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The influence of contamination on the bond strength of an etched resin-bonded retainer
J!0)Â \ RESEARCH
REPORTS
This investigation examines the influence o f p otential sources o f contam ination on the resin bond strength o f a base metal alloy. Sixty specimens were cast in a base m etal alloy and etched. Composite resin cylinders were bonded to six groups o f ten specimens each and tested fo r shear bond strength using a testing machine a t a strain rate o f .5 mmlmin. Five o f the test groups received a different set o f treatm ents, and one o f the test groups was a control group. An analysis o f variance disclosed no significant differences in bond strengths among any o f the test groups at a level o f P < .05.
The influence of contamination on the bond strength of an etched resin-bonded retainer Tomas J. B allesteros, D M D Edward S. Duke, D D S , M SD Barry K. N orling, P hD Robert B. May hew, D M D , P hD
n 1955, B u o n o co re1 showed that an unfilled acrylic resin could be b o n d ed to enam el surfaces that have been treated with a phosphoric acid solution. T h e b o n d in g was m echanical an d was provided by th e resin m aterial flow ing into m icroporosities developed in th e enam el by the etchant. T h is technique has been investigated f u rth e r a n d is com p a tib le w ith th e im p ro v e d B IS-G M A resin-based system s as well.2"5 Factors such as in creased re te n tio n ,6,7 resistance to m icro leak ag e,8-9 a n d im p ro v e d clinical p erfo rm an ce10,11 have led to th e accep tance o f the acid-etching technique fo r use with com posite resin restorations. A uniq u e application o f th e acid-etching tech n iq u e was re p o rte d by R o c h ette.12 T h e technique involved the bond in g o f a p erfo ra ted perio d o n tal splint to etched enam el w ith an unfilled resin. F u rth e r m odifications o f this technique, including the attach m en t o f a p o n tic,13 the substitu tion o f a base m etal for gold alloys,14 and the use o f im proved resin cem en ts,15 gave rise to an alternative technique fo r replac ing m issing teeth.
I
T h is so-called M a ry la n d b rid g e , o r resin-bonded reta in er, has been rep o rted as useful in several clinical applications in c lu d in g tr e a tm e n t o f y o u n g p a tie n ts, in te rim fix ed p ro sth e s e s, p e rio d o n ta l splints, and m aintenance a fte r o rth o d o n tic trea tm e n t, as well as an econom ic alter native to conventional fixed partial d e n tu res.16' 18 A s u b s e q u e n t m o d if ic a tio n to th e resin-bonded reta in er was in tro d u ced by M cLaughlin.19 R ath er th an use the p erfo rations fo r attach m en t o f th e resin to the fram ew ork, M cLaughlin in tro d u ced the process o f electrolytically etching the base m etal as a m echanism for resin attach m ent. T h e electro-etching technique o f fers an im p ro v em en t over the use o f p e r fo ra tio n s in th a t th e b o n d stre n g th is g re a te r,20 less clinical w ear o f com posite resin occurs,21 an d a g rea ter resistance to m icroleakage exists.22 A long w ith th e a fo re m e n tio n e d im provem ents in th e resin-bonded reta in er tech n iq u e, a d isad v an tag e also has d e veloped. W hereas the p erfo ratio n s could be drilled initially by the laboratory, o r at
chairside by the d entist, it has been rec o m m e n d e d th a t th e electro -etch in g be p erfo rm ed afte r th e try-in ap p o in tm e n t.23 T h is reco m m en d atio n was m ad e to avoid co n tam ination o f th e etched m etal th a t could resu lt from saliva in tro d u ced d u rin g th e try-in, o r from su b seq u en t p ro ce d u re s such as ad ditional porcelain firings. All o f these facto rs may je o p a rd iz e successful b o n d in g o f th e com posite resin .21,23 I f the d ental clinic does not have th e necessary eq u ip m en t to p erfo rm th e electro-etching, th e appliance should be re tu rn e d to the laboratory a n d an ad ditional ap p o in tm e n t should be m ad e fo r final cem entation. Som e suggestions have been re p o rte d as useful fo r p rev en tin g contam ination o f th e etch ed m etal surface. T h ey included: adju stin g th e prosthesis w ithout fully seat ing it, using th e ru b b e r dam , an d w ashing the appliance with soap an d rinsing it with aceto n e.23,24 C u rren tly , n o n e o f th e su g gestions has been substantiated. T h is in v e stig a tio n ex a m in e s th e in flu e n c e o f saliva an d p o rcelain firings on th e bond stren g th o f com posite resin to an etched base m etal alloy. I n ad dition, techniques o f JADA, Vol. 112, March 1986 ■ 359
RESEARCH
REPORTS
w ashing an d of applying a protectan t o f unfilled resin o r v arnish are investigated.
