Production of polyimide ceria nanocomposites by development of molecular hook technology in nano-sonochemistry

Poly(amic acid), the precursor of polyimide (PI), was used for the preparation of PI/CeO₂ nanocomposites (NC)s by ultrasonic assisted technique via insertion of the surface modified CeO₂ nanoparticles (NP)s into PI matrix. In the preparation stages, in the first, the modifications of CeO₂ NPs by using hexadecyltrimethoxysilane (HDTMS) as a binder were targeted using ultrasonic waves. In the second step, newly designed PI structure was formed from the sonochemical imidization process as a molecular hook. In this step two different reactions were occurred. The acetic acid elimination reaction in the main chain of macromolecule, and the acetylation reaction in the side chains of poly(amic acid) were accomplished. By acetylation process the hook structure was created for trapping of the modified nanoparticles. In the final step the preparation of PI NCs were achieved by sonochemical process. The structural and thermal properties of pure PI and PI/CeO₂ NCs were studied by several techniques such as fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses. FT-IR and ¹H NMR spectra confirmed the success in preparation of PI matrix. The FE-SEM, TEM, and AFM analyses showed the uniform distribution of CeO₂ NPs in PI matrix. The XRD patterns of NCs show the presence of crystalline CeO₂ NPs in amorphous PI matrix. The thermal analysis results reveal that, with increases in the content of CeO₂ NPs in PI matrix, the thermally stability factors of samples were improved.

Effects of different surface treatments on the cyclic fatigue strength of one-piece CAD/CAM zirconia implants

OBJECTIVES

The effects of different surface treatments on cyclic fatigue strengths of computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia implants and its mechanisms were evaluated.

MATERIAL AND METHODS

One-piece cylindrical screw-type zirconia (Y-TZP) implants with diameters of 4.1-mm were fabricated using CAD/CAM technique; they were divided into four groups according to the type of surface treatment: (i) sintering (control group, CTRL), (ii) sandblasting (SB), (iii) sandblasting and etching with an experimental hot etching solution (SB-ST), and (iv) sandblasting and etching with hydrofluoric acid (SB-HF). The surface morphology and roughness of the implants were evaluated. Tetragonal to monoclinic transformation was measured on the surface by micro Raman spectroscopy. Static and fatigue tests were carried out at room temperature following the ISO 14801:2014 Standard. The cyclic fatigue strength of each group was determined using the staircase method. Specimens that survived the fatigue test were statically loaded to measure the residual fracture strength.

RESULTS

Among the four groups, SB-HF exhibited the highest surface roughness. Compared with the CTRL group, the surface monoclinic content was higher after all three types of surface treatments, amongst which, SB-HF had the highest content (39.14%), significantly more than the other three groups (P < 0.01). The cyclic fatigue strengths of CTRL, SB, SB-ST, and SB-HF implants were 530 N, 662.5 N, 705 N, and 555 N, respectively. The fracture strength after fatigue loading was higher than that before fatigue loading with no significant difference (P＞0.05).

CONCLUSIONS

SB and SB-ST remarkably enhanced the fatigue resistance of zirconia implants, while SB-HF did not. One-piece 4.1-mm diameter CAD/CAM zirconia implants have sufficient durability for application in dental implants.

Effect of Erbium-yttrium, scandium, gallium and garnet (Er-YSGG) laser on the bond strength of lithium disilicate ceramics

Objectives

To assess the bond strength of LD ceramics with resin composite material and surface conditioning using Er: YSGG laser and HF acid.

Methods

Thirty LD ceramic (Emax, Ivoclar vivadent) discs were prepared using hot pressing technique and treated with hydroflouric acid (Group-1-HF acid) (9%) (n=10) and Er- yttrium, scandium, gallium and garnet laser (Group-2-ER-YSGG laser) (Waterlase iPlus, 10 Hz and power of 0.5 W, pulse duration of 230 μs) (n=10). Ten specimens were left untreated to be included as controls (Group-3-Control). All the specimens were treated with Adper Single Bond adhesive (3MESPE, St. Paul, MN, USA). Multicore buildups (3mmx3mm) were performed using a rubber mold on the ceramic surfaces and cured using LED light-curing unit for 140 sec. All specimens were tested using shear bond test and failure modes were assessed with a stereomicroscope and scanning electron microscope. Data was analysed using ANOVA and Tukey Kramer multiple comparisons test.

Results

The maximum and minimum shear bond strength values were achieved in HF Acid specimens (Group-1) (28.15±4.72 MPa) and control specimens (13.47± 3.14 MPa) respectively. Specimens treated with HF acid showed significantly higher bond strength in comparison to laser treated and control specimens (p<0.01). Laser treated specimens had significantly higher bond strength as compared to controls (p<0.01).

