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Issue 10.4 Virtual Journal of Orthodontics Virtual Journal of Orthodontics http://vjo.it The first on-line, paperless orthodontic journal since 1996 Dir. Resp. Dr. Gabriele Floria DDS Spec. Orthod. Viale Gramsci 73 50121 Firenze Italy fax +390553909014 All rights reserved. Iscrizione CCIAA n° 31515/98 © 1996 ISSN-1128-6547 NLM U. ID: 100963616 OCoLC: 40578647 This Journal has free content and no advertisement since many years. Even if commerce is fine, here we prefer to have no company pressures. If everyone reading this Journal would donate a few euros or dollars, we could publish more, and more often. We know that not everyone can, or will, donate, but that is fine. Please, if you find these pages useful, consider making a donation of €5, €20, €50, or whatever you can, to sustain Virtual Journal of Orthodontics. Thanks, Gabriele Floria VJO Founder i TRIBOLOGY: A NEW FRONTIER IN ORTHODONTICS AUTHORS: 1. Dr. Anitha. A (B. D. S, M. D. S.) Ph. D Scholar and Assistant Professor Department of Orthodontics and Dentofacial Orthopaedics. A. J. Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Mangalore - 575004, Karnataka, India. 2. Dr. Akhter Husain (B. D. S, M. D. S., Diplomat, Indian Board of Orthodontics.) Ph. D Scholar, Professor and Head Department of Orthodontics and Dentofacial Orthopaedics. Yenepoya Dental College, Yenepoya University, Mangalore - 575018, Karnataka, India. 3. Dr. Raghuvir Ballambat (B. E, M. E, Ph. D) Director of Research Department of Mechanical Engineering Manipal Institute of Technology, Manipal University - 576104, Karnataka, India. 4. Dr. Raghavendra Kini (B. D. S, M. D. S) Senior Professor Department of Oral Medicine and Radiology, A. J. Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Mangalore - 575004, Karnataka, India. Address of Correspondence: Dr. Anitha. A (B. D. S, M. D. S.) Ph. D Scholar and Assistant Professor Department of Orthodontics and Dentofacial Orthopaedics. A. J. Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Mangalore 575004, Karnataka, India. Phone No: +91-7259191971; +918242458403; Email: [email protected] Fax: 0824-2224968; 0824-2225541 5. Dr. Nillan Shetty (B. D. S, M. D. S) Senior Professor Department of Orthodontics and Dentofacial Orthopaedics, A. J. Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Mangalore - 575004, Karnataka, India. 6. Dr. Rohan Mascarenhas (B. D. S, M. D. S., Diplomat, Indian Board of Orthodontics.) Ph. D Scholar and Senior Professor. Department of Orthodontics and Dentofacial Orthopaedics. Yenepoya Dental College, Yenepoya University, Mangalore - 575018, Karnataka, India. 7. Dr. Rohan Rai (B. D. S, M. D. S) Professor and Head Department of Orthodontics and Dentofacial Orthopaedics, A. J. Institute of Dental Sciences, Rajiv Gandhi University of Health Sciences, Mangalore - 575004, Karnataka, India. Abstract: Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of principles of friction, lubrication and wear. Friction is a force that retards or resists the relative motion of two objects in contact. In Orthodontics, friction is a clinical challenge which is generated by an archwire and bracket and is influenced by interaction of many variables like the bracket composition, bracket width, interbracket distance, slot size, arch wire, second order angulation, degree of torsion, ligation, and wet and dry environment. The ability to quantify and control friction will lead to less anchorage loss, more predictable tooth movement, and the use of ideal force levels to overcome friction and optimize physiological tooth movement. An understanding of this mechanism is im- Leonardo da Vinci who is considered as perative as this insight enables the Ortho- the Father of Modern Tribology is credited dontist appropriate utilization of orthodon- with formulating some of the first funda- tic biomechanical principles, as well as mentals of friction and also apparently how it pertains to the orthodontic appli- sketched designs for anti-friction bearings. ances. Friction: Keywords: Tribology, Friction, Nanotribology, Biotribology, Archwire-Bracket inter- Friction is a force that retards or resists the face. relative motion of two objects in contact. Introduction: tion and normal force. As the two surfaces Friction is the product of coefficient of fric- The word “Tribology” is from the Greek word tribein, meaning to rub. Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear1,2 (Fig.1). in contact slide against each other, two components of total force arises. The frictional force component (F) and the normal force (N) perpendicular to the contacting surface and to the frictional force component (Fig 2).3 Figure 2: Relationship between friction and contact surface area.3 Frictional force is directly proportional to the normal force such that, F = μN where, - μ = Coefficient of friction i.e. sur- face roughness of material. Figure 1: Components of Tribology - N = Normal force i.e. the force acting perpendicular to the object. 3 Lubrication: Lubrication is the process or technique employed to reduce wear of one or both surfaces in close proximity and moving relative to each other, by interposing a substance called lubricant between the surfaces to carry the load between the opposing surfaces. The interposed lubricant film Nanotribology can be defined as the investigations of interfacial processes, on scales ranging in the molecular and atomic scale, occurring during adhesion, friction, scratching, wear, nano-indentation, and thin-film lubrication at sliding surfaces.5 The need for Nanotribology can be summarized as follows: can be a solid (ex: graphite), a solid/liquid - For advanced health care: to dispersion, a liquid/liquid dispersion (ex: modify surfaces in order to create struc- grease) or exceptionally, gas.4 tures that control interaction between materials and biological systems. Wear: Wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface. Some commonly referred to wear mechanisms include: - Adhesive wear - Abrasive wear - Surface fatigue - For energy conversion and stor- age: nanoscale carbide coatings, selfassembled layers for friction control, materials performances at nano- and MEMS scale as a function of aging. For in-situ lubrication study and control. - Microcraft space exploration and Industrialization: to make self repairing materials and self-replicating, biomemmetic materials and nanoscale devices which can sustain any need for movement of sliding surfaces for long periods under severe - Fretting wear conditions. - Erosive wear What is Biotribology? What is Nanotribology? In the human body many tissues move in relation to one another, and the body has to allow for that movement or 4 the tissue will split and break down. It is a fect the outcome of in vitro frictional multidisciplinary field of research involving studies.9,10 The nature of friction in ortho- biology, orthopaedics, biomaterials, sci- dontics is multi-factorial, derived from both ence and tribology and thus a study of fric- a multitude of mechanical or biological fac- tion, wear and lubrication of biological tors. Numerous variables have been as- systems.6 Presently its significance lies in sessed using a variety of model systems the following fields: with nearly equally varying results. Methods to evaluate the Tribological char- - - Making hip replacements last. Maintaining the blood flow with the help of LVAD device. - Ocular tribology - Dental tribology Role of Tribology in Orthodontics: acteristics of the existing Orthodontic systems: - Pin on Disc Tribometer: It con- sists of a stationary "pin" under an applied load in contact with a rotating disc. The pin can have any shape to simulate a specific contact, but spherical tips are often used to simplify the contact geometry.11 In Orthodontics, Tribology plays a very im- Coefficient of friction is determined by the portant role in the performance, reliability, ratio of the frictional force to the loading efficiency and optimization of the orthodon- force on the pin. The pin on disc test has tic systems. Studies of the myriad of pa- proved useful in providing a simple wear rameters, such as bracket composition, and friction test for low friction coatings. bracket width, interbracket distance, slot size, arch wire type, arch wire size, second order angulation, degree of torsion, liga- also be used to draw conclusions on ideal tion, and wet or dry environment, have requirements for improving the effective- helped our understanding by identifying ness of Orthodontic systems. trends or patterns of friction.7,8 The orthodontic literature notes numerous variables that affect the levels of friction at the bracket-archwire interface. In addition, experimental protocol and design often af- - - A Universal Friction Tester12 can Finite element analysis (FEA) is a computer based numerical technique for calculating the strength and behavior of materials. Until the early 1970’s FEA was limited to aeronautics, automotive, de5 fense and nuclear research. However, the ity of the clinician to activate the orthodon- present day computers are now able to tic appliance so that it behaves in a predict- handle FEA for different applications. In Or- able manner. Therefore, the clinician thodontics FEM13 has been used for study- should be aware of the characteristics of ing stress distribution in the teeth, perio- the orthodontic appliance that contribute dontal ligament and in the Orthodontic ap- to friction during sliding mechanics and pliances. Orthodontic bracket systems and the extent of the amount of force expected appliances have been modeled and stud- to be lost to friction. This will help allow effi- ied to understand how the materials would cient reproducible results to be achieved. act under various biological conditions. - References: A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with electrons in the sample, producing various signals that can be detected and which contains information about the sample's surface topography and composition.14 This principle can be used to study the surface roughness and surface changes of the given materials. Conclusion: Friction is not likely to be eliminated from materials, thus the best remedy is to control friction by achieving two clinical objectives: maximizing both the efficiency and the reproducibility of the orthodontic appliances. Efficiency refers to the fraction of force delivered with respect to the force applied, while reproducibility refers to the abil- 1. David T. Biographical Memoirs of Fellows of Royal Society, 2005;54:425. 2. Dowson. D. History of Tribology, Longman Group Ltd., London, 1979. 3. Emile R, Lorne K, Robert K. A fundamental review of variables associated with low velocity frictional dynamics. Semin Orthod, 2003:9(4):223-225. 4. Beinkowski, Keith. Coolants and Lubricants, The truth. Manufacturing Engineering. March, 2003. 5. Richie K, Sahil S. Friction on the nanoscale: new physical mechanisms. Materials Letters, 1999;38:360-66. 6. Anne J. Biotribology: The Tribology of living tissues. Lubrication and Technology, 2003:33-38. 7. Emile R. Friction: An overview. Semin Orthod, 2003;9(4):217-90. 8. Kusy RP, Whitley JQ. Friction between different wire-bracket configurations and materials. Semin Orthod 1997;3:166-177. 9. Drescher D, Bourauel C, Schumacher HA. Frictional forces between bracket and arch wire. Am J Orthod Dentofac Orthop 1989;96:397-404. 10. Wichelhaus A, Geserick M, Hibst R, Sander FG. The effect of surface treatment and clinical use on 6 friction in NiTi orthodontic wires. Dent Mater 2005;21:938-945. 11. Surowska B, Walczak M, Bienia J. Application of the sol-gel coatings in dental prosthetics. Achievements in Mechanical and Material Engineering (Conf. proceed.)2012. 12. Drescher D, Bourauel C, Schumacher HA. Frictional forces between bracket and arch wire. Am J Orthod Dentofac Orthop 1989;96:397-404. 13. Kojima Y, Fukui H. Numeric simulations of en-masse space closure with sliding mechanics. Am J of Dentofac Orthop 2010;138(6)702-04. 14. Doshi UH, Bhad-Patil WA. Static frictional force and surface roughness of various bracket and wire combinations. Am J of Dentofac Orthop 2011;139(1)749. 7