|DENTAL SCIENCE - RESEARCH ARTICLE
|Year : 2015 | Volume
| Issue : 5 | Page : 116-120
Comparison of frictional resistance of esthetic and semi-esthetic self-ligating brackets
MS Kannan, RV Murali, S Kishorekumar, K Gnanashanmugam, V Jayanth
Department of Orthodontics, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu, India
|Date of Submission||31-Oct-2014|
|Date of Decision||31-Oct-2014|
|Date of Acceptance||09-Nov-2014|
|Date of Web Publication||30-Apr-2015|
Dr. M S Kannan
Department of Orthodontics, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The frictional resistance encountered during sliding mechanics has been well established in the orthodontic literature, and it consists of complex interactions between the bracket, archwire, and method of ligation the claim of reduced friction with self-ligating brackets is often cited as a primary advantage over conventional brackets. This study was done to compare and evaluate the frictional forces generated between fully esthetic brackets and semi-aesthetic self-ligating brackets, which are of passive form and SEM (scanning electron microscope) study of the Brackets after Frictional evaluation. Materials and Methods: Two types of self-ligating esthetic brackets, Damon clear (Ormco) made of fully ceramic and Opal (Ultradent Products, USA) and, Two types of self-ligating semi-esthetic brackets, Clarity SL (3M Unitek) and Damon 3 (Ormco) both of which are made of ceramic with metal slot. Arch wires with different dimensions and quality 17 × 25, 19 × 25 Titanium Molybdenum Alloy (TMA) and 17 × 25, 19 × 25 stainless steel that came from plain strands of wire were used for frictional comparison test. The brackets used in this study had 0.022 × 0.028 inch slot. Results: The statistical tests showed significantly smaller amount of kinetic frictional forces is generated by Damon 3 (semi-esthetic self-ligating brackets). For each wire used, Damon 3 displayed significantly lower frictional forces (P ≤ 0.05) than any of the self-ligating system, followed by Opal (fully esthetic self-ligating brackets) which generated smaller amount of frictional forces but relatively on the higher side when compared with Damon 3. Damon clear (fully esthetic self-ligating brackets) generated the maximum amount of kinetic forces with all types of wire dimensions and properties when compared to the other three types of self-ligating system. Clarity SL (semi-esthetic self-ligating brackets) generated smaller amount of frictional forces when compared with Damon clear and relatively higher amount of frictional forces when compared to Opal and Damon 3
Keywords: Esthetic self-ligating, frictional forces, self-ligating brackets, semi-esthetic self-ligating
|How to cite this article:|
Kannan M S, Murali R V, Kishorekumar S, Gnanashanmugam K, Jayanth V. Comparison of frictional resistance of esthetic and semi-esthetic self-ligating brackets. J Pharm Bioall Sci 2015;7, Suppl S1:116-20
|How to cite this URL:|
Kannan M S, Murali R V, Kishorekumar S, Gnanashanmugam K, Jayanth V. Comparison of frictional resistance of esthetic and semi-esthetic self-ligating brackets. J Pharm Bioall Sci [serial online] 2015 [cited 2019 May 24];7, Suppl S1:116-20. Available from: http://www.jpbsonline.org/text.asp?2015/7/5/116/155852
The first self-ligating edgewise bracket Russel lock was introduced by Stolzenberg to orthodontists 75 years ago, since then advances in further bracket technology have resulted in a number of new self-ligating bracket "systems" and greater interest in their use. Much of this interest is in response to information comparing the benefits of self-ligating systems with conventional edgewise brackets. The claim of reduced friction with self-ligating brackets is often cited as a primary advantage over conventional brackets. Two different types of self-ligating brackets were produced: Those with a spring clip that pressed actively against the archwire, such as the speed bracket, and self-ligating brackets, e.g. the Activa bracket (A Company, San Diego, California) whose self-ligating clip did not press against the wire. Passive and active self-ligating appliances with many ligating mechanisms were introduced to allow presumably for efficient sliding mechanics.
Self-ligating brackets are proposed to have the potential advantages of producing more physiologically harmonious tooth movement by not overpowering the musculature and interrupting the periodontal vascular supply.
The frictional resistance encountered while sliding mechanics has been well established in the orthodontic literature, and it consists of complex interactions between the bracket, archwire, and method of ligation. Tooth movement associated with sliding mechanics has been described as a series of short steps involving oscillating tooth tipping and uprighting, rather than a continuous, smooth, gliding process.
Adherence to the tenets of evidence-based orthodontic practice requires that, for any orthodontic intervention applied to a patient, three factors must be integrated: The relevant scientific evidence, the clinician's expertise, and the patient's needs and preferences. On the topic of self-ligating bracket systems, the current challenge for the clinician is to assess the merit of the assertions supporting the superiority of self-ligating brackets.
