Effect of modifications of dual acid-etched implant surfaces on peri-implant bone formation. Part I: organic coatings

Effects of Surface Treatment Method Forming New Nano/Micro Hierarchical Structures on Attachment and Proliferation of Osteoblast-like Cells

Titanium (Ti) and Ti-based alloys are commonly used in dental implants, and surface modifications of dental implants are important for achieving osseointegration (i.e., direct connection between the implant surface and bone). This study investigated the effect of an eco-friendly etching solution-a hydrogen peroxide-sodium bicarbonate mixture-on the surface properties and contact angles of osteoblast adhesion and proliferation on Ti surfaces. Disk-shaped Ti specimens were prepared using different surface treatments (machining, sandblasting, and sandblasting/acid-etching), and they were immersed in the etching solution and ultrasonically cleaned. Surface characterization was performed using scanning electron microscopy, digital microscopy, contact angle analysis, and X-ray photoelectron spectroscopy. MG-63 osteoblasts were cultured on the specimens, and their adhesion to the specimen surface and proliferation were examined using staining and the MTT assay, respectively. Additional etching with the etching solution caused the formation of nano/micro hierarchical structures, increased surface roughness, and enhanced hydrophilicity. Osteoblast adhesion and proliferation were found to improve on the modified surfaces. The eco-friendly etching method has the potential to enhance the biological properties of Ti implant surfaces and thereby improve dental implant performance.

Role of BMP-7 on biological parameters osseointegration of dental implants: Preliminary results of a preclinical study

The aim of this work was to analyze and compare the effect of bone morphogenetic protein-7 on biological parameters related to implant osseointegration in an experimental animal model. Sixteen dental implants were placed in the tibias of four randomly selected minipigs for the following dental implant surface treatments: Group A: conventional treatment of the dental implant surface by SLA (n = 8) and Group B: treatment of the dental implant surface with carboxyethylphosphonic acid and bone morphogenetic protein-7 (n = 8). The animals were sacrificed one month after dental implants placement and a histomorphometric study was performed for the evaluation of bone-to-implant contact, corrected bone-to-implant contact, new bone formation, interthread bone density and peri-implant density using Student's t-test and the non-parametric Mann-Whitney test. The histomorphometric parameters bone-to-implant contact and corrected bone-to-implant contact showed statistically significant differences between the study groups; 34.00% ± 9.92% and 50.02% ± 10.94%, respectively (p = 0.004) for SLA and 43.08% ± 10.76% and 63.30% ± 11.30%, respectively (p = 0.003) for BMP-7. The parameters new bone formation, interthread bone density and peri-implant density did not show statistically significant differences between the study groups (p = 0.951, p = 0.967 and p = 0.894, respectively). Dental implant surfaces treated with carboxyethylphosphonic acid and BMP-7 improve the biological response of dental implants to osseointegration.

Effects of Different Titanium Surface Treatments on Adhesion, Proliferation and Differentiation of Bone Cells: An In Vitro Study

The objective of this study was to evaluate the impacts of different sandblasting procedures in acid etching of Ti6Al4V surfaces on osteoblast cell behavior, regarding various physicochemical and topographical parameters. Furthermore, differences in osteoblast cell behavior between cpTi and Ti6Al4V SA surfaces were evaluated. Sandblasting and subsequent acid etching of cpTi and Ti6Al4V discs was performed with Al2O3 grains of different sizes and with varying blasting pressures. The micro- and nano-roughness of the experimental SA surfaces were analyzed via confocal, atomic force and scanning electron microscopy. Surface free energy and friction coefficients were determined. hFOB 1.19 cells were seeded to evaluate adhesion, proliferation and osteoblastic differentiation for up to 12 d via crystal violet assays, MTT assays, ALP activity assays and Alizarin Red staining assays. Differences in blasting procedures had significant impacts on surface macro- and micro-topography. The crystal violet assay revealed a significant inverse relationship between blasting grain size and hFOB cell growth after 7 days. This trend was also visible in the Alizarin Red assays staining after 12 d: there was significantly higher biomineralization visible in the group that was sandblasted with smaller grains (F180) when compared to standard-grain-size groups (F70). SA samples treated with reduced blasting pressure exhibited lower hFOB adhesion and growth capabilities at initial (2 h) and later time points for up to 7 days, when compared to the standard SA surface, even though micro-roughness and other relevant surface parameters were similar. Overall, etched-only surfaces consistently exhibited equivalent or higher adhesion, proliferation and differentiation capabilities when compared to all other sandblasted and etched surfaces. No differences were found between cpTi and Ti6Al4V SA surfaces. Subtle modifications in the blasting protocol for Ti6Al4V SA surfaces significantly affect the proliferative and differentiation behavior of human osteoblasts. Surface roughness parameters are not sufficient to predict osteoblast behavior on etched Ti6Al4V surfaces.

Collagen-Based Osteogenic Nanocoating of Microrough Titanium Surfaces

The aim of the present study was to develop a collagen/heparin-based multilayer coating on titanium surfaces for retarded release of recombinant human bone morphogenic protein 2 (rhBMP2) to enhance the osteogenic activity of implant surfaces. Polyelectrolyte multilayer (PEM) coatings were constructed on sandblasted/acid-etched surfaces of titanium discs using heparin and collagen. PEM films of ten double layers were produced and overlayed with 200 µL of a rhBMP2 solution containing 15 µg rhBMP2. Subsequently, cross-linking of heparin molecules was performed using EDC/NHS chemistry to immobilize the incorporated rhBMP2. Release characteristics for 3 weeks, induction of Alkaline Phosphatase (ALP) in C2C12 cells and proliferation of human mesenchymal stem cells (hMSCs) were evaluated to analyze the osteogenic capacity of the surface. The coating incorporated 10.5 µg rhBMP2 on average per disc and did not change the surface morphology. The release profile showed a delivery of 14.5% of the incorporated growth factor during the first 24 h with a decline towards the end of the observation period with a total release of 31.3%. Cross-linking reduced the release with an almost complete suppression at 100% cross-linking. Alkaline Phosphatase was significantly increased on day 1 and day 21, indicating that the growth factor bound in the coating remains active and available after 3 weeks. Proliferation of hMSCs was significantly enhanced by the non-cross-linked PEM coating. Nanocoating using collagen/heparin-based PEMs can incorporate clinically relevant amounts of rhBMP2 on titanium surfaces with a retarded release and a sustained enhancement of osteogenic activity without changing the surface morphology.

