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Debonding techniques and enamel fracture patterns /certified fixed orthodontic courses by Indian dental academy

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Debonding techniques and enamel fracture patterns /certified fixed orthodontic courses by Indian dental academy

  1. 1. DEBONDING TECHNIQUES INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2.  Introduction  Mechanical debonding of Steel Brackets  Problems associated with debonding ceramic brackets  Mechanical debonding of ceramic brackets  Electrothermal debonding of brackets  Laser Debonding of Ceramic Brackets  Chemical solvents for debonding ceramic brackets  Finishing procedures during debonding.  Effects of Debonding on Enamel  Management of teeth with white spot lesions after debonding  References.
  3. 3. Introduction  The objectives of debonding are to remove the attachment and all the adhesive resin from the tooth and restore the surface as closely as possible to its pretreatment condition without inducing iatrogenic damage.  To obtain these a correct technique is of fundamental importance, else it may be unnecessarily time consuming and damaging to enamel.
  4. 4. I .Mechanical Bracket removal : A. Steel brackets  Several techniques have been described for debonding brackets, and various designs of orthodontic pliers have been designed for the purpose.  Ligature cutters: Some authors recommend using ligature cutters to debond brackets: these work perfectly well but can damage the beaks, which can detract from the original purpose. Others have expressed concern that enamel damage may be caused by the beaks of ligature cutters used in this way (Oliver, 1988).
  5. 5.    Weingart pliers: A method for removing brackets is to squeeze together the wings using Weingart pliers. This transmits a shear force to the composite adhesive and breaks the bond. Disadvantage : bracket wings often become distorted, altering the slot dimension, making the bracket useless for recycling
  6. 6. .  Use of Debonding pliers: Recommended technique in which the chisel shaped beaks are placed as close to the base of the bracket as possible and a peeling type force is applied.  Because metal brackets are ductile, this force is transmitted to the adhesive bond, breaking it.
  7. 7.  Lift-off Debonding Instrument: This a design of pliers in which a tensile force is placed on the adhesive bond through a wire loop hooked over the bracket tie wings, pulling the wings of the bracket directly away from the tooth surface.  This method distorts the brackets the least and is preferred if recycling is a consideration.
  8. 8.  Oliver     and Pal (AJODO July 1989) compared three methods of debonding: Method A— The mesial and distal wings of an edgewise twin bracket are squeezed together with pliers. Solid brackets are removed by placing the pliers occlusally and gingivally. Method B— A shear force is applied with the blades of the debonding pliers or ligature cutters positioned at the enamel/composite or composite/bracket interface. Method C— Use of LODI. This may be used in two ways: either the arch wire may be left in situ or the slot keeper (a length of 0.018 ´ 0.022-inch wire embedded in a plastic handle) may be placed in the bracket after arch wire removal. In either case, the presence of a wire in the bracket should help to maintain the slot dimensions. The brackets tested were Rocky Mountain Bioprogressive and Unitek Light Square.
  9. 9.  Results : Method B produced the most distortion, the majority of which occurred on the base. All parts of the bracket were almost equally affected with method A, whereas method C produced wing distortion only.  In general RM brackets distorted more often than Unitek Light Square brackets and premolar brackets distorted more often than incisor or canine brackets.  Most of the debonded brackets had increased slot dimensions compared with control brackets, the greatest being an increase of 0.032 mm.
  10. 10.  The clinical significance of an increase in slot dimension of this order (6.5%) will be loss of effective torque from an arch wire.  The authors concluded that if recycling of brackets is considered, then use of Unitek light square brackets and the lift off debracketing instrument for bracket removal is most advantageous.
  11. 11.  Coley-Smith and Rock (BJO 1999) compared two methods of debonding (bracket removing pliers or a lift off debonding instrument) in 507 metallic brackets, with and without the archwire in place during debonding.
  12. 12.  After debond brackets were tested for slot closure by the fit of rectangular test wires from 0·016X 0·022 to 0·021X 0·025 inch in size.  The LODI produced few slot closures sufficient to affect the fit of all but the largest test wire.  Bracket removing pliers used after removal of the archwire produced significantly greater numbers of slot closures and distorted brackets.
  13. 13.  Ten per cent of the brackets debonded using bracket removing pliers had distorted bases, no base damage was produced by the LODI.  When bracket removing pliers are used, the archwire should be left in place at the time of debond since this reduces the number of distortions.
