Bone response to calcium phosphate-coated and bisphosphonate-immobilized titanium implants

Effects of the Application Local Zoledronic Acid On Different Dental Implants in Rats On Osseointegration

Objective

Recently, a lot of research has been done around the world to popularize the osseointegration of dental implants. In this study, it was investigated the effect of local zoledronic acid application on implants with machined (MAC), resorbable blast materials (RBM), sandblasted and acid-etched (SLA) surface implants integrated in rat tibias.

Methodology

A total of 60 female Wistar rats weighing between 270 and 300 g were used in the study. The rats were passing divided into six classes: controls; MAC (n = 10), RBM (n = 10), SLA (n = 10), and local zoledronic acid (LZA) applied groups; LZA-MAC (n = 10), LZA-RBM (n=10) and LZA-SLA (n = 10) and implants were surgically placement into rat tibias in general anesthesia. After a four-week experimental period, the biomechanical bone implant connection level was determined with reverse torque analysis.

Results

Osseointegration levels were detected highly in SLA and RBM surface compared with the machined surfaced implants in both control and treatment groups (p < 0.05). Additionally, local application of zoledronic acid in both three groups; implants increased the biomechanic osseointegration level compared with the controls (p < 0.05).

Conclusion

In this research, we observe that the local application of the zoledronic acid could increase the osseointegration, and RBM and SLA surface could be better than machined surfaced implants in terms of bone implant connection. In addition, local application of zoledronic acid may be a safer method than systemic application.

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

A The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and discontinued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.

Roles of osteoclasts in alveolar bone remodeling

Osteoclasts are large multinucleated cells from hematopoietic origin and are responsible for bone resorption. A balance between osteoclastic bone resorption and osteoblastic bone formation is critical to maintain bone homeostasis. The alveolar bone, also called the alveolar process, is the part of the jawbone that holds the teeth and supports oral functions. It differs from other skeletal bones in several aspects: its embryonic cellular origin, the form of ossification, and the presence of teeth and periodontal tissues; hence, understanding the unique characteristic of the alveolar bone remodeling is important to maintain oral homeostasis. Excessive osteoclastic bone resorption is one of the prominent features of bone diseases in the jaw such as periodontitis. Therefore, inhibiting osteoclast formation and bone resorptive process has been the target of therapeutic intervention. Understanding the mechanisms of osteoclastic bone resorption is critical for the effective treatment of bone diseases in the jaw. In this review, we discuss basic principles of alveolar bone remodeling with a specific focus on the osteoclastic bone resorptive process and its unique functions in the alveolar bone. Lastly, we provide perspectives on osteoclast-targeted therapies and regenerative approaches associated with bone diseases in the jaw.

Crystalline Biomimetic Calcium Phosphate Coating on Mini-Pin Implants to Accelerate Osseointegration and Extend Drug Release Duration for an Orthodontic Application

Miniscrew implants (MSIs) have been widely used as temporary anchorage devices in orthodontic clinics. However, one of their major limitations is the relatively high failure rate. We hypothesize that a biomimetic calcium phosphate (BioCaP) coating layer on mini-pin implants might be able to accelerate the osseointegration, and can be a carrier for biological agents. A novel mini-pin implant to mimic the MSIs was used. BioCaP (amorphous or crystalline) coatings with or without the presence of bovine serum albumin (BSA) were applied on such implants and inserted in the metaphyseal tibia in rats. The percentage of bone to implant contact (BIC) in histomorphometric analysis was used to evaluate the osteoconductivity of such implants from six different groups (n=6 rats per group): (1) no coating no BSA group, (2) no coating BSA adsorption group, (3) amorphous BioCaP coating group, (4) amorphous BioCaP coating-incorporated BSA group, (5) crystalline BioCaP coating group, and (6) crystalline BioCaP coating-incorporated BSA group. Samples were retrieved 3 days, 1 week, 2 weeks, and 4 weeks post-surgery. The results showed that the crystalline BioCaP coating served as a drug carrier with a sustained release profile. Furthermore, the significant increase in BIC occurred at week 1 in the crystalline coating group, but at week 2 or week 4 in other groups. These findings indicate that the crystalline BioCaP coating can be a promising surface modification to facilitate early osseointegration and increase the success rate of miniscrew implants in orthodontic clinics.