A systematic review on the effect of inorganic surface coatings in large animal models and meta-analysis on tricalcium phosphate and hydroxyapatite on periimplant bone formation

The aim of the present systematic review was to analyse studies using inorganic implant coatings and, in a meta‐analysis, the effect of specifically tricalcium phosphate (TCP) and hydroxyapatite (HA) implant surface coatings on bone formation according to the PRISMA criteria. Inclusion criteria were the comparison to rough surfaced titanium implants in large animal studies at different time points of healing. Forty studies met the inclusion criteria for the systematic review. Fifteen of these analyzed the bone‐to‐implant contact (BIC) around the most investigated inorganic titanium implant coatings, namely TCP and HA, and were included in the meta‐analysis. The results of the TCP group show after 14 days a BIC being 3.48% points lower compared with the reference surface. This difference in BIC decreases to 0.85% points after 21–28 days. After 42–84 days, the difference in BIC of 13.79% points is in favor of the TCP‐coatings. However, the results are not statistically significant, in part due to the fact that the variability between the studies increased over time. The results of the HA group show a significant difference in mean BIC of 6.94% points after 14 days in favor of the reference surface. After 21–28 days and 42–84 days the difference in BIC is slightly in favor of the test group with 1.53% points and 1.57% points, respectively, lacking significance. In large animals, there does not seem to be much effect of TCP‐coated or HA‐coated implants over uncoated rough titanium implants in the short term.

Biochemical Modification of Titanium Oral Implants: Evidence from In Vivo Studies

The discovery of osseointegration of titanium implants revolutionized the dental prosthesis field. Traditionally, implants have a surface that is processed by additive or subtractive techniques, which have positive effects on the osseointegration process by altering the topography. In the last decade, innovative implant surfaces have been developed, on which biologically active molecules have been immobilized with the aim of increasing stimulation at the implant-biological tissue interface, thus favoring the quality of osseointegration. Among these molecules, some are normally present in the human body, and the techniques for the immobilization of these molecules on the implant surface have been called Biochemical Modification of Titanium Surfaces (BMTiS). Different techniques have been described in order to immobilize those biomolecules on titanium implant surfaces. The aim of the present paper is to present evidence, available from in vivo studies, about the effects of biochemical modification of titanium oral implants on osseointegration.

The Impact of Dental Implant Surface Modifications on Osseointegration and Biofilm Formation

Implant surface design has evolved to meet oral rehabilitation challenges in both healthy and compromised bone. For example, to conquer the most common dental implant-related complications, peri-implantitis, and subsequent implant loss, implant surfaces have been modified to introduce desired properties to a dental implant and thus increase the implant success rate and expand their indications. Until now, a diversity of implant surface modifications, including different physical, chemical, and biological techniques, have been applied to a broad range of materials, such as titanium, zirconia, and polyether ether ketone, to achieve these goals. Ideal modifications enhance the interaction between the implant's surface and its surrounding bone which will facilitate osseointegration while minimizing the bacterial colonization to reduce the risk of biofilm formation. This review article aims to comprehensively discuss currently available implant surface modifications commonly used in implantology in terms of their impact on osseointegration and biofilm formation, which is critical for clinicians to choose the most suitable materials to improve the success and survival of implantation.

Bone healing at collagenated bicortically installed implants: an experimental study in rabbits

PURPOSE

To study the healing at collagenated bicortically installed implants.

METHODS

Twenty albino New Zealand rabbits were used for implant installation. Two implants with a double acid etched surface, coated with a collagen type I or left uncoated, were installed bicortically in the metaphysis and in the diaphysis of each tibia. Ten rabbits were euthanized after 2 weeks and ten after 6 weeks after installation. Ground sections were prepared for histological analyses that were performed both in the cortical layers and in the marrow regions.

RESULTS

After 2 weeks of healing, highest amounts of new bone were found at the collagenated implants (43.2 ± 6.0%) compared to the standard implants (33.9 ± 6.1%; p = 0.022). After 6 weeks of healing, similar percentages of new bone were observed, being 51.8 ± 7.3% and 50.9 ± 9.6% (p = 0.678) for the standard and collagenated surfaces, respectively.

CONCLUSIONS

A coated surface with collagen type I promoted bone apposition in the earliest periods of healing. However, the effect vanished over time so that similar results were obtained after 6 weeks of healing.

Effect of Different Morphology of Titanium Surface on the Bone Healing in Defects Filled Only with Blood Clot: A New Animal Study Design

Background

The objective of the present histologic animal study was to analyze whether roughness of the titanium surface can influence and/or stimulate the bone growth in defects filled with the blood using a rabbit tibia model.

Materials and Methods

Forty sets (implant and abutment), dental implant (3.5 mm in diameter and 7 mm in length) plus healing abutment (2.5 mm in diameter), were inserted in the tibiae of 10 rabbits. Moreover, twenty titanium discs were prepared. The abutment and discs were treated by 4 different methods and divided into 4 groups: (group A) machined abutments (smooth); (group B) double acid etching treatment; (group C) treatment with blasting with particles of aluminum oxide blasted plus acid conditioning; (group D) treatment with thorough blasting with particles of titanium oxide plus acid conditioning. The discs were used to characterize the surfaces by a profilometer and scanning electronic microscopy.

Results

After 8 weeks, the new bone formation around the sets of the samples was analyzed qualitatively and quantitatively in relation to bone height from the base of the implant and presence of osteocytes. Group C (1.50±0.20 mm) and group D (1.62±0.18 mm) showed bone growth on the abutment with higher values compared to group A (0.94±0.30 mm) and group B (1.19±0.23 mm), with significant difference between the groups (P < 0.05). In addition, osteocyte presence was higher in groups with surface treatment related to machined (P < 0.05).

Conclusions

Within the limitations of the present study, it was possible to observe that there is a direct relationship between the roughness present on the titanium surface and the stimulus for bone formation, since the presence of larger amounts of osteocytes on SLA surfaces evidenced this fact. Furthermore, the increased formation of bone tissue in height demonstrates that there is an important difference between the physical and chemical methods used for surface treatment.

