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TITLE OF THE TOPIC:
“A STUDY OF THE STATIC AND KINETIC FRICTIONAL RESISTANCE BETWEEN CONVENTIONAL AND SELF LIGATING LINGUAL BRACKETS AND STAINLESS STEEL WIRES: A COMPARATIVE IN-VITRO STUDY.”
BRIEF RESUME OF WORK:
NEED FOR STUDY:
Lingual Orthodontics is a frequently used approach in the treatment of adult patients.
Lingual brackets are quite different in their configurations and their clinical aspects.
The dimensions of orthodontic brackets are one of the essential parameters determining the critical contact angle (ϴc) value during sliding mechanotherapy.1
The frictional force between the archwire and bracket slot tends to increase rapidly above this angle.2
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the surfaces. Since it is the force perpendicular or "normal" to the surfaces which affects the frictional resistance, this force is typically called the "normal force" and designated by N. The frictional resistance force may then be written:
ffriction = μN
μ = coefficient of friction
μk = coefficient of kinetic friction
μs = coefficient of static friction
Friction is the resistance to motion when 1 object move tangentially against another. A distinction is made between static frictional force—the smallest force needed to start the motion—and kinetic frictional force—the force needed to resist the sliding motion of one solid object over another at a constant speed.
For one object to slide against the other, the force application must overcome the frictional force; higher frictional resistance requires greater orthodontic forces.3
Many studies have evaluated the factors that influence frictional resistance in labial brackets: bracket and wire materials, surface conditions of archwires and bracket slot, wire section, torque at the wire-bracket interface, type and force of ligation, use of self-ligating brackets, interbracket distance, saliva, and influence of oral functions
Very few studies have been carried out in relation to lingual brackets and archwire combinations.
Hence the need for this study is to compare the static and kinetic frictional resistance between conventional and self ligating lingual brackets with stainless steel archwires.
REVIEW OF LITERATURE:
The aim of this in-vitro study was to investigate the frictional resistance resulting 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 angulation. Each bracket type (n = 30) 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 angulation increased. The lowest friction was found with In-Ovation L brackets and 0.016 inch archwires at 0 degrees angulation, and the greatest friction with a combination of STb brackets and 0.017 × 0.025 inch archwires at 10 degrees angulation. For all combinations, Magic and In-Ovation L brackets showed lower frictional resistance when compared with 7th Generation and STb brackets. The slot width (occluso-gingival dimension) of the brackets, measured using the optics of a microhardness machine, showed that all brackets were oversized and that Magic brackets had the largest slot width. Surface roughness of the brackets investigated using atomic force microscopy and scanning electron microscopy, demonstrated that the 7th Generation brackets had the greatest surface roughness.4
In this in-vitro study the resistances to sliding were studied as a function of five angulations (0°, 3°, 7°, 11°, and 13°) using nine different couples made of stainless steel, single crystal sapphire, or polycrystalline alumina brackets against stainless steel, nickel titanium, or beta-titanium arch wires. When couples were in the passive configuration at low angulations, all stainless steel wire-bracket couples once again had the least resistance to sliding. When the angulation exceeded about 3°, however, the active configuration emerged and binding quickly dominated as the resistance to sliding increased over 100-fold. Under these conditions, the relative rankings among the materials transposed; couples of stainless steel had the most resistance to sliding, whereas, couples of the more compliant alloys, such as nickel titanium wire, had the least. Results suggested that the active configuration and subsequent binding emerged when no bracket clearance remained. This binding component increased in importance with angulation and was additive to the frictional component, that is, they followed the principle of superposition.2
This in-vitro study measured and compared the level of frictional resistance generated between stainless steel self-ligating brackets (Damon SL II, SDS Ormco, Glendora, Calif), polycarbonate self-ligating brackets (Oyster, Gestenco International, Go¨ thenburg, Sweden), and conventional stainless steel brackets (Victory Series, 3M Unitek, Monrovia, Calif), and 3 different orthodontic wire alloys: stainless steel (Stainless Steel, SDS Ormco), nickel-titanium (Ni-Ti, SDS Ormco), and beta-titanium (TMA, SDS Ormco). All brackets had a .022-in slot, whereas the orthodontic wire alloys were tested in 3 different sections: .016, .017 .025, and .019 0.025 in.
