The bisphosphonate pamidronate on the surface of titanium stimulates bone formation around tibial implants in rats

LL-37 and bisphosphonate co-delivery 3D-scaffold with antimicrobial and antiresorptive activities for bone regeneration

This study introduces a novel 3D scaffold for bone regeneration, composed of silk fibroin, chitosan, nano-hydroxyapatite, LL-37 antimicrobial peptide, and pamidronate. The scaffold addresses a critical need in bone tissue engineering by simultaneously combating bone infections and promoting bone growth. LL-37 was incorporated for its broad-spectrum antimicrobial properties, while pamidronate was included to inhibit bone resorption. The scaffold's porous structure, essential for cell infiltration and nutrient diffusion, was achieved through a freeze-drying process. In vitro assessments using SEM and FTIR confirmed the scaffold's morphology and chemical integrity. Antimicrobial efficacy was tested against pathogens of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). In vivo studies in a murine model of infectious bone defect revealed the scaffold's effectiveness in reducing inflammation and bacterial load, and promoting bone regeneration. RNA sequencing of treated specimens provided insights into the molecular mechanisms underlying these observations, revealing significant gene expression changes related to bone healing and immune response modulation. The results indicate that the scaffold effectively inhibits bacterial growth and supports bone cell functions, making it a promising candidate for treating infectious bone defects. Future studies should focus on optimizing the release of therapeutic agents and evaluating the scaffold's clinical potential.

Photothermal Antibacterial and Osteoinductive Polypyrrole@Cu Implants for Biological Tissue Replacement

The treatment of bone defects caused by disease or accidents through the use of implants presents significant clinical challenges. After clinical implantation, these materials attract and accumulate bacteria and hinder the integration of the implant with bone tissue due to the lack of osteoinductive properties, both of which can cause postoperative infection and even lead to the eventual failure of the operation. This work successfully prepared a novel biomaterial coating with multiple antibacterial mechanisms for potent and durable and osteoinductive biological tissue replacement by pulsed PED (electrochemical deposition). By effectively regulating PPy (polypyrrole), the uniform composite coating achieved sound physiological stability. Furthermore, the photothermal analysis showcased exceptional potent photothermal antibacterial activity. The antibacterial assessments revealed a bacterial eradication rate of 100% for the PPy@Cu/PD composite coating following a 24 h incubation. Upon the introduction of NIR (near-infrared) irradiation, the combined effects of multiple antibacterial mechanisms led to bacterial reduction rates of 99% for E. coli and 98% for S. aureus after a 6 h incubation. Additionally, the successful promotion of osteoblast proliferation was confirmed through the application of the osteoinductive drug PD (pamidronate disodium) on the composite coating's surface. Therefore, the antimicrobial Ti-based coatings with osteoinductive properties and potent and durable antibacterial properties could serve as ideal bone implants.

Zoledronate Promotes Peri-Implant Osteogenesis in Diabetic Osteoporosis by the AMPK Pathway

Together with diabetic osteoporosis (DOP), diabetes patients experience poor peri-implant osteogenesis following implantation for dentition defects. Zoledronate (ZOL) is widely used to treat osteoporosis clinically. To evaluate the mechanism of ZOL for the treatment of DOP, experiments with DOP rats and high glucose-grown MC3T3-E1 cells were used. The DOP rats treated with ZOL and/or ZOL implants underwent a 4-week implant-healing interval, and then microcomputed tomography, biomechanical testing, and immunohistochemical staining were performed to elucidate the mechanism. In addition, MC3T3-E1 cells were maintained in an osteogenic medium with or without ZOL to confirm the mechanism. The cell migration, cellular actin content, and osteogenic differentiation were evaluated by a cell activity assay, a cell migration assay, as well as alkaline phosphatase, alizarin red S, and immunofluorescence staining. The mRNA and protein expression of adenosine monophosphate-activated protein kinase (AMPK), phosphorylated AMPK (p-AMPK), osteoprotegerin (OPG), receptor activator of nuclear factor kappa B ligand (RANKL), bone morphogenetic protein 2 (BMP2), and collagen type I (Col-I) were detected using real-time quantitative PCRs and western blot assays, respectively. In the DOP rats, ZOL markedly improved osteogenesis, enhanced bone strength and increased the expression of AMPK, p-AMPK, and Col-I in peri-implant bones. The in vitro findings showed that ZOL reversed the high glucose-induced inhibition of osteogenesis via the AMPK signaling pathway. In conclusion, the ability of ZOL to promote osteogenesis in DOP by targeting AMPK signaling suggests that therapy with ZOL, particularly simultaneous local and systemic administration, may be a unique approach for future implant repair in diabetes patients.

Drug-Releasing Gelatin Coating Reinforced with Calcium Titanate Formed on Ti–6Al–4V Alloy Designed for Osteoporosis Bone Repair

Ti–6Al–4V alloy has been widely used in the orthopedic and dental fields owing to its high mechanical strength and biocompatibility. However, this alloy has a poor bone-bonding capacity, and its implantation often causes loosening. Osteoporosis increases with the aging of the population, and bisphosphonate drugs such as alendronate and minodronate (MA) are used for the medical treatment. Reliable and multifunctional implants showing both bone bonding and drug releasing functions are desired. In this study, we developed a novel organic-inorganic composite layer consisting of MA-containing gelatin and calcium-deficient calcium titanate (cd–CT) with high bone-bonding and scratch resistance on Ti–6Al–4V alloy. The alloy with the composite layer formed apatite within 7 days in a simulated body fluid and exhibited high scratch resistance of an approximately 50 mN, attributable to interlocking with cd ± CT. Although the gelatin layer almost completely dissolved in phosphate-buffered saline within 6 h, its dissolution rate was significantly suppressed by a subsequent thermal crosslinking treatment. The released MA was estimated at more than 0.10 μmol/L after 7 days. It is expected that the Ti alloy with the MA-containing gelatin and cd–CT composite layer will be useful for the treatment of osteoporosis bone.