Electrodeposited Hydroxyapatite-Based Biocoatings: Recent Progress and Future Challenges

Hydroxyapatite has become an important coating material for bioimplants, following the introduction of synthetic HAp in the 1950s. The HAp coatings require controlled surface roughness/porosity, adequate corrosion resistance and need to show favorable tribological behavior. The deposition rate must be sufficiently fast and the coating technique needs to be applied at different scales on substrates having a diverse structure, composition, size, and shape. A detailed overview of dry and wet coating methods is given. The benefits of electrodeposition include controlled thickness and morphology, ability to coat a wide range of component size/shape and ease of industrial processing. Pulsed current and potential techniques have provided denser and more uniform coatings on different metallic materials/implants. The mechanism of HAp electrodeposition is considered and the effect of operational variables on deposit properties is highlighted. The most recent progress in the field is critically reviewed. Developments in mineral substituted and included particle, composite HAp coatings, including those reinforced by metallic, ceramic and polymeric particles; carbon nanotubes, modified graphenes, chitosan, and heparin, are considered in detail. Technical challenges which deserve further research are identified and a forward look in the field of the electrodeposited HAp coatings is taken.

Zn-HA/Bi-HA biphasic coatings on Titanium: Fabrication, characterization, antibacterial and biological activity

Hydroxyapatite (HA) coatings have been of important as biocompatible coatings for dental and bone tissue engineering application. However, the poor antibacterial performance and weak biological activity of HA coatings limited their clinical applications. As a strategy to improve the antibacterial performance and biological activity of HA, Zinc and bismuth ions were incorporated into HA lattice by substituting Ca²⁺ ions, respectively, and thus zinc substituted hydroxyapatite/bismuth substituted hydroxyapatite (Zn-HA/Bi-HA) biphasic coatings on titanium plates with various ratios were fabricated via sol-gel and dip-coating processes. The purity of the Zn-HA and Bi-HA phase was confirmed by X-ray diffraction (XRD) test. The biphasic coatings showed slower dissolution rate than pure HA coating. Furthermore, the Zn-HA/Bi-HA coatings reveal good biomineralization activity in simulated body fluid (SBF) by forming regular spherical apatite agglomerates. Moreover, the biphasic Zn-HA/Bi-HA coatings exhibited that improved antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as compared to pure HA coatings. The CCK-8 assays demonstrate Zn-HA/Bi-HA coatings showed no toxicity to MG63 cells, and the Zn-HA/Bi-HA2 (Zn-HA:Bi-HA=64:1) coating is more effective to enhance the proliferation of MG63 cells compared to other coatings. This finding suggests Zn-HA/Bi-HA biphasic coatings are promising candidates for biomedical applications.

Bioinspired surface modification of orthopedic implants for bone tissue engineering

Biomedical implants have been widely used in various orthopedic treatments, including total hip arthroplasty, joint arthrodesis, fracture fixation, non-union, dental repair, etc. The modern research and development of orthopedic implants have gradually shifted from traditional mechanical support to a bioactive graft in order to endow them with better osteoinduction and osteoconduction. Inspired by structural and mechanical properties of natural bone, this review provides a panorama of current biological surface modifications for facilitating the interaction between medical implants and bone tissue and gives a future outlook for fabricating the next-generation multifunctional and smart implants by systematically biomimicking the physiological processes involved in formation and functioning of bones.

The effect of zoledronic acid on middle ear osteoporosis: An animal study

Hearing function in older patients may be related to bone structure. We conducted an experiment to evaluate the effect of zoledronic acid on osteoporotic middle ear ossicles in an animal model. Our subjects were 19 female New Zealand white rabbits (38 ears) weighing 2 to 4 kg. We divided the rabbits into three groups: one group consisted of 6 rabbits with osteoporotic ears that were treated with zoledronic acid; the second group was made up of 8 rabbits with osteoporotic ears that were not treated; a control group included 5 rabbits with normal ears that were untreated. After an oophorectomy, the 6 study rabbits were administered 0.1 ml/kg of zoledronic acid intravenously. All rabbits were sacrificed 16 weeks later, and the middle ear ossicles were removed for investigation under light microscopy. Although osteoporosis enhanced the osteoclastic bone resorption of the ossicles, zoledronic acid enhanced osteoblastic activity on osteoporotic middle ear ossicles. The incidence of osteoporosis was 93.8% in the untreated osteoporosis group and 33.3% in zoledronic acid group-a statistically significant difference (OR: 0.24; 95% CI: 0.09 to 0.58; p < 0.001). Osteoporosis appears to increase the resorption of the middle ear ossicles, a process that can be avoided with zoledronic acid administration. Prevention of the effects of osteoporosis in humans may help decrease the irreversible changes in the middle ear ossicles.