Conclusions

Hydrofluoric (HF) acid treatment showed significantly better outcomes than YSGG laser surface treatment.

Surface modified SiO2 nanoparticles by thiamine and ultrasonication synthesis of PCL/SiO2-VB1 NCs: Morphology, thermal, mechanical and bioactivity investigations

The influence of silica (SiO₂) nanoparticles (NPs) on the properties of polycaprolactone (PCL) was investigated. Due to the intense tendency of SiO₂ NPs to aggregation and their high surface energy, the surface of SiO₂ NPs was treatment via Vitamin B₁ (VB₁) as a biosafe coupling agent. Novel PCL/SiO₂-VB₁ nanocomposites (NC) films by variety of percentage of SiO₂-VB₁ NPs were prepared under ultrasonic irradiation as an eco-friendly and fast procedure following by casting method. Fourier transform infrared spectroscopy and energy dispersive X-ray analysis exposed the presence of SiO₂ NPs into the polymer matrix. A good distribution of the silica into the polymer matrix was detected by microscopic observations and EDX testing. According to the UV-Vis spectra, the absorption of prepared NCs was improved via increasing the amount of SiO₂ NPs. PCL/SiO₂-VB₁ NCs showed more thermal stability compared to the pure polymer. The tensile test was investigated and good arrangement among the experimental data and the predicted flexibility of NCs was obtained. Moreover, PCL/SiO₂-VB₁ 6wt% had noticeable increase values for tensile strength. Finally, in vitro bioactivity investigation designated that by rising SiO₂ contents in the NCs, the amount of the hydroxyapatite formed was increased and NC films are bioactive and have a potential to be utilized in bone tissue engineering.

The effect of hydrofluoric acid concentration on the fatigue failure load of adhesively cemented feldspathic ceramic discs

OBJECTIVE

This study investigated the influence of hydrofluoric acid (HF) etching at different concentrations on the fatigue failure load of adhesively cemented feldspathic ceramic discs (Vita Mark II). Besides, their effect on the micromorphology of ceramic surface was investigated.

METHODS

Eighty ceramic discs (ϕ=10 mm; thickness=1.5 mm) were cemented to epoxy supporting discs (ϕ=10 mm; thickness=2.0mm) using different surface conditioning methods (n=20): nonetched control (CTRL), or etched for 60s with different HF concentrations: 1% (HF1), 5% (HF5), or 10% (HF10). All the ceramic discs received a silane application (Monobond Plus). The epoxy discs were etched with 10% HF for 60s and received a primer coating (Multilink Primer A+B). Adhesively cementation was performed (Multilink Automix), and the assemblies (ceramic discs/epoxy discs) were subjected to cyclic loads in water by a staircase approach (500,000 cycles; 20Hz; initial load=290N; step size=30N). Fatigue failure load data were analyzed using 1-way ANOVA and post-hoc Tukey's tests (α=.05).

RESULTS

Mean failure load of the HF5 group (255.0±23.0N) was significantly lower; HF1 group (301.7±71.0N) presented intermediate values, and the highest values were achieved in CTRL (351.7±13.4N) and HF10 (341.7±20.6N) groups. All the failures were radial cracks starting from the bonding surface.

SIGNIFICANCE

In terms of fatigue failure load, etching with 1% and 5% HF had a deleterious effect on the fatigue behavior of an adhesively cemented feldspathic ceramic, while 10% HF had no negative influence.

Effect of a calcium chloride solution treatment on physical and mechanical properties of glass ionomer cements

This paper details a novel method to improve wear resistance of dental glass ionomer cement (GIC) restorations. The purpose of this in vitro study was to evaluate the effect of a calcium chloride (CaCl₂) solution treatment on surface hardness, surface roughness, compressive strength, water sorption and solubility of three conventional glass ionomer cements (GICs). Additionally, the changes of the Ca composition and morphology of the surface of the tested GICs were also investigated. The experimental groups of the study were: Group 1 (control) specimens after mixing were left in the mold to set without any treatment for 5 min; Group 2 specimens were left in the mold to set for 5 min and then each specimen was immersed in 10 ml of 42.7 wt% CaCl₂ solution for 60 s. Statistical analysis was performed using one-way ANOVA and Tukey post hoc tests (a = 0.05). Calcium chloride solution treatment increased surface hardness of the GICs compared to control groups (P < 0.05), while surface roughness and compressive strength did not change after the treatment (P > 0.05). Reduction in water sorption and solubility was detected but not in all CaCl₂ solution-treatment groups. No alterations were observed in surface morphology of the GICs, while surface calcium composition was increased after the treatment (P < 0.05). The use of a CaCl₂ solution immediately after initial setting of GICs may be advantageous for some properties of the materials and possibly leads to improved prognosis and wear resistance of their restorations.

