PROCESS FOR THE PREPARATION OF A TOPOGRAPHY FOR IMPROVED BLOOD COAGULATION AND/OR CELL ATTACHMENT ON A BODY MADE OF TITANIUM OR A TITANIUM ALLOY
20180147029 ยท 2018-05-31
Assignee
Inventors
Cpc classification
A61L27/50
HUMAN NECESSITIES
A61L2400/18
HUMAN NECESSITIES
International classification
A61C8/00
HUMAN NECESSITIES
A61L27/50
HUMAN NECESSITIES
Abstract
A process for the preparation of a topography for improved blood coagulation and/or cell attachment on a body made of titanium or a titanium alloy. The process includes the subsequent steps of: a) etching at least a portion of the surface of the body with a first etching solution including a mineral acid, and b) etching the surface etched under a) with a second etching solution different than the first etching solution, the second etching solution including hydrofluoric acid.
Claims
1. Process for the preparation of a topography for improved blood coagulation and/or cell attachment on a body made of titanium or a titanium alloy, wherein the process comprises the subsequent steps of a) etching at least a portion of the surface of the body with a first etching solution comprising a mineral acid, and b) etching the surface etched under a) with a second etching solution different than the first etching solution, said second etching solution comprising hydrofluoric acid.
2. Process according to claim 1, wherein by etching the surface according to step a) a microscopic topographical formation is formed, and by etching the surface according to step b) a sub-microscopic topographical formation is formed in the microscopic topographical formation.
3. Process according to claim 2, wherein the microscopic topographical formation is defined by at least one of the following surface parameters: i) Sa being the arithmetic mean deviation of the surface in three dimensions and being in the range from 0.1 ?m to 2.0 ?m; ii) St being the maximum peak to valley height of the profile in three dimensions and being in the range from 1.0 ?m to 20.0 ?m; and/or iii) Ssk being the skewness of the profile in three dimensions and being in the range from ?0.6 to 1.0.
4. Process according to claim 2, wherein by the sub-microscopic topographical formation formed in step b), at least one surface parameter defining the microscopic topographical formation formed in step a) and being selected from the group consisting of Sa, St and Ssk is changed by 50% at most.
5. Process according to claim 2, wherein the sub-microscopic topographical formation comprises or essentially consists of sub-microscopic structures which extend in at least two dimensions to 1000 nm at most.
6. Process according to claim 1, further comprising the step of providing a macroscopic topographical formation to the surface prior to step a).
7. Process according to claim 1, wherein the body is made of a titanium-zirconium alloy.
8. Process according to claim 1, wherein the concentration of hydrofluoric acid in the second etching solution is in the range from 0.01 vol.-% to 4 vol.-%.
9. Process according to claim 1, wherein the treatment under step b) is carried out for a duration in the range from 0.1 minute to 30 minutes.
10. Process according to claim 1, wherein the treatment under step b) is carried out at a temperature in the range from 10? C. to 90? C.
11. Process according to claim 1, wherein the first etching solution comprises or essentially consists of a mixture of HCl and H.sub.2SO.sub.4.
12. Process according to claim 1, wherein the body is a dental implant or a dental implant abutment and the topography is provided on at least a portion of the surface of the body that in use is intended to be in contact with bone tissue or soft tissue, respectively.
13. Body obtainable by the process according to claim 1.
14. Body according to claim 13, the surface of which being defined by a microscopic topographical formation and by a sub-microscopic topographical formation formed in the microscopic topographical formation.
15. Body according to claim 14, wherein the microscopic topographical formation is defined by at least one of the following surface parameters: i) Sa being the arithmetic mean deviation of the surface in three dimensions and being in the range from 0.1 ?m to 2.0 ?m; ii) St being the maximum peak to valley height of the profile in three dimensions and being in the range from 1.0 ?m to 20.0 ?m, and/or iii) Ssk being the skewness of the profile in three dimensions and being in the range from ?0.6 to 1.0.
16. Body according to claim 14, wherein the sub-microscopic topographical formation comprises or consists of sub-microscopic structures which extend in at least two dimensions to 1000 nm at most.
17. Body according to claim 16, wherein at least some of the sub-microscopic structures have a shape with at least one straight-line edge, and are sharp-edged and/or jagged.
18. A method comprising applying the body according to claim 13 for a dental implant or a dental implant abutment.
Description
EXAMPLES
1. Examples Relating to In Vitro-Analysis
[0072] 1.1. Materials and Methods
Material
[0073] Discs, 5 mm in diameter and 1 mm in thickness, were prepared from a bimetallic TiZr alloy rod (Roxolid (RXD); 13-17% Zr).
