Seminars in Orthodontics: Self Ligating Brackets


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Seminars in Orthodontics: Self Ligating Brackets

  1. 1. Seminars in Orthodontics: Self-Ligating Brackets Dr. Adam Cohen UMDNJ Orthodontics November 17th, 2008
  2. 2. History of Self-ligating brackets <ul><li>Self-ligating brackets do not require an elastic or wire ligature to secure the archwire </li></ul><ul><li>Rather they have an internal mechanism that allows opening and closure with either an instrument or fingertip </li></ul><ul><li>In 1935 Stolzenberg introduce the first self-ligating bracket - Russell Lock edgewise attachment </li></ul><ul><li>Since then there have been a variety of SLB’s available, with a recent surge in popularity over the last 8 years or so </li></ul>
  3. 3. Self Ligating Bracket Types <ul><li>Russell Lock - 1935 </li></ul><ul><li>Ormco Edgelok - 1972 </li></ul><ul><li>Forestadent Mobil-Lock - 1980 </li></ul><ul><li>Forestadent Begg - 1980 </li></ul><ul><li>Strite Industries SPEED - 1980 </li></ul><ul><li>“ A” Company Activa - 1986 </li></ul><ul><li>Adenta Time - 1996 </li></ul><ul><li>“ A” Company Damon SL - 1996 </li></ul><ul><li>Ormco TwinLock - 1998 </li></ul><ul><li>Ormco/ “A” Co. Damon 2 - 2000 </li></ul><ul><li>GAC In-Ovation - 2000 </li></ul><ul><li>Gestenco Oyster - 2001 </li></ul><ul><li>GAC In-Ovation R - 2002 </li></ul><ul><li>Adenta Evolution LT - 2002 </li></ul><ul><li>Ultradent OPAL - 2004 </li></ul><ul><li>Ormco Damon 3 2004 </li></ul><ul><li>3M Unitek Smart Clip - 2004 </li></ul><ul><li>Ormco Damon 3 MX - 2005 </li></ul><ul><li>Ultradent OPAL metal - 2006 </li></ul><ul><li>Forestadent Quick - 2004 </li></ul><ul><li>Lancer Praxis Glide - 2004 </li></ul><ul><li>Class I/Ortho Organisers Carriere LX - 2004 </li></ul>
  4. 4. Properties of an ideal ligation system <ul><li>Be secure and robust </li></ul><ul><li>Ensure full bracket engagement </li></ul><ul><li>Exhibit low friction between bracket and archwire </li></ul><ul><li>Be quick and easy to use </li></ul><ul><li>Permit easy attachment of elastic chains </li></ul><ul><li>Assist good oral hygiene </li></ul><ul><li>Be comfortable for the patient </li></ul>
  5. 5. Secure Ligation <ul><li>Should be no loss of ligation between appointments </li></ul><ul><li>Wire ligatures are reliable while elastomeric ligatures are less </li></ul>
  6. 6. Full Bracket Engagement <ul><li>Want archwire to be fully engaged in bracket </li></ul><ul><li>Wire ligatures allow this and can be maintained over the lifetime of an appointment </li></ul><ul><li>Elastomerics can exert insufficient force to fully engage and also degrade as the elastomer stretches over time </li></ul>
  7. 7. Low Friction <ul><li>Frictional forces arising from ligation add additional resistance that must be overcome by higher forces </li></ul><ul><li>This results in a net effective force that is difficult to assess and a binding force that is higher between bracket and wire </li></ul><ul><li>Wire ligatures produce lower friction then elastomeric ligatures </li></ul><ul><li>However, wire ligatures can also result in high and variable levels of friction relative to the force levels optimal for tooth movement </li></ul>
  8. 8. Static versus Dynamic Friction <ul><li>Static friction - the force between two objects having no motion; being at rest </li></ul><ul><li>Dynamic (sliding or rolling) friction - to move over a surface while maintaining continuous contact </li></ul><ul><li>Friction is affected by bracket material, bracket design, archwire material and shape, ligation method, bracket-archwire angulation and dynamic forces </li></ul><ul><li>Although several of these variables are out of our control, the use of SLBs can greatly reduce friction between the archwire and bracket </li></ul>
  9. 9. Quick and Easy to use <ul><li>Significant disadvantage of wire ligation </li></ul>
  10. 10. Easy Attachment of Elastic Chain <ul><li>Tie wings on conventional brackets make attachment of elastic chain very convenient </li></ul><ul><li>Some SLBs have no tie wings </li></ul>
  11. 11. Maintenance of Optimal Oral Hygiene <ul><li>Most people feel that elastomerics result in more plaque accumulation then wire ligatures </li></ul><ul><li>There are some studies that support this </li></ul><ul><ul><li>Forsberg et al. Ligature wires and elastomeric rings: two methods of ligation, and their association with microbial colonization of Streptococcus mutans and lactobacilli. 1991. Eur J Orthod. 13:416-420. </li></ul></ul><ul><li>There are other studies that found no difference </li></ul><ul><ul><li>Sukotapatipark et al. A scanning electron microscopy study. 2001. Eur J Orthod. 23:475-484. 2001. </li></ul></ul>