Intraoperative changes in corneal structure during excimer laser phototherapeutic keratectomy (PTK) assessed by intraoperative optical coherence tomography

PURPOSE

Excimer laser phototherapeutic keratectomy (PTK) is a safe treatment for superficial corneal opacities, e.g., in corneal dystrophies or degenerations. Nevertheless, no standardized treatment protocols are available and intraoperative monitoring was not possible, so far. Here we evaluate the potential benefits of the intraoperative assessment by microscope-integrated intraoperative optical coherence tomography (MI-OCT) of corneal optical properties during PTK.

METHODS

Retrospective study of eight patients (one male, seven females; age range, 43-80 years, mean = 66.1 years) using an 840-nm microscope-integrated spectral-domain OCT (iOCT; OptoMedical Technologies, Luebeck, Germany adapted to HS Hi-R Neo 900A, Haag Streit Surgical, Wedel, Germany). Images were acquired before and after corneal abrasion and after PTK. For PTK, a SCHWIND Amaris 750S excimer laser (SCHWIND eye-tech-solutions GmbH und KO. KG) was used. Parameters assessed were the central corneal thickness (CCT), changes in central depth-dependent corneal tissue intensity (TI), and corneal surface roughness (SR) in cross-sectional images of the cornea.

RESULTS

Intraoperative monitoring using microscope-integrated OCT was possible in all patients at all time points. TI of the anterior corneal stroma decreased significantly (p = 0.037) after PTK (T1 = 15.1 ± 3.6, T2 = 15.0 ± 3.84, T3 = 13.7 ± 3.38), but not after corneal abrasion alone, indicating increased transparency caused by excimer laser PTK. CCT was significantly lower after corneal abrasion (p = 0.017), but not after PTK (T1 = 630.4 ± 70 μm, T2 = 544.1 ± 59.4 μm, T3 = 558.3 ± 52.5 μm. SR significantly decreased (p = 0.043) after PTK (T1 = 614.4 ± 37.5 pixels, T2 = 634.4 ± 35.6 pixels, T3 = 611.0 ± 40.3 pixels).

CONCLUSIONS

Intraoperative OCT allows real-time imaging during PTK and the assessment of corneal optical transparency and its surface roughness. It has to be clarified in larger studies if these parameters correlate with later postoperative visual outcomes.

Ultrasonic assisted synthesis of nanocomposite materials based on resole resin and surface modified nano CeO2: Chemical and morphological aspects

In this study, phenol-formaldehyde (PF)/CeO₂ nanocomposites (NC)s were prepared by in-situ polymerization of phenol and formaldehyde in alkali solution in the presence of surface modified CeO₂ nanoparticles (NP)s by sonochemical assisted synthesis. The morphology and structure of PF/CeO₂ NCs were characterized by using fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses methods. It was found that due to the good dispersion of surface modified NPs in polymer matrix and the strong interfacial interaction between the CeO₂ NPs and PF matrix, the thermal stability and thermo-mechanical properties of the PF/CeO₂ NCs were greatly enhanced. FE-SEM and AFM analyses showed the uniform distribution of CeO₂ NPs in PF matrix. The XRD patterns of NCs show the presence of crystalline CeO₂ NPs in amorphous matrix. The thermal analysis results reveal that, with increases in the content of CeO₂ NPs in PF matrix, the thermally stability factors of samples were drastically enhanced.

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin.

Repair bond strengths of non-aged and aged resin nanoceramics

PURPOSE

To explore the influence of different surface conditionings on surface changes and the influence of surface treatments and aging on the bond strengths of composites to non-aged and aged resin nanoceramics.

MATERIALS AND METHODS

Rectangular-shaped non-aged and aged (5000 thermocycles) resin nanoceramic specimens (Lava Ultimate) (n=63, each) were divided into 3 groups according to surface treatments (untreated, air abrasion, or silica coating) (n=21). The surface roughness was measured and scanning electron microscopy was used to examine one specimen from each group. Afterwards, the specimens were repaired with a composite resin (Filtek Z550) and half were sent for aging (5000 thermocycles, n=10, each). Shear bond strengths and failure types were evaluated. Roughness and bond strength were investigated by two- and three-way analysis of variance, respectively. The correlation between the roughness and bond strength was investigated by Pearson's correlation test.

RESULTS

Surface-treated samples had higher roughness compared with the untreated specimens (P=.000). For the non-aged resin nanoceramic groups, aging was a significant factor for bond strength; for the aged resin nanoceramic groups, surface treatment and aging were significant factors. The failures were mostly adhesive after thermal cycling, except in the non-aged untreated group and the aged air-abraded group, which had mostly mixed failures. Roughness and bond strength were positively correlated (P=.003).

