Zirconia versus titanium in dentistry: A review

Silk fibroin microgrooved zirconia surfaces improve connective tissue sealing through mediating glycolysis of fibroblasts

The use of zirconia has significantly enhanced the aesthetic outcomes of implant restorations. However, peri-implantitis remains a challenge to long-term functionality of implants. Unlike the perpendicularly arranged collagen fibers in periodontal tissue, those in peri-implant tissue lie parallel to the abutment surface and contain fewer fibroblasts, making them more prone to inflammation. Studies have shown that microgroove structures on implant abutments could improve surrounding soft tissue structure. However, creating precise microgrooves on zirconia without compromising its mechanical integrity is technically challenging. In this study, we applied inkjet printing, an additive manufacturing technique, to create stable silk fibroin microgroove (SFMG) coatings of various dimensions on zirconia substrates. SFMG significantly improved the hydrophilicity of zirconia and showed good physical and chemical stability. The SFMG with 90 μm interval and 10 μm depth was optimal in promoting the proliferation, alignment, and extracellular matrix production of human gingival fibroblasts (HGFs). Moreover, the in vitro results revealed that SFMG stimulated key glycolytic enzyme gene expression in HGFs via the PI3K-AKT-mTOR pathway. Additionally, the in vivo results of histological staining of peri-abutments soft tissue showed that SFMG promoted the vertical alignment of collagen fibers relative to the abutment surface, improving connective tissue sealing around the zirconia abutment. Our results indicated that SFMG on zirconia can enhance HGF proliferation, migration and collagen synthesis by regulating glycolysis though PI3K-AKT-mTor pathway, thereby improving connective tissue sealing.

Optical properties of monolithic zirconia fabricated with nanoparticle jetting

STATEMENT OF PROBLEM

Excellent optical properties are essential for esthetic dental materials. However, the translucency and color masking ability of zirconia fabricated with nanoparticle jetting (NPJ), a type of printed zirconia, are unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the translucency and color masking ability of zirconia fabricated using NPJ.

MATERIAL AND METHODS

A total of 90 specimens with thicknesses of 1.5, 1.0, and 0.5 mm were fabricated using high translucent milled zirconia (HT), low translucent milled zirconia (LT), and NPJ. CIELab values (L*, a*, and b*) of the specimens over 7 backgrounds, black, white, VitaB1, VitaA2, VitaA4, gold alloy (Au), and titanium (Ti), were obtained using a spectral radiometer. The relative translucency parameter (RTP) and color difference (∆E) of specimens over VitaB1, VitaA4, Au, and Ti were determined using VitaA2 as the control with the CIEDE2000 color difference equation. The normality of the data distribution was determined using the Shapiro-Wilk test. Differences among groups were analyzed using 2-way analysis of variance and the Student-Newman-Keuls (SNK) post hoc test (α=.05). The ∆E of specimens was analyzed according to perceptibility (∆E=0.8) and acceptability (∆E=1.8) thresholds using the 1 sample t test. The correlation between RTP and ∆E and RTP/∆E and thickness was examined using the Pearson correlation analysis.

RESULTS

Statistically significant differences were observed in translucency and color masking ability among HT, LT, and NPJ (P<.05). The RTP value was the lowest for zirconia fabricated with NPJ (P<.001) and highest for HT (P<.001). Monolithic zirconia fabricated with NPJ had lower ∆E values than those of HT and LT for the same thickness and background (P<.05). A positive correlation was found in RTP and ∆E (P<.001). A negative correlation was observed in RTP and thickness (P<.001) and ∆E and thickness across a constant background (P<.001).

CONCLUSIONS

Zirconia fabricated with NPJ was less translucent and had a greater color masking ability for discolored backgrounds than HT and LT.

Effects and underlying mechanism of micro-nano-structured zirconia surfaces on biological behaviors of human gingival fibroblasts under inflammatory conditions

Zirconia is one of the most commonly used materials for abutments of dental implants, especially in the anterior region. Soft tissue integration to the zirconia abutment surface remains a challenge. Peri-implant soft tissue integration serves as a physiological barrier, attenuating pathogen penetration and preventing peri‑implant disease. The surface microstructure of zirconia has significant effects on the biological behaviors of human gingival fibroblasts (HGFs), but the effects under inflammatory conditions are still unclear. In this study, we established two micro-nano structures on zirconia surfaces using a femtosecond laser, including microgrooves with widths of 30 µm (G3) and 60 µm (G6) and depths of 5 µm, and nanoparticles inside the microgrooves. Polished surfaces were used as controls. HGFs were seeded onto the three groups of zirconia specimens and stimulated with lipopolysaccharide. The HGFs on micro-nano-structured zirconia surfaces exhibited lower inflammatory responses and higher cell adhesion, proliferation, and migration under inflammatory conditions compared with the polished surfaces. Additionally, the G3 group exhibited lower inflammatory responses and higher cell adhesion and migration than the G6 group. The micro-nano-structured zirconia surface exhibited decreased neutrophil infiltration and increased M2-type macrophage polarization in vivo. To explore the molecular mechanism, RNA sequencing and gene silencing were utilized, which revealed two critical target genes regulated by the G3 group. Overall, we proposed an innovative micro-nano-structured zirconia surface that reduced the in vitro and in vivo inflammatory responses and promoted HGF adhesion, migration, and proliferation under inflammatory conditions, in which TRAFD1 and NLRC5 were the underlying key genes. STATEMENT OF SIGNIFICANCE: Zirconia is one of the most commonly used materials for abutments, especially in the anterior region. The surface microstructure of zirconia has significant effects on the biological behaviors of human gingival fibroblasts (HGFs), but few studies have investigated these effects under inflammatory conditions, and the mechanism remains unclear. In this study, we developed an innovative micro-nano-structured zirconia surface using a femtosecond laser, which reduces the in vitro and in vivo pro-inflammatory responses and promotes HGFs adhesion, migration, and proliferation under inflammatory conditions compared with the polished zirconia surface. The potential underlying mechanism was also investigated. This work has provided some theoretical basis for the micro-nano-structured zirconia surface in potentially reducing the inflammation and enhancing peri‑implant soft-tissue integration under inflammatory conditions.

Synthesis of biocompatible Ti-6Al-4V composite reinforced with ZrO2 and bioceramic produced by powder metallurgy: Morphological, structural, and biocompatibility analysis

In this experimental study, the initial phase involved preparing composite structures with various mix ratios using the Ti-6Al-4V alloy, widely used in clinical applications, in conjunction with ZrO2 and hydroxyapatite (HA) synthesized via the precipitation method, employing powder metallurgy techniques. Subsequently, the microstructures of the resultant hybrid composite materials were imaged, and x-ray diffraction (XRD) phase analyses were conducted. In the final phase of the experimental work, tests were performed to determine the biocompatibility properties of the hybrid composites. For this purpose, cytotoxicity and genotoxicity assays were carried out. The tests and examinations revealed that structures compatible both morphologically and elementally were obtained with no phase transformations that could disrupt the structure. The incorporation of ZrO2 into the Ti-6Al-4V alloy was observed to enhance cell viability values. The value of 98.25 ± 0.42 obtained by adding 20% ZrO2 gave the highest cell viability result. The addition of HA into the hybrid structures further increased the cell viability values by approximately 10%. All viability values for both HA-added and HA-free groups were obtained above the 70% viability level defined in the standard. According to the genotoxicity test results, the highest cytokinesis-block proliferation index values were obtained as 1.666 and 0.620 in structures containing 20% ZrO2 and 10% ZrO2 + 10% HA, respectively. Remarkably, all fabricated composite and hybrid composite materials surpassed established biocompatibility standards and exhibited nontoxic and nongenotoxic properties. This comprehensive study contributes vital insights for future biomechanical and other in vitro and in vivo experiments, as it meticulously addresses fundamental characterization parameters crucial for medical device development. RESEARCH HIGHLIGHTS: Support of optimum doping rates ions on hybrid composites and concentrations. Development of uniform surface appearance and distributions/orientations of microcrystals on ceramic compounds Improvement of cell viability and desired increase in biocompatibility with the doping of HA.

