IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 The Corrosion Behavior of Different Gauges of Stainless Steel Wire Use in Removable Partial Denture and Orthodontics Appliances N. S. Mansoor Foundation of Technical Education,College of Health and Medical Technology Abstract Wires are commonly used for the construction of orthodontic appliances and occasionally as wrought clasps and rests on partial dentures. The corrosion resistance is the most important properties of dental alloy. Corrosion process reported to cause a numerous adverse effects on both living tissue and restoration .The conditions in the mouth are very suitable for the occurrence of corrosion. The main objective of this study was to evaluate the corrosion behavior of different gauges of stainless steel wire in artificial saliva .Four gauges of dental stainless steel wire used in orthodontic and removable partial denture were used in this study 0.6mm.,0.7mm.,0 .8mm.&1.0mm.).The specimens were divided according to gauge in to four groups(A,B,C,&D ) ,ten specimens in each group .Each wire was cut by using wire cutter to get wire with (1cm) in length .Artificial saliva of Fusayama Meyer type was used as the testing solution .Sensitive electronic balance was used to weight the sample before immersion in solution and recording the results.This this represents the first weight(W1).Each specimen was put inside a test tube , and held using dental floss in a way that the specimen was fully immersed in the solution from all sides . The specimens then were put inside an incubator ,which was adjusted at 37±2 and left for 14 days .At the end of immersion period ; the specimens were removed from the solution and then allowed to dry and were balanced then the results were recorded .This represents the second weight (W2) .After obtaining the (W1)&(W2) the corrosion rate was calculated . The results before and after immersion showed that the 0.6 mm.& 0.7mm stainless steel wire gave the highest and more corrosion resistance value than 0.8mm&1.0mm.stainless steel wire . The result showed there is a statistical significance between (W1&W2) of 0.8mm stainless steel wire and highly significant between (W1&W2) of 1.0mm. stainless steel wire . The comparison of the results after calculating results in corrosion rate formula showed that the 1.0mm stainless steel wire more corrosion resistance followed by 0.8mm wire ,from 0.6mm& 0.7 mm wire . Introduction Wires are used by the orthodontist and are some times used for clasps in connection with partial dentures. Until the 1930 the only orthodontic wires available were made of gold and austenitic stainless steel with greater strength. [1] Various wire sizes and four arch wire alloys are now available stainless steel, cobalt, chromium, nickel titanium and beta titanium. The ideal orthodontic wire properties can be described in layer terms of the following criteria ,but in contemporary practice ,no one wire meets all these requirements , and the best result is obtained by using specific wire for IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 specific purpose ,the criteria are : strong ,resilience , weld able , solder able ,low cost , low friction ,and bio compatibility .[2] There are essentially three types of stainless steels. This classification is with approximate compositions. The type includes: ferrite stainless steel, martenstic stainless steel &austenitic stainless steel. [1] Bio compatibility and corrosion resistance of alloys were related to the composition and elements or irons related in to surrounding medium. [3] The corrosion resistance is of great importance because of possible biological reaction (adverse effects on both living tissues) and because of possible destruction of the restoration [4, 5] and lead to roughening of the surface, weakening of the appliances, and liberation of elements from the metal or alloy [6].Release of elements can produce discoloration of adjacent soft tissues and allergic reactions in susceptible patients [7].Corrosion can severely limit the fatigue life and ultimate strength of the material leading to mechanical failure of the dental materials .