Evaluation of bone formation on orthopedic implant surfaces using an ex-vivo bone bioreactor system

Recent advances in materials and manufacturing processes have allowed the fabrication of intricate implant surfaces to facilitate bony attachment. However, refinement and evaluation of these new design strategies are hindered by the cost and complications of animal studies, particularly during early iterations in the development process. To address this problem, we have previously constructed and validated an ex-vivo bone bioreactor culture system that can maintain the viability of bone samples for an extended period ex-vivo. In this study, we investigated the mineralization of a titanium wire mesh scaffold under both static and dynamic culturing using our ex vivo bioreactor system. Thirty-six cancellous bone cores were harvested from bovine metatarsals at the time of slaughter and divided into five groups under the following conditions: Group 1) Isolated bone cores placed in static culture, Group 2) Unloaded bone cores placed in static culture in contact with a fiber-mesh metallic scaffold, Group 3) Bone cores placed in contact with a fiber-mesh metallic scaffold under the constant pressure of 150 kPa, Group 4) Bone core placed in contact with a fiber-mesh metallic scaffold and exposed to cyclic loading with continuous perfusion flow of media within the ex-vivo culture system and Group 5) Bone core evaluated on Day 0 to serve as a positive control for comparison with all other groups at weeks 4 and 7. Bone samples within Groups 1-4 were incubated for 4 and 7 weeks and then evaluated using histological examination (H&E) and the Live-Dead assay (Life Technologies). Matrix deposits on the metallic scaffolds were examined with scanning electron microscopy (SEM), while the chemical composition of the matrix was measured using energy-dispersive x-ray spectroscopy (EDX). We found that the viability of bone cores was maintained after seven weeks of loading in our ex vivo system. In addition, SEM images revealed crystallite-like structures on the dynamically loaded metal coupons (Group 4), corresponding to the initial stages of mineralization. EDX results further confirmed the presence of carbon at the interface and calcium phosphates in the matrix. We conclude that a bone bioreactor can be used as an alternate tool for in-vivo bone ingrowth studies of new implant surfaces or coatings.

Surface decoration of development-inspired synthetic N-cadherin motif via Ac-BP promotes osseointegration of metal implants

Research works on the synergistic effect of surface modified bioactive molecules and bone metal implants have been highlighted. N-cadherin is regarded as a key factor in directing cell-cell interactions during the mesenchymal condensation preceding the osteogenesis in the musculoskeletal system. In this study, the N-cadherin mimetic peptide (Cad) was biofunctionalized on the titanium metal surface via the acryloyl bisphosphonate (Ac-BP). To learn the synergistic effect of N-cadherin mimetic peptide, when tethered with titanium substrates, on promoting osteogenic differentiation of the seeded human mesenchymal stem cells (hMSCs) and the osseointegration at the bone-implant interfaces. Results show that the conjugation of N-cadherin mimetic peptide with Ac-BP promoted the osteogenic gene markers expression in the hMSCs. The biofunctionalized biomaterial surfaces promote the expression of the Wnt/β-catenin downstream axis in the attached hMSCs, and then enhance the in-situ bone formation and osseointegration at the bone-implant interfaces. We conclude that this N-cadherin mimetic peptide tethered on Ti surface promote osteogenic differentiation of hMSCs and osseointegration of biomaterial implants in vitro and in vivo. These findings demonstrate the importance of the development-inspired surface bioactivation of metal implants and shed light on the possible cellular mechanisms of the enhanced osseointegration.

Evaluation of annealed titanium oxide nanotubes on titanium: From surface characterization to in vivo assays

The entire route from anodic oxidation and surface characterization, including in vitro experiments and finally in vivo osseointegration assays were performed with the aim to evaluate nanotubular and crystalline annealed titanium oxides as a suitable surface for grade 2 titanium permanent implants. Polished titanium (T0) was compared with anodized surfaces obtained in acidic media with fluoride, leading to an ordered nanotubular structure of titanium oxide on the metal surface, characterized by tube diameter of 89 ± 24 nm (Tnts). Samples were thermally treated in air (TntsTT) to increase the anatase crystalline phase on nanotubes, with minor alteration of the structure. Corrosion tests were performed to evaluate the electrochemical response after 1, 14, and 28 days of immersion in simulated body fluid. Based on the in vitro results, heat-treated titanium nanotubes (TntsTT) were selected as a promissory candidate to continue with the osseointegration in vivo assays. The in vivo results showed no major improvement in the osseointegration process when compared with untreated Ti after 30 days of implantation and there also was a lower increase in the development of new osseous tissue.

Total hip arthroplasty in patients with osteoporosis

There is a high prevalence of osteoporosis in patients undergoing total hip arthroplasty. There are several clinically relevant questions related to the management of such cases: the effect of ageing; the initial osseointegration of implants, especially when cementless THA is used; the effect of medical osteoporosis treatment on bone-implant interface; the incidence of intraoperative and late periprosthetic fractures, and the long-term survival of both cemented and cementless total hip arthroplasty performed for proximal femoral fractures and hip osteoarthritis. A critical review of the literature is presented in an attempt to draw practical conclusions.