SURVIVAL RATE OF IMPLANT-SUPPORTED, SINGLE-TOOTH RESTORATIONS BASED ON ZIRCONIA OR METAL ABUTMENT IN PATIENTS WITH TOOTH AGENESIS: A 5-YEARS PROSPECTIVE CLINICAL STUDY

OBJECTIVES

The primary aim was to investigate survival rate of zirconia versus metal abutments, and the secondary aim was clinical outcomes of all-ceramic versus metal-ceramic crowns on single-tooth implants.

METHODS

Patients with tooth-agenesis participated to previously published prospective clinical study with 3-year follow-up were recalled after 5 years. Biological variables included survival and success rate of implants, marginal bone level, modified Plaque and Sulcus Bleeding Index and biological complications. Technical variables included restoration survival rate, marginal adaptation and technical complications. The aesthetic outcome of crowns and peri-implant mucosa in addition to patient-reported outcome were recorded. Descriptive analysis, linear mixed model for quantitative data, or generalized linear mixed model for ordinal categorical data were applied; significance was set to 0.05.

RESULTS

Fifty-three patients (mean age: 32.4 years), with 89 implants participated to the 5-years examination. The implants supported 50 zirconia abutments with 50 all-ceramic (AC) crown and 39 metal abutments with 29 metal-ceramic (MC) and 10 AC crowns. The Implant and restoration survival rate was 100% and 96%, respectively. No clinically relevant biological difference between implants supporting metal or zirconia abutments was registered. The technical complications were veneering fracture of AC-crowns (n = 3), crown loosening of MC-crowns (n = 4) and one abutment screw loosening (MC-crown on metal abutment). MC-crowns had significantly better marginal adaptation than AC-crowns (p = .01). AC-crowns had significantly better color and morphology than MC-crowns (p = .01).

CONCLUSIONS

Zirconia-based single-tooth restorations are reliable alternative materials to metal-based restorations with favorable biological and aesthetic outcome, and few technical complications.

Zirconia Dental Implants Surface Electric Stimulation Impact on Staphylococcus aureus

Tooth loss during the lifetime of an individual is common. A strategy to treat partial or complete edentulous patients is the placement of dental implants. However, dental implants are subject to bacterial colonization and biofilm formation, which cause an infection named peri-implantitis. The existing long-term treatments for peri-implantitis are generally inefficient. Thus, an electrical circuit was produced with zirconia (Zr) samples using a hot-pressing technique to impregnate silver (Ag) through channels and holes to create a path by LASER texturing. The obtained specimens were characterized according to vitro cytotoxicity, to ensure ZrAg non-toxicity. Furthermore, samples were inoculated with Staphylococcus aureus using 6.5 mA of alternating current (AC). The current was delivered using a potentiostat and the influence on the bacterial concentration was assessed. Using AC, the specimens displayed no bacterial adhesion (Log 7 reduction). The in vitro results presented in this study suggest that this kind of treatment can be an alternative and promising strategy to treat and overcome bacterial adhesion around dental implants that can evolve to biofilm.

Cross-sectional analysis comparing prefabricated titanium to individualized hybrid zirconia abutments for cemented zirconia based fixed dental prostheses: a critical concept assessment

PURPOSE

Despite the differences in material properties and shapes among the different types of prefabricated titanium (pTiA) and individualized hybrid zirconia abutments (ihZiA), the biological and clinical relevance of materials and construction features remains vague. Yet, individualized ihZiA are increasingly implemented into daily routine aiming to satisfy rising expectations. The objective was to compare these two types of abutments in fixed dental prostheses (FDP).

METHODS

This cross-sectional study examined 462 implants in 102 patients comparing pTiA (52 patients) to ihZiA (50 patients) for FDP. These different treatment regimens were evaluated in terms of peri-implant health, radiographic bone loss, and oral-health related quality of life (OH-QoL) with special consideration of abutment type and superstructure design.

RESULTS

ihZiA showed significantly different design features than prefabricated pTiA, but the annual bone loss in both groups did not. Visible titanium in the esthetic zone negatively impacted OHIP 14 scores. The combination of an emergence angle (EA) of < 30° and a concave emergence profile (EP) as well as gingiva thickness (p = 0.002) at the time of the prosthetic restoration significantly improved the annual peri-implant bone loss, independently of the abutment type.

CONCLUSION

ihZiA showed comparable results to pTiA. To optimize the long-term outcome, not just material alone but generating adequate soft tissue thickness, minimizing the EA, and applying a concave EP seem to be the most relevant factors. To improve OH-QoL, particular attention must be paid to the esthetic zone.

Radiopacity Enhancements in Polymeric Implant Biomaterials: A Comprehensive Literature Review

Polymers as biomaterials possess favorable properties, which include corrosion resistance, light weight, biocompatibility, ease of processing, low cost, and an ability to be easily tailored to meet specific applications. However, their inherent low X-ray attenuation, resulting from the low atomic numbers of their constituent elements, i.e., hydrogen (1), carbon (6), nitrogen (7), and oxygen (8), makes them difficult to visualize radiographically. Imparting radiopacity to radiolucent polymeric implants is necessary to enable noninvasive evaluation of implantable medical devices using conventional imaging methods. Numerous studies have undertaken this by blending various polymers with contrast agents consisting of heavy elements. The selection of an appropriate contrast agent is important, primarily to ensure that it does not cause detrimental effects to the relevant mechanical and physical properties of the polymer depending upon the intended application. Furthermore, its biocompatibility with adjacent tissues and its excretion from the body require thorough evaluation. We aimed to summarize the current knowledge on contrast agents incorporated into synthetic polymers in the context of implantable medical devices. While a single review was found that discussed radiopacity in polymeric biomaterials, the publication is outdated and does not address contemporary polymers employed in implant applications. Our review provides an up-to-date overview of contrast agents incorporated into synthetic medical polymers, encompassing both temporary and permanent implants. We expect that our results will significantly inform and guide the strategic selection of contrast agents, considering the specific requirements of implantable polymeric medical devices.

Femtosecond Laser Irradiation to Zirconia Prior to Calcium Phosphate Coating Enhances Osteointegration of Zirconia in Rabbits

Calcium phosphate (CaP) coating of zirconia and zirconia-based implants is challenging, due to their chemical instability and susceptibility to thermal and mechanical impacts. A 3 mol% yttrium-stabilized tetragonal zirconia polycrystal was subjected to femtosecond laser (FsL) irradiation to form micro- and submicron surface architectures, prior to CaP coating using pulsed laser deposition (PLD) and low-temperature solution processing. Untreated zirconia, CaP-coated zirconia, and FsL-irradiated and CaP-coated zirconia were implanted in proximal tibial metaphyses of male Japanese white rabbits for four weeks. Radiographical analysis, push-out test, alizarin red staining, and histomorphometric analysis demonstrated a much improved bone-bonding ability of FsL-irradiated and CaP-coated zirconia over CaP-coated zirconia without FsL irradiation and untreated zirconia. The failure strength of the FsL-irradiated and CaP-coated zirconia in the push-out test was 6.2-13.1-times higher than that of the CaP-coated zirconia without FsL irradiation and untreated zirconia. Moreover, the adhesion strength between the bone and FsL-irradiated and CaP-coated zirconia was as high as that inducing host bone fracture in the push-out tests. The increased bone-bonding ability was attributed to the micro-/submicron surface architectures that enhanced osteoblastic differentiation and mechanical interlocking, leading to improved osteointegration. FsL irradiation followed by CaP coating could be useful for improving the osteointegration of cement-less zirconia-based joints and zirconia dental implants.

