Variation of roughness and adhesion strength of deposited apatite layers on titanium dental implants

It is known that surface roughness and chemical composition of the titanium surface influence the osseointegration of titanium implants. Most commercial dental implants offer a shot-blasted rough surface. It is also known that apatite layers coating the surface of titanium implants improve bone response, but the adhesion of the layer to the substrate poses some problems.In this study the roughness and adhesion strength to a titanium dental implant surface of an apatite layer deposited via wet chemistry after a thermochemical treatment were compared with those of plasma-sprayed apatite layers and machined titanium surfaces. Different surface conditions have been studied: (a) as-received machined dental implant surface; (b) grit-blasted titanium surface; (c) grit-blasted and thermochemically-treated titanium surface; (d) titanium surfaces coated with plasma-sprayed apatite. The morphology and roughness of the samples were measured and compared. The adhesion of the apatite layers to the titanium was compared by means of a scratch test.Measured roughness showed that the deposition of an apatite layer did not affect roughness but plasma-sprayed apatite produced a decrease on roughness values when compared to control samples. Both roughness and adhesion strength of the deposited apatite layer to the titanium substrate were higher than those of the plasma-sprayed apatite.     

Morphological and animal study of titanium dental implant surface induced by blasting and high intensity pulsed Nd-glass laser

Machined dental implants of titanium were blasted with Al₂O₃ powder of 250 μm particle size. The surface was irradiated in vacuum with a Nd-glass pulsed laser at 1–3 J pulse energies. The morphology of these surfaces was investigated by optical and scanning electron microscopy. The low intensity laser treatment resulted in some new irregularities but we can observe the blasted elements and caves from the original blasted surface too. The blasted elements were washed out and a new surface morphology was induced by the high intensity laser treatment.The osseointegration was determined by measuring the removal torque in the rabbit experiments. The results were referred to the as machined surface. The blasting slightly increased the removal torque. The laser irradiation increased the removal torque significantly, more by a factor of 1.5 compared to the reference at high laser intensity. This shows the influence of the surface morphology on the osseointegration.The combination of the blasting with the laser irradiation is considered a method to determine the morphology optimal for the osseointegration because the pulsed laser irradiation caused modifications of the micrometer sized surface elements and decreases possible surface contamination.     

Human-osteoblast proliferation and differentiation on grit-blasted and bioactive titanium for dental applications

Physico-chemical and topographical surface quality of commercially pure titanium (c.p. Ti) dental implants is one of the most influencing factors in the improvement of their osseointegration. In this sense, previously, a two-step method (2S) for obtaining bioactive blasted-rough titanium surfaces was developed for improving short-term (due to its bioactivity) and long-term (due to its roughness) osseointegration. This 2S-method consists of: (1) Grit blasting on titanium surface in order to roughen it, and (2) thermo-chemical (TCh) treatment in order to obtain a bioactive surface with bone-bonding ability. The aim of the present work is to evaluate the in vitro human-osteoblast response (proliferation, differentiation – ALP activity- and cell morphology-studied by environmental scanning electron microscopy) of rough c.p. Ti (grit blasted), bioactive c.p. Ti (thermo-chemically treated) and rough-bioactive c.p. Ti (2S-treated). Different grit materials (Al₂O₃ and SiC) have been used in order to investigate their influence. The results showed that cell adhesion was statistically higher for the rough and bioactive surfaces, whatever the grit used. Cells proliferated very well on all the c.p. Ti surfaces. If comparing groups with and without TCh (all other treatments being equal) the ALP was always higher in the groups with TCh, indicating stimulation of osteoblast differentiation because of TCh, more significantlly in the groups that were first blasted. Those ALP results were accompanied by a decrease in the value of proliferation, which shows the good behavior of the cells. This results suggest that a rough and bioactive-titanium surface obtained by 2S-treatment enhances adhesion and differentiation activity of human osteoblasts cells.     

