Osteoblast and bone tissue response to surface modified zirconia and titanium implant materials

Development of a Coculture Model for Assessing Competing Host Mammalian Cell and Bacterial Attachment on Zirconia versus Titanium

Objectives: Coculture models are limited by bacteria rapidly outcompeting host mammalian cells for nutrients in vitro, resulting in mammalian cell death. The goal of this study was to develop a coculture model enabling survival of mammalian cells and oral bacterial species to assess their competition for growth on dental implant materials. Methods: Two early colonizing oral bacterial species, Streptococcus mutans or Actinomyces naeslundii, were grown in coculture with primary human macrophages or human gingival fibroblasts for up to 7 days on tissue-culture treated polystyrene or polished titanium and zirconia disks. Chloramphenicol was supplemented in cell culture medium at bacteriostatic concentrations to maintain stable bacterial inoculum size. Planktonic and adherent bacterial growth was assessed via spot plating while mammalian cell growth and attachment were evaluated using colorimetric metabolic assay and confocal fluorescence microscopy, respectively. Results: Macrophages and fibroblasts proliferated in the presence of S. mutans and maintained viability above 70% during coculture for up to 7 days on tissue-culture treated polystyrene and polished titanium and zirconia. In contrast, both mammalian cell types exhibited decreasing proliferation and surface coverage on titanium and zirconia over time in coculture with A. naeslundii versus control. S. mutans and A. naeslundii were maintained within an order of magnitude of seeding inoculum sizes throughout coculture. Significance: Cell culture medium supplemented with antibiotics at bacteriostatic concentrations can suppress bacterial overgrowth and facilitate mammalian cell viability in coculture model systems. Within the study's limitations, oral bacteria and mammalian cell growth in coculture are comparable on polished titanium and zirconia surfaces.

Porphyromonas gingivalis can degrade dental zirconia

OBJECTIVES

The aim of present study was to examine the effect of Porphyromonas gingivalis (P.g.) adhesion on dental zirconia by characterizing the physical and chemical properties.

METHODS

Eighty polished-sintered zirconia discs were prepared and randomly distributed to 5 groups (n = 16): Zirconia cultured with - Group 1: broth containing P.g. for - 3 days; Group 2: 7 days; Group 3: broth (alone) for - 3 days; Group 4: 7 days; and Group 5: dry discs (negative control). After experimental period, broths were analyzed for pH and Zr release with inductively coupled plasma-optical emission spectroscopy (ICP-OES). The zirconia surface was evaluated by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), water contact angle (WCA), and biaxial flexural strength (BFS).

RESULTS

The mean pH with zirconia adhesion to P.g. group was significantly higher than the broth control (p < 0.05). As per ICP-OES, Zr ion/particulate release with P.g. adhesion to zirconia were significantly higher than the controls (p < 0.05). Post-experimental incubation, no defects were found on zirconia surfaces; tetragonal phase remained constant with no transformation to monoclinic phase but lower peak intensities were identified in experimental groups. WCA of zirconia surfaces with P.g. bacteria for 3 days (12.04° ± 2.05°) and 7 days (15.09° ± 2.95°) were significantly higher than zirconia surfaces immersed with broth (only) for 3 days (7.17° ± 1.09°) and 7 days (7.55° ± 0.65°), respectively (p < 0.05). BFS values of zirconia with P.g. for 3 days (632.57 ± 119.96 MPa) and 7 days (656.17 ± 100.29 MPa) were significantly lower than zirconia incubated in broth alone (765.01 ± 20.12 MPa) conditions (p < 0.05).

SIGNIFICANCE

Under the conditions of present study, it can be concluded that P.g. adhesion on zirconia leads to structural alterations of dental zirconia further contributing to zirconia degradation.

Human cells with osteogenic potential in bone tissue research

Bone regeneration after injury or after surgical bone removal due to disease is a serious medical challenge. A variety of materials are being tested to replace a missing bone or tooth. Regeneration requires cells capable of proliferation and differentiation in bone tissue. Although there are many possible human cell types available for use as a model for each phase of this process, no cell type is ideal for each phase. Osteosarcoma cells are preferred for initial adhesion assays due to their easy cultivation and fast proliferation, but they are not suitable for subsequent differentiation testing due to their cancer origin and genetic differences from normal bone tissue. Mesenchymal stem cells are more suitable for biocompatibility testing, because they mimic natural conditions in healthy bone, but they proliferate more slowly, soon undergo senescence, and some subpopulations may exhibit weak osteodifferentiation. Primary human osteoblasts provide relevant results in evaluating the effect of biomaterials on cellular activity; however, their resources are limited for the same reasons, like for mesenchymal stem cells. This review article provides an overview of cell models for biocompatibility testing of materials used in bone tissue research.

One-Piece Zirconia Oral Implants for Single Tooth Replacement: Five-Year Results from a Prospective Cohort Study

The intention of this 5-year prospective cohort investigation was to clinically and radiographically investigate the outcomes of a one-piece zirconia implant system for single tooth replacement. Sixty-five patients received a total of 66 single-tooth implants. All implants immediately received temporary restorations and were finally restored with all-ceramic crowns. Follow-ups were performed at the prosthetic delivery, after 1, 3, and 5 years. Peri-implant and dental soft-tissue parameters were evaluated and patient-reported outcomes recorded. To monitor peri-implant bone remodelling, standardised radiographs were taken at the implant insertion and at the 1-, 3-, and 5-year follow-ups. In the course of 5 years, 14 implants were lost, resulting in a cumulative implant survival rate of 78.2%. The mean marginal bone loss from the implant insertion to the 5-year follow-up amounted to 1.12 mm. Probing depth, clinical attachment level, bleeding, and plaque index increased over time. In 91.5% of the implants, the papilla index showed levels of 1 or 2, respectively. At the end of the study, the patient satisfaction was higher compared to the pre-treatment measurements. Due to the low survival rate after five years and the noticeably high frequency of advanced bone loss observed in this study, the implant has not met the launch criteria, as it would have not been recommended for routine clinical use.

One-Piece Zirconia Oral Implants for the Support of Three-Unit Fixed Dental Prostheses: Three-Year Results from a Prospective Case Series

The objective was to investigate the clinical and radiological outcome of one-piece zirconia oral implants to support three-unit fixed dental prostheses (FDP) after three years in function. Twenty-seven patients were treated with a total of 54 implants in a one-stage surgery and immediate provisionalization. Standardized radiographs were taken at implant placement, after one year and after three years, to evaluate peri-implant bone loss. Soft-tissue parameters were also assessed. Linear mixed regression models as well as Wilcoxon Signed Rank tests were used for analyzing differences between groups and time points (p < 0.05). At the three-year evaluation, one implant was lost, resulting in a cumulative survival rate of 98.1%. The mean marginal bone loss amounted to 2.16 mm. An implant success grade I of 52% (bone loss of ≤2 mm) and success grade II of 61% (bone loss of ≤3 mm) were achieved. None of the evaluated baseline parameters affected bone loss. The survival rate of the zirconia implants was comparable to market-available titanium implants. However, an increased marginal bone loss was observed with a high peri-implantitis incidence and a resulting low implant success rate.

