|Year : 2020 | Volume
| Issue : 2 | Page : 17-21
Assessment of minimum force required to initiate sliding of stainless steel wire in ceramic (monocrystalline and polycrystalline) and stainless steel preadjusted edgewise brackets using stainless steel and elastomeric ligation techniques – An in vitro study
Krishna Ranpura1, Sangeeta Shah2, Dhaval Somani3, Keyur Soni3, Tilak Parikh4, Sejal Patel4
1 Senior Lecturer, Department of Orthodontics, College of Dental Sciences and Research Center, Ahmedabad, Gujarat, India
2 Professor, Department of Orthodontics, College of Dental Sciences and Research Center, Ahmedabad, Gujarat, India
3 Reader, Department of Orthodontics, College of Dental Sciences and Research Center, Ahmedabad, Gujarat, India
4 Senior Lecturer, Department of Orthodontics, Karnavati School of Dentistry, Gandhinagar, Gujarat, India
|Date of Submission||30-Mar-2020|
|Date of Acceptance||22-Apr-2020|
|Date of Web Publication||27-Jun-2020|
Dr. Krishna Ranpura
Department of Orthodontics, College of Dental Sciences and Research Center, Ahmedabad, Gujarat
Source of Support: None, Conflict of Interest: None
Objectives: To compare the force required to initiate sliding of rectangular stainless steel wire in monocrystalline ceramic bracket v/s polycrystalline ceramic bracket v/s stainless steel bracket using stainless steel ligation technique and to compare the force required to initiate sliding of rectangular stainless steel wire in monocrystalline ceramic bracket v/s polycrystalline ceramic bracket v/s stainless steel bracket using elastomeric ligation technique.
Methods: The archwire was pulled in a vertical direction by the testing machine, until the resistance was overcome and the archwire started to slide through the bracket. The force to overcome resistance and to initiate sliding of the archwire was measured.
Results: In metal brackets, there is minimum resistance to sliding as compared to the two different ceramic brackets. Among the two ceramic brackets polycrystalline bracket offered more resistance to sliding then monocrystalline bracket. Although SS ligation offered less resistance to sliding then elastomeric ligation in all three bracket types, the difference between the two ligation systems is not statistically significant.
Conclusions: In maximum anchorage cases metal bracket along with SS ligation should be used to reduce the frictional resistance, enabling the use of lighter forces and eventually conserving the anchorage.
Keywords: Ceramic bracket, edgewise bracket, monocrystalline, polycrystalline
|How to cite this article:|
Ranpura K, Shah S, Somani D, Soni K, Parikh T, Patel S. Assessment of minimum force required to initiate sliding of stainless steel wire in ceramic (monocrystalline and polycrystalline) and stainless steel preadjusted edgewise brackets using stainless steel and elastomeric ligation techniques – An in vitro study. Int J Prev Clin Dent Res 2020;7:17-21
|How to cite this URL:|
Ranpura K, Shah S, Somani D, Soni K, Parikh T, Patel S. Assessment of minimum force required to initiate sliding of stainless steel wire in ceramic (monocrystalline and polycrystalline) and stainless steel preadjusted edgewise brackets using stainless steel and elastomeric ligation techniques – An in vitro study. Int J Prev Clin Dent Res [serial online] 2020 [cited 2020 Jul 15];7:17-21. Available from: http://www.ijpcdr.org/text.asp?2020/7/2/17/288190
| Introduction|| |
Friction is defined as a force tangential to the common boundary of two bodies in contact that resists the motion or tendency to motion of one relative to the other. During treatment with edgewise appliance, a frictional force is produced at the (bracket/archwire/ligature) interface that tends to contrast the desired tooth movement. Because the efficiency of fixed appliance therapy depends on the fraction of force delivered, high frictional forces due to the interaction between the bracket and the guiding archwire affect treatment outcomes and duration in a negative manner.
