The force required to separate the retainer from the tooth was recorded. RESULTS Twelve product/surface t r e a t m e n t s were compared. The means and s t a n d a r d deviations of the d a t a are given in Table L The analysis of variance (ANOVA) and a specific comparison test for the d a t a are shown in Table II. The F value for the ANOVA was 32.72 (df = 11,108; p = 0.0001). A Duncan's multiple range test (Table III, p = 0.05) showed t h a t aluminum oxide air abrasion was the superior surface finish for the products tested and electrochemical etching was the least effective with respect to bond force removal values.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
28.6
0 IJ_
"~ 2o0
E 12:10
0
.
Panavia
Comspan
.
.
.
.
.
Microfill
.
.
.
.
Conclude
Resins F i g . 9. Comparison of removal force of retainers bonded by four resins.
An overall comparison of the 12 groups is shown in Fig. 4. Comspan material was significantly more retentive t h a n Panavia EX, Conclude, and Microfill pontic materials with the electrochemical etching technique (Fig. 5). When the particle-roughened technique was used, Panavia E X material was superior to Comspan, Conclude, and Microfill pontic materials (Fig. 6). Panavia E X and Comspan mate-
785
EL-SHERIF, EL-MESSERY, AND HALHOUL
rials performed significantly better than Microfill pontic and Conclude materials when they were used with the aluminum oxide air abrasion technique (Fig. 7). The aluminum oxide air abrasion technique with 250 ~m particles was statistically superior to electrochemical etching and the particle-roughened technique (Fig. 8). Without regard to the surface finish, the bond strength values for Panavia EX and Comspan luting resins were significantly greater (using Duncan's multiple range test) than those for Conclude and Microfill pontic materials (Fig. 9). DISCUSSION The results agree with those of Pegoraro and Barrack, 13 who postulated that resin-bonded fixed partial denture retainers that have been air-abraded and cemented with Panavia EX material could successfully retain posterior fixed partial dentures. The 250 #m aluminum oxide particles used in the present study are the same size as those used by Wiltshire.11 The results of this study disagree with those of Dhillon et al. 14 and Ferrari et al., 15who found that electrochemical etching produced a stronger bond than air abrasion of the metal. Some suggested advantages of the aluminum oxide air abrasion technique are: (1) the lack of a need for special equipment; (2) the treated specimens possess adequate retention; (3) the procedure can be done clinically by the dentist or the dental assistant during the same appointment as the try-in; (4) if the cement fails, the fixed partial denture can be cleaned, reabraded, and recemented in one visit; and (5) the technique requires minimal time. SUMMARY
AND CONCLUSIONS
This study evaluated the effects of three metal surface finishes and four bonding materials on the retention of resin-bonded nickel-chromium alloy retainers. Retainer surfaces prepared by air abrading with 250 ~ aluminum oxide were superior in retention to those made by the particle-roughened and electrochemical etching techniques. Under the conditions of this study, air abrading with 250 #m aluminum oxide used with any of the resins tested should provide sufficient retention for posterior resinbonded fixed partial denture retainers.
786
REFERENCES 1. Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PROSTHETDENT 1973;30:418-23. 2. Howe DF, Denehy GE. Anterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J PROSTHET DENT 1977;37:28-31. 3. Denehy GE, Howe DF, Donald FH. A conservative approach to the missing anterior teeth. Quintessence Int 1979;7:23-9. 4. Livaditis GJ. Cast metal resin-bonded retainers for posterior teeth. J Am Dent Assoc 1980;110:926-9. 5. Denehy GE. Cast anterior bridges utilizing composite resin. Pediatr Dent 1982;4:44-7. 6. Tanaka T, Atsuta M, Uchiyama Y, Kawashima I. Pitting corrosion for retaining acrylic resin facings. J PROSTHETDENT 1979;42:282-91. 7. Livaditis GJ, Thompson V. Etched castings: an improved retentive mechanism for resin-bonded retainers. J PROSTHETDENT 1982;47:52-8. 8. Moon PC. The Virginia resin bonded bridge: a restorative material report. Va Dent J 1984;61:9-11. 9. Hudgins JL, Moon PC, Knap FJ. Particle-roughened resin-bonded retainers. J PROSTHETDENT 1985;53:471-6. 10. Tanaka T, Fujiyama E, Shimizu H, Takaki A, Atsuta M. Surface treatment of nonprecious alloys for adhesion-fixed partial dentures. J PROSTHET DENT 1986;55:456-62. 11. Wiltshire WA. Tensile bond strengths of various alloy surface treatments for resin-bonded bridges. Quintessence Dent Technol 1986;10:227-33. 12. Thompson V, Barrack G, Simonsen R. Posterior design principles in etched cast restorations. Quintessence Int 1983;14:311-8. 13. Pegoraro LF, Barrack G. A comparison of bond strength of adhesive cast restorations using different design, bonding agents, and luting resins. J PROSTHET DENT 1984;57:133-8. 14. Dhillon M, Fenton AH, Watson PA. Bond strengths of composite to perforated and etched metal surfaces [Abstract]. J Dent Res 1983;62:304. 15. Ferrari M, Cagidiaco MC, Breschi R. Evaluation of resin-bonded retainers with the scanning electron microscope. J PROSTHET DENT 1988;59:160-4. Reprint requests to: DR. M. H. EL-SHERIF FACULTYOF DENTISTRY UNIVERSITYOF TANTA TANTA EGYPT
Contributing authors H. T. S h i l l i n g b u r g , Jr., D.D.S., Professor and Chairman, Department of Fixed Prosthodontics, University of Oklahoma, College of Dentistry, Oklahoma City, Okla. M. G. Duncanson, Jr., D.D.S., Ph.D., Professor and Chairman, Department of Dental Materials, University of Oklahoma, College of Dentistry, Oklahoma City, Okla.
JUNE 1 9 9 1
VOLUME 65
NUMBER 6