SLA Treatment
[0074] First, the samples have been treated according to the protocol for preparing SLA? samples. Specifically, the samples have been sand-blasted using corundum with large grits (particle size 250-500 ?m), followed by etching the sand-blasted surface in a boiling mixture of HCl and H.sub.2SO.sub.4.
Samples RXD SLA HF and RXD SLActive HF
[0075] A first portion of the samples achieved by the SLA? treatment (involving step a) of the process of the present invention) has then been treated in an aqueous solution comprising 0.2% hydrofluoric acid (volumes for 100 ml: 0.5 ml 40% HF, 99.5 ml H.sub.2O) for 2 minutes (corresponding to step b) of the process) at room temperature.
[0076] The samples have then been rinsed in ultrapure water by placing a Teflon beaker containing the samples in 400 ml ultrapure water and subjecting the samples to ultra-sonication three times (1 minute each in approximately 20 ml ultrapure water). The samples have then been blown dry in a stream of argon and stored dry in aluminium foil.
[0077] Thereby, samples RXD SLA HF according to the present invention have been achieved.
[0078] Further, samples RXD SLActive HF have been prepared, which will be discussed in the context of the assessment of the fibrin network formation. Specifically, these samples have been prepared in analogy to the RXD SLA HF described above, but with the difference that instead of storing the dried samples in air, storage was carried out in 0.9% NaCl solution (pH of approximately 5) in a vial used for the commercially available SLActive? implants.
Samples RXD SLActive
[0079] For comparative purposes, a second portion of the samples achieved by the SLA? treatment has been directly immersed and stored in 0.9% NaCl solution, according to the SLActive? protocol, whereby comparative samples RXD SLActive have been achieved.
Storage and Sterilization
[0080] All samples were stored for a minimum duration of 2 months.
[0081] Both the RXD SLA HF and the RXD SLActive samples were ?(gamma)-sterilized (25-42 kGy) before analysing their surface according to the evaluation methods described in the following. Comparison experiments conducted on discs before and after sterilization showed no indication of an influence of the ?(gamma)-sterilization on the results obtained by the following evaluation methods.
[0082] 1.2. Evaluation Methods
[0083] 1.2.1. Contact Angle Measurements
[0084] Contact angle measurements were performed in order to determine the degree of hydrophilicity or hydrophobicity. For RXD SLA HF and RXD SLActive, three sample discs were analysed.
[0085] The contact angles were determined using a sessile drop test with ultrapure water (EasyDrop DSA20E, Kr?ss GmbH). A droplet size of 0.3 ?l (microliter) was chosen for the RXD SLA HF samples (i.e. the samples stored dry) and 0.1 ?l (microliter) for the RXD SLActive samples (i.e. the samples stored in saline solution). The RXD SLActive samples were blown dry in a stream of Ar prior to the contact angle measurements. The RXD SLA HF samples were measured as received. Contact angles were calculated by fitting a circular segment function to the contour of the droplet on the surface.
[0086] The results of the contact angle measurements are given in Table 1a.
TABLE-US-00001 TABLE 1a Contact angles (first set of results) Std disc 1 disc 2 disc 3 mean CA CA [?] CA [?] CA [?] CA [?] [?] RXD 134.3 139.6 134.6 136.2 3.0 SLA HF RXD 0 0 0 0 SLActive
[0087] As shown in Table 1a, all RXD SLA HF discs were hydrophobic exhibiting a contact angle of about 135? when contacted with pure water, whereas the RXD SLActive discs were hydrophilic showing complete wetting with water.
[0088] In further experiments, also RXD SLActive HF samples were assessed for their contact angles, the results of which are shown in Table 1b.
TABLE-US-00002 TABLE 1b Contact angles (second set of results) disc 1 disc 2 disc 3 mean Std CA [?] CA [?] CA [?] CA [?] CA [?] RXD SLA HF 140.7 138.2 135.8 138.2 2.5 RXD SLActive 0.0 0.0 0.0 0.0 RXD SLActive HF 0.0 0.0 0.0 0.0
[0089] These results confirm the previous findings regarding RXD SLA HF and RXD SLActive samples, and further show complete wetting of the RXD SLActive HF samples, the surface of which can therefore be regarded as superhydrophilic within the above mentioned definition, as it is also the case for the surface of the RXD SLActive samples. Thus, the sub-microscopic structures according to the present invention did not have any negative impact on the hydrophilicity of the surface on which they are formed.