Methods and materials Specimen preparation Sixty specim ens, 10 x 10 x 1 m m , w ere cast in a base m etal alloy (R exillium III) as directed by th e m a n u fa c tu re r. T o sim ulate th e initial a ppli cation o f p orcelain, th e 60 tabs o f m etal w ere fired in a porcelain oven (U ltra Mat) in the follow ing m an n e r: oxidation cycle, 990 F, with vacuum , 3 m inutes; o paque bake, 990 F, with vacuum , 1.5 m inutes; first bake, 960 F, with vacuum , 1.5 m inutes; second bake, 960 F, with vacuum , 1.5 m inutes; a n d glaze bake, 920 F, no vacuum , .5 m inute. E lectrolytic e tc h in g o f th e specim ens was d o n e using an e tc h in g m achine (Fig 1).
Electrolytic etching technique Attach the electrode to one side of the specim en using an orthodontic spot welder; verify the electrical continuity. Mask the electrode side and the edges of the specim en with fingernail varnish. Clean the surface to be etched with 25-/xm alum inum oxide air abrasive. Etch the specim en in a 10% solution of H 2SO 4 acid for 3 m inutes at a current density o f 300 mA applying constant ultrasonic agitation. Clean the etched specim en in an 18% solution o f HC1 acid for 10 m inutes with ultrasonic agitation. Verify characteristic dendritic etch with a stereo m icroscope at a magnification X 50. Remove the m asking varnish in two changes of acetone in an ultrasonic cleaner. Fig 1 ■ Electrolytic etching o f the specim ens was done using an etching m achine with the technique described.
GROUP D. T h is g ro u p o f e tch ed specim ens first was co n tam in ated with the n a tu ra l saliva for 10 m inutes, th e n a cleaning tre a tm e n t was p e r fo rm ed using a soap solution (Hebiclens) o f 1 p a rt soap 5 p a rts w ater, fo r 10 m inutes in an ultrasonic clean er follow ed by acetone fo r 10 m inutes in an ultrasonic cleaner. T h e com posite resin th en was b o n d e d as before.
to th e e tch ed m etal tabs was d e te rm in e d u sin g a testing m achine (In stro n Universal) a t a cross head speed o f .50 m m /m in. T h e u p p e r shearing blade was placed flush with the m etal tab s u r face to e n su re load in g p e rp en d icu la r to the com posite resin cylinders. T h e m etal tabs w ere stabilized using a vise fixture.
Results
co n tro l g ro u p . A 6 m m in diam eter, 4 m m in height T eflo n tube was used to bond the com posite resin to the e tch ed m etal tabs. T h e u n filled resin (B onding A gent), follow ed by the com posite resin (A daptic), was in serted in to the tube. T h is resulted in a com posite resin cylin d e r, 4.85 m m in diam eter, b o n d ed p e rp en d icu larly to the e tch ed m etal surface.
GROUP E. T h is g ro u p o f e tch ed specim ens re ceived the first p ro tec ta n t, in th e form o f the unfilled resin, b ru sh ed on th e surface. T o m ain tain a clinically acceptable thickness o f unfilled resin (to allow seating o f the appliance in the m outh), the m etal tabs w ere pressed against a slab o f dental stone until the resin h a d set. T his p ro c e d u re sim u la ted the p o sitio n in g o f th e resin-bonded re ta in e r on the w orking m odel. T h e resin-coated tabs th en w ere contam inated with saliva, cleaned with acetone, a n d b o nded with com posite resin.
GROUP B . This g ro u p o f e tch ed specim ens was
GROUP F . T h is g ro u p o f etched specim ens was
Test groups A fter e tching, the base m etal tabs w ere divided into six test g ro u p s o f ten specim ens each. T h e test g ro u p s received th e follow ing treatm ents: GROUP A. T h is g ro u p of e tc h ed specim ens was the
co n tam in ated with n a tu ra l saliva by su b m e rg ing the specim ens fo r 10 m inutes. T h e speci m ens th en w ere d ried with an a ir syringe, and the com posite resin was b o nded as previously described. GROUP C. T h is g ro u p o f etched specim ens went th ro u g h an ad ditional porcelain firing cycle consisting o f raising the te m p e ra tu re to 920 F fo r .5 m inute. T h is additional step was to sim u late a clinical technique o f porcelain m odifica tion, such as a stain-glazing p ro c ed u re . T h e com posite resin th e n was b o n d ed as before.
