The first dedicated device for measuring static friction in orthodontic ex-vivo searches , Al-Munajed, Mohamad. K: Associate Professor, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. Khalil, Fadi: Assistant Professor, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. Kablan, Fatema. A (Corresponding Author): MSc student, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. E-mail: dr.kablan.f@hotmail.com Abstract: Introduction: Orthodontists always search for a dedicated device to assess the friction in orthodontics and search for low friction esthetic brackets. Until now there is no special device to evaluate static friction in orthodontics. Thus, the aim of this study is to assess the validity and reliability of a newly developed static friction tester which is the first device dedicated to testing static friction in orthodontics and to compare the static friction values of conventional metal and recently introduced ceramic brackets using this new device. Material and Methods: (40) Conventional stainless steel brackets, (40) Radiance ceramic brackets, (40) stainless steel orthodontic straight wires and (40) nickel titanium wires were divided into two groups, each group contained (20) metal brackets, (20) ceramic brackets, (20) S.S wires and (20) Ni-Ti wires. Static Friction was evaluated for the first group using the “New Static Friction Tester” and for the other using the “Zweigle F 427 Machine”. Results: The results found no significant differences between (The New Static Friction Tester) group and (The Zweigle F427) machine group for all test groups (p>0.05), but there was a significant difference between friction values generated by the two types of brackets. Conclusions: The (Zweigle F427) has no significant advantages over (The New Static Friction Tester) which is smaller, lighter, affordable and easier to use for in-vitro studies. The Radiance ceramic brackets produce higher friction than S.S brackets. Key-words: Zweigle F 427, Sliding resistance, Static friction, Ceramic brackets. Introduction: Fixed orthodontic appliances are the common choice for treatment of malocclusion[1]. The Straight-Wire® technique was introduced as the first Edgewise orthodontic system that was based on sliding mechanics[2]. Orthodontists use sliding mechanics not only for space closure, but also for the initial stage of leveling and aligning[3]. As the teeth are translated, forces develop which may inhibit their movement[4]. The total of these forces is called the “Resistance to Sliding (RS)”[3]. Proffit (2000) reported that about 50% of the applied force necessary to initiate tooth movement is required to overcome (RS)[5]. Resistance to sliding is divided into 3 components: friction, binding and notching[6]. Friction Force is one of the “RS” components and it is defined as the force that resists the relative motion of two contacting bodies in a direction tangential to the plane of contact[7]. There are two main types of friction: static friction which is the smallest force needed to start the motion of solid surfaces which were previously at rest, whereas kinetic friction is the force that resists the sliding motion of one solid object over another[2]. Ceramic brackets have higher friction than metal brackets[8], therefore, companies always try to develop ceramic brackets with a smoother slot surface, rounding of slot base or consisting of metallic slot surfaces.[9]. Most studies focused on “Static Friction” force only. Kinetic friction was not considered because orthodontic sliding of a tooth (bracket) in an archwire is not a continuous motion[9]. From a clinical point of view, overcoming the static friction force between the bracket and the wire is a prerequisite for tooth movement. Furthermore, static friction force is always greater than kinetic friction, whereas static force determines the magnitude of the force system acting on the teeth, irrespective of the possible low levels of kinetic friction force[9]. These ex-vivo studies had used different devices such as: - Zweigle Tensile Testing Machine[10]. - Instron Universal Testing Machine[7]. - Nene M3000, Wellingborough, UK[11]. - EZ-Test Machine[12]. - LR5K (Lloyd Instruments)[13]. All the devices mentioned above are large and expensive, situated in sophisticated research centers, need expert personnel to operate and their software may need frequent updating. In an attempt to overcome such obstacles, we have developed a new device to measure the static friction values for orthodontic studies. This device is smaller than the previous machines, inexpensive and not complicated. Compared with stainless steel brackets, most studies showed that ceramic brackets generate higher frictional forces, which lead to longer treatment duration[9]. Recently, new designs of ceramic brackets that offer excellent optical properties with the promise of an optimal functional improvement were introduced[9]. The Radiance bracket is one of these new designs. It is startlingly clear compared to other ceramic brackets. It benefits from a proprietary heat polishing process that removes flaws from the surface of the bracket and has a smooth, precision slot for easier sliding