Dhuha.doc J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 18 Biomechanical evaluation of porous titanium implants (CpTi) fabricated by powder technology Dhuha Hussein Mohammed, B.D.S. (1) Widad A. H. Alnakkash, B.D.S., H.D.D., M.Sc. (2) ABSTRACT Background: It may be an important prospective clinical use of manufacturing of porous implant for clinical situations, such as cases of limitation in bone height, low bone density .The small segment of porous implant an effective osseointegration allows increasing in contact area provided for small segmented porous provided by its surface configuration. This study was done to Fabricate porous titanium implants by powder technology, as well as the observation of removal torque values of porous titanium implants compared to smooth titanium implants. Materials and methods: Twenty porous titanium implants (3.2mm in diameter and 8mm in length) were manufactured by powder technology using commercially pure titanium powder of ≤75um particles size, with polyvinyl alcohol powder of 212-300um particle size, as a space holder, by volume ratio (70:30) % respectively. The mixed powder was compacted using punch and die set -specially designed for this study –under 20 bar then sintering at 900 ºC by the use of argon gas. Twenty smooth titanium implants were prepared of (3.2mm in diameter and 8mm in length) by lathing of commercially pure titanium rod as a control group. The implants were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM), as well as estimation of porosity percentage. For each tibia of the 20 white New Zealand rabbits, one implant of each type (one porous in right, and the smooth in left tibia), were inserted through surgical procedure carried under serial condition. Mechanical test was performed to evaluate the bone- implant interface, after (2 and 6 weeks) healing periods . Results: Porous implants were obtained successfully by powder technology with 52% porosity and pore size 210um 17±. The porous implant showed significantly higher removal torque values when compared to smooth implants at the two different intervals of examination (2,6 weeks) , this proved to be statistically highly significant, also a highly significant difference was noticed for the means of the torque removal values in the same group at different implantation , with no evidence of clinical features of inflammatory reaction with both . Conclusions: Powder technology seemed to be particularly advantageous in fabrication of porous titanium. Porous implant show an increasing bone ingrowth compared with the smooth type represented by higher removal torque for both healing periods (2, 6) weeks . Key words: Porous titanium implant, powder technology, removal torque test. (J Bagh Coll Dentistry 2015; 27(1):18- 25). INTRODUCTION Lost body structures are replaced by surgical implants gaining the goals of becoming the most promising fields, improving quality of life with the increase in expectancy of population. The most commonly commercially biocompatible material used for the manufacturing of surgical implants are metals, with titanium being the most commonly used metals in the field of biomedicine presenting excellent physical and chemical properties there are two main groups of titanium according to manufacturing process the casting and powder technology (1,2). At present, however, the fabrication of Ti- based implants through the casting method is limited to a costly, multi-step process of vacuum melting machining, which is costly with the limited use the high melting temperature of Ti (3,4). The advantage of using powder technology (powder metallurgy is due to its processing route with limited cost (5). (1) Master student, Department of Prosthodontics, College of Dentistry, University of Baghdad. (2) Professor, Department of Prosthodontics, College of Dentistry, University of Baghdad. In powder technology pores can be found from removal of spacer particles with increasing porosity which is crucial for bone ingrowth. "Bone in growth", is the osseointegration gained by micromechanical interlocking between the bony tissues and porous structure of the implant which representing strong implant-bone bond thus increasing stability and preventing mobility. These pores can be interconnected three- dimensionally, which in turn provide