Adjuvant Drug-Assisted Bone Healing: Advances and Challenges in Drug Delivery Approaches

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Alendronate-Anionic Clay Nanohybrid for Enhanced Osteogenic Proliferation and Differentiation

BACKGROUND

Alendronate (AL), a drug for inhibiting osteoclast-mediated bone-resorption, was intercalated into an inorganic drug delivery nanovehicle, layered double hydroxide (LDH), to form a new nanohybrid, AL-LDH, with 1:1 heterostructure along the crystallographic C-axis. Based on the intercalation reaction strategy, the present AL-LDH drug delivery system (DDS) was realized with an enhanced drug efficacy of AL, which was confirmed by the improved proliferation and osteogenic differentiation of osteoblast-like cells (MG63).

METHODS

The AL-LDH nanohybrid was synthesized by conventional ion-exchange reaction and characterized by powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared (FT-IR) spectroscopy. Additionally, in vitro efficacy tests, such as cell proliferation and alkaline phosphatase (ALP) activity, were analyzed.

RESULTS

The AL was successfully intercalated into LDH via ion-exchange reaction, and thus prepared AL-LDH DDS was X-ray single phasic and chemically well defined. The accumulated AL content in MG63 cells treated with the AL-LDH DDS nanoparticles was determined to be 10.6-fold higher than that within those treated with the intact AL after incubation for 1 hour, suggesting that intercellular permeation of AL was facilitated thanks to the hybridization with drug delivery vehicle, LDH. Furthermore, both in vitro proliferation level and ALP activity of MG63 treated with the present hybrid drug, AL-LDH, were found to be much more enhanced than those treated with the intact AL. This is surely due to the fact that LDH could deliver AL drug very efficiently, although LDH itself does not show any effect on proliferation and osteogenic differentiation of MG63 cells.

CONCLUSION

The present AL-LDH could be considered as a promising DDS for improving efficacy of AL.

Recent progress on fabrication and drug delivery applications of nanostructured hydroxyapatite

Through this brief review, we provide a comprehensive historical background of the development of nanostructured hydroxyapatite (nHAp), and its application potentials for controlled drug delivery, drug conjugation, and other biomedical treatments. Aspects associated with efficient utilization of hydroxyapatite (HAp) nanostructures such as their synthesis, interaction with drug molecules, and other concerns, which need to be resolved before they could be used as a potential drug carrier in body system, are discussed. This review focuses on the evolution of perceptions, practices, and accomplishments in providing improved delivery systems for drugs until date. The pioneering developments that have presaged today's fascinating state of the art drug delivery systems based on HAp and HAp-based composite nanostructures are also discussed. Special emphasis has been given to describe the application and effectiveness of modified HAp as drug carrier agent for different diseases such as bone-related disorders, carriers for antibiotics, anti-inflammatory, carcinogenic drugs, medical imaging, and protein delivery agents. As only a very few published works made comprehensive evaluation of HAp nanostructures for drug delivery applications, we try to cover the three major areas: concepts, practices and achievements, and applications, which have been consolidated and patented for their practical usage. The review covers a broad spectrum of nHAp and HAp modified inorganic drug carriers, emphasizing some of their specific aspects those needed to be considered for future drug delivery applications. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Nanotechnology Approaches to Biology > Cells at the Nanoscale.

[Formation of bone in critical calvarias defects in rats under the influence of bisphosphonate alendronate Na complex]

The aim of the study was to investigate dynamic of tissue structures in critical defects of calvaria of rats after inoculation of bisphosphonate (BF) alendronate Na complex into bone defects. Animal model included 24 Wistar rats divided in 3 groups: spontaneous healing under blot clot (1), inoculation of carbonate hydroxide apatite β-tricalcium phosphate blocks (2) and BF alendronate Na complex (3) on 15, 30, 60 and 90 experiment day. New bone formation was observed in group 3 as opposed to groups 1 and 2.

In vitro and in vivo characterization of anodised zirconium as a potential material for biomedical applications

In vitro studies offer the insights for the understanding of the mechanisms at the tissue-implant interface that will provide an effective functioning in vivo. The good biocompatibility of zirconium makes a good candidate for biomedical applications and the attractive in vivo performance is mainly due to the presence of a protective oxide layer. The aim of this study is to evaluate by in vitro and in vivo approach, the influence of surface modification achieved by anodisation at 30 and 60V on zirconium implants on the first steps of the osseointegration process. In this study cell attachment, proliferation and morphology of mouse myoblast C2C12-GFP and in mouse osteoprogenitor MC3T3-E1 cells was evaluated. Also, together with the immune system response, osteoclast differentiation and morphology with RAW 264.7 murine cell line were analysed. It was found that anodisation treatment at 60V enhanced cell spreading and the osteoblastic and osteoclastic cells morphology, showing a strong dependence on the surface characteristics. In vivo tests were performed in a rat femur osteotomy model. Dynamical and static histological and histomorphometric analyses were developed 15 and 30days after surgery. Newly formed bone around Zr60V implants showed a continuous newly compact and homogeneous bone just 15 after surgery, as judged by the enhanced thickness and mineralization rate. The results indicate that anodising treatment at 60V could be an effective improvement in the osseointegration of zirconium by stimulating adhesion, proliferation, morphology, new bone thickness and bone mineral apposition, making zirconium an emerging candidate material for biomedical applications.