[8] Corrosion products were implicated in causing local pain or swelling in the region of the orthodontic appliances in the absence of infection, which can lead to secondary infection. [9] This study aims to investigate the corrosion behavior of stainless steel wire with different gauge in artificial saliva. Materials and Methods Materials, Instruments & Equipments: * Distilled water (Iraq) * NaCl, KCl, CaCl2, 2H2O, NaH2PO4& urea crystal (artificial saliva of Fusayama, Meyer type) *Dental stainless steel wire with different gauge 0.6 mm, 0.7 mm, 0.8 mm & 1.0 mm . (china). fig (1) *Acetone material * Cotton * Dental floss * Sodium bicarbonate & nitric acid. Instrument & Equipments:-  Sensitive electronic balance (Germany)  Incubator (England )  Millimeter ruler  Wire cutter  Electronic pH meter (Japan)  Tubes (testing tube & measuring tube)  Olympus photomicroscope system with exposure control unites (Japan). Methods Four gauges of dental stainless steel wire used in orthodontic & removable partial denture were used in this study, (0.6 mm, 0.7 mm, 0.8 mm & 1.0 mm). The specimens were divided according to gauge into four groups, (A, B, C &D) ten specimens in each group.fig (2) Dental stainless steel wire with different gauge (diameter) were used in this study 0.6 mm , 0.7 mm , 0.8 mm , &1.0 mm ) that using in removable orthodontic & removable partial denture fig (1).Each wire was cut by used wire cutter to get wire with 1 cm in length (used ruler to measure the length of wire).fig (3) The finished were rinsed in distilled water to remove any attached particles, and then allowed to dry in air .The specimen then were immersed in an acetone solution for about (5 minutes) in order to remove any adsorbed particles, and then allowed to dry in air. fig (4) IHJPAS Sensitive Electronic balance was used to weight the samples before immersion in solution & recording the results .This represented the first weight (w1). Preparation of the testing solution Artificial saliva of Fusayama- Meyer type was used as the testing solution [10] .The composition of artificial saliva mentioned in table (1). An electronic balance was used to prepare the required amounts of each element of artificial saliva which were mixed in one liter of distilled water. The pH of the solution is adjusted at (pH=6) by using sodium bicarbonate .This stimulates the pH of natural saliva. The pH of the solution was estimated by using an electronic meter. So 2ml of nitric acid (normality = 6) was added to each sample solution in order to increase the dissolution of the ions in the solution.Each specimen was put inside a test tube, and held using a dental floss in way that the specimen was fully immersed in the solution from all sides. In each test tube 30 ml of the testing solution and then the test tubes were locked, the artificial saliva was prepared as described in table (1). The specimen then were put inside incubator which was adjusted at 37 C ◦ ± 2 and left for 14 days [11] the solutions were shaked for about (5 seconds ) daily in order to prevent the solution from being precipitated. At the end of the immersion period, the specimen were removed from the solution &then allowed to dry & were balanced then the result was recorded .This represented the second weight (w2). The corrosion rate calculated by the following formula: [12] Corrosion rate = ΔW /A.T ΔW = W1-W2 W1 =Weight before corrosion W2 = Weight after corrosion A = Exposure area T = Time Olympus photomicroscope device used to show the type of corrosion occured in wire. Fig (5) The corrosion rate data obtained were recorded and submitted to statistical analysis. Statistical Analyses The suitable statistical methods were used in order to analyze and assess the results, they include the followings: 1- Descriptive statistics: A) Statistical tables including observed frequencies. B) Summary statistic of the readings distribution (mean, SD, SR, minimum & maximum). C) Graphical presentation by (bar - charts). 