Effects of polycaprolactone on alendronate drug release from Mg-doped hydroxyapatite coating on titanium

The scientific objective of this study was to understand the influence of PCL coating on alendronate drug release kinetics in vitro. Our hypothesis was PCL coating would minimize burst release of alendronate from plasma sprayed Mg-doped hydroxyapatite (HA) coated commercially pure titanium (CpTi) samples. In the US alone, over 44 million women and men aged 50 and older are affected by osteoporosis which can lead to replacement and/or revision surgeries. Alendronate is a widely-used drug for treating osteoporosis and would be an ideal drug to be loaded and released from these replacement systems. Initial burst release is a common phenomenon for the most drug loaded devices. To modulate the release kinetics, a biodegradable polymer, polycaprolactone (PCL), coating with slow degradable kinetics was employed. Samples with 2 and 4 wt% PCL showed about 34% and 26% release of alendronate within the first 24 h, respectively, compared to 75% burst release without any PCL coating. With the addition of a PCL coating, a controlled release kinetics of alendronate was achieved from HA coated titanium implants, which can potentially impact millions of patients worldwide having compromised bone due to osteoporosis.

The effect of osteoprotegerin on implant osseointegration in ovariectomized rats

INTRODUCTION

Osteoprotegerin (OPG), the endogenous inhibitor of RANKL, prevents or reverses bone loss in a variety of preclinical models of bone disease. Preclinical studies indicate that osteoporosis significantly impairs implant fixation. This study aims to investigate the role of OPG in implant osseointegration in ovariectomized rats.

MATERIAL AND METHODS

Twelve weeks after bilateral ovariectomy, each rat accepted two titanium screws in the proximal tibiae. All animals were then randomly divided into two groups: the control (10 rats) and OPG group (10 rats). Subcutaneous injection of OPG (10 mg/kg) or vehicle was performed three times a week. Eight weeks later, tibiae with screws were harvested for micro-computed tomography (μCT), histological and biomechanical analysis.

RESULTS

Compared to control, OPG increased the percent bone volume by 124%, the percent osseointegration by 167%, the mean trabecular number by 111%, the mean trabecular thickness by 92% (p < 0.01), the mean connective density by 95% (p < 0.05); and decreased the mean trabecular separation by 64% in μCT analysis (p < 0.05). Osteoprotegerin also increased bone area density by 160% and bone-to-implant contact by 234% in histomorphometric evaluation (p < 0.01), and increased the maximal push-out force by 228% in biomechanical test (p < 0.01).

CONCLUSIONS

Systemic administration of OPG improved implant osseointegration and fixation in ovariectomized rats, resulting from the increased peri-implant bone mass and improved trabecular microarchitecture.

Role of Pyridoxal 5'-Phosphate at the Titanium Implant Interface In Vivo: Increased Hemophilicity, Inactive Platelet Adhesion, and Osteointegration

Titanium is the most biocompatible inorganic biomaterial with a long history of use in orthopedic and dental implants. However, promoting rapid and effective bone formation and integration onto etched, rough TiO₂ surfaces has been a challenging topic. Here, 21 commercially available molecules are examined that met the following criteria: (1) contain phosphonic acid for stable immobilization onto TiO₂ surfaces and (2) have a molecular weight less than 500 Da for negligible coating thickness. Of these molecules, the surface immobilization of pyridoxal 5'-phosphate (PLP), an active form of vitamin B₆ , dramatically increases the hemophilic property of the surface and accelerated osteointegration in vivo. Analysis shows that PLP promotes surface binding of serum albumin and other plasma proteins by Schiff-base formations via its aldehyde group, providing a platform suitable for osteoblast adhesion. PLP also retards blood coagulation more than the widely used citric acid at the TiO₂ surface. As PLP is capable of maintaining an inactivated status of surface-adsorbed platelets, delayed coagulation at the implant-blood interface allows for sufficient supply of growth factors from blood plasma and migration of osteoblasts. The results suggest that PLP can be widely applicable as a biocompatible, effective coating compound to promote osteointegration of titanium-based implants.

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.