CONCLUSION

Surface treatment is not required for the repair of non-aged resin nanoceramic; for the repair of aged resin nanoceramic restorations, air abrasion is recommended.

Anodization of magnesium for biomedical applications - Processing, characterization, degradation and cytocompatibility

This article reports anodization of Mg in KOH electrolyte and the associated surface, degradation, and biological properties for bioresorbable implant applications. The preparation procedures for electrodes and anodization setup significantly enhanced reproducibility of samples. The results of anodization performed at the applied potentials of 1.8, 1.9, or 2.0V showed that the sample anodized at 1.9V and annealed, referred to as the 1.9 AA sample, had homogenous surface microstructure and elemental composition, and a reduction in corrosion current density in the electrochemical testing. In comparison with Mg control, the 1.9 AA sample showed a distinct mode of degradation, e.g., continuous growth of a passivation layer enriched with Ca and P instead of typical localized pitting and undermining, and a greater release rate of Mg²⁺ ions when immersed in physiologically relevant media. In the direct culture with bone marrow derived mesenchymal stem cells (BMSCs) in vitro, the 1.9 AA sample did not affect BMSC adhesion and morphology under indirect contact; however, the 1.9 AA sample showed a reduction in cell spreading under direct contact. The change in surface topography/composition at the dynamic interface of the anodized-annealed Mg sample might have contributed to the change in BMSC morphology. In summary, this study demonstrated the potential of anodic oxidation to modulate the degradation behaviors of Mg-based biomaterials and BMSC responses in vitro, and confirmed the value of direct culture method for studying cytocompatibility of Mg-based biomaterials for medical implant applications.

STATEMENT OF SIGNIFICANCE

Magnesium (Mg)-based biomaterials have been specifically designed and actively explored for biodegradable implant applications since the early 2000s. To realize the benefits of Mg-based materials for medical implant applications, it is critical to control the rate of Mg degradation (i.e. corrosion) in the body. We investigated an environmentally friendly anodization process using KOH electrolyte for modifying the surface of Mg-based materials, and the resulted surface, degradation, and biological properties for biomedical applications. This study reported critical considerations that are important for repeatability of anodization process, homogeneity of surface microstructure and composition, and in vitro evaluations of the degradation and biological properties of surface treated Mg samples. The details in preparation of electrodes, anodization setup, annealing, and sample handling before and after surface treatment (e.g. re-embedding) reported in this article are valuable for studying a variety of electrochemical processes for surface treatment of Mg-based metals, because of enhanced reproducibility.

Comparison of traditional and simplified methods for repairing CAD/CAM feldspathic ceramics

PURPOSE

To evaluate the adhesion to CAD/CAM feldspathic blocks by failure analysis and shear bond strength test (SBSt) of different restorative systems and different surface treatments, for purpose of moderate chipping repair.

MATERIALS AND METHODS

A self-adhering flowable composite (Vertise Flow, Kerr) containing bi-functional phosphate monomers and a conventional flowable resin composite (Premise Flow, Kerr) applied with and without adhesive system (Optibond Solo Plus, Kerr) were combined with three different surface treatments (Hydrofluoric Acid Etching, Sandblasting, combination of both) for repairing feldspathic ceramics. Two commercial systems for ceramic repairing were tested as controls (Porcelain Repair Kit, Ultradent, and CoJet System, 3M). SBSt was performed and failure mode was evaluated using a digital microscope. A One-Way ANOVA (Tukey test for post hoc) was applied to the SBSt data and the Fisher's Exact Test was applied to the failure analysis data.

RESULTS

The use of resin systems containing bi-functional phosphate monomers combined with hydrofluoric acid etching of the ceramic surface gave the highest values in terms of bond strength and of more favorable failure modalities.

CONCLUSION

The simplified repairing method based on self-adhering flowable resin combined with the use of hydrofluoric acid etching showed high bond strength values and a favorable failure mode. Repairing of ceramic chipping with a self-adhering flowable resin associated with hydrofluoric acid etching showed high bond strength with a less time consuming and technique-sensitive procedure compared to standard procedure.

SEM Evaluation of Enamel Surface Changes and Enamel Microhardness around Orthodontic Brackets after Application of CO2 Laser, Er,Cr:YSGG Laser and Fluoride Varnish: An In vivo Study

Introduction

One of the most undesirable consequences of orthodontic treatment is occurrence of enamel demineralization around orthodontic brackets. Numerous in vitro studies have reported the prevention of enamel demineralization by surface treatment with lasers and fluoride varnish.

Aim

To evaluate the changes on the enamel surface and microhardness around orthodontic brackets after surface treatment by CO₂ laser, Er, Cr:YSGG laser and fluoride varnish in vivo.