Comparison of early osseointegration between laser-treated/acid-etched and sandblasted/acid-etched titanium implant surfaces

This study was designed to compare the early osseointegration of titanium surfaces prepared via laser-treated/acid-etched (LA) and sandblasted/acid-etched (SLA) in dogs. Titanium implants were divided into two groups: Surfaces of the experimental group were treated via LA, while in the control group, surfaces were treated via SLA. The physical and chemical properties of LA and SLA surfaces were tested and compared. Sixteen implants with LA or SLA surfaces were placed into the tibias of four beagle dogs, each treatment group received two implants per single tibia. The dogs were sacrificed two and four weeks after implant placement. Scanning electron microscopy showed that both the LA and SLAs surface exhibited rough structures with micro pores sized 1–3?μm. In the LA surface, regular melting points were observed. However, in the SLA surface, the structure was irregular and few oxide aluminum particles still remained. Only titanium and a small amount of titanium compounds were detected on LA surfaces, while Al was found of SLA surfaces. The LA surface roughness was above that of SLA surfaces (LA: Ra: 2.1?μm; SLA: Ra :1.53?μm; P?<?0.01). Both groups exhibited good osseointegration and no significant differences were found in the BIC% at two or four weeks between both groups (P?>?0.05). Both groups exhibited good osseointegration; however, the LA surface was cleaner and more uniform than the SLA surface, and no significant differences were found between both groups.     

Controlled oxidative nanopatterning of microrough titanium surfaces for improving osteogenic activity

To further enhance the biological properties of acid-etched microrough titanium surfaces, titania nanotextured thin films were produced by simple chemical oxidation, without significantly altering the existing topographical and roughness features. The nanotextured layers on titanium surfaces can be controllably varied by tuning the oxidation duration time. The oxidation treatment significantly reduced water contact angles and increased the surface energy compared to the surfaces prior to oxidation. The murine bone marrow stromal cells (BMSCs) were used to evaluate the bioactivity. In comparison, oxidative nanopatterning of microrough titanium surfaces led to improved attachment and proliferation of BMSCs. The rate of osteoblastic differentiation was also represented by the increased levels of alkaline phosphatase activity and mineral deposition. These data indicated that oxidative nanopatterning enhanced the biological properties of the microrough titanium surfaces by modulating their surface chemistry and nanotopography. Based on the proven mechanical interlocking ability of microtopographies, enhancement of multiple osteoblast functions attained by this oxidative nanopatterning is expected to lead to better implant osseointegration in vivo.     

Promoting Bone Mesenchymal Stem Cells and Inhibiting Bacterial Adhesion of Acid-Etched Nanostructured Titanium by Ultraviolet Functionalization

Titanium(Ti) and its alloys are used extensively in orthopedic implants because of their excellent biocompatibility,mechanical properties and corrosion resistance. However,titanium-based implant materials face many severe complications,such as implant loosening due to poor osseointegration and bacterial infections,which may lead to implant failure. Hence,preparing a biomaterial surface,which enhances the interactions with host cells and inhibits bacterial adhesion,may be an optimal strategy to reduce the incidence of implant failure. This study aims to improve osseointegration and confer antibacterial properties on Ti through a combination of two surface modifications including nanostructuring generated by acid etching and ultraviolet(UV) light treatment.Our results showed that without UV treatment,the acid etching treatment of Ti surface was effective at both improving the adhesion of bone mesenchymal stem cells(BMSCs) and increasing bacterial adhesion. A further UV treatment of the acid-etched surface however,not only significantly improved the cell adhesion but also inhibited bacterial adhesion. The acid-etched nanostructured titanium with UV treatment also showed a significant enhancement on cell proliferation,alkaline phosphatase(ALP) activity and mineralization. These results suggest that such nanostructured materials with UV treatment can be expected to have a good potential in orthopedic applications.     