Randomised trial of bisphosphonate-coated dental implants: Radiographic follow-up after five years of loading

The results of a randomised trial with bisphosphonate-coated dental implants have been reported previously. Each patient received one coated and one uncoated implant in a double-blind split-mouth design study. After 6 months of osseointegration, resonance frequency analysis indicated better fixation of the coated implants. Reduced marginal bone resorption was also shown. However, it was not known whether the advantage of the bisphosphonate coating would persist over time. The radiographic results at 5 years after implant installation are reported herein. A blinded investigator measured marginal resorption on fresh radiographs obtained for 14 of the 16 patients (two had died) and compared these with the post-implantation images. Non-parametric statistics were used. All implants functioned well. The median marginal bone loss for control implants was found to be 0.70mm, which is less than usually reported in the literature. The bisphosphonate-coated implants showed even less resorption (median 0.20mm). The median difference within each pair of implants after 5 years of use was 0.34mm (95% confidence interval 0.00-0.75mm; P=0.04). The present data suggest that bisphosphonate-coated implants enable prolonged preservation of the marginal bone.

Efficacy of the comprehensive antiresorptive therapy at different stages of surgical rehabilitation in dentition defects in female patients with postmenopausal osteoporosis

Question of the interrelationship of systemic disorders of bone remodeling and the condition of the bone tissue of the alveolar bone, as well as the efficiency of comprehensive antiresorptive therapy at different stages of surgical rehabilitation in dentition defects in female patients with postmenopausal osteoporosis (PMOP) requires further clarification and remains a subject of active discussion of scientists and clinicians. In the study there was demonstrated that in PMOP female patients with atrophy of the alveolar process of the maxilla in edentulous area there is noted was a significant excess in indices of bone turnover (TNF-alpha level - by 184%, IL-1 - 224%, IL-6- 85%, CTx -156% osteocalcin - 32.9%, PTH- 55%) against the background of the reduced level of a D(OH)25 (by 25.8%) in comparison with patients of reproductive age without osteoporosis. These data correlate with a significant increase in indices of osteosynthesis (index level of the osteoid volume - by 17.6%, index of total resorptive surface by - 51.5%) and a decrease in bone quality indices (index level of the total volume of trabecules - by 60%, index of average width of trabeculae - by 40 %) according to results of the histological examination of bioptate of the process from the edentulous area. At that in PMOP patients with concomitant accompanying somatic pathology the level of TNF-a, IL-1, IL-6 and CTx was significantly higher than in patients of this the group without comorbidity. Appointment of the comprehensive antiresorptive therapy at all stages of surgical rehabilitation (open sinus lifting, dental implantation) in PMOP patients with atrophy of the maxilla in edentulous area during the year before and after sinus lifting significantly increasedthe efficiency of the dental implant. Supplementation of NSAIDs (Arcoxia 60 mg per day) for 2 months prior to dental implantation and within 1 month after a comprehensive antiresorptive therapy in PMOP patients with concomitant estrogen-induced pathology also significantly increases the efficiency of the dental implant in comparison with given indices in patients which received no combined therapy.

Implant-delivered Alendronate Causes a Dose-dependent Response on Net Bone Formation Around Porous Titanium Implants in Canines

BACKGROUND

Bony fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving porous implant fixation could improve the reliability and durability of these reconstructive procedures.

QUESTIONS/PURPOSES

In this study, we asked whether there is a positive and dose-dependent effect of the local release of the bisphosphonate alendronate from (1) alendronate/hydroxyapatite (HA) porous-coated titanium implants compared with bare metal porous controls; and (2) alendronate/HA on porous-coated titanium implants compared with HA-coated porous controls with respect to extent of bone ingrowth, bone apposition, and periimplant bone formation in a canine model?

METHODS

Three-dimensional printed porous-coated cylindrical implants coated with three different doses (0.02, 0.06, and 0.18 mg/cm(2)) of alendronate were inserted bilaterally in the intramedullary canal of the proximal femora of 15 adult mongrel dogs (age range, 3-9 years; mean, 5 years) weighing between 36 kg and 60 kg (mean, 43 kg). In each dog, an implant coated with HA and one of three different doses of alendronate was inserted on one side while the contralateral femur had a bare metal porous control implant and an identical control implant with a coating of HA. The dose effect of locally released alendronate on the extent of bone ingrowth, bone apposition, and periimplant bone was assessed by backscattered electron microscopy of three pairs of cross-sections taken from each implant at 12 weeks after surgery. A linear mixed model was used to perform the statistical analyses to account for the correlation in the data resulting from the multiple measures performed on each dog.