Materials and Methods

A double blind interventional study was carried out on 100 premolars which were equally divided into five groups, out of which one was the control group (Group 0). The intervention groups (Group I to IV) comprised of patients requiring fixed orthodontic treatment with all 4 first premolars extraction. Brackets were bonded on all 80 premolars which were to be extracted. Enamel surface treatment of Groups I, II and III was done by CO₂ laser, Er, Cr:YSGG laser and 5% sodium fluoride varnish respectively and Group IV did not receive any surface treatment. A modified T-loop was ligated to the bracket and after two months, the premolars were extracted. Surface changes were evaluated by Scanning Electron Microscopic (SEM) and microhardness testing. Comparison of mean microhardness between all the groups was assessed using post-hoc test with Bonferroni correction.

Results

Group I showed a melted enamel appearance with fine cracks and fissures while Group II showed a glossy, homogenous enamel surface with well coalesced enamel rods. Group III showed slight areas of erosions and Group IV presented areas of stripped enamel. Significant difference was observed between the mean microhardness (VHN) of Group I, Group II, Group III, Group IV and Group 0 with p<0.001. A significant difference of p<0.001 was observed while comparing Group I vs II,III,IV,0 and Group II vs III,IV,0. However, difference while comparing Group III vs IV was p=0.005 and difference between the mean microhardness of Group 0 vs Group III was non significant.

Conclusion

Surface treatment with Er,Cr:YSGG laser causes a positive alteration of the enamel surface increasing its ability to resist demineralization with optimum microhardness as compared to CO₂ laser and sodium fluoride varnish.

Surface treatment with Fenton for separation of acrylonitrile-butadiene-styrene and polyvinylchloride waste plastics by flotation

Surface treatment with Fenton was applied to flotation separation of acrylonitrile-butadienestyrene (ABS) and polyvinylchloride (PVC). After treatment, the floatability of ABS has a dramatic decrease, while the floatability of PVC is not affected. Fourier transform infrared spectroscopy (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) spectra were recorded to ascertain the mechanism of Fenton treatment. FT-IR and XPS analysis confirms that the introduction of oxygen-containing group occurs on the surface of ABS. The optimum conditions are molar ration (H₂O₂:Fe²⁺) 10000, H₂O₂ concentration 0.4M/L, pH 5.8, treatment time 2min and temperature 25°C, frother concentration 15mg/L and flotation time 3min. Particle sizes and mixing ratios were also investigated. Plastic mixtures of ABS and PVC with different particle sizes and mixing ratios can be effectively separated. The purity of ABS and PVC are up to 100% and 99.78%, respectively; the recovery of ABS and PVC are up to 99.89% and 100%, respectively. A practical, environmentally friendly and effective reagent, namely Fenton, was originally applied to surface treatment of ABS and PVC waste plastics for flotation separation of their mixtures.

Effect of surface treatment on the mechanical properties of nickel-titanium files with a similar cross-section

OBJECTIVES

The aim of this study was to compare the mechanical properties of various nickel-titanium (NiTi) files with similar tapers and cross-sectional areas depending on whether they were surface-treated.

MATERIALS AND METHODS

Three NiTi file systems with a similar convex triangular cross-section and the same ISO #25 tip size were selected for this study: G6 (G6), ProTaper Universal (PTU), and Dia-PT (DPT). To test torsional resistance, 5 mm of the straightened file's tip was fixed between polycarbonate blocks (n = 15/group) and continuous clockwise rotation until fracture was conducted using a customized device. To evaluate cyclic fatigue resistance, files were rotated in an artificial curved canal until fracture in a dynamic mode (n = 15/group). The torsional data were analyzed using 1-way analysis of variance and the Tukey post-hoc comparison test, while the cyclic fatigue data were analyzed using the Mann-Whitney U test at a significance level of 95%.

RESULTS

PTU showed significantly greater toughness, followed by DPT and G6 (p < 0.05). G6 showed the lowest resistance in ultimate torsional strength, while it showed a higher fracture angle than the other files (p < 0.05). In the cyclic fatigue test, DPT showed a significantly higher number of cycles to failure than PTU or G6 (p < 0.05).

CONCLUSIONS

Within the limitations of this study, it can be concluded that the torsional resistance of NiTi files was affected by the cross-sectional area, while the cyclic fatigue resistance of NiTi files was influenced by the surface treatment.

