Gingival fibroblast response to (hybrid) ceramic implant reconstruction surfaces is modulated by biomaterial type and surface treatment

OBJECTIVES

Surface characteristics of implant reconstructions determine the gingival fibroblast (GF) response and thus soft tissue integration (STI). However, for monolithic implant reconstructions it is unknown whether the (hybrid) ceramic biomaterial type and its surface treatment affect GF response. Therefore, this investigation examined the influence of the implant reconstruction biomaterials hybrid ceramic (HC), lithium disilicate ceramic (LS), 4 and 5 mol% yttria partially stabilized zirconiumdioxide ceramics (4/5Y-PSZ) and their surface treatment - machining, polishing or glazing - on surface characteristics and GF response.

METHODS

After characterization of surface topography and wettability by scanning electron microscopy, interferometry and contact angle measurement, the adhesion, morphology, metabolic activity and proliferation of GFs from six donors was investigated by fluorescent staining and a resazurin-based assay at days 1, 3 and 7. Titanium (Ti) served as control.

RESULTS

Biomaterial type and surface treatment affected the GF response in a topography-dependent manner. Smooth polished and glazed surfaces demonstrated enhanced GF adhesion and earlier proliferation onset compared to rough machined surfaces. Due to minor differences in surface topography of polished and glazed surfaces, however, the GF response was similar for polished and glazed HC, LS, 4- and 5Y-PSZ as well as Ti.

SIGNIFICANCE

Within the limits of the present investigation, polishing and glazing of machined HC, LS and 4/5Y-PSZ can be recommended to support STI-relevant cell functions in GF. Since the GF response on polished and glazed HC, LS, 4- and 5Y-PSZ surfaces and the Ti control was comparable, this investigation proofed equal cytocompatibility of these surfaces in vitro.

Zirconium dioxide nanoparticles induced cytotoxicity in rat cerebral cortical neurons and apoptosis in neuron-like N2a and PC12 cell lines

During recent decades, the application of zirconium dioxide nanoparticles (ZrO2-NP) has been expanded in various fields ranging from medicine to industry. It has been shown that ZrO2-NP has the potential to cross the blood-brain barrier (BBB) and induce neurotoxicity. In the current study, we investigated the in vivo neurotoxicity, as well as, the cellular mechanism of ZrO2-NP toxicity on two neuronal-like cell lines, PC12 and N2a. PC12 and N2a cells were exposed to increasing concentrations of ZrO2-NP (0-2000 µg/ml) for 48 h. The apoptotic effect of ZrO2-NP was determined using annexin V/propidium iodide double staining (by flow cytometry), and western blot analysis of relative apoptotic proteins, including caspase-3, caspase-9, bax, and bcl2. Based on our results, ZrO2-NP at concentrations of 250-2000 μg/mL increased both early and late-stage apoptosis in a concentration-dependent manner. Moreover, the expressions of cleaved-caspase-3 and -9 proteins and the bax/bcl2 ratio were significantly increased. In addition, oral administration of ZrO2-NP (50 mg/kg) to male Wistar rats for 28 days led to the loss of neuronal cells in the cerebral cortex. Taken together, our findings highlighted the role of apoptosis on cytotoxicity induced by ZrO2-NP.

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures

OBJECTIVES

The aim of this study was to compare failure load and initial damage in monolithic, partially veneered, and completely veneered (translucent) zirconia cantilevered fixed partial dentures (CFPDs), as well as completely veneered metal-ceramic CFPDs under different support and loading configurations.

MATERIALS AND METHODS

Eight test groups with anatomically congruent CFPDs (n = 8/group) were fabricated, differing in CFPD material/support structure/loading direction (load applied via steel ball (Ø 6 mm) 3 mm from the distal end of the pontic for axial loading with a 2-point contact on the inner cusp ridges of the buccal and oral cusps and 1.3 mm below the oral cusp tip for 30° oblique loading): (1) monolithic zirconia/CoCr abutment teeth/axial, (2) monolithic zirconia/CoCr abutment teeth/oblique, (3) partially veneered zirconia/CoCr abutment teeth/axial, (4) partially veneered zirconia/CoCr abutment teeth/oblique, (5) completely veneered zirconia/CoCr abutment teeth/axial, (6) completely veneered CoCr/CoCr abutment teeth/axial (control group), (7) partially veneered zirconia/implants/axial, and (8) partially veneered zirconia/natural teeth/axial. Restorations were artificially aged before failure testing. Statistical analysis was conducted using one-way ANOVA and Tukey post hoc tests.