[0090] 1.2.2. SEM (Scanning Electron Microscopy)
[0091] The visual appearance and morphology of the nanostructures were evaluated using scanning electron microscopy (SEM).
[0092] SEM measurements were performed on three discs for each type of surface. The measurements were performed on a scanning electron microscope of the type Zeiss Supra 55. The overview SEM images were acquired with an acceleration voltage of 20 kV using the Everhart-Thornley detector and the high-resolution images with an acceleration voltage of 5 kV using the in-lens detector.
[0093] The SEM images of the samples are given in the attached figures, whereby
[0094]
[0095]
[0096]
[0097]
[0098]
[0099]
[0100] As can be seen from
[0101] However, there are distinct differences in the appearance of a sub-microscopic topographical formation. Specifically, sub-microscopic structures are formed by subtractive process step b), i.e. by the etching using an etching solution comprising HF.
[0102] The sub-microscopic structures have a shape with at least one straight-line edge, and more particularly are sharp-edged or even jagged, as can in particular be seen from
[0103] Also, similar structures were obtained if an SLA? or an SLActive? surface was taken as a starting point, as shown by
[0104] The sub-microscopic structures formed by the process of the present invention including subtractive process step b) are both in size and shape completely different from the nanostructures on the RXD SLActive samples, which are formed according to the technology described in WO2013/056844 and thus are formed by a gradual growing or building up over time.
[0105] 1.2.3. Roughness Parameter Determination
[0106] Roughness images were acquired using a confocal microscope (psurf explorer, NanoFocus AG, Oberhausen, Germany) equipped with a 20? lens. Three measurements were performed on each sample disc and three discs were measured for each type of surface. The roughness parameters were calculated using the WinSAM software mentioned above. The whole roughness image with a size of 798 ?m (micrometer)?798 ?m (micrometer) was used for the calculation of the 3D roughness parameters.
[0107] The values of the microscopic topographical formation (roughness) were determined using a moving average Gaussian filter with a cut-off wavelength of 30 ?m (x=31 ?m, y=30 ?m, 20?19 image points). Then, the roughness values were calculated by means of a KFL analysis with limits from the amplitude density.
[0108] Specifically, S.sub.a (the arithmetic mean deviation of the surface in three dimensions), S.sub.t (the maximum peak to valley height of the profile in three dimensions) and S.sub.sk (the skewness) were determined in analogy to EN ISO 4287 relating to the respective parameters R.sub.a, R.sub.t and R.sub.sk in two dimensions. For the parameters in three dimensions, it is further referred to ISO 25178, in which the symbol S.sub.z is used for the maximum peak to valley height of the profile (instead of the symbol S.sub.t used in the context of the present invention).
[0109] Table 2a presents the mean values of the microroughness values of the two samples. The table shows that at least the values of S.sub.a and S.sub.t of both RXD SLActive and RXD SLA HF lie within the same range typically observed for SLA?/SLActive? implants. Specifically, the S.sub.a and S.sub.t values of RXD SLA HF deviate from the respective values of the RXD SLActive samples by less than 15%.
TABLE-US-00003 TABLE 2a Values of the microscopic topographical formation (first set of results) Sa Std Sa St Std St Std [?m] [?m] [?m] [?m] Ssk Ssk RXD SLA HF 1.080 0.024 6.81 0.13 0.261 0.037 RXD SLActive 0.970 0.046 6.38 0.26 0.192 0.051
[0110] In further experiments, also RXD SLActive HF samples were assessed for the microscopic topographical formation formed thereon, the results of which (apart from the ones for RXD SLA HF and RXD SLActive) are shown in Table 2b.
TABLE-US-00004 TABLE 2b Values of the microscopic topographical formation (second set of results) Sa Std Sa St Std St Std [?m] [?m] [?m] [?m] Ssk Ssk RXD SLA HF 1.065 0.046 7.56 0.42 0.270 0.035 RXD SLActive 1.068 0.020 7.00 0.16 0.181 0.047 RXD SLActive HF 1.048 0.029 7.40 0.14 0.286 0.026
[0111] These results confirm the previous findings regarding RXD SLA HF and RXD SLActive samples and further show only a slight deviation of the topography parameters determined for RXD SLActive HF samples in comparison to the ones determined for RXD SLActive. Specifically, a deviation of the S.sub.a and S.sub.t values of less than 15% was found for the RXD SLActive HF samples in comparison to the RXD SLActive samples.
