Influence of surface treatments on the surface properties of different zirconia cores and adhesion of zirconia-veneering ceramic systems

Objective

The aim of this study was to assess the influence of surface treatments on the surface characteristics of different zirconia cores and the adhesion of the zirconia-veneering ceramic systems by means of strain energy release rate (G-value, J/m²).

Methods

Three types of zirconia cores (NANOZR (NZ), Vita In-Ceram YZ (VZ), and IPS e.max ZirCAD (IZ)) were used. The specimens were divided into four groups in each test according to the surface treatment used; Gr 1 (control; no treatment), Gr 2 (sandblasted), Gr 3 (CH₂Cl₂ for 60 min), and Gr 4 (experimental hot etching solution for 60 min). AFM, SEM, EDS, and XRD were carried out. Two types of veneering ceramics (Vita VM9 (V9) and IPS e.max Ceram (IC)) were used for testing the adhesion. The G-value (J/m²) was measured with a four-point bending configuration. Following fracture testing specimens were examined with SEM. Data were analyzed using ANOVA and Tukey's test.

Results

NZ treated with the experimental hot etching solution showed the highest R_a values (206.06 ± 9.98 nm) compared with the other groups (P < 0.05). The greatest amount of monoclinic phase is measured after sandblasting (19.59%) for NZ, followed by VZ (9.3%) and IZ (6.6%). The NZ/V9 (etching for 60 min) group showed the highest G-value (36.02 ± 2.80 J/m²) among the groups. Mode of failure was mostly cohesive failure within all the bonded veneering ceramic systems.

Significance

The experimental hot etching solution could be considered as alternative treatment modality to sandblasting for zirconia cores to avoid phase transition at the surface from tetragonal to monoclinic that may be detrimental for the longevity of the zirconia-veneering ceramic restoration.     

Effect of pretreatments on the metal–ceramic bonding strength of a Pd–Ag alloy

Objectives

The purpose of this study was to evaluate the efficacy of surface treatments on the bonding properties between a metal and ceramic.

Methods

Sixty metal specimens were divided equally into four groups of 15 samples each. These groups received different treatments (Gr1: 250 μm Al₂O₃ + preoxidation; Gr2: 250 μm Al₂O₃ + degassing; Gr3: 120 μm Al₂O₃ + preoxidation; Gr4: 120 μm Al₂O₃ + degassing). Bond strengths were evaluated using a three-point bending test. The results were analyzed using 2-way ANOVA and Tukey's test. Scanning electron microscopy and energy dispersive spectroscopy were used to observe the microscopic features, elemental compositions and distributions, and diffusion in the specimens. Mechanical profiler was used to measure the roughness of metal surface.

Results

The bond strengths of the four groups ranged from 45.00 ± 3.63 MPa to 51.61 ± 5.91 MPa, with significant differences (P < .05). The specimen that received the pretreatment of 250 μm Al₂O₃ air-particle abrasion + degassing had the highest bond strength. Heating under different oxygen partial pressures caused the final Pd–Ag alloys to have varying degrees of internal oxidation and different quantities of metallic nodules. None of the elements in either the ceramic or the Pd–Ag alloy layer diffused into the other layer.

Conclusions

The metal–ceramic specimen subjected to air-particle abrasion with 250 μm Al₂O₃ and degassed before porcelain firing had significantly higher bond strength than specimens treated differently.     

Stress-relieving and porcelain firing cycle influence on marginal fit of commercially pure titanium and titanium-aluminum-vanadium copings.