Effect of surface alkali-based treatment of titanium implants on ability to promote in vitro mineralization and in vivo bone formation

This study investigated whether a novel alkali-based surface modification enhances in vitro mineralization as well as in vivo bone formation around titanium (Ti) implants in a femoral condyle model of 36 male Wister rats. All implant surfaces were grit-blasted and then received either acid-etching treatment, alkali-based treatment, or were left untreated (controls). Histological and histomorphometrical analyses were performed on retrieved specimens after 4 and 8weeks of healing to assess peri-implant bone formation. Results of implants surface characterisation showed notable differences in the topography and composition of alkali-treated surfaces, reflecting the formation of submicron-structured alkali-titanate layer. In the in vitro test, alkali-treated Ti surfaces showed the ability to stimulate mineralization upon soaking in simulated body fluid (SBF). In vivo histomorphometrical analyses showed similar values for bone area (BA%) and bone-to-implant contact (BIC%) for all experimental groups after both 4- and 8-week implantation periods. In conclusion, the surface topography and composition of the grit-blasted Ti implants was significantly modified using alkali-based treatment. With respect to the present in vivo model, the biological performance of alkali-treated Ti implants is comparable to the commercially available, grit-blasted, acid-etched Ti implants.

STATEMENT OF SIGNIFICANCE

Since success rate of dental implants might be challenged in bone of low density, an optimum implant surface characteristic is demanding. In this work, alkali treatment of Ti implants showed significant advantage of surface mineralization upon soaking in simulated body fluid. Using an in vivo rat model, Ti surfaces with either acid-etching treatment or alkali-based treatment evoked robust bone formation around Ti implants. Such information may be utilized for the advancement of biomaterials research for bone implants in future.

A novel process for separation of polycarbonate, polyvinyl chloride and polymethyl methacrylate waste plastics by froth flotation

A novel process was proposed for separation of ternary waste plastics by froth flotation. Pretreatment of plastics with potassium permanganate (KMnO₄) solution was conducted to aid flotation separation of polycarbonate (PC), polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) plastics. The effect of pretreatment parameters including KMnO₄ concentration, treatment time, temperature and stirring rate on flotation recovery were investigated by single factor experiments. Surface treatment with KMnO₄ changes selectively the flotation behavior of PC, PVC and PMMA, enabling separation of the plastics by froth flotation. Mechanism of surface treatment was studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectrum (XPS). Effect of frother concentration and flotation time on flotation behavior of plastic mixtures was further studied for flotation separation. The optimized conditions for separation of PC are KMnO₄ concentration 2mmolL^-1, treatment time 10min, temperature 60°C, stirring rate 300rpm, flotation time 1min and frother concentration 17.5mgL^-1. Under optimum conditions, PVC and PMMA mixtures are also separated efficiently by froth flotation associated with KMnO₄ treatment. The purity of PC, PVC and PMMA is up to 100%, 98.41% and 98.68%, while the recovery reaches 96.82%, 98.71% and 98.38%, respectively. Economic analysis manifests remarkable profits of the developed process. Reusing KMnO₄ solution is feasible, enabling the process greener.

The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness

OBJECTIVE

Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness.

METHODS

Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: R_a, R_sk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics K_I test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone.

RESULTS

G2 and G4 specimens showed very similar, and high R_a values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (K_IC). Weibull's analysis showed G2 (SIE) tendency to exhibit higher K_IC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens.

SIGNIFICANCE

Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (K_IC) values with higher K_IC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups.

Self-etching ceramic primer versus hydrofluoric acid etching: Etching efficacy and bonding performance

AIM

This study assessed the effect of pretreatment of hybrid and glass ceramics using a self-etching primer on the shear bond strength (SBS) and surface topography, in comparison to pretreatment with hydrofluoric acid and silane.

METHODS

40 rectangular discs from each ceramic material (IPS e.max CAD;EM, Vita Mark II;VM, Vita Enamic;VE), were equally divided (n=10) and assigned to one of four surface pretreatment methods; etching with 4.8% hydrofluoric acid followed by Monobond plus (HFMP), Monobond etch & prime (Ivoclar Vivadent) (MEP), No treatment (NT) as negative control and Monobond plus (Ivoclar Vivadent) with no etching (MP) as positive control. SBS of resin cement (Multilink-N, Ivoclar Vivadent) to ceramic surfaces was tested following a standard protocol. Surface roughness was evaluated using an Atomic force microscope (AFM). Surface topography and elemental analysis were analyzed using SEM/EDX. Data were analyzed with two-way analysis of variance (ANOVA) and post-hoc Bonferroni test at a significance level of α=0.05.

RESULTS

Pretreatment with HFMP resulted in higher SBS and increased surface roughness in comparison to MEP and MP. Regardless the method of surface pretreatment, the mean SBS values of EM ceramic was significantly higher (p<0.05) than those recorded for VM and VE, except when VE was treated with MEP, where the difference was statistically insignificant. Traces of fluoride ion were detected when MEP was used with VE and VM.

CONCLUSION

Under limited conditions, using MEP resulted in comparable SBS results to HFMP; meanwhile HFMP remains the gold standard for pretreatment of glass ceramics for resin-luting cementation.