Does Local Ibandronate and/or Pamidronate Delivery Enhance Osseointegration? A Systematic Review

PURPOSE

To our knowledge from indexed literature, the present study is the first one to systematically review the influence of local delivery of pamidronate (PAM) and/or ibandronate (IBA) on osseointegration enhancement. The aim of the present systematic review was to assess the efficacy of IBA and/or PAM local delivery (topically or coating on implants surfaces) in promoting osseointegration.

MATERIALS AND METHODS

To address the focused question, "Does local IBA and/or PAM delivery enhances osseointegration?," indexed databases were searched without time or language restrictions up to and including May 2016 using various combinations of the following keywords: "pamidronate," "ibandronate," "bisphosphonates," "osseointegration," and "topical administration." Letters to the Editor, historic reviews, commentaries, case series, and case reports were excluded.

RESULTS

Fifteen studies were included. Fourteen studies were performed in animals and 2 were clinical trials. One study reported an experimental model and a clinical trial in the same publication. Results from 12 experimental studies and 2 clinical studies reported improved biomechanical properties and/or osseointegration around implants with PAM and/or IBA. Two experimental studies showed that PAM and/or IBA did not improve osseointegration.

CONCLUSIONS

On experimental grounds, local IBA and/or PAM delivery seems to enhance osseointegration; however, from a clinical perspective, further randomized control trials are needed to assess the effectiveness of IBA and PAM in promoting osseointegration around dental implants.

Potential Applications of Biphosphonates in Dental Surgical Implants

Biphosphonates are largely used for their unquestionable properties of inhibiting bone resorption by osteoclast in the treatment of various osteometabolic illnesses such as osteoporosis, multiple myeloma, tumors which metastasize to the bone and malignant hypercalcemia. In this literature review the physico-chemical properties, biologic activities and the mechanisms of action of biphosphonates are described. The use of these drugs is discussed, analyzing the quantity of results which have emerged through in vitro and in vivo experiments on animal models. In this study the efficiency of these drugs is demonstrated in contrasting the osteolitic processes of the alveolar bone, in promoting the neoformation and in bettering the quality of bone implants. However, it is important to draw attention to a worrying correlation which has emerged during the last 3–4 years, between osteonecrosis of the jaw (ONJ) and the systemic administration of aminobiphosphonates. This collateral effect did not emerge following the use of non-aminobiphosphonates. The aim of this revie w is to identify the guidelines for the use of biphosphonates in oral implant surgery.

Single-dose local simvastatin injection improves implant fixation via increased angiogenesis and bone formation in an ovariectomized rat model

Background

Statins have been reported to promote bone formation. However, taken orally, their bioavailability is low to the bones. Implant therapies require a local repair response, topical application of osteoinductive agents, or biomaterials that promote implant fixation.

Material/Methods

The present study evaluated the effect of a single local injection of simvastatin on screw fixation in an ovariectomized rat model of osteoporosis.

Results

Dual-energy X-ray absorptiometry, micro-computed tomography, histology, and biomechanical tests revealed that 5 and 10 mg simvastatin significantly improved bone mineral density by 18.2% and 22.4%, respectively (P<0.05); increased bone volume fraction by 51.0% and 57.9%, trabecular thickness by 16.4% and 18.9%, trabeculae number by 112.0% and 107.1%, and percentage of osseointegration by 115.7% and 126.3%; and decreased trabeculae separation by 34.1% and 36.6%, respectively (all P<0.01). Bone mineral apposition rate was significantly increased (P<0.01). Furthermore, implant fixation was significantly increased (P<0.05), and bone morphogenetic protein 2 (BMP2) expression was markedly increased. Local injection of a single dose of simvastatin also promoted angiogenesis. Vessel number, volume, thickness, surface area, and vascular volume per tissue volume were significantly increased (all P<0.01). Vascular endothelial growth factor (VEGF), VEGF receptor-2, von Willebrand factor, and platelet endothelial cell adhesion molecule-1 expression were enhanced.

Conclusions

A single local injection of simvastatin significantly increased bone formation, promoted osseointegration, and enhanced implant fixation in ovariectomized rats. The underlying mechanism appears to involve enhanced BMP2 expression and angiogenesis in the target bone.

Latham J, G. Dunlop D, Oreffo RO. Bone and metal: an orthopaedic perspective on osseointegration of metals

The area of implant osseointegration is of major importance, given the predicted significant rise in the number of orthopaedic procedures and an increasingly ageing population. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant bulk properties and surface characteristics. Our understanding and ability to modify these mechanisms through alterations in implant design is continuously expanding. The following review considers the main aspects of material and surface alterations in metal implants, and the extent of their subsequent influence on osseointegration. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. The complexity of achieving this outcome through incorporation and balance of contributory factors is highlighted through a clinical case report.