enough space for the attachment and proliferation of new tissues thus facilitating the transport of body fluids (6,7) The applications of porous implants being ranged from spinal fixation to hip prostheses, osteosynthetic plates, and dental implants (8). MATERIALS AND METHODS Commercially available titanium powder particle size ≤75 um was used. Firstly PVA particles were milled using mill to powder then sieved using two sieves 212um and 300 um. PVA with average particle size (212-300 um) was used. Pilot study was done to find the best percentage for porous titanium implant five percentage were tested after mixing by volume J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 19 ratio(90:10) %, (80:20)%, (70:30)% , and (60:40)% (50: 50)% Titanium powder and PVA respectively. The (70:30) % Titanium-PVA was selected. The pressure of 20 bar was selected as the best amount of pressure to be applied. The condensation time of 60 seconds was selected. Sintering was performed by Carbolite Furnace using argon gas under 900 c. Preparation of samples for the tests by ultrasonic cleaning using: distilled water, acetone solution, ethanol solution, finally distilled water for 20, 20, 20, and 15 min, respectively (9). Two implants were placed in a single air tight plastic sheet (one implant from each group) then the implants were autoclaved at (121°C and 20 bar) for 30 minutes, as was performed by Xue XB et al. (10). Figure 1-a.stereomicroscope, (b, c implants as appearing under stereomicroscope) b .cylindrical compacted implant before sintering, c. cylindrical compacted after sintering Examine Implants SEM SEM and stereomicroscope images observation of the porous and smooth titanium samples was carried on to reveal the micrograph. X ray diffraction analysis Phase analysis was employed for CP-titanium powder and porous titanium samples using Shimadzu Lab XRD- 6000 Powder X-ray diffract meter and Cu Kα target radiation .The 20 angles were swept from 20- 80° in step of one degree each time Porosity test The density and porosity of the consolidated samples were measured using Archimedes (9)(11). Sample distribution before surgery 40 implants were placed into 20 rabbits and were divided into: a. Control group (smooth implant): This group includes 10 implants for each healing interval (2 and 6weeks) implanted in 10 rabbits. b. Experimental group (porous implant): This group includes 10 implants for each healing interval (2 and 6 weeks) implanted in 10 rabbits. Animals and surgical procedures Twenty New Zealand white rabbits of both sexes weighing 2-2.5 kg were used .The age of the animals was from 10-12 months. Animals were kept in standard separate cages and had free access to tap water, and were fed with standard pellets. They were left for 2weeks in the same environment before surgical operation. Antibiotic cover with ox tetracycline 20% (0.7ml/kg) intramuscular injection was given to exclude any infection (one dose/day, for 3 days). All instruments were autoclaved at 121 C ˚and 20 bars for 30 minutes. The required dose of anesthesia and antibiotic was calculated by weighing each rabbit in a special balance for the animals. Anesthesia was induced by intramuscular injection of ketamine hydrochloride 50 mg (1ml/kg body weight), Xylazine 20% (0.15ml/ kg body weight).and xylocaine 10% (1ml/ kg body weight). Surgery was performed under sterile condition and a gentle surgical technique. Incision was made on the medial side of the legs about (3cm) length to expose tibia bone. The skin, fascia the periosteum were carefully reflected. Drilling was done using round bur with intermittent pressure and continuous cooling with normal saline at rotary speed 1500 RPM and reduction torque 16.1. The enlargement of the hole was made gradually with spiral drill from 2.2 mm 2.9 mm till 3.1 mm The operation site was cleaned with copious amount of saline to remove bone shreds; the implants were removed from the plastic sheet and placed in holes with slight tapping pressure until 5mm was completely introduced into bone. Suturing of fascia was done with absorbable cat gut suture followed by skin suturing .The operation side was washed with normal saline followed by bandaging. Post-operative care, performed by giving an antibiotic (local and systemic) for 5 days after surgery. Torque removal