mechanics[14].Therefore, the aim of this comparative study was to assess the usability of the “New Static Friction Tester” device for friction investigations in orthodontics and to assess the frictional values of the new ceramic bracket (Radiance). Materials And Methods: Static friction values were measured for metal and ceramic brackets with straight stainless steel and nickel titanium wires. Brackets: The following Roth upper-right canine (tooth 13) brackets for (0.022×0.028 inches) slot size and with no hook were tested in this study: Forty stainless steel brackets (Mini Mater, American Orthodontics, Wisconsin, USA), with torque (-2˚), angulation (+10˚) and mesial-distal width of (3.098 mm). Forty ceramic brackets (Radiance Plus, American Orthodontics, Wisconsin, USA), with torque (-2˚), angulation (+10˚) and mesial-distal width of (3.302 mm). Archwires: Each wire was 6 mm in length and had a hook on the end. Forty straight stainless steel wires with (0.019×0.025 inches) dimensions (American Orthodontics, Wisconsin, USA). Forty straight nickel titanium wires (0.018 inch) (American Orthodontics, Wisconsin, USA). Ligation: 80 clear (O-ring) elastomeric (Unistick-Ligatures, American Orthodontics, Wisconsin, USA) with outer diameter of (2.921 mm) and inner diameter of (1.143 mm) were used. A “ligature gun” (Ortho Technology Inc. Tampa, Florida USA) was used to place each elastomeric ring on the bracket wings. The brackets, wires and ligations were divided into eight groups: -Group 1: (10) metal brackets, (10) S.S wires, (10) elastomeric rings. -Group 2: (10) metal brackets, (10) S.S wires, (10) elastomeric rings. -Group 3: (10) metal brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 4: (10) metal brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 5: (10) radiance brackets, (10) S.S wires, (10) elastomeric rings. -Group 6: (10) radiance brackets, (10) S.S wires, (10) elastomeric rings. -Group 7: (10) radiance brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 8: (10) radiance brackets, (10) Ni-Ti wires, (10) elastomeric ring. Groups (1-3-5-7) were tested using “The New Tester” device while groups (2-4-6-8) were tested using “The Zweigle Machine”. Two testing machines were utilized: testing with “The New Static Friction Tester” (developed by the authors with the help of a mechanical engineer) and with “The Zweigle Machine” (Zweigle Textilprüfmaschinen GmbH, Ferdinand- Lassalle- Strasse 54, Germany). I-The New Static Friction Tester: This machine was constructed as a simple, inexpensive and easy to use device figure (1). Figure1: The New Static Friction Testing Machine. It was designed (with the help of Ali Kablan, a mechanical engineer) to achieve reliable and easy measurements of the static friction of orthodontic materials. The components of this machine are illustrated in figure (2). Figure2: An illustration shows the components of the New Static Friction Testing Machine. Each combination (bracket, wire and elastomeric ligature) was placed in its special place and the hook of the wire was inserted in the ring of the spring. This ring contacts with the two sensors when the spring is not stretched. To start the work with this device, the motor was connected to the electricity, and then we move the two-direction keys to the top, so the motor starts to operate. - When the motor works, the small roller starts its rotation and it translates the move to the middle roller by the elastomeric ring, then to the big roller. - As the big roller moves, the axis will move inside the two bearings so the helix will move with the arm that holds the indicator and the spring. - The spring starts to stretch and it keeps stretching until the wire moves inside the bracket, then the down side of the spring will move back and the ring will be pulled away from the two sensors and the electricity will cut off immediately. - At that moment, the indicator would be stopped at a given number. - This special number indicates the force that is required to move the wire inside the bracket, i.e., the value of the static friction for this special combination (bracket, wire, and ligation). All tests were conducted under dry conditions and at room temperature (29˚ C). Each bracket was mounted on a metal ring with an outer diameter of (20 mm), and an inner diameter of (15 mm) using (Quick Epoxy Steel) adhesive. The position of the bracket was obtained through preliminary insertion of (0.021×0.028 inch) straight stainless steel wire in the slot of the bracket, without ligation, before bonding so the wire is parallel with the ring diameter. After bonding of the bracket on the metal ring, the S.S wire was removed. Each bracket was tested only once and each wire specimen was drawn through one bracket only, so as to eliminate the influence of wear. In total, 80 test models were constructed, i.e. twenty models for each type of brackets (Mini Master and Radiance). II- The Zweigle F 427 Machine: A tensile testing machine. The hardware and software flexibility allow the machine to be custom designed, so it can perform automatic yarn tests, tests on fabrics and friction tests, figure (3). Figure3: The Zweigle F427 testing machine. The resulting frictional force records on a computer screen. Dimensions and weight (without PC): Width: 660 mm, depth: 485 mm, height: 1585 mm and weight: approx. 