  12. 12. Patient Comfort <ul><li>Elastomerics are easy for the patient to handle </li></ul><ul><li>Wire ligatures require careful tucking of the ends to avoid emergency visits </li></ul>
  13. 13. Limitations of Conventional Ligation <ul><li>Inability to provide and maintain full archwire engagement </li></ul><ul><li>Increased friction </li></ul><ul><li>Elastomeric force decay resulting in non-optimal tooth control </li></ul><ul><li>Ligatures can become displaced </li></ul><ul><li>Wire ligation is time consuming </li></ul>
  14. 14. Core Advantages of SLBs <ul><li>Full archwire engagement </li></ul><ul><li>Low friction between bracket and archwire </li></ul><ul><li>Less chairtime assistance needed </li></ul><ul><li>Faster archwire removal and ligation </li></ul>
  15. 15. Low Friction and Secure Full AW Engagement <ul><li>Study by Srinivas (postgraduate thesis in India) </li></ul><ul><li>Split Mouth study of canine retraction - Damon SL on once side and conventional bracket on the other side </li></ul><ul><ul><li>Damon side resulted in </li></ul></ul><ul><ul><ul><li>More rapid retraction (.24mm per month) </li></ul></ul></ul><ul><ul><ul><li>Shorter duration for 3mm retraction (12 wks v. 16wks) </li></ul></ul></ul><ul><ul><ul><li>Less rotation (8 degrees v. 12 degrees) </li></ul></ul></ul><ul><ul><ul><li>Less anchorage loss (.3mm) </li></ul></ul></ul>
  16. 16. Alignment of Severely mal-aligned teeth <ul><li>Combination of low friction and secure archwire engagement is useful for aligning very irregular teeth </li></ul><ul><li>With low friction the wire is able to slide through the brackets of the rotated teeth resulting in rapid uncrowding </li></ul><ul><li>Full engagement results in full control while sliding teeth along the archwire </li></ul>
  17. 17. Lack of Adoption of SLBs <ul><li>Widespread use of these brackets has been hindered, until recently, due to several problems with bracket design - some examples include </li></ul><ul><ul><li>SPEED: early brackets had clips that were easily displaced or broken </li></ul></ul><ul><ul><li>Mobil-Lock: narrowness of the resulting labial face of the slot resulting in poor rotational control </li></ul></ul><ul><ul><li>Activa Brackets: absence of wings, abnormal base shape </li></ul></ul><ul><ul><li>Damon SL: inadvertent opening of the slide, prone to breakage </li></ul></ul>
  18. 18. SPEED <ul><li>The Speed appliance was developed in the 1970s by Dr. Herbert Hanson (from Canada) </li></ul><ul><li>Has been commercially available since 1980. </li></ul><ul><li>It is a miniaturized self-ligating bracket with an active super elastic NiTi spring clip to entrap the archwire </li></ul><ul><li>Archwire engagement can result in elastic deflection of the spring clip </li></ul><ul><li>The deflection of the spring clip represents energy stored in the spring clip, and as the bracket and its accompanied tooth are reoriented relative to the archwire, energy is released </li></ul>
  19. 19. Advantages of Design <ul><li>Highly flexible NiTi clip </li></ul><ul><li>Minimal Friction during sliding mechanics </li></ul><ul><li>Extended range of activation due to energy stored in clip </li></ul><ul><li>Large interbracket span </li></ul><ul><li>Spring clip will not deform or fatigue </li></ul><ul><li>Horizontal auxiliary slot </li></ul>
  20. 20. Treatment Philosophy - As outlined by Dr. Hanson <ul><li>Try to treat without extractions in any case that has the necessary potential </li></ul><ul><li>If extractions necessary, extract 2nd bicuspids to minimize any reduction in prominence of dentition </li></ul><ul><li>Preliminary functional appliances as necessary to favorably alter jaw growth if possible </li></ul><ul><li>Use intraoral distalization instead of headgear </li></ul><ul><li>Expand arches that have failed to develop to their full potential </li></ul><ul><li>In patients that exhibit lots of gingival tissue, intrude upper anterior teeth </li></ul><ul><li>Correct tooth rotations to ideal alignment without overcorrection - rely on IPR and circumferential supra-crestal fiberotomies to enhance retention </li></ul><ul><li>Overcorrect Class II/III where strong tendency for relapse occurs </li></ul>
  21. 21. SPEED pictures The SPEED finishing archwire has a quarter round shape, which facilitates archwire insertion, spring closure, and is highly effective in torque control. Supercable consists of seven strands of superelastic nickel titanium wire in a coaxial form. It is impossible to permanently deform Supercable regardless of the malalignment of the dentition. (B) The combined effect of the initial light multistrand Supercable archwire, the wide interbracket span between the narrow SPEED brackets, and the energy storing capability of the spring clip greatly increases the range of appliance activation.