Surface Structure of Zirconia Implants: An Integrative Review Comparing Clinical Results with Preclinical and In Vitro Data

Background: The purpose of this review was to analyze and correlate the findings for zirconia implants in clinical, preclinical and in vitro cell studies in relation to surface structure. Methods: Electronic searches were conducted to identify clinical, preclinical and in vitro cell studies on zirconia implant surfaces. The primary outcomes were mean bone loss (MBL) for clinical studies, bone-to-implant contact (BIC) and removal torque (RT) for preclinical studies and cell spreading, cell proliferation and gene expression for cell studies. The secondary outcomes included comparisons of data found for those surfaces that were investigated in all three study types. Results: From 986 screened titles, 40 studies were included for data extraction. In clinical studies, only micro-structured surfaces were investigated. The lowest MBL was reported for sandblasted and subsequently etched surfaces, followed by a sinter and slurry treatment and sandblasted surfaces. For BIC, no clear preference of one surface structure was observable, while RT was slightly higher for micro-structured than smooth surfaces. All cell studies showed that cell spreading and cytoskeletal formation were enhanced on smooth compared with micro-structured surfaces. Conclusions: No correlation was observed for the effect of surface structure of zirconia implants within the results of clinical, preclinical and in vitro cell studies, underlining the need for standardized procedures for human, animal and in vitro studies.

Is There a Better Biomaterial for Dental Implants than Titanium?—A Review and Meta-Study Analysis

This article focuses on preclinical studies and reviews the available evidence from the literature on dental implant and abutment materials in the last decade. Specifically, different peri-implantitis materials and how surface modifications may affect the peri-implant soft-tissue seal and subsequently delay or hinder peri-implantitis are examined. This review analyzed more than 30 studies that were Randomized Controlled Trials (RCTs), Controlled Clinical Trials (CCTs), or prospective case series (CS) with at least six months of follow-up. Meta-analyses were performed to make a comparison between different implant materials (titanium vs. zirconia), including impact on bone changes, probing depth, plaque levels, and peri-implant mucosal inflammation, as well as how the properties of the implant material and surface modifications would affect the peri-implant soft-tissue seal and peri-implant health conditions. However, there was no clear evidence regarding whether titanium is better than other implant materials. Clinical evidence suggests no difference between different implant materials in peri-implant bone stability. The metal analysis offered a statistically significant advantage of zirconia implants over titanium regarding developing a favorable response to the alveolar bone.

[Effect of porous zirconia ceramics on proliferation and differentiation of osteoblasts]

OBJECTIVE

To investigate the effect of porous surface morphology of zirconia on the proliferation and differentiation of osteoblasts.

METHODS

According to different manufacturing and pore-forming methods, the zirconia specimens were divided into 4 groups, including milled sintering group (M-Ctrl), milled porous group (M-Porous), 3D printed sintering group (3D-Ctrl) and 3D printed porous group (3D-Porous). The surface micromorphology, surface roughness, contact angle and surface elements of specimens in each group were detected by scanning electron microscope (SEM), 3D laser microscope, contact angle measuring device and energy-dispersion X-ray analysis, respectively. MC3T3-E1 cells were cultured on 4 groups of zirconia discs. The cell morphology of MC3T3-E1 cells on zirconia discs was eva-luated on 1 and 7 days by SEM. The cell proliferation was detected on 1, 3 and 5 days by cell counting kit-8 (CCK-8). After osteogenic induction for 14 days, the relative mRNA expression of alkaline phosphatase (ALP), type Ⅰ collagen (Colla1), Runt-related transcription factor-2 (Runx2) and osteocalcin (OCN) in MC3T3-E1 cells were detected by real-time quantitative polymerase chain reaction.

RESULTS

The pore size [(419.72±6.99) μm] and pore depth [(560.38±8.55) μm] of 3D-Porous group were significantly larger than the pore size [(300.55±155.65) μm] and pore depth [(69.97±31.38) μm] of M-Porous group (P < 0.05). The surface of 3D-Porous group appeared with more regular round pores than that of M-Porous group. The contact angles of all the groups were less than 90°. The contact angles of 3D-Ctrl (73.83°±5.34°) and M-Porous group (72.7°±2.72°) were the largest, with no significant difference between them (P>0.05). Cells adhered inside the pores in M-Porous and 3D-Porous groups, and the proliferation activities of them were significantly higher than those of M-Ctrl and 3D-Ctrl groups after 3 and 5 days' culture (P < 0.05). After 14 days' incubation, ALP, Colla1, Runx2 and OCN mRNA expression in 3D-Porous groups were significantly lower than those of M-Ctrl and 3D-Ctrl groups (P < 0.05). Colla1, Runx2 and OCN mRNA expressions in M-Porous group were higher than those of 3D-Porous group (P < 0.05).

CONCLUSION

The porous surface morphology of zirconia can promote the proliferation and adhesion but inhibit the differentiation of MC3T3-E1 cells.

Alkali-Treated Alumina and Zirconia Powders Decorated with Hydroxyapatite for Prospective Biomedical Applications

The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.

Analysis of Surface Roughness and Three-dimensional Scanning Topography of Zirconia Implants before and after Photofunctionalization by Atomic Force Microscopy: An In Vitro Study

Aim:

To analyze surface roughness and three-dimensional (3D) scanning topography parameters of zirconia implants before and after photofunctionalization by atomic force microscopy (AFM).

Materials and Methods:

Ten commercially available zirconia implants five each in the study and control group were taken. The study group was subjected to ultraviolet (UV) radiation for 48 h using the shorter wavelength of 254 nm. After washing all the implants with 70% alcohol and drying, 3D surface topography and roughness parameters were analyzed using CSC 17 probe AFM at three different magnifications 25 μm, 50 μm, and 80 μm, respectively.

Results:

The surface topography and calculated mean amplitude, spatial, and hybrid parameters of the study group were higher than the control group (P < 0.05) in all three magnifications. Up to scale depth and peak value for the study and control group were (−0.4–0.4: −2-1) (−0.75 to 0.6:−1–1.3) (−0.75-−0.5: −1.5-1.3) for the study and control group at 25, 50, and 80 μm magnification, respectively. This indicates that photofunctionalization increased surface roughness of Zirconia implants to desirable extent.

Conclusion:

There is a definite difference in the quantitative topographic characteristics with zirconia implants being microroughned after photofunctionalization (UV treatment).