The possibility of clinical bonding between metal/ceramic brackets to zirconia: in vitro study

Objective: The present study aimed to assess the bond strength and durability of six bonding agents concerning their application to metal or ceramic brackets and zirconia. Materials and Methods: Six resin cement bonding agents (XT, XTS, RSBU, RGBU, SBPM, and GMP) were chosen for this investigation. Specimens were either stored in distilled water at 37°C for 24 h or subjected to 5,000 thermocycles before conducting a Shear Bond Strength (SBS) test. Statistical analysis of the SBS data was performed using three-way ANOVA and Games-Howell tests (α = 0.05). The Adhesive Remnant Index was examined, and the debonding surface details on brackets and zirconia were observed. Results: For metal brackets, all groups demonstrated clinically acceptable bond strength, irrespective of storage conditions, except for the XT group. Regarding ceramic brackets, all groups displayed acceptable bond strength after 24 h of water storage. However, following thermocycling, a significant decrease in SBS was noted across all groups (p < 0.05), with SBPM exhibiting a higher bond strength. Three-way ANOVA analysis indicated that SBS values were notably influenced by each factor, and an interaction among the three independent variables was observed (p = 0.000). Conclusion: The reliable bond strength between ceramic brackets and zirconia was significantly lower after thermocycling compared to that of metal brackets and zirconia. SBPM exhibited consistent and robust bond strength between ceramic/metal brackets and zirconia across various storage conditions. Furthermore, the HEMA-free adhesive demonstrated a potentially more consistent bonding performance compared to the HEMA-containing adhesive employed in this study.

Evaluation of In Vivo Biocompatibility in Preclinical Studies of a Finger Implant Medical Device Correlated with Mechanical Properties and Microstructure

The aim of the experiment was to evaluate the biocompatibility of four 3D-printed biomaterials planned for use in the surgical treatment of finger amputees: Ti-6Al-4 V (Ti64), ZrO2-Al2O3 ceramic material (ATZ20), and osteoconductive (anodized Ti64) and antibacterial (Hydroxyapatite, HAp) coatings that adhere well to materials dedicated to finger bone implants. The work concerns the correlation of mechanical, microstructural, and biological properties of dedicated materials. Biological tests consisted of determining the overall cytotoxicity of the organism on the basis of in vivo tests carried out in accordance with the ISO 10993-6 and ISO 10993-11 standards. Clinical observations followed by diagnostic examinations, histopathological evaluation, and biochemical characterization showed no significant differences between control and tested groups of animals. The wound healed without complication, and no pathological effects were found. The wear test showed the fragility of the hydroxyapatite thin layer and the mechanical stability of the zirconia-based ceramic substrate. Electron microscopy observations revealed the layered structure of tested substrates and coatings.

Implant-supported single all-ceramic crowns made from prefabricated (stock) or individualized CAD/CAM zirconia abutments: A 5 year randomized clinical trial

AIM

The aim of this randomized, prospective, and clinical multicenter study was to compare the overall clinical performance of two restorative options over a 5-year period: individualized CAD/CAM abutments veneered with a hand-layered ceramic, and prefabricated zirconium dioxide abutments veneered with press ceramic and inserted into a single edentulous gap in the anterior maxilla.

MATERIALS AND METHODS

Forty subjects were recruited from two universities: 20 from the University of XX and 20 from the University of XY. Each subject received an implant to restore a single edentulous gap in the maxillary anterior region (14-24 FDI). 20 patients were randomized into each Group. Group A received a one-piece single crown produced from a prefabricated zirconia abutment with pressed ceramic and Group B received an individualized CAD/CAM zirconia abutment with a hand-layered technique. After 5 years, the aesthetic and radiographic parameters were assessed.

RESULTS

Group A had four dropouts and one failure, resulting in a 95% survival rate and 95% success rate. Group B had two dropouts and two failures which resulted in a 90% survival rate and 90% success rate. No crestal bone level changes were observed, with a mean DIB of 0.06 mm in Group A and 0.09 mm in Group B. No statistically significant differences were present at baseline, 6 months, 1 year, 3 years, or 5 years for DIB values between time points and groups. Pink aesthetic score/white aesthetic score, Peri-Implant and Crown Index, and Implant Crown Aesthetic Index values were stable over time at all five points for both groups.

CONCLUSION

Both implant-supported restorative options represent a valuable treatment option for the restoration of implant crowns in the anterior maxilla.

CLINICAL SIGNIFICANCE

In general, the use of ceramic abutments in the anterior zone represents a valuable treatment procedure with both standardized and CAD/CAM individualized abutments and following the recommendations from the respective manufacturer(s).

Toward Elimination of Electrochemical Corrosion in Dental Implants: A Zirconia-Titanium Composite Prototype

Background Titanium dental implants (e.g., Nobel Biocare, Switzerland) are routinely used as support for dental restoration. Titanium has been the material of choice due to its corrosion resistance and ability to integrate with bone. Nevertheless, corrosion and titanium dissolution do occur. Compared to control, peri-implantitis tissue biopsies have been shown to contain high concentrations of dissolved titanium as well as metal particles. Dissolved titanium species have been found to be associated with the structure/diversity of the subgingival plaque microbiome and the extent of global methylation. Of note, peri-implantitis and peri-implant mucositis are common biological complications of implant therapy. Microorganisms and local inflammation together with a gradient of oxygen have been proven to form an electrochemical fuel cell, which generates the current that flows through the body of the titanium implant. Effectively, the fuel cell reduces oxygen and oxidizes titanium that turns into a soluble form. We are proposing a new zirconia-titanium composite implant design whereby the electrical current is disrupted while other properties are still conducive to osseointegration. Methodology Biocompatible zirconia bolts were treated with hydrofluoric acid (HF) and coated with titanium in a vacuum evaporator. The coating was masked with nail polish, and unmasked areas were etched with HF followed by mask removal with a solvent. Microbial challenges were conducted with a volunteer's plaque. Regular implant (control) and the prototype were inserted into simulated peri-implant environments implemented as a fiberglass sleeve immersed into a growth medium. After a five-day growth, samples were taken and HNO3 digested. Dissolved titanium was evaluated by inductively coupled plasma mass spectrometry. Results Proof-of-concept implant prototypes were successfully created. Vacuum deposition results in reproducible stable titanium coating. The thickness of the titanium coating was estimated using atomic force microscopy. A microbial challenge revealed that compared to the commercial titanium implant, the new implant prototype showed decreased amounts of corrosion-leached titanium. Conclusions We demonstrate a path forward toward a new design of a dental implant, whereby corrosion-induced electrical currents are interrupted resulting in a decreased amount of dissolved titanium.

Biological effects of gamma-ray sterilization on 3 mol% yttria-stabilized tetragonal zirconia polycrystal: An in vitro study

STATEMENT OF PROBLEM

Selecting the sterilization method is important because sterilization can alter the surface chemistry of implant materials, including zirconia, and influence their cellular biocompatibility. Studies on the biological effects of sterilization on implant materials are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the biocompatibility of gamma-ray irradiated 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) compared with unirradiated titanium, 3Y-TZP, and pure gold.

MATERIAL AND METHODS

Disk-shaped specimens each of commercially pure grade 4 titanium, 3Y-TZP, gamma-rayed 3Y-TZP, and pure gold were prepared and evaluated for osteogenic potential by using a clonal murine cell line of immature osteoblasts derived from mice (MC3T3-E1 cells). The surface topography (n=3), chemical analysis of the disks (n=3), and cell morphology cultured on these surfaces were examined using scanning electron microscopy, confocal laser scanning microscopy, and energy dispersive spectroscopy. Cellular biocompatibility was analyzed for 1 and 3 days after seeding. Cell adhesion and spreading were evaluated using confocal laser scanning microscopy (n=3). Cell proliferation was evaluated using methyl thiazolyl tetrazolium assay (n=3). Kruskal-Wallis and Bonferroni corrections were used to evaluate the statistical significance of the intergroup differences (α=.05).