2 – Inferential statistics: These were used to accept or reject the statistical hypotheses, they include the followings: A) (ANOVA) Analysis of variation test (F-test). B) (LSD) less Significant difference (F-test). Note: The comparison of significant (P-value) in any test were: S= Significant difference (P<0.05). HS= Highly Significant difference (P<0.01). NS= Non Significant difference (P>0.05). Results Corrosion rate test results Results of corrosion rate calculated in ( ∆w/mg ) were obtained for (40) samples ,which include the four groups (ten samples) in each group. The mean of samples, standard deviation, slandered error, maximum &minimum for each group (before corrosion and after corrosion) are listed in table (2)& table (3) IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Graphical presentation by bar chart between the mean of wire weight (before and after the corrosion) of the four gauges , shown in fig (6). Graphical presentation by bar chart between the mean corrosion rates of the four groups, is shown in fig (7). The charts represent clearly change in response between the corrosion rate according to their statistic values. Inferential statistical methods represented by analysis of variance “ANOVa” test show that there are statistically significant difference at P<0.05 (was recorded between at least two different groups).Table (6) The source of difference is investigated by further complement analysis of data by using LSD (least significant difference) test to examine the difference between the different pairs of the four groups as shown in table (7) Discussion Wires often remain in the oral cavity for several months. Whether they are part of fixed or removable orthodontic appliance. The wire should therefore have good corrosion resistance in order to remain with stand attack from oral fluid. The corrosion resistance of alloy is one of the most important factors in dental prosthesis success, because of possible biological reactions and because of possible destruction of the restoration [4,5 ]. The oral cavity provides an ideal and unique environment for studying the biological processes involving metallic dental aids. Dental materials within the mouth interact continuously with physiological fluids. Oral tissues are exposed to a veritable bombardment of both chemical and physical stimuli, as well as the metabolism of about 30 species of bacteria (the total salivary bacterial count is said to be five thousand million/ml of saliva). Saliva is a hypotonic solution containing bioactonate, chloride, potassium, sodium, nitrogenous compounds and protein [13]. The pH of saliva varies from 5.2 to 7.8. Corrosion, the graded degradation of materials by electrochemical attack, is of concern particularly when orthodontic appliances are placed in the hostile electrolytic environment provided by the human mouth [14]. Factors such as temperature, quantity and quality of saliva, plaque, pH, proteins, physical/chemical properties of solids/liquids food and oral conditions may influence corrosion processes.[15,16] Table (2) showed the differences in weight between different wires. This is due to the fact that the different wire had different gauge. Table (3) showed the differences between different wires. This is due to the fact that the different wire had different gauge and different corrosion behavior of the wire. Comparison between W1& W2 of each gauge of wire mentioned in table (4). This table showed non statistical significant in mean of 0.6mm. stainless steel wire and non statistical significant in mean of 0.7mm.stainless steel wire ,but showed statistical significant in mean of 0.8mm stainless steel wire and highly statistical significant in mean of 1.0mm. stainless steel wire . This means that the 0.6mm and 0.7mm have more corrosion resistance than 0.8mm and 1.0mm. This may be due to the corrosion depended on surface area that exposure to the solution (artificial saliva).Thase results are also mentioned in figure (2). Table (5) mentioned the mean of corrosion rate