RESULTS

Mean failure loads ranged from 392 N (group 8) to 1181 N (group 1). Axially loaded monolithic zirconia CFPDs (group 1) and controls (group 6) showed significantly higher failure loads. Oblique loading significantly reduced failure loads for monolithic zirconia CFPDs (group 2). Initial damage was observed in all groups except monolithic zirconia groups, and fractography revealed design flaws (sharp edges at the occlusal boundary of the veneering window) in partially veneered zirconia CFPDs.

CONCLUSIONS

Monolithic zirconia CFPDs might be a viable alternative to completely veneered CoCr CFPDs in terms of fracture load. However, oblique loading of monolithic zirconia CFPDs should be avoided in clinical scenarios. Design improvements are required for partially veneered zirconia CFPDs to enhance their load-bearing capacity.

CLINICAL RELEVANCE

Monolithic zirconia may represent a viable all-ceramic alternative to the established metal-ceramic option for CFPD fabrication. However, in daily clinical practice, careful occlusal adjustment and regular monitoring should ensure that oblique loading of the cantilever is avoided.

Impact of restoration thickness and tooth shade background on the translucency of zirconia laminate veneers: An in vitro comparative study

Purpose

Our in vitro comparative study aimed to investigate the impact of thickness and tooth shade background on the translucency of highly translucent zirconia veneers.

Materials and Methods

A total of 75 5Y-TZP zirconia veneers of shade A1 were fabricated with thicknesses of 0.50 mm (n = 25), 0.75 mm (n = 25), and 1.0 mm (n = 25). The translucencies were measured on composite resin teeth with shades A1, A2, A3, A3.5, and A4 using a digital color imaging spectrophotometer. Data were analyzed using ANOVA and post hoc Tukey's test (p < 0.05).

Results

The translucency values were optimal for the veneers placed over the substrate teeth with shades A1 and A2, regardless of the veneer thickness. Additionally, veneers with a thickness of 0.50 mm exhibited significantly higher translucency than those with thicknesses of 0.75 mm and 1.0 mm.

Conclusions

Our study demonstrated that the translucency of the highly translucent zirconia veneers was influenced by both veneer thickness and tooth shade background. The optimal veneer thickness for achieving the highest translucency was 0.50 for the veneers with A1 and A2 shades placed over the substrate teeth.

Clinical Relevance

The optimal thickness for achieving the highest translucency of the highly translucent zirconia laminate veneers was 0.50 mm for the veneers with A1 and A2 shades placed over the substrate teeth. Clinicians and dental technicians could consider this when selecting materials for aesthetic restorations.

Survival and success of zirconia compared with titanium implants: a systematic review and meta-analysis

OBJECTIVE

This systematic review assessed the available evidence on the survival and success rate of zirconia and titanium implants. As secondary outcomes, aesthetic, radiographic and clinical parameters, as well as biological and mechanical complications, were considered.

MATERIALS AND METHODS

A systematic search was performed up to March 2022 to identify CCTs/RCTs comparing zirconia and titanium implants with a minimum of 12 months of follow-up. Meta-analysis was performed when ≥ 2 articles with similar characteristics were retrieved.

RESULTS

Four published articles with two RCTs (2 different patient populations) with 100 zirconia and 99 titanium implants that were followed up over 12-80 months were selected out of the 6040 articles. A non-statistically significant difference between zirconia and titanium implant survival at 12 months was suggested (P = 0.0938). The success rates were 57.5-93.3% and 57.1-100% for zirconia and titanium implants, respectively. The pink aesthetic score (PES) was higher for zirconia (10.33 ± 2.06 to 11.38 ± 0.92) compared to titanium implants (8.14 ± 3.58 to 11.56 ± 1.0).

CONCLUSION

Based on the 2 RCTs retrieved in the literature, similar survival rates were reported for zirconia and titanium implants in the short term (12 months of follow-up). Future RCTs are warranted to evaluate the long-term outcomes of zirconia implants.

CLINICAL RELEVANCE

Zirconia implants may be the procedure of choice, particularly in the aesthetic zone, since they show a similar survival and success rate as titanium implants on a short-term follow-up.

TRIAL REGISTRATION

Systematic review registration number-CRD42021288704 (PROSPERO).