Peri-Implant Bone Behavior after Single Drill versus Multiple Sequence for Osteotomy Drill

Objectives

The present study aims to compare the drilling protocol effect on osseointegration event in three commercially available titanium dental implants with different drill protocol using a rabbit tibia model.

Materials and Methods

Three different drilling sequences were compared as follows: drilling sequence using a single unique drill of 4.2 mm conical implant (Group 1), drilling sequence using 3 consecutive cylindrical drills for a 4.1 mm cylindrical implant (Group 2), and drilling sequence using 3 consecutive conical drills for a 4.3 mm conical implant (Group 3). For each group, 18 drilling procedures and implant placements were performed, totalizing 54 commercially available titanium dental implants. The samples were removed 6 weeks after implantation. Resonance frequency analyses (RFA) were performed immediately after the implantation, and at 6 weeks removal torque test (RTt) and histological analysis were performed.

Results

The RFA measured showed statistical difference between the groups in time 1 and no significant statistical differences in time 2 (p > 0.05). In the RTt no significant difference was found between the 3 groups tested. Histomorphometric analysis showed no significant difference between groups in the bone-to-implant contact% (p > 0.05).

Conclusion

In the present preclinical study, osteotomy using a single bur did not show differences regarding the proposed and evaluated tests parameters for assessing the peri-implant behavior.

Wool-derived keratin hydrogel enhances implant osseointegration in cancellous bone

AIM

This study investigated whether a keratin hydrogel derived from wool enhances ossointegration of dental implants, using a cancellous bone model in sheep.

METHOD

Ten female sheep received one dental implant per hind leg in the distal femoral condyles. Test implants were coated with 1 mL of keratin hydrogel containing sulphonated keratin and hydroxyapatite; control implants remained uncoated; implants were not functionally loaded axially. Biomechanical stability was tested with resonance frequency analysis (RFA) at placement and euthanasia. Animals were sacrificed after 4 weeks and resin-embedded histomorphometry performed.

FINDINGS

Bone appeared denser and more mature around the keratin-treated test implants. Average % bone-implant contact was significantly increased for the test (58.1 ± 4.6 [SD]%) compared to control implants (34.4 ± 7.5%) (p = 0.01). RFA values were lower for control (76.5 ± 4.2 ISQ) than test implants (80.4 ± 1.4) after 4 weeks (p = 0.04).

CONCLUSION

the increase in osseointegration found in this model suggests that keratin hydrogel has the potential to enhance the successful osseointegration of dental implants placed into poor quality bone. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2447-2454, 2018.

Does incorporating collagen and chondroitin sulfate matrix in implant surfaces enhance osseointegration? A systematic review and meta-analysis

Implant surface modification has been used to improve osseointegration. However, evidence regarding improved new bone formation (NBF) and osseointegration with the use of collagen-chondroitin sulfate (CS) matrix coated implants remains unclear. The aim of this study was to assess the efficacy of collagen-CS matrix coating on the osseointegration of implants. The focused question was "Does the incorporation of collagen-CS matrix in implant surfaces influence osseointegration?" To answer the question, indexed databases were searched up to July 2017 using various combinations of the key words "collagen", "chondroitin sulfate", "osseointegration", and "implants". The initial literature search identified 497 articles, of which 18 reporting experimental studies fulfilled the inclusion criteria. Thirteen of the studies included (72%) reported that implants coated with a collagen-CS matrix presented higher NBF, bone-to-implant contact, and/or bone volume density. The strength of this observation was supported by meta-analysis results. Nevertheless, the results should be interpreted with caution due to the lack of standardization regarding the dosage formulation of collagen-CS, short-term follow-up, and lack of assessment of confounders. On experimental grounds, the incorporation of collagen-CS matrix into implant surfaces appears to promote osseointegration. From a clinical perspective, the results from animal models support phase I studies in healthy humans.

Early Bone Response to Dual Acid-Etched and Machined Dental Implants Placed in the Posterior Maxilla: A Histologic and Histomorphometric Human Study

PURPOSE

To compare the early bone response to implants with dual acid-etched (DAE) and machined (MA) surface, when placed in the posterior human maxilla.

MATERIALS AND METHODS

Fourteen patients received 2 implants in the posterior maxilla: 1 DAE and 1 MA. After 2 months, the implants were retrieved for histologic/histomorphometric evaluation. The bone-to-implant contact (BIC%), bone density in the threaded area (BDTA%), and the bone density (BD%) were calculated. The Wilcoxon matched-pairs signed rank test was used to evaluate differences (BIC%, BDTA%, and BD%) between the surfaces.

RESULTS

In the MA implants, a mean (±SD) BIC%, BDTA%, and BD% of 21.76 (±12.79), 28.58 (±16.91), and 21.54 (±11.67), respectively, was reported. In the DAE implants, a mean (±SD) BIC%, BDTA%, and BD% of 37.49 (±29.51), 30.59 (±21.78), and 31.60 (±18.06), respectively, was reported. Although the mean BIC% of DAE implants value was almost double than that of MA implants, no significant differences were found between the 2 groups with regard to BIC% (P = 0.198) and with regard to BDTA% (P = 0.778) and BD% (P = 0.124).

CONCLUSIONS

The DAE surface increased the periimplant endosseous healing properties in the native bone of the posterior maxilla.

Dental implant bioactive surface modifications and their effects on osseointegration: a review

BACKGROUND

The purpose of this article is to review and update the current developments of biologically active dental implant surfaces and their effect on osseointegration.

METHODS

PubMed was searched for entries from January 2006 to January 2016. Only in-vivo studies that evaluated the effects of biomolecular coatings on titanium dental implants inserted into the bone of animals or humans were included.

RESULTS

Thirty four non-review studies provided data and observations were included in this review. Within the criteria, four categories of biomolecular coatings were evaluated. The potential biomolecules include bone morphogenetic proteins in 8 articles, other growth factors in 8 articles, peptides in 5 articles, and extracellular matrix in 13 articles. Most articles had a healing period of 1 to 3 months and the longest time of study was 6 months. In addition, all studies comprised of implants inserted in animals except for one, which evaluated implants placed in both animals and humans. The results indicate that dental implant surface modification with biological molecules seem to improve performance as demonstrated by histomorphometric analysis (such as percentage of bone-to-implant contact and peri-implant bone density) and biomechanical testing (such as removal torque, push-out/pull-out tests, and resonance frequency analysis).