RESULTS

Gamma-ray sterilization of 3Y-TZP showed significantly higher surface roughness compared with titanium and gold (P<.002). On day 1, the proliferation and adhesion of MC3T3-E1 cells cultured on gamma-rayed 3Y-TZP were significantly higher than those cultured on gold (P<.05); however, cell spreading was significantly lower than that of titanium on days 1 and 3 (P<.05). On day 3, cell proliferation of gamma-rayed 3Y-TZP was significantly lower than that of unirradiated 3Y-TZP (P<.05). Cell adhesion of gamma-rayed 3Y-TZP was slightly lower than that of zirconia and titanium but without significant difference (P>.05).

CONCLUSIONS

Gamma-rayed zirconia exhibited increased surface roughness compared with titanium and significantly decreased bioactivity compared with titanium and zirconia. The use of gamma-ray sterilization on zirconia is not promising regarding biocompatibility, and the effect of this sterilization method on implant materials warrants further investigation.

Incorporating zinc ion into titanium surface promotes osteogenesis and osteointegration in implantation early phase

The objective of this study is to further investigate the feasibility of Zinc-Titanium implant as a potential implantable material in oral application in aspects of osteoblast biocompatibility, osteogenesis and osseointegration ability. First, we used plasma immersion ion implantation and deposition (PIIID) technology to introduce Zinc ion into pure Titanium surface, then we used X-ray photoelectron spectroscopy to analyze the chemical composition of modified surface layer; next, we used in vitro studies including immunological fluorescence assay and western blotting to determine responses between MG-63 osteoblast-like cell and implant. In vivo studies adopted pig model to check the feasibility of Zn-Ti implant. Results showed that in vitro and in vivo were consistent, showing that Zn ion was successfully introduced into Ti surface by PIIID technique. The chemical and physical change on modified plant resulted in the more active expressions of mRNA and protein of Type I collagen in MG-63 cells compared with non-treated implant, and the better integration ability of bones with modified implant. We confirmed the Zn-Ti implant owns the ability in promoting osteogenesis and osteointegration in early phase of implantation and is a qualified candidate in dentistry. The overview of our study can be depicted as follows.

New biomaterials for modern dentistry

Whilst the appropriate assessment criteria for dental biomaterials is debated, there has been an increasing interest in the use of dental biomaterials for oral rehabilitation. Consequently, a variety of new biomaterials have been introduced in dentistry. To address this issue, BMC Oral Health has launched a Collection on "New biomaterials for modern dentistry".

Overview of strategies to improve the antibacterial property of dental implants

The increasing number of peri-implant diseases and the unsatisfactory results of conventional treatment are causing great concern to patients and medical staff. The effective removal of plaque which is one of the key causes of peri-implant disease from the surface of implants has become one of the main problems to be solved urgently in the field of peri-implant disease prevention and treatment. In recent years, with the advancement of materials science and pharmacology, a lot of research has been conducted to enhance the implant antimicrobial properties, including the addition of antimicrobial coatings on the implant surface, the adjustment of implant surface topography, and the development of new implant materials, and significant progress has been made in various aspects. Antimicrobial materials have shown promising applications in the prevention of peri-implant diseases, but meanwhile, there are some shortcomings, which leads to the lack of clinical widespread use of antimicrobial materials. This paper summarizes the research on antimicrobial materials applied to implants in recent years and presents an outlook on the future development.

The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

Digital replication and transfer of interim to definitive complete arch implant-supported fixed prostheses by using a laboratory scanner

The present technique describes an effective digital approach for the replication and transfer of occlusion, maxillomandibular relationship, and esthetic parameters from interim to definitive complete arch implant-supported fixed prostheses by laboratory scanning with transfer plates. Monolithic zirconia complete arch implant prostheses have been fabricated with satisfactory functional and esthetic outcomes.

Comparison between bone-implant interfaces of microtopographically modified zirconia and titanium implants

The aim of this study was to investigate the surface characteristics and evaluate the bone-implant interfaces of injection molded zirconia implants with or without surface treatment and compare them with those of conventional titanium implants. Four different zirconia and titanium implant groups (n = 14 for each group) were prepared: injection-molded zirconia implants without surface treatment (IM ZrO₂); injection-molded zirconia implants with surface treatment via sandblasting (IM ZrO₂-S); turned titanium implants (Ti-turned); and titanium implants with surface treatments via sandblasting with large-grit particles and acid-etching (Ti-SLA). Scanning electron microscopy, confocal laser scanning microscopy, and energy dispersive spectroscopy were used to assess the surface characteristics of the implant specimens. Eight rabbits were used, and four implants from each group were placed into the tibiae of each rabbit. Bone-to-implant contact (BIC) and bone area (BA) were measured to evaluate the bone response after 10-day and 28-day healing periods. One-way analysis of variance with Tukey's pairwise comparison was used to find any significant differences. The significance level was set at α = 0.05. Surface physical analysis showed that Ti-SLA had the highest surface roughness, followed by IM ZrO₂-S, IM ZrO₂, and Ti-turned. There were no statistically significant differences (p > 0.05) in BIC and BA among the different groups according to the histomorphometric analysis. This study suggests that injection-molded zirconia implants are reliable and predictable alternatives to titanium implants for future clinical applications.

Differences in Titanium, Titanium-Zirconium, Zirconia Implants Treatment Outcomes: a Systematic Literature Review and Meta-Analysis

Objectives

The objective of this systematic review is to test the hypothesis that treatment with titanium, titanium-zirconium and zirconia dental implants has different clinical outcomes in survival rate, marginal bone loss, bleeding on probing, plaque control record, and probing depth.

Material and Methods

A systematic electronic search through the PubMed (MEDLINE) and Cochrane Library databases was performed to identify studies published between January 1, 2013 and January 1, 2023 containing a minimum of 10 patients per study comparing titanium (Ti), titanium-zirconium (Ti-Zr), and zirconia (Zr) dental implants. Ti, Ti-Zr, and Zr dental implant clinical outcomes were determined by evaluating survival rate, marginal bone level, bleeding on probing, probing depth, plaque control record. Quality and risk-of-bias assessment were evaluated by Cochrane risk of bias tool.

Results

A total of 1361 articles were screened, with 10 meeting the inclusion criteria and being utilized for this systematic review and meta-analysis. A total of 301 patients with 637 implants (304 Ti, 134 Ti-Zr, and 199 Zr) were evaluated, showing a survival rate of 97.7% for Ti, 98.6% for Ti-Zr, and 93.8% for Zr implants respectively. In a meta-analysis, no difference in marginal bone level was found between Ti, Ti-Zr, and Zr implants (P = 0.84).

Conclusions

Dental implant survival rate was lower in zirconia group. Assessment of marginal bone loss and bleeding on probing showed better results with titanium-zirconium dental implants. Plaque control result was similar in all groups. Due to limited sample size assessed it was not possible to obtain conclusion on probing depth parameter.