Unravelling the effect of macro and microscopic design of dental implants on osseointegration: a randomised clinical study in minipigs

Several dental implants are commercially available and new prototype design are constantly being fabricated. Nevertheless, it is still unclear what parameters of the design affect most the osseointegration of dental implants. The purpose of this study is to assess the effects of the microscopic and macroscopic design of dental implants in the osseointegration by comparing three macroscopic designs (Straumann tissue level (STD), essential cone (ECD) and prototype design (PD)) and six surface treatments. A total of 96 implants were placed in 12 minipigs. The implant stability quotient (ISQ), was assessed at the time of implantation, as well as at 2, 4 and 8 weeks. Histomorphometric and statistical analyses were conducted at the different sacrifice times, being 2, 4 and 8 weeks, to analyse the bone to implant contact (BIC), the bone area density (BAT) and the density of bone outside the thread region (ROI). The macroscopic design results showed higher ISQ values for the ECD, whereas the histomorphometric analysis showed higher ossoeintegration values for the STD. Regarding the microscopic design, both Sandblasted plus acid etching (hydrochloric/sulphuric acid) in a nitrogen atmosphere (SLActive) and Shot-blasted or bombarded with alumina particles and posterior alkaline immersion and thermal treatment (ContacTi) showed superior results in terms of osseointegration and reduced the osseointegration times from 8 weeks to 4 weeks compared to the other analysed surfaces. In conclusion, each of the macroscopic and microscopic designs need to be taken into account when designing novel dental implants to enhance the osseointegration process.     

The synergistic effect of 3D-printed microscale roughness surface and nanoscale feature on enhancing osteogenic differentiation and rapid osseointegration

Personalized precision therapy and rapid osseointegration are the main development directions of dental implants.3 D printing is a vital advanced manufacturing technology for personalized precision therapy.However,the osteogenesis of the 3 D printed Ti6 Al4 V implants is unsatisfactory.From the bionic perspective,the hierarchical micro/nano-topography can mimic the microenvironment of the multilevel structure of natural bone tissue and may endow the implant surface with superior bioactivity.In the present study,the hierarchical micro/nano-topography was successfully fabricated by construction the nanoscale feature on 3 D printed microscale roughness surface of 3 D-printed Ti6 Al4 V implants by alkali-heat treatment and hydrothermal treatment.Then the cell biological responses in vitro and osseointegration performance in vivo were systematically evaluated.The hierarchical micro/nano-topography evidently increased the roughness,improved the hydrophilicity and accelerated the hydroxyapatite deposition and mineralization,which significantly enhanced the adhesion,differentiation and extracellular matrix mineralization of bone marrow derived mesenchymal stromal cells(BMSCs).Most importantly,the hierarchical micro/nano-topography on 3 D-printed implants facilitated the new bone formation and rapid osseointegration in vivo.Our study suggested that 3 D-printed implant with micro/nano-topography may be a promising candidate to be applied in orthopedic field to meet the need of customized therapy and rapid osseointegration.     

Roughened titanium surfaces with silane and further RGD peptide modification in vitro

The strategy to achieve osteoregeneration of dental implants during early-stage regeneration is strongly related to surface conditions for achieving highly successful effects after implantation. Surface modifications, namely, mechanical ground, silanization, bonded and sandblasted with pentasequence Gly-Arg-Gly-Asp-Ser (GRGDS) peptide, and acid-etched with Arg-Gly-Asp (RGD) peptide, were compared for their ability to support cell attachment, proliferation, and differentiation on titanium surfaces. The characteristics and comparative in vitro bio-interactions toward osteoprogenitor cells were tested in the four groups with various surface modifications. Compared with the other groups, the sandblasted and acid-etched, and silane with subsequent RGD peptide modified surfaces had the smallest wetting angle, absence of a significant cell viability difference, and largest quantity of alkaline phosphatase production during the expressions of early-stage cell differentiation. The method of synthesizing GRGDS peptides on roughened titanium surfaces has the potential to provide a combination of early bone regeneration and implant of long-term anchored capabilities.     