RESULTS

Compared with paired bare metal controls, periimplant bone increased by 92% (p = 0.007), and 114% (p < 0.001) in the femora with the alendronate implants with a dose of 0.06 mg/cm(2), or 0.18 mg/cm(2), respectively. At a dose of 0.02 mg/cm(2), there was no difference (46% change; p = 0.184, with the numbers available). The comparison of the alendronate-dosed implants with their HA-coated controls showed that the intermediate dose of 0.06 mg/cm(2) alendronate had the greatest effect on net bone formation. Bone apposition was enhanced with the 0.06-mg/cm(2) alendronate femoral implants (82%; p = 0.008), although there was no change in bone ingrowth (37% change; p = 0.902, with the numbers available). When compared with the HA-coated control implants, the greatest effect of the alendronate-dosed implants was the increased amount of periimplant bone at the intermediate dose of 0.06-mg/cm(2) (108%, p = 0.009). There was no effect of the low (0.02-mg/cm(2)) and high (0.18-mg/cm(2)) alendronate-dosed implants (4%, and 6%, respectively; p = 0.321, p = 0.502). Overall, all three alendronate-dosed implants revealed little to no effect on bone ingrowth compared with the HA-coated control implants.

CONCLUSIONS

The local release of alendronate from a three-dimensional printed porous-coated implant from the three doses studied showed an overall improvement in bone apposition and periimplant bone at the intermediate dose compared with bare metal or with HA-coated controls, although the effect was more pronounced compared with bare metal. Long-term studies to show the effects of localized alendronate delivery and mechanical fixation would be the next step for future studies.

CLINICAL RELEVANCE

Local release of alendronate from a three-dimensional printed porous-coated implant may improve the reliability of cementless fixation of currently available porous-coated bare metal implants.

Bisphosphonate-related osteonecrosis of the jaw and dental implants

Bisphosphonate (BP) is one of the possible riskfactors in the osteonecrosis of the jaw (ON J). Surgical interventions during or after the course of treatment by using BPs may expose the patient under this risk. Animal studies, human studies, case reports, and systematic reviews are used to show the relationship between the use of bisphosphonates and dental implants. In this review data about bisphosphonaterelated osteonecrosis of the jaw (BRON J): incidence, prevention and treatment modalities for the patients who are scheduled for dental implant treatment plan and who have been already treated by dental implants will be investigated. Various views for the relationship between dental implants and bisphosphonates will be analyzed depending on the multifactors: duration, route of uptake, dosage of the drug and patient's other medications that affect the effects of bisphosphonate. All patients treated with this drug must be informed about the risk of implant loss or possibility of osteonecrosis.

In vitro and in vivo investigation of bisphosphonate-loaded hydroxyapatite particles for peri-implant bone augmentation

Locally applied bisphosphonates, such as zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite (HA) particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-zoledronate combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either zoledronate-loaded or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that had been predrilled in rat femoral condyles before the insertion of miniature screws. Micro-CT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound zoledronate. Hyaluronic acid with zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation. Copyright © 2015 John Wiley & Sons, Ltd.

Atmospheric pressure nonthermal plasmas for bacterial biofilm prevention and eradication

Biofilms are three-dimensional structures formed by surface-attached microorganisms and their extracellular products. Biofilms formed by pathogenic microorganisms play an important role in human diseases. Higher resistance to antimicrobial agents and changes in microbial physiology make treating biofilm infections very complex. Atmospheric pressure nonthermal plasmas (NTPs) are a novel and powerful tool for antimicrobial treatment. The microbicidal activity of NTPs has an unspecific character due to the synergetic actions of bioactive components of the plasma torch, including charged particles, reactive species, and UV radiation. This review focuses on specific traits of biofilms, their role in human diseases, and those effects of NTP that are helpful for treating biofilm infections. The authors discuss NTP-based strategies for biofilm control, such as surface modifications to prevent bacterial adhesion, killing bacteria in biofilms, and biofilm destruction with NTPs. The unspecific character of microbicidal activity, proven polymer modification and destruction abilities, low toxicity for human tissues and absence of long-living toxic compounds make NTPs a very promising tool for biofilm prevention and control.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