  14. 14. Why are ceramic brackets difficult to debond?  The inert composition of the aluminum oxide ceramic brackets makes chemical cohesion between the ceramic base and the adhesive resin impossible.  Therefore, a silane coupling agent is used as a chemical mediator between the adhesive resin and the bracket base.  The silane molecule is a bifunctional molecule; one end is a reactive silanol group that can bind tenaciously to glass, while the other end of the molecule reacts with other acrylic resins and polymerizes, producing a cohesive bond with the resin material.
  15. 15.  The base of each bracket is coated with silica glass to promote bonding with the silanol functional group of the silane molecule.  The adhesion between the resin and the ceramic bracket bases has increased to a point where the most common site of bond failure during debonding has shifted from the bracket baseadhesive interface to the enamel adhesive interface, a less desirable site.  This has led to an increase in the incidence of bond failures within the enamel surface.
  16. 16.  Also, though the tensile strength of the new ceramics is greater than that of stainless steel, they have lower fracture toughness, compared with conventional stainless steel brackets.  During loading, stainless steel will elongate approximately 20% of its original length before failing, while sapphire will elongate less than 1% before failing.  Thus, ceramics are more likely to fracture than metals under the same conditions during debonding.  Clinically, this is seen most often at the tie wing area.
  17. 17.  A.Example of fracture of the Starfire bracket. B, Example of fracture of the Allure bracket. C, Example of fracture of the Transcend bracket.
  18. 18.  Condition of the surface of the ceramic: A shallow scratch on the surface or a microscopic crack will drastically reduce the load required for fracture of ceramic brackets.  Stresses introduced during ligation and arch wire activation, forces of mastication and occlusion, and forces applied during bracket removal with pliers or debracketing instruments are all capable of creating cracks in ceramic brackets that may lead to failure.
  19. 19. B.Mechanical debonding of ceramic brackets.  In order to address the problem of enamel fracture during debonding, various manufacturers have given their own recommendations on debonding.  GAC recommends the use of the ETM 346 plier for removal of the Allure brackets . ETM 346 plier
  20. 20.  The Allure brackets are beveled on the incisal and gingival edges for easy insertion of the plier which is slowly squeezed to remove the bracket.  A-Company has produced a similar plier with an additional shield to catch any splinters which may fly off during debonding.  Unitek do not recommend the use of conventional debonding tools with their Transcend Series 2000 brackets.  These brackets are mechanically retained, and though strong in shear, are significantly weaker in the tensile mode.
  21. 21.  Accordingly Unitek have introduced a new debonding tool, which applies a tensile force.  This has been shown to produce less enamel damage.  Generally, cutting brackets off with gradual pressure from tips of twin beaked pliers close to the bracket adhesive surface is not recommended as it could introduce horizontal enamel cracks.  The use of mechanical debonding of ceramic brackets carries the risk of bracket fracture and the additional risk of injury to doctor or patient from flying fragments.  The remaining bracket may also have to be removed with a diamond bur, which is time consuming and injurious to pulp, if coolant is not used.
  22. 22.  Recently, 2 new ceramic bracket designs were introduced to the market in an attempt to minimize the problems that are encountered by the clinician.  The Clarity bracket (3M Unitek) has a metal lined arch wire slot which minimizes friction, and is also suggested to help strengthen the bracket to withstand routine orthodontic torque forces.  It also incorporates a vertical slot, which is designed to help create a consistent bracket failure mode during debonding.
  23. 23. Facial (A), and lingual (B), views of the Clarity ceramic bracket.
  24. 24.  The MXi (TP Orthodontics, Inc), on the other hand,is an injection-molded polycrystalline bracket that incorporates a polymeric base made of a high strength epoxy resin that adheres to most orthodontic adhesives.  The polymeric base has a mesh architecture to enhance bond strength. The base is sufficiently flexible to allow plastic deformation at levels similar to that of metal brackets.  The ceramic/polymer interface is reinforced with an amorphous glass layer, which is formed integrally on the smooth ceramic surface through a high-temperature sintering process.
  25. 25. Facial (A) and lingual (B) views of the MXi ceramic bracket.
  26. 26.  Bishara et al (AJODO 1999) compared the debonding characteristics of the two brackets, using their appropriate pliers. The most efficient method of debonding the Clarity bracket is to use the Weingart pliers and apply pressure to the tiewings. Weingart pliers for debonding Clarity brackets
  27. 27. ETM plier used to debond The most efficient method to debond the MXi ceramic bracket is to place the blades of the ETM 346 plier between the bracket base and the enamel surface. MXi ceramic brackets.