T h e m ean shear bond stren g th s fo r the test g ro u p s a re show n in Figure 2. No significant differences in com posite resin bond stre n g th w ere fo u n d betw een the test g ro u p s at a level o f P < .05 using a one-way analysis o f variance.
Discussion
T h e resu lts o f this investigation w ould suggest th a t an additional ap p o in tm e n t to tre a te d with fingernail varnish as a p ro tectan t p e r f o r m th e e le c tro -e tc h in g o f re sin applied in one coat over th e etched surface. bo n d ed retain ers may be unnecessary. Al T his, again, was follow ed by the saliva co ntam i th o u g h sim ple im m ersion into the n atu ral nation, the cleaning technique, a n d the com pos saliva d id n o t red u ce the bond stren g th o f ite resin bonding. the com posite resin, a m ore severe co n A listing o f the trea tm e n ts th e test gro u p s tam ination, such as food debris o r plaque received is show n in T ab le 1. All specim ens ac c u m u la tio n p re sse d in to th e etch e d w ere stored in distilled w ater fo r 7 days a t 37 C m etal, may influence bo n d in g seriously. b efo re testing fu rth e r. In th ese cases, th e clean in g te ch n iq u e w ould be o f g rea ter value an d should be Bond strength test considered. T h e single, subsequent porcelain firing, T h e sh e a r b o n d s tre n g th o f the com posite resin
Table 1 ■ Summary of the treatments applied to each of the experimental groups. After etching, the base metal tabs were divided into six test groups of ten specimens each. Each test group received the treatments in the order listed under the corresponding head. All specimens were stored in distilled water G roup A
Group B
G roup C
G roup D
G roup E
Group F
Electro-etch
Electro-etch
Electro-etch Porcelain-bake
Electro-etch
Electro-etch Unfilled resin Saliva contamination Soap-acetone Composite resin
Electro-etch Fingernail varnish Saliva contamination Soap-acetone Composite resin
Saliva contamination Composite resin
Composite resin
360 ■ JADA, Vol. 112, March 1986
Composite resin
Saliva contamination Soap-acetone Composite resin
RESEARCH
2 0 -1 1 8 -
A
B
C
D
E
F
Fig 2 ■ Com posite shear bond strengths (striped bars) of each test group with standard deviations (solid bars). No significant differences in com posite resin bond strength were found between the test groups at a level of P < .05 using a one-way analysis o f variance.
sim ulating the glazing technique, did not a p p e a r to influence the retentive qualities o f th e electro-etched surface. Because the base m etal can be expected to oxidize d u r ing these firings, fu rth e r investigation is w arran ted to exam ine the influence o f ad ditional firing cycles on retention. T h e use o f the p rotectan t agents, the unf illed resin an d varnish, d id not h a m p e r the b o n d in g o f the com posite resin; yet, th e protective agents did not o ffe r any ad vantage over the cleaning technique. T h e use o f this technique may have a lim ited application in view o f the additional step req u ired an d the inability to p erfo rm ad d itional porcelain firings with the protec tants in place. Conclusions From this study, th e following conclusions are suggested: — N o ap p a ren t ef fect o f saliva contam i natio n on the bond strength o f the resin to the etch ed m etal was found. — P ro te c ta n ts, such as u n fille d BISGMA an d fingernail varnish, did not in
crease th e shear bond stren g th signifi cantly. — T h e influence of a porcelain cycle was n ot fo u n d to have a deleterious effect on the retention o f the electro-etched su r face.