Bioactive TiOB‐Coating on Titanium Alloy Implants Enhances Osseointegration in a Rat Model

The surface properties of titanium alloy implants for improved osseointegration in orthopaedic and dental surgery have been modified by many technologies. Hydroxyapatite coatings with a facultative integration of growth factors deposited by plasma spraying showed improved osseointegration. Our approach in order to enhance osseointegration was carried out by a surface modification method of titanium alloy implants called plasma chemical oxidation (PCO). PCO is an electrochemical procedure that converts the nm‐thin natural occurring titanium‐oxide layer on an implant to a 5 µm thick ceramic coating (TiOB‐surface). Bioactive TiOB‐surfaces have a porous microstructure and were loaded with calcium and phosphorous, while bioinert TiOB‐surfaces with less calcium and phosphorous loadings are smooth. A rat tibial model with bilateral placement of titanium alloy implants was employed to analyze the bone response to TiOB‐surfaces in vivo. 64 rats were randomly assigned to four groups of implants: (i) pure titanium alloy (control), ii) titanium alloy, type III anodization, (iii) bioinert TiOB‐surface, and (iv) bioactive TiOB‐surface. Mechanical fixation was evaluated by pull out tests at 3 and 8 weeks. The bioactive TiOB‐surface showed significantly increased shear strength at 8 weeks compared to all other groups.     

The early osseointegration of the laser-treated and acid-etched dental implants surface: an experimental study in rabbits

The aim of the study was to evaluate early osseointegration of the laser-treated and acid-etched implant surface after the installation in rabbit tibias for 4 weeks. A total of 56 screw-shaped implants were grouped as follows: group A: implants were turned surface; group B: implants were laser-treated surface; group C: implants were acid-etched; group D: Implants were laser-treated and acid-etched surface. After 4 weeks, the removal torques were: group A: 13.21 ± 11.30 Ncm; group B: 29.73 ± 8.32 Ncm; group C: 30.31 ± 9.45 Ncm; group D: 35.76 ± 7.58 Ncm; The averages of bone-to-implant contact (BIC) were as follows: group A: 27.30 ± 6.55%; group B: 38.00 ± 8.56%; group C: 42.71 ± 8.48%; group D: 49.71 ± 9.21%. The removal torque and bone-to-implant contact measurements yielded statistically significant differences between the treated groups and turned group (P < 0.05); The laser-treated and acid-etched surface achieved higher Bone-to-Implant Contact than the laser-treated surface (P < 0.05), but there was no statistically significant difference between the laser-treated and acid-etched surface and the acid-etched surface in bone-to-implant contact (P > 0.05). In the present study, it was concluded that the laser-treated and acid-etched implants had good osteoconductivity and was a potential material for dental implantation.     

Correlation between primary stability and bone healing of surface treated titanium implants in the femoral epiphyses of rabbits

The aim of this study was to analyse the stability and osseointegration of surface treated titanium implants in rabbit femurs. The implants were either grit-blasted and acid-etched (BE Group), calcium phosphate (CaP) coated by using the electrodeposition technique, or had bioactive molecules incorporated into the CaP coatings: either cyclic adenosine monophosphate (cAMP) or dexamethasone (Dex). Twenty four cylindrical titanium implants (n = 6/group) were inserted bilaterally into the femoral epiphyses of New Zealand White, female, adult rabbits for 4 weeks. Implant stability was measured by resonance frequency analysis (RFA) the day of implantation and 4 weeks later, and correlated to histomorphometric parameters, bone implant contact (BIC) and bone growth around the implants (BS/TS 0.5 mm). The BIC values for the four groups were not significantly different. That said, histology indicated that the CaP coatings improved bone growth around the implants. The incorporation of bioactive molecules (cAMP and Dex) into the CaP coatings did not improve bone growth compared to the BE group. Implant stability quotients (ISQ) increased in each group after 4 weeks of healing but were not significantly different between the groups. A good correlation was observed between ISQ and BS/TS 0.5 mm indicating that RFA is a non-invasive method that can be used to assess the osseointegration of implants. In conclusion, the CaP coating enhanced bone formation around the implants, which was correlated to stability measured by resonance frequency analysis. Furthers studies need to be conducted in order to explore the benefits of incorporating bioactive molecules into the coatings for peri-implant bone healing.     