  28. 28.  Their findings indicated that the mean shear bond strength of the Clarity bracket (10.4 MPa)was greater than that of the MXi ceramic bracket (7.6 MPa).  These are more than the minimal force levels suggested by Reynolds (5.9 to 7.8 MPa) as being clinically acceptable for orthodontics.  The Clarity brackets had a greater incidence rate of partial bracket failure with the Weingart pliers, as compared the to the MXi brackets in which no failures were seen.
  29. 29.  ARI scores indicated that, when debonding these brackets with the appropriate pliers, there was a greater tendency for most of the adhesive to remain on the enamel.  This has the advantage of protecting the enamel surface and the disadvantage of having more residual adhesive material present that needs to be mechanically removed by the clinician.
  30. 30.  The Inspire monocrystalline bracket manufactured by Ormco has also undergone modification by reducing the area of retentive beads on the bracket base by 20% on the gingival side.  Diaz and Swartz (JCO 2004) did lab and clinical studies on the modified bracket and reported a significant reduction in the force required to remove the bracket in one piece with the debonding plier.
  31. 31. II.Electrothermal debonding of brackets  (Sheridan et al., AJO 1986) developed an alternative to conventional metal bracket removal, known as electrothermal debonding.  It is the technique of removing bonded brackets from enamel surfaces with a cordless battery device that generates heat.  This heat (in the range of 232ºC) is transferred to the bracket by a blade that is placed in the bracket slot.  The heat deforms the bracket/adhesive interface and the bracket may then be removed without distortion or excessive forces being applied to the underlying enamel
  32. 32. Diagrammatic view of ETD blade engaging bracket slot. A, Lock-on arm engaging incisal wings of bracket; B, Lip shield; C, Heat element; D, blade positioned in bracket slot.
  33. 33. , Battery-powered heat source. Index finger is on "heat on demand" button. Thumb is on "lock-on" extension
  34. 34.  Sheridan et al (1986) reported that the mean increase in pulpal temperature, when debonding metal brackets with this method was 2.4 ºC; when cooling water spray was used immediately after debracketing, the mean increase was only 0.12ºC.  These values are well within the biological limits specified by Zach and Cohen (1965).  Kearns et al (BJO 1997) compared the mechanical and electrothermal debonding techniques for 3 varieties of ceramic brackets: Starfire (monocrystalline, chemically bonded), Transcend 6000 (polycrystalline, micromechanically bonded) and Fascination (polycrystalline, chemically bonded).
  35. 35. reported that the shear forces recorded in the mechanically debonded cohort did not differ significantly between different bracket types.(Mean 12.4 Mpa)  There was a significant difference between the shear forces recorded when the different brackets were debonded electrothermally, with the Fascination® group showing significantly lower shear force levels (1.8 Mpa) than the other brackets.  The shear force levels recorded for the electrothermally debonded brackets (Mean 4.6 Mpa) were significantly lower than those recorded for mechanically debonded groups  They
  36. 36.  This study showed a mean increase in temperature higher than those found by other workers using similar recording methods  These values were similar to the 5·5°C limit commonly accepted as being the level above which some pulpal damage occurs.  Jost-Brinkmann et al (EJO 1997) did an in vivo study in which 12 human premolars scheduled for extraction were bonded with ceramic brackets which were subsequently debonded using ETD. After 4 weeks, the teeth were extracted and histologically examined. No signs of pulpal inflammation were seen.
  37. 37.  Takla and Shivapuja(AJODO 1995) performed an in vivo study in which a total of 30 teeth scheduled for orthodontic extractions were used.  15 teeth were extracted 24 hours after ETD, 7 were extracted 28 to 32 days after ETD, and 8 were the control teeth and debonded by a conventional method, with pliers.  The pulp was normal in most cases in the control group.  There was significant hyperemia seen 24 hours after debonding in teeth debonded by ETD.  Teeth extracted 30 days after ETD showed varied responses, ranging from complete recovery in some cases to persistence of inflammation and pulpal fibrosis.
  38. 38. 30 days postdebond case. Presence of inflammatory cells (Iymphocytes), and vascular engorgement. Photomicrograph 24 hours after debonding. Vascular engorgement and extravasation of RBCs. 30 days post debond. Normal pulp tissue with minimal evidence of inflammation.