------------------- J A D A ---------------------T h e authors have no commercial interests in the products m entioned in this report. T h e authors thank Dr. Martin C. Cornelia for his help and technical expertise. D r. B allesteros is chief, resto rativ e d en tistry , Homestead Air Force Base, FL. Dr. Duke is chief, dental materials, departm ent o f general dentistry, W ilford Hall USAF Medical Center, Lackland Air Force Base, TX. Dr. Norling is assistant professor and head, division of biomaterials, departm ent o f restora tive dentistry, University of T exas H ealth Science C enter Dental School, San Antonio, TX. Dr. Mayhew is director, general practice residency, Barksdale Air Force Base, LA. Address requests for reprints to Dr. Mayhew, 6202 Gaylyn Dr, Shreveport, LA 711054826. 1. Buonocore, M.G. A simple m ethod o f increasing the adhesion o f acrylic filling materials to enamel sur faces. J Dent Res 34:849-853, 1955. 2. Bowen, R.L. Dental filling material comprising
REPORTS
vinyl silane treated fused silica and a binder consisting o f the reaction product o f bis phenol and glycidyl acrylate. US Patent no. 3066, 112, 1962. 3. Laswell, H.R.; Welk, D.A.; and Regenos, J.W . Attachm ent o f resin restorations to acid pretreated enam el. JADA 82(3):558-563, 1971. 4. Miura, F.; Nakagawa, K.; and Ishizaki, A. Direct b o n d in g sy stem s in g e n e ra l d e n tis tr y . JA D A 88(2):360-366, 1974. 5. H annah, C.M., and Combe, E.C. Mechanical properties o f composite restorative materials. B r D ent J 140:167-173, 1976. 6. Mitchem, J.C., and T u rn er, L.R. T he retentive stre n g th s o f acid-etched re ta in e d resins. JA D A 89(5): 1107-1110, 1974. 7. Soetopo, D.R.; Beech, D.R.; and Hardwick, J.L. Mechanisms o f adhesion o f polymers to acid-etched enamel. J Oral Rehabil 5:69-80, 1978. 8. Council on Dental Materials and Devices. Status report on acid etching procedures. JADA 97(3):505508, 1978. 9. Galan, J.; Mondelli, J.; and Coradazzi, J.L. Mar ginal leakage of two composite resin systems. J Dent Res 55:74-76, 1976. 10. Buonocore, M.G. Retrospections on bonding. Dent Clin N orth Am 25:241-255, 1981. 11. R upp, N.W. Clinical placem ent and p erfo r m ance o f composite resin restorations. J Dent Res 58:1551-1557, 1979. 12. Rochette, A.L. Attachm ent o f a splint to enamel o f lower anterior teeth. J Prosthet Dent 30:418-423, 1973. 13. Howe, D.F., and Denehy, G.E. A nterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J Prosthet Dent 37:28-31,1977. 14. Eshelman, J.R.; Douglas, H.; and Barnes, D. T h e acid-etch bonded porcelain fused to metal bridge. Va Dent J 56:16-19, 1979. 15. Meetz, H.K. Comparison o f commercially avail able cem enting resin m aterials for the M aryland bridge. J Dent Res 62:458, 1983. 16. Wolf, E.; Fine, L.; and Cap, B. Acid-etched an terior fixed partial prostheses. Gen Dent 28:50-53, 1980. 17. Peck, C.; Doukoudakis, A.; and Doukoudakis, S. T he use o f acid-etch metal retainers. CDS Rev 74:27-29, 1981. 18. Yanover, L.; Croft, W.; and Pulver, F. T he acid-etched fixed prosthesis. JADA 104(3):325-328, 1982. 19. McLaughlin, G. Composite bonding of etched metal anterior splints. Com pend Contin Educ Dent 2:279-283, 1981. 20. Williams, V.; Drennon, D.; and Silverstone, L. T h e effect of retainer design on the retention o f filled resin acid-etched fixed partial dentures. J Prosthet Dent 48:417-423, 1982. 21. Livaditis, G.J., and Thom pson, V.P. Etched castings: an improved mechanism for resin-bonded retainers. J Prosthet Dent 47:52-58, 1982. 22. T hom pson, V.P., and Livaditis, G.J. Etched casting acid-etch composite bonded posterior bridges. Pediatr Dent 4:38-43, 1982. 23. Simonsen, R.J.; T hom pson, V.P.; and Barrack, G. Etched cast restorations: clinical and laboratory techniques. Chicago, Quintessence Publishing Co, Inc, 1983. 24. W ood, M., an d T h o m p so n , V.P. A n terio r etched cast resin-bonded retainers: an overview o f d e sign, fabrication, and clinical use. Com pend Contin Educ Dent 4:247-256, 1983.