of four gauges after calculating the corrosion according to corrosion rate formula( the change in weight on exposure area and time ) ,showed that the 1.0mm stainless steel has more corrosion resistance followed by 0.8mm, followed by 0.6mm and finally by 0.7mm of stainless steel wire The “ANOVa” test for corrosion rate in table (6) between groups and within group showed the statistical significant values (p<0.005). The least significant difference (LSD) of multiple comparison test showed that o.6mm of stainless steel wire has non statistical significant compared with 0.7mm and 0.8mm but highly significant with 1.0mm ,This is due to the fact that (W1&W2) of 1.0mm .was more than 0.6 mm. stainless steel wire before and after corrosion .The 0.7mm has no significant difference as compared with 0.8mm but highly statistical significant with 1.0mm stainless steel but IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 0.8mm significant as compared with 1.0mm stainless steel wire. This results is in an agreement with [17]. They found that the large surface area provided by wire surface provided favorable environment for growth of bacteria and led to corrosion. There are different forms of corrosion occur in the alloy , Uniform Corrosion , Pitting Corrosion, Crevice Corrosion, Fretting and Erosion-Corrosion , Intergranular Corrosion, Galvanic Corrosion of Orthodontic Alloys, Stress Corrosion of Orthodontic Wires, Hydrogen damage,and Microbial Corrosion [18], microscopic anaylsis of the metal surface also used to detect the types of corrosion [19]. In this study, the type of corrosion was pitting corrosion type of all gauges of wire was examined by microscope (x4 magnification).fig (8)& (9) This result in this study is in an agreement with [16] but in disagreement with [19], they found that the most type of corrosion was crevice corrosion. Potentiodynamic polarization experiments and scanning electron microscopic oberservations of arch wires composed of stainless steel, CoCr, NiCr, NiTi and Beta-Ti exposed to electrochemical corrosion in artificial saliva have shown evidence of pitting corrosion formed on the wire surfaces.[20] Pitting corrosion is a sharply localized corrosion occurring on base metal such as iron, nickel & chromium, which are protected by a naturally thin film of an oxide .In the presence of chlorides in the environment, the film locally breaks down and has rapid dissolution of the underlying metal occurs in the form of pits or holes. This may be isolated or closed together that they look like a rough surface and the occur within or at the grain boundaries of alloy.[18,21] Conclusions On the basis of the results arrived at, the following conclusions can be drawn: 1- There is no statistically significant difference in mean corrosion value of 0.6mm. stainless steel wire group (group A) also in group (B) 0.7 mm. stainless steel wire . 2- Statisticaly significant difference in mean corrosion value of 0.8mm. stainless steel group (group C) and highly significant difference in mean corrosion value of 1.0mm. stainless steel group (group D). 3 –Statistically significant difference in mean corrosion rate value was observed of different group with different gauge and the best outcome of corrosion resistance were found for the 1.0mm group and low corrosion resistance was found in 0.7 mm .group. 4- The type of corrosion of different group with different gauge was pitting corrosion. References 1- Phillips, R.W. (1973), Science of dental materials .7th .255. 2- Kusy, R.P.A. (1997), " Areview of contemporary arch wires: their properties and chanceries tic .Angle orthod : 67 :197 – 207 . 3- Al- Hiyasat, A.S.; Bashabsheh; O.M . and Darmni, H. ( 2003) :Elements release from dental casting alloys and their cytotoxic effect .Int.J p rosthodent .16:8-12 4- Geis –gerstorfer, J.;Weber, H. (1987): "In vitro corrosion behavior of four Ni/Cr dental alloy in lactic acid and sodium chloride solution .dent matter : 3:289.295 . 