CONCLUSIONS

Bioactive surface modifications on implant surfaces do not always offer a beneficial effect on osseointegration. Nevertheless, surface modifications of titanium dental implants with biomolecular coatings seem to promote peri-implant bone formation, resulting in enhanced osseointegration during the early stages of healing. However, long-term clinical studies are needed to validate this result. In addition, clinicians must keep in mind that results from animal experiments need not necessarily reflect the human clinical reality.

Dental implant bioactive surface modifications and their effects on osseointegration: a review

Background

The purpose of this article is to review and update the current developments of biologically active dental implant surfaces and their effect on osseointegration.

Methods

PubMed was searched for entries from January 2006 to January 2016. Only in-vivo studies that evaluated the effects of biomolecular coatings on titanium dental implants inserted into the bone of animals or humans were included.

Results

Thirty four non-review studies provided data and observations were included in this review. Within the criteria, four categories of biomolecular coatings were evaluated. The potential biomolecules include bone morphogenetic proteins in 8 articles, other growth factors in 8 articles, peptides in 5 articles, and extracellular matrix in 13 articles. Most articles had a healing period of 1 to 3 months and the longest time of study was 6 months. In addition, all studies comprised of implants inserted in animals except for one, which evaluated implants placed in both animals and humans. The results indicate that dental implant surface modification with biological molecules seem to improve performance as demonstrated by histomorphometric analysis (such as percentage of bone-to-implant contact and peri-implant bone density) and biomechanical testing (such as removal torque, push-out/pull-out tests, and resonance frequency analysis).

Conclusions

Bioactive surface modifications on implant surfaces do not always offer a beneficial effect on osseointegration. Nevertheless, surface modifications of titanium dental implants with biomolecular coatings seem to promote peri-implant bone formation, resulting in enhanced osseointegration during the early stages of healing. However, long-term clinical studies are needed to validate this result. In addition, clinicians must keep in mind that results from animal experiments need not necessarily reflect the human clinical reality.

Impact of Dental Implant Surface Modifications on Osseointegration

Objective. The aim of this paper is to review different surface modifications of dental implants and their effect on osseointegration. Common marketed as well as experimental surface modifications are discussed. Discussion. The major challenge for contemporary dental implantologists is to provide oral rehabilitation to patients with healthy bone conditions asking for rapid loading protocols or to patients with quantitatively or qualitatively compromised bone. These charging conditions require advances in implant surface design. The elucidation of bone healing physiology has driven investigators to engineer implant surfaces that closely mimic natural bone characteristics. This paper provides a comprehensive overview of surface modifications that beneficially alter the topography, hydrophilicity, and outer coating of dental implants in order to enhance osseointegration in healthy as well as in compromised bone. In the first part, this paper discusses dental implants that have been successfully used for a number of years focusing on sandblasting, acid-etching, and hydrophilic surface textures. Hereafter, new techniques like Discrete Crystalline Deposition, laser ablation, and surface coatings with proteins, drugs, or growth factors are presented. Conclusion. Major advancements have been made in developing novel surfaces of dental implants. These innovations set the stage for rehabilitating patients with high success and predictable survival rates even in challenging conditions.

A systematic review and meta-analysis on the influence of biological implant surface coatings on periimplant bone formation

This systematic review and meta-analysis evaluated the influence of biological implant surface coatings on periimplant bone formation in comparison to an uncoated titanium reference surface in experimental large animal models. The analysis was structured according to the PRISMA criteriae. Of the1077 studies, 30 studies met the inclusion criteriae. Nineteen studies examined the bone implant contact (BIC) and were included in the meta-analysis. Overall, the mean increase in BIC for the test surfaces compared to the reference surfaces was 3.7 percentage points (pp) (95% CI -3.9-11.2, p = 0.339). Analyzing the increase in BIC for specific coated surfaces in comparison to uncoated reference surfaces, inorganic surface coatings showed a significant mean increase in BIC of 14.7 pp (95% CI 10.6-18.9, p < 0.01), extracellular matrix (ECM) surface coatings showed an increase of 10.0 pp (95% CI 4.4-15.6, p < 0.001), and peptide coatings showed a statistical trend with 7.1 pp BIC increase (95% CI -0.8-15.0, p = 0.08). In this review, no statistically significant difference could be found for growth factor surface coatings (observed difference -3.3 pp, 95% CI -16.5-9.9, p = 0.6). All analyses are exploratory in nature. The results show a statistically significant effect of inorganic and ECM coatings on periimplant bone formation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2898-2910, 2016.

Assessment of a polyelectrolyte multilayer film coating loaded with BMP-2 on titanium and PEEK implants in the rabbit femoral condyle

The aim of this study was to evaluate the osseointegration of titanium implants (Ti-6Al-4V, noted here TA6V) and poly(etheretherketone) PEEK implants induced by a BMP-2-delivering surface coating made of polyelectrolyte multilayer films. The in vitro bioactivity of the polyelectrolyte film-coated implants was assessed using the alkaline phosphatase assay. BMP-2-coated TA6V and PEEK implants with a total dose of 9.3μg of BMP-2 were inserted into the femoral condyles of New Zealand white rabbits and compared to uncoated implants. Rabbits were sacrificed 4 and 8weeks after implantation. Histomorphometric analyses on TA6V and PEEK implants and microcomputed tomography on PEEK implants revealed that the bone-to-implant contact and bone area around the implants were significantly lower for the BMP-2-coated implants than for the bare implants. This was confirmed by scanning electron microscopy imaging. This difference was more pronounced at 4weeks in comparison to the 8-week time point. However, bone growth inside the hexagonal upper hollow cavity of the screws was higher in the case of the BMP-2 coated implants. Overall, this study shows that a high dose of BMP-2 leads to localized and temporary bone impairment, and that the dose of BMP-2 delivered at the surface of an implant needs to be carefully optimized.