Ballesteros-Others : INFLUENCE OF CONTAMINATION ON STRENGTH OF RETAINER ■ 361
REPORTS
This investigation examines the influence o f p otential sources o f contam ination on the resin bond strength o f a base metal alloy. Sixty specimens were cast in a base m etal alloy and etched. Composite resin cylinders were bonded to six groups o f ten specimens each and tested fo r shear bond strength using a testing machine a t a strain rate o f .5 mmlmin. Five o f the test groups received a different set o f treatm ents, and one o f the test groups was a control group. An analysis o f variance disclosed no significant differences in bond strengths among any o f the test groups at a level o f P < .05.
The influence of contamination on the bond strength of an etched resin-bonded retainer Tomas J. B allesteros, D M D Edward S. Duke, D D S , M SD Barry K. N orling, P hD Robert B. May hew, D M D , P hD
n 1955, B u o n o co re1 showed that an unfilled acrylic resin could be b o n d ed to enam el surfaces that have been treated with a phosphoric acid solution. T h e b o n d in g was m echanical an d was provided by th e resin m aterial flow ing into m icroporosities developed in th e enam el by the etchant. T h is technique has been investigated f u rth e r a n d is com p a tib le w ith th e im p ro v e d B IS-G M A resin-based system s as well.2"5 Factors such as in creased re te n tio n ,6,7 resistance to m icro leak ag e,8-9 a n d im p ro v e d clinical p erfo rm an ce10,11 have led to th e accep tance o f the acid-etching technique fo r use with com posite resin restorations. A uniq u e application o f th e acid-etching tech n iq u e was re p o rte d by R o c h ette.12 T h e technique involved the bond in g o f a p erfo ra ted perio d o n tal splint to etched enam el w ith an unfilled resin. F u rth e r m odifications o f this technique, including the attach m en t o f a p o n tic,13 the substitu tion o f a base m etal for gold alloys,14 and the use o f im proved resin cem en ts,15 gave rise to an alternative technique fo r replac ing m issing teeth.
I
T h is so-called M a ry la n d b rid g e , o r resin-bonded reta in er, has been rep o rted as useful in several clinical applications in c lu d in g tr e a tm e n t o f y o u n g p a tie n ts, in te rim fix ed p ro sth e s e s, p e rio d o n ta l splints, and m aintenance a fte r o rth o d o n tic trea tm e n t, as well as an econom ic alter native to conventional fixed partial d e n tu res.16' 18 A s u b s e q u e n t m o d if ic a tio n to th e resin-bonded reta in er was in tro d u ced by M cLaughlin.19 R ath er th an use the p erfo rations fo r attach m en t o f th e resin to the fram ew ork, M cLaughlin in tro d u ced the process o f electrolytically etching the base m etal as a m echanism for resin attach m ent. T h e electro-etching technique o f fers an im p ro v em en t over the use o f p e r fo ra tio n s in th a t th e b o n d stre n g th is g re a te r,20 less clinical w ear o f com posite resin occurs,21 an d a g rea ter resistance to m icroleakage exists.22 A long w ith th e a fo re m e n tio n e d im provem ents in th e resin-bonded reta in er tech n iq u e, a d isad v an tag e also has d e veloped. W hereas the p erfo ratio n s could be drilled initially by the laboratory, o r at
chairside by the d entist, it has been rec o m m e n d e d th a t th e electro -etch in g be p erfo rm ed afte r th e try-in ap p o in tm e n t.23 T h is reco m m en d atio n was m ad e to avoid co n tam ination o f th e etched m etal th a t could resu lt from saliva in tro d u ced d u rin g th e try-in, o r from su b seq u en t p ro ce d u re s such as ad ditional porcelain firings. All o f these facto rs may je o p a rd iz e successful b o n d in g o f th e com posite resin .21,23 I f the d ental clinic does not have th e necessary eq u ip m en t to p erfo rm th e electro-etching, th e appliance should be re tu rn e d to the laboratory a n d an ad ditional ap p o in tm e n t should be m ad e fo r final cem entation. Som e suggestions have been re p o rte d as useful fo r p rev en tin g contam ination o f th e etch ed m etal surface. T h ey included: adju stin g th e prosthesis w ithout fully seat ing it, using th e ru b b e r dam , an d w ashing the appliance with soap an d rinsing it with aceto n e.23,24 C u rren tly , n o n e o f th e su g gestions has been substantiated. T h is in v e stig a tio n ex a m in e s th e in flu e n c e o f saliva an d p o rcelain firings on th e bond stren g th o f com posite resin to an etched base m etal alloy. I n ad dition, techniques o f JADA, Vol. 112, March 1986 ■ 359
RESEARCH
REPORTS
w ashing an d of applying a protectan t o f unfilled resin o r v arnish are investigated.