5- Anusavice, K.J. ( 1996) , "Philip's science of dental material " 10ed " Philadelphia , sounders ch 14 : 315 - , ch 15 : 327 – 346 , ch 16 : 347 – 359 , ch 20 : 423 – 459 , ch 23 : 491 -524 , ch 27 : 619 – 630. 6. Jia, W.; Beatty, M.W.; Reinhardt, R.A.; Petro, T.M.; Cohen, D.M.; Maze, C.R.;Strom EA, and Hoffman, M. (1999),Nickel release from orthodontic arch wires and cellular immune response to various nickel concentrations. J Biomed Mater Res. 48:488–495. 7. Kerosuo, H.; Moe, G.and Kleven, E. (1995), In vitro release of nickel and chromium from different types of simulated orthodontic appliances. Angle Orthod. 65:2111–116. IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 8. Iijima, M.; Endo, K.; Ohno, H.; Yonekura, Y. and Mizoguchi, I. (2001),Corrosion behavior and surface structure of orthodontic Ni-Ti alloy wires. Dent Mater J. 20:1103–113. 9. Maruthamuthu ,S. et al(2005), electrochemical behavior of microbes on orthodontic wires. urrent Science, 89( 6). 10-Luthy , H.;Marinceello, C.P; Reclarn L, Scharer P. (1996). "Corrosion consideration in the 524.-:515 75brazing repair of Co/Cr based PD". J prosthetics dent: 11-Humphrey, S.P., and Williamson, R.T. (2001):"A review of saliva normal comparison,flow and function" J p rosthetic dent; 85: 162-169. 12- Moberg, L.E.(1985), Long – term corrosion studies in vitro of gold, Co/Cr, and Ni/Cr 222.-:21543alloys in contact ". Acta dental Scand. 13. Martinez, J.R. and Barker, S. (1987), Ion transport and water movement. Arch.Oral Biol. 32: 843-847. 14. Maijer, R.; Smith, D.C. (1986), Biodegradation of the orthodontic bracket system. Am Orthod Dentofac Orthop .; 90:195–198. 15. Brantley, W.A. (2001),Orthodontic wires. In: Brantley WA, Eliades T, eds. Orthodontic Materials: Scientific and Clinical Aspects. Stuttgart: Thieme,77–103. 16-Al-Hiyasat, A.S. and Darmani, H.(2005), the effect of recasting on the cytotoxicity of base 163.-(2): 15893metal alloy " J prosthet ; 17. Maruthamuthu,S.; Rajasekar,A.; Sathiyanarayanan, S. ; Muthukukumar,N.and Palaniswamy,N. (2005),Electrochemical behavior of microbes on orthodontic wires. Current Science, 89( 6):988-996. 18-Noort, V. (2002): "Introduction to dental material" 2 en ed. 109:61-67 19-Platt, A. ;Guzmen, A.;Zuccari and Thornburg, W .(1997):"Corrosion behavior of 2205 79.-:69112duplex stainless steel " AMJ ortho Dentolac orthop ; 20. Barret,R.D.; Bishara, S.E. Quinn, J.K. (1993),Biodegradation of orthodontic appliancesPart I: biodegradation of nickel and chromium in vitro. Am J Orthod Dentofac Orthop103:8–14. 21- Benatti, O.F.M .; Miranda, W.J; Muench, A. (2000),In vitro and in vivo corrosion evaluation of Ni /Cr and copper aluminum-based alloy" J p rosthetic Dent, 84 (3): 360 – 363. Fig. (1) Wire with different gauge IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Fig. (2) Diagram illustrates the distribution of the samples Fig. (3) The specimen & ruler Fig.(5) Olympus photomicroscope device Fig. (4) The specimen in Acetone Materials IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Fig. (6) Comparison between W1 / mg (Before corrosion) & W2 / mg (After corrosion) among studied groups Fig. (7) Mean distribution of corrosion rate among studied groups 0 0.00005 0.0001 0.00015 0.0002 0.00025 0.0003 M e a n o f c o rr o s io n r a te A(0.6)mm B(0.7)mm C(0.8)mm D(1)mm Studied groups 0 0.00005 0.0001 0.00015 0.0002 0.00025 0.0003 M e a n o f c o rr o s io n r a te A(0.6)mm B(0.7)mm C(0.8)mm D(1)mm Studied groups IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 A B C D Fig. (8 ) Stainless steel wire under microscope before corrosion (a :0.6mm;B:0.7mm; C :0.8mm ;D:0.9mm A B C D Fig. (9 ) Stainless steel wire under microscope after corrosion (a :0.6mm;B:0.7mm; C :0.8mm ;D:0.9mm ) IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Table (1): Composition of artificial saliva used in this investigation Element Composition in gm/ml Nacl 0.4 KCl 0.4 CaCl2.2H2O 0.795 Na H2PO4 0.69 Urea 1.0 Table (2): Mean distribution of W1 / mg (Before corrosion) among studied groups Studied groups No. Mean Std. Dev. Std. Error Mini. Maxi. A (0.6 mm) 10 0.021 0.0006 0.0002 0.0208 0.0223 B (0.7mm) 