[0112] 1.2.4. Protein Adsorption Measurements
[0113] Albumin (from bovine serum (BSA), Alexa Fluor 647 conjugate, Invitrogen, USA), fibrinogen (from human plasma; HPF, Alexa Fluor 546 conjugate, Invitrogen, USA) and fibronectin (Rhodamine Fibronectin from bovine plasma; BSF, Cytoskeleton, Inc., USA) were used as model proteins to study their adsorption (or adherence) behaviour on the different surfaces by means of fluorescence microscopy using a fluorescence scanner.
[0114] Stock solutions of 0.5 mg/ml albumin and 0.5 mg/ml fibrinogen have been made according to the product manuals. For storage these stock solutions were divided into 0.5 ml aliquots and frozen at ?20? C. Fibronectin solutions were made directly from the 20 ?g vials, without making a stock solution.
[0115] All protein-adsorption solutions were made with HEPES 2 buffer prepared with 10 mM 4-(2-hydroxylethyl)-piperazine-1-ethanesulfonic acid (HEPES) and 150 mM NaCl with pH 7.4. Prior to use the HEPES 2 buffer was filtered (Whatman FP 30/0.2 CA-S, size 0.2 ?m, maximum pressure 7 bar).
[0116] For low protein concentration experiments, the protein solution consisted of filtered HEPES 2 and fluorescently labelled protein of defined concentration (see Table 3 below). For high concentration experiments, unlabelled protein was added additionally to simulate the real protein concentration in human blood (Table 3). To enhance the solubility of unlabelled proteins, HEPES 2 was heated to 37? C. (water bath, INCO 2/108, Memmert GmbH&Co, Germany) prior to the preparation of the solution. The different proteins were tested separately; therefore, the prepared protein solutions always contained only one type of protein. It is assumed that the labelled proteins behave like the unlabelled ones.
[0117] To reduce a possible uncertainty in the results due to the instability of the fluorescence marker, the protein solution was freshly prepared right before the adsorption experiments.
[0118] The method applied was based on the application of fluorescently labelled proteins and intensity measurements as well as comparison of fluorescence scanning images.
[0119] For the albumin and fibrinogen experiments, the samples were generally immersed into 2 ml of protein solution for 10 minutes. The adsorption process was carried out in 24-well plates. Experiments with fibronectin were carried out in 96-well plates and 0.3 ml protein solution but also with an adsorption time of 10 minutes. All adsorption experiments were performed at room temperature.
[0120] Proteins not adsorbed onto the surface were removed by submerging the samples in 2 ml of pure HEPES 2 for 10 seconds. Next, they were pivoted in 5 ml of HEPES 2 for 5 seconds followed by a rinsing step with the same 5 ml of HEPES 2. Additionally, the samples were rinsed with ultrapure water for 3 seconds, dried in a stream of nitrogen (at a pressure of about 1 bar) and stored at room temperature in a 24-well plate. To avoid bleaching of the fluorescent label of the adsorbed proteins, the well plates were covered with aluminium foil.
[0121] The experimental conditions are given in Table 3 below:
TABLE-US-00005 TABLE 3 Experimental conditions of protein adsorption experiments Protein Protein Concentration solution Time Samples low protein concentration Albumin 3 ?g/mL 2 mL 10 min 6 Fibrinogen 7 ?g/mL 2 mL 10 min 6 Fibronectin 3 ?g/mL 0.3 mL 10 min 6 high protein concentration Albumin 3 ?g/mL + 10 mg/mL* 2 mL 10 min 6 Fibrinogen 7 ?g/mL + 1 mg/mL* 2 mL 10 min 6 Fibronectin 3 ?g/mL + 0.2 mg/mL* 0.3 mL 10 min 6 *= unlabelled protein
[0122] The amount of protein attached to the surface was measured qualitatively using a microarray fluorescence scanner (Axon Genepix 4200A, Molecular Devices, USA). For intensity measurements, the resolution was set to 100 ?m/pixel and only one scan per line was performed. For imaging the resolution was set to 5 ?m/pixel and three scans per line were performed. To read out the albumin adsorption a laser with a wavelength of 635 nm was used whereas the scanning of fibrinogen and fibronectin adsorbed surfaces was performed using a 532 nm laser. The best focus position was determined separately for every sample.