OBJECTIVES: This study evaluated: (1) the marginal fit of copings fabricated from commercially pure titanium (cp Ti) and titanium-aluminum-vanadium alloy (Ti-6Al-4V) after each firing cycle for a recommended porcelain; and (2) the effectiveness of a stress-relieving treatment on the fit. The results were compared with copings made with Pd-Ag alloy submitted to the recommended porcelain firing protocol. METHODS: Bovine teeth were machined for metal-ceramic crowns and die casts were obtained for waxing patterns. The firing cycle of titanium porcelain was performed on cp Ti and Ti-6Al-4V copings obtained using the Rematitan System. A stress-relieving treatment (cp Ti treated and Ti-6Al-4V treated groups) was performed on original invested castings at the first porcelain firing temperature (800 degrees C). Fit (microm) was measured in the 'as cast' condition and after each porcelain firing cycle with a traveling microscope. The values were compared using the analysis of variance and Tukey's test (P<0.05), the Pd-Ag group was compared to titanium groups using Dunnett's test (P<0.05). RESULTS: The marginal fit values in the as-cast condition (initial) were 84.43 microm for Ti-6Al-4V not treated, 76.35 microm for Ti-6Al-4V treated, 86.09 microm for cp Ti not treated, 97.66 microm for cp Ti treated and 58.11 microm for Pd-Ag group. The Ti-6Al-4V, cp Ti, and Pd-Ag groups exhibit significant differences in marginal fit values when the as-cast condition (initial) was compared with those after the recommended porcelain firing protocol (by Tukey's test at 5% probability level). No significant differences were observed between stress-relieving treated and not treated groups.Significance. The firing cycles used for porcelain build-up may worsen the fit of titanium copings to values that suggest no inferences to the detriment of clinical applications.     

Bleaching effectiveness,hydrogen peroxide diffusion,and cytotoxicity of a chemically activated bleaching gel

Objectives

The objective of this study was to evaluate the bleaching effectiveness, hydrogen peroxide diffusion (H₂O₂), and cytotoxicity of a bleaching gel with 35 % H₂O₂ either associated with ferrous sulfate (FeSO₄) or not.

Materials and methods

Enamel/dentin discs adapted to artificial pulp chambers were placed in compartments containing a culture medium (Dulbecco's Modified Eagle's Medium (DMEM)) and distributed into the following groups: G1—no treatment (negative control), G2—10 % carbamide peroxide (one application for 4 h), G3—35 % H₂O₂ (three applications for 15 min), and G4—35 % H₂O₂ + 0.004 g FeSO₄ (three applications for 15 min). After treatments, the extracts (DMEM + bleaching components that diffused across enamel and dentin) were applied on human dental pulp cells (HDPCs) and odontoblast-like cells (MDPC-23). Cell viability (MTT assay, Kruskal–Wallis and Mann–Whitney, α?=?5 %), quantification of H₂O₂ diffusion, and color change of the enamel/dentin discs (Commission Internationale de I'Eclairage L*a*b* system) were assessed (analysis of variance and Tukey's tests, α?=?5 %).

Results

For both cells, a significant reduction in cell viability was observed for G3 and G4 compared with G1 and G2. No statistical difference was observed between G3 and G4. The rate of H₂O₂ diffusion was significantly higher in G3 compared with that in G2 and G4. The ΔE value for G4 was statistically higher than that of the other groups.

Conclusions

Chemical activation of H₂O₂ by FeSO₄ improves the bleaching effectiveness. However, this metal ion has no significant protective effect against pulp cell cytotoxicity.

Clinical relevance

Although the chemical activation of H₂O₂ by adding FeSO₄ to the bleaching agent improved the bleaching effectiveness, this metal ion has no significant protective effect against pulp cell cytotoxicity.     

Wear performance of substructure ceramics and veneering porcelains

Aim

The aim of this in vitro study was to compare the two-body wear resistance of substructure zirconia and veneering porcelain versus steatite and human enamel antagonists, respectively.

Materials and methods

Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists (enamel cusps). A pin-on-block design with a vertical load of 50 N for 1.2 × 10⁵ cycles; (f = 1.6 Hz; lateral movement: 1 mm, mouth opening: 2 mm) was used for the wear test. For quantification of the wear resistance, wear tests were performed with standardized steatite spheres. Human enamel was used as a reference. Five zirconia ceramics and four veneering porcelains were investigated. One zirconia ceramic was tested with superficial glaze, which was applied after polishing or sandblasting, respectively. Surface roughness R_a (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D-Profilometer (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures were used for evaluating wear performance of both, ceramics and antagonists.