Several variables have been demonstrated to affect the magnitude of friction between bracket and wire; these include wire material, wire size and shape, ligature material, ligating force, bracket slot size, bracket width, bracket slot/wire angulations, bracket material, and salivary lubrication. Friction may exist in two forms: static friction, which is the resistance that prevents actual motion, and dynamic (kinetic) friction, which exists during motion. Because orthodontic tooth movement is best accomplished by light physiologic forces of long and constant duration, the preferred material for moving a tooth relative to the archwire should be one that produces the least amount of friction at the archwire/bracket interface and has minimal fluctuation in the amount of frictional forces present in the tooth-moving system.
Ceramic brackets were developed to improve esthetics during orthodontic treatment. In clinical use, however, they have problems including brittleness leading to bracket or tie-wing failure, iatrogenic enamel damage during debonding, enamel wear of opposing teeth, and high frictional resistance to sliding mechanics.
All currently available ceramic brackets are composed of aluminum oxide. Because of their distinct differences during fabrication, two types of ceramic brackets are available, namely the polycrystalline alumina and the single crystal alumina or monocrystalline alumina. The most apparent difference between them is in their optical clarity. Single crystal brackets are noticeably clearer and esthetic than polycrystalline brackets.
Polycrystalline brackets have a higher coefficient of friction than monocrystalline ceramic and stainless steel (SS) brackets. This is due to their rougher and more porous surface. Monocrystalline alumina brackets are smoother than polycrystalline samples. The coefficient of friction of monocrystalline and SS brackets is, however, comparable.
Hence, choosing a bracket material of low coefficient of friction would be of great value to orthodontists, to render their expertise in a more comfortable and speedier manner.
| Materials and Methods|| |
The following materials were used to collect the data:
Sixty pre-adjusted edgewise maxillary premolar brackets (30 for each ligation type) were used of three different materials:
- Metal bracket: Mini Masters series
- Polycrystalline ceramic bracket: 20/40 series
- Monocrystalline ceramic bracket: Radiance series.
Each of the brackets used for the study was the product of a single company. It has slot size 0.022” × 0.028” with (−7°) torque and 0° tip.
- −0.019” × 0.025” straight length SS archwires
- −0.010” ligature wire.
III. Elastomeric modules
- Gray-colored regular modules.
IV. Custom-made jig
V. Instron machine.
For the present study, a total of 180 observations were obtained using different bracket–archwire–ligation assemblies with 30 in each group:
- Metal brackets + SS ligation + 0.019” × 0.025” SS wire
- Polycrystalline ceramic brackets + SS ligation + 0.019” × 0.025” SS wire
- Monocrystalline ceramic brackets + SS ligation + 0.019” × 0.025” SS wire
- Metal brackets + elastomeric ligation + 0.019” × 0.025” SS wire
- Polycrystalline ceramic brackets + elastomeric ligation + 0.019” × 0.025” SS wire
- Monocrystalline ceramic brackets + elastomeric ligation + 0.019” × 0.025” SS wire.
The presentin vitro study evaluated the minimum force required to initiate sliding produced by three different types of brackets (metal, polycrystalline ceramic, and monocrystalline ceramic) and two commonly used ligation methods (SS ligation and elastomeric ligation) using SS archwire (0.019” × 0.025”).
In our study, a custom-made apparatus (jig) was constructed from acrylic to record the resistance to movement of test brackets through a SS 0.019” × 0.025” working archwire. It consisted of a simulated fixed appliance with the archwire in vertical position. Bracket was bonded to the jig with a waterproof adhesive. 10-cm long, straight lengths of 0.019” × 0.025” SS archwire were used. This archwire dimension was chosen because it is the recommended size for sliding mechanics with the 0.022” slot brackets used in the investigation. Maxillary premolar brackets were used, each incorporating −7° torque and 0° angulation.
The specimen population was comprised a total of 180 brackets and 180 wire specimens. All the archwires and brackets were washed in 95% ethanol and air-dried before testing. All testing was done under dry conditions with an Instron universal machine (Instron Corporation, Canton, MA, USA) model no. 5982. The wire was drawn up through the testing apparatus with the crosshead moving at 5 mm/min. The Instron testing machine was zeroed and calibrated before each testing was done. The bracket and wire were held together either with elastomeric ligatures or SS ligatures of 0.010” size and tested in a dry environment. Each bracket was placed in a specially designed testing apparatus that was held from the crosshead of the testing machine. The lower end of the jig was attached to the lower crosshead of the testing machine. The upper part of the wire would then be fixed in the top part of testing apparatus. Care was taken to align the jig so that the archwire is parallel with the vertical framework of the machine.
