IBN AL- HAITHAM J. FOR PURE & APPL. S CI. 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 app liances and occasionally as wrought clasp s and rests on p artial dentures. The corrosion resistance is the most imp ortant p rop erties of dental alloy. Corrosion p rocess 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 st udy was t o evaluate the corrosion behavior of different gauges of st ainless st eel wire in artificial saliva .Four gauges of dental st ainless st eel wire used in orthodont ic and removable p artial denture were used in this st udy 0.6mm.,0.7mm.,0 .8mm.&1.0mm.).The sp ecimens were divided according to gauge in to four group s(A,B,C,&D ) ,ten sp ecimens in each group .Each wire was cut by using wire cutter to get wire with (1cm) in length .Art ificial saliva of Fusayama M eyer ty p e 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 sp ecimen was p ut inside a test tube , and held using dental floss in a way that the sp ecimen was fully immersed in the solution from all sides . The sp ecimens then were p ut inside an incubator ,which was adjusted at 37±2 and left for 14 days .At the end of immersion p eriod ; the sp ecimens were removed from the solution and then allowed to dry and were balanced then the results were recorded .This represents the second weight (W2) .Aft er obtaining the (W1)&(W2) the corrosion rate was calculated . The results before and after immersion showed that the 0.6 mm.& 0.7mm st ainless st eel wire gave the highest and more corrosion resistance value than 0.8mm&1.0mm.stainless st eel wire . The result showed there is a statistical si gnificance between (W1&W2) of 0.8mm st ainless st eel wire and highly sign ificant between (W1&W2) of 1.0mm. stainless st eel wire . The comparison of t he results after calculating r esults in corrosion rate formula showed that the 1.0mm stainless st eel 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 clasp s in connection with p artial dentures. Unt il the 1930 the only orthodontic wires available were made of gold and austenitic st ainless st eel with greater strength. [1] Various wire sizes and four arch wire alloys are now available st ainless st eel, cobalt, chromium, nickel titanium and beta titanium. The ideal orthodontic wire p rop erties can be described in lay er terms of the following criteria ,but in contemporary p ractice ,no one wire meets all these requirements , and the best result is obt ained by using sp ecific wire for IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 sp ecific p urp ose ,the criteria are : st rong ,resilience , weld able , solder able ,low cost , low friction ,and bio compatibility .[2] There are essentially three ty p es of st ainless st eels. This classification is with app roximate comp ositions. The ty p e includes: ferrite st ainless st eel, martenstic st ainless st eel &aust enitic st ainless st eel. [1] Bio comp atibility and corrosion resistance of alloys were related to the comp osition and elements or irons related in to surrounding medium. [3] The corrosion resistance is of great imp ortance because of p ossible biological reaction (adverse effects on both living tissues) and because of p ossible destruction of the restoration [4, 5] and lead to roughening of the surface, weakening of the app liances, and liberation of elements from the metal or alloy [6].Release of elements can p roduce discoloration of adjacent soft tissues and allergic reactions in suscep tible p atients [7].Corrosion can severely limit the fatigue life and ultimate st rength of the material leading to mechanical failure of the dental materials .[8] Corrosion p roducts were imp licated in causing local p ain or swelling in the region of the orthodontic app liances in the absence of infection, which can lead to secondary infection. [9] This st udy aims to invest igate the corrosion behavior of st ainless st eel wire with different gauge in artificial saliva. Materials and Methods Materials, Instruments & Equi pments: * Dist illed water (Iraq) * NaCl, KCl, CaCl2, 2H2O, NaH2PO4& urea cry st al (artificial saliva of Fusay ama, M eyer type) *Dental st ainless st eel 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 b icarbonate & nitric acid. Instrument & Equi pments:-  Sensitive electronic b alance (Germany)  Incubator (England )  M illimeter ruler  Wire cutter  Electronic p H meter (Jap an)  Tubes (testing tube & measuring tube)  Oly mpus p hotomicroscope sy st em with exp osure control unites (Japan). Methods Four gauges of dental st ainless st eel wire used in orthodont ic & remov able p artial denture were used in this st udy , (0.6 mm, 0.7 mm, 0.8 mm & 1.0 mm). The sp ecimens were d ivided according to gauge into four group s, (A, B, C &D) ten sp ecimens in each group .fig (2) Dental st ainless st eel wire with different