Stainless steel self-ligating brackets generated significantly lower static and kinetic frictional forces than both conventional stainless steel and polycarbonate self-ligating brackets, which showed no significant differences between them.
Beta-titanium archwires had higher frictional resistances than stainless steel and nickel-titanium archwires. No significant differences were found between stainless steel and nickel-titanium archwires. All brackets showed higher static and kinetic frictional forces as the wire size increased.3
This in-vitro study was done to compare the amount of expressed frictional resistance between orthodontic selfligating brackets and conventionally ligated brackets as reported in the literature. Several electronic databases (Medline, PubMed, Embase, Cochrane Library, and Web of Science) were searched without limits. In vitro studies that addressed friction of self-ligating brackets compared with conventionally ligated brackets were selected and reviewed. A total of 70 papers from the electronic database searches and 3 papers from the secondary search were initially obtained. It was concluded that as Compared with conventional brackets, self-ligating brackets produce lower friction.5
The purpose of this in-vitro study was to determine a new measuring method with a pin on disk friction tester for the measurement of the frictional force between lingual brackets and archwires. Two brands of lingual brackets and one brand of labial standard bracket with an 0.018-inch slot size were used. Archwires of three alloys (stainless steel [SS], Ormco; b-Titanium [TM], Ormco; cobalt-chrome, [EL], RMO) with 0.016 3 0.022- and 0.017 3 0.025- inch dimensions were used. Measurements were conducted with an angular velocity of 0.68/s for 90 seconds and a normal force of 100 g at 258C in a dry and 348C in an artificial saliva environment. For SS and EL archwires, the frictional force with the FJT bracket was greater than that with ORM bracket .Compared with SS and TM archwires, 0.016 X 0.022-inch EL archwire showed a higher frictional force with two lingual brackets . Significant differences in frictional force existed between dry and artificial saliva environments and the effects varied by the bracket-archwire couples. The estimated critical contact angles were greater than the theoretical values.6
AIMS AND OBJECTIVES OF STUDY:
The aim of this study will be to evaluate the frictional resistance between various lingual orthodontic brackets and stainless steel archwires and to relate their respective actual slot size and surface morphology and roughness.
The objectives of this study are:
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To suggest the suitable wire-bracket combination which has the lowest frictional resistance thereby aiding in optimum tooth movement.
MATERIALS AND METHODS:
SOURCE OF DATA:
This study is proposed to be conducted in the DEPARTMENT OF ORTHODONTICS, M R AMBEDKAR DENTAL COLLEGE, Bangalore
MATERIALS:
1. Brackets:
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30 upper premolar Conventional(JOY) lingual brackets from Adenta corp.(USA) of 0.018” slot width.
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30 upper premolar Self ligating(EVOLUTION) lingual brackets from Adenta corp.(USA) of 0.018” slot width.
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30 upper premolar Conventional (STb) lingual brackets from ORMCO Corp(USA) of 0.018” slot width.
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30 upper premolar Self ligating(2D LINGUAL) lingual brackets from Forestadent Corp(USA) ) of 0.018” slot width.
2. Stainless steel wires from 3M Dental Corp.:
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0.016 inch
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0.016 inch X 0.022 inch
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0.017 inch X 0.025 inch
Wire sizes recommended for partial canine retraction and en masse retraction of the anterior teeth are 0.016 and 0.016 × 0.022 inch stainless steel archwires, respectively.
