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Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy

Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium... J Adv Prosthodont 2009;1:41-6 ORIGINAL ARTICLE DOI:10.4047/jap.2009.1.1.41 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy 1 2 2 Su-Sung Kim , DDS, Mong-Sook Vang *, DDS, MSD, PhD, Hong-So Yang , DDS, MSD, PhD, 2 3 Sang-Won Park , DDS, MSD, PhD, Hyun-Pil Lim , DDS, MSD 1 2 3 Graduate Student, Professor, Clinical Professor, Department of Prosthodontics, Graduate School, Chonnam National University STATEMENT OF PROBLEM. The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive fail- ure and increases microleakage. PURPOSE. This study evaluated the shear bond strengths of a heat cure denture base resin to commer- cially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND MATHODS. Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the con- trols. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS. The primers significantly (P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy primer (MDP monomer) showed higher bond strength than those primed with the MR bond (MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS. The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy primer , which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to tita- nium than a MR bond , which contains the carboxylic acid monomer, MAC-10. KEY WORDS. Heat cure denture base resin, Adhesive primers [J Adv Prosthodont 2009;1:41-6] microleakage of oral fluids in the finish lines, which causes the INTRODUCTION 1,2 accumulation of oral debris, microorganisms, and stains. As a result, the propagation of microorganisms contributes to Polymethylmethacrylate (PMMA) is the material of choice an unfavorable soft tissue response. for constructing denture bases (95%). However, there are The bonding of resin to dental alloys has improved signifi- problems with the integrity of, not of the between metal and cantly over the last decade, and various bonding methods and PMMA interfaces. Despite many disadvantages of PMMA, such techniques have been developed for base metal alloys, such as as few sites for chemical bonding to the metals used in remov- electrolytic etching, chemical etchant, and silica coating. The able and complete arch fixed frameworks, it is one of the availability of adhesive primer for base metals that are capa- materials most often used for conventional removable and ble of chemically bonding to a casting dental alloy has simplified implant-supported prosthodontics. The integrity of the bond the surface preparation of base metal alloys. at the PMMA-to-metal interface is important for the service For approximately 20 years, the application of a 4-methacry- longevity of a prosthesis. loxyethyl trimellitate anhydride (4-META) bonding system to The mechanical retention of a denture resin (PMMA) in a removable partial dentures (RPDs) has been examined as a way removable prosthesis is usually provided by the framework 5,6 to prevent the problems previously mentioned. Yasuda et al. design in the denture base, for example, using beads, posts, bars, reported that a higher bond strength was obtained for cobalt- an open lattice, a mesh, or some macroscopic retentive 3,4 chromium (Co-Cr) alloys with a 4-META bonding system design. The correct positioning of the finish lines and the sharp and also suggested in a longitudinal in vivo research study that undercut line angles of the denture resin margin are also the formation of bonds between these materials is clinically sta- essential for preventing failure of the resin at the junction with 6,7 1,5 ble. the framework. Chemical bonding between the metal frame- Co-Cr alloys are commonly used for RPDs and complete den- work and the denture base resin is also important. Poor tures that incorporate metal components. Compared with chemical bonding in that area is a significant clinical problem, alternative type IV gold alloys, Co-Cr alloys are relatively inex- which often introduces adhesive failure and the increasing Corresponding author: Mong-Sook Vang Department of Prosthodontics, School of Dentistry, Chonnam National University 300 Yongbond-dong, Buk-gu, Gwang-Ju, 500-070, Korea Tel, +82 62 530 5638: e-mail, [email protected] Received January 28, 2009/ Last Revison February 25, 2009/ Accepted March 4, 2009 41 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al pensive, and are approximately twice as rigid. However, minute using ultrasonic cleaner (Ultraschall. KRUPP Corp, they may contain elements (Co and or Cr) that have been alleged Germany). to produce sensitivity or allergic reactions in some patients.8 Because of the potential of titanium to reduce and eliminate some Preparation of specimens for shear testing of these reported problems associated with Co-Cr alloys; First, a hexagonal shape (2.5 mm edge) wax was attached to titanium has been used increasingly in clinical practice for remov- the discs to fabricate a part of the resin tap. The waxes were fixed able prosthesis. in the same dimension by preparing silicone models and Many studies have evaluated the adhesion of composites to pouring the melted waxes. Ninety wax specimens in the CP titanium with adhesive primers, and high bond strength same parameter were fabricated. 