60 kg The ring (with the bracket) was mounted on the lower arm of the machine while the wire, with the hooked end, was inserted through a ring mounted on the upper arm. The thickness of the upper ring equals the thickness of the lower ring with the base of the bracket, so the wire was mounted vertically figure (4). The crosshead moved upward at a speed of (0.5 mm/min). Figure4: The upper and lower rings in Zweigle machine. Results: The data were analyzed using statistical software (SPSS) version (18.0). Table (1) provides a statistical summary of static friction data for the two bracket materials and the two devices. Table 1. One-way ANOVA analysis of variance was carried out to determine the effect of the device type and the bracket material on the results. The results are summarized in Tables (2 and 3) and figure (5). Table 2. It can be seen from Table (2) that there are no significant differences between the two devices for all test groups (P>0.05). It can be seen from Table (3) that the metal brackets displayed significantly lower frictional forces (P\u003C0.05) than the radiance brackets for the two wire types. Table 3. Figure5: Friction measurements of “The New Tester” and “The Zweigle Machine”. Discussion: The characteristics of an ideal orthodontic appliance include good esthetics and optimal technical performance. Optimal tooth movement with a fixed appliance requires the use of optimal forces, but these forces need to overcome frictional resistance that is present between the wire, the bracket and the means of ligation[13]. Alignment of teeth during leveling is affected by friction[1] and when closing spaces or reducing moderate overjets using sliding mechanics in clinical orthodontic practice, the significance of frictional force may not always be apparent. However, in those cases where anchorage balance is marginal, or where sliding mechanics fail, frictional forces may result in a loss of anchorage[3], so it is important to study frictional values of different (bracket, wire, and ligation) combinations, especially of the different materials of brackets[13]. Frictional values were always measured using complicated and costly testing machines which might not be affordable to all research centers. For this reason, a new testing machine was designed and constructed in this study to measure static friction for orthodontic purposes. The usability and reliability of this machine were assessed according to the following criteria: 1- The first criterion, precision: ANOVA analysis showed no significant differences between the new device and the Zweigle Testing Machine (P\u003C0.05) for the two types of brackets and the two types of wires tested. This means that “The New Static Friction Tester” has precision results and we can use it to study the static friction values of different (bracket, wire, ligation) combinations. 2- The second criterion, the size of the device: The new device is much smaller than “The Zweigle Machine”, (660 mm, 485 mm, 1585 mm), without the PC, for the Zweigle machine versus (340 mm, 80 mm, 20 mm) for the new device. 3- The third criterion, the weight: The new device is much lighter than the Zweigle machine (60 kg) for Zweigle versus (2 kg) for the new device. 4- The fourth criterion, the ease of use: It is very easy to use the new device, whereas it is too complicated to use the Zweigle machine. The new device just needs to be connected to the electrical source and then to move the key, while the Zweigle (and the other universal machines) needs a special mechanism for fixing the sample, a specialist mechanical engineer for calibration, and a continual updating for the software. An increase in the number of adult patients led to the development of various esthetically superior appliances[9]. Ceramic brackets were introduced to the orthodontic specialty in 1986 and since then have become an integral part of the orthodontists’ armamentarium[7]. Although the esthetics are highly desirable, their high coefficient of friction versus metals has caused concern. In order to reduce frictional resistance, the development of ceramic brackets with a smoother slot surface, rounding of slot bases or consisting of metallic slot surfaces has been accomplished[9]. The Radiance bracket is a new ceramic bracket and no previous study had compared the frictional values of this bracket compared to metal brackets. It is made from a single sapphire crystal, the second hardest mineral known, and has a smooth, precision slot for easier sliding mechanics[14]. This bracket is designed to be the strongest ceramic bracket. Mono-crystalline formation gives Radiance a solid core structure as opposed to the strand structure in polycrystalline brackets[14]. A special heat process is then used to seal the bracket and ensure that no fissures exist in the surface structure. The result is a remarkably strong bracket that is far less likely to fail during treatment[14]. Radiance’s mono-crystalline structure and highly polished surface serve as barriers to undesirable staining