gauge (d iameter) were used in this st udy 0.6 mm , 0.7 mm , 0.8 mm , &1.0 mm ) that using in removable orthodontic & removable p artial denture fig (1).Each wir e was cut by used wire cutter to get wire with 1 cm in length (used ruler to measure the len gth of wire).fig (3) The finished were rinsed in distilled water to remove any att ached p articles, and then allowed to dry in air .The sp ecimen 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 samp les before immersion in solution & recording the results .T his represented the first weight (w1). Preparation of the testing solution Art ificial saliva of Fusayama- M eyer type was used as the testing solution [10] .The comp osition of artificial saliva mentioned in table (1). An electronic balance was used to p repare the required amounts of each element of artificial saliva which were mixed in one liter of distilled water. The pH of t he solution is adjust ed at (p H=6) by using sodium bicarbonate .This st imulates the pH of natural saliva. The p H of t he solution was est imated 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 sp ecimen was p ut inside a test tube, and held using a dental floss in way that the sp ecimen 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 p repared as described in table (1). The sp ecimen then were p ut inside incubator which was adjust ed at 37 C ◦ ± 2 and left for 14 days [11] t he solutions were shaked for about (5 seconds ) daily in order to p revent the solution from being p recipitated. At the end of the immersion p eriod, the sp ecimen were removed from the solution &then allowed to dry & were balanced then the result was recorded .This rep resented 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 = Exp osure area T = Time Oly mp us p hotomicroscope device used to show t he typ e of corrosion occured in wire. Fig (5) The corrosion rate data obtained were record ed and submitt ed to statistical analysis. S tatistical Analyses The suitable st atist ical methods were used in order to analyze and assess the results, they include the followings: 1- Descriptive st atist ics: A) Statistical tables including observed frequencies. B) Summary st atist ic of the readings dist ribution (mean, SD, SR, minimum & maximum). C) Grap hical p resentation by (bar - charts). 2 – Inferential statist ics: These were used to accep t or reject the st atist ical hy p otheses, they include the followings: A) (ANOVA) Analysis of variation test (F-t est). B) (LSD) less Significant difference (F-t est). Not e: 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). Re sults Corrosion rate test results Results of corrosion rate calculated in ( ∆w/mg ) were obtained for (40) samples ,which include the four group s (t en samp les) in each group . The mean of samples, st andard deviation, slandered error, maximum &minimum for each group (before corrosion and after corrosion) are list ed in table (2)& table (3) IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Grap hical p resentation by bar chart between the mean of wire weight (before and after the corrosion) of the four gauges , shown in fig (6). Grap hical p resentation by bar chart between the mean corrosion rates of the four group s, is shown in fig (7). The charts represent clearly change in resp onse between the corrosion rate according to their st atist ic values. Inferential statist ical methods rep resented by analysis of variance “ANOVa” test show that there are st atist ically significant difference at P<0.05 (was recorded between at least two different group s).T able (6) The source of difference is invest igated by further comp lement analysis of data by using LSD (least significant difference) test to examine the difference between the different p airs of the four group s as shown in table (7) Discussion Wires often remain in the oral cavity for several months. Whether they are p art of fixed or removable orthodont ic app liance. The wire should therefore have good corrosion resistance in order to remain with st and attack from oral fluid. The corrosion resistance of alloy is one of the most imp ortant factors in dental p rost hesis success, because of p ossible biological reactions and because of p ossible destruction of the restoration [4,5 ]. The oral cavity p rovides an ideal and unique environment for st udy ing the biological p rocesses involving metallic dental aids. Dental materials within the mouth interact continuously with p hy siological fluids. Oral tissues are exp osed to a veritable bombardment of both chemical and p hy sical st imuli, as well as the metabolism of about 30 sp ecies of bacteria (the total salivary bacterial count is said to be five thousand million/ml of saliva). Saliva is a hy p otonic solution containing bioactonate, chloride, p otassium, sodium, nitrogenous comp