  39. 39.  Teeth subjected to the conventional debonding were normal histologically.  The authors proposed that patients with compromised teeth that have large restorations or a questionable pulpal status could behave more adversely to this significant amount of heat applied.  In compromised cases and on older patients, performing pulp vitality tests before ETD may inform the operator about the status of the pulp and thereby prevent the potential for pulpal damage.
  40. 40.  Knight et al, AJO-DO 1997 studied the safety of electrothermal debonding of ceramic brackets from teeth with ceramic veneers, as compared with metal brackets.  Results of this study suggest that metal brackets cannot be predictably debonded without producing either veneer damage, if debonded mechanically or electrothermally, or potential pulp damage, if debonded electrothermally.  Ceramic brackets may be removed without causing either veneer or pulpal damage, if debonded electrothermally.  The current recommendation for bonding to a ceramic veneer is to place a ceramic bracket that may be subsequently electrothermally debonded.
  41. 41.  Luthra S et al (1998) investigated the pulpal damage associated with electrothermal debonding.  A total of 50 teeth from 14 patients, nine of whom were females and five were males, Dentaurum Electrothermal debonding who had to undergo unit used in the study. extractions for orthodontic purposes were used to provide the histologic material.  All 50 teeth were bonded with Fascination ceramic brackets.
  42. 42.  30 teeth were debonded using the Dentaurum Electrothermal debonding unit.  Ten teeth were extracted 24 hours after ETD, ten were extracted 28-32 hours after ETD, and ten were extracted 56 days after ETD.  20 teeth served as controls and were debonded by conventional methods. Debonding procedure with the electrothermal debonding unit.
  43. 43.    The 24 hour group and the 28-32 day group debonded by ETD, on histologic examination, showed dilatation of the pulpal vessels and engorgement with RBC’s. The 56-day sample in general showed a normal pulpal architecture. It was concluded that the pulp is predominantly unaffected by electrothermal debonding of brackets, with most changes being of a reversible nature.
  44. 44. III. Ultrasonic debonding of ceramic brackets    Krell, Courey, and Bishara AJODO 1993 described the use of 2 Ultrasonic tips for debonding of brackets. Bracket removal was initiated at the incisal portion of the bracket, with the KJS tip, the straight chisel bevel directed toward the bracket itself. After placing the tip at either the gingival or incisal edge, the ultrasonic unit was activated while moving the tip in a mesial to distal direction.
  45. 45.   This rapidly created a groove in the composite. On gaining approximately a 0.5 to 1 mm "purchase point," a rocking motion was then incorporated until bond failure occurred. Alternating the use of the KJS with the KJC tip facilitated bracket removal.
  46. 46.  Bishara and TruloveAJO-DO 1990 Sep (263 273) reported that although the incidence of bond failure at the enamel-adhesive interface is high when the ultrasonic technique is used, the likelihood of enamel damage with this technique is relatively minimal.  This is because the force levels required to achieve bond failure are significantly reduced with the ultrasonic tips compared with the force needed for the conventional removal methods.  A disadvantage of ultrasonic method is the increased amount of time required for debonding.
  47. 47. Laser Debonding of Ceramic Brackets  The discovery of optic laser technology began with the invention of ruby lasers in the early 1960s.  During the 1980s and early 1990s, introduction of lasers into dentistry was approved by the USFDA.  Since the early 1990s, lasers have been used experimentally for debonding ceramic brackets.
  48. 48. Mechanism of Laser debonding: According to Tocchio et al (AJODO 1993), laser energy can degrade the adhesive resin by 3 methods  Thermal softening  Thermal ablation  Photoablation.
  49. 49.  Thermal softening occurs when the laser heats the bonding agent until it softens.  Clinically this results in the bracket succumbing to gravity and sliding off the tooth surface.  It is a relatively slow process, which means it can lead to a large rise in both tooth and bracket temperature.  Thermal ablation occurs when heating is fast enough to raise the temperature of the resin to its vaporization range before debonding by thermal softening occurs.  This results in the bracket being blown off the tooth surface.  Photoablation also results in the bracket being blown off the surface of the tooth.