test The animals that categorized for mechanical test were anesthetized with the same type and dose that used in the implantation procedure. Incision was made at the medial side of tibia; muscle and fascia were reflected to expose implants. J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 20 The stability of implant checked by the end of head of torque meter, Tibia was supported firmly while performing mechanical test to prevent any movement, which may have an affects on the accuracy of the test. A torque removal test was done by the torque meter to determine the peak torque necessary to loosen the implant from its bed, through the torque meter head manufactured for the measuring purpose of this study. RESULTS SEM observations 1. The SEM image observation of the porous titanium samples shows the surface morphology Fig. (2),(3). The pore space structure after space holder removal displays ragged shaped macro- pores inside the sintered material, where the number and the size of spaces can be evaluated. On the other hand a three-dimensional interconnected pores was clearly observed between the pores. Fig (3), (4). 2. The SEM observation of the smooth titanium samples Fig (5) Figure 2: SEM of porous titanium implant Figure 3: SEM of porous titanium sample showing the macropore Figure 4: SEM of porous titanium sample shows the interconnected pores X-ray Diffraction Phase Analysis The x-ray diffraction pattern of untreated commercially pure titanium powder and the sintered commercially pure titanium implants are shown in Fig (6). It is clearly obvious that the strongest peaks of powder were at (100) , (002) , (101) and(102) at 2Ө 35.20 , 38.48 , 40.27 ,and 53.08 respectively which could be indexed for αTitanium (JCPDS file 44.1294) . Figure 5: SEM illustrates topography of smooth titanium implant Figure 6: X-ray diffraction patterns of TI implant and TI powder J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 21 Also the pattern shows strong peaks of the sintered commercially pure titanium implants at (101), (101), (002), and (102) at 2Ө 40.23, 40.08, 38.18, and 53.23 respectively and this pattern is corresponding to the powder and responsible for αTitanium (JCPDS file 44.1294) Clinical observation All animals recovered well after surgery presenting clinically satisfactory postoperative results as an indication of good tolerance for the implantation procedure, with no clinical evidence of inflammation or infection at the surgical site Torque removal test The removal torque values of porous titanium implant after 2 weeks of implantation. Where at that interval, a higher torque values was needed to remove porous implants (mean value of 13.77 N.cm) compared to the torque value needed to remove smooth titanium implants (mean values of 8.27 N.cm ) (Figure 7). Figure 7: The removal torque mean values of the smooth and porous titanium implants after 2 weeks interval Descriptive statistics of removal torque values at 6 weeks after implantation, where higher torque force was required to remove the porous titanium implants (mean value of 18.79 N.cm) compared to that needed for smooth titanium implants (mean values of 13.55 N.cm) fig (8) Figure 8: The removal torque mean values of the smooth and porous titanium implants after 6 weeks interval Effect of time on removal torque value Both coating materials showed increased torque removal force between 2 and 6 weeks of implantation which was statistically highly significant. Figure 9 Figure 9: The summary of the differences in the torque mean values between all groups. Table (1) shows t-test for equality of means of torque values between porous and smooth titanium implants at 2 weeks healing period where showed a highly significant difference, also at 6 weeks as illustrated in (table 2) Table 1: t-test for equality of means of torque value for porous and smooth implants at 2 weeks interval Types of implant (at 2weeks ) t-test df Sig. (2-tailed) Sig Porous × smooth 15.77 18 .000 HS Table 2: t-test for equality of means of torque value for porous and smooth implants at 6 weeks interval Types of implant (at 6 weeks ) t-test df Sig. (2- tailed) Sig Porous × smooth 15.86 18 .000 HS T-test was performed for comparing the equality of means for the same group at the different implantation periods. A highly significant