STATEMENT OF SIGNIFICANCE

The presentation of growth factors from material surfaces currently presents significant challenges in academia, clinics and industry. Applying osteoinductive factors to different types of implants, made of metals or polymers, may improve bone repair in difficult situations. Here, we show the effects of an osteoinductive coating made of polyelectrolyte multilayer films on two widely used materials, titanium TA6V alloys and PEEK implants, which were implanted in the rabbit femoral condyle. We show that a too high dose of BMP-2 delivered from the screw surface has a negative short-term effect on bone regeneration in close vicinity of the screw surface. In contrast, bone formation was increased at early times in the empty spaces around the screw. These results highlight the need for future dose-dependence studies on bone formation in response to osteoinductive coatings.

The effects of pulsed electromagnetic field (PEMF) on osteoblast-like cells cultured on titanium and titanium-zirconium surfaces

BACKGROUND

Commercially pure Ti, together with Ti Ni, Ti-6Al-4V, and Ti-6Al-7Nb alloys, are among the materials currently being used for this purpose. Titanium-zirconium (TiZr) has been developed that allows SLActive surface modification and that has comparable or better mechanical strength and improved biocompatibility compared with existing Ti alloys. Furthermore, approaches have targeted making the implant surface more hydrophilic, as with the Straumann SLActive surface, a modification of the SLA surface.

PURPOSE

The aim of this study is to evaluate the effects of pulsed electromagnetic field (PEMF) to the behavior of neonatal rat calvarial osteoblast-like cells cultured on commercially pure titanium (cpTi) and titanium-zirconium alloy (TiZr) discs with hydrophilic surface properties.

MATERIALS AND METHODS

Osteoblast cells were cultured on titanium and TiZr discs, and PEMF was applied. Cell proliferation rates, cell numbers, cell viability rates, alkaline phosphatase, and midkine (MK) levels were measured at 24 and 72 hours.

RESULTS

At 24 hours, the number of cells was significantly higher in the TiZr group. At 72 hours, TiZr had a significantly higher number of cells when compared to SLActive, SLActive + PEMF, and machine surface + PEMF groups. At 24 hours, cell proliferation was significantly higher in the TiZr group than SLActive and TiZr + PEMF group. At 72 hours, TiZr group had higher proliferation rate than machine surface and TiZr + PEMF. Cell proliferation in the machine surface group was lower than both SLActive + PEMF and machine surface + PEMF. MK levels of PEMF-treated groups were lower than untreated groups for 72 hours.

CONCLUSIONS

Our findings conclude that TiZr surfaces are similar to cpTi surfaces in terms of biocompatibility. However, PEMF application has a higher stimulative effect on cells cultured on cpTi surfaces when compared to TiZr.

Clinical evaluation of anodized surface implants submitted to a counter torque of 25 ncm after 60 days of osseointegration: study in humans

INTRODUCTION

Decreasing the time needed for osseointegration has always been a big challenge for modern implantodontics. The main factor which helps to decrease the time needed for osseointegration is the newly developed surfaces being used, as well as their microstructures, in relation to their osseoinductive properties. The aim of this work is to clinically evaluate the osseointegration of the implants when using The anodized surfaces in humans, following a 60 days-period of osseointegration.

METHODOLOGY

Forty-Five implants were placed in different kinds of bones, according to the technique recommended by the manufacturer. Those implants were opened after 60 days of osseointegration. The success of evaluation was made through assessing the counter torque resistance of 25 Ncm. The implants which could withstand the applied torque were considered osseointegrated.

RESULTS

Of the forty-five implants made in different kinds of bones, only one failed to present osseointegration, resulting in a success rate of 97.7 %.

CONCLUSIONS

With this methodology it was possible to conclude that anodized surface implants present primary osseointegration after 60 days of healing, after which they can function normally.

Enhanced osseointegration of titanium implants with nanostructured surfaces: an experimental study in rabbits

Titanium and its alloys are commonly used for dental implants because of their good mechanical properties and biocompatibility. The surface properties of titanium implants are key factors for rapid and stable bone tissue integration. Micro-rough surfaces are commonly prepared by grit-blasting and acid-etching. However, proteins and cells interact with implant surfaces in the nanometer range. The aim of this study was to compare the osseointegration of machined (MA), standard alumina grit-blasted and acid-etched (MICRO) and nanostructured (NANO) implants in rabbit femurs. The MICRO surface exhibited typical random cavities with an average roughness of 1.5 μm, while the NANO surface consisted of a regular array of titanium oxide nanotubes 37±11 nm in diameter and 160 nm thick. The MA and NANO surfaces had a similar average roughness of 0.5 μm. The three groups of implants were inserted into the femoral condyles of New Zealand White rabbits. After 4 weeks, the pull-out test gave higher values for the NANO than for the other groups. Histology corroborated a direct apposition of bone tissue on to the NANO surface. Both the bone-to-implant contact and bone growth values were higher for the NANO than for the other implant surfaces. Overall, this study shows that the nanostructured surface improved the osseointegration of titanium implants and may be an alternative to conventional grit-blasted and acid-etched surface treatments.

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.

Functionalization of biomaterial surfaces using artificial extracellular matrices

Construction of biomaterials with the ability to guide cell function is a topic of high interest in biomaterial development. One approach is using components native to the ECM of the target tissue to generate in vitro a microenvironment that can also elicit specific responses in cells and tissues—an artificial ECM (aECM). The focus is on collagen as the basic material, which can be modified using a number of different glycoproteins, proteoglycans and glycosaminoglycans. Preparation, immobilization and the biochemical characteristics of such aECM are discussed, as well as the in vitro and in vivo response of cells and tissues, illustrating the potential of such matrices to direct cell fate.

Bone Formation in a Local Defect around Dental Implants Coated with Extracellular Matrix Components

PURPOSE

The coating of implant surfaces with components of the extracellular matrix offers an approach to influence peri-implant bone healing. In this study, bone healing around coated implants is analyzed in a peri-implant defect model.

MATERIALS AND METHODS

Eight months after extraction of the premolar teeth, six dogs received 48 implants (eight per animal) in the mandible. Implant surfaces were sandblasted and acid-etched, and some were additionally coated with collagen type II and chondroitin sulfate (collagen/CS). On each side of the mandible, implants either had no peri-implant defect (control side) or a vertical defect of 5 mm in depth and 0.5, 1.0, or 2.0 mm in width. Implants healed submerged for 8 weeks. Fluorochrome staining, histology, and histomorphometry were used to analyze implant osseointegration.