Since various interactions among cells, surrounding tissues and implanted biomaterials always occur at their interfaces, the surface properties of potential implants appear to be of paramount importance for the clinical success. In view of the fact that a limited amount of materials appear to be tolerated by living organisms, a special discipline called surface engineering was developed to initiate the desirable changes to the exterior properties of various materials but still maintaining their useful bulk performances. In 1975, this approach resulted in the introduction of a special class of artificial bone grafts, composed of various mechanically stable (consequently, suitable for load bearing applications) implantable biomaterials and/or bio-devices covered by calcium orthophosphates (CaPO4) to both improve biocompatibility and provide an adequate bonding to the adjacent bones. Over 5000 publications on this topic were published since then. Therefore, a thorough analysis of the available literature has been performed and about 50 (this number is doubled, if all possible modifications are counted) deposition techniques of CaPO4 have been revealed, systematized and described. These CaPO4 deposits (coatings, films and layers) used to improve the surface properties of various types of artificial implants are the topic of this review.

Synthesis, characterization and the formation mechanism of magnesium- and strontium-substituted hydroxyapatite

The hydroxyapatite crystals grow in different ways when the calcium is substituted by strontium or magnesium.

Bisphosphonate associated osteonecrosis of the jaw: an update on pathophysiology, risk factors, and treatment

Osteonecrosis of the jaw in patients treated with bisphosphonates is a relatively rare but well known complication at maxillofacial units around the world. It has been speculated that the medication, especially long-term i.v. bisphosphonate treatment, could cause sterile necrosis of the jaws. The aim of this narrative review of the literature was to elaborate on the pathological mechanisms behind the condition and also to gather an update on incidence, risk factors, and treatment of bisphosphonate associated osteonecrosis of the jaw. In total, ninety-one articles were reviewed. All were published in internationally recognized journals with referee systems. We can conclude that necrotic lesions in the jaw seem to be following upon exposure of bone, for example, after tooth extractions, while other interventions like implant placement do not increase the risk of osteonecrosis. Since exposure to the bacterial environment in the oral cavity seems essential for the development of necrotic lesions, we believe that the condition is in fact chronic osteomyelitis and should be treated accordingly.

Fabrication of porous titanium scaffolds by stack sintering of microporous titanium spheres produced with centrifugal granulation technology

Microporosity plays a key role in bioactivity and osteoinductivity of a biomaterial scaffold. A simple new approach to fabricating load-bearing porous titanium (Ti) scaffolds with uniform porous structure, highly controllable pore size and excellent biocompatibility was developed in the present study. This method was based on stack sintering of microporous Ti spheres produced with centrifugal granulation of commercial Ti powders. Macropores (180.0-341.8 μm) and micropores (6.1-11.8 μm) of the scaffolds were dependent on the sizes of the Ti spheres and the Ti powders, respectively. The compressive strength of the scaffolds (83.4-108.9 MPa) was high enough for the repair of load-bearing bone defects. Besides, the abundant micropores occurred on the rough and convex surface of the Ti spheres in the scaffolds were more favorable for adsorption of serum proteins, and thus promoted the growth of mesenchymal stem cells (MSCs).

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.

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.

Early tissue responses to zoledronate, locally delivered by bone screw, into a compromised cancellous bone site: a pilot study

Background

In fracture treatment, adequate fixation of implants is crucial to long-term clinical performance. Bisphosphonates (BP), potent inhibitors of osteoclastic bone resorption, are known to increase peri-implant bone mass and accelerate primary fixation. However, adverse effects are associated with systemic use of BPs. Thus, Zoledronic acid (ZOL) a potent BP was loaded on bone screws and evaluated in a local delivery model. Whilst mid- to long-term effects are already reported, early cellular events occurring at the implant/bone interface are not well described. The present study investigated early tissue responses to ZOL locally delivered, by bone screw, into a compromised cancellous bone site.

Methods

ZOL was immobilized on fibrinogen coated titanium screws. Using a bilateral approach, ZOL loaded test and non-loaded control screws were implanted into femoral condyle bone defects, created by an overdrilling technique. Histological analyses of the local tissue effects such as new bone formation and osteointegration were performed at days 1, 5 and 10.

Results

Histological evaluation of the five day ZOL group, demonstrated a higher osseous differentiation trend. At ten days an early influx of mesenchymal and osteoprogenitor cells was seen and a higher level of cellular proliferation and differentiation (p < 5%). In the ZOL group bone-to-screw contact and bone volume values within the defect tended to increase. Local drug release did not induce any adverse cellular effects.