differences at p<0.010 between each subgroup of the two periods of examine times. It was clearly obvious that the torque value needed to remove implants from the bone was increased as healing period increased. Torque value N.cm Torque value N.cm Torque value N.cm J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 22 Table 3: t-test for equality of means of torque value within the same group at different time interval 2&6 weeks interval. Type of implants TIME in weeks N Mean S.D. T-test Sig. Porous 6 10 18.79 .77 14.617 HS 2 10 13.77 .84 Smooth 6 10 13.55 .70 17.234 HS 2 10 8.27 .71 S : Significant at P<0.05 DISCUSION Around the biomechanical area the resent use of powder technology is of great advantage for the final format of prosthesis production dense or porous and less expensive than the conventional (6,7,12). 1 Part One in Vitro Study 1.1 Selection of powder percentage and particles size The reason behind choosing the volume percentage of 30% PVA -70% titinuim powder, was because implant surface morphology is considered important for ossiointegration, since fibrin clot retention and bone progenerater cell migration are related to surface topography is associated . The use of large particle size for space holder (PVA), and fine particle size for ti, could be due to both a wider PVA particles distribution (which promotes a higher degree of interconnectivity of the pores) and a high average size of space-holder (>200um )which would fulfill the requirements to ensure the growth of bone into the implant (ingrowth); on the other hand, the choice of a titanium powder of small average size would improve the sinter ability of the compact (quality of the neck and lower grain size), helping to offset the loss of mechanical strength inherent in increased porosity. 1.2 Powder Compaction and problems associated with it: Punch and die set was designed in a way that ensure proper condensation of porous titanium implants .The powder / spacer material mixture was compacted using the hydraulic press with a pressure of 20 bar for 60 seconds, genuinely determined by trial and error in order to get the good quality for producing "green strength " that allowed enough handling strength. The pilot study showed that when powder / spacer material mixture was compacted at a pressure higher than 20bar with a holding time of more than 60 seconds, the compact became very hard with difficulty in ejecting the pellets from the mold and with a tendency to damage the punch .It was also noted in the pilot study that the compaction pressure should not be used when holding time less than 30 seconds. It could be understand that when the pressure is too high a considerable proportion of binder would be crushed during compaction this finding coincide with XB Xue et al. (10). While through the compaction of powder before sintering one can improve the mechanical properties (12,13). The loss of interconnectivity in between the powder particles may be caused by loose packing of powder mixture (14). Generally, higher compaction pressure increased the densification of the Ti powder. Heat treatment In sintering (thermal treatment ) the classic melting was substituted , and carried out below the melting point of the metal .In the pattern fig.(6)of the XRD phase analysis showed that in sintered titanium implants, heating was carried on using argon gas to provide a non oxidizing environment ; and this explained by in that the Ti and its alloys may have high affinity towards interstitial elements like oxygen and nitrogen required a non oxidizing environment thus reducing the residual surface oxide in order to improve the metallic contact between adjacent powder particles as stated by Gasser, Nyberg et al. and Ryan et al. and Nouri et al. (34,15,16).On the other hand conventional processing of molten metal to fabricate porous metal is suffering from limited part geometries, and limited control over the size, shape and distribution of porosities , contamination, costly, multi-step process (17). This in turn can confirmed that in particular, the casting method is unpractical for manufacturing of porous Ti based scaffolds, due to the high melting point and the high affinity of Ti towards oxygen and special refractory materials during the manufacturing process and these support the findings of