Bioactive coatings for orthopaedic implants-recent trends in development of implant coatings

Joint replacement is a major orthopaedic procedure used to treat joint osteoarthritis. Aseptic loosening and infection are the two most significant causes of prosthetic implant failure. The ideal implant should be able to promote osteointegration, deter bacterial adhesion and minimize prosthetic infection. Recent developments in material science and cell biology have seen the development of new orthopaedic implant coatings to address these issues. Coatings consisting of bioceramics, extracellular matrix proteins, biological peptides or growth factors impart bioactivity and biocompatibility to the metallic surface of conventional orthopaedic prosthesis that promote bone ingrowth and differentiation of stem cells into osteoblasts leading to enhanced osteointegration of the implant. Furthermore, coatings such as silver, nitric oxide, antibiotics, antiseptics and antimicrobial peptides with anti-microbial properties have also been developed, which show promise in reducing bacterial adhesion and prosthetic infections. This review summarizes some of the recent developments in coatings for orthopaedic implants.

Can anodised zirconium implants stimulate bone formation? Preliminary study in rat model

The mechanical properties and good biocompatibility of zirconium and some of its alloys make these materials good candidates for biomedical applications. The attractive in vivo performance of zirconium is mainly due to the presence of a protective oxide layer. In this preliminary study, the surface of pure zirconium modified by anodisation in acidic media at low potentials to enhance its barrier protection given by the oxides and osseointegration. Bare, commercially pure zirconium cylinders were compared to samples anodised at 30 V through electrochemical tests and scanning electron microscopy (SEM). For both conditions, in vivo tests were performed in a rat tibial osteotomy model. The histological features and fluorochrome-labelling changes of newly bone formed around the implants were evaluated on the non-decalcified sections 63 days after surgery. Electrochemical tests and SEM images show that the anodisation treatment increases the barrier effect over the material and the in vivo tests show continuous newly formed bone around the implant with a different amount of osteocytes in their lacunae depending on the region. There was no significant change in bone thickness around either kind of implant but the anodised samples had a significantly higher mineral apposition, suggesting that the anodisation treatment stimulates and assists the osseointegration process. We conclude that anodisation treatment at 30 V can stimulate the implant fixation in a rat model, making zirconium a strong candidate material for permanent implants.

A brief historical perspective on dental implants, their surface coatings and treatments

This review highlights a brief, chronological sequence of the history of dental implants. This historical perspective begins with ancient civilizations and spotlights predominant dentists and their contributions to implant development through time. The physical, chemical and biologic properties of various dental implant surfaces and coatings are discussed, and specific surface treatments include an overview of machined implants, etched implants, and sand-blasted implants. Dental implant coatings such as hydroxyapatite, fluoride, and statin usage are further reviewed.

The topical administration of bisphosphonates in implant surgery: a randomized split-mouth prospective study with a follow-up up to 5 years

OBJECTIVE

To evaluate the efficacy of the topical administration of bisphosphonates in implant therapy.

MATERIALS AND METHODS

Thirty-nine consecutive patients were selected for a split-mouth study. Inclusion criteria were: presence of a bilateral or total edentulism, ability to tolerate conventional implant procedures, older than 18 years. Ten patients were smokers. Ten patients were fully edentulous in both maxilla and mandible, 12 patients had fully edentulous maxilla or mandible, and 17 were bilaterally partially edentulous (9 in the mandible and 8 in the maxilla). A one-stage procedure was adopted in all cases. The prosthetic phase started 10 weeks after implant insertion. Each patient received implants on the control side and the test side, with insertion performed in the conventional way on the control side; on the test side, a 3% clodronate solution mixed with a surfactant (Tween-20) at a 1:3 ratio was topically administered both at the implant surface and at the implant site.

RESULTS

One hundred fifty-five implants were inserted. The test and control groups included 75 and 80 implants, respectively. The implant insertion torque was no less than 30 Ncm. A total of 7 implants failed in the control group (6 before loading and one after 12 months of loading). No failure occurred on the test side. By the 5-year follow-up, no further implant failure had been recorded. Overall, implant survival rates at 5 years for the test and control groups were, respectively, 100% and 91.3%, the difference being significant (p < .01). Mean marginal bone loss was 0.85 ± 0.71 mm in the test group and 1.12 ± 0.85 mm in the control group after 1 year of loading and stable thereafter. The difference was not significant.

CONCLUSIONS

The topical administration of bisphosphonates may positively affect implant survival in the preloading and postloading phases in partially and fully edentulous patients. However, a larger study population is needed to verify these promising clinical results.

Taking a deep look: modern microscopy technologies to optimize the design and functionality of biocompatible scaffolds for tissue engineering in regenerative medicine

This review focuses on modern nonlinear optical microscopy (NLOM) methods that are increasingly being used in the field of tissue engineering (TE) to image tissue non-invasively and without labelling in depths unreached by conventional microscopy techniques. With NLOM techniques, biomaterial matrices, cultured cells and their produced extracellular matrix may be visualized with high resolution. After introducing classical imaging methodologies such as µCT, MRI, optical coherence tomography, electron microscopy and conventional microscopy two-photon fluorescence (2-PF) and second harmonic generation (SHG) imaging are described in detail (principle, power, limitations) together with their most widely used TE applications. Besides our own cell encapsulation, cell printing and collagen scaffolding systems and their NLOM imaging the most current research articles will be reviewed. These cover imaging of autofluorescence and fluorescence-labelled tissue and biomaterial structures, SHG-based quantitative morphometry of collagen I and other proteins, imaging of vascularization and online monitoring techniques in TE. Finally, some insight is given into state-of-the-art three-photon-based imaging methods (e.g. coherent anti-Stokes Raman scattering, third harmonic generation). This review provides an overview of the powerful and constantly evolving field of multiphoton microscopy, which is a powerful and indispensable tool for the development of artificial tissues in regenerative medicine and which is likely to gain importance also as a means for general diagnostic medical imaging.