Conclusion

This study indicates that local ZOL delivery into a compromised cancellous bone site actively supports peri-implant osteogenesis, positively affecting mesenchymal cells, at earlier time points than previously reported in the literature.

Local alendronic acid elution increases net periimplant bone formation: a micro-CT analysis

BACKGROUND

Fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving implant fixation would improve the reliability and durability of certain reconstructive procedures.

QUESTIONS/PURPOSES

The purpose of this study was to determine the effect of local elution of the bisphosphonate alendronic acid on bone formation around porous titanium implants in an animal model.

METHODS

Porous-coated cylindrical rods were coated with either 0.2 mg or 1.0 mg alendronic acid before bilateral surgical implantation into the femoral intramedullary canals of 10 experimental dogs. Twelve weeks after surgery, the femora were harvested and scanned with micro-CT to quantify the percentage volume of bone within the immediate periimplant space. Four femora from two dogs were also processed for undecalcified thin-section histology and analysis with backscattered scanning electron microscopy. Three histologic sections from each of these four femora were anatomically matched with transverse micro-CT sections to enable direct comparison of the area fraction of bone within the periimplant space.

RESULTS

Compared with paired controls, micro-CT analysis showed that local elution of alendronic acid increased periimplant bone at both doses of 0.2 mg (+52%, p = 0.01) and 1.0 mg (+152%, p = 0.004) with 1.0 mg resulting in a 2.9-fold greater mean relative increase compared with 0.2 mg (p = 0.002). Micro-CT measurements of periimplant bone formation correlated very strongly with the backscattered scanning electron microscopy measurements (R = 0.965, p < 0.001).

CONCLUSIONS

Local elution of alendronic acid causes a dose-dependent net increase in periimplant bone formation in an animal model.

CLINICAL RELEVANCE

This concept has potential to improve the biologic fixation of porous reconstructive implants.

In-vitro biocompatibility and corrosion resistance of strontium incorporated TiO2 nanotube arrays for orthopaedic applications

This article investigates the in-vitro biocompatibility and corrosion behaviour of strontium ion incorporated TiO2 nanotube arrays formed by anodization method for orthopaedic applications. The morphological studies were carried out using field emission scanning electron microscopy, atomic force microscopy, attenuated total reflectance fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thin film X-ray diffraction techniques. The morphological investigation indicated that the length and the average diameter of nanotube were 2.1 ± 0.3 µm and 110 ± 4 nm, respectively. The wettability measurements showed that the TiO2 nanotube arrays have super wettability, as well as, strontium ion incorporated TiO2 nanotube arrays exhibited hydrophilic behaviour. Excellent in-vitro bioactivity was observed for TiO2 nanotube arrays with strontium ions. Electrochemical studies in Hank's solution showed that the TiO2 nanotube arrays with strontium ions have enhanced corrosion resistance.

SiO2 and ZnO dopants in three-dimensionally printed tricalcium phosphate bone tissue engineering scaffolds enhance osteogenesis and angiogenesis in vivo

Calcium phosphate (CaP) scaffolds with three-dimensionally-interconnected pores play an important role in mechanical interlocking and biological fixation in bone implant applications. CaPs alone, however, are only osteoconductive (able to guide bone growth). Much attention has been given to the incorporation of biologics and pharmacologics to add osteoinductive (able to cause new bone growth) properties to CaP materials. Because biologics and pharmacologics are generally delicate compounds and also subject to increased regulatory scrutiny, there is a need to investigate alternative methods to introduce osteoinductivity to CaP materials. In this study silica (SiO2) and zinc oxide (ZnO) have been incorporated into three-dimensional printed β-tricalcium phosphate (β-TCP) scaffolds to investigate their potential to trigger osteoinduction in vivo. Silicon and zinc are trace elements that are common in bone and have also been shown to have many beneficial properties, from increased bone regeneration to angiogenesis. Implants were placed in bicortical femur defects introduced to a murine model for up to 16 weeks. The addition of dopants into TCP increased the capacity for new early bone formation by modulating collagen I production and osteocalcin production. Neovascularization was found to be up to three times more than the pure TCP control group. The findings from this study indicate that the combination of SiO2 and ZnO dopants in TCP may be a viable alternative to introducing osteoinductive properties to CaPs.

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.