[0123] The photo-multiplier tube (PMT) of the fluorescence scanner was specified to be linear between a gain of 350 to 600. For that reason, all scans were performed in this PMT range. The gain was adapted for each combination of surface, protein and concentration in order to stay in the grey-scale limits of the fluorescence signal of a sample. All gains chosen are listed in Table 4.
TABLE-US-00006 TABLE 4 Gains chosen for every batch of samples to measure the protein adsorption RXD SLActive RXD SLA HF low protein concentration Albumin 400 600 Fibrinogen 450 650 Fibronectin 500 600 high protein concentration Albumin 600 600 Fibrinogen 550 550 Fibronectin 550 600
[0124] To evaluate the homogeneity of the protein adsorption, high-resolution images were compared with each other by visual examination.
[0125] The fluorescence intensity data acquired by fluorescence scanning are given in the attached
[0126]
[0127]
[0128] All values presented in
[0129] According to
[0130] At high protein concentration, a very selective adsorption of fibrinogen was determined for the RXD SLA HF according to the present invention with an intensity comparable to the one of fibrinogen adsorbed on well-established Ti SLActive, as shown in
[0131] 1.2.5. Assessment of Fibrin Network Formation after Whole Human Blood Incubation
[0132] RXD SLActive HF samples were incubated with whole human blood and analysed for fibrin network formation by SEM and CLSM (confocal laser scanning microscopy) imaging.
[0133] Specifically, whole human blood obtained from healthy volunteers was partially heparinized directly with 3 IU/ml sodium heparin (final concentration 0.5 IU heparin/ml blood) and used for the experiments within 1 hour after withdrawal.
[0134] Samples were placed into a sample holder and freshly withdrawn blood was added until all samples were covered with a 4 mm thick layer of blood. To prevent further contact with air, the sample holder was closed with a lid and sealed with parafilm before incubation on a tumbling shaker at 10 rpm at room temperature.
[0135] The incubation time was determined for each experiment individually. For this, whole blood was spiked with labeled fibrinogen (Alexa488), which allows live monitoring of the blood coagulation on the samples using the fluorescence microscope. As reference, the samples RXD SLActive (and RXD SLA) were used and two time points were chosen (t1: thin, t2: thick fibrin network present on the reference sample).
[0136] After incubation, blood was removed and the samples were washed three times by adding pre-warmed PBS into the sample holder, then incubated on a tumbling shaker at 10 rpm for 1 minute for each washing step. Thereafter, the samples were transferred into a new 96-well plate for further treatment.
[0137] For SEM imaging, samples were fixed in modified Karnovsky solution for 1 h at room temperature (RT) and then washed twice in PBS. Thereafter the samples were dehydrated by immersing the samples in solutions of a gradient series of ethanol (50, 70, 80, 90 and 100%), followed by incubation in hexamethyldisilazane (HMDS) for 30 min. Finally, samples were placed into a new 96-well plate and dried overnight at RT. On the next day samples were sputter-coated with gold/palladium (high vacuum coater Leica EM ACE 600, Switzerland). SEM imaging was performed using a Hitachi S-4800 (Hitachi High-Technologies, Canada) at an accelerating voltage of 2 kV and 10 ?A current flows.
[0138] For CLSM analysis, samples were incubated for 30 min in PBS with 5% goat serum and 1% FCS before staining platelets with Alexa546-labeled phalloidin for 1 h at RT. The platelets and the fibrin network (visible due to spiking of the blood with Alexa488-labeled fibrinogen) were imaged with the CLSM (10?, 40? magnification). Depending on the coverage and thickness of the fibrin network seen by SEM imaging, only one time point (t1 or t2) was imaged. On samples showing complete coverage with fibrin on the surface, the thickness of the fibrin network was measured from z-stack images. To assess the thickness of the fibrin network, 4 z-stack images of 2 samples (2 images per sample with 4 to 6 measurements per image) were analysed to measure the distance from the sample surface to the top surface of the fibrin network using the measure function of the Zeiss ZEN software. CLSM analysis was performed with three independent experiments.
[0139] The semi-quantitative analysis of the SEM imaging revealed a trend for higher fibrin network thickness and larger sample coverage of the RXD SLActive HF sample in comparison to the RXD SLActive sample.
[0140] This is evidenced by the following figures, of which
[0141]
[0142]
[0143] Evaluating the presence, distribution and thickness of the fibrin network, the semi-quantitative analysis of the SEM images is summarized in Table 5 showing for four different experiments the value of a qualitative ranking from 0 to 4 taken in each case for two samples and for two different incubation periods given in the table, the ranking starting from patches of blood cells with only few visible fibrin fibers (0) to thick fibrin networks completely covering the sample surface (4).