Ryan et al. 15.These difficulties driven the researchers to a more cost affordable manufacturing methods with minimal waste product (3). Scanning Electron Microscope The SEM image observation of the porous titanium samples revealed the micrograph of the porous cylindrical implants upon the removal of the space holder (18). The pore-space structure in the sintered material contains different types of pores; Macro-pores, determined by the number and size of the space holder materials Fig (2, 3and4), also SEM images showed clearly, J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 23 interconnected pores. The average pore diameter was about 210μm (± 17), and 52% total porosity. This agreed with Elema et al. (19) who proposed that the pore size should range from 200 to 300 μm for bone tissue in growth in the porous samples; although they did their study about biodegradable porous polymeric implants. Small pores could favor hypoxia, which can result in the formation of osteocartilaginous tissue, while large richly vascularized pores permit direct osteogenesis and thus resulting in an improved bone implant interface (20).In addition to the presence of pores with more ragged and rough surfaces as seen in fig 3.5 offering larger surface area for bone ingrowth (21). Both the open porosity and pore interconnectivity are necessary for bone ingrowth, and extensive body fluid transport through the porous implants possible, thus trigger bone growth. It is also known that the pore size itself is less important than the amount of interconnectivity for new bone formation .This agrees with Chen et al. and Nouri et al. (22,23) with the difference in material and technique used . In the present study the observation of The SEM image can give a good indication of the packing of the powder mixture at a given sintering process. Porosity The porous structure of the alloys is important for the growth of bone inside the implant body and thus will improve the fixation and stability and the remodeling between the implant and the human tissue (24); by providing space for cell adhesion and permitting the transport of body fluids and thus leads to acceleration in the proliferation of new vasculature, while providing adequate mechanical properties to withstand stresses during surgical procedure and use (1). This agrees with Ryan et al. and vasconcellous et al. (6,15) but with the difference in material, method that used. The total porosity percentage of the fabricated porous implants after porosity test was within 52% as used in this study which could be an alternative for clinical use, for the reason that increased porosity may permit the growth into pores and subsequent mineralization. Many authors have been suggested that the percentage of pores preferable for Ti samples is between (25-66%). However, samples reaching till 80% porosity have also shown bone formation (25-27). On the other hand the percentage of the open porosity was 33% while the percentage of closed porosity was 19% .Pores are usually surrounded by pore walls and disconnected from each other in closed –cell porous implant structure, while in open-cell porous implant structure, pores are connected to each other, thus ensuring fixation of implants as new bone tissue grows and integrate into the this is in agreement with Banhart and Shehata Aly et al. (28,29). Part Two in Vivo Study Implant Preparation Prior to Surgery In this study the size of the holes created in the bone were (3.1mm)which was smaller than the diameter of the implant(3.2 mm) and this in turn would result in a better surgical fit, and as a consequence, force-fitting stress increases installation torque and initial stability and This agree with Skalak and Zhaoin and Waheed (30,31) with the differences in material, method, technique, and shape used in this study. Mechanical Test The removal torque value (RTV) is the torsion force required to remove an implant and this value represent the critical torque threshold where implant contact was destroyed. This would indirectly provide information about the amount of bone -implant contact for a given implant. Such testing was carried out on experimental animals model, where the rabbit tibia are the most frequently bone components cited in literatures Alnajar et al and Gonzalez et al. (32,33). The increase