  22. 22. DAMON <ul><li>Damon Philosophy - use just enough force to initiate tooth movement </li></ul><ul><li>Want this force to be low enough to prevent occluding blood vessels in the PDL and allow cells the ability to transport messengers necessary to produce bone resorption and apposition </li></ul><ul><li>Is a passive-self ligation system - it is suggested that this type of system results in </li></ul><ul><ul><li>Less anchorage requirements </li></ul></ul><ul><ul><li>Less intraoral expansion - because the force of the AW is not transformed or absorbed by the ligatures </li></ul></ul><ul><ul><li>Less need for extractions </li></ul></ul><ul><ul><li>Low levels of static and dynamic friction </li></ul></ul><ul><ul><li>Rigid ligation </li></ul></ul><ul><ul><li>Control of tooth position </li></ul></ul>The Damon Evolution -> -> -> ?
  23. 23. Effects of Passive Ligation on Friction <ul><li>Many authors (Thomas et al. 1998 Eur J Orthod, Pizzoni et al. 1998 Eur J Orthod, Khambay et al. 2004 Eur J Orthod) have found that static friction measured in vitro is much less with a passive self ligating appliance that any other type of fixed appliance </li></ul><ul><li>When angulation or inclination is applied to the bracket friction is generated, however it is less for SLB’s than for conventional ligation </li></ul>Figure showing static friction for passive, active, TipEdge, and conventionally ligated brackets. The value for the passive self-ligating Damon SL bracket was zero except for with the 0.019″ × 0.025″ stainless steel archwire. The wires were drawn through the brackets and the frictional resistance was measured using an Instron 1193 testing machine.
  24. 24. High versus Low Torque Brackets <ul><li>High Torque Upper Incisors </li></ul><ul><ul><li>Extraction cases </li></ul></ul><ul><ul><li>Class II Div I where mechanics might excessively retrocline teeth </li></ul></ul><ul><ul><li>Class II Div II </li></ul></ul><ul><li>High Torque Upper canines </li></ul><ul><ul><li>First PM extraction cases </li></ul></ul><ul><ul><li>When crowns of upper cuspids are palatally tipped </li></ul></ul><ul><li>Low Torque Upper incisors </li></ul><ul><ul><li>Excessively Proclined upper incisors </li></ul></ul><ul><ul><li>Isolated upper incisors with palatally displaced roots </li></ul></ul><ul><ul><li>Malocclusions where Tx mechanics may result in excessive upper incisor proclination </li></ul></ul><ul><ul><li>Moderate and severe upper arch crowding </li></ul></ul><ul><ul><li>Anterior open bite cases </li></ul></ul><ul><li>Low Torque Lower Incisors </li></ul><ul><ul><li>Cases where control is needed to avoid proclination of lower incisors (extreme lower labial segment crowding, Class II elastics, fixed class II correctors </li></ul></ul>
  25. 25. Stages of Treatment <ul><li>Phase 1 - Light Round High Technology Wires (.013, .014 or .016 CuNiTi) </li></ul><ul><ul><li>Level the arches, excluding 2nd molars </li></ul></ul><ul><ul><li>Correct all anterior rotations and partial correction of posterior rotations </li></ul></ul><ul><ul><li>Initiate arch development with use of light forces to allow soft tissue to influence arch shape </li></ul></ul><ul><li>Phase 2 - High Technology Rectangular Wires (14x25 CuNiTi --> 18x25 CuNiTi or 16x25 CuNiti) </li></ul><ul><ul><li>Fully correct all rotations </li></ul></ul><ul><ul><li>Consolidate any anterior space </li></ul></ul><ul><ul><li>Initiate torque control </li></ul></ul><ul><ul><li>Initiate bite opening </li></ul></ul><ul><ul><li>Continue arch development </li></ul></ul><ul><ul><li>Use of .025 in first order dimension is critical to obtain tooth alignment by almost completely filing the .027 slot depth </li></ul></ul><ul><li>Phase 3 - Major Mechanics (19x25 pre-posted stainless steel archwires) </li></ul><ul><ul><li>Maintain archform </li></ul></ul><ul><ul><li>Finish torque control </li></ul></ul><ul><ul><li>Consolidate posterior space </li></ul></ul><ul><ul><li>Completely correct AP, buccolingual and vertical relationships </li></ul></ul><ul><li>Phase 4 - Finishing and Detailing </li></ul><ul><ul><li>Can continue use of SS AW’s or can use 19x25 TMA for individual adjustments </li></ul></ul>