9-15 being reported. However, few studies have evaluated the adhe- The waxes adhered to the dried specimens. The specimens sion of denture base resin to primed titanium for use in were then invested in the conventional way. After hardening 20-22 RPDs. In particular, there are few reports on the evaluation the investment, the remaining waxes were removed by hot water. of the bond strength of a heat cure denture base resin to a primed Immediately after drying the cleaned discs, two metal con- titanium sample. ditioners were applied to the air-abraded surfaces using a sponge This study examined the shear bond strength of a heat cure pellet according to the manufacturer's directions. The specimens resin as a denture base resin to cast CP titanium and Ti-6Al- with unprimed disc surfaces were also prepared as controls 4V alloy using two adhesive primers. These results were (Fig. 1). The resin separator was brushed on the investment and compared with those obtained with a Co-Cr alloy. the heat cure resin applied. Heat cure resin (Vertex-Vertex Dental B.V. co., Netherland) MATERIAL AND METHODS was polymerized according to the manufacturer's instruc- tions, i.e. in a heat curing unit (SE KI Dental Co. Korea) at 70℃ Table I lists the materials used in this study. Disc-shaped wax for 60 min followed by 100℃ for 30 min and then cooling for 120 patterns (10.0 mm in diameter and 2.5 mm thick) of CP titanium, min. All the specimens were immersed in water at 37℃ for 24 h. Ti-6Al-4V alloy (Kobesteel Co., Japan) were cast using a mag- nesia-based investment (Selevest CB, Selec Co., Japan) in an argon arc-centrifugal casting machine (Ticast Super R, Selec Co.) accord- ing to the manufacturer's instructions. For comparison, disc patterns (the same size as Ti-6Al-4V alloy) of a Co-Cr alloy (Biosil F, Degussa co., Ltd) were conventionally cast using a silica-based investment (Univest Silky, Shofu Dental Corp.) in a centrifugal induction melting machine (Neutrodyn Easyti, Manfred, Italy). Thirty cast discs were made for each alloy. After casting, the disk surfaces were finished with No. 600 silicon carbide paper under water followed by 250 μ m grain- sized aluminum oxide for 5 seconds using grit blaster (Micro sand blaster. Phoenix electric company Korea). The emis- sion pressure was 4.5 kgf/cm with the nozzle positioned approximately 5 mm from the surface of the metal adherent. Fig. 1. Metal conditioner were Fig. 2. Fabricated specimen. The grit-blasted cast disks were washed in acetone for 10 applied. Table I. Materials used for this Materials Identification Manufacturer Composition Metal CP titanium ASTM Grade II Kobe steel co., Ltd., Japan Ti > 99.0% Ti-6AL-4V ASTM Grade V Kobe steel co., Ltd., Japan Ti > 89.0%, 6.0% Al, 4.0% V Co-Cr alloy (Biosil F) Degussa co., Ltd., Germany Co 67%, Cr 28.5%, Mo 5.3% Primer Alloy primer Kuraray co., Ltd., Japan MDP, VBATDT MR Bond Tokuyama co., Ltd., Japan MAC-10 PMMA Vertex Vertex-Dental B.V. co., Netherland Methyl methacrylate MDP(10-methacryloyloxydecyl dehydrogen phosphate) MAC-10(11-methacryloyloxyundecan-1,1-decarboxylic acid) VABATDT(6-4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4 dithione) J Adv Prosthodont 2009;1:41-6 42 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al Measurement of shear bond strength the groups. Table IV shows the types of bond failure classified The shear bond strengths were measured using a screw-dri- as A or M for each group of specimens. Application of the ven universal testing machine (STM-5, United Calibration, USA) primers significantly (P < .05) improved the shear bond at a crosshead speed of 1.0 mm/min. The means and standard strengths of the heat cure resin to all metals (Table II, III). deviations (SD) of the shear bond strength (n = 5) were calculated The specimens primed with the Alloy primer showed a sig- and statistically analyzed with a 2-way analysis of variance nificantly higher bond strength (P < .05) than the specimens (ANOVA). primed with the MR bond on titanium. However, there was The factors for analysis were primer and metal. Then 2- no significant difference between the Alloy primer and MR way ANOVA, 1-way ANOVA and the Scheffe multiple com- bond on the Co-Cr alloy. parison test were performed at a significance level of α = .05. Mixed failure within the denture base resin was observed in After testing, the fracture surfaces of the specimens were the specimens primed with the Alloy primer . In addition, Mixed observed using an optical microscope (BX51 TRF, LYMPUS, failure and Adhesive failure were observed in the specimens JAPAN) at × 50 magnification to assess the type of bond fail- primed with the MR bond . Adhesive failure was observed in ure. The failure modes were categorized s either A (adhesive all control specimens (Table IV, Fig. 5). failure at the metal-PMMA interface) or M (mixed adhesive and cohesive failure). DISCUSSION RESULTS Titanium is a relatively new material in removable partial den- ture frameworks, and will most likely become more popular Fig. 4 and Table II shows the effect of the adhesive primers with the advancements in casting procedures and materi- on the shear bond strength of the heat cure resin to the cast tita- als. Since the introduction of the first fixed partial denture nium and cobalt-chromium alloy. Table III shows the means retained by implants, a type III gold alloy has been recom- and standard deviations (SD) of the shear bond strengths mended metal for the substructure because it is nontoxic, (MPa) of the 3 metals along with the statistical comparisons of no allergenic, corrosion resistant, easy to use, has adequate Fig. 3. Test configuration for debonding. Fig. 5. A: Adhesive failure at non-primed specimens. M: Mixed failure of