in the amount of cortical bone in contact with the implant required greater removal torque forces where the surface of the implant is often porous thus increasing bone/implant interface which consequently will increase the bony ingrowth into the surface irregularities of the implant (34). Tables (1 and 2) demonstrates t-test for equality means of the removal torque values of the porous titanium implants and the smooth titanium implants at the two implantation testing periods (2 and 6 weeks). It showed statistically highly significant difference; which indicates minimum removal torque values associated with smooth implants group, while the maximum removal torque values were associated with porous implants group thus suggesting that the pore structure for the porous implants provide more surface area and space for bone ingrowth as well as mechanical interlocking between the implant and bone. The surface area and contact surface configuration are important parameters for implant stability. When there is little or no mechanical interlocking between the implant surface and bone, any excessive loading may J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 24 cause rupture at the bone-implant interface . This mechanical interlock should enhance the strength of the bone- implant interface. As well as the force needed to extrude the bone through the porosities may be much higher than the bone mechanical strength itself. This agrees with Wazen et al. (35) with the difference in the material, method. Implant porosity promotes positive results in bone neoformation in vivo since it facilitates the transport of body fluids, aids in the spread of cells into the implant. Improving the implant stability over time is gained through increase in contact area between bone tissue and implant this in turn promoting the proliferation of bone tissue through a mechanism which is not usually observed on flat or rough surfaces ,on the other hand the process of osseointegration is accelerated as claimed by Bottino et al., Vanconcellos, Wazen et al. and Faria et al. (6-8, 35,36) with difference in the material , method technique and shape of implant used in this study. The removal torque method selected in this study is used for the first time shows the correlation between the force necessary for removal of the porous implants and the degree of bone implant integration and it focuses on interfacial shear properties. The amount of integration in RT method may be affected by implant geometry and topography as stated by Waheed and Alnajar (31,32) but on the other hand the material and the technique and shape are not the same and are used for the first time. Table (3) showed the result of t-test for equality for means of removal torque value within the same group at the different implantation periods shows a highly significant difference, which means that the minimum torque value was seen within 2 weeks of implantation periods, while the maximum value was observed in the 6 weeks implantation periods for both the porous and smooth groups. It was noticed in this study that the torque value significantly increased with time for both the porous and smooth implants .These results may suggest increased holding power and anchorage of implant with time due to progressive bone formation around the implant during healing period and consequently improved mechanical capacity due to maturation of bone with elapsed of time. REFERENCES 1. Rosa AL, Crippa GE, Oliveira PT, Taba MJ, Lefebvre LP, Beloti MM. Human alveolar bone cell proliferation, expression of osteoblastic phenotype, and matrix mineralization on porous titanium produced by powder metallurgy. Clin Oral Implant Res 2009 20: 472–81. 2. Bhattarai SR, Khalil KA, Dewidar M, Hwang PH, Yi HK, Kim HY. Novel production method and in-vitro cell compatibility of porous Ti-6Al-4V alloy disk for hard tissue engineering. J Biomed Mat Res A 2008; 86: 289-99. 3. Gasser B. Design and engineering criteria for titanium devices. In: Titanium in Medicine, Brunette, DM, Tengvall P, Textor M, Thomsen P. Springer; 2001. p.673-701. 4. Nyberg E, Miller M, Simmons K, Scott Weil, K. Microstructure and mechanical properties of titanium components fabricated by a new powder injection molding technique. Materials Science and Engineering C 2005a; 25: 336-42 5. Santos DR, Henriques VAR, Cairo CAA, Pereira MS. Production of a low young modulus titanium alloy by powder metallurgy. Mat Res 2005; 8: 439-42. 