Dental Materials Applied to 3D and 4D Printing Technologies: A Review

As computer-aided design and computer-aided manufacturing (CAD/CAM) technologies have matured, three-dimensional (3D) printing materials suitable for dentistry have attracted considerable research interest, owing to their high efficiency and low cost for clinical treatment. Three-dimensional printing technology, also known as additive manufacturing, has developed rapidly over the last forty years, with gradual application in various fields from industry to dental sciences. Four-dimensional (4D) printing, defined as the fabrication of complex spontaneous structures that change over time in response to external stimuli in expected ways, includes the increasingly popular bioprinting. Existing 3D printing materials have varied characteristics and scopes of application; therefore, categorization is required. This review aims to classify, summarize, and discuss dental materials for 3D printing and 4D printing from a clinical perspective. Based on these, this review describes four major materials, i.e., polymers, metals, ceramics, and biomaterials. The manufacturing process of 3D printing and 4D printing materials, their characteristics, applicable printing technologies, and clinical application scope are described in detail. Furthermore, the development of composite materials for 3D printing is the main focus of future research, as combining multiple materials can improve the materials' properties. Updates in material sciences play important roles in dentistry; hence, the emergence of newer materials are expected to promote further innovations in dentistry.

Advances of plant and biomass extracted zirconium nanoparticles in dental implant application

Nanoparticles are minimal materials with unique physicochemical features that set them apart from bulk materials of the same composition. These properties make nanoparticles highly desirable for use in commercial and medical research. The primary intention for the development of nanotechnology is to achieve overarching social objectives like bettering our understanding of nature, boosting productivity, improving healthcare, and extending the bounds of sustainable development and human potential. Keeping this as a motivation, Zirconia nanoparticles are becoming the preferred nanostructure for modern biomedical applications. This nanotechnology is exceptionally versatile and has several potential uses in dental research. This review paper concentrated on the various benefits of zirconium nanoparticles in dentistry and how they provide superior strength and flexibility compared to their counterparts. Moreover, the popularity of zirconium nanoparticles is also growing as it has strong biocompatibility potency. Zirconium nanoparticles can be used to develop or address the major difficulty in dentistry. Therefore, this review paper aims to provide a summary of the fundamental research and applications of zirconium nanoparticles in dental implants.

Functionalization of zirconia ceramic with fibronectin proteins enhanced bioactivity and osteogenic response of osteoblast-like cells

Introduction: To overcome the genuine bioinert properties of zirconia ceramic, functionalization of the surface with the bioactive protein fibronectin was conducted. Methods: Glow discharge plasma (GDP)-Argon was first used to clean the zirconia surface. Then allylamine was treated at three different powers of 50 W, 75 W, and 85 W and immersed into 2 different fibronectin concentrations (5 µg/ml and 10 µg/ml). Results and Discussion: After surface treatment, irregularly folded protein-like substances were attached on the fibronectin coated disks, and a granular pattern was observed for allylamine grafted samples. Infrared spectroscopy detected C-O, N-O, N-H, C-H, and O-H functional groups for fibronectin treated samples. Surface roughness rose and hydrophilicity improved after the surface modification, with MTT assay showing the highest level of cell viability for the A50F10 group. Cell differentiation markers also showed that fibronectin grafted disks with A50F10 and A85F10 were the most active, which in turn encouraged late-stage mineralization activity on 21d. Up-regulation of osteogenic related mRNA expression from 1d to 10d can be observed in RT-qPCR data for ALP, OC, DLX5, SP7, OPG and RANK biomarkers. These physical and biological properties clearly indicate that an allylamine and fibronectin composite grafted surface significantly stimulated the bioactivity of osteoblast-like cells, and can be utilized for future dental implant applications.

Response of Human Gingival Fibroblasts and Porphyromonas gingivalis to UVC-Activated Titanium Surfaces

Ultraviolet (UV) photofunctionalization has been demonstrated to synergistically improve the osteoblast response and reduce biofilm formation on titanium (Ti) surfaces. However, it remains obscure how photofunctionalization affects soft tissue integration and microbial adhesion on the transmucosal part of a dental implant. This study aimed to investigate the effect of UVC (100–280 nm) pretreatment on the response of human gingival fibroblasts (HGFs) and Porphyromonas gingivalis (P. g.) to Ti-based implant surfaces. The smooth and anodized nano-engineered Ti-based surfaces were triggered by UVC irradiation, respectively. The results showed that both smooth and nano-surfaces acquired super hydrophilicity without structural alteration after UVC photofunctionalization. UVC-activated smooth surfaces enhanced the adhesion and proliferation of HGFs compared to the untreated smooth ones. Regarding the anodized nano-engineered surfaces, UVC pretreatment weakened the fibroblast attachment but had no adverse effects on proliferation and the related gene expression. Additionally, both Ti-based surfaces could effectively inhibit P. g. adhesion after UVC irradiation. Therefore, the UVC photofunctionalization could be more potentially favorable to synergistically improve the fibroblast response and inhibit P. g. adhesion on the smooth Ti-based surfaces.

Bioengineering Applied to Oral Implantology, a New Protocol: “Digital Guided Surgery”

Rehabilitative dentistry has made enormous progress in recent years, not only due to the advent of new implant-prosthetic methods, but also thanks to new information technologies that support the doctor. This study aims to present a new implant protocol that involves the application of bioengineering methods. With the application of the finite element analysis, it is possible to evaluate the distribution of the forces of a fixture and possible implant rehabilitation on each patient, even before performing the surgery. This protocol provides for the combination of radiographic images and three-dimensional files to obtain predictable results on possible rehabilitation, guiding its planning in the best possible way. Surely, the evolution of machines and computers will enable the surgeon to carry out and maintain these protocols in a chair-side manner, and to carry out safe and predictable rehabilitations.

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

Background/purpose

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.

Materials and methods

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).

Results

Under a 20-min deposition time at 40 W and 150 mTorr, the thin films had a maximum graft density of 2.1 mg/cm². MG-63 cells (human osteosarcoma cells) were employed to evaluate cell compatibility. Chitosan and chitosan/poly-γ-glutamic acid promoted the compatibility of MG-63 cells (a human osteosarcoma cell line) with zirconia ceramics, whereas gelatin reduced this compatibility.

Conclusion

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.

Numerical Analysis of Zirconium and Titanium Implants under the Effect of Critical Masticatory Load

Dental implants have become an alternative to replace the teeth of people suffering from edentulous and meet the physiological and morphological characteristics (recovering 95% of the chewing function). The evolution and innovation of biomaterials for dental implants have had a trajectory that dates back to prehistory, where dental pieces were replaced by ivory or seashells, to the present day, where they are replaced by metallic materials such as titanium or ceramics such as zirconium or fiberglass. The numerical evaluation focuses on comparing the stress distribution and general displacement between different dental implants and a healthy tooth when applying a force of 850 N. For the analysis, a model of the anatomical structure was developed of a healthy tooth considering three essential parts of the tooth (enamel, dentin, and pulp). The tooth biomodel was established through computed tomography. Three dental implant models were considered by changing the geometry of the abutment. A structural simulation was carried out by applying the finite element method (FEM). In addition, the material considered for the analyses was zirconium oxide (ZrO2), which was compared against titanium alloy (Ti6Al4V). The analyses were considered with linear, isotropic, and homogeneous properties. The variables included in the biomodeling were the modulus of elasticity, Poisson's ratio, density, and elastic limit. The results obtained from the study indicated a significant difference in the biomechanical behavior of the von Mises forces and the displacement between the healthy tooth and the titanium and zirconium implant models. However, the difference between the titanium implant and the zirconium implant is minimal because one is more rigid, and the other is more tenacious.

Preparation and Characterization of a Polyetherketoneketone/Hydroxyapatite Hybrid for Dental Applications

Here, we developed a new synthetic method for the production of a new class of polymeric inorganic hybrid biomaterial that has potential for dental implant applications and, in general, other orthopedic applications owing to its excellent mechanical properties and biomechanical compatibility. The new hybrid biomaterial is a composite consisting of polyetherketoneketone (PEKK) and hydroxyapatite (HA). This hybrid material boasts several unique features, including its high HA loading (up to 50 wt%), which is close to that of natural human bone; the homogeneous HA distribution in the PEKK matrix without phase separation; and the fact that the addition of HA has no effect on the molecular weight of PEKK. Nanoindentation analysis was used to investigate the mechanical properties of the composite, and its nano/microstructure variations were investigated through a structural model developed here. Through nanoindentation technology, the newly developed PEKK/HA hybrid biomaterial has an indentation modulus of 12.1 ± 2.5 GPa and a hardness of 0.42 ± 0.09 GPa, which are comparable with those of human bone. Overall, the new PEKK/HA biomaterial exhibits excellent biomechanical compatibility and shows great promise for application to dental and orthopedic devices.