Osteoblastic response to biomaterials surfaces: Extracellular matrix proteomic analysis

The cellular response to surfaces is mediated, among other factors, by the extracellular matrix (ECM). However, little is known about the ECM proteome during mineralization. Our objective was to compare the ECM composition formed by osteoblast on different materials surfaces with proteomic analysis. Three types of biomaterial surfaces (pure titanium, anodized titanium, and zirconia) were used. Osteoblasts (MC3T3 linage) cells were cultivated on the biomaterials for 7, 14, and 21 days with the osteogenic medium. For the proteomic analysis, the specimens were washed, decellularized, and the ECM was collected. The majority of the typical ECM proteins, out of a total of 24 proteins identified, was expressed and regulated equally on the three biomaterials tested. Alpha-1,4 glucan phosphorylase was found to be down-regulated on zirconia on the seventh day, while at the same time, glycogen phosphorylase brain form was up-regulated on anodized titanium, both when compared with pure titanium (ratio: 1.06 and 0.97, respectively). And after 14 days of culture, glycogen phosphorylase brain form was downregulated on zirconia when compared with pure titanium (ratio: 0.90), suggesting the influence of material surface roughness and chemical composition on energy metabolism. Proteins related to bone development like Transforming growth factor beta-3 and Fibroblast growth factor 8 were found exclusively on pure titanium on the 21st day. Altogether, our results show a possible influence of material surfaces on the composition of ECM.

Oral Tissue Interactions and Cellular Response to Zirconia Implant-Prosthetic Components: A Critical Review

Background: Dental components manufactured with zirconia (ZrO₂) represent a significant percentage of the implant prosthetic market in dentistry. However, during the last few years, we have observed robust clinical and pre-clinical scientific investigations on zirconia both as a prosthetic and an implantable material. At the same time, we have witnessed consistent technical and manufacturing updates with regards to the applications of zirconia which appear to gradually clarify points which until recently were not well understood. Methods: This critical review evaluated the “state of the art” in relation to applications of this biomaterial in dental components and its interactions with oral tissues. Results: The physico-chemical and structural properties as well as the current surface treatment methodologies for ZrO₂ were explored. A critical investigation of the cellular response to this biomaterial was completed and the clinical implications discussed. Finally, surface treatments of ZrO₂ demonstrate that excellent osseointegration is possible and provide encouraging prospects for rapid bone adhesion. Furthermore, sophisticated surface treatment techniques and technologies are providing impressive oral soft tissue cell responses thus leading to superior biological seal. Conclusions: Dental devices manufactured from ZrO₂ are structurally and chemically stable with biocompatibility levels allowing for safe and long-term function in the oral environment.

Magnetron sputtering of strontium nanolayer on zirconia implant to enhance osteogenesis

The zirconia implants have a wide range of clinical applications, however, the biological inertness and lack of osteoinductive properties limit these applications. Strontium possesses superior biocompatibility and excellent osteogenic properties. To take advantage of these, the strontium titanate-coated zirconia implants were prepared in this study by sandblasting, acid etching, and magnetron sputtering, followed by the analysis of the biological behavior. Briefly, the zirconia sheets were polished and subjected to sandblasting and acid etching. Subsequently, a nano‑strontium titanate coating was developed on the sheets by magnetron sputtering. The specimens were characterized by scanning electron microscopy (SEM), water contact angle measurement (WCA) and EDS mapping, which confirmed the physical alternation and successful deposition of the strontium titanate coating. The in vitro experiments indicated that the majority of the filopodia and actin fibers of the MC3T3-E1 cells on SA-ZrO₂/Sr possessed an optimal osteogenic property to promote the osteogenic differentiation. Moreover, the RT-PCR results revealed that SA-ZrO₂/Sr significantly up-regulated the gene expression of Runx2, COL-1, ALP, OPG, OPN and OCN. Further, the in vivo evaluation confirmed that the SA-ZrO₂/Sr implants promoted the bone-implant osseointegration to the greatest extent as compared to SA-ZrO₂ and ZrO₂ implant. Overall, the SA-ZrO₂/Sr system was confirmed to be a promising implant, thus, providing new pathways for an effective implant design.

Interactions of Osteoprogenitor Cells with a Novel Zirconia Implant Surface

Background: This study compared the in vitro response of a mouse pre-osteoblast cell line on a novel sandblasted zirconia surface with that of titanium. Material and Methods: The MC3T3-E1 subclone 4 osteoblast precursor cell line was cultured on either sandblasted titanium (SBCpTi) or sandblasted zirconia (SBY-TZP). The surface topography was analysed by three-dimensional laser microscopy and scanning electron microscope. The wettability of the discs was also assessed. The cellular response was quantified by assessing the morphology (day 1), proliferation (day 1, 3, 5, 7, 9), viability (day 1, 9), and migration (0, 6, 24 h) assays. Results: The sandblasting surface treatment in both titanium and zirconia increased the surface roughness by rendering a defined surface topography with titanium showing more apparent nano-topography. The wettability of the two surfaces showed no significant difference. The zirconia surface resulted in improved cellular spreading and a significantly increased rate of migration compared to titanium. However, the cellular proliferation and viability noted in our experiments were not significantly different on the zirconia and titanium surfaces. Conclusions: The novel, roughened zirconia surface elicited cellular responses comparable to, or exceeding that, of titanium. Therefore, this novel zirconia surface may be an acceptable substitute for titanium as a dental implant material.

Gingival fibroblasts behavior on bioactive zirconia and titanium dental implant surfaces produced by a functionally graded technique

Adding a biological apatite layer to the implant surface enhances bone healing around the implant.

Laser Nd:YAG patterning enhance human osteoblast behavior on zirconia implants

Zirconia has been regarded as a promising material for dental implants, and Nd:YAG laser treatment has been proposed as a potential strategy to improve its bioactivity. The main aim of the present study was to evaluate the in vitro behavior of human fetal osteoblasts in contact with laser-textured zirconia implant surfaces assessing the effect of different texture patterns, spacing between laser passes and number of laser passes. Zirconia discs were produced and treated with Nd:YAG laser according to test group variables: texture (microgrooves and micropillar array), distance between surface features (25 μm, 30 μm and 35 μm), and laser passes [1, 2, 4, and 8]. Untextured sandblasted and acid-etched zirconia discs (SBAE) were used as controls. Human osteoblasts (hFOB 1.19) were cultured for 14 days on test and control samples. Morphology and cellular adhesion were observed using scanning electron microscopy (SEM). Cell viability and proliferation were evaluated at 1, 3, 7, and 14 days using a commercial resazurin-based method. Collagen type I was evaluated at 3 days using ELISA. Alkaline phosphatase (ALP) activity was evaluated at 7 days using a colorimetric enzymatic technique. Group comparisons were tested using ANOVA or Mann-Whitney test (Tukey's post hoc) using statistical software, and significance was set at p < 0.05. Cell viability and proliferation increased over time for all groups with statistically higher values for laser-textured groups when compared with control at 7 and 14 days in culture (p < 0.05). Collagen type I levels were higher for study groups (p < 0.05) when compared with control group. No statistically differences were detected for ALP activity levels between texture and control groups (p > 0.05). The results suggest that laser-machined zirconia implant surfaces may benefit biological osteoblast response. However, the type of texture, spacing at the range of 25-35 μm, and number of laser passes did not seem to be relevant variables.