RESULTS

Fluorochrome labels showed an increased mineralization around collagen/CS-coated surfaces at 4 weeks (p = .031). Histomorphometry generally showed lower vertical and horizontal bone apposition with increasing gap size for both surface types. In gapless sites and 0.5-mm gaps, collagen/CS coated implants showed increased bone volume in areas directly adjacent to the implant, in comparison with uncoated implants (p < .05).

CONCLUSION

The width of the peri-implant gap influences peri-implant bone formation. Complete filling of all gaps by newly formed bone could not be observed around either surface. In proximity to the surface, implant surface coating by collagen/CS positively influenced bone formation.

Ultrathin sP(EO-stat-PO) hydrogel coatings are biocompatible and preserve functionality of surface bound growth factors in vivo

Hydrogel coatings prepared from reactive star shaped polyethylene oxide based prepolymers (NCO-sP(EO-stat-PO)) minimize unspecific protein adsorption in vitro, while proteins immobilized on NCO-sP(EO-stat-PO) coatings retain their structure and biological function. The aim of the present study was to assess biocompatibility and the effect on early osseointegrative properties of a NCO-sP(EO-stat-PO) coating with additional RGD-peptides and augmentation with bone morphogenetic protein-4 (BMP) used on a medical grade high-density polyethylene (HDPE) base under in vivo circumstances. For testing of biocompatibility dishes with large amounts of bulk NCO-sP(EO-stat-PO) were implanted subcutaneously into 14 Wistar rats. In a second set-up functionalization of implants with ultrathin surface layers by coating ammonia-plasma treated HDPE with NCO-sP(EO-stat-PO), functionalization with linear RGD-peptides, and augmentation with RGD and BMP-4 was analyzed. Therefore, implants were placed subcutaneously in the paravertebral tissue and transcortically in the distal femur of another 14 Wistar rats. Both tests revealed no signs of enhanced inflammation of the surrounding tissue analyzed by CD68, IL-1ß-/TNF-α-antibody staining, nor systemic toxic reactions according to histological analysis of various organs. The mean thickness of the fibrous tissue surrounding the femoral implants was highest in native HDPE-implants and tended to be lower in all NCO-sP(EO-stat-PO) modified implants. Micro-CT analysis revealed a significant increase of peri-implant bone volume in RGD/BMP-4 coated samples. These results demonstrate that even very low amounts of surface bound growth factors do have significant effects when immobilized in an environment that retains their biological function. Hence, NCO-sP(EO-stat-PO)-coatings could offer an attractive platform to improve integration of orthopedic implants.

The in vivo effect of P-15 coating on early osseointegration

The aim of this study was to evaluate mechanically and morphologically the effect of a specific peptide sequence P-15, when incorporated into implant surfaces. Three types of implants were used for the study: Group A: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition, Group B: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition + P-15 incorporation, and as control, Group C: commercially pure titanium implant (blasted and acid etched). After a topographical characterization, transcortical osteotomies were made, and all implant groups (102 implants per group) were randomly placed bilaterally in the tibiae of adult beagle dogs (n = 24). At, 1, 2, and 4 weeks post-surgery, the animals were sacrificed and the samples were retrieved for removal torque tests, for nano indentation, and for histomorphometrical analysis. The results (mean ± 95% CI) showed that Group B (34.4 ± 8.7%) presented statistically higher bone-to-implant contact than the other groups (A = 23.9 ± 7.8%; C = 21.7 ± 8.3%) at 1 week, indicating an enhanced osteogenesis due to the peptide incorporation. The results suggested that the incorporation of P-15 to implant surfaces increased its bioactivity and the effects were notable especially in the early stages of the healing process.

Chondroitin sulfate and sulfated hyaluronan-containing collagen coatings of titanium implants influence peri-implant bone formation in a minipig model

An improved osseous integration of dental implants in patients with lower bone quality is of particular interest. The aim of this study was to evaluate the effect of artificial extracellular matrix implant coatings on early bone formation. The coatings contained collagen (coll) in conjunction with either chondroitin sulfate (CS) or sulfated hyaluronan (sHya). Thirty-six screw-type, grit-blasted, and acid-etched titanium implants were inserted in the mandible of 6 minipigs. Three surface states were tested: (1) uncoated control (2) coll/CS (3) coll/sHya. After healing periods of 4 and 8 weeks, bone implant contact (BIC), bone volume density (BVD) as well as osteoid related parameters were measured. After 4 weeks, control implants showed a BIC of 44% which was comparable to coll/CS coated implants (48%) and significantly higher compared to coll/sHya coatings (37%, p = 0.012). This difference leveled out after 8 weeks. No significant differences could be detected for BVD values after 4 weeks and all surfaces showed reduced BVD values after 8 weeks. However, at that time, BVD around both, coll/CS (30%, p = 0.029), and coll/sHya (32%, p = 0.015), coatings was significantly higher compared to controls (22%). The osteoid implant contact (OIC) showed no significant differences after 4 weeks. After 8 weeks OIC for controls was comparable to coll/CS, the latter being significantly higher compared to coll/sHya (0.9% vs. 0.4%, p = 0.012). There were no significant differences in osteoid volume density. In summary, implant surface coatings by the chosen organic components of the extracellular matrix showed a certain potential to influence osseointegration in vivo.

Addition of nanoscaled bioinspired surface features: A revolution for bone related implants and scaffolds?

Our expanding ability to handle the "literally invisible" building blocks of our world has started to provoke a seismic shift on the technology, environment and health sectors of our society. During the last two decades, it has become increasingly evident that the "nano-sized" subunits composing many materials—living, natural and synthetic—are becoming more and more accessible for predefined manipulations at the nanosize scale. The use of equally nanoscale sized or functionalised tools may, therefore, grant us unprecedented prospects to achieve many therapeutic aims. In the past decade it became clear that nano-scale surface topography significantly influences cell behaviour and may, potentially, be utilised as a powerful tool to enhance the bioactivity and/ or integration of implanted devices. In this review, we briefly outline the state of the art and some of the current approaches and concepts for the future utilisation of nanotechnology to create biomimetic implantable medical devices and scaffolds for in vivo and in vitro tissue engineering,with a focus on bone. Based on current knowledge it must be concluded that not the materials and surfaces themselves but the systematic biological evaluation of these new material concepts represent the bottleneck for new biomedical product development based on nanotechnological principles.