adhesive and cohesive failures at Primed specimens. ×50: The fracture surface of the specimens were observed with and optical microscope. Table II. Shear bonding strength of three metal to two primer or non-primed of controls No primer MR bond Alloy primer Metal MPa SD MPa SD MPa SD Adhesive primer Co-Cr 3.4 0.6 17.8 4.0 17.1 2.6 CP Ti 2.4 0.3 5.9 2.1 15.9 2.5 Fig. 4. Shear bonding strength of three metal to two primer or Ti-6AI-4V 3.2 0.4 7.4 2.1 16.0 3.6 non-primed of controls. J Adv Prosthodont 2009;1:41-6 Bond Strength (MPa) Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al strength, and is relatively inexpensive. Commercially pure tita- decreased considerably after thermocycling. Jemt and Linden nium and Ti-6Al-4V alloy have similar desirable mechanical also showed that implant-supported prostheses with machined and physical properties. Clinical trials of titanium substructures titanium had bonding problems between the machined surface are underway to identify the variables that might negatively and the PMMA. Therefore, conventional bonding between an affect the life expectancy of an implant and the use of the pros- acrylic resin denture base and a titanium framework may theses. A failure of the bond at the PMMA-titanium interface not be sufficient to prevent microleakage. can result in prosthetic failure and create space between the met- The surface of pure titanium metal is usually coated with a al and PMMA, where oral debris, microorganism, and stains titanium oxide that is stable in an atmospheric environment. can accumulate. A poor bond between a titanium frame- This indicates that the primers actually adhere to titanium oxide work and PMMA can compromise the quality of the prosthesis rather than to pure titanium. Some metal oxides can react with and potentially place the patients at risk of an infection from carboxylic or phosphoric acid derivatives to form a chemical opportunistic microorganism. bond. In order to evaluate the value of commercially pure (CP) tita- Kojima et al. synthesized the 6-4-vinylbenzyl-n-propyl)amino- nium as a material for cast partial denture frameworks, 1,3,5-triazine-2,4-dithione monomer, which does not contain Yamauchi et al. examined the results of a follow-up examination a free mercapto group, and reported that the VBATDT primer of patients who had used titanium prosthesis. They report- improved the bond durability of an MMA-PMMA-TBBO ed that there were no clinical problems with cast CP titanium resin joined to precious metal alloys. However, VBATDT partial denture frameworks. However, there was some dye pen- was ineffective in increasing the bond strength of MMA-TBB etration from the finish line found despite the use of an adhe- resin to base metal dental casting alloys such as Co-Cr and nick- sive resin containing 4-META (META-DENT, Sun Medical, el-chromium. It was for this reason that MAC-10 (11- Kyoto, Japan) as a denture base resin. In a study of this phe- methacryloyloxyundecan-1,1-decarboxylic acid) and MDP nomenon, Matsumura et al. reported the bond strength of (10-methacryloyloxydecyl dehydrogen phosphate) were used 4-META containing an adhesive resin to pure titanium in this study. Regarding the bond strength, the use of any of the primers in previous studies would be acceptable for achieving clinically durable bonds to titanium frameworks. However, cast titanium frameworks, particularly CP titanium, are more flexible (low- er elastic modulus) than the Co-Cr alloy. Denture deflection during use can cause debonding between the denture base resin and the framework, and resulting eventually in resin fracture. Therefore, titanium frameworks should also be designed (and fabricated) to be hard enough so that denture deflection is kept to a minimum. It was for this reason that Ti-6AL-4V alloy ASTM Grade Ⅴ was used in this study. The aim of this study was to evaluate the shear bond Fig. 6. Chemical structure of MAC-10, MDP. strengths of a PMMA denture base resin to cast pure titanium, Table III. Summary of 2-way analysis of variance for shear bond strengths Source Degree of freedom Sum of square F-value P-value Metal 2 151,787 26,530 .000 Primer 2 1,070,802 187,161 .000 Metal*Primer 4 94,999 16,605 .000 Residual 63 5,721 Total 72 Table IV. Type of bond failure Primer METAL No primer MR.Bond Alloy primer Co-Cr AAAAAAAA AMMMMMMM AMMMMMMM Ti Gr II AAAAAAAA AAAAAMMM MMMMMMMM Ti 6AI 4V AAAAAAAA AAAAMMMM MMMMMMMM A: adhesive failure; M: adhesive + cohesive failure J Adv Prosthodont 2009;1:41-6 44 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al Ti-6Al-4V, and a cobalt-chromium alloy using two adhesive um and cobalt-chromium framework. CP titanium, Ti-6Al-4V, � � primers (MR bond : MAC-10, Alloy primer : MDP, VBATDT). or Co-Cr alloy discs were cast, and the bonding surfaces of the The difference in shear bond strengths of the primed and metal disk (10 mm diameter, 2.5 mm thick) were treated � � unprimed specimens was significant (P < .05) (Table III). with 2 different metal primers (MR bond , Alloy primer ). The May et al. suggested that the shear bond strength of heat- specimens without the primer were also prepared as the processed PMMA bonded to a machined surface of wrought control. CP titanium with 110 μ m alumina air abrasion and a silane coat- The shear bond strengths were determined at a crosshead ing was 63% higher than the specimens with no pretreat- speed of 1.0 mm/min. The application of any one of the two 21,22 ment. Other studies reported that the application of Rocatec primers