Heat treatment dependent cytotoxicity of silicalite-1 films deposited on Ti-6Al-4V alloy evaluated by bone-derived cells

A silicalite-1 film (SF) deposited on Ti-6Al-4V alloy was investigated in this study as a promising coating for metallic implants. Two forms of SFs were prepared: as-synthesized SFs (SF-RT), and SFs heated up to 500 °C (SF-500) to remove the excess of template species from the SF surface. The SFs were characterized in detail by X-ray photoelectron spectroscopy (XPS), by Fourier transform infrared spectroscopy (FTIR), by scanning electron microscopy (SEM) and water contact angle measurements (WCA). Two types of bone-derived cells (hFOB 1.19 non-tumor fetal osteoblast cell line and U-2 OS osteosarcoma cell line) were used for a biocompatibility assessment. The initial adhesion of hFOB 1.19 cells, evaluated by cell numbers and cell spreading area, was better supported by SF-500 than by SF-RT. While no increase in cell membrane damage, in ROS generation and in TNF-alpha secretion of bone-derived cells grown on both SFs was found, gamma H2AX staining revealed an elevated DNA damage response of U-2 OS cells grown on heat-treated samples (SF-500). This study also discusses differences between osteosarcoma cell lines and non-tumor osteoblastic cells, stressing the importance of choosing the right cell type model.

Effect of bisphosphonate treatment of titanium surfaces on alkaline phosphatase activity in osteoblasts: a systematic review and meta-analysis

BACKGROUND

Bisphosphonate coating of dental implants is a promising tool for surface modification aiming to improve the osseointegration process and clinical outcome. The biological effects of bisphosphonates are thought to be mainly associated with osteoclasts inhibition, whereas their effects on osteoblast function are unclear. A potential of bisphosphonate coated surfaces to stimulate osteoblast differentiation was investigated by several in vitro studies with contradictory results. The purpose of this systematic review and meta-analysis was to evaluate the effect of bisphosphonate coated implant surfaces on alkaline phosphatase activity in osteoblasts.

METHODS

In vitro studies that assessed alkaline phosphatase activity in osteoblasts following cell culture on bisphosphonate coated titanium surfaces were searched in electronic databases PubMed/MEDLINE, Scopus and ISI Web of Science. Animal studies and clinical trials were excluded. The literature search was restricted to articles written in English and published up to August 2019. Publication bias was assessed by the construction of funnel plots.

RESULTS

Eleven studies met the inclusion criteria. Meta-analysis showed that coating of titanium surfaces with bisphosphonates increases alkaline phosphatase activity in osteoblasts after 3 days (n = 1), 7 (n = 7), 14 (n = 6) and 21 (n = 3) days. (7 days beta coefficient = 1.363, p-value = 0.001; 14 days beta coefficient = 1.325, p-value < 0.001; 21 days beta coefficient = 1.152, p-value = 0.159).

CONCLUSIONS

The meta-analysis suggests that bisphosphonate coatings of titanium implant surfaces may have beneficial effects on osteogenic behaviour of osteoblasts grown on titanium surfaces in vitro. Further studies are required to assess to which extent bisphosphonates coating might improve osseointegration in clinical situations.

Hard and soft tissue evaluation of titanium dental implants and abutments with nanotubes in canines

BACKGROUND

Little is known regarding the interaction of dental implant surface nanotubes and oral soft and hard tissues. The purpose of this study was to evaluate both histologically and radiographically the qualitative and quantitative effects of dental implant surface nanotubes on hard and soft tissue in a canine model.

METHODS

Three subgroups consisting of a combination of test and control implants and abutments (Group A: control implant/control abutment, Group B: control implant/test abutment: Group C: test implant/test abutment) were placed in edentulous mandibles of six large-breed canines. Implants and abutments were placed on one side at baseline, and on the opposite side of the mandible at week 10; sacrifice occurred at week 12. Quantitative and qualitative analyses were used to measure newly formed hard and soft tissues histologically and radiographically.

RESULTS

The mean radiographic change in marginal bone level from weeks 0 to 12 between implant groups was not statistically significant (P > 0.05). Mean soft tissue contact (junctional epithelium + connective tissue) for Groups A, B, and C were 2.29, 2.33, and 2.31 mm, respectively, with no statistically significant difference (P > 0.05) between the groups. All connective tissue fibers were oriented parallel to the abutment regardless of surface treatment.

CONCLUSIONS

The findings of this study suggest that healing of hard and soft tissues around implants and abutments is similar when comparing grit-blasted surfaces to machined, turned surfaces with nanotubes. Both resulted in similar soft tissue contact values, as well as connective tissue fiber orientation.

The summary of the most important cell-biomaterial interactions that need to be considered during in vitro biocompatibility testing of bone scaffolds for tissue engineering applications

Tissue engineered products (TEPs), which mean biomaterials containing either cells or growth factors or both cells and growth factors, may be used as an alternative to the autografts taken directly from the bone of the patients. Nevertheless, the use of TEPs needs much more understanding of biointeractions between biomaterials and eukaryotic cells. Despite the possibility of the use of in vitro cellular models for initial evaluation of the host response to the implanted biomaterial, it is observed that most researchers use cell cultures only for the evaluation of cytotoxicity and cell proliferation on the biomaterial surface, and then they proceed to animal models and in vivo testing of bone implants without fully utilizing the scientific potential of in vitro models. In this review, the most important biointeractions between eukaryotic cells and biomaterials were discussed, indicating molecular mechanisms of cell adhesion, proliferation, and biomaterial-induced activation of immune cells. The article also describes types of cellular models which are commonly used for biomaterial testing and highlights the possibilities and drawbacks of in vitro tests for biocompatibility evaluation of novel scaffolds. Finally, the review summarizes recent findings concerning the use of adult mesenchymal stem cells for TEP generation and compares the potential of bone marrow- and adipose tissue-derived stem cells in regenerative medicine applications.

Surface Modification Techniques for Zirconia-Based Bioceramics: A Review

Zirconia is gaining interest as a ceramic biomaterial for implant applications due to its biocompatibility and desirable mechanical properties. At present, zirconia-based bioceramics is often seen in the applications of hip replacement and dental implants. This article briefly reviews different surface modification techniques that have been applied to zirconia such as polishing, sandblasting, acid etching, biofunctionalization, coating, laser treatment, and ultraviolet light treatment. The potential of surface modification to make zirconia a successful implant material in the future is highly dependent on the establishment of successful in vitro and in vivo studies. Hence, further effort should be made in order to deepen the understanding of tissue response to implant and tissue regeneration process.