Evaluation of the permeation of antineoplastic agents through medical gloves of varying materials and thickness and with varying surface treatments

BACKGROUND

Medical gloves are an important piece of personal protective equipment that prevents exposure to antineoplastic agents. The permeability of medical gloves to antineoplastic agents is a crucial factor in the appropriate selection of gloves. However, the relationship between glove permeability and material type, thickness, and surface treatment is poorly understood.

METHODS

A continuous flow in-line cell device was used for the evaluation of the permeation of five antineoplastic agents (etoposide, cyclophosphamide, doxorubicin hydrochloride, paclitaxel, and fluorouracil) through medical gloves. Medical gloves made of three types of materials (chlorinated latex, non-chlorinated latex, and nitrile) were subjected to a permeability test. The antineoplastic agents in test solutions were tested at the highest concentrations employed in general clinical practice. Then, the relationship between glove thickness and permeability was assessed using chlorinated latex gloves with thicknesses of 0.1, 0.15, 0.2, and 0.1 mm × 2 (to represent the practice of "double gloving").

RESULTS

Only cyclophosphamide and fluorouracil showed detectable permeation through the tested latex gloves. The permeability of chlorinated latex was lower than that of non-chlorinated latex. Nitrile gloves showed no detectable permeability to any of the five antineoplastic agents tested. The permeability of chlorinated latex gloves depended on the thickness of the gloves; 0.1 mm × 2 (double gloving) exhibited the highest resistance to permeation by antineoplastic agents.

CONCLUSIONS

The permeability of medical gloves was dependent on the type of material and the surface treatment and decreased as the thickness of the glove increased. The double glove was shown to prevent antineoplastic agent permeation more efficiently than did a single glove of the same total thickness. These results provided important information that will guide the appropriate selection of medical gloves.

Effect of zirconia surface treatment using nitric acid-hydrofluoric acid on the shear bond strengths of resin cements

PURPOSE

The aim of this study was to compare the surface roughness of zirconia when using Zircos E etching system (ZSAT), applying a nitric acid-hydrofluoric acid compound as a pretreatment agent, and also to compare the shear bonding strength according to different resin cements.

MATERIALS AND METHODS

ZSAT, air abrasion, and tribochemical silicacoating were applied on prepared 120 zirconia specimens (10 mm in diameter, 7 mm in height) using CAD/CAM. Each 12 specimens with 4 different resin cements (Panavia F 2.0, Rely X Unicem, Superbond C&B, and Hot bond) were applied to test interfacial bond strength. The statistical analysis was performed using SAS 9.1 (SAS Institute Inc., Cary, NC, USA). The results are as follows: after application of the ZSAT on the zirconia specimens, surface roughness value after 2-hour etching was higher than those after 1- and 3-hour etching on SEM images.

RESULTS

For Superbond C&B and Rely X Unicem, the specimens treated with ZSAT showed higher shear bond strength values than those treated with air abrasion and tribochemical silicacoating system. Regarding the failure mode of interface over cement and zirconia surface, Rely X Unicem and Hot bond showed cohesive failures and Panavia F 2.0 and Superbond C&B showed mixed failures.

CONCLUSION

Zircos E etching system in zirconia restoration could increase its shear bond strength. However, its long term success rate and clinical application should be further evaluated.

Bond Strength of Repaired Acrylic Denture Teeth Using Visible Light Cure Composite Resin

Background:

Although bonding to denture teeth after surface treatment with chemical agents is desirable, there is little information on the use of Visible Light Cure composite resin (VLC) as bonding denture materials.

Objectives:

To determine the effect of various surface treatments on shear bond strength between Visible Light Cure composite resin and the acrylic denture teeth interface.

Methods:

Forty cylindrical sticks of acrylic resin with denture teeth mounted atop were prepared. Various treatments were implemented upon the acrylic resin teeth surfaces. The samples were divided into four groups (n = 10). Light-cured composite resin (LC) was applied over all treated and untreated surfaces of tested groups. The shear bond was tested using a universal tensile testing apparatus with the knife-edge of a 0.8mm shear tester. Data were statistically analyzed using one-way ANOVA performed at a confidence level of 95% and significant P-value of (P ≤ 0.05).

Results:

Analysis of variance (ANOVA) showed statistically significant difference (P < 0.05) between treated and untreated teeth surfaces. The treated surfaces exhibited various levels of bond strength depending on the type of treatment.

Conclusion:

Application of VLC bonding agent with prior treatment of methylmethacrylate (MMA) on the acrylic resin denture teeth resulted in maximum bond strength with composite resin.

The effects of water on degradation of the zirconia-resin bond

OBJECTIVES

10-methacryloyloxydecyldihydrogenphosphate (MDP) containing primers improve bonding of yttria-stabilised tetragonal zirconia (Y-TZP) to methacrylate resins. The present study investigated the role played by water in the deterioration of MDP-mediated zirconia-resin bonds.