Zirconium dioxide as electrochemiluminescence emitter for D-dimer determination based on dual-quenching sensing strategy

The ECL emission of simple and stable zirconium dioxide nanomaterials has always been a blank slate in the ECL sensors field. In this work, zirconium dioxide (ZrO₂)-titanium dioxide (TiO₂)-gold nanoparticle (AuNPs) composite (ZT-Au), a novel self-enhanced ECL emitter, was introduced the system of dual-quenching ECL immunosensor. The anodic luminescence of ZrO₂ in the system of tripropylamine (TPrA) as a co-reagent was first reported and explored. Meanwhile, TiO₂ was designed into the ECL scheme as a co-reaction accelerator to form the ZrO₂/TPrA/TiO₂ ternary system, which can efficiently amplify the ECL signal of the emitter. In addition, cuprous oxide-triaminophenol (Cu₂O-APF) as the quencher was devoted to the dual-quenching sensing strategy. The dual-quenching mechanism that effectively boosted the immunosensor sensitivity was adequately investigated and conjectured in this paper. The sensing model based on the luminophor ZT-Au and the quencher Cu₂O-APF was utilized for the detection of D-dimer, a reliable marker for the diagnosis and evaluation of thrombotic diseases. The short peptide ligands NARKFYKGC (NFC) with efficient biological affinity were used to site-directionally capture antibodies for adequately protecting the activity of antigen binding sites during the construction of the immunosensor. The implemented immunosensor was equipped with a broad linear range of 0.01-500 ng/mL and a low detection limit of 3.6 pg/mL. The original methodology opens up the field of vision for the detection of additional biomarkers.

Extra-modification of zirconium dioxide for potential photocatalytic applications towards environmental remediation: A critical review

Photocatalytic degradation is a valuable direction for eliminating organic pollutants in the environment because of its exceptional catalytic activity and low energy requirements. As one of the prospective photocatalysts, zirconium dioxide (ZrO₂) is a promising candidate for photoactivity due to its favorable redox potential and higher chemical stability. ZrO₂ has a high rate of electron-hole recombination and poor light-harvesting capabilities. Still, modification has demonstrated enhancements, especially extra-modification, and is therefore worthy of investigation. This present review provides a comprehensive overview of the extra-modifications of ZrO₂ for enhanced photocatalytic performance, including coupling with other semiconductors, doping with metal, non-metal, and co-doping with metal and non-metal. The extra-modified ZrO₂ showed superior performance in degrading the organic pollutant, particularly dyes and phenolic compounds. Interestingly, this review also briefly highlighted the probable mechanisms of the extra-modification of ZrO₂ such as p-n heterojunction, type II heterojunction, and Z-scheme heterojunction. The latter heterojunction with excellent electron-hole space separation improved the photoactivity. Extensive research on ZrO₂'s photocatalytic potential is presented, including the removal of heavy metals, the redox of heavy metals and organic pollutants, and the evolution of hydrogen. Modified ZrO₂'s photocatalytic effectiveness depends on its band position, oxygen vacancy concentration, and metal defect sites. The opportunities and future problems of the extra-modified ZrO₂ photocatalyst are also discussed. This review aims to share knowledge regarding extra-modified ZrO₂ photocatalysts and inspire new environmental remediation applications.

Simple separation of glycosphingolipids in the lower phase of a Folch's partition from crude lipid fractions using zirconium dioxide

A simple method was developed for the separation of glycosphingolipids (GSLs) from lipid mixtures, including phospholipids and cholesterol, using zirconium dioxide (zirconia, ZrO₂). Although this procedure does not incorporate a mild alkali treatment, which is commonly used for eliminating glycerophospholipids, it can be used to remove both alkali-resistant sphingomyelin and glycerophospholipids possessing ether bonds. Importantly, when GSLs were dissolved in organic solvent together with cholesterol (Chol) and phospholipids, and loaded onto ZrO₂, Chol did not bind to the ZrO₂ but both the GSLs and phospholipids did. When eluted with 5 mg/mL of 2,5-dihydroxybenzoic acid in methanol, GSLs but not phospholipids were recovered, leaving the phospholipids bound to the ZrO₂ particles. This method is particularly applicable for GSLs such as triglycosylceramides, tetraglycosylceramides and some pentaglycosylceramides, sulfatide and GM3 located in the lower phase of a Folch's partition, where significant amounts of phospholipids, Chol and neutral lipids reside along with GSLs. This method was successfully used to easily isolate GSLs from biological materials for their subsequent analysis by matrix-assisted laser desorption ionization time-of-flight mass spectrometry with high resolution.