  50. 50.  It occurs when very high energy laser light interacts with the adhesive material and the energy level of the bonds between the adhesive resin atoms rapidly rises above their dissociation energy levels, resulting in decomposition of the material.  Tocchio et al suggested that in monocrystalline brackets debonding takes place by ablation,while for polycrystalline brackets it is due to thermal softening.  Strobl et al ( AJODO 1992) showed that with the aid of lasers, debonding force is significantly reduced, when using a Bis GMA adhesive resin.  There was a difference in debonding characteristics for mono and poly crystalline brackets.
  51. 51.   Using CO2 lasers, at a total energy of 15 Joules, there was a 5.2 fold reduction in debonding force for monocrystalline brackets but only a 1.3 fold reduction for polycrystalline brackets. A fixed laser energy power level of 14.1 watts applied for 2 seconds was selected as most optimal.
  52. 52. Why do poly and monocrystalline brackets debond differently?  The different behaviors observed are, in part, due to differences in the design (shape and dimensions) of the two brackets, as well as in their different microscopic structure.  The polycrystalline material consists of an agglomerate of small microcrystals with random orientation, size distribution, and shape that result in a much higher energy diffusion (heat and light) than the basically homogeneous monocrystalline brackets.  Heat transmits through the body of the monocrystalline bracket with much less lateral spreading, which results in a significantly hotter spot at the bracket-adhesive interface.
  53. 53.  Since the adhesive must be heated to approximately 150° to 200° C before significant softening of the composite occurs, a more localized hot spot is more effectively obtained with the monocrystalline brackets.  This is supported by the observation that at higher laser energy levels, the monocrystalline brackets have a tendency, during the debonding process, to show plasma or plume formation, occasionally associated with the cracking of the bracket along the wire slot.  The polycrystalline brackets showed no such behavior at the same energy levels.
  54. 54.  In comparison to the lased group, the non lased group showed a slightly higher incidence of bracket failure.  Strobl et al compared the use of YAG laser with that of CO2 laser and found that with the YAG laser, only 15% to 26% of the incident light was absorbed by the adhesive material and changed to heat, while the rest reached the enamel surface, potentially damaging the pulp.  Other authors such as Ma et al (AJODO 1997), Tocchio et al (AJODO 1993), also showed that CO2 laser is effective for debonding ceramic brackets.
  55. 55. Iatrogenic effects of laser  When laser radiation is applied to a ceramic bracket, energy is absorbed and converted into heat  There is a potential for this heat to propagate to the tooth structure and eventually lead to pulp damage.  Zach and Cohen (1965) have shown in monkeys, that up to 1.8 ºC increase in intra pulpal temperature results in no pulpal damage, while with increase of 5.5 ºC , there was pulpal necrosis in 15 % of teeth.
  56. 56.  Ma et al ( AJODO 1997) showed that there is a linear relationship between lasing time and increase in intra pulpal temperature.  They found that application of an 18W CO2 laser for 2 seconds allowed debonding with a 1.48 MPa tensile load, with a mean intrapulpal temperature increase of 1.1ºC.  Obata et al (1995) found no histological differences in the tooth pulps of lased and non lased teeth.  Use of Super pulse lasers in surgery has been reported by Ben Baruch et al ( 1988) and Ho et al (1995). The super CO2 laser has short laser pulses of microseconds which allow for some time for tissues to cool, limiting damage to the pulp.
  57. 57.  Obata et al (EJO 1999) showed that super pulse CO2 laser was able to create debonding at 2 watts within a period of less than 4 seconds. During this period it caused increase in intra pulpal temperature of 1.4º C, which was within acceptable physiologic limits.  Super CO2 lasers may also induce vibration in the adhesion material , thus decreasing power output, and minimizing temperature increase.  In comparison, normal pulse CO2 lasers are more likely to cause thermal necrosis and charring .
  58. 58. Time lag between lasing and debonding:  Abdul Kader and Ibrahim (1999) reported that irrespective of lasing time, there was a significant increase in required debonding force, 1 minute after lasing, compared to immediately after lasing.  Therefore, debonding ceramic brackets one by one after lasing, before the adhesive resin material resolidifies, requires less debonding force. Effect of Laser on different bonding adhesives:  The popularly used adhesive materials for ceramic brackets are Concise, a Bis GMA resin with filler, and Super Bond : an MMA resin with 4META and no filler.