Raloxifene and alendronate containing thin mesoporous titanium oxide films improve implant fixation to bone

This study tested the hypothesis that osteoporosis drug-loaded mesoporous TiO2 implant coatings can be used to improve bone-implant integration. Two osteoporosis drugs, Alendronate (ALN) and Raloxifene (RLX), were immobilized in nanoporous oxide films prepared on Ti screws and evaluated in vivo in rat tibia. The drug release kinetics were monitored in vitro by quartz crystal microbalance with dissipation and showed sustained release of both drugs. The osteogenic response after 28days of implantation was evaluated by quantitative polymerase chain reaction (qPCR), removal torque, histomorphometry and ultrastructural interface analysis. The drug-loaded implants showed significantly improved bone fixation. In the case of RLX, stronger bone-remodelling activity was observed compared with controls and ALN-loaded implants. The ultrastructural interface analysis revealed enhanced apatite formation inside the RLX coating and increased bone density outside the ALN coating. Thus, this novel combination of a thin mesoporous TiO2 carrier matrix and appropriate drugs can be used to accelerate implant fixation in trabecular bone.

Calcium orthophosphates in dentistry

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in the most communities even though the prevalence of disease has decreased since the introduction of fluorides for dental care. Therefore, biomaterials to fill dental defects appear to be necessary to fulfill customers' needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns or bridges. Calcium orthophosphates belong to bioceramics but they have some specific advantages over other types of bioceramics due to a chemical similarity to the inorganic part of both human and mammalian bones and teeth. Therefore, calcium orthophosphates (both alone and as components of various formulations) are used in dentistry as both dental fillers and implantable scaffolds. This review provides brief information on calcium orthophosphates and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, calcium orthophosphates are most frequently used in periodontics; however, the majority of the publications on calcium orthophosphates in dentistry are devoted to unspecified "dental" fields.

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.

Calcium orthophosphate coatings, films and layers

In surgical disciplines, where bones have to be repaired, augmented or improved, bone substitutes are essential. Therefore, an interest has dramatically increased in application of synthetic bone grafts. As various interactions among cells, surrounding tissues and implanted biomaterials always occur at the interfaces, the surface properties of the implants are of the paramount importance in determining both the biological response to implants and the material response to the physiological conditions. Hence, a surface engineering is aimed to modify both the biomaterials, themselves, and biological responses through introducing desirable changes to the surface properties of the implants but still maintaining their bulk mechanical properties. To fulfill these requirements, a special class of artificial bone grafts has been introduced in 1976. It is composed of various mechanically stable (therefore, suitable for load bearing applications) biomaterials and/or bio-devices with calcium orthophosphate coatings, films and layers on their surfaces to both improve interactions with the surrounding tissues and provide an adequate bonding to bones. Many production techniques of calcium orthophosphate coatings, films and layers have been already invented and new promising techniques are continuously investigated. These specialized coatings, films and layers used to improve the surface properties of various types of artificial implants are the topic of this review.

Antibacterial and biological characteristics of silver containing and strontium doped plasma sprayed hydroxyapatite coatings

Infection in primary total joint prostheses is estimated to occur in up to 3% of all surgery. As a measure to improve the antimicrobial properties of implant materials silver (Ag) was incorporated into plasma sprayed hydroxyapatite (HA) coatings. To offset potential cytotoxic effects of Ag in the coatings strontium (Sr) was also added as a binary dopant. HA powder was doped with 2.0 wt.% Ag(2)O, 1.0 wt.% SrO and was then heat treated at 800 °C. Titanium substrates were coated using a 30 kW plasma spray system equipped with a supersonic nozzle. X-ray diffraction confirmed the phase purity and high crystallinity of the coatings. Samples were evaluated for mechanical stability by adhesive bond strength testing. The results show that the addition of dopants did not affect the overall bond strength of the coatings. The antibacterial efficacies of the coatings were tested against Pseudomonas aeruginosa. Samples that contained the Ag(2)O dopant were found to be highly effective against bacterial colonization. In vitro cell-material interactions using human fetal osteoblast cells were characterized by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for cell viability, field emission scanning electron microscopy for cell morphology and confocal imaging for the important differentiation marker alkaline phosphatase (ALP). Our results showed evidence of cytotoxic effects of the Ag-HA coatings, characterized by poor cellular morphology and cell death and nearly complete loss of functional ALP activity. The addition of SrO to the Ag-HA coatings was able to effectively offset these negative effects and improve performance compared with pure HA-coated samples.