Zirconia Surface Research Articles

Surface modification of zirconia ceramics through cold plasma treatment and the graft polymerization of biomolecules

Although zirconia ceramics were highly versatile as dental implants, their long-term presence in the human body may slow down healing and impede cell growth in the past. To enhance the cytocompatibility of zirconia ceramics, surface activation modification was used to immobilize biopolymers such that a biomimetic environment was created. Hexamethyldisilazane thin films were deposited onto the surface of inorganic zirconia through cold plasma treatment under various power and deposition time settings to form an organosilane interface layer. Next, oxygen plasma treatment was performed to activate the free radicals on the surface. Subsequently, ultraviolet light was employed to graft and polymerize acrylic acid for generating carboxyl groups on the surface. This was followed by a condensation reaction with biopolymers (chitosan, chitosan/poly-γ-glutamic acid, and gelatin). Under a 20-min deposition time at 40W and 150 mTorr, the thin films had a maximum graft density of 2.1mg/cm2. MG-63cells (human osteosarcoma cells) were employed to evaluate cell compatibility. Chitosan and chitosan/poly-γ-glutamic acid promoted the compatibility of MG-63cells (a human osteosarcoma cell line) with zirconia ceramics, whereas gelatin reduced this compatibility. The findings confirm that cold plasma treatment and graft polymerization can promote the immobilization of biomolecules and improve the biocompatibility of zirconia ceramics. This approach can be applied to the modification of zirconia ceramic implants.

Investigation on microstructure, mechanical properties and tribological behavior of AlZnMgCu1.5-T6/zirconia surface nanocomposites developed by FSP

This research aimed to find the suitable condition for the fabrication of AlZnMgCu1.5-T6/ZrO2 nanocomposites to improve the mechanical properties and wear resistance of the produced surface nanocomposites. The effects of rotational speed and the number of passes were investigated to obtain the desired properties. For this purpose, rotational speeds of 1000 rpm, 1200 rpm, and 1400 rpm were used along with a constant traverse speed of 40 mm/min, and the number of processing passes was considered to be one and two passes. Optical microscopy and electron microscopy equipped with an EDS system were used to study the microstructural evolution, such as grain refinement and distribution of nanoparticles in these nanocomposites. To evaluate the mechanical and wear properties of the nanocomposites, tension, hardness, and wear tests were performed according to related standards. In the next step, the fracture surfaces were examined by XRD to investigate the formation of possible phases. Finally, fracture and wear surfaces were investigated to determine dominant mechanisms. In addition to the absence of defects, an extreme grain refinement due to the severe plastic deformation of the grains and the presence of ceramic nanoparticles were confirmed by microscopic observations. According to the results, due to the extreme grain refinement and the presence of ZrO2 hard ceramic nanoparticles, the average and maximum hardness values increased up to 33% and 48%, respectively, compared to those of the aluminum alloy matrix. Also, the wear rate was reduced up to 65%. It was concluded that according to the findings, the most suitable condition for achieving the optimal mechanical and wear properties is 1400 rpm-two passes.

The Correlation of Surface Roughness Parameters of Zirconia and Lithium Disilicate with Steatite Wear.

Various surface roughness parameters are utilized to describe the surface in the tooth to ceramics abrasion and to assess the resulting wear. The use of three-dimensional parameters may offer a better estimation for wear and an improved deduced clinical surface treatment. The aim of this study was to determine the influence of various surface roughness parameters of zirconia and lithium disilicate ceramics on the wear of steatite antagonists. Forty zirconia specimens with a diameter of 7 mm and a thickness of 3 mm and 40 lithium disilicate specimens with the dimensions 10×10×4 mm were each divided into five subgroups. Two subgroups were treated with different clinically established diamond burs; a third subgroup was treated with a silicone polishing set. Two additional subgroups were produced by glazing the surfaces after treatment. Surface roughness parameters were determined by laser scanning microscopy. All specimens underwent 1.2 million loading cycles using steatite antagonists. After regular intervals of cycles, precision impressions were made to assess the wear. The correlation between wear and different roughness parameters was evaluated using the Spearman correlation test. For the glazed zirconia, unglazed zirconia, and glazed lithium disilicate specimens no significant correlations (p > 0.05) between the investigated roughness parameters and antagonist wear could be found. In the unglazed lithium disilicate groups, significant (p ≤ 0.05) correlations with steatite substance loss could be found for several roughness parameters after 1.2 million cycles. For lithium disilicate, it seems not sufficient to use only one roughness parameter to indicate the wear behavior of the surface. There was no correlation between wear and the tested roughness parameters of zirconia surfaces.

