Physico-chemical properties and healing capacity of potentially bioactive titanium surface

The aim of this study was to evaluate physico-chemical properties and the healing capacity of surface treated titanium. Surface treatment combining sand-blasting, acid etching and alkaline etching (BIO surface) was evaluated together with machined titanium as a reference surface. Hydration, wetting angle, surface area and roughness parameters were evaluated for both surfaces. Stability of dental implants with both surfaces implanted in the tibia of dog was measured during the healing of twelve weeks. BIO surface exhibited lower wetting angle, larger surface area, higher degree of hydration and higher average roughness compared to machined titanium. Implants with the BIO surface maintained their stability during the whole healing period in contrast to those with machined titanium surface, which showed a statistically significant decrease in stability three and nine weeks after implantation.     

Biomimetic Mineralized Fiber Bundle-Inspired Scaffolding Surface on Polyetheretherketone Implants Promotes Osseointegration

The stress shielding effect caused by traditional metal implants is circumvented by using polyetheretherketone (PEEK), due to its excellent mechanical properties; however, the biologically inert nature of PEEK limits its application. Endowing PEEK with biological activity to promote osseointegration would increase its applicability for bone replacement implants. A biomimetic study is performed, inspired by mineralized collagen fiber bundles that contact bone marrow mesenchymal stem cells (BMMSCs) on the native trabecular bone surface. The PEEK surface (P) is first sulfonated with sulfuric acid to form a porous network structure (sP). The surface is then encapsulated with amorphous hydroxyapatite (HA) by magnetron sputtering to form a biomimetic scaffold that resembles mineralized collagen fiber bundles (sPHA). Amorphous HA simulates the composition of osteogenic regions in vivo and exhibits strong biological activity. In vitro results show that more favorable cell adhesion and osteogenic differentiation can be attained with the novelsurface of sPHA than with SP. The results of in vivo experiments show that sPHA exhibits osteoinductive and osteoconductive activity and facilitates bone formation and osseointegration. Therefore, the surface modification strategy can significantly improve the biological activity of PEEK, facilitate effective osseointegration, and inspire further bionic modification of other inert polymers similar to PEEK.     

On the Future Design of Bio‐Inspired Polyetheretherketone Dental Implants

Polyetheretherketone (PEEK) is a promising implant material because of its excellent mechanical characteristics. Although this polymer is a standard material in spinal applications, PEEK is not in use in the manufacturing of dental implants, where titanium is still the most‐used material. This may be caused by its relative bio‐inertness. By the use of various surface modification techniques, efforts have been made to enhance its osseointegrative characteristics to enable the polymer to be used in dentistry. In this feature paper, the state‐of‐the‐art for dental implants is given and different surface modification techniques of PEEK are discussed. The focus will lie on a covalently attached surface layer mimicking natural bone. The usage of such covalently anchored biomimetic composite materials combines many advantageous properties: A biocompatible organic matrix and a mineral component provide the cells with a surrounding close to natural bone. Bone‐related cells may not recognize the implant as a foreign body and therefore, may heal and integrate faster and more firmly. Because neither metal‐based nor ceramics are ideal material candidates for a dental implant, the combination of PEEK and a covalently anchored mineralized biopolymer layer may be the start of the desired evolution in dental surgery.     

The Role of Epigenetic Functionalization of Implants and Biomaterials in Osseointegration and Bone Regeneration—A Review

The contribution of epigenetic mechanisms as a potential treatment model has been observed in cancer and autoimmune/inflammatory diseases. This review aims to put forward the epigenetic mechanisms as a promising strategy in implant surface functionalization and modification of biomaterials, to promote better osseointegration and bone regeneration, and could be applicable for alveolar bone regeneration and osseointegration in the future. Materials and Methods: Electronic and manual searches of the literature in PubMed, MEDLINE, and EMBASE were conducted, using a specific search strategy limited to publications in the last 5 years to identify preclinical studies in order to address the following focused questions: (i) Which, if any, are the epigenetic mechanisms used to functionalize implant surfaces to achieve better osseointegration? (ii) Which, if any, are the epigenetic mechanisms used to functionalize biomaterials to achieve better bone regeneration? Results: Findings from several studies have emphasized the role of miRNAs in functionalizing implants surfaces and biomaterials to promote osseointegration and bone regeneration, respectively. However, there are scarce data on the role of DNA methylation and histone modifications for these specific applications, despite being commonly applied in cancer research. Conclusions: Studies over the past few years have demonstrated that biomaterials are immunomodulatory rather than inert materials. In this context, epigenetics can act as next generation of advanced treatment tools for future regenerative techniques. Yet, there is a need to evaluate the efficacy/cost effectiveness of these techniques in comparison to current standards of care.     