Poly(L-lactide-co-glycolide) scaffolds coated with collagen and glycosaminoglycans: impact on proliferation and osteogenic differentiation of human mesenchymal stem cells

In this study, we analyzed poly(L-lactide-co-glycolide) (PLGA) scaffolds modified with artificial extracellular matrices (aECM) consisting of collagen type I, chondroitin sulphate, and sulphated hyaluronan (sHya). We investigated the effect of these aECM coatings on proliferation and osteogenic differentiation of human mesenchymal stem cells (hMSC) in vitro. We found that scaffolds were homogeneously coated, and cross-linking of aECM did not significantly influence the amount of collagen immobilized. Cell proliferation was significantly increased on cross-linked surfaces in expansion medium (EM), but was retarded on cross-linked and non-cross-linked collagen/sHya coatings. The alkaline phosphatase activity was increased on sHya-containing coatings in EM even without the presence of differentiation supplements, but was six to ten times higher in differentiation medium (DM) and comparable for cross-linked and non-cross-linked collagen/sHya. The highest amount of calcium phosphate mineral was deposited on day 28 on cross-linked collagen/sHya. Therefore, coatings of PLGA scaffolds with collagen/sHya promoted the osteogenic differentiation of hMSCs in vitro and might be an interesting candidate for the modification of PLGA for bone reconstruction in vivo.

Effect of force on alveolar bone surrounding miniscrew implants: a 3-dimensional microcomputed tomography study

INTRODUCTION

The primary aim of this study was to better understand how bone adapts to forces applied to miniscrew implants. A secondary aim was to determine whether the direction of force applied to miniscrew implants has an effect on bone surrounding the miniscrew implants.

METHODS

A randomized split-mouth design, applied to 6 skeletally mature male foxhound dogs, was used to compare miniscrew implants loaded for 9 weeks with 200 or 600 g to unloaded control miniscrew implants. By using microcomputed tomography, with an isotropic resolution of 6 μm, bone volume fractions (bone volume/total volume) were calculated for bone around the entire miniscrew implant surface. Bone volume fractions were calculated for bone 6 to 24, 24 to 42, and 42 to 60 μm from the miniscrew implant surface. For each loaded miniscrew implant, the bone volume fraction was also calculated for 2 compression and 2 noncompression zones.

RESULTS

The 6 to 24-μm layer showed a significantly lower (P <0.05) bone volume fraction than did the 24 to 42-μm and the 42 to 60-μm layers, which were not significantly different. The bone volume fractions of cortical bone surrounding the apical aspects of the unloaded miniscrew implants were significantly greater (P <0.05) than the bone volume fractions of cortical bone surrounding the loaded miniscrew implants. In contrast, the bone volume fractions of noncortical bone surrounding loaded miniscrew implants were significantly greater (P <0.05) than the bone volume fractions of bone surrounding the unloaded miniscrew implants. Miniscrew implants loaded with 200 g showed significantly greater (P <0.05) amounts of noncortical bone volume fractions than did miniscrew implants loaded with 600 g. With both 200 and 600 g, zones under compression had significantly greater bone volume fractions than did the noncompression zones.

CONCLUSIONS

The application of force, the amount of force applied, and the direction of force all have significant effects on the amounts of bone produced around miniscrew implants.

Biofunctionalization of the implant surface with different concentrations of a synthetic peptide (P-15)

OBJECTIVE

This study aimed at identifying the ideal concentration of a biofunctional surface coating of dental implants with a synthetic peptide (P-15). In a previous study, P-15 was shown to enhance osseointegration parameters.

MATERIAL AND METHODS

Implants (modified ANKYLOS(®) A8; FRIADENT Plus(®) surface) with five different concentrations (0-400 μg/ml) of a P-15 coating as well as uncoated controls were inserted in the frontal bone of 45 adult domestic pigs. The histomorphometric and microradiographic findings for the coated implants were compared to those for the uncoated ones after 7, 14, and 30 days.

RESULTS

No significant differences were observed comparing the peri-implant bone density between the coated and uncoated implants The bone-to-implant contact, as the primary histological parameter for osseointegration, showed high rates for all surfaces investigated (between 73.3 ± 17.9% for the control and 81.9 ± 15.2% for P15 20 μg/ml after 30 days).

CONCLUSIONS

No significant benefit on osseointegration of a biofunctional P-15 coating of dental implants could be displayed in the present study.

Effects of type I collagen coating on titanium osseointegration: histomorphometric, cellular and molecular analyses

The investigation of titanium (Ti) surface modifications aiming to increase implant osseointegration is one of the most active research areas in dental implantology. This study was carried out to evaluate the benefits of coating Ti with type I collagen on the osseointegration of dental implants. Acid etched Ti implants (AETi), either untreated or coated with type I collagen (ColTi), were placed in dog mandibles for three and eight weeks for histomorphometric, cellular and molecular evaluations of bone tissue response. While the histological aspects were essentially the same with both implants being surrounded by lamellar bone trabeculae, histomorphometric analysis showed more abundant bone formation in ColTi, mainly at three weeks. Cellular evaluation showed that cells harvested from bone fragments in close contact with ColTi display lower proliferative capacity and higher alkaline phosphatase activity, phenotypic features associated with more differentiated osteoblasts. Confirming these findings, molecular analyses showed that ColTi implants up-regulates the expression of a panel of genes well known as osteoblast markers. Our results present a set of evidences that coating AETi with collagen fastens the osseointegration by stimulating bone formation at the cellular and molecular levels, making this combination of morphological and biochemical modification a promising approach to treat Ti surfaces.

Biological response to titanium implants coated with nanocrystals calcium phosphate or type 1 collagen in a dog model

OBJECTIVE

The current study aimed to evaluate the osteogenic potential of electrosprayed organic and non-organic surface coatings in a gap-implant model over 4 and 12 weeks of implantation into the dog mandible.