6. Vasconcellos LM, Leite DO, Nascimento FO, Vasconcellos LGO, Graça MLA, Carvalho YR, Cairo CAA. Porous titaniumfor biomedical applications - An experimental study on rabbits. Med Oralpatol oral Cir Bucal 2010, 2: E407-412. 7. Vasconcellos LM, Leite DO, Nascimento FO, Carvalho YR, Cairo CAA. Evaluation of bone ingrowth into porous titanium implant: histomorphometric analysis in rabbits. Braz Oral Res 2010b; 24: 399-405. 8. Bottino MC, Coelho PG, Yoshimoto M, König Jr B, Henriques VAR, Bressiani AHA, et al. Histomorphologic evaluation of Ti-13Nb-13Zr alloys processed via powder metallurgy. A study in rabbits. Mat Sci Engin 2008; 28: 223-7. 9. Xu J, Weng X-J, Wang X, Huang J-Z, Zhang C, et al. Potential use of porous titanium–niobium alloy in orthopedic implants: preparation and experimental study of its biocompatibility in vitro. PLoS One 2013; 19(8): e79289. 10. Xue XB, Zhao YY, Kearns V, Williams RL. Mechanical and Biological Properties of Titanium Synthetic Foams, supplemental proceeding; Vol. 2: Material characterization, compaction, modeling, and energy TMS (the mineral, metal & material society, 2010. p.129-35. 11. Al. Obaid, Inaam M. Physical and mechanical properties of alumina comp. pact. A master thesis, University of Technology, Department of Applied Science, 1999. 12. Esen Z, Bor S. Processing of titanium foams using magnesium spacer particles. Scripta Materialia 2007; 56: 341-4. 13. Dewidar M, Yoon HC, Lim JK. Mechanical properties of metals for biomedical applications using powder metallurgy process. Met Mat Int 2006; 12: 193-206. 14. Wen CE, et al, Processing of biocompatible porous Ti and Mg. Scripta Materialia 2001; 45: 1147-1153. 15. Ryan G, Pandit A, Apatsidis DP. Fabrication methods of porous metals for use in orthopaedic applications. Biomaterials 2006; 27: 2651-70 16. Nouri A, Li YC, Yamada Y, Hodgson PD, Wen CE. Effects of process control agent (PCA) on the microstructural and mechanical properties of Ti-Sn- Nb alloy prepared by mechanical alloying. World Congress on Powder Metallurgy and Particulate J Bagh College Dentistry Vol. 27(1), March 2015 Biomechanical evaluation Restorative Dentistry 25 Materials (PM 2008). Washington D.C., USA: 222- 233. 17. Krishna BV, Xue W, Bose S, Bandyopadhyay A. Engineered Porous Metals for Implants. JOM 2008; 60: 45-8. 18. Al-Ma'adhidi TMH. The significance of surface characteristics on Iraqi dental implants. A Ph.D. thesis, College of Dentistry, University of Baghdad, 2002. 19. Elema H, de Groot JH, Nijenhuis AJ, Pennings AJ, Veth RPH, Klompmaker J, et al. Biological evaluation of porous biodegradable polymer implants in menisci. Colloid and Polymer Science 1990; 268, 1082–88. 20. Frosch KH, Barvencik F, Lohmann CH, Viereck V, Siggelkow H, Breme J, Dresing K, Stürmer KM. Migration, matrix production and lamellar bone formation of human osteoblast-like cells in porous titanium implants. Cell Tis Org 2002; 170: 214-27. 21. Li H, Oppenheimer SM, Stupp SI, Dunand DC, Brinson LC. Effects of pore morphology and bone ingrowth on mechanical properties of microporous titanium as an orthopedic implant material. Materials Transactions 2004; 45: 1124- 31 22. Chen XB, Nouri A, Li YC, Hodgson PD, Wen CE. Effect of surface roughness of Ti, Zr, and TiZr on apatite precipitation from simulated body fluid. Biotechnology and Bioengineering 2008; 101: 378-87 23. Nouri A, Peter D, Hodgson, Cui'e Wen. Biomimetic Porous Titanium Scaffolds for Orthopedic and Dental Applications, Biomimetics Learning from Nature, Amitava Mukherjee (Ed.), ISBN: 978-953-307-025- 4, InTech, Available from: http://www. intechopen.com/books/biomimetics-learning-from- nature/ biomimetic-porous-titanium-scaffolds-for- orthopedic-and-dental applications. 24. Zhang YP, Li DS, Zhang XP. Gradient porosity and large pore size NiTi shape memory alloys. Scripta Materialia 2007; 57: 1020–3 25. Liu YL, Schoenaers J, Groot K, Wijn JR, Schepers E. Bone healing in porous implants: a histological and histometrical comparative study on sheep. J Mat Sci Mat Med 2000; 11: 711-7 26. Kujala S, Ryhänen J, Danilov A, Tuukkanen J. Effect of porosity on the osteointegration and bone ingrowth of a weight-bearing nickel-titanium bone graft substitute. Biomaterials 2003; 24: 4691-7. 