Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

Implant surface characteristics, as well as physical and mechanical properties, are responsible for the positive interaction between the dental implant, the bone and the surrounding soft tissues. Unfortunately, the dental implant surface does not remain unaltered and changes over time during the life of the implant. If changes occur at the implant surface, mucositis and peri-implantitis processes could be initiated; implant osseointegration might be disrupted and bone resorption phenomena (osteolysis) may lead to implant loss. This systematic review compiled the information related to the potential sources of titanium particle and ions in implant dentistry. Research questions were structured in the Population, Intervention, Comparison, Outcome (PICO) framework. PICO questionnaires were developed and an exhaustive search was performed for all the relevant studies published between 1980 and 2018 involving titanium particles and ions related to implant dentistry procedures. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed for the selection and inclusion of the manuscripts in this review. Titanium particle and ions are released during the implant bed preparation, during the implant insertion and during the implant decontamination. In addition, the implant surfaces and restorations are exposed to the saliva, bacteria and chemicals that can potentially dissolve the titanium oxide layer and, therefore, corrosion cycles can be initiated. Mechanical factors, the micro-gap and fluorides can also influence the proportion of metal particles and ions released from implants and restorations.

https://www.mdpi.com/1422-0067/19/11/3585/pdf

Potential Causes of Titanium Particle and Ion Release in Implant Dentistry: A Systematic Review

After using cast titanium prostheses in clinical dental practice, severe wear of titanium teeth has been observed. This in vitro study evaluated the wear behavior of teeth made with several cast titanium alloys containing copper (CP Ti+3.0 wt% Cu; CP Ti+5.0 wt% Cu; Ti-6Al-4V +1.0 wt% Cu; Ti-6Al-4V+4.0 wt% Cu) and compared the results with those for commercially pure (CP) titanium, Ti-6Al-4V, and gold alloy. Wear testing was performed by repeatedly grinding upper and lower teeth under flowing water in an experimental testing apparatus. Wear resistance was assessed as volume loss (mm(3)) at 5kgf (grinding force) after 50,000 strokes. Greater wear was found for the six types of titanium than for the gold alloy. The wear resistance of the experimental CP Ti+Cu and Ti-6Al-4V+Cu alloys was better than that of CP titanium and Ti-6Al-4V, respectively. Although the gold alloy had the best wear property, the 4% Cu in Ti-6Al-4V alloy exhibited the best results among the titanium metals. Alloying with copper, which introduced the alpha Ti/Ti(2)Cu eutectoid, seemed to improve the wear resistance.

Wear resistance of experimental Ti-Cu alloys

Cathodic arc deposition of ceramic coatings is gaining importance due to their good adhesion and minimum residual stresses. In this work we have arc deposited TiN coatings on Ti6Al4V alloy and evaluated their mechanical, corrosion, in vitro tribological and biological properties for implant applications. Coatings exhibited high hardness of 33.4 ± 10 GPa and Young's modulus of 458.4 ± 79 GPa. Scratch tests revealed that the coatings fail adhesively at 2.9 ± 0.3 GPa. Hydrophilic nature of the coatings enabled protein adsorption leading to surface passivation and significant increase in the in vitro corrosion resistance. The inherent in vitro wear rate of the coatings was 6.8 ± 1.7 × 10−7 mm3/N·m against Al2O3 ball. The wear rate of ultrahigh molecular weight polyethylene tested against TiN coatings was 1.9 ± 0.7 × 10−5 mm3/N·m, which appears to be better than against CoCrMo alloy. In vitro biocompatibility studies performed using mouse embryonic fibroblast cell line (NIH3T3) demonstrated that the coatings are non-toxic and exhibit excellent cell-materials interactions. Further improvement in the performance of present cathodic arc deposited TiN coatings can be achieved by minimizing/eliminating coating defects such as pits and macro/micro particles, which accelerated the localized damage during articulation.

