Surface characterization of precious alloys treated with thione metal primers

doi:10.1016/j.dental.2006.06.007

Dental Materials

Volume 23, Issue 6, June 2007, Pages 665-673

https://doi.org/10.1016/j.dental.2006.06.007 Get rights and content

Abstract

Objectives

To characterize the effect of two thione metal primers with phosphate groups on the surface morphology and composition of two noble prosthodontic alloys.

Methods

Cast specimens from Argen 81(Au–Pd) and Argipal (Hi–Pd) alloys which were ground, polished and ultrasonicated in water, were divided in two groups (2 × 3) and treated with single layers of Alloy Primer (AP) and Metal Primer II (MP) primers respectively. The treated alloy surfaces were washed off with acetone and then examined by polarized light microscopy (PLM), reflection FTIR microspectroscopy (FTIRM) and X-ray photoelectron spectroscopy (XPS).

Results

After AP treatment, PLM revealed a crystalline phase (VBATDT) dispersed in an amorphous phase (MDP plus soluble VBATDT) on both the alloys tested. MP demonstrated a fibrial arrangement with the most dense structure found on the Hi–Pd alloy. FTIRM failed to clearly resolve the presence of single bond SH peaks on alloy surfaces. Moreover, NH and P double bond S peaks were identified denoting the presence of original thione tautomers. In both primers, phosphates were detected in a dissociative state (PO₃²⁻). FTIR molecular mapping confirmed separation of VBATDT from MDP and MEPS from residual MMA. XPS showed that on alloy surfaces approximately 50% of sulphur was in the sulphide state, the rest being organic sulphur. AP showed higher sulphide percentage than MP on both alloys and higher sulphide percentage on the Au–Pd alloy (p < 0.05).

Clinical significance

Phase separation of the primer components on alloy surfaces may adversely affect their clinical performance. Sulphide formation on alloy surfaces was confirmed only by XPS under ultra-high vacuum and not by environmental techniques like FTIR; this poses serious questions on the chemical bonding capacity of these primers with the noble alloys tested under environmental conditions.

Introduction

Bonding of resin-composites to metallic frameworks is of paramount importance for the strength, sealing capacity and durability of modern resin veneered restorations. The same requirements exist also for cementation of cast restorations with resin luting cements and for repair of fractured ceramic, composite or acrylic veneers with exposed metal surfaces.

Adhesive bonding to base metal alloys has been substantially improved by either direct use of carboxylic and phosphoric acid functionaliszed monomers on alloy surfaces [1], [2], [3], [4] or application of elaborate laboratory techniques for alloy surface modification, in combination with silane-coupling agents [5], [6], [7]. For noble metal alloys, the absence of a well defined passive oxide surface film has diminished the effectiveness of adhesive monomers [8], limiting thus a reliable solution to surface modification techniques [9], [10], [11]. Nevertheless, during the late 1980s, an alternative approach was introduced by Kojima et al. [12], who synthesized 6-(4-vinylbenzyl-n-propyl) amino-1,3,5-triazine-2,4-dithione (VBATDT), a thione–thiol tautomer, to be used as a coupling agent between methacrylate-based monomers and noble metal alloys (Fig. 1). The coupling mechanism of this monomer has been assigned to (i) transformation of thione ( single bond C double bond S) to thiol (CSH) groups on noble metal surface (M) and subsequently primary bond formation (CSM) and (ii) copolymerization of vinyl groups with the methacrylate-based resin monomer. The choice of the thione tautomer increased the self-life of the coupling agent and minimized thiol interferences with resin polymerization, since thiol-induced chain transfer reactions during the propagation stage could affect the final conversion in the polymer network [13]. Surface-enhanced Raman scattering spectroscopic analysis (SERS) confirmed thione to thiol transformation of VBATDT in an aqueous colloidal gold solution, but failed to confirm the existence of a primary bond [14]. The only evidence of chemical bond formation between a thiol monomer and a noble metal was presented in an early study by Kojima [15], who employed X-ray photoelectron spectroscopy (XPS) to investigate the bonding status between N-(4-mercaptophenyl) methacrylamide and palladium surface.