Effect of femtosecond laser ablate ultra-fine microgrooves on surface properties of dental zirconia materials

ObjectivesZirconia is an important dental implant material, yet it surfaces milling method is still under investigation. To explore the feasibility of laser etching in processing fine micro grooves on the surface of zirconia and to observe fine micro groove structure’ influence on mouse embryonic osteoblasts, the survey was conducted. Methods31 zirconia discs were made and polished to mirror surface. Then, they were divided into 3 groups: the mirror group, the femtosecond laser ablated microgroove group and the air blasted + acid etched group. Then, the surface properties of zirconia discs were analyzed by Scanning Electron Microscope/Energy Dispersive Spectrometer (SEM/EDS), X-Ray Diffraction (XRD), Atomic Force Microscope (AFM), water contact angle test and micro-Vickers hardness test. The biocompatibility of each machined zirconia was tested by cell proliferation test and SEM analyze of cell morphology. Then, the effect of these surface treatment to MC-3T3-E1’s osteogenic differentiation was evaluated by Q-PCR test. ResultsSEM image showed that the femtosecond laser is a reliable method for forming regular-arranged microgrooves with pitch width of around 5 μm. EDS and XRD indicated that there were stable and purified tetragonal crystal system on the laser-roughened surface. AFM suggested that laser machining generated rougher surface (Ra) (271.7 ± 67.2 nm) than other groups. Furthermore, the contact angle showed laser ablated grooves induced anisotropic wetting. The micro-Vickers hardness test ascertained that laser-ablation strengthened zirconia surface. In vitro experiment showed that MC-3T3-E1 grown along the long axis of microgrooves on the first day. Besides, Real time PCR implied that osteogenesis-related gene expression OPN and ALP was much higher than the rest groups. SignificanceFemtosecond laser is able to machine zirconia with ultra-fine microgrooves (around 2.5 μm). These structures promoted MC-3T3-E1 cell to line along the microstructure and differentiate into osteogenic cells. Thus, femtosecond laser might be a potential processing options for zirconia micro-texturing.

Effect of Different Cleaning Methods on Shear Bond Strength of Resin Cement to Contaminated Zirconia

The aim of this study was to evaluate the effect of different cleaning methods on the shear bond strength (SBS) of resin cement to contaminated zirconia specimens. Eighty rectangular-shaped specimens (2 × 5 × 10 mm) were fabricated from Zirconia blocks (IPS e.max ZirCAD) and randomly divided into 8 groups (n = 10). Group A (control) was not exposed to contaminants. The following tests specimens were contaminated with saliva and silicone indicating paste. Group B was coated with ceramic primer, then subjected to contamination. Groups C, D, E, F, G, and H were contaminated; cleaned with water rinse, Ivoclean, air particle abrasion, hydrofluoric acid, KATANATM Cleaner and ZirCleanTM, respectively, and then coated with ceramic primer and bonded to dual cure resin cement cylinders. All the specimens were subjected to artificial aging and surviving specimens were subjected to the SBS test. For statistical analysis, ANOVA and multiple comparison methods at the 0.05 significance level were used. There was no statistically significant difference among Ivoclean (21.48 ± 2.90 MPa), air particle abrasion (21.92 ± 2.85 MPa), and the control group (24.68 ± 5.46). The application of ceramic primer before contamination did not preserve the SBS of resin cement to zirconia. Cleaning the contaminated zirconia surface with hydrofluoric acid (15.03 ± 3.63) or KATANATM Cleaner (17.27 ± 7.63) did not restore SBS to the uncontaminated state, but it was significantly higher than simply rinsing with water (12.46 ± 5.17) or the use of ZirCleanTM (11.59 ± 5.53). The bond strength of resin cement to zirconia was influenced by cleaning methods.

Polycrystalline particulates synthesized on zirconia for enhanced bioactivity: An in vitro study.