Incorporation of growth factors into medical devices via biomimetic coatings

Orthopaedic and dental surgeons are fully aware of the need for implants to bond well with the surrounding living bone if long-lasting clinical success is to be achieved. For example, well-bonded hip implants have a 10 year failure rate, which is lowered fivefold if bonding is poor or absent. The techniques that are currently available to impart implant surfaces with the desired osteoconductive properties are essentially limited. To overcome the inherent difficulties, we have developed a 'biomimetic' coating process. By this means, implants with complex surface geometries, such as porous spinal implants, can be furnished with a bone-bonding surface. Furthermore, these coatings can be rendered osteoinductive as well as osteoconductive (by incorporating osteogenic agents). Using this facility, we have induced bone formation at an ectopic site in rats, and have accelerated osseointegration (bone bonding) at an orthotopic dental site in adult miniature pigs. Our preliminary results indicated that these osteoinductive dental implants bond with surrounding bone within one week instead of the usual three weeks. We believe that surfaces coated with biomimetic coatings into which osteogenic growth factors are incorporated hold great potential for use in clinical orthopaedics and dentistry.     

Electrochemical characterization of titanium biomaterials using the Mini-cell System

The aim of this work was the electrochemical characterization of modified Titanium surfaces for implants with help of the Mini-cell System (MCS). The materials tested were Cp titanium specimens, designed for animal experiments, with 8 mm length and 4 mm diameter, with different surface conditions: one had machined surface, the other was blasted with a bioceramic (GB14+AP40) and the third was blasted with aluminum oxide. Roughness measurements were also made on the materials. The results showed that MCS has sensitivity to detect differences in the electrochemical point of view due to surface modifications. The differences between the materials are small, but systematic. The aluminum oxide blasted material had the highest current density, however due to the roughness increase. The material with bioceramics blasting had the highest chemical activity. The higher activity of the bioceramics treated surface was explained as (i) an interaction between the modified surface and electrolyte; or (ii) the calcium phosphate dissolves in the electrolyte and leaves the surface of the metal, and then the free metal reacts immediately to form new titanium oxide. These results may help to explain the biological effects observed by modified surfaces, in particular with bioceramics.     

A comparative study of zirconium and titanium implants in rat: osseointegration and bone material quality

Permanent metal implants are widely used in human medical treatments and orthopedics, for example as hip joint replacements. They are commonly made of titanium alloys and beyond the optimization of this established material, it is also essential to explore alternative implant materials in view of improved osseointegration. The aim of our study was to characterize the implant performance of zirconium in comparison to titanium implants. Zirconium implants have been characterized in a previous study concerning material properties and surface characteristics in vitro, such as oxide layer thickness and surface roughness. In the present study, we compare bone material quality around zirconium and titanium implants in terms of osseointegration and therefore characterized bone material properties in a rat model using a multi-method approach. We used light and electron microscopy, micro Raman spectroscopy, micro X-ray fluorescence and X-ray scattering techniques to investigate the osseointegration in terms of compositional and structural properties of the newly formed bone. Regarding the mineralization level, the mineral composition, and the alignment and order of the mineral particles, our results show that the maturity of the newly formed bone after 8 weeks of implantation is already very high. In conclusion, the bone material quality obtained for zirconium implants is at least as good as for titanium. It seems that the zirconium implants can be a good candidate for using as permanent metal prosthesis for orthopedic treatments.     