tested, regardless of the brand used, significantly bonding material (ESPE GmbH, Seefeld/Oberbay, Germany) improved the shear bond strength of the denture base resin to increased the bond strength by 68% compared with the con- any of the cast metals tested (CP titanium, Ti-6Al-4V, and Co- trol. The application of heat-cured PMMA containing 4- Cr alloy). The specimens primed with the Alloy primer META (META-DENT) demonstrated a 3.7 fold higher bond showed higher bond strength than those primed with the strength than the control group. Shiragami et al. evaluated the MR bond on titanium. However, significant difference was not tensile bond strengths of a similar resin to cast Ti-6Al-4V observed on the Co-Cr alloy. Only adhesive failure was evident alloy with 3 adhesive primers. They used the original Metal at the metal-resin interface of all the non-primed specimens, Primer, Meta Base M, and Cesead Opaque Primer materials and while the primed specimens showed mixed failure of adhesive found greater bond strength than with the untreated specimens. and cohesive failure. In this study, the shear bond strength of heat cure denture With the use of appropriate adhesive metal primers, it is pos- base resin to a metal surface treated with an adhesive primer sible not only to eliminate the need for surface preparations of was greater than the specimens with no treatment. Therefore, the metal frameworks before the application of heat cure the two metal conditioners had a significant effect on the resins but also to reduce the need for retentive devices on the bond between the heat cure denture base resin and both metal substructure. alloys (Fig. 4 and Table II). While the shear bond strengths of In particular, the Alloy primer , which contains the phosphoric � � the Alloy primer were higher than those of the MR bond on acid monomer, MDP, is clinically more acceptable for bond- cast pure titanium, Ti-6Al-4V alloy, there was no significant dif- ing heat cure resin to titanium than the MR bond , which con- ference observed on the Co-Cr alloy. It is possible that the chem- tains the carboxylic acid monomer, MAC-10. ical bond of MDP to the titanium oxide is superior to that of MAC-10. Moreover, these results may be attributed to the dif- REFERENCES ferences in their composition, polymerization procedure or 1. Jacobson TE, Chang JC, Keri PP, Watanabe LG. Bond strength of mechanical properties. However, further research will be 4-META acrylic resin dentrue base to cobalt chromium alloy. J needed to answer this question. Prosthet Dent 1988;60:570-6. 2. Jacobson TE. The significance of adhesive denture base resin. Int The fractured site revealed bonding failure between the J Prosthodont 1989;2:163-72. denture base resin and metal interface in all comparative 3. Dunny JA, King GE. Minor connector disigns for anterior acrylic samples that had not been treated with a metal surface con- resin bases; a preliminary study. J Prosthet Dent 1975;34:496-502. 4. Brown DT, Desjardins RP, Chao EY. Fatigue failure in acrylic resin ditioner were observed. The reason for the failure was that the retaining minor connectors. J Prosthet Dent 1987;58:329-35. comparative, which showed a lower bonding strength than the 5. Sasaki M, Yasuda N, Mogi T, Ai M. Influence between metal and resin strength. This is similar to the results reported by resin on the finishing line of cobalt-chromium denture. Part 3. Ohkubo et al., who showed that bonding failure occurred Studies on finishing line structure. J Jpn Prosthodont Soc 24 1994;38:191-7. between the resin and metal interface . Mixed failure appeared 6. Yasuda N, Sasaki M, Mogi T, Ai M, Nakabayashi N. Influence be- in the resin and metal interface, which is considered to be the tween metal and resin on the finishing line of cobalt-chromium result between chemical bonding of metal and resin. denture. Part 2. Effect of 4-META on preventing dye penetration at the finishing line. J Jpn Prosthodont Soc 1978;22:761-5. Based on the results from other studies, the use of each 7. Yasuda N, Sasaki M, Shinogaya T, Ai M, Nakabayashi N. 20-25 adhesive primer with PMMA is recommended to improve Influence between metal and resin on the finishing line of the bond strength and durability to titanium. In this study, the cobalt-chromium denture. Part 7. A clinical evaluation of 4- META system : a five-year report. J Jpn Prosthodont Soc primers significantly (P < .05) improved the shear bond 1985;29:761-5 strength of the denture base resin to all metals. 8. Kononen M, Rintanen J, Waltimo A, Kempainen P. Titanium frame- work removable partial denture used for patients allergic to CONCLUSIONS other metals: a clinical report and literature review. J Prosthet Dent 1995;73:4-7. 9. Fujishima A, Fujimori S, Tamaki Y, Miyazaki T, Fujishima Y, Shiba This study evaluated the effect of adhesive primers on the shear A. A basic study on the fabrication of titanium veneered crown bond strength of heat cure denture base resin to a cast titani- with resin composites. (Part 2). Effect of surface treatments on bond- J Adv Prosthodont 2009;1:41-6 45 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al ing of resin composites. (Part 2). Effect of surface treatment on bond- metal primers on bonding a prosthetic composite resin to met- ing of resin composites with titanium. J Jpn Dent Mater als. J Prosthet Dent 1993;69:357-62. 1995;14(special issue):78-9. 