elements[14]. However, this newly produced bracket failed to overcome the known shortcomings of ceramic brackets with regard to high frictional values. The results presented here showed that the stainless steel bracket produced significantly lower static frictional resistance than the ceramic bracket. Our findings agree with those of some previous studies[15], Al-Munajed study concluded that ceramic brackets produce higher friction than stainless steel brackets[8]. Tanne found that the ceramic bracket may interfere with smooth sliding between bracket and wire[15]. The difference in friction levels between metal and ceramic brackets could be explained by the ceramic bracket characteristics, such as surface roughness, hardness, and stiffness[16]. Manufacturing process, finishing, and polishing are difficult also; this might explain the granular and pitted surface of the ceramic bracket[16] comparing with the smoother surface of stainless steel bracket, which is clearly visible on SEM images[9]. Clocheret study found that ceramic brackets have higher coefficients of friction than metal brackets[17]. The high friction value of Radiance bracket could be due to its hardness. This bracket is designed to be the strongest possible ceramic bracket[14]. Some studies have failed to detect any differences in frictional forces between ceramic and stainless brackets[18]; other studies found that mono-crystalline ceramic bracket had lower mean frictional forces than stainless steel bracket[19]. However, the differences in the results can be explained by analyzing the different experimental methods employed[19]. Conclusion: This study found that the new static friction device could serve as a reliable device for testing and measuring static friction in orthodontics and it has practical advantages over conventional machines. In addition, a newly developed ceramic bracket (Radians) has higher static frictional values compared with the metal brackets. Reference: 1. Wichelhaus A, Geserick M, Hibst RM, Sander FG. The effects of surface treatment and clinical use on friction in Ni-Ti orthodontic wires. Dental Materials 2005; 21: 938-45. 2. Moore MM, Harrington E, Rock WP. Factors affecting friction in the pre-adjusted brackets. Eur J Orthod 2004; 26: 579-83. 3. Ching LY, Budi K, Grace V, Carla AE, James LD. In-vitro evaluation of frictional resistance between brackets with passive-ligation designs. Am J Orthod Dentofacial Orthop 2007;131: 740.e11-704.e22. 4. Cash A, Curtis R, Majo DG, McDonald F. A comparative study of the static and kinetic frictional resistance of titanium molybdenum alloy Archwires in stainless steel brackets. Eur J Orthod 2004; 26: 105-11. 5. Proffit WR, Fields HW. Contemporary fixed appliances. Contemporary orthodontics, 2nd ed. St. Louis: Mosby; 1993. p. 385-91. 6. Loftus BP, Årtun J. A model for evaluating friction during orthodontic tooth movement. Eur J Orthod 2001; 23: 253-61. 7. Budd S, Daskalogiannakis J, Tompson BD. A study of the frictional characteristics of four commercially available self-ligating systems. Eur J Orthod 2008; 30: 645-53. 8. Al-Munajed MK. A study and an assessment of the frictional forces between orthodontic wire and aesthetic orthodontic brackets. Tishreen University Journal for Research and Scientific Studies-Medical Sciences Series 2008; 30: 52-60. 9. Gautam P, Valiathan A. Ceramic bracket: in search of an ideal. Tends Biomater Artif Organs 2007; 20: 220-28. 10. Obaidi HA, Al-Mukhtar AM. The frictional coefficient comparison between stainless steel and beta-titanium arch-wires ligatured to the stainless steel bracket via different ligatures. Al-Rafidain Dental Journal 2008; 8: 79-82. 11. Redlich M, Mayer Y, Harari D. In vitro study of frictional forces during sliding mechanics of “Reduces Friction” brackets. Am J Orthod Dentofacial Orthop 2003; 124: 69-73. 12. Kao CT, Ding SJ, Wang CK, He H, Chou MY, Huang TH. Comparison of frictional resistance after immersion of metal brackets and orthodontic wires in a fluoride-containing prophylactic agent. Am J Orthod Dentofacial Orthop 2006; 130: 569.e1-568.e9. 13. Griffiths HS, Sherriff M, Ireland AJ. Resistance to sliding with 3 types of elastomeric modules. Am J Orthod Dentofacial Orthop 2005; 27: 670-5. 14. American Orthodontics Catalog \u003Chttp://bit.ly/16gNzQH; 15. Tanne k, Matsubara S, Shibaguchi T, Sakuda M. Wire friction from ceramic brackets during simulated canine retraction. The Angle Orthodontist 1991;61:285-292. 16. Nishio C, Da Motta AF, Elias CN, Mucha JN. In vitro evaluation of frictional forces between arch-wires and ceramic brackets. Am J Orthod Dentofacial Orthop. 2004; 125: 56-64. 17. Clocheret K, Willems G, Carels C, Celis J. Dynamic frictional behavior of orthodontic Archwires and brackets. Eur J Orthod 2004; 26:163-170. 18. Kusy RP, Whitely JQ. Coefficients of friction for arch wires in stainless steel and polycrystalline alumina bracket slots: the dry state. Am J Ortho Dentofacial Orthop 1990;98:300-312. 19. Lee WY, Lim KS. A study on frictional resistance force of orthodontic resin bracket. Korea. J. Orthod 1999;29:107-112. , http://bit.ly/XmYz0j