MATERIAL AND METHODS

Sixteen Beagle dogs received experimental titanium implants in the mandible 3 months after removal of left premolars (P2, P3 and P4). Three types of implants were installed in each animal: non-coated implant, nano-CaP coated implant and implant with type 1 collagen coating. Both micro-CT and histomorphometry were used to evaluate peri-implant bone response after implantation periods of 4 and 12 weeks. The bone area percentage was assessed histomorphometrically in three different zones (inner: 0-300 μm; middle: 300-600 μm; and outer: 600-1000 μm) around the implant surface. Bone-bridging of the gap was also calculated for each sample.

RESULTS

Four weeks after implantation, nano-CaP and collagen-coated implants showed significantly higher bone volume (BV) in the inner zone compared with non-coated implants (P < 0.05 and P < 0.01). After 12 weeks, histomorphometric analysis showed comparable amounts of BV between all experimental groups. Also, no significant difference was found in the BV, as measured using micro-CT, between the implant groups. Absolute bone ingrowth measurements were highest for collagen-coated implants, but these differences were not significant.

CONCLUSION

The obtained data failed to provide a consistent favourable effect on bone formation of the collagen coating over 3 months of implantation. It is concluded that the source of the collagen as well as the limited osseous environment overshadowed a possible effect of the applied implant surface modifications. Similarly, the tested nano-apatite surface coating did not improve peri-implant bone ingrowth into a gap-implant model.

Osseointegration of SLActive implants in diabetic pigs

OBJECTIVES

Diabetes mellitus is currently classified as a relative contraindication for implant treatment because of microangiopathies with the consequence of impaired bone regeneration and higher rates of implant failure. The study aim was to investigate peri-implant bone formation in a diabetic animal model in comparison to healthy animals and to evaluate the differences between conventional (SLA(®) ) and modified (SLActive(®) ) titanium implant surfaces on osseointegration.

MATERIAL AND METHODS

Each six implants were placed in the calvaria of 11 diabetic and 4 healthy domestic pigs. At 30 and 90 days after implant placement, the bone-to-implant contact (BIC) and bone density (BD) were appraised. Additionally, the expression of the bone-matrix proteins collagen type I and osteocalcin was evaluated at both points in time by using immunohistochemical staining methods.

RESULTS

Overall, BIC was reduced in the diabetic group at 30 and 90 days. After 90 days, the SLActive(®) implants showed significantly higher BICs compared with the SLA(®) implants in diabetic animals. Peri-implant BD was higher in the SLActive(®) group at 30 and 90 days in healthy and diabetic animals. Collagen type I protein expression was higher using SLA(®) implants in diabetic pigs at 30 days. Values for osteocalcin expression were not consistent.

CONCLUSIONS

The results indicate the negative effect of untreated diabetes mellitus on early osseointegration of dental implants. The modified SLA(®) surface (SLActive(®) ) elicited an accelerated osseointegration of dental implants, suggesting that a better prognosis for implant treatment of diabetic patients is possible.

Bone healing of commercial oral implants with RGD immobilization through electrodeposited poly(ethylene glycol) in rabbit cancellous bone

Immobilization of RGD peptides on titanium (Ti) surfaces enhances implant bone healing by promoting early osteoblastic cell attachment and subsequent differentiation by facilitating integrin binding. Our previous studies have demonstrated the efficacy of RGD peptide immobilization on Ti surfaces through the electrodeposition of poly(ethylene glycol) (PEG) (RGD/PEG/Ti), which exhibited good chemical stability and bonding. The RGD/PEG/Ti surface promoted differentiation and mineralization of pre-osteoblasts. This study investigated the in vivo bone healing capacity of the RGD/PEG/Ti surface for biomedical application as a more osteoconductive implant surface in dentistry. The RGD/PEG/Ti surface was produced on an osteoconductive implant surface, i.e. the grit blasted micro-rough surface of a commercial oral implant. The osteoconductivity of the RGD/PEG/Ti surface was compared by histomorphometric evaluation with an RGD peptide-coated surface obtained by simple adsorption in rabbit cancellous bone after 2 and 4 weeks healing. The RGD/PEG/Ti implants displayed a high degree of direct bone apposition in cancellous bone and achieved greater active bone apposition, even in areas of poor surrounding bone. Significant increases in the bone to implant contact percentage were observed for RGD/PEG/Ti implants compared with RGD-coated Ti implants obtained by simple adsorption both after 2 and 4 weeks healing (P<0.05). These results demonstrate that RGD peptide immobilization on a Ti surface through electrodeposited PEG may be an effective method for enhancing bone healing with commercial micro-rough surface oral implants in cancellous bone by achieving rapid bone apposition on the implant surface.

Functionalization of titanium based metallic biomaterials for implant applications

Surface immobilization with active functional molecules (AFMs) on a nano-scale is a main field in the current biomaterial research. The functionalization of a vast number of substances and molecules, ranging from inorganic calcium phosphates, peptides and proteins, has been investigated throughout recent decades. However, in vitro and in vivo results are heterogeneous. This may be attributed partially to the limits of the applied immobilization methods. Therefore, this paper highlights the advantages and limitations of the currently applied methods for the biological nano-functionalization of titanium-based biomaterial surfaces. The second part describes a newer immobilization system, using the nanomechanical fixation of at least partially single-stranded nucleic acids (NAs) into an anodic titanium oxide layer as an immobilization principle and their hybridization ability for the functionalization of the surface with active functional molecules conjugated to the respective complementary NA strands.

Simulation of adhesion forces and energies of peptides on titanium dioxide surfaces

Force field molecular dynamics simulations on a decapeptide in contact with a rutile (100) surface in aqueous solution are reported. The peptide sequence is part of α(1)-collagen. Force-distance curves yield discrete peaks to the rupture of charged lysine and glutamate side chains from the surface according to the model of contact points. The rupture forces are 0.2-2.2 nN, and the values strongly depend on the charges of surface hydroxyl groups. Adhesion energies are evaluated from the areas of the rupture peaks. For proton charges of 0.4 and 1, adhesion energies between 40 and 190 kJ/mol were found being comparable to recent ab initio molecular dynamics results. Flips in the torsional angles of the peptide are observed during restrained desorption. The partial charges of hydroxyproline are revised, and the polarization of the C(β)-C(γ) bond as well as the ring pucker conformations are taken into account. It is shown that transition from collagen to helix fold is more likely for hydroxyproline than for proline and might be relevant for differences in the properties of POG (proline, hydroxyproline, glycine) and PPG collagen sequences.