Details

Autor(en) / Beteiligte

• G, Arifa N. Khanam

Titel

Effects of Intraoral Aging of Archwires on Frictional Forces

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2016

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• In contemporary orthodontics, many practitioners use sliding mechanics for both aligning irregular teeth and closing extraction spaces. Tooth movement associated with sliding mechanics involves a dynamic relationship among the archwires, brackets and ligation type in the oral environment. Archwires act as gears to move teeth with light, continuous forces. The wires behave elastically to these forces over a period of weeks to months. However, the intraoral use of orthodontic archwires is liable to surface deposits and thus corrosion. These factors affect the surface topography and mechanical properties of the archwires causing an increase in the friction coefficient.A coefficient of friction is a value that shows the relationship between the force of friction between two objects and the normal force between the objects. Friction develops when one moving object (archwire) contacts another (bracket slot/ligature wire) tangentially, resisting movement; thus, reducing the forces applied by treatment appliances. Further, to add to this, is the oral environment wherein the orthodontic arch wires are clinically used. Surface films become the most powerful modifiers of friction; generally, friction tends to be high for very rough or very smooth surfaces. Very smooth surfaces make possible relatively large areas of adhesion that tend to grow during sliding, and very rough surfaces cause high friction because of the contact and interlocking of peaks and valley on their surface.1 The biological variables causing increased friction include the presence of saliva, acquired pellicles, corrosion and plaque which present as an adhesive interference by increased surface tension in the archwires. Friction is considered to reduce the rate of physiological forces applied to move teeth, as these forces are consumed to overcome the surface roughness of the intraoral archwires. Thus, an analysis of the surface characteristics of archwire material after intraoral use could be related to the frictional resistance offered by the material. Of the four major alloys used stainless steel, cobalt-chromium, nickel titanium and betatitanium, stainless steel is the most popular and commonly used archwire in fixed mechanotherapy. The role of the orthodontic wire alloys in frictional characteristics of sliding mechanics has been extensively studied, and it has been reported that stainless steel offers the least frictional resistance when compared to the other orthodontic alloys.2 But, the increased cross-section of the stainless steel wire used during final leveling and alignment phase before retraction exhibits increased archwire stiffness which becomes the controlling factor for frictional resistance.3 Further, there are the popular stainless steel ligature ties or the use of elastic modules to engage the archwire into the bracket slot. Stainless steel ligatures have been suggested to create less friction when compared with elastic ligatures. Also, the passively tied steel ligatures produce lesser frictional resistance than the actively tied stainless steel ligature wires.4,5,6 The sliding technique used to accomplish orthodontic treatment consists of the sliding of the rectangular archwires in the bracket slot of premolar teeth and in the buccal tube of molar teeth, allowing the remaining spaces of the extracted teeth to be closed. The main advantage of the straight wire system is the simplicity of the system because after the levelling phase all bracket slots lie in the same plane. This configuration permits sliding of teeth easier