The first dedicated device for measuring static friction in orthodontic ex-vivo searches , Al-Munajed, Mohamad. K: Associate Professor, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. Khalil, Fadi: Assistant Professor, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. Kablan, Fatema. A (Corresponding Author): MSc student, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Lattakia, Syria. E-mail: dr.kablan.f@hotmail.com Abstract: Introduction: Orthodontists always search for a dedicated device to assess the friction in orthodontics and search for low friction esthetic brackets. Until now there is no special device to evaluate static friction in orthodontics. Thus, the aim of this study is to assess the validity and reliability of a newly developed static friction tester which is the first device dedicated to testing static friction in orthodontics and to compare the static friction values of conventional metal and recently introduced ceramic brackets using this new device. Material and Methods: (40) Conventional stainless steel brackets, (40) Radiance ceramic brackets, (40) stainless steel orthodontic straight wires and (40) nickel titanium wires were divided into two groups, each group contained (20) metal brackets, (20) ceramic brackets, (20) S.S wires and (20) Ni-Ti wires. Static Friction was evaluated for the first group using the “New Static Friction Tester” and for the other using the “Zweigle F 427 Machine”. Results: The results found no significant differences between (The New Static Friction Tester) group and (The Zweigle F427) machine group for all test groups (p>0.05), but there was a significant difference between friction values generated by the two types of brackets. Conclusions: The (Zweigle F427) has no significant advantages over (The New Static Friction Tester) which is smaller, lighter, affordable and easier to use for in-vitro studies. The Radiance ceramic brackets produce higher friction than S.S brackets. Key-words: Zweigle F 427, Sliding resistance, Static friction, Ceramic brackets. Introduction: Fixed orthodontic appliances are the common choice for treatment of malocclusion[1]. The Straight-Wire® technique was introduced as the first Edgewise orthodontic system that was based on sliding mechanics[2]. Orthodontists use sliding mechanics not only for space closure, but also for the initial stage of leveling and aligning[3]. As the teeth are translated, forces develop which may inhibit their movement[4]. The total of these forces is called the “Resistance to Sliding (RS)”[3]. Proffit (2000) reported that about 50% of the applied force necessary to initiate tooth movement is required to overcome (RS)[5]. Resistance to sliding is divided into 3 components: friction, binding and notching[6]. Friction Force is one of the “RS” components and it is defined as the force that resists the relative motion of two contacting bodies in a direction tangential to the plane of contact[7]. There are two main types of friction: static friction which is the smallest force needed to start the motion of solid surfaces which were previously at rest, whereas kinetic friction is the force that resists the sliding motion of one solid object over another[2]. Ceramic brackets have higher friction than metal brackets[8], therefore, companies always try to develop ceramic brackets with a smoother slot surface, rounding of slot base or consisting of metallic slot surfaces.[9]. Most studies focused on “Static Friction” force only. Kinetic friction was not considered because orthodontic sliding of a tooth (bracket) in an archwire is not a continuous motion[9]. From a clinical point of view, overcoming the static friction force between the bracket and the wire is a prerequisite for tooth movement. Furthermore, static friction force is always greater than kinetic friction, whereas static force determines the magnitude of the force system acting on the teeth, irrespective of the possible low levels of kinetic friction force[9]. These ex-vivo studies had used different devices such as: - Zweigle Tensile Testing Machine[10]. - Instron Universal Testing Machine[7]. - Nene M3000, Wellingborough, UK[11]. - EZ-Test Machine[12]. - LR5K (Lloyd Instruments)[13]. All the devices mentioned above are large and expensive, situated in sophisticated research centers, need expert personnel to operate and their software may need frequent updating. In an attempt to overcome such obstacles, we have developed a new device to measure the static friction values for orthodontic studies. This device is smaller than the previous machines, inexpensive and not complicated. Compared with stainless steel brackets, most studies showed that ceramic brackets generate higher frictional forces, which lead to longer treatment duration[9]. Recently, new designs of ceramic brackets that offer excellent optical properties with the promise of an optimal functional improvement were introduced[9]. The Radiance bracket is one of these new designs. It is startlingly clear compared to other ceramic brackets. It benefits from a proprietary heat polishing process that removes flaws from the surface of the bracket and has a smooth, precision slot for easier sliding mechanics[14].Therefore, the aim of this comparative study was to assess