Multi-compartment scaffold fabricated via 3D-printing as in vitro co-culture osteogenic model

The development of in vitro 3D models to get insights into the mechanisms of bone regeneration could accelerate the translation of experimental findings to the clinic, reducing costs and duration of experiments. This work explores the design and manufacturing of multi-compartments structures in poly(ε-caprolactone) (PCL) 3D-printed by Fused Filament Fabrication technique. The construct was designed with interconnected stalls to host stem cells and endothelial cells. Cells were encapsulated within an optimised gellan gum (GG)-based hydrogel matrix, crosslinked using strontium (Sr2+) ions to exploit its bioactivity and finally, assembled within compartments with different sizes. Calcium (Ca2+)-crosslinked gels were also used as control for comparison of Sr2+ osteogenic effect. The results obtained demonstrated that Sr2+ ions were successfully diffused within the hydrogel matrix and increased the hydrogel matrix strength properties under compressive load. The in vitro co-culture of human-TERT mesenchymal stem cells (TERT- hMSCs) and human umbilical vein endothelial cells (HUVECs), encapsulated within Sr2+ ions containing GG-hydrogels and inter-connected by compartmentalised scaffolds under osteogenic conditions, enhanced cell viability and supported osteogenesis, with a significant increase of alkaline phosphatase activity, osteopontin and osteocalcin respect with the Ca2+-crosslinked GG-PCL scaffolds. These outcomes demonstrate that the design and manufacturing of compartmentalised co-culture of TERT-hMSCs and HUVEC populations enables an effective system to study and promote osteogenesis.

Current status of zirconia implants in dentistry: preclinical tests

PURPOSE

This systematic review aimed to provide an overview of zirconia implants as well as regarding the outcome of the implant-restorative complex in preclinical studies.

STUDY SELECTION

An electronic search of the literature prior to July 2017 was performed to identify all articles related to preclinical research on zirconia implants. The search was conducted using MEDLINE (National Library of Medicine) and PubMed without restrictions concerning the date of publication. The search terminology included: zirconia implant, osseointegration, bone-to-implant contact, soft tissue, histology, histomorphometry, surface modification, surface roughness, surface characteristics, and restoration (connecting multiple keywords with AND, OR).

RESULTS

Fifty-seven studies were finally selected from an initial yield of 654 titles, and the data were extracted. The identified preclinical studies focused on several aspects related to zirconia implants, namely biocompatibility, mechanical properties, implant design, osseointegration capacity, soft tissue response, and restorative options. Due to heterogeneity of the studies, a meta-analysis was not possible. The most frequently used zirconia material for the fabrication of implants is yttria-stabilized tetragonal zirconia polycrystal. The resistance-to-fracture for zirconia implants ranged between 516-2044N. The mostly investigated parameter was osseointegration, which is compared to that of titanium. A lack of evidence was found with other parameters.

CONCLUSIONS

Due to its good biocompatibility as well as favorable physical and mechanical properties, zirconia implants are a potential alternative to titanium implants. However, knowledge regarding the implant-restorative complex and related aspects is still immature to recommend its application for daily practice.

Biological and osseointegration capabilities of hierarchically (meso-/micro-/nano-scale) roughened zirconia

PURPOSE

Zirconia is a potential alternative to titanium for dental and orthopedic implants. Here we report the biological and bone integration capabilities of a new zirconia surface with distinct morphology at the meso-, micro-, and nano-scales.

METHODS

Machine-smooth and roughened zirconia disks were prepared from yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), with rough zirconia created by solid-state laser sculpting. Morphology of the surfaces was analyzed by three-dimensional imaging and profiling. Rat femur-derived bone marrow cells were cultured on zirconia disks. Zirconia implants were placed in rat femurs and the strength of osseointegration was evaluated by biomechanical push-in test.

RESULTS

The rough zirconia surface was characterized by meso-scale (50 µm wide, 6-8 µm deep) grooves, micro-scale (1-10 µm wide, 0.1-3 µm deep) valleys, and nano-scale (10-400 nm wide, 10-300 nm high) nodules, whereas the machined surface was flat and uniform. The average roughness (Ra) of rough zirconia was five times greater than that of machined zirconia. The expression of bone-related genes such as collagen I, osteopontin, osteocalcin, and BMP-2 was 7-25 times upregulated in osteoblasts on rough zirconia at the early stage of culture. The number of attached cells and rate of proliferation were similar between machined and rough zirconia. The strength of osseointegration for rough zirconia was twice that of machined zirconia at weeks two and four of healing, with evidence of mineralized tissue persisting around rough zirconia implants as visualized by electron microscopy and elemental analysis.

CONCLUSION

This unique meso-/micro-/nano-scale rough zirconia showed a remarkable increase in osseointegration compared to machine-smooth zirconia associated with accelerated differentiation of osteoblasts. Cell attachment and proliferation were not compromised on rough zirconia unlike on rough titanium. This is the first report introducing a rough zirconia surface with distinct hierarchical morphology and providing an effective strategy to improve and develop zirconia implants.

Biomimetic surface functionalization of clinically relevant metals used as orthopaedic and dental implants

Titanium and its alloys or tantalum (Ta) are materials used in orthopaedic and dental implants due to their excellent mechanical properties and biocompatibility. However, their bioactivity and osteoconductivity is low. With a view to improving the bioactivity of these materials we hypothesised that the surface of Ta and TiAl6V4 can be functionalised with biomimetic, amorphous nano-sized calcium phosphate (CaP) apatite-like deposits, instead of creating uniform coatings, which can lead to flaking, delamination and poor adherence. We used Ta and TiAl6V4 metal discs with smooth and rough surfaces. Amorphous CaP apatite-like particles were deposited on the different surfaces by a biomimetic rapid two-step soaking method using concentrated simulated body fluid (SBF) solutions without a pre-treatment of the metal surfaces to induce CaP deposition. Immersion times in the second SBF solution of 48 and 18 h for Ta and TiAl6V4 respectively produced CaP deposits composed of amorphous globular nano-sized particles that also contained Mg, C and O. Longer immersion times produced more uniform coatings as well as an undesired calcite mineral phase. Prediction of in vivo behaviour by immersion in regular SBF showed that the obtained CaP deposits would act as a catalyst to rapidly form a Ca deficient CaP layer that also incorporates Mg. The amorphous CaP apatite-like deposits promoted initial attachment, proliferation and osteogenic differentiation of bone marrow derived mesenchymal stem cells. Finally, we used our method to functionalise 3D porous structures of titanium alloy made by selective laser sintering. Our study uses a novel and cost-effective approach to functionalise clinically relevant metal surfaces in order to increase the bioactivity of these materials, which could improve their clinical performance.

Osseointegration of zirconia dental implants in animal investigations: A systematic review and meta-analysis

OBJECTIVE

To determine the osseointegration rate of zirconium dioxide (ZrO₂) dental implants in preclinical investigations.

DATA

Data on the osseointegration rate was extracted considering the bone to implant contact (BIC), removal torque analysis (RTQ) and push-in tests. Meta analyses were conducted using multilevel multivariable mixed-effects linear regression models. The Šidák method was used in case of multiple testing.

SOURCES

An electronic screening of the literature (MEDLINE/Pubmed, Cochrane Library and Embase) and a supplementary manual search were performed. Animal investigations with a minimum sample size of 3 units evaluating implants made of zirconia (ZrO₂) or its composites (ZrO₂>50vol.%) were included.

STUDY SELECTION

The search provided 4577 articles, and finally 54 investigations were included and analyzed. Fifty-two studies included implants made from zirconia, 4 zirconia composite implants and 37 titanium implants. In total, 3435 implants were installed in 954 animals.

CONCLUSIONS

No significant influence of the evaluated bulk materials on the outcomes of interest could be detected. When comparing different animal models, significant differences for the evaluated variables could be found. These results might be of interest for the design of further animal investigations.