Effect of implanted bisphosphonate-enriched cement on the trabecular microarchitecture of bone in a rat model using micro-computed tomography

PURPOSE

Bisphosphonates (BPs) are antiresorptive drugs typically used to inhibit bone resorption. The latest reports show that BPs play an important role in not only achieving better bone mineral density but also in improving bone microarchitecture. The mechanism of action of the BPs is complex and multifactorial. We tried to determine whether there are any changes in the microarchitectural bone structure during local use of BP (Pamifos 60). The aim of this study was to see if BP-enriched cement used in rat models had positive effects on bone formation.

METHODS

Research was performed on 40 adult male Wistar rats that were divided into four groups: two control groups and two experimental groups. Rats in the experimental groups were implanted with BP-enriched cement into the bone, while the control group rats were implanted with clean bone cement (without BP). Micro-computed tomography was applied for the investigation of trabecular microarchitecture of the proximal physis of the tibial bone in all animals three and six weeks after surgery. In all microCT images variables such as bone volume density (BV/TV), trabecular thickness (TbTh), trabecular separation (TbSp) and trabecular number (TbN) were used to describe trabecular bone morphometry.

RESULTS

The major finding of this study is that using BP-enriched cement results in distinct changes in bone microarchitecture. We showed that local use of pamidronate (Pamifos 60) in orthopaedic cement had a positive effect on bone formation. It significantly changed three variables. We noticed increasing bone volume fraction and trabecular thickness together with decreasing trabecular separation.

CONCLUSION

In this paper we demonstrate the efficacy of using BP-enriched cement in vitro in the tibiae of rats. Our most significant finding based on micro-CT picture analysis allows us to start further work on more suitable applications of BP-enriched cement in humans. We believe that future successful experiments will facilitate potential use of BP-enriched cement in clinical applications.

Early healing of hydroxyapatite-coated implants in grafted bone of zoledronic acid-treated osteoporotic rabbits

BACKGROUND

Resorption of grafted bone and delayed osseointegration of implants are main problems associated with alveolar bone augmentation in dental implantology, especially for patients with osteoporosis. The aim of this study is to investigate the early healing response of implants to systemic treatment of zoledronic acid (ZA) in autogenous grafted iliac bone of osteoporotic rabbits.

METHODS

Ovariectomy (OVX) or sham operation was performed in 46 rabbits, and osteoporotic changes were verified in animals receiving OVX 3 months later. The remaining animals were divided into three groups (n = 12): sham, OVX, and OVX with ZA treatment (ZA group). Autogenous iliac bone grafting was performed in bilateral tibiae, and hydroxyapatite-coated titanium implants were simultaneously placed into the grafted bone. The animals were sacrificed 2 and 8 weeks later for examination.

RESULTS

At both time points, systemic treatment of ZA efficiently promoted bone healing of implants in grafted bone, and all histologic and microcomputed tomography bone indices, including mineralized bone volume, implant-bone contact ratio, connectivity density, trabecular thickness, and trabecular number, were significantly increased in the ZA group compared with the OVX-only group (P <0.01); implant-bone contact rates in the ZA group were even restored to levels similar to those of sham-operated animals (P >0.05). Furthermore, biomechanical testing demonstrated that removal torque of implants was significantly increased in the ZA group compared with the OVX group (P <0.01).

CONCLUSION

Systemic treatment with ZA could efficiently promote early bone healing of implants in autogenous grafted bone of osteoporotic rabbits by increasing early osseointegration and fixation of implants.

Immobilization of pamidronic acids on the nanotube surface of titanium discs and their interaction with bone cells

Self-assembled layers of vertically aligned titanium nanotubes were fabricated on a Ti disc by anodization. Pamidronic acids (PDAs) were then immobilized on the nanotube surface to improve osseointegration. Wide-angle X-ray diffraction, X-ray photoelectron microscopy, and scanning electron microscopy were employed to characterize the structure and morphology of the PDA-immobilized TiO2 nanotubes. The in vitro behavior of osteoblast and osteoclast cells cultured on an unmodified and surface-modified Ti disc was examined in terms of cell adhesion, proliferation, and differentiation. Osteoblast adhesion, proliferation, and differentiation were improved substantially by the topography of the TiO2 nanotubes, producing an interlocked cell structure. PDA immobilized on the TiO2 nanotube surface suppressed the viability of the osteoclasts and reduced their bone resorption activity.

Effect of local vs. systemic bisphosphonate delivery on dental implant fixation in a model of osteonecrosis of the jaw

Locally applied bisphosphonates may improve the fixation of metal implants in bone. However, systemic bisphosphonate treatment is associated with a risk of osteonecrosis of the jaw (ONJ). We hypothesized that local delivery of bisphosphonate from the implant surface improves the fixation of dental implants without complications in a setting where systemic treatment induces ONJ. Forty rats were randomly allocated to 4 groups of 10. All groups received a titanium implant inserted in an extraction socket. Group I received the implants only. Group II received dexamethasone (0.5 mg/kg). Group III received dexamethasone as above plus alendronate (200 µg/kg). Group IV received zoledronate-coated implants and dexamethasone as above. The animals were sacrificed 2 weeks after tooth extraction. All 10 animals with systemic alendronate treatment developed large ONJ-like changes, while all with local treatment were completely healed. Implant removal torque was higher for the bisphosphonate-coated implants compared with the other groups (p < 0.03 for each comparison). Micro-computed tomography of the maxilla showed more bone loss in the systemic alendronate group compared with groups receiving local treatment (p = 0.001). Local bisphosphonate treatment appears to improve implant fixation in a setting where systemic treatment caused ONJ.

Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Bisphosphonates (BPs) are a group of well-established drugs that are applied in the development of metabolic bone disorder-related therapies. There is increasing interest also in the application of BPs in the context of bone tissue engineering, which is the topic of this review, in which an extensive overview of published studies on the development and applications of BPs-based strategies for bone regeneration is provided with special focus on the rationale for the use of different BPs in three-dimensional (3D) bone tissue scaffolds. The different alternatives that are investigated to address the delivery and sustained release of these therapeutic drugs in the nearby tissues are comprehensively discussed, and the most significant published approaches on bisphosphonate-conjugated drugs in multifunctional 3D scaffolds as well as the role of BPs within coatings for the improved fixation of orthopedic implants are presented and critically evaluated. Finally, the authors' views regarding the remaining challenges in the fields and directions for future research efforts are highlighted.

Locally enhanced early bone formation of zoledronic acid incorporated into a bone cement plug in vivo

OBJECTIVES

The aim of the study was to gain experience about the short-term effects of zoledronic acid (ZOL) on bone-implant contact (BIC), bone regeneration and bone area (BA).

METHODS

In this in-vivo study, ZOL was released locally from a drug-loaded pre-shaped calcium phosphate bone cement plug which was implanted into a bone defect in the proximal tibia of rats. At 1 and 3 weeks post implantation, tissue reactions as well as bone regeneration capabilities at the implant site were investigated. Furthermore, tissue samples, harvested at placebo and verum plug sites were used to analyse the gene expression of selected bone-specific markers by using quantitative polymerase chain reaction. Data were normalized against ribosomal RNA (Rn18s) subunits.

KEY FINDINGS

In the placebo interface a higher amount of cells could be detected as indicated by higher expression of small subunit Rn18s. Nevertheless, comparing the normalized data of the selected gene expression levels, no significant differences were detected. The histomorphometric results showed a significant higher BIC and BA for ZOL-loaded plugs at 3 weeks after implantation.

CONCLUSIONS

In this model, ZOL was demonstrated to be effective in impacting the bone regeneration process towards reduction of early bone resorption and enhanced bone formation.

EFFECT OF ALENDRONATE-CONTAINING COATINGS ON OSTEOINTEGRATION INTO POROUS TANTALUM IN A CORTICAL BONE MODEL

Hip replacement is extensively performed in hips with serious damages. The clinical outcomes of hip implants remain to be improved. Local delivery of bisphosphonates may improve implant fixation by positively affecting local bone modeling. In this study, two alendronate-containing coatings were prepared on porous tantalum by electrolytic deposition. Calcium phosphate coating was deposited and adsorbed with alendronate; the resulting coating had a low drug dose and slow release rate. Solid calcium alendronate coating was also deposited on tantalum; the resulting coating had high drug dose and faster release rate. The effects of the two coatings on new bone formation and implant fixation were studied in the rabbit tibial cortex. Four weeks after implantation, the implants with adsorbed alendronate showed the highest total new bone formation and mechanical fixation, whereas the implants with solid drug coating showed slightly lower fixation and total new bone formation than control bare implants. The improvement by the alendronate-adsorbed calcium phosphate coating provides potentials of enhancing early fixation of porous implants. The solid drug coating warranted further studies to exploit its high drug dose for inhibiting future osteolysis.

Local bisphosphonate release versus hydroxyapatite coating for stainless steel screw fixation in rat tibiae

Implant fixation in bone can be improved by a coating that delivers bisphosphonates locally, or by a hydroxyapatite (HA) coating. In this study, we compared these different types of coatings. For mechanical testing, 30 rats were assigned into three groups, and similar screws were implanted bilaterally in the proximal tibiae. The rats received screws that were either uncoated, coated with nano-crystalline hydroxyapatite or coated with a bisphosphonate releasing protein matrix. After 4 weeks, one screw was subjected to pull-out testing, and the contra-lateral one to torsion testing. For morphology, 30 rats were assigned to similar treatment groups, but received only one screw each. Bisphosphonates enhanced the pull-out force by 41% (P = 0.02) compared to controls, HA increased the pull-out force although not significantly. Conversely, HA increased the maximal torque by 64% (P = 0.02). Morphometry showed higher bone volume around bisphosphonate screws in comparison to HA-coated screws (P < 0.001) and controls (P < 0.001). The results suggest that bisphosphonates improve fixation by increasing the amount of surrounding bone, whereas HA mainly improves bone to implant attachment.

Augmentation of peri-implant bone improves implant stability: quantification using simulated bone loss

Low bone quality, such as induced by osteoporosis, is considered a main factor leading to failure of fracture fixations. Peri-implant bone augmentation has been proposed as a means of reducing failure rates in osteoporotic bone by improving implant stability. The beneficial effects of pharmacological augmentation of bone in the immediate vicinity of the implant have been demonstrated. Yet, a quantitative understanding of the role of peri-implant bone in implant stability is lacking. Therefore, the aim of our study was to quantify the effects of bone loss and peri-implant bone augmentation on implant stability using image-based finite element analyses. Using a validated model, we simulated how osteoporotic bone loss would affect implant stability in human humeral heads. We also quantified how augmentation of peri-implant bone can enhance implant stability. Our simulations revealed that a 30% reduction in bone mass led to a 50% decrease in implant stability. We also found that peri-implant bone augmentation increased implant stability and that the efficiency of bone augmentation decreased with increasing peri-implant distance. These findings highlight the strong effect that bone loss has on implant fixation and the potential of peri-implant bone augmentation for improving implant anchorage in low quality bone.