Zirconia is a promising material for dental implant with its excellent biocompatibility, good mechanical properties, and esthetic effect similar to natural teeth. To improve the bioactivity and osteogenic properties of zirconia, pre-sintered zirconia discs were divided into C, T3 , T5 , and T7 group. Group C was as control. T3 , T5 , and T7 groups were soaked in hydrofluoric acid (HF) for 30, 50, and 70 s, respectively. Then, they were placed into CaCl2 solution and heated in NaOH solution. After sintering, the samples were characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction, which confirmed the ZrO2 polycrystalline particulates in situ synthesized on the treated sample discs. The surface roughness of the treated samples was increased with the prolonged of acid treatment time (p < .05), while the three-point bending strength did not decrease significantly (p > .05). MC3T3-E1 cells were cultured on zirconia discs to evaluate the bioactivity and osteogenic effect of modified zirconia. The living&dead fluorescence staining and CCK-8 assay showed that the specimens were non-toxic and significantly promoted cell proliferation. In addition, the cell proliferation was enhanced with the increase of zirconia surface roughness. Polycrystalline particles modified zirconia were beneficial to cell spreading. After osteogenic induction, MC3T3-E1 cells inoculated on modified zirconia exhibited higher alkaline phosphatase activity, mineralization activity and up-regulated osteogenesis-related gene expression. Above all, in situ synthesized polycrystalline particulates significantly improve the biological activity of zirconia, which will promote the widespread application of zirconia implants.

Application Effect of New Material after Surface Modification of Zirconia Ceramics and Analysis of Patient Evaluation.

Objective To explore the application effect of new material after surface modification of zirconia ceramics and patient evaluation. Methods A total of 60 patients with tooth defect treated in our hospital from April 2020 to April 2021 were selected as the study subjects and randomly divided into the control group and experimental group, with 30 cases each. The patients in the control group were treated with glass-ceramics, and those in the experimental group received LiSi surface treatment, so as to compare the application effect and patients' evaluation between the two groups. Results Between the two groups, no obvious differences in surface loss, adhesive strength, and transmittance at 3 months, 6 months, and 1 year were not observed (P > 0.05); and after intervention, the score on dental aesthetics, hardness value, and occlusal force were obviously higher in the experimental group than in the control group (P < 0.001). Conclusion The new material enables forming an acid etchable coating on the zirconia surface, increases the adhesive strength, and achieves an aesthetic degree that is welcomed by the patients; meanwhile, after grinding, the edge is defect free and the tightness is higher. Further research will help to establish a better solution for patients.

3-D Surface Morphological Characterization of CAD/CAM Milled Dental Zirconia: An In Vitro Study of the Effect of Post-Fabrication Processes.

Objective: To investigate the effect on zirconia surface of the post-fabrication surface treatments on the morphological characteristics and mechanical properties of CAD/CAM milled dental zirconia specimens as well as to identify the critical parameters in the measurement of oral retention under in vitro circumstances. Method: The zirconia specimens (N = 20, n = 4) were subjected to CAD/CAM milling and divided into five groups. The specifications were: Group G1—sintered; Group G2—sintered followed by a polishing process; Group G3—sintered followed by polishing and sandblasting with alumina particles Al2O3 (110 µm); Group G4—sintered followed by sandblasting; Group G5—sintered followed by sandblasting with polishing as the end process. All the groups were subjected to Fretting wear tests, 3-D surface roughness measurements, and Vickers’s Micro hardness tests. Investigation of the phase transformation using XRD, and surface feature examination using SEM were also carried out. Additionally, one-way ANOVA, Tukey, and Pearson correlations were statistically analysed. Results: The fabrication processes had a significant effect on the performance of zirconia specimens in all the groups (p > 0.05). Specimens that underwent polishing as the last process exhibited lower surface roughness. The monoclinic phase of zirconia was observed in all the specimens before and after wear except for those in the G2 and G5 groups, where polishing was the end process. In G5, the post-wear surface properties revealed lower surface roughness and hardness. Further, the SEM and 3-D topography show grooves as seen by the dale void volume (Vvv) values; shallow valley depth (Svk); micro craters; and wear track. Conclusion: Specimens in G5 that were subjected to multistep post-fabrication process, namely sandblasting followed by polishing, yielded better results when compared to those in the other groups (G1, G2, G3, and G4). G5 with an interlayer of alumina is recommended for clinical applications due to its enhanced surface properties, mechanical properties, and low wear.