Aims and Objectives
The aim of the study was to compare and evaluate the frictional forces generated between fully aesthetic brackets and semi-aesthetic self-ligating brackets of the passive form.
| Materials and Methods|| |
An experimental model reproducing the right buccal segment of the maxillary arch was used to assess the frictional forces produced by Two types of self-ligating aesthetic brackets, Opal (Ultradent Products, USA) [Figure 1]a made of a glass filled, polycrystalline resin and Damon clear (Ormco) [Figure 1]b made of fully ceramic. Two types of Self-ligating semi-aesthetic brackets, Damon 3 (Ormco) [Figure 1]c and Clarity SL (3M Unitek) [Figure 1]d both of which are made of ceramic with metal slot. Arch wires with different dimensions and quality 17 × 25, 19 × 25 TMA and 17 × 25, 19 × 25 stainless steel (SS) that came from plain strands of wire were used for frictional comparison test. The brackets used in this study had 0.022 × 0.028 inch slot and were passive form. All the five brackets of the upper right side of the quadrant were used (central-premolar).
The brackets were fixed on to an acrylic block using cyanoacrylate glue with interbracket distance of 6 mm [Figure 2], [Figure 3], [Figure 4] and [Figure 5]. A 16 cm long wire of each type was tested. The wire was secured into the brackets by using the self-ligation system. Each wire was tested for 5 times with a new set of brackets every time. The frictional force generated by the testing unit consisting of wire and brackets was measured under dry condition and at room temperature of 20°C. Friction was tested using Instron Universal Testing Machine model no. 3369 UK with a load cell of 10 N, [Figure 6]. The acrylic block was fixed to the clamp; the test wire was ligated with the bracket and one end of the wire was fixed.
A total of 80 tests (20 tests for each of the four types self-ligation system) were carried out. Kinetic friction forces were recorded while 15 mm of wire were drawn through the brackets at a speed of 15 mm/min. Software used in frictional evaluation is Bluehill software, Instron, UK.
Descriptive statistics, including means, medians, and standard deviations values were calculated for the kinetic frictional forces produced by the four types of self-ligation systems with the four types of wires[Table 1]. The comparisons between the ligation systems were carried out with the analysis of variance on ranks with the Tukey post-hoc test (P ≤ 0.05) Statistical Package for the Social Sciences (SPSS), IBM, USA software, version 15.
| Results|| |
The statistical tests showed significantly smaller amount of kinetic frictional forces is generated by Damon 3 (semi-aesthetic self-ligating brackets). For each wire used, Damon 3 displayed significantly lower frictional forces (P ≤ 0.05) than any of the self-ligating system, followed by Opal (fully aesthetic self-ligating brackets) which generated smaller amount of kinetic forces but relatively on the higher side when compared with Damon 3. Damon clear (fully aesthetic self-ligating brackets) generated the maximum amount of kinetic forces with all types of wire dimensions and properties when compared to the other three types of self-ligating system. Clarity SL (semi-aesthetic self-ligating brackets) generated smaller amount of frictional forces when compared with Damon clear and relatively higher amount of frictional forces when compared to Opal and Damon.
| Discussion|| |
In general Damon 3 produced the lowest frictional forces among the four types of self-ligating brackets used in this study. Opal self-ligating brackets produced much lesser amount of frictional forces compared to Clarity SL and Damon clear self-ligating Systems.
Comparison by wire dimension and quality with four types of bracket shows that 19 × 25 SS, 17 × 25 SS and 17 × 25 TMA showed least frictional forces with Damon 3 and Opal self-ligating brackets. 19 × 25 TMA showed least frictional forces with Opal brackets(Opal Orthodontics, By Ultradent Products, USA). Frictional resistance between archwire and brackets is caused by many factors and varies according to archwire size and material, mode of ligation, angulation of the wire to the bracket and saliva. Drescher et al. regarded bracket width to play an inferior role in frictional forces.
In this study, friction was tested under dry conditions. The effect of lubrication by saliva on friction is controversial. Kusy et al. for example, regarded artificial saliva as inadequate replacement for human saliva and hence such experiments as invalid. Andreasen and Quevedo  claimed that saliva played an insignificant role, while Read-Ward et al. concluded that the presence of human saliva had an inconsistent effect on static friction and sliding mechanics.
Baker et al.  found that saliva acted as a lubricant while Stannard et al.  reported that saliva increased friction. Thus, in the present investigation the wire/bracket couples were tested under dry conditions.
However studies, despite with similar testing conditions, the results found to be not confirmed. During the investigation of the frictional properties of the speed self-ligating bracket compared with a conventional bracket, authors reported increased friction for the self-ligating speed bracket,  Henao and Kusy  2005. One reason for this finding may be the fact that the effect of humidity and temperature in the oral cavity was not simulated. More important, is the fact that the different results are likely to be caused by the particular design of the speed bracket. With this bracket, the wire is actively engaged by a spring clip and pressed into the slot so that a certain amount of pressure proportional to the size of the wire is exerted. In contrast, the locking cap in aesthetic self-ligating brackets just passively converts the bracket slot into a tube, and hence, no pressure is exerted on the wire.
In this study, torque effects (third-order angulation) were not simulated. Even though torque effects increase friction in clinical situations, only a few studies simulating this effect are found in literature Drescher et al., 1991;  Bourauel et al. 1992.  Generally, friction appears to intensify with the increase of archwire diameter Angolkar et al., 1990,  Ireland et al., 1991  a finding supported by the results of the present study. For all bracket types, the 0.019 × 0.025 inch SS wire produced higher friction than the 0.017 × 0.025 inch SS wire. All the four types of self-ligating brackets used in the test regimen produced higher frictional forces in combination with the 0.019 × 0.025-inch TMA wire than with the SS wire of the same dimension. This difference was significant (P ≤ 0.05). These high frictional forces are caused by the surface properties of the TMA wires. TMA has more porosities and a noticeably rougher surface than SS. These findings are in agreement with those of Angolkar et al. and Drescher et al.,  who also observed higher frictional forces with TMA wires compared with SS wires.
Studies have proved that ageing of opal self-ligating brackets has showed a significant increase in frictional qualities Reicheneder et al.  With all types of archwires, aged Opal brackets exhibited greater frictional forces than new Opal brackets. This increase was significant for Opal brackets aged for 9-10 and 18-20 months with respect to SS wires. The negative influence of ageing on frictional behaviour may be due to abrasion of bracket material caused by alternate warm and cold cycles in the chewing simulator. This wear and tear resulted in increased surface roughness and probably in an accumulation of debris in the slot, which, in turn, increased friction. The results are in accordance with those of Riley et al.,  who found that friction of polycarbonate brackets gradually increased in distilled water due to corrosion, and the results of the study by Keith et al. on ceramic brackets.
The current study results support previous investigation by Reicheneder et al.  by Sims et al.,  Read-Ward et al., and Thorstenson and Kusy,  who also found self-ligating brackets to produce significantly less friction than conventional brackets. Schumacher et al. also reported reduced friction with Damon SL self-ligating brackets in comparison with conventionally designed brackets, despite the fact that this decrease was associated with negative side-effects in terms of levelling losses after completion of retraction.
Small differences in the torque prescriptions between the active and passive brackets were not expected to influence the outcome because these were outweighed by the large free play that was more than 2 times higher than the torque differences in a conventional bracket. Randomized controlled trial with the body of evidence on this issue suggest that the bracket-archwire free play might not be the most critical factor in altering the tooth movement rate. This situation, however, changes drastically as treatment progresses, and wires of higher stiffness are engaged in the bracket. Correction of rotations and achievement of proper buccolingual crown inclination (torque), which are frequently required in mandibular and maxillary anterior teeth, respectively, necessitate a couple of forces. This assumes the formation of contacts of wire inside the bracket slot walls, and thus the major advantage of self-ligating bracket free play is eliminated as the crowns gradually attain their proper spatial orientation.
Especially for torque application, self-ligating brackets lose more torque compared with conventional brackets, whereas a clinical trial showed that these brackets can achieve comparable torque transmission only with a reverse curve of Spee archwires. Alternatively, torquing auxiliaries, higher torque prescription brackets, or pretorqued wires can be used to counteract the greater torque loss from greater free play.
This investigation demonstrated clearly that minimal amounts of friction are generated with four types of passive self-ligating brackets that are commercially available. The literature reports values of frictional forces for active self-ligating brackets that are 5 times greater than passive self-ligating brackets.
| Conclusion|| |
This (in vitro) study measures the frictional properties of different aesthetic brackets and semi-aesthetic self-ligating brackets. The results demonstrate a difference in the friction produced by self-ligating aesthetic and self-ligating semi-aesthetic brackets. Self-ligating semi-aesthetic brackets had a smaller amount of friction when compared to aesthetic self-ligating brackets. Among the four types of self-ligating brackets Damon 3 showed the least amount of frictional forces. The difference was significant (P ≤ 0.05). TMA wires demonstrated more frictional forces than SS wires in all the four types of self-ligating brackets. Opal self-ligating brackets showed the least amount of friction with 19 × 25 TMA wire compared to other four types.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]