19. Kojima K, Kadoma Y, Imai Y. Adhesion to precious metals uti- 10. Hansson O. Strength of bond with Comspan Opaque to three sil- lizing triazine dithione derivative monomer. J Jpn Soc Dent icoated alloys and titanium. Scand J Dent Res 1990;98:248-56. Mater Devices 1987;6:702-7. 11. Fujishima A, Fujishima Y, Ferracane JL. Shear bond strength of 20. May KB, Russell MM, Razzoog ME, Lang BR. The shear strength four commercial bonding systems to cp Ti. Dent Mater 1995;11:82- of polymethyl methacrylate bonded to titanium partial den- 6. ture framework material. J Prosthet Dent 1993;70:410-3. 12. Yoshida N. Clinical application of resin facing titanium crown by 21. May KB, Fox J, Razzoog ME, Lang BR. Silane to enhance the bond the non-retention method-bond strength of composite resin between polymethyl methacrylate and titanium. J Prosthet Dent materials for veneering to titanium. Ohu Dent J 1997;24:1-20. 1995;73:428-31. 13. Hansson O, Moberg LE. Evaluation of three silicoating methods 22. May KB, Van Putten MC, Bow DA, Lang BR. 4-META polymethyl for resin-bonded prostheses. Scand J Dent Res 1993;101:243-51. methacrylate shear bond strength to titanium. Oper Dent 14. Kern M, Thompson VP. Durability of resin bonds to pure titanium. 1997;22:37-40. J Prosthodont 1995;4:16-22. 23. Shiragami N, Kozono Y, Morikawa M. Bond of resin materials to 15. Kurtz K, Kabcenell J, Watanabe I, Okabe T. Shear bond strength titanium. Part 1. Effects of surface treatment. J Jpn Prosthodont of polymer-glass to cast titanium. J Dent Res 1998;77:272, Abstract Soc 1994;88(special issue):73. 24. Ohkubo C, Watanabe I, Hosoi T, Okabe T. Shear bond strengths 16. Yamauchi M, Sakai M, Kawano J. Clinical application of pure ti- of polymethylmethacrylate to cast titanium and cobalt-chromi- tanium for cast plate dentures. Dent Mater J 1988;7:39-47. um frameworks using five metal primers. J Prosthet Dent 17. Matsumura H, Kojima K, Kadoma Y, Masuhara E. Studies on den- 2000;83:50-7. tal self-curing resins (26). Effect of 4-META and 4-MET addition 25. Shimizu H, Kurtz KS, Tachii Y, Takahashi Y. Use of metal con- to the MMA-TBBO resin. [in Japanese] Shika Zairyo kikai ditioners to improve bond strengths of autopolymerizing den- 1984;3:480-9. ture base resin to cast Ti-6Al-7Nb and Co-Cr. J Dent 2006;34:117- 18. Yoshida K, Taira Y, Matsumura H, Atsuta M. Effect of adhesive J Adv Prosthodont 2009;1:41-6 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Advanced Prosthodontics Pubmed Central

Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy

Kim, Su-Sung; Vang, Mong-Sook; Yang, Hong-So; Park, Sang-Won; Lim, Hyun-Pil
The Journal of Advanced Prosthodontics , Volume 1 (1) – Mar 31, 2009
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Copyright © 2009 The Korean Academy of Prosthodontics
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2005-7806
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10.4047/jap.2009.1.1.41
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Abstract

J Adv Prosthodont 2009;1:41-6 ORIGINAL ARTICLE DOI:10.4047/jap.2009.1.1.41 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy 1 2 2 Su-Sung Kim , DDS, Mong-Sook Vang *, DDS, MSD, PhD, Hong-So Yang , DDS, MSD, PhD, 2 3 Sang-Won Park , DDS, MSD, PhD, Hyun-Pil Lim , DDS, MSD 1 2 3 Graduate Student, Professor, Clinical Professor, Department of Prosthodontics, Graduate School, Chonnam National University STATEMENT OF PROBLEM. The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive fail- ure and increases microleakage. PURPOSE. This study evaluated the shear bond strengths of a heat cure denture base resin to commer- cially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND MATHODS. Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the con- trols. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS. The primers significantly (P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy primer (MDP monomer) showed higher bond strength than those primed with the MR bond (MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS. The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy primer , which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to tita- nium than a MR bond , which contains the carboxylic acid monomer, MAC-10. KEY WORDS. Heat cure denture base resin, Adhesive primers [J Adv Prosthodont 2009;1:41-6] microleakage of oral fluids in the finish lines, which causes the INTRODUCTION 1,2 accumulation of oral debris, microorganisms, and stains. As a result, the propagation of microorganisms contributes to Polymethylmethacrylate (PMMA) is the material of choice an unfavorable soft tissue response. for constructing denture bases (95%). However, there are The bonding of resin to dental alloys has improved signifi- problems with the integrity of, not of the between metal and cantly over the last decade, and various bonding methods and PMMA interfaces. Despite many disadvantages of PMMA, such techniques have been developed for base metal alloys, such as as few sites for chemical bonding to the metals used in remov- electrolytic etching, chemical etchant, and silica coating. The able and complete arch fixed frameworks, it is one of the availability of adhesive primer for base metals that are capa- materials most often used for conventional removable and ble of chemically bonding to a casting dental alloy has simplified implant-supported prosthodontics. The integrity of the bond the surface preparation of base metal alloys. at the PMMA-to-metal interface is important for the service For approximately 20 years, the application of a 4-methacry- longevity of a prosthesis. loxyethyl trimellitate anhydride (4-META) bonding