Surface characteristics of dental implants: A review

OBJECTIVES

During the last decades, several changes of paradigm have modified our view on how biomaterials' surface characteristics influence the bioresponse. After becoming aware of the role of a certain microroughness for improved cellular contact and osseointegration of dental titanium implants, the likewise important role of surface energy and wettability was increasingly strengthened. Very recently, synergistic effects of nanoscaled topographical features and hydrophilicity at the implant/bone interface have been reported.

METHODS

Questions arise about which surface roughness and wetting data are capable to predict the bioresponse and, ultimately, the clinical performance. Current methods and approaches applied for topographical, wetting and surface energetic analyses are highlighted. Current knowledge of possible mechanisms explaining the influence of roughness and hydrophilicity at the biological interface is presented.

RESULTS

Most marketed and experimental surfaces are based on commonly available additive or subtractive surface modifying methods such as blasting, etching or anodizing. Different height, spatial, hybrid and functional roughness parameters have been identified as possible candidates able to predict the outcome at hard and soft tissue interfaces. Likewise, hydrophilic implants have been proven to improve the initial blood contact, to support the wound healing and thereby accelerating the osseointegration.

SIGNIFICANCE

There is clear relevance for the influence of topographical and wetting characteristics on a macromolecular and cellular level at endosseous implant/biosystem interfaces. However, we are still far away from designing sophisticated implant surfaces with the best possible, selective functionality for each specific tissue or cavity interface. Firstly, because our knowledge of the respective surface related reactions is at best fragmentary. Secondly, because manufacturing of multi-scaled complex surfaces including distinct nanotopographies, wetting properties, and stable cleanliness is still a technical challenge and far away from being reproducibly transferred to implant surfaces.

Mesenchymal stromal cell and osteoblast responses to oxidized titanium surfaces pre-treated with λ = 808 nm GaAlAs diode laser or chlorhexidine: in vitro study

Preservation of implant biocompatibility following peri-implantitis treatments is a crucial issue in odontostomatological practice, being closely linked to implant re-osseointegration. Our aim was to assess the responses of osteoblast-like Saos2 cells and adult human bone marrow-mesenchymal stromal cells (MSCs) to oxidized titanium surfaces (TiUnite^®, TiU) pre-treated with a 808 ± 10 nm GaAlAs diode laser operating in non-contact mode, in continuous (2 W, 400 J/cm²; CW) or pulsed (20 kHz, 7 μs, 0.44 W, 88 J/cm²; PW) wave, previously demonstrated to have a strong bactericidal effect and proposed as optional treatment for peri-implantitis. The biocompatibility of TiU surfaces pre-treated with chlorhexidine digluconate (CHX) was also evaluated. In particular, in order to mimic the in vivo approach, TiU surfaces were pre-treated with CHX (0.2%, 5 min); CHX and rinse; and CHX, rinse and air drying. In some experiments, the cells were cultured on untreated TiU before being exposed to CHX. Cell viability (MTS assay), proliferation (EdU incorporation assay; Ki67 confocal immunofluorescence analysis), adhesion (morphological analysis of actin cytoskeleton organization), and osteogenic differentiation (osteopontin confocal immunofluorescence analysis; mineralized bone-like nodule formation) analyses were performed. CHX resulted cytotoxic in all experimental conditions. Diode laser irradiation preserved TiU surface biocompatibility. Notably, laser treatment appeared even to improve the known osteoconductive properties of TiU surfaces. Within the limitations of an in vitro experimentation, this study contributes to provide additional experimental basis to support the potential use of 808 ± 10 nm GaAlAs diode laser at the indicated irradiation setting, in the treatment of peri-implantitis and to discourage the use of CHX.

Corrosion behavior of surface modifications on titanium dental implant. In situ bacteria monitoring by electrochemical techniques

The effects of surface modifications and bacteria on the corrosion behavior of titanium have been studied. Five surface modifications were analyzed: two acid etchings (op V, op N), acid etching + anodic oxidation (op NT), sandblasting + acid etching (SLA), and machined surfaces (mach). The corrosion behavior of the surface modifications was evaluated by following the standard ANSI/AAMI/ISO 10993-15:2000. Cyclic potentiodynamic and potentiostatic anodic polarization tests and ion release by ICP-OES after immersion for 7 days in 0.9% NaCl were carried out. Microbiologically induced corrosion (MIC) of low and high roughness (mach, op V) was assessed in situ by electrochemical techniques. Streptococcus mutans bacteria were resuspended in PBS at a concentration of 3 × 10⁸ bacteria mL^-1 and maintained at 37°C. MIC was measured through the open circuit potential, E_oc , and electrochemical impedance spectroscopy from 2 to 28 days. Potentiodynamic curves showed the typical passive behavior for all the surface modifications. The titanium ion release after immersion was below 3 ppb. In situ bacteria monitoring showed the decrease in E_oc from -0.065 (SD 0.067) V_{vs. Ag/AgCl} in mach and -0.115 (SD 0.084) V_{vs. Ag/AgCl} in op V, to -0.333 (SD 0.147) V_{vs. Ag/AgCl} in mach and -0.263 (SD 0.005) V_{vs. Ag/AgCl} in op V, after 2 and 28 days, respectively. A reduction of the oxide film resistance, especially in op V (54 MΩ cm² and 6 MΩ cm² , after 2 and 28 days, respectively) could be seen. Streptococcus mutans negatively affected the corrosion resistance of titanium. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 997-1009, 2018.

Multilayer Nanoscale Encapsulation of Biofunctional Peptides to Enhance Bone Tissue Regeneration In Vivo

Bone tissue healing is a dynamic process that is initiated by the recruitment of osteoprogenitor cells followed by their migration, proliferation, differentiation, and development of a mineralizing extracellular matrix. The work aims to manufacture a functionalized porous membrane that stimulates early events in bone healing for initiating a regenerative cascade. Layer-by-layer (LbL) assembly is proposed to modify the surface of osteoconductive electrospun meshes, based on poly(lactic-co-glycolic acid) and nanohydroxyapatite, by using poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) as polyelectrolytes. Molecular cues are incorporated by grafting peptide fragments into the discrete nanolayers. KRSR (lysine-arginine-serine-arginine) sequence is grafted to enhance cell adhesion and proliferation, NSPVNSKIPKACCVPTELSAI to guide bone marrow mesenchymal stem cells differentiation in osteoblasts, and FHRRIKA (phenylalanine-histidine-arginine-arginine-isoleucine-lysine-alanine) to improve mineralization matrix formation. Scanning electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy demonstrate the successful surface functionalization. Furthermore, the peptide incorporation enhances cellular processes, with good viability and significant increase of alkaline phosphatase activity, osteopontin, and osteocalcin. The functionalized membrane induces a favorable in vivo response after implantation for four weeks in nonhealing rat calvarial defect model. It is concluded that the multilayer nanoencapsulation of biofunctional peptides using LbL approach has significant potential as innovative manufacturing technique to improve bone regeneration in orthopedic and craniofacial medical devices.