Bonding and Debonding of Zirconia Using Laser Approaches.

To describe the current findings regarding the use of lasers to enhance the bonding properties of zirconia and to enable its debonding. The PudMed database was searched for literature up to July 2021. The keywords used for zirconia surface treatment were: laser irradiation; zirconia; and bond strength. For ceramic laser debonding, the keywords were: laser irradiation; ceramic; and debonding. A total of 36 studies were included for zirconia surface treatment, and 12 for ceramic laser debonding. Nd:YAG, CO2, Er:YAG, Er,Cr:YSGG, and ultrashort lasers were used for surface treatment, whereas only Er:YAG and Er,Cr:YSGG lasers were applied to debond zirconia structures. The use of laser irradiation to improve the bonding properties of zirconia depends on the type of laser and the parameters used. Among the laser types included in this review, ultrashort lasers have shown the most promising results; however, more studies are needed to prove their superiority over the other lasers for enhancing zirconia bond strength. In terms of debonding, irradiation with different lasers was effective regardless of the ceramic type; however, well-established protocols (ie, laser irradiation time and motion, laser settings) are still needed for different thicknesses and material ceramic types.

Bonding Durability Between Zirconia and Different Types of Tooth or Implant Abutments—A Systematic Review. Part II: Outcomes of Clinical Studies

To systematically review all clinical studies focusing on the clinical outcomes of zirconia restorations bonded to different types of tooth or implant abutments and to provide practical clinical guidelines. A search was performed for English-language articles in dental journals published up to September 2020 using a combination of free-text words and MeSH terms. Studies were identified for review according to certain inclusion and exclusion criteria. A total of 2,856 studies were identified, and 24 studies were finally included. The included studies featured different types of surface pretreatment methods, primers, resin cements, tooth and implant abutments, zirconia restorations, and designs. The relatively limited number of identified studies and the heterogeneity of the extracted data did not allow for meta-analysis. Airborne-particle abrasion (APA) and tribochemical silica (TBS) APA surface pretreatment methods yielded positive clinical outcomes on zirconia/resin bonding to all types of tooth surfaces identified. Chemically activating the APA and the TBS APA zirconia surfaces with an MDP monomer-based primer, along with an MDP monomer or phosphoric ester monomer-based resin cement, seems to be a durable bonding protocol for all types of tooth surfaces identified. Skipping the surface pretreatment method step in the bonding protocol did not affect the clinical outcomes of certain types of zirconia restorations on most types of tooth or implant abutment surfaces identified. Type of resin cement seems to be a less influential factor.

Effect of air abrasion, acid etching, and aging on the shear bond strength with resin cement to 3Y-TZP zirconia

This study investigates the effect of acid etching treatment on the surface microstructure, surface roughness, and surface contact angle of zirconia and compares the effects of air abrasion, different etching times, and aging on the shear bond strength (SBS) of resin cement on the zirconia surface. 480 specimens (9 × 10 × 10 mm) were divided into as-sintered and air-abraded groups, and each group was further subdivided into six groups based on etching time (0, 3, 5, 10, 20, and 30 min). The etching solution comprised hydrofluoric acid 25%, sulfuric acid 16%, hydrogen peroxide, methyl alcohol, and purified water. The shear bond strength (SBS), scanning electron microscopy, surface roughness, contact angle, and failure mode were measured. The results indicated that the mean SBS values increased and decreased significantly when the etching times increased to 20 min and 30 min, respectively, in both groups. Further, SBS after aging was lower than that before aging in all groups. Sandblasting, etching time, and aging all showed significant effects (p < 0.001) in the three-way analysis of variance. In addition, the surface roughness increased and the contact angle decreased significantly with an increase in etching time. Thus, the acid-etching treatment induced significant changes on the zirconia surface and increased the SBS of the resin cement. The results of this in vitro study suggest that acid etching is a promising alternative for zirconia surface treatment.

Establishment of Biomimetic Soft Tissue Integration with the Surface of Zirconia Fused with Platelet-Activating Peptide.