A review on self-modification of zirconium dioxide nanocatalysts with enhanced visible-light-driven photodegradation of organic pollutants

Over the past few years, photocatalysis is one of the most promising approaches for removing organic pollutants. Zirconium dioxide (ZrO₂) has been shown to be effective in the photodegradation of organic pollutants. However, low photoresponse and fast electron-hole recombination of ZrO₂ affected the efficiency of catalytic performance. Modifying the photocatalyst itself (self-modification) is a prominent way to enhance the photoactivity of ZrO₂. Moreover, as ZrO₂-like photocatalysts have a large bandgap, improving the spectral response via self-modification could extend the visible light region and reduce the chance of recombination. Here, we review the self-modification of ZrO₂ for enhanced the degradation of organic pollutants. The approaches of the ZrO₂ self-modification, including the type of synthetic route and synthesis parameter variation, are discussed in the review. This will be followed by a brief section on the effect of ZrO₂ self-modification in terms of morphology, crystal structure, and surface defects for enhanced photodegradation efficiency. It also covers the discussion on the photocatalytic mechanism of ZrO₂ self-modification. Finally, some challenges with ZrO₂ catalysts are also discussed to promote new ideas to improve photocatalytic performance.

Performance of PEEK based telescopic crowns, a comparative study

OBJECTIVE

Telescopic crowns are suitable components of partial dentures to efficiently anchor dental supra-structures to teeth or dental implants and achieve high chewing performance and wear comfort. Usually alloy- or metal-based structures are used for the primary and the secondary crowns. The advantage is the possibility to produce precise structures with a high perfection and sufficient friction force, but the disadvantage is the corrosion instability. The recent introduction of zirconia ceramics has enabled the fabrication of ceramic primary crowns, thus reducing corrodibility. The novel application of the high-performance polymer polyetheretherketone (PEEK) as another metal-free alternative material offers a new perspective for such applications. Therefore, the aim of this work was to assess the performance of telescopic crowns of PEEK by comparing telescopic crowns based on the combination of PEEK (prim. crown) + PEEK (sec. crown) with the pairings ZrO₂ (prim. crown) + PEEK (sec. crown) and CoCr-alloy (prim. crown) + PEEK (sec. crown).

METHODS

All specimens were CAD/CAM planned and manufactured based on a model of a tooth 26. One master dental technician performed the post-treatment. For each group of material pairing, n = 9 telescopic crown pairs were manufactured and tested. Herein not only the maximum retention force was measured but also the retention force vs. pull-off distance were analyzed. As there is no commonly accepted test protocol available, the influence of various pull off speeds were tested as well. All measurements were first made with three blocks of three crowns (3C), subsequently with three blocks of two crowns (2C) and finally with nine single crowns (1C). The long-term behavior was estimated by performing 10.000 cycles, which is related to a life-time of more than 10 years.

RESULTS

The maximum retention force in case of PEEK + PEEK was higher in comparison to the other tested material pairings. In the range between 1 and 10 mm/ min pull off speed there was no significant influence by the pull off speed. More influence on the friction force would be expected by changes of the number of the crowns acting simultaneously. The friction force was decreasing with decreasing number of crowns but not linearly in any tested case. The long-term test has shown that the friction force remained constant.

SIGNIFICANCE

The performance of PEEK + PEEK telescopes is comparable with the usually applied material pairings. Over long time no loss in retention force could be observed. The retention force - distance progression in the PEEK + PEEK pairing offers more security against a possible loss of retention during repair or relining. For further tests of the performance of telescopic crowns or to estimate of friction force limits, a setup with at least two, but preferably three, crowns tested in parallel is suggested.

Poly (ε-Caprolactone)/Cellulose Nanofiber Blend Nanocomposites Containing ZrO2 Nanoparticles: A New Biocompatible Wound Dressing Bandage with Antimicrobial Activity

Purpose: In the present study, the poly (ε-caprolactone)/cellulose nanofiber containing ZrO₂ nanoparticles (PCL/CNF/ZrO₂ ) nanocomposite was synthesized for wound dressing bandage with antimicrobial activity.

Methods: PCL/CNF/ZrO₂ nanocomposite was synthesized in three different zirconium dioxide amount (0.5, 1, 2%). Also the prepared nanocomposites were characterized by Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). In addition, the morphology of the samples was observed by scanning electron microscopy (SEM).

Results: Analysis of the XRD spectra showed a preserved structure for PCL semi-crystalline in nanocomposites and an increase in the concentrations of ZrO₂ nanoparticles, the structure of nanocomposite was amorphous as well. The results of TGA, DTA, DSC showed thermal stability and strength properties for the nanocomposites which were more thermal stable and thermal integrate compared to PCL. The contact angles of the nanocomposites narrowed as the amount of ZrO₂ in the structure increased. The evaluation of biological activities showed that the PCL/CNF/ZrO₂ nanocomposite with various concentrations of ZrO₂ nanoparticles exhibited moderate to good antimicrobial activity against all tested bacterial and fungal strains. Furthermore, cytocompatibility of the scaffolds was assessed by MTT assay and cell viability studies proved the non-toxic nature of the nanocomposites.