Bioinspired Multi-Layer Biopolymer-Based Dental Implant Coating for Enhanced Osseointegration

The major drawbacks of metal-based implants are weak osseointegration and post-operational infections. These limitations restrict the long-term use of implants that may cause severe tissue damage and replacement of the implant. Recent strategies to enhance the osseointegration process require an elaborate fabrication process and suffer from post-operative complications. To address the current challenges taking inspiration from the extracellular matrix (ECM), the current study is designed to establish enhanced osseointegration with lowered risk of infection. Natural biopolymer pectin, peptide amphiphiles, and enzyme-mimicking fullerene moieties are governed to present an ECM-like environment around the implant surfaces. This multifunctional approach promotes osseointegration via inducing biomineralization and osteoblast differentiation. Application of the biopolymer-based composite to the metal surfaces significantly enhances cellular attachment, supports the mineral deposition, and upregulates osteoblast-specific gene expression. In addition to the osteoinductive properties of the constructed layers, the inherent antimicrobial properties of multilayer coating are also used to prevent infection possibility. The reported biopolymer-artificial enzyme composite demonstrates antimicrobial activity against Escherichia coli and Bacillus subtilis as a multifunctional surface coating.     

Induction of Osseointegration by Nacre in Pigs

Nacre is a biomaterial that has shown osteoinductive and osteoconductive properties in vitro and in vivo. These properties make nacre a material of interest for inducing bone regeneration. However, information is very limited regarding the introduction of nacre to dental implant surgery for promoting osteogenesis. This study investigated the potential of nacre powder for peri-implant bone regeneration in a porcine model. Ninety-six dental implants were placed into the tibia of twelve male domestic pigs. The dental implants were coated with nacre powder from the giant oyster before implantation. Implantations without nacre powder were used as control groups. Euthanization took place at 2, 4 and 6 weeks after implantation, after which we measured bone-to-implant contact (BIC) and bone volume density (BVD) of the implanted bone samples using micro-computed tomography (micro-CT), and examined the histology of the surrounding bone using histological sections stained with Stevenel’s blue and Alizarin red S. The micro-CT analyses showed that the BIC of dental implantations with nacre powder were significantly higher than those without nacre powder, by 7.60%. BVD of implantations with nacre powder were significantly higher than those without nacre powder, by 12.48% to 13.66% in cortical bone, and by 3.37% to 6.11% in spongy bone. Histological study revealed more peri-implant bone regeneration toward the surface of the dental implants after implantation with nacre powder. This was consistent with the micro-CT results. This study demonstrates the feasibility of using nacre to promote peri-implant bone regeneration in dental implantation.     

Interaction of acid and alkali treated titanium with dynamic simulated body environment

Interaction of acid and acid+alkali treated titanium samples with simulated body fluid was studied. In case of alkali treated titanium, the dynamic arrangement of the test enabled the detection of primary calcium and phosphate ion adsorption from the solution and later apatite crystal growth (XRD). The induction time for crystal growth was 24.2±0.3 h. On acid-only treated titanium no crystal growth was detected. The calcium phosphate adsorption layer formed on the acid treated samples was detectable by XPS only, however it differed from that one formed on the acid+alkali treated samples. The adsorption layer formed on the acid+alkali treated samples contained larger amount of calcium, especially in the shortest exposure times. Charging of the apatite crystallites during the XPS measurement enabled the determination their Ca/P ratio separately from Ca/P ratio of the adsorption layers. XPS and EDS analyses indicated that the spherulitic crystallites consisted of carbonated hydroxyapatite with the Ca/P ratio close to that one of the stoichiometric hydroxyapatite. It is proposed that the adsorption layer formed spontaneously and immediately on the acid+alkali treated titanium can provide an ideal interface between the metal implant and the apatite cement line, the first structure formed by osteoblast cells during the formation of the new bone on foreign surfaces. This revised version was published online in August 2006 with corrections to the Cover Date.