Soft tissue sealing around zirconia (ZrO2) abutment is critical for the long-term stability of dental implants. The goal of the study is to develop a strong basal lamina (BL)-mediated epithelial attachment to ZrO2 via a novel physicochemical immobilization method. An electrophoretic fusion (EPF) method was applied to fuse a phosphonic acid (PA) linker to ZrO2 discs. Bindings of the PA linker and the following protease activated receptor 4 (PAR4) were verified by Fourier-transform infrared spectroscopy (FITR). Then, ZrO2 discs were doped in platelet-rich plasma (PRP). Platelet-derived growth factor (PDGF) was measured to assess platelet activation. PRP-doped discs were subsequently co-cultured with human gingival epithelial cells (OBA9) to evaluate establishment of basal lamina-mediated epithelial attachment. The EPF method achieved robust immobilization of the PA linker and PAR4 onto the ZrO2 surface. The resultant PAR4-coupled ZrO2 successfully induced platelet aggregation and activation. Furthermore, a BL-mediated epithelial attachment was established. The results are significant for clinical application to minimize the risk of developing peri-implant diseases.

Effect of Helium Plasma Exposure on Wettability and Shear Bond Strength between the Zirconia Core and Feldspathic Veneering Ceramic: An In Vitro Study

Introduction The present study aimed to evaluate the effect of helium plasma treatment on the wettability of zirconia surface and on the shear bond strength between the dental zirconia core and feldspathic veneering ceramic. Methods 128 zirconia specimens were prepared, polished, and then divided into four groups: control, Zr, FC, and Zr/FC. In Zr and Zr/FC groups, the zirconia blocks were treated by helium plasma for 60 s. In FC and Zr/FC, the feldspathic ceramic powder received 60 s of plasma treatment. Then, the feldspathic powder was applied on the zirconia blocks. Half of the specimens in each group were sintered in a tube furnace, and the contact angle between the zirconia core and feldspathic ceramic was measured at different time intervals. The other half were sintered in a ceramic furnace and then subjected to thermocycling. The shear bond strength was measured using a universal testing machine. The failure mode was assessed using a stereomicroscope. Data were analyzed by one-way ANOVA test, and the statistical significance was considered less than 0.05. Results There was no significant difference in the mean contact angle and the shear bond strength values of the experimental groups (P > 0.05). The mean contact angle decreased significantly in all groups over time (P < 0.001). The modes of failure were predominantly mixed in all groups. Conclusion The helium plasma applied on either dental zirconia core or feldspathic ceramic powder could not improve the zirconia surface wettability and the shear bond strength between the two ceramics.

Epithelial cell attachment and adhesion protein expression on novel in sol TiO2 coated zirconia and titanium alloy surfaces.

An adequate mucosal attachment is important when it comes to preventing peri‐implant inflammation. The aim of this study was to compare epithelial cell adhesion and adhesion protein expression on in sol TiO2‐coated and non‐coated zirconia and titanium alloy surfaces. Fifty‐six zirconia and titanium discs were cut, and half of them were coated with bioactive TiO2‐coating. To study the epithelial cell attachment, human gingival keratinocytes were cultivated on discs for 1, 3, 6, and 24 h. The cell proliferation was detected by cultivating cells for 1, 3, and 7 days. In addition, the levels of adhesion proteins laminin y2, integrin α6, β4, vinculin, and paxillin were detected with Western Blot method. Furthermore, high‐resolution imaging of the actin cytoskeleton and focal adhesion proteins was established. Longer‐term cell culture (1–7 days) revealed higher cell numbers on the coated zirconia and titanium discs compared to non‐coated discs. The difference was statistically significant (p < .05) after 24 h on coated zirconia and after 3 and 7 days on coated titanium discs compared to non‐coated discs. Clear induction in the protein levels of laminin y2 and integrin α6 were detected on both coated samples, meanwhile integrin β4 were clearly induced on coated titanium alloy. The microscope evaluation showed significantly increased cell spreading on the coated discs. According to this study, the in sol induced TiO2‐coating increases keratinocyte attachment and the expression of adhesion proteins on coated zirconia and titanium in vitro. Consequently, the coating has potential to enhance the mucosal attachment on implant surfaces.

Preparation of Calcium Phosphate Compounds on Zirconia Surfaces for Dental Implant Applications.