Methods and materials Specimen preparation Sixty specim ens, 10 x 10 x 1 m m , w ere cast in a base m etal alloy (R exillium III) as directed by th e m a n u fa c tu re r. T o sim ulate th e initial a ppli cation o f p orcelain, th e 60 tabs o f m etal w ere fired in a porcelain oven (U ltra Mat) in the follow ing m an n e r: oxidation cycle, 990 F, with vacuum , 3 m inutes; o paque bake, 990 F, with vacuum , 1.5 m inutes; first bake, 960 F, with vacuum , 1.5 m inutes; second bake, 960 F, with vacuum , 1.5 m inutes; a n d glaze bake, 920 F, no vacuum , .5 m inute. E lectrolytic e tc h in g o f th e specim ens was d o n e using an e tc h in g m achine (Fig 1).
Electrolytic etching technique Attach the electrode to one side of the specim en using an orthodontic spot welder; verify the electrical continuity. Mask the electrode side and the edges of the specim en with fingernail varnish. Clean the surface to be etched with 25-/xm alum inum oxide air abrasive. Etch the specim en in a 10% solution of H 2SO 4 acid for 3 m inutes at a current density o f 300 mA applying constant ultrasonic agitation. Clean the etched specim en in an 18% solution o f HC1 acid for 10 m inutes with ultrasonic agitation. Verify characteristic dendritic etch with a stereo m icroscope at a magnification X 50. Remove the m asking varnish in two changes of acetone in an ultrasonic cleaner. Fig 1 ■ Electrolytic etching o f the specim ens was done using an etching m achine with the technique described.
GROUP D. T h is g ro u p o f e tch ed specim ens first was co n tam in ated with the n a tu ra l saliva for 10 m inutes, th e n a cleaning tre a tm e n t was p e r fo rm ed using a soap solution (Hebiclens) o f 1 p a rt soap 5 p a rts w ater, fo r 10 m inutes in an ultrasonic clean er follow ed by acetone fo r 10 m inutes in an ultrasonic cleaner. T h e com posite resin th en was b o n d e d as before.
to th e e tch ed m etal tabs was d e te rm in e d u sin g a testing m achine (In stro n Universal) a t a cross head speed o f .50 m m /m in. T h e u p p e r shearing blade was placed flush with the m etal tab s u r face to e n su re load in g p e rp en d icu la r to the com posite resin cylinders. T h e m etal tabs w ere stabilized using a vise fixture.
Results
co n tro l g ro u p . A 6 m m in diam eter, 4 m m in height T eflo n tube was used to bond the com posite resin to the e tch ed m etal tabs. T h e u n filled resin (B onding A gent), follow ed by the com posite resin (A daptic), was in serted in to the tube. T h is resulted in a com posite resin cylin d e r, 4.85 m m in diam eter, b o n d ed p e rp en d icu larly to the e tch ed m etal surface.
GROUP E. T h is g ro u p o f e tch ed specim ens re ceived the first p ro tec ta n t, in th e form o f the unfilled resin, b ru sh ed on th e surface. T o m ain tain a clinically acceptable thickness o f unfilled resin (to allow seating o f the appliance in the m outh), the m etal tabs w ere pressed against a slab o f dental stone until the resin h a d set. T his p ro c e d u re sim u la ted the p o sitio n in g o f th e resin-bonded re ta in e r on the w orking m odel. T h e resin-coated tabs th en w ere contam inated with saliva, cleaned with acetone, a n d b o nded with com posite resin.
GROUP B . This g ro u p o f e tch ed specim ens was
GROUP F . T h is g ro u p o f etched specim ens was
Test groups A fter e tching, the base m etal tabs w ere divided into six test g ro u p s o f ten specim ens each. T h e test g ro u p s received th e follow ing treatm ents: GROUP A. T h is g ro u p of e tc h ed specim ens was the
co n tam in ated with n a tu ra l saliva by su b m e rg ing the specim ens fo r 10 m inutes. T h e speci m ens th en w ere d ried with an a ir syringe, and the com posite resin was b o nded as previously described. GROUP C. T h is g ro u p o f etched specim ens went th ro u g h an ad ditional porcelain firing cycle consisting o f raising the te m p e ra tu re to 920 F fo r .5 m inute. T h is additional step was to sim u late a clinical technique o f porcelain m odifica tion, such as a stain-glazing p ro c ed u re . T h e com posite resin th e n was b o n d ed as before.