Results

No wear was found for zirconia substructures. Veneering porcelain provided wear traces between 186.1 ± 33.2 μm and 232.9 ± 66.9 μm (steatite antagonist) and 90.6 ± 3.5 μm and 123.9 ± 50.7 μm (enamel). Wear of the steatite antagonists varied between 0.812 ± 0.256 mm² and 1.360 ± 0.321 mm² for zirconia and 1.708 ± 0.275 mm² and 2.568 ± 0.827 mm² for porcelain. Enamel generally showed wear, cracks or even fractures at the ridge, regardless whether opposed by zirconia or porcelain/glaze. Enamel was polished, when opposed to zirconia, or plowed, provoked and grinded, when opposed to porcelain/glaze.

Conclusion

The results of the wear test with steatite or enamel antagonists indicated no measurable wear on zirconia surfaces. Porcelain showed higher wear than zirconia, but comparable or lower wear than an enamel reference. Antagonistic wear against zirconia was found to be lower than wear against porcelain.     

Hydrogen Peroxide Induces Apoptosis in Human Dental Pulp Cells via Caspase-9 Dependent Pathway

Introduction

Reactive oxygen species are a group of metabolic intermediates produced during oxidative metabolism in eukaryotic cells. They include superoxide anion (O₂⁻), hydrogen peroxide (H₂O₂), hydroxyl radical (·OH), and ¹O₂. Of these intermediates, H₂O₂ is the most stable. Dental pulp cells can be invaded by tooth bleaching, laser radiation, and dental materials. This can influence the intracellular level of reactive oxygen species. Apoptosis, which is the best-known form of programmed cell death, is pivotal to tissue development and regeneration. Little information is available regarding the relationship between H₂O₂ and apoptosis of human dental pulp cells (hDPCs). The purpose of this study was to investigate whether H₂O₂ can induce apoptosis in hDPCs and its signaling way.

Methods

HDPCs were obtained by using a modified tissue explant technique in vitro and cultured at 37°C, 20% O₂ (5% CO₂, 95% air) in Dulbecco modified Eagle medium. Cell viability was investigated by methyl-thiazol-tetrazolium assay. Cell apoptosis was detected by using the annexin V–fluorescein isothiocyanate/propidium iodide apoptosis assay and flow cytometry. Expression of activated caspase-3, cleaved caspase-9, and β-actin was analyzed by using Western blot.

Results

Cell viability of hDPCs decreased more in treated groups than in the control group from days 1 to 7. The relative number of apoptotic cells and the expression of activated caspase-3 and cleaved caspase-9 were much higher in groups exposed to 20 and 50 μmol/L H₂O₂.

Conclusions

These results imply that low concentrations of H₂O₂ are cytotoxic to hDPCs and induce apoptosis in hDPCs in a caspase-9–dependent way.     

Bioactive polyphenol antioxidants protect oral fibroblasts from ROS-inducing agents

Background

Oxidative damage to soft oral tissues may result from exposure to the chemicals or biochemicals found in teeth-whitening products, dental restorations, tobacco, and alcohol. Our working hypothesis is that oral tissues are susceptible to the toxic effects of stressors such as hydrogen peroxide (H₂O₂), ethanol (EtOH) and nicotine (Nic), which decrease cell viability/DNA synthesis and elevate reactive oxygen species (ROS). In this study, we investigated specific polyphenols and turmeric derivative antioxidants (AO) in combinations that counteracted the effects of these stressors on cultured oral fibroblast proliferation and ROS production.

Methods

Oral fibroblasts were exposed to stressors for 30 min and then treated with 10⁻⁵ M of bioactive AO mixtures [resveratrol, ferulic acid and tetrahydrocurcuminoid (RFT), phloretin, ferulic acid and resveratrol (PFR), phloretin, ferulic acid and tetrahydrocurcuminoid (PFT)] for 24 h. Cell viability and DNA synthesis were monitored using incorporated 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulphophenyl]-2H-tetrazolium (MTS) and 5-bromo-2-deoxyuridine (BrdU) assays, respectively. Total ROS was measured with dichlorodihydrofluorescein diacetate (H₂DCFDA).

Results

Incubation of oral fibroblasts in the stressors for 30 min resulted in a dose-dependent decrease of DNA synthesis and number of viable cells, and an increased total ROS activity. AO treatment counteracted the insults by restoring DNA synthesis levels and cell viability, and decreasing the total ROS activity.

