Brief resume of the intended study: need for the study

Friction is one of the critical factors that determine the efficiency of orthodontic tooth movement. The friction that is generated in a bracket-archwire combination can be advantageous as well as disadvantageous depending on the stages of treatment, such as space closure. In order to prevent undesired tooth movement and get optimal result, friction must be understood and controlled.

With the emergence of various aesthetic options in orthodontics, lingual brackets are preferred as a cosmetic alternative. So far, few attempts have been made to study the friction of lingual brackets because of their dimensional limitation. Therefore a new type of testing machine is used to evaluate the friction of lingual brackets, which will facilitate orthodontic tooth movement by gradual angular changes.

So the purpose of this study is to evaluate the friction of lingual bracket and its arch wires under wet and dry conditions using a new type of friction testing machine

1. 
   A study¹ was conducted in which five different wire alloys (standard stainless steel, Hi-T stainless steel, Elgiloy blue, Nitinol, and TMA) and five different wire sizes (0.016, 0.016x 0.022, 0.017 x 0.025, 0.018, and 0.018 x 0.025 inch) were examined with respect to three bracket widths (2.2, 3.3, and 4.2 mm) at four levels of retarding force (0, 1, 2, and 3 N). In this study, they have used 0.016 x 0.022 inch stainless steel wire combined with a medium (3.3 mm) or wide (4.2 mm) bracket for an arch-guided mechanism with a 0.018 inch slot. This study reports that narrow brackets intensify friction by enhancing tipping movements and the effective force for stainless steel arch wire was increased up to two folds where as TMA was increased up to six folds to overcome friction with the bracket.
   
2. 
   In another study², the frictional resistance to bodily tooth movement along a continuous arch wire was measured. For the study, a fixed appliance was constructed in vitro to simulate tooth movement in a previously aligned arch. The effect of load, bracket width, slot size, arch wire size, and material were studied. It was found that friction was proportional to applied load and inversely proportional to bracket width. Arch wire dimension and slot size had little effect on friction. Nitinol and TMA (beta-titanium) arch wires produced frictional forces two and five times greater than those of stainless steel.
   
3. 
   According to another study³ Coefficients of friction in the dry and wet (saliva) state for stainless steel, cobalt-chromium, nickel titanium, and beta-titanium wires against either stainless steel or polycrystalline alumina brackets were evaluated. The study shows in the dry state and regardless of slot size, the mean kinetic coefficients of friction were smallest for the all-stainless steel combinations (0.14) and largest for the beta-titanium wire combinations (0.46). In the wet state, the kinetic coefficients of the all-stainless steel combinations increased up to 0.05 over the dry state.
   
4. 
   This study⁴ measures and compares the level of frictional resistance generated between titanium and stainless steel brackets. Both 0.018 and 0.022 inch slot size edgewise brackets were tested with different sizes of rectangular stainless steel wires. The frictional resistance was measured on Instron Universal testing machine (Instron Corp, Canton, Mass) with a 10 pound load cell. The study showed that with the increase in wire size titanium brackets showed lower static and kinetic frictional force, whereas stainless steel brackets showed higher static and kinetic frictional force.
   
5. 
   According to this study⁵, frictional resistance tends to rapidly increase as the angle between a bracket and an archwire increases beyond a critical angle. The study also evaluated influence of artificial saliva on friction. To evaluate friction a new testing machine is used.This new machine was found to useful for measuring ‘frictional force because it can measure the frictional under the conditions of continuous angular change between bracket and archwire dry and wet condition.
   
6. 
   Another study⁶ was conducted to investigate the frictional resistance from a combination of lingual orthodontic brackets (7th Generation, STb, Magic, and In-Ovation L) and stainless steel archwires at 0, 5, and 10 degrees of second-order angulations. Each bracket type was tested with three different sizes of archwires. Static and kinetic frictional forces were evaluated with a universal testing machine. All tested brackets showed higher frictional forces as the wire size and second-order angulations increased. The lowest friction was found with In-Ovation L brackets and 0.016 inch archwires at 0 degrees angulation, and the greatest friction was found with a combination of STb brackets and 0.017 × 0.025 inch archwires at 10 degrees angulations.
   