ounds and protein [13]. The p H of saliva varies from 5.2 to 7.8. Corrosion, the graded degradation of materials by electrochemical att ack, is of concern p articularly when orthodontic app liances are p laced in the host ile electrolytic environment p rovided by the human mouth [14]. Factors such as temp erature, quantity and quality of saliva, p laque, p H, p roteins, p hy sical/chemical p rop erties 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 t he 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 st atist ical significant in mean of 0.6mm. st ainless st eel wire and non st atist ical significant in mean of 0.7mm.st ainless st eel wire ,but showed st atist ical significant in mean of 0.8mm st ainless st eel wire and highly st atist ical significant in mean of 1.0mm. st ainless st eel 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 exp osure 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 exp osure area and time ) ,showed that the 1.0mm st ainless st eel has more corrosion resistance followed by 0.8mm, followed by 0.6mm and finally by 0.7mm of st ainless st eel wire The “ANOVa” test for corrosion rate in table (6) between group s and within group showed the statist ical significant values (p <0.005). The least significant difference (LSD) of multiple comp arison test showed that o.6mm of st ainless st eel wire has non st atist ical significant comp ared 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. st ainless st eel wire before and after corrosion .The 0.7mm has no significant difference as comp ared with 0.8mm but highly st atist ical significant with 1.0mm st ainless st eel but IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 0.8mm significant as comp ared with 1.0mm st ainless st eel wire. This results is in an agreement with [17]. They found that t he large surface area p rovided by wire surface p rovided favorable environment for growt h 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 Ort hodontic Alloys, Stress Corrosion of Ort hodontic Wires, Hy drogen damage,and M icrobial Corrosion [18], microscopic anay lsis of the metal surface also used to detect t he ty p es of corrosion [19]. In this st udy , the ty p e of corrosion was p itt ing corrosion ty p e of all gauges of wire was examined by microscope (x4 magnification).fig (8)& (9) This result in this st udy is in an agreement with [16] but in disagreement with [19], they found that t he most ty p e of corrosion was crevice corrosion. Pot entiody namic p olarization exp eriments and scanning electron microscopic oberservations of arch wires comp osed of st ainless st eel, CoCr, NiCr, NiTi and Beta-Ti exp osed to electrochemical corrosion in artificial saliva have shown evidence of p itt ing corrosion formed on the wire surfaces.[20] Pitting corrosion is a sharp ly localized corrosion occurring on base metal such as iron, nickel & chromium, which are p rotected by a naturally thin film of an oxide .In the p resence of chlorides in the environment, the film locally breaks down and has rapid dissolution of the underly ing metal occurs in the form of p its 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 t he basis of t he results arrived at, t he following conclusions can be drawn: 1- There is no st atist ically significant difference in mean corrosion value of 0.6mm. st ainless st eel wire group (group A) also in group (B) 0.7 mm. st ainless st eel wire . 2- Statist icaly significant difference in mean corrosion value of 0.8mm. st ainless st eel group (group C) and highly significant difference in mean corrosion value of 1.0mm. st ainless st eel group (group D). 3 –Statist ically 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 ty p e of corrosion of different group with different gauge was p itt ing corrosion. Re ferences 1- Phillips, R.W. (1973), Science of dental materials .7 th .255. 2- Kusy , R.P.A. (1997), " Areview of contemporary arch wires: their p rop erties and chanceries tic .Angle orthod : 67 :197 – 207 . 3- Al- Hiy asat, A.S.; Bashabsheh; O.M . and Darmni, H. ( 2003) :Elements release from dental cast ing alloys and their cytotoxic effect .Int .J p rost hodent .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 " 10 ed " Philadelp hia , 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.; Beatt y , M .W.; Reinhardt, R.A.; Petro, T .M .; Cohen, D.M .; M aze, C.R.;Strom EA, and Hoffman, M . (1999),Nickel release from orthodontic arch wires and cellular immune resp onse to various nickel concentrations. J Biomed M ater Res. 48:488–495. 7. Kerosuo, H.; M oe, G.and Kleven, E. (1995), In vitro release of nickel and chromium from different t y p es of simulated orthodontic app liances. Angle Ort hod. 65:2111–116. IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 8. Iijima, M .; Endo, K.; Ohno, H.; Yonekura, Y. and M izoguchi, I. (2001),Corrosion behavior and surface structure of orthodontic Ni-Ti alloy wires. Dent M ater J. 20:1103–113. 