Conclusion

The AO combinations of RFT, PFR and PFT protected the oral fibroblasts from the detrimental effects of H₂O₂, EtOH and Nic by decreasing total ROS and increasing cell viability and DNA synthesis.     

Effects of tooth whitening and orange juice on surface properties of dental enamel

Objective

To study the effects of 6% H₂O₂ activated with LED light on surface enamel as compared to orange juice challenges in vitro.

Methods

A total of 40 human enamel discs were incubated in saliva overnight to allow pellicle formation and then divided into three groups: 15 for whitening treatments, 15 for orange juice immersions and 10 for normal saline controls. Baseline microhardness was measured with a microhardness Knoop indenter (50 g, 10 s) and surface topography was evaluated with a focus-variation 3D scanning microscopy. Enamel discs were treated with H₂O₂ or orange juice for 20 min each cycle for five cycles to simulate daily treatment with the products for 5 days. The discs were stored in saliva between treatment cycles. Microhardness and surface topography were evaluated again after treatments. Changes in microhardness and in surface area roughness (Sa), mean maximum peak-to-valley distance (Sz) and the developed surface area ratio (Sdr) were compared before and after treatments (t-test) and among groups (ANOVA).

Results

Enamel surface hardness decreased by 84% after orange juice immersion but no statistically significant changes were observed in the whitening and control groups. Surface topography changed significantly only in the orange juice group as shown by increased Sa (1.2 μm vs. 2.0 μm), Sz (7.7 μm vs. 10.2 μm) and Sdr (2.8% vs. 6.0%). No such changes were observed in the whitening and control groups.

Conclusion

In comparison to orange juice challenges, the effects of 6% H₂O₂ on surface enamel are insignificant. Orange juice erosion markedly decreased hardness and increased roughness of enamel.     

Human gingival fibroblasts function is stimulated on machined hydrided titanium zirconium dental implants

Objectives

The aim of this study was to evaluate the influence of different titanium zirconium (TiZr) alloy surfaces on primary human gingival fibroblasts (HGF) for improved soft tissue integration of dental implants.

Methods

TiZr polished, machined and machined + HCl/H₂SO₄ acid-etched surfaces were modified by cathodic polarization and/or HNO₃/HF acid etching. Contact angle of surfaces was measured. The influence of modified TiZr surfaces on HGF was evaluated through the analysis of cell number, morphology, recovery after a wound (wound healing assay) and the expression of several genes, including matrix metalloproteinase-1 (MMP1) and metallopeptidase inhibitor-1 (TIMP1).

Results

Modification of TiZr surfaces decreased its hydrophilicity. Hydride implementation on TiZr surfaces via cathodic polarization increased TIMP1 expression and decreased MMP1/TIMP1 mRNA ratio. Cathodic polarization of machined surfaces promoted cell attachment. Cells on machined and machined + cathodic polarization surfaces grew aligned to the microgrooves whereas on all polished surfaces they grew randomly. Acid etching of polished and machined surfaces did not improve HGF function.

Conclusions

Hydride implementation on TiZr machined surfaces may be used as new dental implant material for improved soft tissue integration.

Clinical significance

Enhancing dental implant surfaces’ bioactivity by hydride implementation may promote soft tissue attachment and sealing around the implant and reduce peri-implantitis related to ECM-destruction compared with conventional machined surfaces.     

Weibull analysis of bond strength of orthodontic buccal tubes bonded to resin composite surface with various techniques

The objective of this study was to analyze the survival probabilities of various surface preparation techniques for bonding buccal tubes on resin composite surface. Resin composite specimens (hybrid), 33 per group were prepared. 8 experimental groups were (1) sandblast 90 μm; (2) sandblast 50 μm; (3) abrasion using diamond bur; (4) hydrofluoric acid etching for 1 min (HF 1 min); (5) HF 2 min; (6) HF 3 min; (7) 37% orthophosphoric etching for 10 min (H₃PO₄ 10 min) and (8) control (unetched surface). Plastic conditioner was applied then buccal tubes were bonded. Shear bond strength was tested with the universal testing machine and the Weibull analysis was performed. The results at a stress level of 7.8 MPa and 10 MPa, revealed the probabilities of survival for sandblast 50 μm (100%, 99.9%), sandblast 90 μm (99.7%, 98.7%), diamond bur (98.3%, 93.4%), HF 2 min (95.9%, 85.3%), HF 1 min (78.3%, 61.4%), HF 3 min (70.6%, 46.3%), H₃PO₄ 10 min (61.4%, 44.5%) and control (26.3%, 6.9%), respectively. Therefore, surface preparation by sandblast (50 μm and 90 μm), or diamond bur followed by plastic conditioner were highly effective for bonding orthodontic buccal tubes on hybrid resin composite surface. HF 2 min was acceptable. However, HF 1 min, 3 min, H₃PO₄ etching and unetched surface could not achieve adequate bond survival.     

Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Objectives

Sn²⁺ has promising erosion-inhibiting properties in solutions, but little is known about respective effects in toothpastes. In addition, biopolymers might have protecting potential. Aim of this study was to investigate the effects of Sn²⁺ in toothpastes and of a biopolymer (chitosan) added to a Sn²⁺ formulation on erosion/abrasion.

Methods

Enamel samples were subjected to cyclic erosion procedures (10 days; 0.50% citric acid, pH 2.5; 6× 2 min/day), and brushing (2× 15 s/day, load 200 g) during immersion in slurries (2 min). The toothpastes were NaF formulations (NaF/1, NaF/2, NaF/3) and Sn²⁺ formulations (NaF/SnCl₂, AmF/SnF₂, AmF/NaF/SnCl₂) and AmF/NaF/SnCl₂ + 0.5% chitosan.Declared concentrations of active ingredients in toothpastes were 1400–1450 μg/g F⁻ and 3280–3500 μg/g Sn²⁺. Negative controls were erosion only and placebo, positive control was a SnF₂ gel. Tissue loss was quantified profilometrically, Sn on enamel surfaces was measured by energy dispersive X-ray spectroscopy.

Results

Loss values (μm) for erosion only and placebo were 14.4 ± 4.5 and 20.2 ± 3.8, respectively, and 4.6 ± 1.9 for the positive control (p ≤ 0.001 each compared to erosion only). The other loss values were: NaF/1 16.5 ± 3.0, NaF/2 14.0 ± 2.7, NaF/3 12.6 ± 3.9, NaF/SnCl₂ 14.7 ± 5.1, AmF/SnF₂ 13.5 ± 4.8, AmF/NaF/SnCl₂ 12.4 ± 4.2, AmF/NaF/SnCl₂ + chitosan 6.6 ± 3.5 (except NaF/1 all p ≤ 0.01 compared to placebo). AmF/NaF/SnCl₂/chitosan was more effective than all other toothpastes (p ≤ 0.01 each). Sn on the enamel surface ranged between 1.3 ± 0.3 and 2.8 ± 0.04 wt.% with no obvious relationship with efficacy.

Conclusions

The NaF and Sn²⁺ toothpastes without chitosan exhibited similar anti-erosion and abrasion-prevention effects. The experimental Sn²⁺ formulation with chitosan revealed promising results similar to those of the positive control.

Clinical significance

NaF toothpastes offer a degree of protection against erosion/abrasion, which is likely sufficient for most subjects with average acid exposures. For patients with initial erosive lesions, however, more effective toothpaste is desirable. The combination of Sn²⁺ and a biopolymer appears promising in this context.     

Surface treatment of feldspathic porcelain: scanning electron microscopy analysis

PURPOSE

Topographic analysis of treated ceramics provides qualitative information regarding the surface texture affecting the micromechanical retention and locking of resin-ceramics. This study aims to compare the surface microstructure following different surface treatments of feldspathic porcelain.

MATERIALS AND METHODS

This in-vitro study was conducted on 72 porcelain discs randomly divided into 12 groups (n=6). In 9 groups, feldspathic surfaces were subjected to sandblasting at 2, 3 or 4 bar pressure for 5, 10 or 15 seconds with 50 µm alumina particles at a 5 mm distance. In group 10, 9.5% hydrofluoric acid (HF) gel was applied for 120 seconds. In group 11, specimens were sandblasted at 3 bar pressure for 10 seconds and then conditioned with HF. In group 12, specimens were first treated with HF and then sandblasted at 3 bar pressure for 10 seconds. All specimens were then evaluated under scanning electron microscopy (SEM) at different magnifications.