Antibacterial Ti-Cu implants: A critical review on mechanisms of action

Titanium (Ti) has been widely used for manufacturing of bone implants because of its mechanical properties, biological compatibility, and favorable corrosion resistance in biological environments. However, Ti implants are prone to infection (peri-implantitis) by bacteria which in extreme cases necessitate painful and costly revision surgeries. An emerging, viable solution for this problem is to use copper (Cu) as an antibacterial agent in the alloying system of Ti. The addition of copper provides excellent antibacterial activities, but the underpinning mechanisms are still obscure. This review sheds light on such mechanisms and reviews how incorporation of Cu can render Ti–Cu implants with antibacterial activity. The review first discusses the fundamentals of interactions between bacteria and implanted surfaces followed by an overview of the most common engineering strategies utilized to endow an implant with antibacterial activity. The underlying mechanisms for antibacterial activity of Ti–Cu implants are then discussed in detail. Special attention is paid to contact killing mechanisms because the misinterpretation of this mechanism is the root of discrepancies in the literature.

Finite Element Analysis of Zirconia Dental Implant

Titanium dental implants have had new competitors in recent years, such as fixtures made of zirconia, which promise better aesthetics. The purpose of this study is to evaluate their mechanical performance in silico (Finite Element Analysis). The investigation was performed on a single tooth Patent™ Dental Implant (Zircon Medical®, Altendorf, Switzerland) in two configurations: without offset (Test I) and with offset (Test II, 1.5 mm within the cortical bone). The Patent Implant system consists of two components: the implant with integrated abutment and the fibreglass post. The components of the dental implants were tested using a compression load of 400 N along the implant axis. The results showed that the chewing load generates stress distribution on the bone, therefore, the offset configuration should be avoided.

The effect of surface material, roughness and wettability on the adhesion and proliferation of Streptococcus gordonii, Fusobacterium nucleatum and Porphyromonas gingivalis

Background/purpose

Dental implants are inevitably exposed to bacteria in oral cavity. Understanding the colonization of bacteria on implant surface is necessary to prevent bacteria-related inflammation surrounding dental implants. The purpose of this study was to investigate the effect of surface properties on biofilm formation on the implant surface.

Materials and methods

One early colonizer, Streptococcus gordonii (S. gordonii), and two late colonizers, Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis), were grown on the titanium and zirconia surfaces with two types of surface roughness for 24 and 72 h. Each bacterial biofilm on specimens was quantified using crystal violet assay and observed by scanning electron microscopy.

Results

S. gordonii formed more biofilm on the titanium surface than zirconia at the same roughness and more biofilm on the rough surface than smooth one of the same materials at 24 and 72 h of incubation. F. nucleatum adhered on all the surfaces at 24 h and proliferated actively on the surfaces except smooth zirconia at 72 h. P. gingivalis proliferated vigorously on the surfaces at 72 h while it scarcely adhered at 24 h. There was no consistent correlation between contact angle and biofilm formation of the three bacteria.

Conclusion

The three bacteria proliferated most on the rough titanium surface and least on the smooth zirconia surface. In addition, the proliferation was affected by the bacterial species as well as the surface properties.

Cytokines Activate JAK-STAT Signaling Pathway in MG-63 Cells on Titanium and Zirconia

Although titanium has been traditionally used as the gold standard for dental implants, recent years have seen the widespread application of zirconia implants given their superiority with regards to reduced bacterial adhesion, inflammation and cellular-interaction in terms of bio-compatibility. The JAK-STAT signaling pathway plays an important role in bone remodeling and formation. The aim of the study was to investigate the activation of the JAK-STAT pathway through different cytokines in osteoblast-like cells (MG-63) on zirconia in comparison to titanium discs. IFN-γ induced the very strong activation of STAT1 protein, IFN-α activated both STAT1 and STAT3 molecules, IL-6 activated STAT3 and IL-4 induced the activation of STAT6 on both surfaces. The activation of STAT proteins was confirmed by western blot, immunofluorescence and flow cytometry using phospho-specific anti-STAT antibodies, which recognize only phosphorylated STAT proteins. The incubation of MG-63 cells with IFN-γ caused the upregulation of MHC class I and class II proteins when MG-63 cells were grown on zirconia and titanium discs. In sum, the present study shows that the JAK-STAT pathway is activated in MG-63 cells when they are incubated on titanium or zirconia surfaces.

Biocompatibility of titanium from the viewpoint of its surface

Among metals, Ti and majority of its alloys exhibit excellent biocompatibility or tissue compatibility. Although their high corrosion resistance is a factor in the biocompatibility of Ti and Ti alloys, it is clear that other factors exist. In this review, the corrosion resistance and passive film of Ti are compared to those of other metallic biomaterials, and their band gap energies, E_gs, are compared to discuss the role of E_g in the reactivity with living tissues. From the perspective of the material's surface, it is possible to explain the excellent biocompatibility of Ti by considering the following factors: Ti ions are immediately stabilized not to show toxicity if it is released to body fluids; good balance of positive and negative charges by the dissociation of surface hydroxyl groups on the passive film; low electrostatic force of the passive film inducing a natural adsorption of proteins maintaining their natural conformation; strong property as n-type semiconductor; lower band gap energy of the passive film on Ti generating optimal reactivity; and calcium phosphate formation is caused by this reactivity. The results suggest that due to the passive oxide film, the optimal balance between high corrosion resistance and appropriate reactivity of Ti is the predominate solution for the excellent biocompatibility of Ti.

Effect of Non-Thermal Plasma Treatment of Contaminated Zirconia Surface on Porphyromonas gingivalis Adhesion and Osteoblast Viability

Plasma treatment on a zirconia surface prevents bacterial contamination and maintains osteoblast activity. To assess the degree of adhesion of Porphyromonas gingivalis on a zirconia surface after non-thermal plasma (NTP) treatment, specimens were treated with plasma for 60, 300, and 600 s, after which P. gingivalis was inoculated onto the surface and incubated for 48 h. To assess osteoblast activity after NTP treatment, osteoblasts (MC3T3-E1) were dispensed onto the specimens contaminated with P. gingivalis immediately after NTP for 60 and 120 s, followed by incubation for 48, 72, and 96 h. P. gingivalis was cultured after 60 s of NTP treatment of zirconia. The NTP and control groups showed no significant difference (p = 0.91), but adhesion was significantly increased following NTP treatment for 300 s or longer (300, 600 s groups) (p < 0.05). After NTP treatment of P. gingivalis-contaminated zirconia, osteoblast activity significantly increased at 72 and 96 h (I60 and I120 s group) in the groups treated with plasma (p < 0.017). Application of NTP to dental zirconia implants for 60 s not only inhibits the proliferation of P. gingivalis, which causes peri-implantitis but also increases osseointegration on zirconia surfaces contaminated with P. gingivalis.