Mechanical, wear, corrosion and biological properties of arc deposited titanium nitride coatings

A large portion of the global human population carries a type of medical implant. Dental implants are an important part of this category, and the crowns they support are vital for satisfying the patients' needs both functionally and aesthetically. Materials science pertaining to dental crowns is a driver of their development, and currently zirconium oxide (zirconia) is a promising non-metal alternative, exhibiting biocompatibility and excellent mechanical and aesthetic properties. This review aims to collate a selection of the extensive testing and research that has been performed and evaluated on a variety of zirconia-based ceramics, as there are many commercial brands developing blank and powdered samples for refinement into structurally sound dental prosthetics. Significant advancements regarding manufacturing technologies for zirconia-based ceramics are also currently in progress. Methodologies and conditions for uniaxial and isostatic pressing of zirconia powder are reviewed, as are the benefits of emerging CAD/CAM technologies. Several knowledge gaps were identified based on this review, primarily that different sintering conditions and methodologies, such as two-step sintering, should be investigated experimentally. Preliminary studies using alternative methods show promising results, and further trialling would help to ensure that the mechanical, aesthetic and ageing properties of the final product are enhanced and optimised.

Zirconia in dental prosthetics: A literature review

Degradation mechanisms and future challenges of titanium and its alloys for dental implant applications in oral environment.

Titanium alloys have created a biomedical revolution in the past three decades and several research works are being carried out globally to combat the day to day challenges posed by the biomedical industries to meet the needs of a patient-friendly implant. Enhancement of corrosion and wear resistance of titanium alloys serve as the major treat for the stability of implant material after implantation. These problems could be overcome through various objectives, one among them being alloying titanium with non-toxic β-stabilizer elements to both increase the surface-related properties and improve biocompatibility. Other objectives include surface engineering methods such as coating, oxidation, nanograined surface and laser texturing. Overall, in this article an attempt has been made to bring out the current advances in the development of highly stable Ti-alloys with superior corrosion and wear resistance through various processes has been reviewed in detail.

Current advances in enhancement of wear and corrosion resistance of titanium alloys – a review

Surface properties and cytocompatibility of Ti-6Al-4V fabricated using Laser Engineered Net Shaping.

Hydroxyapatite–titanium dioxide (HAp-TiO2) nanohybrid composite was coated on Ti–6Al–4V and Ti–13Nb–13Zr substrates by electrophoretic deposition. Coating surface characteristics and biocompatibility were analysed using X-ray photoelectron spectroscopy, water contact measurement, scanning electron microscopy and fluorescence microscopy. The results indicated high degree of crystallinity and densely packed crack free morphology of the coating. The coated substrates displayed lower contact angle (Ti–13Nb–13Zr, 17·4°; Ti–6Al–4V, 22·2°) than the controls (Ti–13Nb–13Zr, 80·8°; Ti–6Al–4V, 72·6°). The cytocompatibility of the coated substrates was determined by staining the human dermal fibroblast cells with 4′,6-diamidino-2-phenylindole and imaging under fluorescent microscope. Both SEM and florescence microscope images showed comparatively enhanced cell adhesion on coated Ti–13Nb–13Zr and Ti–6Al–4V than the uncoated substrates. This difference could be attributed because of the higher wettability of Ti–13Nb–13...

Surface modification of Ti–13Nb–13Zr and Ti–6Al–4V using electrophoretic deposition (EPD) for enhanced cellular interaction

Biomaterials play a crucial role in regenerative medicine, which aims to restore and reinstate lost/failed tissues or organs in the human body. Biomaterials are three dimensional temporary substrates which help in the development of new tissue and organization. Mimicking the characteristics of natural bone is challenging and those biomaterials which posses that property serves beneficial and also helps in the speedy recovery of the patient. These characteristics are of nanoscale regime and helps in wounding healing and tissue regeneration in the most effective way. In this chapter the development of nanostructured biomaterials, nanosurface modifications and nanoscaffolds has been discussed in detail. The different application of these bulk and surface modified nanomaterials has been convened. In conclusion, the nanostructured biomaterials is an emerging area of research and the application of these materials can improve the performance and longevity of the implants and at the same time pave way for the development of new technologies in the future.

Revathi A

Papers

Degradation mechanisms and future challenges of titanium and its alloys for dental implant applications in oral environment.

Current advances in enhancement of wear and corrosion resistance of titanium alloys – a review

Surface properties and cytocompatibility of Ti-6Al-4V fabricated using Laser Engineered Net Shaping.

Surface modification of Ti–13Nb–13Zr and Ti–6Al–4V using electrophoretic deposition (EPD) for enhanced cellular interaction

Use of nanostructured materials in implants