the usability of the “New Static Friction Tester” device for friction investigations in orthodontics and to assess the frictional values of the new ceramic bracket (Radiance). Materials And Methods: Static friction values were measured for metal and ceramic brackets with straight stainless steel and nickel titanium wires. Brackets: The following Roth upper-right canine (tooth 13) brackets for (0.022×0.028 inches) slot size and with no hook were tested in this study: Forty stainless steel brackets (Mini Mater, American Orthodontics, Wisconsin, USA), with torque (-2˚), angulation (+10˚) and mesial-distal width of (3.098 mm). Forty ceramic brackets (Radiance Plus, American Orthodontics, Wisconsin, USA), with torque (-2˚), angulation (+10˚) and mesial-distal width of (3.302 mm). Archwires: Each wire was 6 mm in length and had a hook on the end. Forty straight stainless steel wires with (0.019×0.025 inches) dimensions (American Orthodontics, Wisconsin, USA). Forty straight nickel titanium wires (0.018 inch) (American Orthodontics, Wisconsin, USA). Ligation: 80 clear (O-ring) elastomeric (Unistick-Ligatures, American Orthodontics, Wisconsin, USA) with outer diameter of (2.921 mm) and inner diameter of (1.143 mm) were used. A “ligature gun” (Ortho Technology Inc. Tampa, Florida USA) was used to place each elastomeric ring on the bracket wings. The brackets, wires and ligations were divided into eight groups: -Group 1: (10) metal brackets, (10) S.S wires, (10) elastomeric rings. -Group 2: (10) metal brackets, (10) S.S wires, (10) elastomeric rings. -Group 3: (10) metal brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 4: (10) metal brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 5: (10) radiance brackets, (10) S.S wires, (10) elastomeric rings. -Group 6: (10) radiance brackets, (10) S.S wires, (10) elastomeric rings. -Group 7: (10) radiance brackets, (10) Ni-Ti wires, (10) elastomeric ring. -Group 8: (10) radiance brackets, (10) Ni-Ti wires, (10) elastomeric ring. Groups (1-3-5-7) were tested using “The New Tester” device while groups (2-4-6-8) were tested using “The Zweigle Machine”. Two testing machines were utilized: testing with “The New Static Friction Tester” (developed by the authors with the help of a mechanical engineer) and with “The Zweigle Machine” (Zweigle Textilprüfmaschinen GmbH, Ferdinand- Lassalle- Strasse 54, Germany). I-The New Static Friction Tester: This machine was constructed as a simple, inexpensive and easy to use device figure (1). Figure1: The New Static Friction Testing Machine. It was designed (with the help of Ali Kablan, a mechanical engineer) to achieve reliable and easy measurements of the static friction of orthodontic materials. The components of this machine are illustrated in figure (2). Figure2: An illustration shows the components of the New Static Friction Testing Machine. Each combination (bracket, wire and elastomeric ligature) was placed in its special place and the hook of the wire was inserted in the ring of the spring. This ring contacts with the two sensors when the spring is not stretched. To start the work with this device, the motor was connected to the electricity, and then we move the two-direction keys to the top, so the motor starts to operate. - When the motor works, the small roller starts its rotation and it translates the move to the middle roller by the elastomeric ring, then to the big roller. - As the big roller moves, the axis will move inside the two bearings so the helix will move with the arm that holds the indicator and the spring. - The spring starts to stretch and it keeps stretching until the wire moves inside the bracket, then the down side of the spring will move back and the ring will be pulled away from the two sensors and the electricity will cut off immediately. - At that moment, the indicator would be stopped at a given number. - This special number indicates the force that is required to move the wire inside the bracket, i.e., the value of the static friction for this special combination (bracket, wire, and ligation). All tests were conducted under dry conditions and at room temperature (29˚ C). Each bracket was mounted on a metal ring with an outer diameter of (20 mm), and an inner diameter of (15 mm) using (Quick Epoxy Steel) adhesive. The position of the bracket was obtained through preliminary insertion of (0.021×0.028 inch) straight stainless steel wire in the slot of the bracket, without ligation, before bonding so the wire is parallel with the ring diameter. After bonding of the bracket on the metal ring, the S.S wire was removed. Each bracket was tested only once and each wire specimen was drawn through one bracket only, so as to eliminate the influence of wear. In total, 80 test models were constructed, i.e. twenty models for each type of brackets (Mini Master and Radiance). II- The Zweigle F 427 Machine: A tensile testing machine. The hardware and software flexibility allow the machine to be custom designed, so it can perform automatic yarn tests, tests on fabrics and friction tests, figure (3). Figure3: The Zweigle F427 testing machine. The resulting frictional force records on a computer screen. Dimensions and weight (without PC): Width: 660 mm, depth: 485 mm, height: 1585 mm and weight: approx. 