Osteoblast cell adhesion on a laser modified zirconia based bioceramic

Due to their attractive mechanical properties, bioinert zirconia bioceramics are frequently used in the high load-bearing sites such as orthopaedic and dental implants, but they are chemically inert and do not naturally form a direct bond with bone and thus do not provide osseointegration. A CO₂ laser was used to modify the surface properties with the aim to achieve osseointegration between bioinert zirconia and bone. The surface characterisation revealed that the surface roughness decreased and solidified microstructure occurred after laser treatment. Higher wettability characteristics generated by the CO₂ laser treatment was primarily due to the enhancement of the surface energy, particularly the polar component, determined by microstructural changes. An in vitro test using human fetal osteoblast cells (hFOB) revealed that osteoblast cells adhere better on the laser treated sample than the untreated sample. The change in the wettability characteristics could be the main mechanism governing the osteoblast cell adhesion on the YPSZ.     

Increased reactivity and in vitro cell response of titanium based implant surfaces after anodic oxidation

In the quest for improved bone growth and attachment around dental implants, chemical surface modifications are one possibility for future developments. The biological properties of titanium based materials can be further enhanced with methods like anodic polarization to produce an active rather than a passive titanium oxide surface. Here we investigate the formation of hydroxide groups on sand blasted and acid etched titanium and titanium–zirconium alloy surfaces after anodic polarization in an alkaline solution. X-ray photoelectron spectroscopy shows that the activated surfaces had increased reactivity. Furthermore the activated surfaces show up to threefold increase in OH^? concentration in comparison to the original surface. The surface parameters S_a, S_ku, S_dr and S_sk were more closely correlated to time and current density for titanium than for titanium–zirconium. Studies with MC3T3-E1 osteoblastic cells showed that OH^? activated surfaces increased mRNA levels of osteocalcin and collagen-I.     

<Emphasis Type="Italic">Streptococcus sanguinis</Emphasis> adhesion on titanium rough surfaces: effect of shot-blasting particles

Dental implant failure is commonly associated to dental plaque formation. This problem starts with bacterial colonization on implant surface upon implantation. Early colonizers (such as Streptococcus sanguinis) play a key role on that process, because they attach directly to the surface and facilitate adhesion of later colonizers. Surface treatments have been focused to improve osseointegration, where shot-blasting is one of the most used. However the effects on bacterial adhesion on that sort of surfaces have not been elucidated at all. A methodological procedure to test bacterial adherence to titanium shot-blasted surfaces (alumina and silicon carbide) by quantifying bacterial detached cells per area unit, was performed. In parallel, the surface properties of samples (i.e., roughness and surface energy), were analyzed in order to assess the relationship between surface treatment and bacterial adhesion. Rather than roughness, surface energy correlated to physicochemical properties of shot-blasted particles appears as critical factors for S. sanguinis adherence to titanium surfaces.     

The effects of early osseointegration in different implant sites in rabbit tibias

The aim of this study was to evaluate the early osseointegration of implants with the same surface treatment in different implant sites in rabbit tibias after 4 weeks. A total of 42 acid-etched implants were implanted in three different sites in the tibia: group A was 2.08 ± 0.18 mm below epiphyseal line; group B was 7.00 ± 0.61 mm below the epiphyseal line; group C was 13.01 ± 1.26 mm below the epiphyseal line. After 4 weeks, the average bone-to-implant contact (BIC) values were as follows: group A, 40.02 ± 4.82 %; group B, 28.20 ± 5.41 %; group C, 20.76 ± 3.10 %. The BIC measurements yielded statistically significant differences among group A, group B and group C (P < 0.01); group A demonstrated the best osseointegration. In the present study, the different implantation sites in the selected 20-mm area demonstrated different early osseointegration; the sites located 7 ± 1.5 mm below the epiphyseal line were best suited for observing the effectiveness of early osseointegration among the three sites. The statistical results of the early osseointegration of implants are therefore affected by the location of the implant sites in this 20-mm area.     

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

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