1. 
   To evaluate the friction generated between two different types of arch wires in lingual brackets with continuous change in angulations by a new testing machine.
   
2. 
   To access the frictional force of lingual brackets and arch wires in wet and dry environment.
   

1. 
   MATERIALS:
   

1. 
   48 Lingual brackets
   
2. 
   2 Types of rectangular Arch Wires of 0.016 x 0.022 inch dimension.
   

• 
  Stainless Steel arch wires of 35mm length.
  
• 
  TMA arch wires of 35mm length.
  

3. 
   Artificial Saliva
   

2. 
   EQUIPMENT:
   

1. 
   Pin On Disk Type Friction Tester Machine
   

1. 
   Brackets will be divided into 2 groups (dry and wet conditions). Each group will be divided in to 2 subgroups (stainless steel and TMA).
   
2. 
   48 lingual brackets, 12 brackets in each subgroup will be evaluated for friction.
   

DRY CONDITION	WET CONDITION
STAINLESS STEEL ARCH WIRES		TMA ARCH WIRES	STAINLESS STEEL ARCH WIRES	TMA ARCH WIRES

3. 
   Brackets will be bonded to metal cylindrical rods by using acrylic resin, to set the zero-torque slot.
   
4. 
   A wire holder will be fabricated with an acrylic resin plate, matching the shape of the specimen container of the friction tester.
   
5. 
   Each arch wire of 0.016 x 0.022 inch dimension will be cut into 35-mm lengths.
   
6. 
   A groove for the arch wire will be made in the wire holder to receive the wire sample.
   
7. 
   After fixing the wire holder in the specimen container with screws, the wire specimen will be inserted in the groove of the wire holder.
   
8. 
   The bracket-bonded metal rod will be inserted and fixed in the pin holder of the friction tester and aligned into a passive relationship with the arch wire specimen.
   
9. 
   Each bracket-arch wire couple will be tested in the dry and artificial saliva environments.
   
10. 
    During the artificial saliva environment evaluation, the specimen container will be filled with artificial saliva.
    

1. 
   Correlation Analysis
   
2. 
   Student’s t test
   
3. 
   Two way analysis of variance
   

1. 
   Lingual brackets of slot width 0.018 inch
   
2. 
   Arch wires of two different alloys are (Stainless steel and TMA) wires used.
   
3. 
   Rectangular arch wires of 0.016 x 0.022 inch dimension and 35mm length are used.
   
4. 
   Pin on disk type friction testing machine.
   
5. 
   Artificial saliva used.
   

1. 
   Round Arch wires are not included in the study.
   
2. 
   Distorted brackets are not included.
   
3. 
   Arch wire of 0.017 x 0.025 inch dimension is not used.
   
4. 
   Minor bent or irregular wires were not included.
   
5. 
   Nickel-titanium arch wire is not used.
   
6. 
   STb brackets are not are not used.
   
7. 
   Labial brackets are not used.
   

• 
  No
  

Not applicable

1. 
   Drescher D, Bourauel C, and Schumacher HA, Frictional forces between bracket and arch wire. AJO-DO 1989 Nov.397 - 404.
   
2. 
   D.C TIDY AND D .ORTH, Frictional forces in fixed appliances. AJO-DO Volume 1989 Sep.249 - 254
   
3. 
   KUSY R P, WHITLEY J Q, AND PREWITT M J. Comparison of coefficients for selected archwire-bracket slot combinations in dry and wet state. Angle Orthod 1991; 61,4:193-302
   
4. 
   KAPUR R, PRAMOD K. SINHA AND RAM S. NANDA. Comparison of frictional resistance in titanium and stainless steel brackets. Am J Orthod Dentofacial Orthop 1999; 116:271-4.
   
5. 
   PARK J H, LEE Y K, LIM B S AND KIM W C. Frictional forces between lingual brackets and archwires measured by a friction tester. Angle Orthod 2004; 74:816-824.
   
6. 
   O RTAN Y O, ARSLAN T Y AND AYDEMIR B. A comparative in vitro study of frictional resistance between lingual brackets and stainless steel archwires.European Journal of Orthodontics 2012; 34:119-125.