27. Wen CE, Yamada Y, Shimojima K, Chino Y, Asahina T, Mabuchi M. Processing and mechanical properties of autogenous titanium implant materials. J Mat Sci Mat Med 2002; 13: 397-401. 28. Banhart J. Functional applications. In: Degischer HP, Kriszt B (eds.). Handbook of cellular metals: Production, Processing, Applications. Weinheim: Wiley-VCH Verlag; 2002. p. 313-320 29. Shehata Aly M, Bleck W, Scholz PF. How metal foams behave if the temperature rises. Metal Powder Report 2005; 60: 38-45 30. Skalak R, Zhao Y. Interaction of force-fitting and surface roughness of implants. Clin Implant Dent Rel Res 2000; 2: 219-24. 31. Waheed AS. Mechanical and histological evaluation of nanozirconium oxide coating on titanium alloy (Ti- 6Al-7Nb) dental implants. A master thesis, College of Dentistry, University of Baghdad, 2013. 32. Al-Najar SS. Mechanical and histological significance of Nigella sativa oil extract on bone implant interface. A master thesis, College of Dentistry, University of Baghdad, 2009. 33. Gonzalez P, Serra J, Liste S, Chiussi S, Leon B, Perez-Amor M, de Arellano-Lopez AR, Varela- Ferioa FM. New biomorphic ceramics coated with bioactive glass for biomedical applications. Biomaterial 2003; 24: 4827-32. 34. Clokie CM, Bell RC. Recombinant human transforming growth factor beta-1 and its effects on osseointegration. J Craniofac Surg 2003; 14(3): 268-77. 35. Wazen RM, Lefevre L-P, Baril E, Nanci .A Initial evaluation of bone ingrowth into a novel porous titanium coating. J Biomed Mat Res B: applied biomat 2010; 94: 64-71. 36. Faria PEP, Carvalho AL, Felipucci DNB, Wen C, Sennerby L, Salata LA. Bone formation following implantation of titanium sponge rods into humeral osteotomies in dogs: a histological and histometrical study. Clin Implant Dent Rel Res 2010; 12: 72-9. الخالصة ال السریري في حاالت محددة منھا عدم تمتع العظم بواصفات جیدة من حیث النوعیة أو االبعاد الكافیة الستقبال لتسھیل عملیة تصنیع غرسات مسامیة لالستعم:خلفیة الموضوع . ةحیث من الممكن للزرعات المسامیة ذات االبعاد الصغیرة ان تسمح بنمو عظمي فعال وذلك بسبب سعة المساحة السطحیة للتركیب المسامي للغرس.الغرسات لغرض ایجاد فعالیة وتاثیر مسامیة الغرسات ذات التركیب المسامي على تعزیز التماسك المیكانیكي بین العظم . المساحیقسات التیتانیوم المسامیة بطریقة تكنولوجیا تصنیع غر:االھداف . والزرعة 75≥باستخدام مسحوق التیتانیوم النقي التجاري بحجم حبیبي المساحیقورجیا بطریقة میتال)ملیمیتر طوال8-ملیمیتر قطرا 3.2(غرسة مسامیة بابعاد ) 20(تم تصنیع : المواد واالدوات بار في داخل قالب 20وتعبئتھا باستعمال ضغط , بالتعاقب %30:70كماسك للفراغ بنسبة حجمیة مئویة ) مایكرون 300-212(مایكرون مع مادة الكحول البولي الفنیلي بحجم حبیبي .مئویة باستعمال غاز االركون 900ثم معاملتھا حراریا بدرجة , صول على عینات مضغوطةاعد خصیصا لھذه الدراسة للح فحص : ومن ثم اجریت بعد ذلك الفحوص االتیة . الستعمالھا كمجموعة قیاسیة غیر معالجة ) ملیمیتر طوال 8-ملیمیتر قطرا 3.2(من مادة التیتانیوم النقي , غرسة ملساء 20حضرت .كما وتم فحص التركیب الدقیق للعینات باستخدام المجھر االلكتروني . السینیة للسطوح للغرسات المسامیة ومسحوق التیتانیوم النقي باالضافة لفحص المسامیة انحراف االشعة اجریت .واحدة في كل ساق ) غرسة مسامیة وغرسة ملساء (حیث استلم كل ارنب اثنین من الغرسات ,ارنبا من االرانب النیوزلندیة البیضاء مكانا للزراعة 20اختیر عظم الساق ل وزعت .اسابیع من مدة الشفاء ) 6و 2(العملیة الجراحیة تحت ظروف معقمة ومن ثم تم اجراء الفحوص المیكانیكیة لفھم طبییعة السطح البیني للعظم وغرسة االسنان بعد مضي . خصصت لفحص العزم الالزم لنزع الغرسة من العظم) مسامیة 20ملساء و 20(غرسة 40:الغرسات كاالتي مایكرون بطریقة تكنولوجیا المساحیق حیث اظھرت الغرسات المسامیة تفاعل اسرع مع ) 17 .±210(وبحجم مسامیي % 52تم انتاج غرسات اسنان ذات مسامیة تصل الى : النتائج فترتي االختبار وقد اظھرت نتائج العزم الالزم لنزع الغرسات المسامیة من العظم قیما اعلى احصائیا وبشكل واضح عند مقارنتھا مع الغرسات الملساء خال العظم من الغرسات الملساء من جھة اخرى الفحوص النسیجیة قد بینت بشكل .اسابیع كما انھ كانت ھناك نتائج اعلى للعزم الالزم لنزع الغرسة داخل كل مجموعة وبتناسب طردي مع طول فترة الشفاء ) 6و 2( .واضح تكون عظم جدید بمالصقة الغرسات باالضافة الى تحسین استجابة العظم للغرسات المسامیة بالمقارنة بالغرسات الملساء كما اظھرت الغرسات . وبسیطرة على نسبة المسامیة وحجم المسامات اظھرت تكنولوجیا المساحیق فائدة عملیة في تصنیع غرسات التیتانیوم المسامیة وذات مسامات متصلة : االستنتاج .المسامیة قیما اعلى للعزم الالزم لنزع الغرسات من العظم مقارنة بالغرسات الملساء ولكتا فترتي الشفاء