Evaluation of Frictional Characteristics of Four Commercially Available Self-Ligating Brackets: An In-Vitro Study

Subu, Thomas (2011) Evaluation of Frictional Characteristics of Four Commercially Available Self-Ligating Brackets: An In-Vitro Study. Masters thesis, Ragas Dental College & Hospital, Chennai.


Download (6MB) | Preview


INTRODUCTION: Orthodontic treatment aims to relocate malpositioned teeth within the jaws using application of mechanical forces. Although little is known about the optimal orthodontic force, it is widely assumed that the optimal orthodontic tooth movement occurs under a small and continuous force. During the evolution of the various fully programmed appliances, concomitant improvements and refinements in retraction mechanics resulted in a relatively new procedure called “sliding mechanics”. In orthodontics, the term sliding mechanics implies that there is relative movement between archwire and brackets or tubes. The advantages of sliding mechanics include less complicated wire bending, decreased chair side time and patient comfort, whereas the disadvantage of sliding mechanics is friction and thus slower rate of tooth movement. Friction is the resistance to motion encountered when one solid body slides or tends to slide over another. It may be described as a force acting parallel and opposite to the direction of this motion. Friction is considered to be significant in decreasing the effective orthodontic force available to move teeth thus reducing the efficiency and rate of tooth movement. Self-ligation seems to be gaining more and more popularity in contemporary orthodontics. Compared with conventional appliances, all the commercially available self-ligating mechanisms attribute their increased efficiency and reduced treatment time to their improved frictional characteristics. However, considerable variation exists between commercially available bracket types in terms of their mechanical, geometrical, and material-related specifications and this would be expected to affect their frictional performance. For these reasons it was considered important to test the kinetic frictional behavior of self-ligating brackets and compare that to pre adjusted twin brackets with conventional ligation. Therefore the aim of the present study was to compare the kinetic frictional resistance of four commercially available self-ligating brackets and a preadjusted twin bracket conventionally ligated with elastomeric modules in-vitro with various dimension stainless steel archwire combinations under conditions that would allow replication (from a mechanical standpoint) of the clinical situation. MATERIALS AND METHODS: Materials used in this study: Brackets-Two popular brands in each Active and passive self-ligating bracket systems were selected and one conventional bracket system with elastomeric module ligation served as control. Upper right first premolar stainless steel Roth prescription brackets with slot dimension of 0.022 x 0.028 inches were used in all the 3 groups. Active self-ligating bracket systems: a) Speed – (Strite industries -Canada), b) In-Ovation R (GAC-Dentsply-USA). Passive self-ligating bracket systems: a) Damon 3 - (Ormco orthodontics-California), b) Smart clip - (3 M Unitek-USA). Conventional ligation systema): Mini Ovation - (GAC-Dentsply-USA). Archwires: a) 0.018 inches-A.J.wilcockStainless steel wires of straight length, b) 0.020 inches- A.J.wilcock Stainless steel wires of straight length, c) 0.017 x 0.025 inches-straight length Stainless steel wires (GAC-USA), d) 0.019 x0.025 inches straight length Stainless steel wires (GAC-USA), e) 0.021 x 0.025 inches- straight length Stainless steel wires (GAC-USA), Elastomeric modules: Grey colored ligatures- (GAC-Dentsply-USA) (Fig-2). Testing machine: Autograph AGS-J Series-Load cell capacity of 50 N-(Shimadzu- Corp Japan) (Fig-8). Acetone: to condition the brackets before testing. Study methodology: Two brackets of each type were bonded with epoxy resin adhesive (Araldite, Ciba-Geigy) to color coded acrylic rectangular blocks. The distance between the brackets measured 8 mm corresponding to interbracket width in clinical condition44 (Fig-5). Prior to bracket bonding, a 0.021×0.025 inch diameter straight length wire was secured into the slot of the brackets of the self-ligating groups, and the twin preadjusted brackets as described by Cordasco et al with a specially designed jig which enabled accurate paralleling of the bracket slot to the base of acrylic rectangular blocks (Fig-4). Each bracket and wire was cleaned with Acetone solution to remove any surface impurities before testing. The straightened stainless steel archwires measuring 125 mm, after checking for any surface impurities or irregularities are ligated to the bracketgroups. A universal testing machine was used to determine the frictional force levels in which the entire testing procedure was done in a dry environment. RESULTS: The present study was conducted to evaluate the kinetic frictional resistance of four self-ligating brackets:- two Active types, two Passive types and to compare the values with that of a conventional twin bracket ligated with elastomeric module. The brackets were tested against five different dimensions of round and rectangular stainless steel wires. Thus twenty five bracket archwire couples and two hundred and fifty total readings were obtained. These test readings were statistically analyzed with a one way ANOVA followed by Post HOC Tukey test for multiple comparisons and student T tests. (The level of statistical significance was set at p=0.05. If the value of P>0.05, then the inference is that there is no statistical difference between the variables and a value of P<0.05, implies a statistically significant difference between the variables). The statistical operations were done through SPSS (Statistical Package for Social Sciences Software) for Windows, version 10.0 (SPSS, 1999. SPSS Inc: New York) and formulated in tables and bar diagrams. SUMMARY AND CONCLUSION: In this study we evaluated the frictional resistance of two Active and two Passive Self-ligating brackets and a Conventional twin bracket ligated with elastomeric module with five different dimension of stainless steel wires commonly used in orthodontic practice and to determine which among the two systems exhibit more kinetic frictional resistance. Based on the statistical results derived from this study the following conclusions were drawn a) Between Self-ligating and Conventional bracket systems, Self-ligating brackets offered less frictional resistance. b) Passive bracket systems offer less frictional resistance than Active Self ligating bracket systems and Damon brackets offered the least frictional resistance among all the brackets studied. c) Damon Self-ligating brackets produced less frictional resistance then Smart Clip brackets in the passive group and In-Ovation R produced less frictional resistance then Speed brackets in active group. d) There was an increase in the frictional resistance as the wire dimensions increased. 0.018 inch round stainless steel wire showed the least friction while 0.021 x 0.025 inch rectangular stainless steel wires showed the maximum frictional resistance. e) Conventional twin brackets with elastomeric ligatures which are still popular generate more friction than Self-ligating brackets.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Frictional Characteristics ; Four Commercially Available ; Self-Ligating Brackets ; In-Vitro study.
Subjects: DENTAL > Orthodontics and Dentofacial Orthopedics
Depositing User: Kambaraman B
Date Deposited: 12 May 2018 09:21
Last Modified: 12 May 2018 09:21
URI: http://repository-tnmgrmu.ac.in/id/eprint/7723

Actions (login required)

View Item View Item