60 kg The ring (with the bracket) was mounted on the lower arm of the machine while the wire, with the hooked end, was inserted through a ring mounted on the upper arm. The thickness of the upper ring equals the thickness of the lower ring with the base of the bracket, so the wire was mounted vertically figure (4). The crosshead moved upward at a speed of (0.5 mm/min). Figure4: The upper and lower rings in Zweigle machine. Results: The data were analyzed using statistical software (SPSS) version (18.0). Table (1) provides a statistical summary of static friction data for the two bracket materials and the two devices. Table 1. One-way ANOVA analysis of variance was carried out to determine the effect of the device type and the bracket material on the results. The results are summarized in Tables (2 and 3) and figure (5). Table 2. It can be seen from Table (2) that there are no significant differences between the two devices for all test groups (P>0.05). It can be seen from Table (3) that the metal brackets displayed significantly lower frictional forces (P\u003C0.05) than the radiance brackets for the two wire types. Table 3. Figure5: Friction measurements of “The New Tester” and “The Zweigle Machine”. Discussion: The characteristics of an ideal orthodontic appliance include good esthetics and optimal technical performance. Optimal tooth movement with a fixed appliance requires the use of optimal forces, but these forces need to overcome frictional resistance that is present between the wire, the bracket and the means of ligation[13]. Alignment of teeth during leveling is affected by friction[1] and when closing spaces or reducing moderate overjets using sliding mechanics in clinical orthodontic practice, the significance of frictional force may not always be apparent. However, in those cases where anchorage balance is marginal, or where sliding mechanics fail, frictional forces may result in a loss of anchorage[3], so it is important to study frictional values of different (bracket, wire, and ligation) combinations, especially of the different materials of brackets[13]. Frictional values were always measured using complicated and costly testing machines which might not be affordable to all research centers. For this reason, a new testing machine was designed and constructed in this study to measure static friction for orthodontic purposes. The usability and reliability of this machine were assessed according to the following criteria: 1- The first criterion, precision: ANOVA analysis showed no significant differences between the new device and the Zweigle Testing Machine (P\u003C0.05) for the two types of brackets and the two types of wires tested. This means that “The New Static Friction Tester” has precision results and we can use it to study the static friction values of different (bracket, wire, ligation) combinations. 2- The second criterion, the size of the device: The new device is much smaller than “The Zweigle Machine”, (660 mm, 485 mm, 1585 mm), without the PC, for the Zweigle machine versus (340 mm, 80 mm, 20 mm) for the new device. 3- The third criterion, the weight: The new device is much lighter than the Zweigle machine (60 kg) for Zweigle versus (2 kg) for the new device. 4- The fourth criterion, the ease of use: It is very easy to use the new device, whereas it is too complicated to use the Zweigle machine. The new device just needs to be connected to the electrical source and then to move the key, while the Zweigle (and the other universal machines) needs a special mechanism for fixing the sample, a specialist mechanical engineer for calibration, and a continual updating for the software. An increase in the number of adult patients led to the development of various esthetically superior appliances[9]. Ceramic brackets were introduced to the orthodontic specialty in 1986 and since then have become an integral part of the orthodontists’ armamentarium[7]. Although the esthetics are highly desirable, their high coefficient of friction versus metals has caused concern. In order to reduce frictional resistance, the development of ceramic brackets with a smoother slot surface, rounding of slot bases or consisting of metallic slot surfaces has been accomplished[9]. The Radiance bracket is a new ceramic bracket and no previous study had compared the frictional values of this bracket compared to metal brackets. It is made from a single sapphire crystal, the second hardest mineral known, and has a smooth, precision slot for easier sliding mechanics[14]. This bracket is designed to be the strongest ceramic bracket. Mono-crystalline formation gives Radiance a solid core structure as opposed to the strand structure in polycrystalline brackets[14]. A special heat process is then used to seal the bracket and ensure that no fissures exist in the surface structure. The result is a remarkably strong bracket that is far less likely to fail during treatment[14]. Radiance’s mono-crystalline structure and highly polished surface serve as barriers to undesirable staining elements[14]. However, this newly produced bracket failed to overcome the