Titanium is widely used in medical implants despite the release of heavy metal ions over long-term use. Zirconia is very close to the color of teeth; however, its biological inertness hinders bonding with bone tissue. Alkaline treatment and coatings of calcium phosphate can be used to enhance bone regeneration adjacent to dental implants. This study examined the effects of alkaline treatment, calcium phosphate coatings, and sintering, on the physical properties of implant material. Our analysis confirmed that the calcium phosphate species were octacalcium phosphate (OCP). The sintering of calcium phosphate was shown to create B-type HAP, which is highly conducive toward the differentiation of mesenchymal stem cells (MSCs) into osteoblasts for the facilitation of bone integration. Conclusions: This study demonstrated the room-temperature fabrication of dental implants with superhydrophilic surfaces to enhance biocompatibility.

Silica deposition on zirconia via Room-Temperature Atomic Layer Deposition and bond strength to resin-based luting agent

To evaluate the effect of the controlled growth of yttria-stabilized zirconia (Y-PSZ) transformed layer and silica deposition via Room-Temperature Atomic Layer Deposition (RT-ALD) on the shear bond strength (SBS) between Y-PSZ and luting agent. Y-PSZ specimens (IPS e.max ZirCAD) with different translucencies (MO, MT, LT) were exposed to surface treatments (n = 10): control (C - no treatment), aged (A - 15 h, 134 °C, 2 bar in autoclave), blasted (B - 50 μm Al2O3), silica deposition via RT-ALD (R - 40 cycles of sequential exposure to tetramethoxysilane orthosilicate and ammonium hydroxide vapors) and aged followed by silica deposition (AR). Specimens were bonded to resin composite cylinders with a luting agent (Multilink Automix) and SBS test was performed. Failure mode and surface chemical and topographical characterization (energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy) were performed. SBS data was analyzed by two-way ANOVA and Tukey test (α = 0.05). Silica deposition resulted in SBS values similar to alumina blasting (p > .848), with no significant effect of aging (p > .664). Higher incidence of composite resin cohesive failures was observed in the R-treated specimens (MT, LT), with and without aging. SEM images showed a rougher surface for B-treated specimens, while no changes were observed for the other treatments. XPS analysis showed a nanofilm of silica deposited over the zirconia surface after silica deposition. RT-ALD was an effective technique to deposit silica on the surface of zirconia, generating bond strength results similar to alumina-blasted specimens.

Dual response of fibroblasts viability and Porphyromonas gingivalis adhesion on nanostructured zirconia abutment surfaces.

Soft tissue integration surrounding dental implant is considered as a biological barrier against the oral microorganisms and external stimuli. At present, successful soft tissues integration around implants remains a challenge. The aim of this study was to evaluate the effects of nanostructured zirconia abutment surfaces on fibroblasts viability and Porphyromonas gingivalis adhesion, which are the two main factors influencing the quality of peri-implant soft-tissue seal. Zirconia samples were made from three-dimensional gel deposition approach and divided into three groups: zirconia surfaces, zirconia film coated surfaces (CZr) and polished surfaces (PZr). The Surface properties were characterized by scanning electron microscopy, atomic force microscopy and water contact angle. The behavior of human gingival fibroblasts (HGFs) on samples, including of proliferation, morphology, gene expression and protein expression as well as collagen synthesis were assessed. Additionally, the adhesion of P. gingivalis on samples was analyzed by scanning electron microscopy and live/dead staining. CZr and PZr group significantly enhanced fibroblasts viability such as cell proliferation, cell spreading and extracellular matrix secretion, and impaired P. gingivalis adhesion. Therefore, our findings demonstrated that CZr and PZr surfaces with nano-grains or grinding grooves might be considered as the feasible zirconia abutments substrate for reinforcing HGFs response and minimizing P. gingivalis adhesion, and thereby enhance peri-implant soft-tissue integration.

Does Ultraviolet Radiation Exhibit Antimicrobial Effect against Oral Pathogens Attached on Various Dental Implant Surfaces? A Systematic Review