Conclusion: The results show that the biodegradability of nanocomposite has advantages that can be used as wound dressing.

Insertion of Small Diameter Radiopaque Tracking Beads into the Anterior Cruciate Ligament Results in Repeatable Strain Measurement Without Affecting the Material Properties

The characterization of ligamentous soft tissue properties is limited by a lack of measurement methods capable of minimally-invasively quantifying regional strain. Previous implementations of radiographic imaging and tissue-embedded radiopaque markers demonstrated promising regional strain measurements, but found error associated with non-repeatable bead positions within the tissue after load application. No study has investigated the effects of cyclic loading on the strains measured within the tissue. The purpose of this study was to quantify the effect of joint loading on strain measurement using radiopaque markers and micro-computed tomography imaging. Six cadaveric porcine femur-anterior cruciate ligament-tibia complexes were instrumented with small diameter (0.8 mm) zirconium dioxide marker beads. The compound was imaged at 10 N then at 100 N of anterior force using micro-computed tomography. The bead positions in the images were used to calculate tissue strain between the 10 and 100 N anterior joint load conditions. Up to 100 intermediate joint cycles were applied, then images were acquired again at 10 and 100 N anterior force. No statistically significant difference was found between the strains measured before and after intermediate cycling (p > 0.05). This indicates that tissue loading did not introduce statistically significant changes to strains measured in tissue tested following this methodology.

Catalytic Reaction Mechanism of NO-CO on the ZrO2 (110) and (111) Surfaces

Due to the large population of vehicles, significant amounts of carbon monoxide (CO), nitrogen oxides (NO_x), and unburned hydrocarbons (HC) are emitted into the atmosphere, causing serious pollution to the environment. The use of catalysis prevents the exhaust from entering the atmosphere. To better understand the catalytic mechanism, it is necessary to establish a detailed chemical reaction mechanism. In this study, the adsorption behaviors of CO and NO, the reaction of NO reduction with CO on the ZrO₂ (110) and (111) surfaces was performed through periodic density functional theory (DFT) calculations. The detailed mechanism for CO₂ and N₂ formation mainly involved two intermediates N₂O complexes and NCO species. Moreover, the existence of oxygen vacancies was crucial for NO reduction reactions. From the calculated energy, it was found that the pathway involving NCO intermediate interaction occurring on the ZrO₂ (110) surface was most favorable. Gas phase N₂O formation and dissociation were also considered in this study. The results indicated the role of reaction intermediates NCO and N₂O in catalytic reactions, which could solve the key scientific problems and disputes existing in the current experiments.

Sonochemical synthesis and fabrication of honeycomb like zirconium dioxide with chitosan modified electrode for sensitive electrochemical determination of anti-tuberculosis (TB) drug

Herein, novel honeycomb like zirconium dioxide with chitosan (ZrO₂@chitosan) nanocomposite have been designed through a facile ultrasound-assisted method and followed by a simple sonication process (bath-type ultrasound washer; Honda Electronics-W-118T; 100 W/cm² and 300 kHz frequency). After then, as-synthesized ZrO₂@chitosan was characterized by FESEM, XRD and EIS. The ZrO₂@chitosan nanocomposite modified glassy carbon electrode shows excellent electrochemical sensing performance towards anti-tuberculosis drug (rifampicin). Furthermore, the ZrO₂@chitosan modified and fabricated electrochemical sensor showed a wide linear range between 0.015 µM and 547.4 µM and nanomolar detection limit (7.5 nM). Moreover, the ZrO₂@chitosan modified electrode showed selectivity towards the detection of anti-tuberculosis drug (rifampicin). The ZrO₂@chitosan nanocomposite film modified non-enzymatic sensor has high stable and good reproducible towards the detection of rifampicin. In addition, the as-synthesized ZrO₂@chitosan nanocomposite modified electrode has been applied to the determination of rifampicin in biological samples such as human serum and urine samples.