RESULTS

SEM images of HF treated specimens revealed deep porosities of variable sizes; whereas, the sandblasted surfaces were more homogenous and had sharper peaks. Increasing the pressure and duration of sandblasting increased the surface roughness. SEM images of the two combined techniques showed that in group 11 (sandblasted first), HF caused deeper porosities; whereas in group 12 (treated with HF first) sandblasting caused irregularities with less homogeneity.

CONCLUSION

All surface treatments increased the surface area and caused porous surfaces. In groups subjected to HF, the porosities were deeper than those in sandblasted only groups.     

The effect of long-term use of tooth bleaching products on the human enamel surface

The aim of this in vitro study was to evaluate the long-term effect of bleaching on human enamel. Four groups of enamel specimens were prepared (n = 20): group 1: bleaching with Opalescence Boost [40% hydrogen peroxide (H₂O₂), 3 × 20 min/week]; group 2: control group (the specimens were stored in human saliva); group 3: beaching with Vivastyle Paint on Plus (6% H₂O₂, 2 × 10 min/day), and group 4: bleaching with Opalescence PF 16% [16% carbamide peroxide (CP), 6 h/day]. After each bleaching session the specimens were stored in human saliva. Knoop microhardness and surface roughness were measured: before bleaching, after 2-week and after 8-week bleaching. After 2-week treatment, surface roughness was significantly increased in all experimental groups (p < 0.05), while among them no significant difference was found (p > 0.05). The roughness changes exerted after 8-week bleaching were not significantly higher than the ones after 2 weeks (p > 0.05). After 8-week treatment, the increase in roughness caused by 16% CP was significantly higher (p < 0.05) than the one caused by 40% H₂O₂. Microhardness increased in all groups including control; however, only 40% H₂O₂ increased the microhardness significantly (p < 0.05). The effect of bleaching on enamel was not shown to be dependent on the method or the H₂O₂ concentration. Bleaching with CP 16% resulted in higher roughness than bleaching with H₂O₂, while 40% H₂O₂ caused the higher microhardness increase. The present study showed that in-office bleaching with 40% H₂O₂ seems to be at least as safe as home bleaching as far as their effects on human enamel are concerned.     

Concentrations of and application protocols for hydrogen peroxide bleaching gels: Effects on pulp cell viability and whitening efficacy

Objectives

To assess the whitening effectiveness and the trans-enamel/trans-dentinal toxicity of experimental tooth-bleaching protocols on pulp cells.

Methods

Enamel/dentine discs individually adapted to trans-well devices were placed on cultured odontoblast-like cells (MDPC-23) or human dental pulp cells (HDPCs). The following groups were formed: G1 – no treatment (control); G2 to G4 – 35% H₂O₂, 3 × 15, 1 × 15, and 1 × 5 min, respectively; and G5 to G7 – 17.5% H₂O₂, 3 × 15, 1 × 15, and 1 × 5 min, respectively. Cell viability and morphology were evaluated immediately after bleaching (T1) and 72 h thereafter (T2). Oxidative stress and cell membrane damage were also assessed (T1). The amount of H₂O₂ in culture medium was quantified (Mann–Whitney; α = 5%) and colour change (ΔE) of enamel was analysed after 3 sessions (Tukey's test; α = 5%).

Results

Cell viability reduction, H₂O₂ diffusion, cell morphology alteration, oxidative stress, and cell membrane damage occurred in a concentration-/time-dependent fashion. The cell viability reduction was significant in all groups for HDPCs and only for G2, G3, and G5 in MDPC-23 cells compared with G1. Significant cell viability and morphology recovery were observed in all groups at T2, except for G2 in HDPCs. The highest ΔE value was found in G2. However, all groups presented significant ΔE increases compared with G1.

Conclusion

Shortening the contact time of a 35%-H₂O₂ gel for 5 min, or reducing its concentration to 17.5% and applying it for 45, 15, or 5 min produce gradual tooth colour change associated with reduced trans-enamel and trans-dentinal cytotoxicity to pulp cells.