system to The mechanical retention of a denture resin (PMMA) in a removable partial dentures (RPDs) has been examined as a way removable prosthesis is usually provided by the framework 5,6 to prevent the problems previously mentioned. Yasuda et al. design in the denture base, for example, using beads, posts, bars, reported that a higher bond strength was obtained for cobalt- an open lattice, a mesh, or some macroscopic retentive 3,4 chromium (Co-Cr) alloys with a 4-META bonding system design. The correct positioning of the finish lines and the sharp and also suggested in a longitudinal in vivo research study that undercut line angles of the denture resin margin are also the formation of bonds between these materials is clinically sta- essential for preventing failure of the resin at the junction with 6,7 1,5 ble. the framework. Chemical bonding between the metal frame- Co-Cr alloys are commonly used for RPDs and complete den- work and the denture base resin is also important. Poor tures that incorporate metal components. Compared with chemical bonding in that area is a significant clinical problem, alternative type IV gold alloys, Co-Cr alloys are relatively inex- which often introduces adhesive failure and the increasing Corresponding author: Mong-Sook Vang Department of Prosthodontics, School of Dentistry, Chonnam National University 300 Yongbond-dong, Buk-gu, Gwang-Ju, 500-070, Korea Tel, +82 62 530 5638: e-mail, [email protected] Received January 28, 2009/ Last Revison February 25, 2009/ Accepted March 4, 2009 41 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al pensive, and are approximately twice as rigid. However, minute using ultrasonic cleaner (Ultraschall. KRUPP Corp, they may contain elements (Co and or Cr) that have been alleged Germany). to produce sensitivity or allergic reactions in some patients.8 Because of the potential of titanium to reduce and eliminate some Preparation of specimens for shear testing of these reported problems associated with Co-Cr alloys; First, a hexagonal shape (2.5 mm edge) wax was attached to titanium has been used increasingly in clinical practice for remov- the discs to fabricate a part of the resin tap. The waxes were fixed able prosthesis. in the same dimension by preparing silicone models and Many studies have evaluated the adhesion of composites to pouring the melted waxes. Ninety wax specimens in the CP titanium with adhesive primers, and high bond strength same parameter were fabricated. 9-15 being reported. However, few studies have evaluated the adhe- The waxes adhered to the dried specimens. The specimens sion of denture base resin to primed titanium for use in were then invested in the conventional way. After hardening 20-22 RPDs. In particular, there are few reports on the evaluation the investment, the remaining waxes were removed by hot water. of the bond strength of a heat cure denture base resin to a primed Immediately after drying the cleaned discs, two metal con- titanium sample. ditioners were applied to the air-abraded surfaces using a sponge This study examined the shear bond strength of a heat cure pellet according to the manufacturer's directions. The specimens resin as a denture base resin to cast CP titanium and Ti-6Al- with unprimed disc surfaces were also prepared as controls 4V alloy using two adhesive primers. These results were (Fig. 1). The resin separator was brushed on the investment and compared with those obtained with a Co-Cr alloy. the heat cure resin applied. Heat cure resin (Vertex-Vertex Dental B.V. co., Netherland) MATERIAL AND METHODS was polymerized according to the manufacturer's instruc- tions, i.e. in a heat curing unit (SE KI Dental Co. Korea) at 70℃ Table I lists the materials used in this study. Disc-shaped wax for 60 min followed by 100℃ for 30 min and then cooling for 120 patterns (10.0 mm in diameter and 2.5 mm thick) of CP titanium, min. All the specimens were immersed in water at 37℃ for 24 h. Ti-6Al-4V alloy (Kobesteel Co., Japan) were cast using a mag- nesia-based investment (Selevest CB, Selec Co., Japan) in an argon arc-centrifugal casting machine (Ticast Super R, Selec Co.) accord- ing to the manufacturer's instructions. For comparison, disc patterns (the same size as Ti-6Al-4V alloy) of a Co-Cr alloy (Biosil F, Degussa co., Ltd) were conventionally cast using a silica-based investment (Univest Silky, Shofu Dental Corp.) in a centrifugal induction melting machine (Neutrodyn Easyti, Manfred, Italy). Thirty cast discs were made for each alloy. After casting, the disk surfaces were finished with No. 600 silicon carbide paper under water followed by 250 μ m grain- sized aluminum oxide for 5 seconds using grit blaster (Micro sand blaster. Phoenix electric company Korea). The emis- sion pressure was 4.5 kgf/cm with the nozzle positioned approximately 5 mm from the surface of the metal adherent. Fig. 1. Metal conditioner were Fig. 2. Fabricated specimen. The grit-blasted cast disks were washed in acetone for 10 applied. Table I. Materials used for this Materials Identification Manufacturer Composition Metal CP titanium ASTM Grade II Kobe steel co., Ltd., Japan Ti > 99.0% Ti-6AL-4V ASTM Grade V Kobe steel co., Ltd., Japan Ti > 89.0%, 6.0% Al, 4.0% V Co-Cr alloy (Biosil F) Degussa co., Ltd., Germany Co 67%, Cr 28.5%, Mo 5.3% Primer Alloy primer Kuraray co., Ltd., Japan MDP, VBATDT MR Bond Tokuyama co., Ltd., Japan MAC-10 PMMA Vertex Vertex-Dental B.V. co., Netherland Methyl methacrylate MDP(10-methacryloyloxydecyl dehydrogen