  26. 26. Damon Case Presentation 14 years old
  27. 27. 12 Months into Tx 1 yr post-retention (26 month Tx)
  28. 28. <ul><li>Lower Cast Measurements </li></ul><ul><ul><li>Intercanine: 19.2  29.4 </li></ul></ul><ul><ul><li>Inter 1 st Premolar 29.6  38.1 </li></ul></ul><ul><ul><li>Inter 2 nd Premolar: 38.2  43.8 </li></ul></ul><ul><ul><li>Inter 1 st Molar: 49.9  50.7 </li></ul></ul><ul><li>IMPA – 87.4  97.8 </li></ul><ul><li>L1-Apo: 0.2  3.4 </li></ul>
  29. 29. In-Ovation
  30. 30. In-Ovation <ul><li>Innovation R – the standard In-ovation bracket we use in clinic </li></ul><ul><li>Innovation C - esthetic innovation brackets </li></ul><ul><li>Innovation L MTM - indirect bonding of anterior teeth (3-3) with these lingual braces, no wire changes </li></ul><ul><li>Innovation L - lingual innovation braces </li></ul><ul><li>Innovation brackets open from the gingival margin - </li></ul>
  31. 31. In-Ovation R <ul><li>Bracket design has a closing clip that can apply pressure or no pressure to the archwire as the situation requires </li></ul><ul><li>This bracket was designed to be a passive or active SLB </li></ul><ul><li>The clip secures the AW into place but also allows the clip to flex buccally if the wire is not fully seated </li></ul><ul><li>At max flex the clip can apply 250 g of force </li></ul>
  32. 32. In-Ovation R <ul><li>Our In-Ovation bracket has an .022 slot </li></ul><ul><li>To completely fill the slot without impinging on the clip you would want to place an .022 x .018 wire </li></ul><ul><li>Fully seating this .022 x .018 results in full in-out, tip and torque control without clip friction </li></ul>
  33. 33. Smart Clip <ul><li>NiTi clip mechanism that retains the wire by two C-shaped spring slips on either side of the bracket slot </li></ul><ul><li>The wire contains no moving door or latch and thus are the only true self-ligating brackets </li></ul><ul><li>MBT prescription </li></ul><ul><li>The force required for the removal and insertion of heavy stainless steel wires is often uncomfortable for patients </li></ul>
  34. 34. Active Clip or Passive Slide? <ul><li>Active Clips - SPEED, In-Ovation, Quick Brackets, Time2 (American ortho) </li></ul><ul><li>Passive - Damon, Smart clip, Praxis Glide, and Carriere LX </li></ul><ul><li>Intended benefit of storing some force in the clip - “a given wire will have its range of labiolingual action extended and produce more alignment than would a passive slide with the same dimension wire” </li></ul><ul><li>However, with increased clearance between a given wire and a passive slide, lower forces will be generated along with less binding to possibly allow teeth to push each other as they slide along the wire </li></ul><ul><li>Not many studies have been done to assess the effectiveness of active versus self ligation at this point </li></ul>
  35. 35. Current Literature…
  36. 36. Evaluation of frictional forces during dental alignment: an experimental model with 3 nonleveled brackets <ul><li>Aim of study was to evaluate frictional forces generated by various combinations of brackets and orthodontic wires </li></ul><ul><li>Used passive self-ligating brackets (Damon SL2) and conventional twin SS brackets </li></ul><ul><li>Tests 3 NiTi wires (.014, .016, .016x.022), 2 SS multistranded wires, and 1 TMA </li></ul><ul><li>Used elastic ligatures and SST’s for the twin brackets </li></ul><ul><li>Each 10-bracket AW combo was tested 10 times </li></ul><ul><li>The ability of the wire to slide through the bracket was influenced by wire-cross section dimension, wire material, number of wire strands, and type of ligation </li></ul><ul><li>Overall conclusions were that frictional forces can be greatly reduced through the use of SLBs, smaller diameter wires and less stiff wires </li></ul>