Effect of zoledronate acid treatment on osseointegration and fixation of implants in autologous iliac bone grafts in ovariectomized rabbits

One main problem associated with alveolar bone augmentation in implant dentistry is resorption of grafted bone, which may be further compromised by systemic skeletal disorders such as osteoporosis. Zoledronate acid (ZOL) is the most potent bisphosphonate to treat osteoporosis and therefore it is hypothesized to be able to invert the negative effect of osteoporosis on osseointegration and fixation of dental implants in autologous bone grafts. In this study, 56 rabbits received bilateral ovariectomy (OVX) (40 rabbits) or sham operation (16 rabbits). Three months later, 8 animals from each group were sacrificed for bone mineral density (BMD) examination. Then the remaining animals underwent bilateral autologous iliac bone grafting with simultaneous implantation of titanium implants in tibiae and were divided into 5 groups (n=8): Sham, OVX, Loc-ZOL (local treatment), Sys-ZOL (systemic treatment) and Loc+Sys-ZOL (local plus systemic) group. At 3 months after implantation, all animals were sacrificed and specimens were harvested for examinations. Both BMD and histological examinations of femurs showed osteoporotic changes after ovariectomy, while systemic treatment with ZOL restored mineralized bone. Micro-CT examination demonstrated that OVX group showed significant decrease of mineralized bone and implant-bone contact when compared with sham control, whereas both systemic and local treatments of ZOL significantly increased mineralized bone and implant-bone contact in ovariectomized animals. However, the best effects were observed in Loc+Sys-ZOL group (combined use of ZOL) and most of bone indices were similar to (IBCR, p>0.05) or higher than (BV/TV, Conn.D and Tb.N) (p<0.01) those of the sham group, except Tb.Th, which was still significantly lower (p<0.01), and Tb.Sp, which was further decreased (p<0.01). The aforementioned effects were also confirmed by histomorphometric analysis of bone indices on implant-bone contact and mineralized bone. In addition, biomechanical testing further supported the beneficial effect of ZOL treatment and maximal removal torque of titanium implants was observed in Loc+Sys-ZOL group. In conclusion, our study suggests that both systemic and local treatments with ZOL can invert negative effect of osteoporosis and promote osseointegration and fixation of dental implants in autologous bone grafts under osteoporotic condition. Combined systemic and local use of ZOL exerts best effects when compared to their single use.

Evaluation of trabecular bone formation in a canine model surrounding a dental implant fixture immobilized with an antimicrobial peptide derived from histatin

JH8194 induces osteoblast differentiation, although it was originally designed to improve antifungal activity. This suggests that JH8194 is useful for implant treatment. Therefore, the aim of this study was to evaluate the osseointegration capacity of JH8194-modified titanium dental implant fixtures (JH8194-Fi). The implants were randomly implanted into the edentulous ridge of dog mandibles. Healing abutments were inserted immediately after implant placement. Three weeks later, peri-implant bone levels, the first bone-to-implant contact points, and trabecular bone formation surrounding the implants were assessed by histological and digital image analyses based on microcomputed tomography (microCT). The histological analysis revealed an enhancement of mature trabecular bone around the JH8194-Fi compared with untreated fixtures (control-Fi). Similarly, microCT combined with analysis by Zed View™ also showed increased trabecular bone formation surrounding the JH8194-Fi compared with the control-Fi (Student's t-test, P < 0.05). JH8194 may offer an alternative biological modification of titanium surfaces to enhance trabecular bone formation around dental implants, which may contribute to the transient acquirement of osseointegration and the long-term success of implant therapy.

Effect of β-tricalcium phosphate coated with zoledronic acid on human osteoblasts and human osteoclasts in vitro

The combination of a bone graft material with bisphosphonates (BPs) might be advantageous for an optimal balance of material resorption and stimulation of bone formation. This study investigated the effect of β-tricalcium phosphate (β-TCP) bone grafts coated with zoledronic acid (ZOL) on osteoblast-like cells and osteoclast-like cells (OLC). As a drug carrier, the polymer poly(D,L-lactide) was used and three different concentrations of ZOL were tested. β-TCP coated with ZOL stimulated the production of osteocalcin (OC), osteoprotegerin, and sRANKL in osteoblast-like cells. The polymer coating alone caused a significant increase in collagen type 1 and OC production. OLC viability was inhibited and the tartrate-resistant acidic phosphatase isoform-5b was significantly decreased after cultivation on polymer-coated β-TCP for 12 days. The three different concentrations of ZOL decreased cell viability and no TRAPiso-5b was detectable, indicating a strong reduction of the TRAPiso-5b after 12 days in culture. After 21 days in culture, only the higher ZOL concentrations significantly reduced cell viability and TRAPiso-5b. The results of this study show that coating of β-TCP with ZOL has stimulating effects on osteoblast-like cells. Additionally, an inhibition of osteoclasts was seen. The combination of this bone grafting material with BPs might, therefore, be effective in the treatment of large bone defects.