Currently, a variety of vinyl–thione coupling agents, known as precious metal primers, have become commercially available. The efficiency of these primers has been documented by a series of in vitro bond strength tests, including prolonged storage and hydrothermal aging [13], [16], [17], [18], [19], [20], [21]. Some of these primers contain phosphate co-monomers or thiophosphate groups possibly to provide a synergistic effect by bonding to the base metal components of the alloys [13]. The exact bonding mechanism of these primers with alloy surfaces has not yet been verified.

The aim of the present study was to characterize the effect of two precious metal primers containing thione and phosphate groups on the surface morphology and composition of two representative noble prosthodontic alloys. The null hypothesis tested was that there was no difference in the bonding mechanisms existing between each of the primer and alloy combinations investigated.

Section snippets

Materials and methods

The metal primers and prosthodontic alloys investigated are listed in Table 1 and the chemical structures of the monomers in Fig. 1. Six disk-shaped specimens, 7 mm in diameter and 2 mm in thickness, were cast from each alloy. The casts were ground to 1200 grit size SiC papers, polished with 0.5 μm Al₂O₃ suspension in a grinding/polishing machine (Ecomet III, Buhler, Lake Bluff, ILL, USA) and then cleaned in a water ultrasound bath. No air-abrasion was performed to avoid surface roughness and

Results

Fig. 2(a and b) demonstrates representative reflection polarized light images of the primers on the alloy surfaces tested. AP showed two distinct phases; an amorphous phase forming a continuous thin film, incorporating islands of a crystalline aggregated phase. No differences in the AP adsorbed film pattern were observed between the alloys tested. MP presented a completely different pattern; a diffuse and dense fibril arrangement was found on the Au–Pd alloy, whereas on the Hi–Pd alloy the

Discussion

The results of the present study lead to acceptance of the null hypothesis. This followed since the XPS, directly probing the chemical bond between the primers and alloy surfaces, showed that eventually the same bonding mechanism existed between all the primers and alloys tested. Nevertheless, between different alloy surfaces important morphological and compositional variations were documented. FTIR mapping clearly showed the presence of VBATDT in the amorphous AP film phase along with MDP,

Acknowledgement

This study was supported by the research grant ELKE 70/4/5768 from the University of Athens.