Background: Dental implant therapy is currently identified as the most effective treatment for edentulous patient. However, peri-implant inflammations were found to be one of the most common complications that leads to the loss and failure of dental implantation. Ultraviolet (UV) radiation has been proposed to enhance bone integration and reduce bacterial attachment. In this study, we aimed to systematically review the current evidence regarding the antimicrobial effect of UV on different dental implant surfaces. Methods: Five databases including PubMed, Scopus, Web of science, VHL, and Cochran Library were searched to retrieve relevant articles. All original reports that examined the effect of the application of UV radiation on dental implants were included in our study. Results: A total of 16 in vitro studies were included in this systematic review. Polymethyl methacrylate UV radiation has induced a significant decrease in bacterial survival in PMMA materials, with an increased effect by modification with 2.5% and 5% TiO2 nanotubes. UV-C showed a superior effect to UV-A in reducing bacterial attachment and accumulation. UV wavelength of 265 and 285 nm showed powerful bactericidal effects. UV of 365 nm for 24 h had the highest inhibition of bacterial growth in ZnO coated magnesium alloys. In UV-irradiated commercially pure titanium surfaces treated with plasma electrolytic oxidation, silver ion application, heat or alkali had shown significant higher bactericidal effect vs non-irradiated treated surfaces than the treatment with any of them alone. UVC and gamma-ray irradiation increased the hydrophilicity of zirconia surface, compared to the dry heat. Conclusion: UV radiation on Ti surfaces exhibited significant antibacterial effects demonstrated through the reduction in bacterial attachment and biofilm formation with suppression of bacterial cells growth. Combination of UV and treated surfaces with alkali, plasma electrolytic oxidation, silver ion application or heat enhance the overall photocatalytic antimicrobial effect.

In Vitro Evaluation of the Shading Effect of Various Zirconia Surface Stains on Porcelain Crowns

Human teeth display various colors under natural light. Dental restorations, such as zirconia crowns, are generally used to rehabilitate the oral function of patients with tooth loss due to trauma or natural tooth falls. However, significant improvements in the color and translucency of zirconia are required to meet the clinical needs for dental restoration. In the past, a large amount of ceramic powder has been used to improve the appearance of zirconia. However, the interface between the ceramic powder and zirconia makes them prone to falling off. Therefore, the aesthetics of zirconia crowns remains a major challenge. Recently, substantial advances have been made in the field of dental materials, as special staining agents for zirconia have been introduced as alternatives to ceramic powders. Therefore, this study tested zirconia-specific staining agents that were used to produce zirconia samples with A1 and A3 colors. A dental colorimetric plate was used as the control group to assess the staining effects of the different brands of staining agents. Meanwhile, two hypotheses were proposed: that the staining effects of these special staining agents for zirconia met the criteria for clinical application and that there was no significant difference between the different staining agents for zirconia. The results showed that the coatings of different brands of staining agents were ultrathin, with a thickness of approximately 27–78 µm. In addition, the coloring effects of the zirconia staining agents were not significantly different from those of the colorimetric plates. After staining, the zirconia samples had decreased surface roughness and contact angle values, which improved surface smoothness and cleanliness. In summary, the results support the hypothesis of this study that zirconia stains can be used as an alternative to the current fabrication methods for clinical dental restorations. We sought to identify the clinical techniques that are easier to perform and to overcome the current problem of dental technicians requiring considerable dentin space for staining. It is expected that the results of this study will be useful in clinical dental restorations.

Human Gingival Fibroblast Adhesion and Proliferation on Hydroxyapatite-Coated Zirconia Abutment Surfaces.

Applying antibacterial coatings to dental implant materials seems reasonable but can have negative influences on desired cell adhesion and healing. In this study, zirconia abutment specimens interacting with gingival tissue were used. The aim was to compare the influence of machined or coated zirconia surfaces on the adhesion and proliferation of human gingival fibroblasts (HGF-1). Surface modifications were performed using atmospheric plasma coating with hydroxyapatite, zinc, and copper. Zirconia specimens were divided into four groups: hydroxyapatite, hydroxyapatite with zinc oxide (ZnO), hydroxyapatite with copper (Cu), and an untreated machined surface. After the characterization of the surface conditions, the morphology of adhered HGF-1 was determined by fluorescence staining and subjected to statistical evaluation. The visual analysis of cell morphology by SEM showed flat, polygonal, and largely adherent fibroblast cells in the untreated group, while round to partially flat cells were recorded in the groups with hydroxyapatite, hydroxyapatite + ZnO, and hydroxyapatite + Cu. The cell membranes in the hydroxyapatite + ZnO and hydroxyapatite + Cu groups appeared porous. The results show that HGF-1 adhere and proliferate well on machined zirconia, while plasma coating with hydroxyapatite or hydroxyapatite mixtures does not lead to increased adhesion or proliferation.