known shortcomings of ceramic brackets with regard to high frictional values. The results presented here showed that the stainless steel bracket produced significantly lower static frictional resistance than the ceramic bracket. Our findings agree with those of some previous studies[15], Al-Munajed study concluded that ceramic brackets produce higher friction than stainless steel brackets[8]. Tanne found that the ceramic bracket may interfere with smooth sliding between bracket and wire[15]. The difference in friction levels between metal and ceramic brackets could be explained by the ceramic bracket characteristics, such as surface roughness, hardness, and stiffness[16]. Manufacturing process, finishing, and polishing are difficult also; this might explain the granular and pitted surface of the ceramic bracket[16] comparing with the smoother surface of stainless steel bracket, which is clearly visible on SEM images[9]. Clocheret study found that ceramic brackets have higher coefficients of friction than metal brackets[17]. The high friction value of Radiance bracket could be due to its hardness. This bracket is designed to be the strongest possible ceramic bracket[14]. Some studies have failed to detect any differences in frictional forces between ceramic and stainless brackets[18]; other studies found that mono-crystalline ceramic bracket had lower mean frictional forces than stainless steel bracket[19]. However, the differences in the results can be explained by analyzing the different experimental methods employed[19]. Conclusion: This study found that the new static friction device could serve as a reliable device for testing and measuring static friction in orthodontics and it has practical advantages over conventional machines. In addition, a newly developed ceramic bracket (Radians) has higher static frictional values compared with the metal brackets. Reference: 1. Wichelhaus A, Geserick M, Hibst RM, Sander FG. The effects of surface treatment and clinical use on friction in Ni-Ti orthodontic wires. Dental Materials 2005; 21: 938-45. 2. Moore MM, Harrington E, Rock WP. Factors affecting friction in the pre-adjusted brackets. Eur J Orthod 2004; 26: 579-83. 3. Ching LY, Budi K, Grace V, Carla AE, James LD. In-vitro evaluation of frictional resistance between brackets with passive-ligation designs. Am J Orthod Dentofacial Orthop 2007;131: 740.e11-704.e22. 4. Cash A, Curtis R, Majo DG, McDonald F. A comparative study of the static and kinetic frictional resistance of titanium molybdenum alloy Archwires in stainless steel brackets. Eur J Orthod 2004; 26: 105-11. 5. Proffit WR, Fields HW. Contemporary fixed appliances. Contemporary orthodontics, 2nd ed. St. Louis: Mosby; 1993. p. 385-91. 6. Loftus BP, Årtun J. A model for evaluating friction during orthodontic tooth movement. Eur J Orthod 2001; 23: 253-61. 7. Budd S, Daskalogiannakis J, Tompson BD. A study of the frictional characteristics of four commercially available self-ligating systems. Eur J Orthod 2008; 30: 645-53. 8. Al-Munajed MK. A study and an assessment of the frictional forces between orthodontic wire and aesthetic orthodontic brackets. Tishreen University Journal for Research and Scientific Studies-Medical Sciences Series 2008; 30: 52-60. 9. Gautam P, Valiathan A. Ceramic bracket: in search of an ideal. Tends Biomater Artif Organs 2007; 20: 220-28. 10. Obaidi HA, Al-Mukhtar AM. The frictional coefficient comparison between stainless steel and beta-titanium arch-wires ligatured to the stainless steel bracket via different ligatures. Al-Rafidain Dental Journal 2008; 8: 79-82. 11. Redlich M, Mayer Y, Harari D. In vitro study of frictional forces during sliding mechanics of “Reduces Friction” brackets. Am J Orthod Dentofacial Orthop 2003; 124: 69-73. 12. Kao CT, Ding SJ, Wang CK, He H, Chou MY, Huang TH. Comparison of frictional resistance after immersion of metal brackets and orthodontic wires in a fluoride-containing prophylactic agent. Am J Orthod Dentofacial Orthop 2006; 130: 569.e1-568.e9. 13. Griffiths HS, Sherriff M, Ireland AJ. Resistance to sliding with 3 types of elastomeric modules. Am J Orthod Dentofacial Orthop 2005; 27: 670-5. 14. American Orthodontics Catalog \u003Chttp://bit.ly/16gNzQH; 15. Tanne k, Matsubara S, Shibaguchi T, Sakuda M. Wire friction from ceramic brackets during simulated canine retraction. The Angle Orthodontist 1991;61:285-292. 16. Nishio C, Da Motta AF, Elias CN, Mucha JN. In vitro evaluation of frictional forces between arch-wires and ceramic brackets. Am J Orthod Dentofacial Orthop. 2004; 125: 56-64. 17. Clocheret K, Willems G, Carels C, Celis J. Dynamic frictional behavior of orthodontic Archwires and brackets. Eur J Orthod 2004; 26:163-170. 18. Kusy RP, Whitely JQ. Coefficients of friction for arch wires in stainless steel and polycrystalline alumina bracket slots: the dry state. Am J Ortho Dentofacial Orthop 1990;98:300-312. 19. Lee WY, Lim KS. A study on frictional resistance force of orthodontic resin bracket. Korea. J. Orthod 1999;29:107-112. , http://bit.ly/XmYz0j , via كل يوم معلومة من طب الأسنان http://www.facebook.com/photo.php?fbid=446517492097857&set=a.443015215781418.1073741856.157162584366684&type=1