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Which metal surface treatment improves the bond strength between metal alloys and acrylic resin in removable partial dentures? A systematic review
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The union of the metal removable partial denture framework to the heat polymerized acrylic resin is related to prosthesis longevity. However, methods to enhance this bond are not clear to clinicians and dental laboratory technicians.
The purpose of this systematic review was to identify which metal surface treatments best increase the bond strength between heat polymerized acrylic resin and removable partial denture alloys.
This review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in the International Prospective Registry of Systematic Reviews (PROSPERO) database (CRD42022384926). Electronic searches were carried out independently, by 3 examiners in Medline/PubMed, Scopus, and Web of Science databases, and in the nonpeer-reviewed literature via ProQuest.
The electronic searches resulted in 4143 articles, with 4055 after removing duplicates. After reading the titles and abstracts, 37 articles were selected for reading in full-text version, from which 6 articles were included. All studies evaluated materials for conventional acrylic resin denture base (heat polymerized), processed by water bath, bonded to metal. For the metal framework alloys, cobalt chromium (Co-Cr) alloys were used in 2 studies, titanium (Ti) in 2 studies, and Co-Cr and Ti in the other 2 studies. Different metal surface treatments were used as airborne-particle abrasion with aluminum oxide (particle sizes of 50 µm, 110 µm, and 250 µm) followed by the primer application and the isolated use of the primer, compared to the absence of isolated intervention or airborne-particle abrasion of the metal surface. Among the different primers used, those based on 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) showed the highest acrylic resin-to-metal bond strength values.
Airborne-particle abrading the metal with Al₂O₃ followed by applying a 10-MDP-based primer, increased the bond strength between metal framework alloys and heat polymerized acrylic resin denture base material.
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Thereafter, Kojima et al. obtained a patent for several monomers, including 10-methacryloyloxydecyl-6,8-dithiooctanoate (10-MDDT) [3]. The performances of primers containing VBATDT or 6-methacryloyloxyhexyl 2-thiouracil 5-carboxylate (MTU-6) have been investigated in relation to facilitating the bonding of elemental noble metals [4] or of noble alloys [5–9], the characteristics of their bonds to these metals have been analyzed [10–14], and the clinical effectiveness of their use in facilitating bonds to dental noble metal alloys has been reported [15,16]. Synthesis of a sulfur-containing functional monomer, 10-methacryloyloxydecyl-(2-thiohydantoin-4-yl)propionate (MDTHP), was thereafter reported [17].
The purpose of this study was to assess the effects of an experimental primer containing acetone solution and a sulfur-containing functional monomer, 10-methacryloyloxydecyl-(2-thiohydantoin-4-yl)propionate (MDTHP), on the bonds between noble metals and acrylic resin.
The experimental primer used as the control for comparison consisted of 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithione (VBATDT) in acetone. These primers were prepared as equimolar functional monomers (0.1 mol%). A self-polymerizing acrylic resin initiated with tri-n-butylborane (TBB) was used as the luting agent. Four elemental metal disks (silver, copper, palladium, and gold) were used as adherend specimens. All the disks were wet-ground with silicon carbide paper (#1500). Bonding reactions were performed on 12 combinations of the four metals, and the disks were either primed with MDTHP or VBATDT or were unprimed (control). Shear bond strengths were determined pre- and post-thermocycling (5–55 °C, dwell time 60 s, 20,000 cycles). The results were statistically analyzed via a non-parametric test (α = 0.05).
The post-thermocycling shear bond strengths of the MDTHP primer were as follows (median, n = 11): 13.2 MPa on silver, 25.9 MPa on copper, 4.1 MPa on palladium, and 11.3 MPa on gold. The MDTHP primer showed higher post-thermocycling shear bond strength on all the four metals. Additionally, on silver and copper, the MDTHP bond strengths were higher than on the other metals.
Within the limitation of current of experimental setting, the MDTHP compound may be applicable as a functional monomer for bonding noble metal alloys.