10 0.030 0.0001 0.00006 0.0300 0.0305 C (0.8mm) 10 0.038 0.0002 0.0001 0.0381 0.0390 D (1.0mm) 10 0.051 0.0012 0.00047 0.0494 0.0530 Total 40 Table (3): Mean distribution of W2 / mg (After corrosion) among studied groups Studied groups No. Mean Std. Dev. Std. Error Mini. Maxi. A (0.6 mm) 10 0.0207 0.000567 0.000214 0.0200 0.0218 B (0.7 mm) 10 0.0294 0.000195 0.000073 0.0292 0.0297 C (0.8 mm) 10 0.0369 0.000267 0.000101 0.0366 0.0372 D (1.0mm) 10 0.0469 0.00199 0.000752 0.0425 0.0481 Total 40 IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Table (4): Comparison between W1 / mg (Before corrosion) & W2 / mg (After corrosion ) among studied groups Gauge of wires (groups) ∆W No. Mean Std. Dev. Std. Error Mini. Maxi. A (0.6 mm) W1 10 0.021 0.0006 0.0002 0.0208 0.0223 W2 10 0.0207 0.000567 0.000214 0.0200 0.0218 Total 20 P-value (0.968) Non Sig. (P>0.05) B (0.7mm) W1 10 0.030 0.0001 0.00006 0.0300 0.0305 W2 10 0.0294 0.000195 0.000073 0.0292 0.0297 Total 20 P-value (0.973) Non Sig. (P>0.05) C (0.8 mm) W1 10 0.038 0.0002 0.0001 0.0381 0.0390 W2 10 0.0369 0.000267 0.000101 0.0366 0.0372 Total 20 P-value (0.031) Sig. (P<0.05) D (1.0mm) W1 10 0.051 0.0012 0.00047 0.0494 0.0530 W2 10 0.0469 0.00199 0.000752 0.0425 0.0481 Total 20 P-value (0.00) Highly Sig. (P<0.01) Table (5): Mean distribution of corrosion rate among studied groups Studied groups No. Mean Std. Dev. Std. Error Mini. Maxi. A (0.6 mm) 10 0.000118 0.000056 0.000021 0.00006 0.00020 B (0.7mm) 10 0.000085 0.000011 0.000004 0.00007 0.00010 C (0.8mm) 10 0.000153 0.000036 0.000013 0.00012 0.00021 D (1.0mm) 10 0.000291 0.000209 0.000079 0.00011 0.00075 Total 40 IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.23 (2) 2010 Table (6): The ANOVA test for corrosion rate among studied groups ANOVA test Sum of Squares dF Mean Square F P-value Sig. Between Groups 0.0000002 3 0.00000006 4.700 0.012 Sig. (P<0.05) Within Groups 0.0000003 24 0.00000001 Total 0.0000005 27 Table (7): The least significant difference (LSD) of multiple comparison tests for corrosion rate among studied groups Studied groups LSD (F-test) P-value Sig. A (0.6mm) B (0.7mm) 0.583 Non Sig. (P>0.05) C (0.8mm) 0.564 Non Sig. (P>0.05) D (1.0mm) 0.007 Highly Sig. (P<0.01) B (0.7mm) C (0.8mm) 0.265 Non Sig. (P>0.05) D (1.0mm) 0.002 Highly Sig. (P<0.01) C (0.8mm) D (1.0mm) 0.028 Sig. (P<0.05) IHJPAS 2010) 2( 32المجلد مجلة ابن الهیثم للعلوم الصرفة والتطبیقیة في عملفي السلك المقاوم للصدأ المستكلي في مختلف القیاسات آالسلوك الت طقم األسنان الجزئي المتحرك وأجهزة تقویم األسنان نضال صاحب منصور لطبیةكلیة التقنیات الصحیة وا، هیئة التعلیم التقني الخالصه ـابك فـي صـناعة طقــم األسـنان الاألبشـكل شــائع لصـناعة اجهـزه تقــویم األســالك تسـتعمل أن . جزئــيسـنان وكمشـ مقاومة التاكل تعتبر من الصفات االكثر اهمیه في سبیكة األسنان لما لها من تاثیر سلبي على انسجة الجسـم الحیـه وجهـاز ه تقـیم سـلوك التأكـل فـي ، كمـا أن الظـروف فـي الفـم مناسـبه جـدا لحـدوث عملیـة التأكـل.األسـنان نفسـه الهـدف مـن هـذه الدراسـ حضـرت اربـع قیاسـات مـن السـلك المقـاوم للصـدأ المسـتعمل فـي . للصدأ فـي اللعـاب الصـناعي اربع قیاسات من الحدید المقاوم عشـرة عینـات فـي كـل ) A,B,C,&D(للقیاس الى اربع مجـامیع " تقویم األسنان المتحرك وطقم األسنان الجزئي وقسمت طبقا محلـول لالختبـار واســتخدم ك) Fusayam mere(حضــر اللعـاب مـن نـوع ،) واحـد سـنتمیتر(مجموعـه طـول كـل عینـه ه قبــل الغمــر فــي اللعــاب الصــناعي وســجلت تلــك القــراءه كــوزن اولــي بعــد ذلــك ) W1(میـزان الكترونــي حســاس لــوزن العینــ ه بالكامـل ومـن كــل )االسـنان تنظیـف خـیط( وضـعت كـل عینـه فـي وعـاء وعلقـت بخـیط مـن البالسـتك لضـمان غمـر العینـ یوم ازیلت تلك العینات وتركت تجـف ثـم وزنـت كـل عینـه ) ۱٤(ولمدة ۲ +٣۷ه الجهات ثم وضعت في حاضنه بدرجه حرار ـاز وسـجلت كقــراءه ثانیــه وبعـد الحصــول علــى الـوزن االول والثــاني واخـراج الفــرق بــین الـوزن لكــل عینــه ، W2)(بـنفس الجهـ وجد ا األخـتالف فـي " حصائیاوكذلك ا، ملیمتر اكثر مقاومة للتاكل من االحجام االخرى ۷،٠ملیمتر و ٠، ٦كانت النتیجه ائیا. ملمیتـر ٠،۱ملمیتـر و ۸،٠فـي " الـوزن كـان كبیـرا ٠،۱ملمیتـر ۸،٠( ان " وعنـد تطبیـق معادلـه التاكـل وجـد احصـ .ملمیتر۷،٠ملمیتر و ٦,٠اكثر مقاومة للتاكل من )ملمیتر IHJPAS