TABLE-US-00007 TABLE 5 Semi-quantitative analysis of the SEM images for four different experiments performed on RXD SLActive HF and RXD SLActive samples Incubation period RXD RXD Experiment (min) SLActive HF SLActive 1 10 1 2 1.5 1.5 15 2 4 2 4 2 12 1.5 1.5 1 n.d. 15 3.5 2 0.5 1 3 14 3 3 0.5 1 17 4 2.5 4 2 4 15 4 4 4 4 18 4 4 2 1.5
[0144] The thickness of fibrin formed on samples incubated with whole blood (partially heparinized 0.5 IU/ml) for 15 minutes and 17 minutes, respectively, has been assessed as described above, the results of which are given in Table 6.
TABLE-US-00008 TABLE 6 Analysis of fibrin layer thickness of RXD SLActive HF and RXD SLActive samples 15 minutes incubation 17 minutes incubation fibrin thickness fibrin thickness Sample layer [?m] layer [?m] RXD homogenous 16.93 homogenous/ 14.29 SLActive HF spots RXD homogenous 13.97 homogenous 9.86 SLActive
[0145] Thus, higher fibrin thickness was determined on the samples according to the present invention than on the comparative samples.
2. Examples Relating to In Vivo-Analysis
[0146] Biomechanical studies in rabbits were performed to investigate the influence of the surface topography on the osseointegration. The attachment between bone and implant was directly assessed by pull-out tests.
[0147] 2.1. Materials and Methods
[0148] Additionally, biomechanical studies in rabbits were performed to investigate the osseointegration of titanium implant discs in vivo. For these additional studies, discs were prepared as described for the in-vitro experiments, but using Roxolid discs with 6.2 mm in diameter and 2 mm in thickness. The respective samples are in the following referred to as RXD SLA HF II.
[0149] 2.2. Characterization of the Surface of the Samples
[0150] The samples were analysed using the above described procedures for contact angle measurement and roughness parameter determination.
[0151] Regarding contact angle measurement, a mean value of 123.2? was measured for RXD SLA HF II.
[0152] Roughness parameter determination produced the results given in Table 7.
TABLE-US-00009 TABLE 7 Roughness values of the microscopic topographical formation of the RXD SLA HF II samples of the in vivo study Sa Std Sa St Std St Std [?m] [?m] [?m] [?m] Ssk Ssk RXD SLA HF II 1.204 0.069 8.17 0.42 0.306 0.031
[0153] The results given in Table 7 confirm the findings obtained above, namely that at least the values of S.sub.a and S.sub.t of RXD SLA HF II lie within the same range typically observed for SLA?/SLActive? implants. Also, with regard to the samples of the in vivo study, the S.sub.a, S.sub.t and S.sub.sk are only unsubstantially changed by process step b), i.e. the formation of the sub-microscopic topographical formation.
[0154] 2.3. Biomechanical Pull-Out Measurements
[0155] As mentioned above, pull-out studies were performed in rabbits. To this end, rabbits were sedated and, during standard surgical procedures, received two disc-implants per tibia, i.e. four implants in total per rabbit.
[0156] The implants were provided with a Teflon cap to protect them from bone overgrowth and were stabilized with a pre-shaped titanium band, retained in the cortical bone with two titanium screws. After the implant procedures, the soft tissue layers were repositioned and the wound closed using a resorbable suture.
[0157] Bone-implant attachments were tested 4 weeks after implantation.
[0158] Detailed information concerning the surgery procedure as well as the pull-out test description has already been published elsewhere by Remold and Ellingsen (Biomaterials 23 (2002) 2201) and Monjo et al. (Monjo et al., Biomaterials 29 (2008) 3771).
[0159] Table 8 gives the measured pull-out-force in [N] after 4 weeks of implantation.
TABLE-US-00010 TABLE 8 Pull-out-force after 4 weeks of implantation Mean Pull- Out-Force [N] Std Median RXD SLA 50.3 23.32 50.9 HF II
[0160] As can be clearly seen from the Table 8, a very high pull-out-force was determined for RXD SLA HF prepared according to the present invention. Given the relatively high hydrophobicity of the surface of RXD SLA HF, this result is most surprising and emphasizes the relevance of the sub-microscopic topographical formation achieved in subtractive process step b) of the present invention.