Torque control and ideal tooth positioning should be accomplished with archwire/bracket couples that produce greater frictional resistance at the finishing stage of treatment. For this purpose, 0.017 × 0.025 inch stainless steel or 0.0175 × 0.0175 Beta titanium (TMA) archwires are used.4
3. Ethanol
4.Aluminium jig
5. Bonding agent-Transbond XT
6. Light curing gun(Elipar 2500 -3M ESPE)
7. Universal Testing Machine(INSTRON)
8. Scanning Electron Microscope
METHODOLOGY:
All brackets will be tested at 0 degree second order angulation. The friction tests will be undertaken at room temperature and under dry conditions. Bracket and archwire surfaces will be cleaned with 95 per cent ethanol and each bracket will be bonded on an aluminium plate with a light curing resin in a standardized occluso-gingival position.
Prescription characteristics will be eliminated by supporting the bracket with a full dimension stainless steel wire (0.018 × 0.025 inch).Once the light curing resin will harden, the jig will be removed. The brackets will be positioned at 0 degree second order angulation.
The upper end of the stainless steel wire will be inserted into the tension load cell of the universal testing machine, and a 200 g weight will be attached to the lower end of the wire. The 25 cm wire segment will be then seated into the slots of the brackets.
The ligation force will be standardized at 200 g.
Static and kinetic frictional forces will be measured throughout 2 mm translation of the bracket along the archwire at a crosshead speed of 1 mm/minute.
Each group will contain 30 brackets tested with three different wire sizes divided into the sub-groups A,B and C. The sample size for each archwire/bracket combination will be 10.
During friction testing, the static friction (the peak force required to initiate movement) and kinetic friction (the mean force required to maintain movement) Will be digitally recorded using a software program . The universal testing machine was set to zero and calibrated before each archwire/bracket type/angulation series will be run.
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Surface morphology and roughness.
Before scanning electron microscopy (SEM) observations, all samples will be cleaned with 95 per cent ethanol. Scanning electron micrographs of the received brackets will be recorded using a SEM.
One sample will be chosen from each bracket type and mounted on studs, which will be later placed in the vacuum chamber of the microscope. The accelerating voltage, angle of fit, and the aperture will be adjusted to optimize the quality of the micrograph. The slot surface will be scanned and viewed on the monitor at different magnifications.
ANALYSIS OF DATA:
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Descriptive statistics, including the means, SD, minimum and maximum values will be calculated for each archwire/bracket combination.
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ANOVA will be used to compare the frictional resistances of the different bracket- archwire combinations.
DOES THE STUDY REQUIRE ANY INVESTIGATIONS TO BE CONDUCTED ON PATIENTS OR ON OTHER HUMANS OR ANIMALS? IF SO, PLEASE DESCRIBE BRIEFLY.
Not applicable.
HAS ETHICAL CLEARANCE BEEN OBTAINED FROM YOUR INSTITUTION IN CASE OF 7.4
Yes.
LIST OF REFERENCES:
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Kusy R P, Whitley J Q 1997 Friction between different wire-bracket configurations and materials. Seminars in Orthodontics 3: 166–177
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Articolo L C, Kusy R P 1999 Influence of angulation on the resistance to sliding in fixed appliances. American Journal of Orthodontics and Dentofacial Orthopedics 115: 39–51
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Cacciafesta V, Sfondrini M F, Ricciardi A, Scribante A, Klersy C, Auricchio F 2003 Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations. American Journal of Orthodontics and Dentofacial Orthopedics 124: 395–402
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Ortan YO, Arslan TY, Aydemir B,2012; A comparative in vitro study of frictional resistance between lingual brackets and stainless steel archwires; Eur J Ortho:34;119-125
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Ehsani S, Mandich M A, El-Bialy T H, Flores-Mir C 2009 Frictional resistance in self-ligating orthodontic brackets and conventionally ligated brackets. A systematic review. Angle Orthodontist 79: 592–601
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Park J H, Lee Y K, Lim B S, Kim C W 2004 Frictional forces between lingual brackets and archwires measured by a friction tester. Angle Orthodontist 74: 816–824
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Rajiv Gandhi University of Health Sciences, Bangalore