Influence of the Surface Chemical Composition Differences between Zirconia and Titanium with the Similar Surface Structure and Roughness on Bone Formation

The osseointegration of zirconia (ZrO2) implants is still controversial. In this study, we aimed to make clear the influence of surface chemical composition, Ti or ZrO2, to osseointegration. First, a roughened Ti surface was prepared with a combination of large-grit sandblasting and acid treatment. Then, we applied molecular precursor solution containing Zr complex onto roughened Ti surface and can deposit thin ZrO2 film onto roughened Ti surface. We can change surface chemical composition from Ti to ZrO2 without changing the surface structure and roughness of roughened Ti. The tetragonal Zr was uniformly present on the ZrO2-coated Ti surface, and the surface of the ZrO2-coated Ti showed a higher apparent zeta potential than Ti. Ti and ZrO2-coated Ti rectangular plate implant was placed into the femur bone defect. After 2 and 4 weeks of implantation, histomorphometric observation revealed that the bone-to-implant contact ratio and the bone mass values for ZrO2-coated Ti implants inserted into the femur bone defects of the rats at 2 weeks were significantly higher than those for Ti implants (p < 0.05). It revealed that ZrO2 with a similar surface structure and roughness as that of roughened Ti promoted osteogenesis equivalent to or better than that of Ti in the early bone formation stage.

Effect of the surface finish on the mechanical properties and cellular adhesion in (Ce,Y)-TZP/Al2O3 ceramic composites for denture implants

Ceramic composites based on (Ce, Y)-TZP/Al₂O₃ system have great potential for applications as dental implants due to their unusually great balance between good mechanical properties and resistance to hydrothermal degradation. Surface roughness plays an important role in controlling these properties, but few studies have investigated the relationship between cytocompatibility and surface roughness, at levels considered moderate and low, comparable to titanium implants. In this work, bending strength, hydrothermal degradation and biological evaluation of a ceramic composite based on (Ce,Y)-TZP/Al₂O₃ system were investigated as a function of surface roughness. Compacted samples were sintered at 1500 °C - 2h and then submitted to different surface treatments: Group 1 composed of samples with smooth surfaces, Group 2 and Group 3 composed of rough surfaces (grinded with 15 μm or 45 μm diamond sandpaper, respectively. Samples were characterized by X-ray diffraction, scanning electron microscopy, contact angle and optical profilometry and then subjected to hydrothermal degradation tests in autoclave (134 °C - 2 bar) using artificial saliva. The Piston-on-three-balls (P-3B) testing was used to determine flexural strength. To assess indirect cytotoxicity, samples were immersed in the culture medium for NIH-3T3 cells for 72 h. Furthermore, cell adhesion and proliferation were investigated using MG63 cells (human osteosarcoma) after 3, 7, 14, and 21 days of culture. Cytotoxicity, adhesion, and cell proliferation were examined by the Methyl Tetrazolium salt (MTS) and Alizarin Red, using a confocal laser microscope. The results indicated that the materials have high resistance to degradation. Furthermore, the (Ce,Y)-TZP/Al₂O₃ composites are not cytotoxic. The flexural strength of the composites was 913 ± 103 MPa in samples presenting original (smooth) surface, however, a reduction in the order of 17% was observed in samples containing rough surfaces. The rougher samples show the best cellular adhesion and proliferation, leading to the formation of a mineralized matrix after 21 days. These results clearly suggest that the new (Ce,Y)-TZP/Al₂O₃ brand is strong and highly biocompatible and warrants further study.

The Main Bacterial Communities Identified in the Sites Affected by Periimplantitis: A Systematic Review

(1) Background: Periimplantitis is an infectious condition that affects the periimplant tissue and is of bacterial etiology. However, to date, the exact bacterial flora involved in its occurrence is not known. The aim of this literature review was to summarize the articles published on this topic and to identify the main bacterial species isolated in periimplantitis. (2) Methods: The articles published in three databases were researched: Pubmed, Embase and Web of Science using Prisma guides and combinations of MeSH terms. We selected 25 items from the 980 found by applying the inclusion and exclusion criteria. (3) Results: We quantified the results of the 25 studies included in this review. In general, the most commonly identified bacterial species were Gram-negative anaerobic species, as Prevotella, Streptococcus, Fusobacterium and Treponema. (4) Conclusion: The most frequent bacteria in the periimplantitis sites identified in this review are Gram-negative anaerobic species, also involved in the pathogenesis of the periodontal disease.

Bone Tissue Engineering through 3D Bioprinting of Bioceramic Scaffolds: A Review and Update

Trauma and bone loss from infections, tumors, and congenital diseases make bone repair and regeneration the greatest challenges in orthopedic, craniofacial, and plastic surgeries. The shortage of donors, intrinsic limitations, and complications in transplantation have led to more focus and interest in regenerative medicine. Structures that closely mimic bone tissue can be produced by this unique technology. The steady development of three-dimensional (3D)-printed bone tissue engineering scaffold therapy has played an important role in achieving the desired goal. Bioceramic scaffolds are widely studied and appear to be the most promising solution. In addition, 3D printing technology can simulate mechanical and biological surface properties and print with high precision complex internal and external structures to match their functional properties. Inkjet, extrusion, and light-based 3D printing are among the rapidly advancing bone bioprinting technologies. Furthermore, stem cell therapy has recently shown an important role in this field, although large tissue defects are difficult to fill by injection alone. The combination of 3D-printed bone tissue engineering scaffolds with stem cells has shown very promising results. Therefore, biocompatible artificial tissue engineering with living cells is the key element required for clinical applications where there is a high demand for bone defect repair. Furthermore, the emergence of various advanced manufacturing technologies has made the form of biomaterials and their functions, composition, and structure more diversified, and manifold. The importance of this article lies in that it aims to briefly review the main principles and characteristics of the currently available methods in orthopedic bioprinting technology to prepare bioceramic scaffolds, and finally discuss the challenges and prospects for applications in this promising and vital field.

The enhancing effects of heparin on the biological activity of FGF-2 in heparin-FGF-2-calcium phosphate composite layers

Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the composite layers is important for its wider application in orthopedics and dentistry. This study incorporated low-molecular-weight heparin (LMWH) into the FGF-2-calcium phosphate composite layers and clarified the enhancing effects of LMWH on the biological activity of FGF-2 in the composite layers in vitro. LMWH-FGF-2-calcium phosphate composite layers were successfully formed on zirconia in supersaturated calcium phosphate solutions. The composite layers comprised continuous and macroscopically homogeneous layers and particles smaller than 500 nm in size composed of amorphous calcium phosphate. The amounts of Ca and P deposited on zirconia remained almost unchanged with the addition of LMWH under the presence of FGF-2 in the supersaturated calcium phosphate solution. The LMWH in the supersaturated calcium phosphate solution increased the stability of FGF-2 in the solution and the amount of FGF-2 in the composite layers. The LMWH in the composite layers increased the mitogenic and endothelial tube-forming activities of FGF-2, and FGF-2 activity of inducing osteogenic differentiation gene expression pattern in the composite layers. Our results indicate that the enhanced biological activity of FGF-2 in the LMWH-FGF-2-calcium phosphate composite layers is attributed to an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the supersaturated calcium phosphate solution and the composite layers. The LMWH-FGF-2-calcium phosphate composite layer is a promising coating for orthopedic and dental implants. STATEMENT OF SIGNIFICANCE: Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the layers is important for wider its application in orthopedics and dentistry. This study demonstrates the enhancing effects of low-molecular-weight heparin (LMWH) contained within LMWH-FGF-2-calcium phosphate composite layers on the biological activity of FGF-2 in vitro. Our results indicate that the enhanced biological activity of FGF-2 within the composite layers arises from an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the LMWH-FGF-2-calcium phosphate composite layers and supersaturated calcium phosphate solutions used for coating the composite layers.

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.

Topographical changes and bactericidal efficacy of antimicrobial photodynamic therapy on titanium implant surface

BACKGROUND

A lot of research has been done on various disinfection modalities used to achieve an aseptic implant surface. However, the bacterial efficacy and the topographical alterations resulting from the use of these techniques have never been compared.

OBJECTIVE

This study aimed to evaluate and compare the disinfection efficacy and surface changes on a bacteria contaminated titanium block following application of various disinfectants.