9. M aruthamuthu ,S. et al(2005), electrochemical behavior of microbes on orthodontic wires. urrent Science, 89( 6). 10-Luthy , H.;M arinceello, C.P; Reclarn L, Scharer P. (1996). "Corrosion consideration in the 524.-:515 75brazing repair of Co/Cr based PD". J p rost hetics dent: 11-Hump hrey, S.P., and Williamson, R.T. (2001):"A review of saliva normal comp arison,flow and function" J p rost hetic dent; 85: 162-169. 12- M oberg, L.E.(1985), Long – term corrosion studies in vitro of gold, Co/Cr, and Ni/Cr 222.-:21543alloys in contact ". Acta dental Scand. 13. M artinez, J.R. and Barker, S. (1987), Ion transp ort and water movement. Arch.Oral Biol. 32: 843-847. 14. M aijer, R.; Smith, D.C. (1986), Biodegradation of the orthodontic bracket sy st em. Am Ort hod Dentofac Ort hop .; 90:195–198. 15. Brantley, W.A. (2001),Ort hodontic wires. In: Brantley WA, Eliades T, eds. Ort hodontic M aterials: Scientific and Clinical Asp ects. Stuttgart: Thieme,77–103. 16-Al-Hiy asat, A.S. and Darmani, H.(2005), the effect of recast ing on the cy totoxicity of base 163.-(2): 15893metal alloy " J p rosthet ; 17. M aruthamuthu,S.; Rajasek ar,A.; Sathiy anarayanan, S. ; M uthukukumar,N.and Palaniswamy,N. (2005),Electrochemical behav ior of microbes on ort hodontic wires. Current Scien ce, 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.-:69112dup lex st ainless st eel " AMJ ortho Dentolac orthop ; 20. Barret,R.D.; Bishara, S.E. Quinn, J.K. (1993),Biodegradation of orthodontic app liancesPart I: biodegradation of nickel and chromium in vitro. Am J Ort hod Dentofac Ort hop 103:8–14. 21- Benatti, O.F.M .; M iranda, W.J; M uench, A. (2000),In vitro and in vivo corrosion evaluation of Ni /Cr and copp er aluminum-based alloy " J p rost hetic Dent, 84 (3): 360 – 363. Fig. (1) Wire with different gauge IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Fig. (2) Diagram illustrates the distribution of the samples Fig. (3) The specimen & ruler Fig.(5) Olympus photomi croscope device Fig. (4) The specimen in Acetone Materials IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Fig. (6) Comparison between W1 / mg (Before corrosion) & W2 / mg (After corrosion) among studied groups Fig. (7) Mean distributi on of corrosi on 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. S CI. VOL.23 (2) 2010 A B C D Fig. (8 ) S tainless steel wire under microscope before corrosi on (a :0.6mm;B:0.7mm; C :0.8mm ;D:0.9mm A B C D Fig. (9 ) S tainless steel wire under microscope after corrosi on (a :0.6mm;B:0.7mm; C :0.8mm ;D:0.9mm ) IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. 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 studie d groups S tudie d groups No. Mean S td. De v. S td. 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 co rrosi on) among studied groups S tudie d groups No. Mean S td. De v. S td. 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. S CI. 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 S td. De v. S td. 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 corrosi on rate among studied groups S tudie d groups No. Mean S td. De v. S td. 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. S CI. VOL.23 (2) 2010 Table (6): The ANO VA test for corrosion rate among studied groups ANOVA test Sum of Squares dF M ean 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 si gni ficant difference (LS D) of mul tiple comparison te sts for corrosi on rate among studie d groups Studied group s 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 أن . جزئــيسـنان وكمشــابك فـي صـناعة طقــم األسـنان الاألبشـكل شــائع لصـناعة اجهـزه تقــویم األســالك تسـتعمل مقاومة التاكل تعتبر من الصفات االكثر اهمیه في سبیكة األسنان لما لها من تاثیر سلبي على انسجة الجسـم الحیـه وجهـاز الهـدف مـن هـذه الدراسـه تقـیم سـلوك التأكـل فـي ، كمـا أن الظـروف فـي الفـم مناسـبه جـدا لحـدوث عملیـة التأكـل.األسـنان نفسـه 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 بعــد ذلــك ) W1(میـزان الكترونــي حســاس لــوزن العینــه قبــل الغمــر فــي اللعــاب الصــناعي وســجلت تلــك القــراءه كــوزن اولــي لضـمان غمـر العینـه بالكامـل ومـن كــل )االسـنان تنظیـف خـیط( وضـعت كـل عینـه فـي وعـاء وعلقـت بخـیط مـن البالسـتك یوم ازیلت تلك العینات وتركت تجـف ثـم وزنـت كـل عینـه ) ۱٤(ولمدة ۲ +٣۷ه الجهات ثم وضعت في حاضنه بدرجه حرار وبعـد الحصــول علــى الـوزن االول والثــاني واخـراج الفــرق بــین الـوزن لكــل عینــه ، W2)(بـنفس الجهــاز وسـجلت كقــراءه ثانیــه وجد ا األخـتالف فـي " حصائیاوكذلك ا، ملیمتر اكثر مقاومة للتاكل من االحجام االخرى ۷،٠ملیمتر و ٠، ٦كانت النتیجه ٠،۱ملمیتـر ۸،٠( ان " وعنـد تطبیـق معادلـه التاكـل وجـد احصـائیا. ملمیتـر ٠،۱ملمیتـر و ۸،٠فـي " الـوزن كـان كبیـرا .ملمیتر۷،٠ملمیتر و ٦,٠اكثر مقاومة للتاكل من )ملمیتر IHJPAS