Clinical significance

The experimental protocols tested in the present study provided significant tooth-bleaching improvement associated with decreased toxicity to pulp cells, which may be an interesting alternative to be tested in clinical situations intended to reduce tooth sensitivity and pulp damage.     

Effect acidic and alkaline/heat treatments on the bond strength of different luting cements to commercially pure titanium

Objective

The purpose of this study was to characterize the effects of either acidic or combined alkaline/heat treatments on the surface of grit-blasted commercially pure (cp) titanium. The effects of the previous treatments on the shear bond strength (SBS) of cp titanium to conventional glass ionomer, resin-reinforced glass ionomer and self-adhesive resin luting cements were evaluated.

Methods

Titanium discs were machined and received one of the following treatments; grit-blasting (GB), grit-blasting followed either by etching in HNO₃/HF solution (GB/Ac) or by combined 5 M NaOH treatment/heat treatment at 600 °C for 1 h, then immersed for 24 h in SBF solution before cementation (GB/Ak). The treated surfaces were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and laser-induced brake-down spectroscopy (LIBS). Discs were cemented either by Fuji I, Fuji Plus or Rely X™ Unicem luting cements. The SBS was evaluated and the debonded discs were investigated by SEM.

Results

Two prominent results were revealed; first, GB/Ak treatment showed the highest SBS than the other treatments (P < 0.0001). Second, Rely X™ Unicem showed the highest SBS than the other cements (P < 0.0001). Fuji I and Fuji Plus showed predominant cohesive type of failure, whereas Rely X™ showed predominant adhesive type of failure.

Significance

Combined alkaline/heat treatments of commercially pure titanium surface shows to be of beneficial effect in enhancing SBS to glass ionomer, resin-modified glass ionomer and adhesive resin luting cements.     

Optimisation of the hydrogen peroxide pre‐treatment of titanium: surface characterisation and protein adsorption

Background: Researchers have attempted to enhance titanium osseointegration by modifying its surface properties, including via H₂O₂ pre‐treatment, with reported treatment regimes varying from minutes/hours, to weeks. Objective: This study examined the effects of various H₂O₂ treatments on titanium surface topography/roughness, chemical composition/oxide thickness, hydrophilicity and plasma protein adsorption. Materials and methods: Titanium discs were treated with 30% H₂O₂ for 0–24 h or 1–4 weeks and subjected to atomic force microscopy (AFM), scanning electron microscopy (SEM), profilometry, X‐ray photon spectroscopy and contact angle analysis. For protein adsorption, whole plasma and FITC‐conjugated serum albumin were added to 0–24 h and
1–4 week H₂O₂‐treated discs and examined by SEM and fluorescence microscopy, respectively. Results: AFM, SEM and profilometry demonstrated that 1–6 h H₂O₂‐treated discs exhibited subtle alterations in surface topography/roughness at the nanometre scale, although 24 h and 1–4 week H₂O₂‐treated discs exhibited much greater increases in surface roughness, in the micrometre range. Maximal increases in surface oxide thickness and chemical modification were identified between 1 h–4 weeks and 3 h–4 weeks, respectively, although no increases in oxygen/titanium (O1s : Ti2p) molar ratio or in hydrophilicity were evident. Plasma and serum albumin adsorption increased on 1–24 h H₂O₂‐treated discs, with further increases on 1–4 week H₂O₂‐treated discs. Conclusions: Based upon the present data and previous findings, this study supports the concept that surface topography/roughness and oxide composition/thickness, are more significantly modified by H₂O₂ treatment and more influential to protein adsorption than hydrophilicity. Additionally, it can be hypothesized that the 24 h H₂O₂ treatment of titanium surfaces, which induced micrometre scale changes in roughness and protein adsorption, to those associated with enhanced osteoblast attachment/behaviour, mineralisation and subsequent implant osseointegration, would be most beneficial.     

Six-month evaluation of adhesives interface created by a hydrophobic adhesive to acid-etched ethanol-wet bonded dentine with simplified dehydration protocols

Objectives

To evaluate the efficacy of simplified dehydration protocols, in the absence of tubular occlusion, on bond strength and interfacial nanoleakage of a hydrophobic experimental adhesive blend to acid-etched, ethanol-dehydrated dentine immediately and after 6 months.