phosphate) MAC-10(11-methacryloyloxyundecan-1,1-decarboxylic acid) VABATDT(6-4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4 dithione) J Adv Prosthodont 2009;1:41-6 42 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al Measurement of shear bond strength the groups. Table IV shows the types of bond failure classified The shear bond strengths were measured using a screw-dri- as A or M for each group of specimens. Application of the ven universal testing machine (STM-5, United Calibration, USA) primers significantly (P < .05) improved the shear bond at a crosshead speed of 1.0 mm/min. The means and standard strengths of the heat cure resin to all metals (Table II, III). deviations (SD) of the shear bond strength (n = 5) were calculated The specimens primed with the Alloy primer showed a sig- and statistically analyzed with a 2-way analysis of variance nificantly higher bond strength (P < .05) than the specimens (ANOVA). primed with the MR bond on titanium. However, there was The factors for analysis were primer and metal. Then 2- no significant difference between the Alloy primer and MR way ANOVA, 1-way ANOVA and the Scheffe multiple com- bond on the Co-Cr alloy. parison test were performed at a significance level of α = .05. Mixed failure within the denture base resin was observed in After testing, the fracture surfaces of the specimens were the specimens primed with the Alloy primer . In addition, Mixed observed using an optical microscope (BX51 TRF, LYMPUS, failure and Adhesive failure were observed in the specimens JAPAN) at × 50 magnification to assess the type of bond fail- primed with the MR bond . Adhesive failure was observed in ure. The failure modes were categorized s either A (adhesive all control specimens (Table IV, Fig. 5). failure at the metal-PMMA interface) or M (mixed adhesive and cohesive failure). DISCUSSION RESULTS Titanium is a relatively new material in removable partial den- ture frameworks, and will most likely become more popular Fig. 4 and Table II shows the effect of the adhesive primers with the advancements in casting procedures and materi- on the shear bond strength of the heat cure resin to the cast tita- als. Since the introduction of the first fixed partial denture nium and cobalt-chromium alloy. Table III shows the means retained by implants, a type III gold alloy has been recom- and standard deviations (SD) of the shear bond strengths mended metal for the substructure because it is nontoxic, (MPa) of the 3 metals along with the statistical comparisons of no allergenic, corrosion resistant, easy to use, has adequate Fig. 3. Test configuration for debonding. Fig. 5. A: Adhesive failure at non-primed specimens. M: Mixed failure of adhesive and cohesive failures at Primed specimens. ×50: The fracture surface of the specimens were observed with and optical microscope. Table II. Shear bonding strength of three metal to two primer or non-primed of controls No primer MR bond Alloy primer Metal MPa SD MPa SD MPa SD Adhesive primer Co-Cr 3.4 0.6 17.8 4.0 17.1 2.6 CP Ti 2.4 0.3 5.9 2.1 15.9 2.5 Fig. 4. Shear bonding strength of three metal to two primer or Ti-6AI-4V 3.2 0.4 7.4 2.1 16.0 3.6 non-primed of controls. J Adv Prosthodont 2009;1:41-6 Bond Strength (MPa) Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al strength, and is relatively inexpensive. Commercially pure tita- decreased considerably after thermocycling. Jemt and Linden nium and Ti-6Al-4V alloy have similar desirable mechanical also showed that implant-supported prostheses with machined and physical properties. Clinical trials of titanium substructures titanium had bonding problems between the machined surface are underway to identify the variables that might negatively and the PMMA. Therefore, conventional bonding between an affect the life expectancy of an implant and the use of the pros- acrylic resin denture base and a titanium framework may theses. A failure of the bond at the PMMA-titanium interface not be sufficient to prevent microleakage. can result in prosthetic failure and create space between the met- The surface of pure titanium metal is usually coated with a al and PMMA, where oral debris, microorganism, and stains titanium oxide that is stable in an atmospheric environment. can accumulate. A poor bond between a titanium frame- This indicates that the primers actually adhere to titanium oxide work and PMMA can compromise the quality of the prosthesis rather than to pure titanium. Some metal oxides can react with and potentially place the patients at risk of an infection from carboxylic or phosphoric acid derivatives to form a chemical opportunistic microorganism. bond. In order to evaluate the value of commercially pure (CP) tita- Kojima et al. synthesized the 6-4-vinylbenzyl-n-propyl)amino- nium as a material for cast partial denture frameworks, 1,3,5-triazine-2,4-dithione monomer, which does not contain Yamauchi et al. examined the results of a follow-up examination a free mercapto group, and reported that the VBATDT primer of patients who had used titanium prosthesis. They report- improved the bond durability of an MMA-PMMA-TBBO ed that there were no clinical problems with cast CP titanium resin joined to precious metal alloys. However, VBATDT partial denture frameworks. However, there was some dye pen- was ineffective in increasing the bond strength of MMA-TBB etration from the finish line found despite the use of an adhe- resin to base metal dental casting alloys such as Co-Cr and nick- sive resin containing 4-META (META-DENT, Sun