The archwire was pulled in a vertical direction by the testing machine until the resistance was overcome and the archwire started to slide through the bracket. The force to overcome resistance and to initiate sliding of the archwire was measured. After each test, the testing machine was stopped, the wire and bracket assembly were removed, and a new assembly was placed. This was done for 30 nonrepeated evaluations for each wire–bracket combination tested, totaling to 180 samples.
Recording the force
The values of maximum force required to initiate sliding in grams were recorded for individual combinations of bracket–archwire–ligation assemblies with an Instron -5982 machine.
The results were subjected to statistical analysis using one-way analysis of variance (ANOVA) and an unpaired t-test.
| Results|| |
[Table 1] and [Table 2] show that when elastomeric ligation technique is used, the minimal load (gf) required to initiate sliding of wire differs significantly in three different types of brackets as confirmed by ANOVA and t-test. [Table 3] and [Table 4] also reveal similar findings when SS ligation technique is used in three different types of brackets as confirmed by ANOVA and t-test.
|Table 1: Groupwise comparison between the two bracket types using elastomeric ligation|
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|Table 2: One-way descriptive score (analysis of variance) on comparing different bracket types using elastomeric ligation|
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|Table 3: Groupwise comparison between the two bracket types using SS ligation|
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|Table 4: Groupwise comparison between the two ligation systems using similar bracket|
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In metal brackets, there is a minimum resistance to sliding as compared to the two different ceramic brackets. Among the two ceramic brackets, polycrystalline bracket offered more resistance to sliding. Moreover, there is no significant difference between the two ligation techniques [Table 4].
| Discussion|| |
Friction is defined as the resisting force tangential to the common boundaries between two or more bodies when under the action of an external force; one body moves or tends to move relative to the surface of the other. Whenever sliding mechanics is used for tooth movement in orthodontics, friction occurs at the bracket–archwire interface. Profit (2000) reported that 50% of the force necessary to initiate tooth movement is required to overcome the retarding force generated between brackets, archwire, and ligatures. This implies that only 50% of the force applied reaches the tooth and its supporting tissues causing movement and the rest is lost as friction. Smaller the part of the force that is lost or dissipated as friction, more efficient is the tooth movement.
Slot surfaces of polycrystalline brackets have a coarser surface texture and more prominent surface irregularities than slot surfaces of the SS or single-crystal brackets. Higher frictional values of polycrystalline brackets could be produced by sharp and hard edges created at the intersection of the base and walls of the slot with the external surface of the bracket. These results fully agree with those of previous studies by Russell, and Khambay et al. but did not agree with Guerrero et al. and Pimentel et al.
The two ligation techniques used in the study are selected as they are commonly used techniques. The tables show that SS ligation provided lower resistance to sliding and hence better reduction in the friction although the result was not statistically significant, which is in agreement with the study by Frank and Nikolai.
All friction measurements in this study were obtained from materials in planar apposition, i.e., flat surfaces of rectangular wires were drawn across flat surfaces of bracket slots. Such simple geometry permits an uncomplicated examination of basic differences in frictional resistance of materials since the clinical situation involves binding between brackets and wire, additional measurements at various wire angulations Make it more interesting.
| Conclusion|| |
- The force required to initiate sliding of rectangular SS wire was least in SS bracket and maximum in polycrystalline ceramic bracket using both the ligation techniques (elastomeric ligation and SS ligation technique)
- Among the two commonly used ligation techniques (elastomeric ligation and SS ligation technique), SS ligation technique offered lower resistance to sliding (although not statistically significant)
- If the esthetic requirement of the patient is more than among the two ceramic brackets, the monocrystalline bracket should be preferred as it offers less resistance to sliding, and hence, anchorage can be preserved.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]