Success Rate of Two-Piece Zirconia Implants: A Retrospective Statistical Analysis

PURPOSE

About 10 years ago, one-piece zirconia implants were introduced to dentistry. The aim of the study was to evaluate the clinical success of two-piece zirconia implants regarding osseointegration using the manufacturers' warranty data.

MATERIALS AND METHODS

Over a period of 4 years (2010-2014), the data of warranty replacements of 15,255 sold Zeramex implants were evaluated retrospectively and blinded.

RESULTS

Three hundred forty-seven (2.2%) nonosseointegrated implants were sent back. Zeramex T showed an average success rate of 96.7%, whereas Zeralock implants exhibited an average success rate of 98.5%. Furthermore, Zeramex Plus implants exhibit an average success rate of 99.4% within the investigated period. Assuming, that 2% of the failed implants were unreturned, the above-mentioned values show no changes. Assuming 5% (10%) of unreturned nonosseointegrated implants, the average success rate of Zeramex T decreases from 96.7% to 96.6% (96.4%) and of Zeralock from 98.5% to 98.4% (98.4%), respectively. The success rate of Zeramex Plus implants remains unchanged at 99.4%.

CONCLUSION

The results of this study imply that two-piece zirconia implants show competitive success rates, improved from >96.7% to >98.5% over three product generations.

Preparation and 68Ga-radiolabeling of porous zirconia nanoparticle platform for PET/CT-imaging guided drug delivery

This paper describes the preparation of gallium-68 (⁶⁸Ga) isotope labeled porous zirconia (ZrO₂) nanoparticle (NP) platform of nearly 100nm diameter and its first pharmacokinetic and biodistribution evaluation accomplished with a microPET/CT (μPet/CT) imaging system. Objectives of the investigations were to provide a nanoparticle platform which can be suitable for specific delivery of various therapeutic drugs using surface attached specific molecules as triggering agents, and at the same time, suitable for positron emission tomography (PET) tracing of the prospective drug delivery process. Radiolabeling was accomplished using DOTA bifunctional chelator. DOTA was successfully adsorbed onto the surface of nanoparticles, while the ⁶⁸Ga-radiolabeling method proved to be simple and effective. In the course of biodistribution studies, the ⁶⁸Ga-labeled DOTA-ZrNPs showed proper radiolabeling stability in their original suspension and in blood serum. μPet/CT imaging studies confirmed a RES-biodistribution profile indicating stable nano-sized labeled particles in vivo. Results proved that the new method offers the opportunity to examine further specifically targeted and drug payload carrier variants of zirconia NP systems using PET/CT imaging.

Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies

Implant surfaces are continuously being improved to achieve faster osseointegration and a stronger bone to implant interface. This review will present the various implant surfaces, the parameters for implant surface characterization, and the corresponding in vitro human cell-based studies determining the strength and quality of the bone-implant contact. These in vitro cell-based studies are the basis for animal and clinical studies and are the prelude to further reviews on how these surfaces would perform when subjected to the oral environment and functional loading.

The Effect of UV Treatment on the Osteoconductive Capacity of Zirconia-Based Materials

Objective: Improvements in the bioactivity of zirconia implants for accelerated healing and reduced morbidity have been of continuing interest in the fields of dentistry and orthopedic surgery. The aim of the present study was to examine whether UV treatment increases the osteoconductivity of zirconia-based materials. Materials and Methods: Smooth and rough zirconia-based disks and cylindrical implants were treated with UV light for 15 min and subsequently placed in rat femurs. Surface characterization was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Results: In vivo histomorphometry revealed that the percentage of bone-implant contact and the amount of bone volume, formed around UV-treated implants, increased by 3–7-fold for smooth surfaces and by 1.4–1.7-fold for rough surfaces compared to non-treated specimens at Weeks 2 and 4 of healing, respectively. A biomechanical test showed that UV treatment accelerated the establishment of bone-zirconia integration and enhanced the strength of the bone-implant interface by two-fold. Additionally, surface characterization of the zirconia disks revealed that UV treatment decreased the amount of surface carbon and converted the hydrophilic status from hydrophobic to superhydrophilic. Conclusions: This study indicates that UV light pretreatment enhances the osteoconductive capacity of zirconia-based materials.

Lu-177-Labeled Zirconia Particles for Radiation Synovectomy

The present article describes the preparation of β-emitter lutetium-177-labeled zirconia colloid and its preliminary physicochemical and biological evaluation of suitability for local radionuclide therapy. The new (177)Lu-labeled therapeutic radiopharmaceutical candidate was based on the synthesis mode of a previously described zirconia nanoparticle system. The size and shape of the developed radiopharmaceutical compound were observed through a scanning electron microscope and dynamic light scattering methods. The radiocolloid had a 1.7 μm mean diameter and showed high in vitro radiochemical and colloid size stability at room temperature and during the blood sera stability test. After the in vitro characterizations, the product was investigated in the course of the treatment of a spontaneously diseased dog veterinary patient's hock joint completed with single-photon emission computed tomography (SPECT) imaging follow-up measurements and a dual-isotope SPECT imaging tests with conventional (99m)Tc-methanediphosphonic acid bone scintigraphy. In the treated dog, no clinical side-effects or signs of histopathological changes of the joints were recorded during the treatment. SPECT follow-up studies clearly and conspicuously showed the localization of the (177)Lu-labeled colloid in the hock joint as well as detectable but negligible leakages of the radiocolloid in the nearest lymph node. On the basis of biological follow-up tests, the orthopedic team assumed that the (177)Lu-labeled zirconia colloid-based local radionuclide therapy resulted in a significant and long-term improvement in clinical signs of the patient without any remarkable side-effects.

Titanium and Zirconium Levels Are Associated with Changes in MicroRNAs Expression: Results from a Human Cross-Sectional Study on Obese Population

Objectives

In this study on 90 individuals we aimed at evaluating the microRNAs (miRNAs) expression profile associated with personal levels of Titanium (Ti) and Zirconium (Zr) traced in hair samples. Ti and Zr materials are broadly used for dental implants but the biological reactions triggered by a long term presence of these materials in the oral cavity still need to be assessed. MiRNAs are mechanisms that need to be investigated as they play a fundamental role in the control of gene expression following external stimuli and contribute to a wide range of pathophysiological processes.

Methods

Using the TaqMan^® Low-Density Array, we assessed the expression levels of 377 human miRNAs in peripheral blood of 90 subjects. Hair samples were analyzed for Ti and Zr content using Inductively Coupled Plasma-Mass Spectrometry. We performed multivariable regression analysis to investigate the effects of Ti and Zr exposure on miRNA expression levels. We used the Ingenuity Pathway Analysis (IPA) software to explore the functional role of the investigated miRNAs and the related target genes.

Results

Seven miRNAs (miR-99b, miR-142-5p, miR-152, miR-193a-5p, miR-323-3p, miR-335, miR-494) resulted specifically associated with Zr levels. The functional target analysis showed that miRNAs are involved in mechanisms such as inflammation, skeletal and connective tissue disorders.