  59. 59.  Lasers are very effective in debonding ceramic brackets with either of the two, resulting in no enamel fractures.  Mimura et al (AJODO 1995) found however, that using laser it is easier to debond brackets bonded with Super-Bond.  In addition,laser tends to remove the Bis GMA resin along with the bracket, while with MMA resin, the adhesive remained on the tooth.  They thus concluded that with laser aided debonding of ceramic brackets, use of MMA is safer than Bis GMA.
  60. 60. Azzeh and Feldon (AJODO 2003) comprehensively reviewed the literature relating to laser debonding of ceramic brackets, and made the following conclusions:  Time and force spent to debond ceramic brackets is significantly less with the use of lasers, as also is the risk of enamel damage and bracket fracture.  CO2 super pulse laser is superior to normal pulse CO2 lasers and YAG lasers.  MMA resins are recommended over Bis GMA resins.  Use of monocrystalline brackets is suggested over polycrystalline brackets.  Ceramic brackets should be irradiated and debonded one by one immediately after laser exposure.
  61. 61. Risk of pulpal damage is significantly reduced if the following are used  Super pulse CO2 laser at 2W for less than 4 seconds.  CO2 laser (10.6 microns) at 3 W for 3 seconds  CO2 laser (normal pulse) at 18W for 2 seconds
  62. 62. A IV. Chemical solvents for debonding ceramic brackets peppermint oil material has been marketed previously as a debonding agent.  Larmour , McCabe Gordon (BJO 1998) assessed ex vivo the effects of peppermint oil application on the debond behaviour of ceramic brackets compared with ethanol and acetone which are recognized softening agents.  One hour placement in peppermint oil produced the lowest mean and maximal debond forces (77 and 114 N, respectively).  Placement in peppermint oil produced the lowest levels of retained resin.  There was no evidence of enamel fracture with any of the groups, but a problem. fracture remained
  63. 63. Finishing procedures during debonding.    Retief and Denys (Angle O 1979) described the removal of direct bonded attachments and the finishing of underlying enamel as an acute clinical problem. Using the scanning electron microscope they concluded that debonding pliers, scalers, and diamond finishing burs should not be used to remove the remaining resin after debonding because they cause deep gouges in the enamel. They recommended using a 12-bladed tungsten carbide bur at high speed with adequate air cooling to remove the bulk resin. finishing the residual resin and underlying enamel with graded polishing discs or ceramiste wheels with light pressure and adequate air cooling.
  64. 64.  Final finishing may be done with a water slurry of pumice applied with a rubber cup.  Other authors such as Zachrisson and Artun (AJO 1979) found that tungsten carbide bur at low speed produced the finest scratch pattern and the least enamel loss.  Rouleau et al (AJO 1982) on the other hand concluded that the instrument leaving the smoothest enamel surface was the tungsten carbide ultra-fine bur operated at high speed with water spray.  Hosein et al (AJODO 2004) compared enamel loss during debonding of brackets bonded with conventional and self-etch primers and reported that for both groups, most enamel loss occurred with high speed TC bur or ultrasonic scaler, while least occurred with slow speed TC bur.
  65. 65. Effects of Debonding on Enamel Features of Normal enamel:  Normal enamel varies considerably in appearance between young, adolescent and adult teeth.  Young teeth that have just erupted into the oral cavity are characterised clinically by perikymata, that run around the tooth in its entirety.  Under scanning electron microscope open enamel prisms are seen as small holes.
  66. 66.  In adult teeth, the perikymata are worn away and replaced by a scratched pattern.Cracks are frequently visible, electron microscopy shows no evidence of prism ends or perikymata.  Teeth in adolescents reflect an intermediate stage.  Mannerberg (1960) reported that normal wear of enamel is between 0-2 microns per year. On the other hand, a sand paper Scratched pattern of adult enamel disk that touches a tooth for only a fraction of a second leaves scratch marks up to 5 microns deep.
  67. 67. Influence of different debonding instruments on enamel:  Zachrisson and Artun (AJO 1979) showed that diamond instruments produced coarse scratches and gave a deeply marred apppearance to enamel.  Medium sandpaper disks and a green rubber wheel produced similar scratches that could not be polished away.  Fine sandpaper disks produced several considerable and some even deeper scratches.  Plain cut and spiral fluted tungsten carbide burs operated at about 25000 rpm were the only instruments that provided a satisfactory surface appearance.  However none of the instruments left the virgin tooth surface with its perikymata intact.