METHODS

Grit-blasted Y-TZP plates were conditioned with two MDP primers and bonded with resin for shear bond strength (SBS) testing. Additional bonded plates were aged hydrothermally and compared with unaged Y-TZP after 24h of water-storage or 6 months of water/acid/alkali-storage. The monoclinic phase (m-ZrO₂) in different groups was determined by X-ray diffraction. Hydrolytic stability of the coordinate bond between MDP and zirconia in neutral/acid/alkaline environment was analysed using thermodynamic calculations. Microleakage and release of the element phosphorus from MDP-mediated Y-TZP/resin-bonded interfaces were evaluated via methylene blue dye infiltration and inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTS

Hydrothermal ageing did not significantly alter SBS. Ageing in acidic or neutral medium led to significant decline in SBS. The m-ZrO₂ phase increased after hydrothermal ageing but no m-ZrO₂ was detected in the water/acid/alkali-aged specimens. A higher equilibrium constant was identified in the MDP-t-ZrO₂ complex when compared with the MDP-m-ZrO₂ complex. MDP-conditioning failed to prevent infiltration of the methylene blue dye. Phosphorus was detected by ICP-MS from the solutions used for soaking the resin-bonded specimens.

CONCLUSIONS

Hydrolysis of the coordinate bond between MDP and ZrO₂, rather than t→m phase transformation, weakens the bond integrity between MDP-conditioned Y-TZP and methacrylate resin.

CLINICAL SIGNIFICANCE

Hydrolysis of the coordinate bond between MDP and zirconia is responsible for deterioration of the integrity of the bond between MDP-conditioned Y-TZP and methacrylate resin.

The effects of non-thermal plasma and conventional treatments on the bond strength of fiber posts to resin cement

Objectives

This study compared the effect of hexamethyldisiloxane (HMDSO) and ammonia (NH₃) plasmas on the bond strength of resin cement to fiber posts with conventional treatments.

Materials and Methods

Sixty-five fiber posts were divided into 5 groups: Control (no surface treatment); H₂O₂ (24% hydrogen peroxide for 1 min); Blasting (blasting with aluminum oxide for 30 sec); NH₃ (NH₃ plasma treatment for 3 min); HMDSO (HMDSO plasma treatment for 15 min). After the treatments, the Ambar adhesive (FGM Dental Products) was applied to the post surface (n = 10). The fiber post was inserted into a silicon matrix that was filled with the conventional resin cement Allcem Core (FGM). Afterwards, the post/cement specimens were cut into discs and subjected to a push-out bond strength (POBS) test. Additionally, 3 posts in each group were evaluated using scanning electron microscopy. The POBS data were analyzed by one-way analysis of variance and the Tukey's honest significant difference post hoc test (α = 0.05).

Results

The Blasting and NH₃ groups showed the highest POBS values. The HMDSO group showed intermediate POBS values, whereas the Control and H₂O₂ groups showed the lowest POBS values.

Conclusion

Blasting and NH₃ plasma treatments were associated with stronger bonding of the conventional resin cement Allcem to fiber posts, in a procedure in which the Ambar adhesive was used.

Microtensile bond strength of repaired indirect resin composite

PURPOSE

The objective of this study was to investigate the effect of surface treatments on microtensile bond strengths (MTBSs) of two types of indirect resin composites bonded to a conventional direct resin composite.

MATERIALS AND METHODS

Indirect resin composite blocks of Ceramage and SR Nexco were prepared in a plastic mold having a dimension of 10 × 10 × 4 mm. These composite blocks were divided into three groups according to their surface treatments: Group1: Sandblast (SB); Group2: Sandblast and ultrasonically clean (SB+UL); Group3: Sandblast plus silane (SB+SI). After bonding with direct resin composite, indirect-direct resin composite blocks were kept in distilled water for 24 hours at 37℃ and cut into microbars with the dimension of 1 × 1 × 8 mm. Microbar specimens (n = 40 per group) were loaded using a universal testing machine. Failure modes and compositions were evaluated by SEM. The statistical analyses of MTBS were performed by two-way ANOVA and Dunnett's test at α = .05.

RESULTS

Surface treatments and brands had effects on the MTBS without an interaction between these two factors. For SR Nexco, the MTBSs of SB and SB+SI group were significantly higher than that of SB+UL. For Ceramage, the MTBSs of SB and SB+SI were significantly higher than that of SB+UL. The mean MTBS of the Ceramage specimens was significantly higher than that of SR Nexco for all surface treatments.

CONCLUSION

Sandblasting with or without silane application could improve the bond strengths of repaired indirect resin composites to a conventional direct resin composite.