METHOD

Ultrasonically cleaned titanium blocks were contaminated with Porphyromonas gingivalis and Tannerella forsythia. The infected titanium implants were randomly divided into four experimental groups and decontaminated using antimicrobial photodynamic therapy (aPDT), laser therapy, chlorhexidine and hydrogen peroxide. Bacterial viability and surface changes following decontamination were analyzed.

RESULT

Bacterial viability decreased in all the groups with aPDT having the highest reduction. Surface roughness remained unchanged whereas the contact angle lessened in the aPDT group.

CONCLUSION

aPDT could possibly be a suitable alternative to other disinfection regimen to treat periimplantitis.

Effect of Porous Zirconia Coating on Human Gingival Fibroblasts and Its Mechanism

Gingival fibroblasts play an important role in the constitution of soft tissue attachment. This study aims to investigate whether porous zirconia coating has a positive effect on promoting human gingival fibroblast attachment. The porous zirconia coating was loaded on zirconia surface by the dip coating method, surface morphology and composition were confirmed by scanning electron microscope and energy dispersive spectrometer; Tested the tensile bond strength by universal testing machine; Tested the surface roughness by roughness analyzer; Human gingival fibroblast proliferation, integrin β1 and F-actin immunofluorescence staining explored the influence of porous zirconia on the adhesion and proliferation of human gingival fibroblast. Zirconia0.2 group showed spherical zirconia particles with diameters of 3-8 μm are distributed on the surface; The bonding strength of zirconia particle coating group reached 16.1±0.1 MPa, and the surface roughness was 0.715±0.091 μm; In comparison with control group (P < 0.01), the percentage of human gingival fibroblasts adhering to zirconia was markedly higher. In zirconia group, integrin-β1 and F-actin fluoresced more obvious than in control group. Porous zirconia coating can form a porous structure on the surface and the porous structure can promote the attachment and proliferation of human gingival fibroblast, it will be more beneficial for soft tissue early sealing.

Human Gingival Fibroblast and Osteoblast Behavior on Groove-Milled Zirconia Implant Surfaces

Two type of cells representing periodontal hard tissues (osteoblasts) and soft tissues (fibroblasts) were evaluated in response to microgroove-milled zirconia surfaces. A total of 90 zirconia discs were randomly assigned to four width-standardized milling microgroove-textured groups and a control group without grooves (UT). The sandblast and acid-etch protocol were applied to all samples. Both cell lines were cultured on zirconia discs from 1 day up to 14 days. Cell morphology and adhesion were evaluated after 1 day of culturing. Cell viability and proliferation of the cells were measured. Alkaline phosphatase activity, collagen I, osteopontin, interleukin 1β and interleukin 8 secretions were assessed at predefined times. The results obtained were presented in the form of bar graphs as means and standard deviations. Multi comparisons between groups were evaluated using two-away ANOVA or Mann−Whitney tests, and a p-value < 0.05 was established. Group comparisons with regard to cell viability, proliferation and secretion of collagen I, interleukin-1β and interleukin 8 revealed no statistically significant differences. The alkaline phosphatase activity and osteopontin secretion were significantly higher in the group with a large groove compared to the small one and the control group. Nevertheless, the viability of gingival and bone cells did not appear to be affected by the milled microgroove texture compared to the conventional sandblasted and acid-etched texture, but they seem to influence osteoblasts’ cellular differentiation.

[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.

Influence of different zirconia surface treatments on biofilm formation in vitro and in situ

OBJECTIVES

To determine if the surface treatment of zirconia affects biofilm formation in an in vitro three-species biofilm model and in situ.

MATERIAL AND METHODS

Zirconia surfaces considered for the transmucosal portion of a zirconia implant were compared with polished pure titanium grade 4 (Tp). Discs 13 mm in diameter of either polished (Zp), polished and heat-treated (Zpt), machined (Zm), machined and heat-treated (Zmt) and sandblasted, etched and heat-treated (Z14) zirconia were fabricated. Surface roughness and wettability of specimens was measured. Biofilm formation was evaluated by safranin staining and scanning electron microscopy (SEM) using a three-species model, and intraorally with 16 volunteers carrying oral splints in two independent experiments. Relative biofilm formation was compared with Kruskal-Wallis followed by Bonferroni post-hoc test (α=0.05).

RESULTS

In vitro biofilm formation with optical density values on Zp (0.14±0.01), Zpt (0.14±0.02), Zm (0.13±0.01) and Zmt (0.13±0.01) was significantly lower than on Tp (0.21±0.05) and Z14 (0.20±0.04) (p<0.05). In situ biofilm formation was significantly higher on Z14 (0.56±0.45) (p<0.05), while no significant differences in optical density were observed among Zp (0.25±0.20), Zm (0.36±0.34) and Tp (0.28±0.22). SEM analysis supported quantitative findings.

CONCLUSIONS

In the in vitro three-species biofilm model differences in material and surface roughness affected biofilm formation. In situ biofilm formation was mainly affected by the surface roughness of the specimens. Polishing of zirconia is recommended to reduce biofilm formation while heat-treatment has no significant effect.

Antimicrobial potential of AH Plus supplemented with bismuth lipophilic nanoparticles on E. faecalis isolated from clinical isolates

The objective of this study was to determine the antimicrobial potential of AH plus supplemented with bismuth lipophilic nanoparticles (BisBAL NPs) on the growth of Enterococcus faecalis isolated from patients with endodontic infections. BisBAL NPs, synthesized with the colloidal method, were characterized, in its pure form or AH Plus-absorbed, by energy-dispersive X-ray spectroscopy and scanning electron microscopy (EDS-SEM). Antimicrobial activity was evaluated with disc diffusion assays, and antibiofilm activity with fluorescence microscopy. BisBAL NP-supplemented AH Plus had a 4.9 times higher antimicrobial activity than AH Plus alone (p = 0.0001). In contrast to AH Plus alone, AH Plus supplemented with BisBAL NP inhibited E. faecalis biofilm formation. The sealing properties of AH plus were not modified by the incorporation of BisBAL NPs, which was demonstrated by a 12-day split-chamber leakage assay with daily inoculation, which was used to evaluate the possible filtration of E. faecalis. Finally, BisBAL NP-supplemented AH plus-BisBAL NPs was not cytotoxic for cultured human gingival fibroblasts. Their viability was 83.7% to 89.9% after a 24-h exposure to AH Plus containing 50 and 10 µM BisBAL NP, respectively. In conclusion, BisBAL NP-supplemented AH Plus constitutes an innovative nanomaterial to prevent re-infection in endodontic patients without cytotoxic effects.

Prospective Clinical Evaluation of Posterior Third-Generation Monolithic Zirconia Crowns Fabricated with Complete Digital Workflow: Two-Year Follow-Up

Clinical studies on the behavior of posterior translucent monolithic zirconia restorations are lacking. We assessed the clinical outcome and survival rate of posterior third-generation monolithic zirconia crowns over a 2-year period. A total of 24 patients, requiring 30 posterior full-contour restorations were selected. All abutments were scanned, and crowns were milled and cemented with a self-adhesive dual cure cement. Crowns were assessed using the California Dental Association’s criteria. Gingival status was assessed by evaluating the gingival index, plaque index, periodontal probing depth of the abutments and control teeth, and the margin index of the abutment teeth. Statistical analyses were performed using the Friedman and the Wilcoxon signed-rank tests. During the 2-year follow-up, no biological or mechanical complications were observed, and the survival and success rate was 100%. All restorations ranked as satisfactory throughout the follow-up period. The gingival index and plaque index were worse at the end of the 2-year follow-up. The margin index was stable during the 2 years of clinical service. No significant differences were recorded in periodontal parameters between crowns and control teeth. Third-generation monolithic zirconia could be a reliable alternative to posterior metal–ceramic and second-generation monolithic zirconia posterior crowns.