Conclusions

Our data suggest that Zr is more bioactive than Ti and show that miRNAs are relevant molecular mechanisms sensitive to Zr exposure.

Bone tissue response to experimental zirconia implants

OBJECTIVES

This study seeks to assess the bone tissue response at experimental zirconia implants in comparison with titanium implants by means of descriptive histology and histomorphometry in a dog model.

MATERIALS AND METHODS

Experimental zirconia implants with three different surface roughnesses (Z1 < Z2 < Z3) and conventional sandblasted large grit and acid-etched titanium implants were inserted bilaterally in the lower jaws of nine beagle dogs. Tissue biopsies were obtained after 3 and 14 days and 10 weeks of transmucosal healing. The tissue response was investigated by assessing new, old, and total bone-to-implant contact (nBIC, oBIC, and tBIC).

RESULTS

After 3 days, histological specimens of all groups showed an intimate contact between the implant threads and pristine bone (tBIC: Ti 42.3 % > Z2 30.1 % > Z3 28.9 % > Z1 25.1 %, p > 0.05, unpaired t test, respectively). A provisional matrix was evident at all implant surfaces. At 14 days, percentages of BIC increased in all groups (tBIC: Ti 62.1 % > Z3 69.2 % < Z2 44.4 % > Z1 42.3 %; nBIC: Z3 58.9 % > Ti 52.2 % > Z2 35.1 % > Z1 32.5 %). Two implants, one of group Z1 and one of group Z2, were lost. At 10 weeks, 13 of 18 zirconia implants were lost, equally distributed between all three surface modifications. The remaining implants revealed increased BIC values (tBIC: Z3 69.5 % > Ti 58.5 % > Z1 49.7 % > Z2 37.1 %; nBIC: Z3 57.2 % > Ti 46.5 % > Z1 32.3 % > Z2 29.3 %). Histomorphometrical analysis showed comparable mean BIC values in all groups at all healing periods without showing statistical differences (p > 0.05, unpaired t test, respectively).

CONCLUSION

The bone tissue response throughout the healing periods was characterized by a constant bone remodeling accompanied by resorption of old bone in favor of new bone formation at both titanium and zirconia implants. Surface roughness had a positive effect on BIC, although not showing statistical significance. Due to the poor survival rate, the experimental zirconia implants investigated may not be suitable for clinical use.

CLINICAL RELEVANCE

Zirconia has been introduced as an alternative biomaterial for dental implants. A profound knowledge about the bone tissue response at zirconia implant surfaces is necessary as it plays an important role for proper osseointegration and long-term stability.

Characteristics and in vitro response of thin hydroxyapatite-titania films produced by plasma electrolytic oxidation of Ti alloys in electrolytes with particle additions

Enhanced incorporation of hydroxyapatite nanoparticles in porous titania coating formed by plasma electrolytic oxidation significantly increases surface osteogenic activity.

The enhancement of the biological properties of Ti by surface doping with hydroxyapatite (HA) is of great significance, especially for orthodontic applications. This study addressed the effects of HA particle size in the electrolyte suspension on the characteristics and biological properties of thin titania-based coatings produced on Ti–6Al–4V alloy by plasma electrolytic oxidation (PEO). Detailed morphological investigation of the coatings formed by a single-stage PEO process with two-step control of the electrical parameters was performed using the Minkowski functionals approach. The surface chemistry was studied by glow discharge optical emission spectroscopy and Fourier transform infrared spectroscopy, whereas mechanical properties were evaluated using scratch tests. The biological assessment included in vitro evaluation of the coating bioactivity in simulated body fluid (SBF) as well as studies of spreading, proliferation and osteoblastic differentiation of MC3T3-E1 cells. The results demonstrated that both HA micro- and nanoparticles were successfully incorporated in the coatings but had different effects on their surface morphology and elemental distributions. The micro-particles formed an irregular surface morphology featuring interpenetrated networks of fine pores and coating material, whereas the nanoparticles penetrated deeper into the coating matrix which retained major morphological features of the porous TiO₂ coating. All coatings suffered cohesive failure in scratch tests, but no adhesive failure was observed; moreover doping with HA increased the coating scratch resistance. In vitro tests in SBF revealed enhanced bioactivity of both HA-doped PEO coatings; furthermore, the cell proliferation/morphometric tests showed their good biocompatibility. Fluorescence microscopy revealed a well-organised actin cytoskeleton and focal adhesions in MC3T3-E1 cells cultivated on these substrates. The cell alkaline phosphatase activity in the presence of ascorbic acid and β-glycerophosphate was significantly increased, especially in HA nanoparticle-doped coatings.

Silica@zirconia@poly(malic acid) nanoparticles: promising nanocarriers for theranostic applications

Nanocarriers designed, synthesized and characterized for the targeted delivery of diagnostic and therapeutic ^99mTc to folate-overexpressing tumors.

Zirconia in dental implantology: A review

Background:

Titanium has been the most popular material of choice for dental implantology over the past few decades. Its properties have been found to be most suitable for the success of implant treatment. But recently, zirconia is slowly emerging as one of the materials which might replace the gold standard of dental implant, i.e., titanium.

Materials and Methods:

Literature was searched to retrieve information about zirconia dental implant and studies were critically analyzed. PubMed database was searched for information about zirconia dental implant regarding mechanical properties, osseointegration, surface roughness, biocompatibility, and soft tissue health around it. The literature search was limited to English language articles published from 1975 to 2015.

Results:

A total of 45 papers met the inclusion criteria for this review, among the relevant search in the database.

Conclusion:

Literature search showed that some of the properties of zirconia seem to be suitable for making it an ideal dental implant, such as biocompatibility, osseointegration, favourable soft tissue response and aesthetics due to light transmission and its color. At the same time, some studies also point out its drawbacks. It was also found that most of the studies on zirconia dental implants are short-term studies and there is a need for more long-term clinical trials to prove that zirconia is worth enough to replace titanium as a biomaterial in dental implantology.

Osteoblast response to zirconia surfaces with different topographies

Zirconia-3 mol% yttria ceramics were prepared with as-sintered, abraded, polished, and porous surfaces in order to explore the attachment, proliferation and differentiation of osteoblast-like cells. After modification, all surfaces were heated to 600°C to extinguish traces of organic contamination. All surfaces supported cell attachment, proliferation and differentiation but the surfaces with grain boundary grooves or abraded grooves provided conditions for enhanced initial cell attachment. Nevertheless, overall cell proliferation and total DNA were highest on the polished surface. Zirconia sintered at a lower temperature (1300°C vs. 1450°C) had open porosity and presented reduced proliferation as assessed by alamarBlue™ assay, possibly because the openness of the pores prevented cells developing a local microenvironment. All cells retained the typical polygonal morphology of osteoblast-like cells with variations attributable to the underlying surface notably alignment along the grooves of the abraded surface.

Inherently fluorescent and porous zirconia colloids: preparation, characterization and drug adsorption studies

Adsorption of drug molecules onto the zirconia surface.

Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts

In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium.