1.self ligating brackets past present future of orthodontics

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JOURNAL OF DENTAL SCIENCES Volume 2 Issue 1

SELF-LIGATING BRACKETS :PAST, PRESENT & FUTURE OF ORTHODONTICS

Address for Correspondence :Dr. Aakash ShahDept. of Orthodontics & Dentofacial OrthopaedicsFaculty of Dental Science, Dharmsinh Desai University,NADIAD - 387 001. GUJARATPHONE:079-27681666 E-MAIL: [email protected]

Dr. Aakash Shah

Dept. of Orthodontics & Dentofacial OrthopaedicsFaculty of Dental Science, Dharmsinh Desai University,NADIAD - 387 001. GUJARAT

Professor

Introduction :

A self -ligating bracket is a ligature less system with a mechanical device built-in to close-off the bracket slot. Secure engagement of the main archwire into bracket may be produced by a clip mechanism replacing the stainless steel or elastomeric ligature.

Both active and passive self-ligating brackets have been developed depending upon the bracket & archwire interaction. The active type has a spring clip that presses against the arch wire (In ovation R*, or Speed**). In the passive type, the clip or rigid door does not actively press against the arch wire (Smartclip***, Damon 3MX****).

History of Self-ligating Appliances :stThe concept of self-ligating brackets was 1 described in

11935 with the Russell- Lock edgewise attachment. At that time, operator efficiency was the main advantage advocated. A dramatic peak in the popularity of self-ligation occurred in the 1990’s; by than many refinements in self- ligating systems had arrived and also made patented. Recent products include Smartclip 3, In ovation C and Damon 3MX.

Illustration 2 – Self ligating ceramic brackets

Table-1

History of Self Ligating System

System Year Introduced

Russell Lock 19352Edgelok (Ormco) 1972

Mobil Lock (Forestadent) 19803Speed (Strite Industries) 1980

4Activa (“A” Company) 1986Time (Adenta) 1994

5Damon SL (“A” Company) 1996Twinlock (Ormco) 1998Damon 2 (“A” Company/Ormco) 2000In Ovation (GAC) 2000In Ovation R (GAC) 2002Philippe (Forestadent) 2002Smartclip (3M Unitek) 2004Sure (Denrum) 2005Quick (Forestadent) 2005Damon 3MX (Ormco) 2006Smartclip 2 (3M Unitek) 2006In Ovation C (GAC) 2006Clarity SL (3M Unitek) 2007

10Smartclip 3 (3M Unitek) 2009

Abstract :

Self-ligating brackets have been gaining popularity over the past several decades. The purpose of this article is to search previous orthodontic literatures and databases with regard to the efficiency, effectiveness & stability of treatment with self-ligating brackets.

Keywords - Self-ligating bracket, friction, robust-ligation.

Illustration 1 – Conventional ceramic bracket with elastomeric ligature ties.

**********

Trademark of GAC InternationalTrademark of Strite Industries Ltd.Trademark of 3M UnitekTrademark of Ormco/”A” Company

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Advantages of Self-ligating Preadjusted Edgewise System :

1) Secure & robust ligation2) Reduced friction3) Enhanced efficiency & ease of use4) Reduced overall treatment time5) Efficient alignment of severely irregular teeth.6) Better plaque control & anchorage conservation7) Reduced risk of operator & patient injury including

“Puncture Wounds”.

Following potential advantages were further searched in the literatures :-

(i) Secure, robust ligation and fully bracket engagement :-

The shortcomings of elastomeric materials are well known. 6Taloumis and Colleagues , in an invitro study, demonstrated

high decay rates of elastomeric forces within 24 hours. Dowling & Colleague’s study showed a similar reduction in strength of elastomeric modules.

Degradation of elastomeric ligature ties has been found to cause a significant loss of full bracket engagement. A figure-8 elastic ligature tie seems to make arch wire ligation more secure, but this improvement comes at the expense of increased frictional resistance, which may be on the order of 70-220%.

Full, robust arch wire engagement is assured in self -ligating system unless the clip or slide mechanism fails. There is no problem of decay of the ligature as with elastic ligatures.

Table-2Friction in different type of brackets

STUDY HIGHEST FRICTION INTERMEDIATE FRICTION LOWEST FRICTION

Table-3Reduced chairtime required for archwire removal & insertionwith self-ligating appliances as compared to conventional appliances.

8Maijer& Smith SPEED Elastomerics 7 minutes

Shivapuja & Berger Activa, Edgelok Wire ligatures 12 minutesSPEED

Voudouris Interactwin Elastomerics 2.5 minutes

Berger & Byloff SPEED Elastomerics 2-3 minutes

Turnbull & Birnie Damon 2 Elastomerics 1.5 minutes

STUDY SELF LIGATING SYSTEMCONVENTIONAL

MODE OF LIGATIONTIME SAVINGS

However, 50% patients have reported slide mechanism breakages in cases where Damon SL brackets were used. But introduction of newer systems like clip mechanism has virtually eliminated such problems.

(ii) Reduced Friction :-

Very low friction with self ligating brackets has been clearly demonstrated and quantified in work by various authors.

9Bednar & Colleagues showed that elastomerics introduced more friction into the appliance system than stainless steel

7ligatures. Shivapuja & Berger confirmed this finding, reporting that wire ligating produced only 30-50% of the frictional forces as compared to elastomerics. Meling & Colleagues came to similar conclusions. The passive self-ligating appliances (Damon, Smartclip) typically have lower friction than the active systems. (In Ovation R, Speed).

A reduced friction appliance produces more rapid, efficient alignment, rotational corrections and space closure and thus it is also very less taxing on the anchorage.

(iii)Efficiency & Ease of use :-

Self- ligation system results in a consistent reduction in chairtime for fixed appliance adjustment compared to conventional appliances.

In SHIVAPUJA & BERGER study, the use of wire ligatures added almost 12 minutes to the time needed to remove & replace two arch wires. The time saved in self-ligating system (chairside) could be used to schedule more patients, increase efficiency, improve patient relations, or allow oral hygiene reinforcement.

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(iv) Reduced overall treatment time :-

A study of treatment efficiency by self-ligating brackets by Harradine found the following :

• A mean reduction of four months in treatment time.

• A mean reduction of four visits during active treatment.

D. Robust Fry in a presentation at the AAO Annual Session in Toronto 2001 reported similar 4 months reduction in treatment times.

A study by Eberting et al found an average reduction in treatment time of 7 months and 7 visits for self-ligating brackets compared to conventional ligation.

These reports suggest a clinically significant improvement in treatment efficiency with self-ligating brackets.

(v) More efficient alignment :-

Miles compared the alignment efficiency of self-ligating brackets and conventional twin brackets in two studies. In his first study, he noted that 0.7 mm more irregularity remained after initial alignment in the group treated with self-ligating (Smartclip) appliance than in a group treated with conventional twin bracket; this he attributed to the rotational play of 6.8” allowed by the passive self-ligating system.

In a second study, which was a split mouth study design, Miles and Colleagues found that twin bracket had achieved an irregularity index 0.2 mm less than that of self-ligating brackets (Damon 2 brackets). Again, this was attributed to the initial 0.014” nickel titanium, with the potential for greater rotational play.

These findings suggest that any time savings arising from the use of self-ligating brackets do not occur in the initial alignment phase of treatment.

(vi) Improved Patient Comfort :-

Wire ligatures require careful tucking in of the ends to avoid soft tissue trauma, and can occasionally be displaced between appointments and cause discomfort. In self- ligating brackets, there is no chance of poking into patient’s soft tissue as there is no ligation.

Torque Expression :-

The influence of bracket type on torque expression in the upper segment has been assessed in a randomized controlled trial. The Damon 2 appliance was found to be equally capable of torque delivery, relative to the SN & NA lines, compared to a conventional bracket system.

Little difference in mandibular incisor inclination change was reported in a prospective clinical trial of Smartclip & conventional brackets. Incisor proclination of 4.410 and 4.320 occurred in the respective groups during arch leveling & alignment; incisor production was governed largely by the initial incisor inclination and the degree of crowding resolved during the study period. An active self-ligating appliance that presses the wire into the base of the bracket may facilitate more effective torque expression with undersize archwires than can be achieved with a passive self-ligating system.

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• failure to provide and to maintain full archwire engagement results in poor control of tooth movement.

• frictional values are increased

• for elastomerics, the force decays and therefore tooth control is not optimal.

• Both wire and elastomeric ligatures sometime become displaced.

• Oral hygiene is potentially impeded.

• Wire ligation is a time-consuming clinical procedure.

Self ligation offers significant improvements relative to all of these factors.

uFeature of self-ligatiing brackets available in Market.

(A) Speed brackets :

Speed brackets (Strite Industries Ltd., 298 Shepherd Avenue, Cambridge, Ohtario, N3C IVI Canada, Illustration - 3) have remained in successful production since 1980. Earlier brackets had clips which could too easily be displaced or distorted . These drawbacks have been taken care of. These brackets doesn’t have the familiar tie-wings

Illustration 3 – Speed bracket

(B) Activa brackets :

Activa brackets (“A Company, San Diego, CA, Illustration - 4) had a rotating slide, which therefore gave a concave inner radiaus to the labial surface of the slot. These increased slot depth reduced the labiolingual alignment efficiency. The bracket is wider than the average bracket, which reduced the inter-bracket span with the consequent disadvantages. Tie-wings were absent and a different bonding base made bracket positioning more difficult.

Illustration 4 – Active bracket

Limitations of Conventional Ligation

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(C) Time 2 bracket :

The time 2 bracket (Adenta Gmbh, Illustration - 5) has a clip that rotates into position around the gingival tie wing and rotates towards the occlusal rather then the gingival wall of the slot.

Illustration 5 – Time 2 bracket

(D) DAMON SL Brackets :

Damon SL brackets (“A Company, San Diego, CA, Illustration - 6) had a slide that wrapped around the labial face of the bracket. Launch of Damon brackets in mid 1990s made a definite step forward in popularity of self-ligating bracket. Damon SL brackets had two significant problems— the slides sometimes opened inadvertently and they were prone to breakage.

Illustration 6 – Damon SL bracket

(E) DAMON 2 Brackets :

Damon 2 brackets (Ormco Corp. Illustration - 7) were introduced to address the imperfections of Damon SL. Combined with the introduction of metal injection molding manufacture & slight design changes, Damon 2 brackets are almost completely free from inadvertent slide opening or slide breakage. However, the brackets were not immediately and consistently very easy to open.

Illustration 7 – Damon 2 bracket

(F) DAMON 3 and DAMON 3MX Brackets :

Damon 3 and Damon 3MX brackets (Ormco corp. Illustration - 8) have a different location and action of the retaining spring, and this has produced a very easy and secure mechanism for opening and closing. In addition, Damon 3 brackets are semi-esthetic. However, early production of Damon 3 brackets suffered three significant problems : a high rate of bond failure, separation of metal from reinforced resin components, and fractured tie wings. These three problems received rapid and effective investigation and correction. Damon 3MX bracket is a all metal bracket with least problems

Illustration 8 – Damon 3 and Damon 3MX brackets

(G) SYSTEM R Brackets :

System R brackets (GAC International Inc. 355 kniterboker Ave. Bohemina, NY11716, Illustration - 9) originally called In-ovation brackets, are very similar to the speed brackets in conception and design, but of a twin configuration with tie wings. In 2002, smaller brackets for the lower anterior teeth became available. In-Ovation R (Reduce, referring to the reduced brackets width) and this narrower width was effective in terms of greater inter bracket span. The bracket subsequently became known as system R. Some brackets of this type are difficult to open and this is more common in the lower arch where the gingival end of the spring clip is difficult to visualize. Excess composite at the gingival aspect of brackets in the lower arch can be difficult to see and may also hinder opening. Similarly, lace backs, under ties and elastemerics placed behind the arch-wire are competing for space with the bracket clip. Both Speed and System R and also the similar and recently released Quick brackets (forestadent Bernhard Foerster Gmbh, fig. 8) have addressed this difficulty by providing a labial hole or notch in the clip in which a probe or similar instrument can be inserted to open the brackets

Illustration 9 – System R brackets

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(4) SMARTCLIP Brackets :

The smartclip10 brackets (3M unitek 3M Center, St. Paul, MN55144-1000, Illustration - 10) retains the wire by two C-shaped spring clips on either side of the bracket slots. The instruments or bracket pressure required to insert or remove an archwire is therefore not applied directly to the clip, but to the archwire, which in turn applies the force to deflect the clips and thus permits archwire insertation or removal. This mechanism therefore has to cope with providing easy insertion and removal through the jaws of the clips but must also prevent inadvertent loss of ligation for both small, flexible archwires and large stiff archwires. With wider clinical use, it became apparent that the force required for insertion and removal of thick stainless steel wires from smartclip brackets was uncomfortably high. Recent edition of smartclip brackets called as smartclip 3 has addressed this difficulty by lowering the effective stiffeners of the spring clips. Smartclip is also available in all esthetic ceramic brackets called as CLARITY –SL (with metal slots).

Illustration 10 – Smartclip Bracket

COST AND TREATMENT EFFICIECY

Currently available self-ligating brackets are more expensive then most good quality tie wing brackets. A modest balancing factor is the cost of elastic ligatures that are, ofcourse not required. However, this significant extra cost must be measured against savings in time— an expensive commodity. Self- ligating brackets save appreciable chairside time as many studies suggests, which becomes an added saving.

Many studies have shown a mean reduction of 4 months in active treatment when treated with self-ligating brackets. The more recent bracket type would be expected to show still better treatment efficiency because they are less prone to breakage or loss of the clips and slides, are easier to open and close, are frequently of more effective slot dimensions, and are used with greater understanding of the optimal archwire selection and appointment intervals.

CONCLUSIONS :

Currently available self-ligating brackets offer the very valuable combination of extremely low friction and secure full bracket engagement and at last they are sufficiently robust and user-friendly to deliver most of the potential advantages of this type of bracket. The core advantages of self-ligation are now established and readily available. These developments offer the possibility of a significant reduction in average treatment time and may be also in anchorage requirements, particularly in cases requiring large tooth movements.

A significant clinical advantage of self ligating brackets is subsequently reduced plaque accumulating sites and also very easy to brush (as lack of ligature wire around each bracket) the whole appliance.

While further refinements are desirable and further studies essential, current brackets appear able to deliver measurable benefits with good robustness and ease of use.

References:

1. Stolzenberg J: The Russell attachment and its improved advantages. Int J Orthod Dent Child 21:837-840, 1935

2. Wildman A J :Round table –the Edgelok bracket. J Clin Orthod 6:613-623, 1972

3. Berger J L : The SPEED appliance : a 14 year update on this unique self-ligating orthodontic mechanism. Am J Orthod Dentofacial Orthop 105:217-223, 1994

4. Harradine NWT, Bernie DJ: The clinical use of Activa self-ligating brackets. Am J Orthod Dentofacial Orthop 109:319-328, 1996

5. Damon DH: The rationale , evolution & clinical application of the self-ligating bracket. Clin Orthod Res 1:52-61, 1998

6. Taloumis LJ, Smith TM, Hondrum SO, et al: Force decay & deformation of orthodontic elastomeric ligatures. Am J Orthod Dentofacial Orthop 111:1-11, 19997

7. Shivapuja PK, Berger J : A comparative study of conventional ligation & self-ligation bracket systems. Am J Orthod Dentofacial Orthop 106:472-480, 1994

8. Maijer R, Smith DC: Time saving with self-ligating brackets. J Clin Orthod 24:29-31, 1990

9. Bednar, J. R.; Gruendeman, G. W.; & Sandrik, J.L.: A comparative study of frictional forces between orthodontic brackets & arch wires, Am. J. Orthod. 100:513-522, 1991

10. Smartclip self-ligating appliance system : concept & biomechanics By Hugo Trevisi (Textbook of MOSBY Elsevier Ltd.)

1.self ligating brackets past present future of orthodontics

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