Medical, el-chromium. It was for this reason that MAC-10 (11- Kyoto, Japan) as a denture base resin. In a study of this phe- methacryloyloxyundecan-1,1-decarboxylic acid) and MDP nomenon, Matsumura et al. reported the bond strength of (10-methacryloyloxydecyl dehydrogen phosphate) were used 4-META containing an adhesive resin to pure titanium in this study. Regarding the bond strength, the use of any of the primers in previous studies would be acceptable for achieving clinically durable bonds to titanium frameworks. However, cast titanium frameworks, particularly CP titanium, are more flexible (low- er elastic modulus) than the Co-Cr alloy. Denture deflection during use can cause debonding between the denture base resin and the framework, and resulting eventually in resin fracture. Therefore, titanium frameworks should also be designed (and fabricated) to be hard enough so that denture deflection is kept to a minimum. It was for this reason that Ti-6AL-4V alloy ASTM Grade Ⅴ was used in this study. The aim of this study was to evaluate the shear bond Fig. 6. Chemical structure of MAC-10, MDP. strengths of a PMMA denture base resin to cast pure titanium, Table III. Summary of 2-way analysis of variance for shear bond strengths Source Degree of freedom Sum of square F-value P-value Metal 2 151,787 26,530 .000 Primer 2 1,070,802 187,161 .000 Metal*Primer 4 94,999 16,605 .000 Residual 63 5,721 Total 72 Table IV. Type of bond failure Primer METAL No primer MR.Bond Alloy primer Co-Cr AAAAAAAA AMMMMMMM AMMMMMMM Ti Gr II AAAAAAAA AAAAAMMM MMMMMMMM Ti 6AI 4V AAAAAAAA AAAAMMMM MMMMMMMM A: adhesive failure; M: adhesive + cohesive failure J Adv Prosthodont 2009;1:41-6 44 Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy Kim SS et al Ti-6Al-4V, and a cobalt-chromium alloy using two adhesive um and cobalt-chromium framework. CP titanium, Ti-6Al-4V, � � primers (MR bond : MAC-10, Alloy primer : MDP, VBATDT). or Co-Cr alloy discs were cast, and the bonding surfaces of the The difference in shear bond strengths of the primed and metal disk (10 mm diameter, 2.5 mm thick) were treated � � unprimed specimens was significant (P < .05) (Table III). with 2 different metal primers (MR bond , Alloy primer ). The May et al. suggested that the shear bond strength of heat- specimens without the primer were also prepared as the processed PMMA bonded to a machined surface of wrought control. CP titanium with 110 μ m alumina air abrasion and a silane coat- The shear bond strengths were determined at a crosshead ing was 63% higher than the specimens with no pretreat- speed of 1.0 mm/min. The application of any one of the two 21,22 ment. Other studies reported that the application of Rocatec primers tested, regardless of the brand used, significantly bonding material (ESPE GmbH, Seefeld/Oberbay, Germany) improved the shear bond strength of the denture base resin to increased the bond strength by 68% compared with the con- any of the cast metals tested (CP titanium, Ti-6Al-4V, and Co- trol. The application of heat-cured PMMA containing 4- Cr alloy). The specimens primed with the Alloy primer META (META-DENT) demonstrated a 3.7 fold higher bond showed higher bond strength than those primed with the strength than the control group. Shiragami et al. evaluated the MR bond on titanium. However, significant difference was not tensile bond strengths of a similar resin to cast Ti-6Al-4V observed on the Co-Cr alloy. Only adhesive failure was evident alloy with 3 adhesive primers. They used the original Metal at the metal-resin interface of all the non-primed specimens, Primer, Meta Base M, and Cesead Opaque Primer materials and while the primed specimens showed mixed failure of adhesive found greater bond strength than with the untreated specimens. and cohesive failure. In this study, the shear bond strength of heat cure denture With the use of appropriate adhesive metal primers, it is pos- base resin to a metal surface treated with an adhesive primer sible not only to eliminate the need for surface preparations of was greater than the specimens with no treatment. Therefore, the metal frameworks before the application of heat cure the two metal conditioners had a significant effect on the resins but also to reduce the need for retentive devices on the bond between the heat cure denture base resin and both metal substructure. alloys (Fig. 4 and Table II). While the shear bond strengths of In particular, the Alloy primer , which contains the phosphoric � � the Alloy primer were higher than those of the MR bond on acid monomer, MDP, is clinically more acceptable for bond- cast pure titanium, Ti-6Al-4V alloy, there was no significant dif- ing heat cure resin to titanium than the MR bond , which con- ference observed on the Co-Cr alloy. It is possible that the chem- tains the carboxylic acid monomer, MAC-10. ical bond of MDP to the titanium oxide is superior to that of MAC-10. Moreover, these results may be attributed to the dif- REFERENCES ferences in their composition, polymerization procedure or 1. Jacobson TE, Chang JC, Keri PP, Watanabe LG. Bond strength of mechanical properties. However, further research will be 4-META acrylic resin dentrue base to cobalt chromium alloy. J needed to answer this question. Prosthet Dent 1988;60:570-6. 2. Jacobson TE. The significance of adhesive denture base resin. 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Journal

The Journal of Advanced Prosthodontics – Pubmed Central

Published: Mar 31, 2009

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