T h e m ean shear bond stren g th s fo r the test g ro u p s a re show n in Figure 2. No significant differences in com posite resin bond stre n g th w ere fo u n d betw een the test g ro u p s at a level o f P < .05 using a one-way analysis o f variance.
Discussion
T h e resu lts o f this investigation w ould suggest th a t an additional ap p o in tm e n t to tre a te d with fingernail varnish as a p ro tectan t p e r f o r m th e e le c tro -e tc h in g o f re sin applied in one coat over th e etched surface. bo n d ed retain ers may be unnecessary. Al T his, again, was follow ed by the saliva co ntam i th o u g h sim ple im m ersion into the n atu ral nation, the cleaning technique, a n d the com pos saliva d id n o t red u ce the bond stren g th o f ite resin bonding. the com posite resin, a m ore severe co n A listing o f the trea tm e n ts th e test gro u p s tam ination, such as food debris o r plaque received is show n in T ab le 1. All specim ens ac c u m u la tio n p re sse d in to th e etch e d w ere stored in distilled w ater fo r 7 days a t 37 C m etal, may influence bo n d in g seriously. b efo re testing fu rth e r. In th ese cases, th e clean in g te ch n iq u e w ould be o f g rea ter value an d should be Bond strength test considered. T h e single, subsequent porcelain firing, T h e sh e a r b o n d s tre n g th o f the com posite resin
Table 1 ■ Summary of the treatments applied to each of the experimental groups. After etching, the base metal tabs were divided into six test groups of ten specimens each. Each test group received the treatments in the order listed under the corresponding head. All specimens were stored in distilled water G roup A
Group B
G roup C
G roup D
G roup E
Group F
Electro-etch
Electro-etch
Electro-etch Porcelain-bake
Electro-etch
Electro-etch Unfilled resin Saliva contamination Soap-acetone Composite resin
Electro-etch Fingernail varnish Saliva contamination Soap-acetone Composite resin
Saliva contamination Composite resin
Composite resin
360 ■ JADA, Vol. 112, March 1986
Composite resin
Saliva contamination Soap-acetone Composite resin
RESEARCH
2 0 -1 1 8 -
A
B
C
D
E
F
Fig 2 ■ Com posite shear bond strengths (striped bars) of each test group with standard deviations (solid bars). No significant differences in com posite resin bond strength were found between the test groups at a level of P < .05 using a one-way analysis o f variance.
sim ulating the glazing technique, did not a p p e a r to influence the retentive qualities o f th e electro-etched surface. Because the base m etal can be expected to oxidize d u r ing these firings, fu rth e r investigation is w arran ted to exam ine the influence o f ad ditional firing cycles on retention. T h e use o f the p rotectan t agents, the unf illed resin an d varnish, d id not h a m p e r the b o n d in g o f the com posite resin; yet, th e protective agents did not o ffe r any ad vantage over the cleaning technique. T h e use o f this technique may have a lim ited application in view o f the additional step req u ired an d the inability to p erfo rm ad d itional porcelain firings with the protec tants in place. Conclusions From this study, th e following conclusions are suggested: — N o ap p a ren t ef fect o f saliva contam i natio n on the bond strength o f the resin to the etch ed m etal was found. — P ro te c ta n ts, such as u n fille d BISGMA an d fingernail varnish, did not in
crease th e shear bond stren g th signifi cantly. — T h e influence of a porcelain cycle was n ot fo u n d to have a deleterious effect on the retention o f the electro-etched su r face.