Investigation of physical, mechanical and tribological properties of Al6061-ZrO2 nano-composites

The present investigation mainly concentrates on work done in order to explore physical, mechanical & tribological characteristics of Al6061 alloy reinforced with nano-sized zirconium dioxide particulates. Four casts of different percentages of reinforcement from 0 to 6 wt% in the steps of 2 are fabricated using liquid metallurgy technique (stir casting). The prepared composites later subjected to various physical, mechanical & wear tests and results were studied. The tests were carried out in accordance with the ASTM standards on the alloy and nano-composites. In the present investigation the physical and mechanical properties like density, hardness and tensile strength increased significantly with the increase in percentage of reinforcement in the matrix alloy, while the percentage elongation found to be decreased. The sliding wear tests were performed by using pin-on-disc the tribometer and results indicated that wear resistance of composites was higher. Off the four compositions, there were improved properties of composites with higher weight percent of reinforcement. Scanning Electron Microscope (SEM) micrographs was used after tensile testing to study fractured surfaces of specimens and wear morphology after wear testing. Overall the investigational outcomes are very interesting and motivates to do further more research.

Investigations on synthesis, characterization and humidity sensing properties of ZnO and ZnO-ZrO2 composite nanoparticles prepared by ultrasonic assisted wet chemical method

In the present investigations, Zinc oxide (ZnO) and ZnO-ZrO₂ composite nanoparticles were synthesized by ultrasonic assisted wet chemical method to investigate their structural, optical and humidity sensing properties. The synthesized nanoparticles were characterized by the techniques like X ray diffraction (XRD), UV-Vis absorption spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). XRD and EDS were employed to confirm the phase formation and phase purity respectively. SEM micrographs showed that morphology of the parent compound ZnO is considerably changed with varying concentration of ZrO₂. The optical absorption spectra showed that optical absorption of ZnO decreases with increase in ZrO₂ content in the composite. The observed band gap values for ZnO and ZnO-ZrO₂ composites were higher as compared to the bulk sample. The humidity sensing performance was substantiated for all the samples and the result of effect of concentration of ZrO₂ in ZnO-ZrO₂ composites on sensitivity, response and recovery time are discussed in detail.

A prospective clinical study to evaluate the performance of zirconium dioxide dental implants in single-tooth edentulous area: 3-year follow-up

BACKGROUND

Traditionally, dental implants have been made from titanium or titanium alloys. Alternatively, zirconia-based ceramic implants have been developed with similar characteristics of functional strength and osseointegration. Ceramic implants offer advantages in certain settings, e.g. in patients who object to metal dental implants. The aim of this study was to investigate the mid-term (36 months) clinical performance of a ceramic monotype implant in single-tooth edentulous area.

METHODS

This was a prospective, open-label, single-arm study in patients requiring implant rehabilitation in single-tooth edentulous area. Ceramic implants (PURE Ceramic Implant, Institut Straumann AG, Basel, Switzerland) with a diameter of 4.1 mm were placed following standard procedure and loaded with provisional and final prostheses after 3 and 6 months, respectively. Implant survival rate and implant success rate were evaluated and crestal bone levels were measured by analysing standardized radiographs during implant surgery and at 6, 12, 24 and 36 months.

RESULTS

Forty-four patients received a study implant, of whom one patient withdrew consent after 3 months. With one implant lost during the first 6 months after surgery, the implant survival rate was 97.7% at 6 months. No further implants were lost over the following 30 months, and 3 patients were lost to follow-up during this time frame. This led to a survival rate of 97.5% at 36 months. Six months after implant surgery 93.0% of the implants were considered "successful", increasing to 97.6% at 12 months and remaining at this level at 24 months (95.1%) and 36 months (97.5%). Bone loss was most pronounced in the first half-year after implant surgery (0.88 ± 0.86 mm). By contrast, between 12 and 36 months the mean bone level remained stable (minimal gain of 0.06 [± 0.60] mm). Hence, the overall bone loss from implant surgery to 36 months was 0.97 (± 0.88) mm.

CONCLUSIONS

In the follow-up period ceramic implants can achieve favourable clinical outcomes on a par with titanium implants. For instance, these implants can be recommended for patients who object to metal dental implants. However, longer term studies with different edentulous morphology need to confirm the present data.

TRIAL REGISTRATION

Registered on www.clinicaltrials.gov : NCT02163395 .

Synthesis and characterization of a heterojunction rGO/ZrO2/Ag3PO4 nanocomposite for degradation of organic contaminants