Methods

Molars were randomly assigned to 6 treatment groups (n = 5). Under pulpal pressure simulation, dentine crowns were acid-etched with 35% H₃PO₄ and rinsed with water. Adper Scotchbond Multi-Purpose was used for the control group. The remaining groups had their dentine surface dehydrated with ethanol solutions: group 1 = 50%, 70%, 80%, 95% and 3 × 100%, 30 s for each application; group 2 the same ethanol sequence with 15 s for each solution; groups 3, 4 and 5 used 100% ethanol only, applied in seven, three or one 30 s step, respectively. After dehydration, a primer (50% BisGMA + TEGDMA, 50% ethanol) was used, followed by the neat comonomer adhesive application. Resin composite build-ups were then prepared using an incremental technique. Specimens were stored for 24 h, sectioned into beams and stressed to failure after 24 h or after 6 months of artificial ageing. Interfacial silver leakage evaluation was performed for both storage periods (n = 5 per subgroup).

Results

Group 1 showed higher bond strengths at 24 h or after 6 months of ageing (45.6 ± 5.9^a/43.1 ± 3.2^a MPa) and lower silver impregnation. Bond strength results were statistically similar to control group (41.2 ± 3.3^ab/38.3 ± 4.0^ab MPa), group 2 (40.0 ± 3.1^ab/38.6 ± 3.2^ab MPa), and group 3 at 24 h (35.5 ± 4.3^ab MPa). Groups 4 (34.6 ± 5.7^bc/25.9 ± 4.1^c MPa) and 5 (24.7 ± 4.9^c/18.2 ± 4.2^c MPa) resulted in lower bond strengths, extensive interfacial nanoleakage and more prominent reductions (up to 25%) in bond strengths after 6 months of ageing.

Conclusions

Simplified dehydration protocols using one or three 100% ethanol applications should be avoided for the ethanol-wet bonding technique in the absence of tubular occlusion, as they showed decreased bond strength, more severe nanoleakage and reduced bond stability over time.     

Flexural strength of fluorapatite-leucite and fluorapatite porcelains exposed to erosive agents in cyclic immersion

Objective

The aim of this study was to evaluate the flexural strength of two porcelain materials (IPS d.SIGN and IPS e.max Ceram) exposed to erosive agents

Material and Methods

One hundred and twenty bar-shaped specimens were made from each of fluorapatite-leucite porcelain (IPS d.SIGN) and fluorapatite porcelain (IPS e.max Ceram) and divided into 8 groups of 15 specimens each. Six groups were alternately immersed in the following storage agents for 30 min: deionized water (control), citrate buffer solution, pineapple juice, green mango juice, cola soft drink and 4% acetic acid. Then, they were immersed for 5 min in deionized water at 37°C. Seven cycles were completed, totalizing 245 min. A 7^th group was continuously immersed in 4% acetic acid at 80°C for 16 h. The final, 8^th, group was stored dry at 37°C for 245 min. Three-point bending tests were performed in a universal testing machine. The data were analyzed statistically by 2-way ANOVA, Tukey’s HSD test and t-test at significance level of 0.05.

Results

The flexural strengths of all groups of each porcelain after exposure to erosive agents in cyclic immersion did not differ significantly (p>0.05). For both types of porcelain, dry storage at 37°C yielded the highest flexural strength, though without significant difference from the other groups (p>0.05). The flexural strengths of all groups of fluorapatite porcelains were significantly higher (p<0.05) than those of the fluorapatite-leucite porcelains.

Conclusions

This study demonstrated that the erosive agents evaluated did not affect the flexural strength of the tested dental porcelains.     

Electrochemistry of a urea-functionalized calix[4]diquinone sulfate-anion selective receptor

A new class of neutral ligands is synthesized and studied for the binding properties with anions by electrochemical methods. The binding of calix[4]diquinone 1 with HSO₄^? causes a large negative shift of the electrode potentials of the calix[4]diquinone. This novel neutral anion receptor 1 binds anions through hydrogen-bonding and shows high selectivity for HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^?. The selectivity of HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^? may be attributed to the stronger hydrogen-bonding with the urea moiety, and also with the quinone moiety of 1 receptor, and also the greater compatibility of the cavity of 1 with tetrahedral HSO₄^?.