------------------- J A D A ---------------------T h e authors have no commercial interests in the products m entioned in this report. T h e authors thank Dr. Martin C. Cornelia for his help and technical expertise. D r. B allesteros is chief, resto rativ e d en tistry , Homestead Air Force Base, FL. Dr. Duke is chief, dental materials, departm ent o f general dentistry, W ilford Hall USAF Medical Center, Lackland Air Force Base, TX. Dr. Norling is assistant professor and head, division of biomaterials, departm ent o f restora tive dentistry, University of T exas H ealth Science C enter Dental School, San Antonio, TX. Dr. Mayhew is director, general practice residency, Barksdale Air Force Base, LA. Address requests for reprints to Dr. Mayhew, 6202 Gaylyn Dr, Shreveport, LA 711054826. 1. Buonocore, M.G. A simple m ethod o f increasing the adhesion o f acrylic filling materials to enamel sur faces. J Dent Res 34:849-853, 1955. 2. Bowen, R.L. Dental filling material comprising
REPORTS
vinyl silane treated fused silica and a binder consisting o f the reaction product o f bis phenol and glycidyl acrylate. US Patent no. 3066, 112, 1962. 3. Laswell, H.R.; Welk, D.A.; and Regenos, J.W . Attachm ent o f resin restorations to acid pretreated enam el. JADA 82(3):558-563, 1971. 4. Miura, F.; Nakagawa, K.; and Ishizaki, A. Direct b o n d in g sy stem s in g e n e ra l d e n tis tr y . JA D A 88(2):360-366, 1974. 5. H annah, C.M., and Combe, E.C. Mechanical properties o f composite restorative materials. B r D ent J 140:167-173, 1976. 6. Mitchem, J.C., and T u rn er, L.R. T he retentive stre n g th s o f acid-etched re ta in e d resins. JA D A 89(5): 1107-1110, 1974. 7. Soetopo, D.R.; Beech, D.R.; and Hardwick, J.L. Mechanisms o f adhesion o f polymers to acid-etched enamel. J Oral Rehabil 5:69-80, 1978. 8. Council on Dental Materials and Devices. Status report on acid etching procedures. JADA 97(3):505508, 1978. 9. Galan, J.; Mondelli, J.; and Coradazzi, J.L. Mar ginal leakage of two composite resin systems. J Dent Res 55:74-76, 1976. 10. Buonocore, M.G. Retrospections on bonding. Dent Clin N orth Am 25:241-255, 1981. 11. R upp, N.W. Clinical placem ent and p erfo r m ance o f composite resin restorations. J Dent Res 58:1551-1557, 1979. 12. Rochette, A.L. Attachm ent o f a splint to enamel o f lower anterior teeth. J Prosthet Dent 30:418-423, 1973. 13. Howe, D.F., and Denehy, G.E. A nterior fixed partial dentures utilizing the acid-etch technique and a cast metal framework. J Prosthet Dent 37:28-31,1977. 14. Eshelman, J.R.; Douglas, H.; and Barnes, D. T h e acid-etch bonded porcelain fused to metal bridge. Va Dent J 56:16-19, 1979. 15. Meetz, H.K. Comparison o f commercially avail able cem enting resin m aterials for the M aryland bridge. J Dent Res 62:458, 1983. 16. Wolf, E.; Fine, L.; and Cap, B. Acid-etched an terior fixed partial prostheses. Gen Dent 28:50-53, 1980. 17. Peck, C.; Doukoudakis, A.; and Doukoudakis, S. T he use o f acid-etch metal retainers. CDS Rev 74:27-29, 1981. 18. Yanover, L.; Croft, W.; and Pulver, F. T he acid-etched fixed prosthesis. JADA 104(3):325-328, 1982. 19. McLaughlin, G. Composite bonding of etched metal anterior splints. Com pend Contin Educ Dent 2:279-283, 1981. 20. Williams, V.; Drennon, D.; and Silverstone, L. T h e effect of retainer design on the retention o f filled resin acid-etched fixed partial dentures. J Prosthet Dent 48:417-423, 1982. 21. Livaditis, G.J., and Thom pson, V.P. Etched castings: an improved mechanism for resin-bonded retainers. J Prosthet Dent 47:52-58, 1982. 22. T hom pson, V.P., and Livaditis, G.J. Etched casting acid-etch composite bonded posterior bridges. Pediatr Dent 4:38-43, 1982. 23. Simonsen, R.J.; T hom pson, V.P.; and Barrack, G. Etched cast restorations: clinical and laboratory techniques. Chicago, Quintessence Publishing Co, Inc, 1983. 24. W ood, M., an d T h o m p so n , V.P. A n terio r etched cast resin-bonded retainers: an overview o f d e sign, fabrication, and clinical use. Com pend Contin Educ Dent 4:247-256, 1983.
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