  68. 68.  Amount of enamel lost in debonding:  The amount of enamel lost during debonding is related to several factors such as instruments used for prophylaxis, debonding, and the type of adhesive resin used.  Initial prophylaxis with a bristle brush for 10 –15 seconds per tooth may abrade away up to 10 microns of enamel, compared to rubber cups which may abrade upto 5 microns of enamel.  Cleanup of unfilled adhesive resin may be accomplished with hand instrumentation only, and is associated with loss of 5-8 microns of enamel.  Adequate removal of filled resin generally needs rotary instrumentation and may involve 10-25 microns of enamel loss.
  69. 69.  In vitro studies using an optical system of a profile projector and steel reference markers show that total enamel loss for filled reins ranged from 30-60 microns depending upon the instrumentation. (Pus and Way, AJO 1980; Thompson and Way, AJO 1981).  On the other hand,Van Waes et al (AJODO 1997) using computerized 3 D scanning over the tooth surface found a more limited enamel loss ( 7.4 microns) if tungsten carbide burs were used carefully.
  70. 70. Enamel tearouts:  Localized enamel tearouts have been reported to occur during debonding of metal and ceramic brackets.  These are partly related to the type of filler material in the adhesive resin and to the location of bond breakage.  Smaller filler particles may penetrate deeper into the etched enamel than macrofillers.On debonding the small fillers reinforce the adhesive tags. Macrofillers, on the other hand create a more natural break point in the enamel adhesivesurface.
  71. 71. Ceramic brackets using chemical retention cause enamel damage more often, probably because the point of bond breakage is at the enamel-adhesive rather than adhesive-bracket surface.  Clinical implications: 1. Use brackets that have mechanical retention and debonding techniques that leave all or majority of composite on the tooth. 2. Avoid scraping away adhesive remnants with hand instruments. 
  72. 72. Enamel cracks  Cracks, occurring as split lines in the enamel are often overlooked at the clinical examination, and they do not show up on routine intra-oral photographs.  Finger shadowing in good light or preferably fiberoptic transillumination is needed for proper visualization.
  73. 73.    1. There is a distinct possibility that the sharp sound sometimes heard on removal of bonded orthodontic brackets with pliers is associated with the creation of enamel cracks. Zachrisson et al (AJO 1980) studied normal as well as debonded teeth and reported that the occurrence of vertical cracks is quite common, especially in maxillary central incisors and canines. Clinical implications; The orthodontist should review his debonding technique if he notices; Several distinct enamel cracks on the patient’s teeth after debonding, especially on teeth other than maxillary canines and central incisors
  74. 74.  2. If cracks are detected in a predominantly horizontal direction.  With ceramic brackets, the potential for creating cracks is far higher because of their lack of ductility, which may generate excessive stress at the adhesive –enamel interface.  Note: It is important for the orthodontist to notify the patient about any cracks present prior to treatment, in order to avoid being blamed for it post-treatment.
  75. 75. Enamel loss associated with adhesive removal from teeth with white spot lesions  Development of white spot lesions during orthodontic treatment is almost inevitable in patients with poor oral hygiene.  These can occur within only 2-3 weeks of plaque accumulation in gingival areas of teeth.  Studies have shown loss of upto 10% of inorganic content in these lesions, which has led to concern about further enamel loss during debonding.  Tufekci et al (AJO DO 2004) performed a study to assess the effect of debonding on teeth with WSL’s.
  76. 76.  They found that in teeth with white spot lesions, the use of abrasive (Sof-Lex) disks was associated with more enamel loss than slow speed TC burs.  Based on this, use of slow speed TC bur was recommended for adhesive removal in affected teeth.
  77. 77. Management of teeth with white spot lesions after debonding:  Artun and Thylstrup ( 1986) found that removal of cariogenic challenge after debonding results in the arrest of further demineralization, and gradual regression of lesion clinically takes place because of surface abrasion as well as some deposition of minerals.  Visible white spots that develop during orthodontic therapy should not be treated with concentrated fluoride agents immediately after debonding, because this procedure will arrest the lesion and prevent complete repair.
  78. 78.  At present, 2-3 months of good oral hygiene without fluoride supplementation should be recommended post debonding.  More fluoride may tend to precipitate calcium phosphate onto the surface and limit remineralization of the superficial part of the lesion, and the optical appearance of the white spot is not reduced.