  37. 37. Torque Expression of Self Ligating Brackets <ul><li>Purpose of the study was to measure the difference in 3rd order moments that can be delivered by engaging a 19x25 SS AW to various brackets </li></ul><ul><li>2 Active SLBs were used - In-Ovation and SPEED </li></ul><ul><li>2 Passive SLBs were used - Damon2 and Smart Clip </li></ul><ul><li>A bracket/wire assembly torsion device was used - is able to apply torsion to a wire while maintaining perfect vertical and horizontal alignment between the wire and the bracket </li></ul><ul><li>The torque was then measured by a multi-axis force/torque transducer </li></ul><ul><li>Results showed that torque started to be expressed at lower degrees of torsion (7.5) for the active SLBs versus the passive SLBs (15) </li></ul><ul><li>Concluded that active SLBs are more effective in torque expression </li></ul>
  38. 38. External apical root resorption in patients with conventional and self-ligating brackets <ul><li>Aim was to investigate the amount of external apical root resorption between conventional and passive SLBs (Damon2) </li></ul><ul><li>96 patients selected </li></ul><ul><li>Pts received Tx with either SLBs or conventional brackets with .022 slot </li></ul><ul><li>No difference was found in the amount of EARR, but a positive association existed between EARR and duration of TX </li></ul>
  39. 39. Alignment efficiency of Damon3 self-ligating and conventional orthodontic bracket system: A randomized clinical trial <ul><li>Aim of this study was to compare the efficiency of mandibular tooth alignment and the clinical effectiveness of a self-ligating (Damon 3) and a conventional preadjusted orthodontic bracket (Ormco bracket). </li></ul><ul><li>62 pts from 2 orthodontic clinics (32 male, 30 female) with mandibular incisor irregularities (Little’s Irregularity Index) of 5 to 12mm and prescribed extraction pattern including the mandibular first premolars </li></ul><ul><li>Wire sequence: .014 NiTi  14x25 Niti  18x25 NiTi  19x25SS </li></ul><ul><li>No difference in the initial or the overall rate of mandibular incisor alignment between the two bracket types </li></ul><ul><li>Only significant influence of initial rate of alignment was the amount of initial irregularity </li></ul>
  40. 40. References <ul><li>Sadowsky, PL. Self-Ligating Orthodontic Brackets. 2008. Seminars in Orthodontics. 14(1). </li></ul><ul><li>Scott P, DiBiase A, Sherriff M, Cobourne M. Alignment efficiency of Damon3 self-ligating and conventional orthodontic bracket systems: A randomized clinical trial. 2008. Am J Orthod Dentofacial Orthop. 134:470.e1-470.e8. </li></ul><ul><li>Pandis N, Nasika M, Polychronopoulou A, Eliades T. External apical root resorption in patients treated with conventional and self-ligating brackets. 2008. Am J Ortho Dentofacial Orthop. 134:646-51. </li></ul><ul><li>Matarese G, Nucera R, Militi A, Mazza M, Portelli M, Festa F, Cordasco G. Evaluation of frictional forces during dental alignment: An experimental model with 3 nonleveled brackets. 2008. Am J Ortho Dentofacial Orthop. 133:708-15. </li></ul><ul><li>Badawi H, Toogood R, Carey J, Heo G, Major P. Torque expression of self-ligating brackets. 2008. Am J Orthod Dentofacial Orthop. 133-721-8 </li></ul><ul><li>Rinchuse D, Miles P. Self-ligating Brackets: Present and Future. 2007. Am J Orthod Dentofacial Orthop. 132:216-22 </li></ul><ul><li>Thomas S, Birnie DJ, Sherriff M. A comparative in vitro study of the fricitonal characterisitics of two types of self-ligating brackets and two types of preadjusted brackets tied with elastomeric ligatures. 1998. Eur J Orthod 20:589-596. </li></ul><ul><li>Srinivas S. Comparison of canine retraction with self-ligated and conventional ligated brackets—a clinical study. 2003. Thesis in fulfillment of postgraduate degree, Tamilnadu Medical University, Chennai, India </li></ul>