Synergy between surface adsorption and photocatalysis is key for effective contaminant degradation in the liquid phase. Herein, we report a heterojunction photocatalyst of reduced graphene oxide (rGO)/zirconium dioxide (ZrO₂)/silver phosphate (Ag₃PO₄) that incorporates this synergy for 4-nitrophenol (PNP) removal. Compared with other photocatalyst combinations, ZrO₂ and Ag₃PO₄ coupling generates reactive species with greater degradation potential. ZrO₂ and rGO were synthesized by a green approach using a one-step hydrothermal reaction in ethanol-water. The growth of rGO/ZrO₂ and Ag₃PO₄ were accomplished and the functions of each part were well developed together. The rGO/ZrO₂/Ag₃PO₄ composite exhibited enhanced light absorption and a low band gap energy (2.3 eV) owing to rGO and Ag₃PO₄ integration. The composite's photocatalytic activity was much higher than that of ZrO₂, Ag₃PO₄, or ZrO₂/Ag₃PO₄. The maximal adsorption of PNP was 26.88 mg/g, and a pseudo-first-order model described the PNP degradation kinetics (k = 0.034 min^-1). Synergy between the three components resulted in 97% PNP removal in 90 min, and even after five cycles, 94% PNP removal was obtained. The quantum yield of the system (7.31 × 10^-5 molecules/photon) was compared with those in previous reports to assess the photocatalytic performance and energy requirements.

Evaluation of reversed-phase nano liquid chromatography conditions by using reversed-phase thin layer chromatography based on Hansen solubility parameters for the analysis of amphiphilic glycosylsphingolipid transformations

Pulse chase analysis is often used in investigating dynamics of cellular substances. Fluorescently labeled lactosyl sphingosine molecule is useful in chasing its transformation, however the analysis of such metabolites in attomole level is of extreme difficult due to the presence of large amount of endogenous amphiphilic molecules such as glycosphingolipids, sphingomyerin, and glycerophospholipids. Nano LC suites for analyzing the attomole scale metabolites, therefore removal of endogenous substances prior to nano LC and finding appropriate nano LC conditions are necessary. Thus, we focused on the solubility of fluorescent BODIPY-labeled lactosylsphingosine (Lac-Sph-BODIPY) to identify suitable solvents to remove endogenous compounds. In this study, we evaluated solvents by using C18 thin layer chromatography (RP TLC). The mobility (R_f) of Lac-Sph-BODIPY against several solvent mixtures on RP TLC were plotted against polarity and hydrogen bonding capability followed by Hansen solubility parameters (HSPs). The optimum solvent mixture with R_f = 0.3 ± 0.1 was chosen for elimination of endogenous phospholipids on a ZrO₂-SiO₂ cartridge column and subsequent separation by nano LC. Efficient removal of endogenous phospholipids was demonstrated, and good resolution in nano LC analysis of Lac-Sph-BODIPY extracted from Chinese hamster ovary (CHO)-K1 cells was achieved. It was also shown that the amount of exogenously added compound was important in the investigation of metabolites using cultured cells.

Effect of nanostructured zirconium dioxide incorporation in an experimental adhesive resin

OBJECTIVES

The aim of this study was to evaluate the influence of nanostructured zirconium dioxide incorporation in an experimental adhesive resin.

METHODS

ZrO₂ particles were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy and Brunauer-Emmett-Teller (B.E.T). Experimental adhesive resins were formulated with 0, 0.5, 1, 4.8, and 9.1% ZrO₂ in weight. The adhesives were evaluated based on degree of conversion (DC), radiopacity, softening in solvent and microtensile bond strength (μTBS) 24 h and after 1 year of aging. Mineral deposition at the hybrid layer was assessed with micro-Raman spectroscopy at the baseline and after 14 days.

RESULTS

XRD showed monoclinic and tetragonal phases of ZrO_2.particles. B.E.T data revealed a surface area of 37.41 m²/g, and typical chemical groups were shown on the Raman spectra_. The addition of ZrO₂ did not influence the radiopacity. The addition of 4.8% and 9.1 wt.% ZrO₂ showed higher initial hardness with increased softening in solvent (P < 0.05) and promoted mineral deposition at the dentin interface. DC was significantly increased in the group with 1% ZrO₂ (P < 0.05). The μTBS test showed difference on the group with 9.1 wt.% of ZrO₂, with a significant reduction after aging.

CONCLUSION

The incorporation of ZrO₂ promoted mineral deposition on the adhesive interface and the addition of 1 wt.% caused a significant increase on the DC without compromising the other physicochemical characteristics, which may prove promising for the development of new dental adhesive systems.

CLINICAL RELEVANCE

The mineral deposition on the hybrid layer can result in a longer stability of the adhesive, thus delaying the hydrolytic degradation.

Adhesion of living cells to abutment materials, dentin, and adhesive luting cement with different surface qualities

OBJECTIVE

We tested the adhesion properties of living gingival fibroblasts on three different implant abutment materials, adhesive resin used to bond bi-partite abutments, and human dentin.