  79. 79. Microabrasion  Done when remineralizing capacity of oral fluids is exhausted and white spots established.  Microabrasion: A gel prepared from 18% HCl, pumice and glycerine is applied professionally with a modified toothbrush tip for 3-5 mins; followed by rinsing.  This is effective for removing white spots and brownyellow enamel discolorations.  In case of more extensive mineral loss, grinding with diamond burs or composite restorations may be required..
  80. 80. White spot lesions After micro-abrasion
  81. 81. References  Hosein I, Sherriff M, Ireland AJ. Enamel loss during bonding, debonding, and cleanup with use of a selfetching primer.Am J Orthod Dentofacial Orthop. 2004 Dec;126(6):717-24.  Diaz C, Swartz M. Debonding a new ceramic bracket: a clinical study. J Clin Orthod. 2004 Aug;38(8):442-5  Tufekci E, Merrill TE, Pintado MR, Beyer JP, Brantley WA. Enamel loss associated with orthodontic adhesive removal on teeth with white spot lesions: an in vitro study. Am J Orthod Dentofacial Orthop. 2004 Jun;125(6):733-9.  Azzeh E, Feldon PJ. Laser debonding of ceramic brackets: a comprehensive review. Am J Orthod Dentofacial Orthop. 2003 Jan;123(1):79-83.
  82. 82.  Coley-Smith A, Rock WP. Distortion of metallic orthodontic brackets after clinical use and debond by two methods. Br J Orthod. 1999 Jun;26(2):1359.  Bishara SE, Olsen ME, VonWald L, Jakobsen JR. Comparison of the debonding characteristics of two innovative ceramic bracket designs.Am J Orthod Dentofacial Orthop. 1999 Jul;116(1):8692.  Obata A, Tsumura T, Niwa K, Ashizawa Y, Deguchi T, Ito M. Super pulse CO2 laser for bracket bonding and debonding. Eur J Orthod. 1999 Apr;21(2):193-8  Turner PJ. Trouble-free debonding in orthodontics: 2. Dent Update. 1996 Dec;23(10):426-9.
  83. 83.  Jost-Brinkmann PG, Radlanski RJ, Artun J, Loidl H. Risk of pulp damage due to temperature increase during thermodebonding of ceramic brackets. Eur J Orthod. 1997 Dec;19(6):623-8.  Bishara SE, Olsen ME, Von Wald L. Evaluation of debonding characteristics of a new collapsible ceramic bracket. Am J Orthod Dentofacial Orthop. 1997 Nov;112(5):552-9.  Kearns HP, Sandham JA, Bryan Jones W, Lagerstrom L. Electrothermal debonding of ceramic brackets: an ex vivo study.Br J Orthod. 1997 Aug;24(3):237-42.  Lee-Knight CT, Wylie SG, Major PW, Glover KE, Grace M. Mechanical and electrothermal debonding: effect on ceramic veneers and dental pulp.Am J Orthod Dentofacial Orthop. 1997 Sep;112(3):263-70.
  84. 84.  Sinha PK, Nanda RS. The effect of different bonding and debonding techniques on debonding ceramic orthodontic brackets. Am J Orthod Dentofacial Orthop. 1997 Aug;112(2):132-7  Ma T, Marangoni RD, Flint W. In vitro comparison of debonding force and intrapulpal temperature changes during ceramic orthodontic bracket removal using a carbon dioxide laser. Am J Orthod Dentofacial Orthop. 1997 Feb;111(2):203-10.  Takla PM, Shivapuja PK. Pulpal response in electrothermal debonding. Am J Orthod Dentofacial Orthop. 1995 Dec;108(6):623-9.  Seema Luthra, K Vighnesh, Nirmala Rao, Valiathan Ashima. Ceramic brackets and their electrothermal debonding-an in vivo evaluation. TIBAO 1998 Vol 12, No.2. 47-49.
  85. 85.     Tocchio RM, Williams PT, Mayer FJ, Standing KG. Laser debonding of ceramic orthodontic brackets.Am J Orthod Dentofacial Orthop. 1993 Feb;103(2):155-62 Bishara SE, Trulove TS. Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Part I. Background and methods. Am J Orthod Dentofacial Orthop. 1990 Aug;98(2):145-53. Graber, Vanarsdall. Orthodontics: Current Principles and Technique. 4th Edition (Mosby) 2005. Krell KV, Courey JM, Bishara SE. Orthodontic bracket removal using conventional and ultrasonic debonding techniques, enamel loss, and time requirements Am J Orthod Dentofacial Orthop. 1993 Mar;103(3):258-66.
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