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Novel tetrazinan-thione compounds including 6-hexyl-1,2,4,5-tetrazinan-3-thione (HTT), 6-propyl-1,2,4,5-tetrazinan-3-thione (PrTT) and 6-phenyl-1,2,4,5-tetrazinan-3-thione (PhTT) were synthesized and originally introduced as collectors for beneficiation of copper oxide mineral. The micro-flotation investigations exhibited that HTT achieved higher malachite recovery with better flotation selectivity against calcite than octyl hydroxamic acid (OHA). The three tetrazinan-thione surfactants significantly improved the hydrophobicity of malachite surfaces as followed: HTT > PhTT > PrTT, matching well with their hydrophobic-hydrophilic index LogP value, as well as their flotation response to malachite. In-situ AFM images clearly presented that HTT firmly covered on malachite surfaces. Zeta potential suggested the chemisorption of malachite towards HTT. FTIR and XPS offered additional evidences that malachite chemisorbed HTT on to its surfaces where the CuS and CuN bonds were generated. The heptyl group possesses stronger hydrophobic than the hexyl group, while, HTT exhibited better hydrophobization towards malachite than OHA, which might be attributed to their different bonding mode on malachite surfaces.
Peel strength and interfacial characterization of maxillofacial silicone elastomers bonded to titanium
2016, Dental Materials
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The primer was not separately cured to allow for copolymerization with the vinyl groups of the elastomers. This applies for most metal primers, even for these used for low-reactive noble alloys [23]. Nevertheless, the σ0 values were the lowest recorded for both the elastomers.
To investigate the effect of three adhesive primers on the morphology, chemistry and peel bond strength of two maxillofacial silicone elastomers with commercially pure titanium (cpTi).
The effect of three primers (PR2:A-304 Primer/A-320 Bonding Enhancer, PR3:Super Bond, and PR4:Super Glue) on cpTi morphology and chemistry were studied by reflected light polarized microscopy (RPOLM) and reflection Fourier-transform infrared microspectroscopy (RFTIRM). For testing the bond strength between two elastomers (EL1:MDX4-4210, EL2:A-2006) and primed cpTi surfaces, a 90° T peel test was performed (PBS), using as reference EL1, EL2 specimens bonded to heat-cured poly(methyl methacrylate) resin (PMMA) primed with A-330G primer (PR1). Failure modes were analyzed under a stereomicroscope, and the percentage of remaining silicone (RS%) on cpTi and PMMA were calculated by image analysis. Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDX) was used to investigate representative failure patterns on cpTi. Data were analyzed with Weibull analysis, ANOVA plus post hoc tests, and Pearson correlation coefficient (a = 0.05).
Thick-irregular (PR2), thin-smooth (PR3), and uniform-porous (PR4) films were identified on cpTi by RPOLM. RFTIRM revealed: a strong peak of Si–O–Si with a distribution following the outline of the image (PR2); COO-M groups developed, but unevenly distributed (PR3); and reduction in CC groups due to in situ polymerization (PR4). Following PBS, the ranking of the statistical significant differences in Weibull scale parameter (σ₀) of the EL1 group was PMMA_PR1 > cpTi_PR2,cpTi_PR3 > cpTi_PR4, whereas for the EL2 group cpTi_PR2 > PMMA_PR1 > cpTi_PR4,cpTi_PR3. For RS%, the ranking in the EL1 group was: PMMA_PR1 > cpTi_PR2 > cpTi_PR3 > cpTi_PR4, and in the EL2 cpTi_PR2 > cpTi_PR3 > cpTi_PR4,PMMA_PR1. There was no statistically significant correlation between PBS and RS%, with the exception of EL1_PMMA_PR1. In all groups mixed failure modes were found by SEM/EDX.
Although there is evidence of bonding with cpTi, there are important differences among the primer/elastomer combination that may affect the clinical performance of these materials.
Functionalized polyacrylamide by xanthate for Cr (VI) removal from aqueous solution
2016, Chemical Engineering Journal
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There were some new adsorption peaks in MPAM. The peak at 2550 cm−1 could be attributed to stretching vibration of SH group [31,35,36], while that at 877 cm−1 was likely generated by deformation [37]. Those new peaks at 675 cm−1, 453 cm−1 and 1005 cm−1 could be assigned to the stretching vibration of and CS groups [38–40].
Hexavalent chromium [Cr (VI)] has long been considered as a highly toxic substance that will impact water quality. In this study, a modified polyacrylamide (MPAM) was prepared by grafting a xanthate group onto polyacrylamide (PAM), which was characterized by the Fourier transform infrared (FT-IR) spectrum, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry (EDS). The performance of the new metal chelating agent, MPAM, was assessed by measuring Cr (VI) removal efficiency from an aqueous environment. FT-IR spectroscopy demonstrated that the MPAM is a xanthate functionalized PAM with functional groups of