METHODS

Discs of lithium disilicate (LS), zirconium dioxide (Zr), adhesive resin cement (AR), titanium (Ti), and human dentin (HD) were fabricated with three different levels of surface roughness (rough, machined, and polished). Ra and Rz, water contact angle, and cell detachment forces were measured. Cell detachment force was measured for single cells using single-cell force spectroscopy. Data were statistically analyzed using parametric tests (ANOVA, MANOVA, Bonferroni post-hoc tests).

RESULTS

Surface roughness significantly influenced the water contact angle for all materials (P≤0.05). Overall, HD showed the lowest contact angle, followed by LS, Ti, Zr, and AR (P≤0.05). Comparison of cell detachment forces between materials with rough and machined surfaces revealed no significant differences (P>0.05), with the exception of Zr compared to HD with rough surfaces (P=0.006). For polished surfaces, HD showed the highest detachment force (P≤0.0001), followed by Ti, AR, and Zr, which did not significantly differ from each other (P>0.05) and LS; Ti/AR was significantly different from LS (P≤0.05). Except for HD, where polished surfaces exhibited the highest cell detachment force (P≤0.002), most machined surfaces showed higher cell detachment forces than polished or rough surfaces.

SIGNIFICANCE

Implant abutments should ideally be provided with a machined like surface roughness for best cell adhesion.

Theoretical study on the initial reaction mechanisms of ansa-metallocene zirconium precursor on hydroxylated Si(1 0 0) surface

The initial reaction mechanisms for depositing ZrO2 thin films using ansa-metallocene zirconium (Cp2CMe2)ZrMe2 precursor were studied by density functional theory (DFT) calculations. The (Cp2CMe2)ZrMe2 precursor could be absorbed on the hydroxylated Si(1 0 0) surface via physisorption. Possible reaction pathways of (Cp2CMe2)ZrMe2 were proposed. For each reaction, the activation energies and reaction energies were compared, and stationary points along the reaction pathways were shown. In addition, the influence of dispersion effects on the reactions was evaluated by non-local dispersion corrected DFT calculations.

Effect of 10 different TiO2 and ZrO2 (nano)materials on the soil invertebrate Enchytraeus crypticus

Nearly 80% of all the nano-powders produced worldwide are metal oxides, and among these materials titanium dioxide (TiO2 ) is one of the most produced. Titanium dioxide's toxicity is estimated as low to soil organisms, but some studies have shown that TiO2 nanoparticles can cause oxidative stress. Additionally, it is known that TiO2 is activated by ultraviolet (UV) radiation, which can promote photocatalytic generation of reactive oxygen species, which is seldom taken into account in toxicity testing. In the present study, the authors investigated the effects of different TiO2 and zirconium materials on the soil oligochaete Enchytraeus crypticus, using exposure via soil, water, and soil:water extracts, and studied the effects combined with UV radiation. The results showed that zirconium dioxide (bulk and nano) was not toxic, whereas zirconium tetrachloride reduced enchytraeid reproduction in soil (50% effect concentration = 502 mg/kg). The TiO2 materials were also not toxic via soil exposure or under UV radiation. However, pre-exposure to TiO2 and UV radiation via aqueous media caused a lower reproductive output post-exposure in clean soil (20-50% less but only observed at the lowest concentration tested, 1 mg/L); that is, the effect of TiO2 in water was potentiated by the UV radiation and measurable as a decrease in reproduction in soil media.

Solid-phase zirconium and fluoride species in alkaline zircaloy cladding waste at Hanford

The United States Department of Energy Hanford Site, near Richland, Washington, USA, processed plutonium between 1944 and 1987. Fifty-six million gallons of waste of various origins remain, including waste from removing zircaloy fuel cladding using the so-called Zirflex process. The speciation of zirconium and fluoride in this waste is important because of the corrosivity and reactivity of fluoride as well as the (potentially) high density of Zr-phases. This study evaluates the solid-phase speciation of zirconium and fluoride using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Two waste samples were analyzed: one waste sample that is relatively pure zirconium cladding waste from tank 241-AW-105 and another that is a blend of zirconium cladding wastes and other high-level wastes from tank 241-C-104. Villiaumite (NaF) was found to be the dominant fluoride species in the cladding waste and natrophosphate (Na7F[PO4]2 · 19H2O) was the dominant species in the blended waste. Most zirconium was present as a sub-micron amorphous Na-Zr-O phase in the cladding waste and a Na-Al-Zr-O phase in the blended waste. Some zirconium was present in both tanks as either rounded or elongated crystalline needles of Na-bearing ZrO2 that are up to 200 μm in length. These results provide waste process planners the speciation data needed to develop disposal processes for this waste.