Adhesion of adhesive resin to dental precious metal alloys. Part II. The relationship between surface structure of Au-In alloys and adhesive ability with 4-META resin

In vitro evaluation of NaOCl-mediated functionalization of biologically aged titanium surfaces

The aim of this study was to evaluate the NaOCl-mediated biofunctionalization of titanium surfaces. Titanium disks stored for 2 weeks were immersed in 5% NaOCl solution for 24 h. A disk immersed in distilled water for 24 h was used as a control. X-ray photoelectron spectrometer assay of the titanium surface after NaOCl treatment demonstrated that organic contaminants containing carbon and nitrogen were removed and the number of hydroxyl groups increased. The NaOCl treatment substantially converted the titanium surface to superhydrophilic status (θ<5°), which resulted in an increased number of attached cells and enhanced cell spreading on the NaOCl-treated surfaces. These results indicate that biofunctionalization of the biologically degraded titanium surfaces can be achieved by chemical surface treatment with 5% NaOCl. The mechanism for desorption of strongly adsorbed organic molecules with polar groups such as amino and aldehyde groups from titanium surfaces by ClO^- was elucidated.

Effect of different pH environments on the durability of bonds between zirconia and Ti-6Al-4V

This study investigated the role played by different pH environments in the deterioration of bonds between Y-TZP and Ti-6Al-4V. One hundred and thirty-five specimens were randomly assigned to one of the following storage media at 37°C: (1) distilled water, pH 6.9, DW; (2) acidic solution, pH 1-2, CS; and (3) alkaline solution, pH 10-11, KS. Shear bond strength (SBS) tests were carried out at the 4-, 14-, and 30-day storage time intervals. The morphology characteristics and elements distribution of the fracture surfaces were analyzed. CS-30 showed the lowest mean SBS and the least amount of residual cement on the Ti-6Al-4V surface after the SBS tests. Bond strength tended to decrease with increasing storage time for the acidic group. Alkaline and neutral media showed little influence on the SBS of Y-TZP to Ti-6Al-4V in 30 days. Acidic environments should be properly avoided to obtain reliable long-term bonding strength between Ti-6Al-4V and Y-TZP.

Peel strength and interfacial characterization of maxillofacial silicone elastomers bonded to titanium

OBJECTIVES

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).

METHODS

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).

RESULTS

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.

SIGNIFICANCE

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.

The effects of different wavelength UV photofunctionalization on micro-arc oxidized titanium

Many challenges exist in improving early osseointegration, one of the most critical factors in the long-term clinical success of dental implants. Recently, ultraviolet (UV) light-mediated photofunctionalization of titanium as a new potential surface treatment has aroused great interest. This study examines the bioactivity of titanium surfaces treated with UV light of different wavelengths and the underlying associated mechanism. Micro-arc oxidation (MAO) titanium samples were pretreated with UVA light (peak wavelength of 360 nm) or UVC light (peak wavelength of 250 nm) for up to 24 h. UVC treatment promoted the attachment, spread, proliferation and differentiation of MG-63 osteoblast-like cells on the titanium surface, as well as the capacity for apatite formation in simulated body fluid (SBF). These biological influences were not observed after UVA treatment, apart from a weaker effect on apatite formation. The enhanced bioactivity was substantially correlated with the amount of Ti-OH groups, which play an important role in improving the hydrophilicity, along with the removal of hydrocarbons on the titanium surface. Our results showed that both UVA and UVC irradiation altered the chemical properties of the titanium surface without sacrificing its excellent physical characteristics, suggesting that this technology has extensive potential applications and merits further investigation.

Tensile bond strength of dual curing resin-based cements to commercially pure titanium

OBJECTIVES

The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer.

METHODS

One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine.

RESULTS

The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h.

SIGNIFICANCE

Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.

Surface characterization of precious alloys treated with thione metal primers

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 x 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 SH peaks on alloy surfaces. Moreover, NH and PS peaks were identified denoting the presence of original thione tautomers. In both primers, phosphates were detected in a dissociative state (-PO(3)(2-)). 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.