. MPAM is a crystal material, and its main phase is similar to Na₂CO₃·!H₂O, which was not significantly changed in the chelation process. However, there was a significant increase in the intensity of the phase, which was possibly attributed to an increase in the size of ligand group. EDS results demonstrated that the chelation product was the result of a complex MPAM formation process, and Cr. MPAM had better yields with CS₂/NaOH molar ratio of 1:3 during the preparation. Cr (VI) removal efficiency increased with the increase of MPAM dosage. With an appropriate dosage, aqueous Cr (VI) could be almost completely removed. An acidic environment was conducive to Cr (VI) removal with better removal efficiency achieved at pH 5. Further illustration indicated that with 4.7 mg/L of MPAM dosage for treatment of solution containing 10 mg/L Cr (VI), a Cr (VI) removal efficiency of over 98% could be achieved. The presence of the cations, such as K⁺, Na⁺, and Ca²⁺ had an inhibiting effect on Cr (VI) removal; thus, there was a need to use a higher MPAM dosage. Overall, the functionalized polyacrylamide exhibited good Cr (VI) removal efficiency from aqueous solution with tested Cr (VI) concentrations.
In vitro shear bond strength of Y-TZP ceramics to different core materials with the use of three primer/resin cement systems
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The use of 10-methacryloyloxydecyldihydrogenphosphate (MDP) monomer following preparation of the surface of Y-TZP ceramics by using airborne-particle abrasion has been reported to produce favorable bond strength.7,13,18,27,45,46 As mentioned earlier, the MDP monomer can bond directly to the metallic oxides through a reaction between its hydroxyl groups and the hydroxyl groups on the surface of the zirconia ceramics.45,47-49 There was controversy in regard to the ability of MDP-containing systems to maintain a stable bond before and after aging in water and thermocycling of airborne-particle-abraded zirconia.14,50-53
Durability of the bond between different core materials and zirconia retainers is an important predictor of the success of a dental prosthesis. Nevertheless, because of its polycrystalline structure, zirconia cannot be etched and bonded to a conventional resin cement.
The purpose of this in vitro study was to compare the effects of 3 metal primer/resin cement systems on the shear bond strength (SBS) of 3 core materials bonded to yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic retainers.
Zirconia ceramic (Cercon) disks (5×3 mm) were airborne-particle abraded, rinsed, and air-dried. Disk-shaped core specimens (7×7 mm) that were prepared of composite resin, Ni-Cr, and zirconia were bonded to the zirconia ceramic disks by using one of 3 metal primer/cement systems: (Z-Prime Plus/BisCem, Zirconia Primer/Multilink Automix, or Clearfil Ceramic Primer/Clearfil SA). SBS was tested in a universal testing machine. Stereomicroscopy was used to evaluate the failure mode of debonded specimens. Data were analyzed using 2-way ANOVA and post hoc analysis using the Scheffe procedure (α=.05).
Clearfil SA/Clearfil Ceramic Primer system with an Ni-Cr core yielded the highest SBS value (19.03 MPa), whereas the lowest SBS value was obtained when Multilink Automix/Zirconia Primer system was used with the zirconia core group (4.09 MPa). Differences in mean SBS values among the cement/primer groups were statistically significant, except for Clearfil SA and BisCem with both composite resin and zirconia cores. Differences in mean SBS values among the core subgroups were not statistically significant, except for zirconia core with BisCem, Multilink, and Clearfil SA. The predominant failure mode was adhesive, except for Clearfil SA and BisCem luting agents with composite resin cores, which displayed cohesive failure, and Multilink Automix with a composite resin, core as well as Clearfil SA with Ni-Cr cores, where the debonded specimens of each group displayed a mixed (adhesive/cohesive) failure pattern.
Use of the Clearfil SA/Clearfil Ceramic Primer system, based on methacryloyloxydecyl dihydrogen phosphate (MDP), increased the bond strength of Y-TZP ceramics to core materials.

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Surface characterization of precious alloys treated with thione metal primers

Abstract

Objectives

Methods

Results

Clinical significance

Introduction

Section snippets

Materials and methods

Results

Discussion

Acknowledgement

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

Dent Mater

J Prosthet Dent

Biomaterials

J Prosthet Dent

J Prosthet Dent

J Prosthet Dent

J Dent

Dent Mater

4-META opaque resin-a new resin strongly adhesive to nickel-chromium alloy

J Dent Res