BONDING in orthodontics techniques .pptx

BONDING in orthodontics techniques

1. BONDING IN ORTHODONTICS 1 DR PRINCYMOL FIRST YEAR MDS DEPT.ORTHODONTICS

2. CONTENTS Introduction History Materials and Devices Used in Orthodontic Bonding Brackets Adhesives Composite Resins Glass Ionomer Cements Light Sources Bonding to Enamel Bonding to Artificial Tooth Surfaces Indirect Bonding Rebonding Debonding conclusion Rebonding Debonding Conclusion 2

3. INTRODUCTION “ Bonding is mechanical locking of an adhesive to irregularities in the enamel surface of the tooth and to mechanical locks formed in the base of orthodontic attachment .” Successful bonding depends on three components •Tooth surface & its preparation •Design of attachment base •Bonding Material 3

4. 4 HISTORY

5. YEARS AUTHORS IMPORTANT EVENTS 1955 Buonocore Introduced etching tooth surfaces with phosphoric acid—85% phosphoric acid for 30 s 1962 Bowen Bowen’s Resin— bisphenol A- glycidyl dimethacrylate 1965 Newman Epoxy resin bonding orthodontic resins— diglycidyl ether of bisphenol -A with a polyamide curing agent 1968 Smith Bracket bonding with zinc polyacrylate cement 1971 Miura et al Acrylic resin ( orthomite ) 1972, 1976 Silverman and Cohen Pioneers of indirect bonding technique 1973 1974 1977 2005 2010 Retief Silverstone Gorelick Zachrisson and Büyükyılmaz Øgaard and Fjeld Üs¸umez and Erverdi Etching modifications: 50%phosphoric acid concentration 30%–50% phosphoric acid concentration 35%–38% orthophosphoric acid 5

6. YEARS AUTHORS IMPORTANT EVENTS 1977 Zachrisson First detailed published large sample data on posttreatment evaluation of direct bonding 1979 Takao Fusayama Total etch technique 1979 Maijer and Smith Crystal growth technique 1982 Nobuo Nakabayashi Resin reinforced hybrid layer 1992 J. Kanca et al. Moist bonding technique 1993 1997 2007 Hermsen and Vrijhoef Olsen and Bishara Bas - Kalkan and Orhan 10% Maleic acid, polyacrylic acid as etchants 1999 Sondhi A Sondhi Rapid-Set Indirect Bonding Adhesive 6

7. BONDING OVER BANDING Esthetically superior. F aster and simple. L ess discomfort for the patient Arch length is not increased by band material It allows more precise bracket placement even in tooth with aberrant shape. Improved gingival health Better access for cleaning 7

8. The ability to bond partially erupted and malaligned teeth enables early force application during treatment - Mesiodistal enamel reduction ( proximal reduction) is possible during treatment. Attachments may be bonded to artificial tooth surfaces ( eg ., amalgam, porcelain, gold) and to fixed bridge work. Interproximal areas are accessible for composite buildups. Caries risk under loose bands is eliminated. No band spaces are present to close at the end of treatment. Brackets may be recycled, further reducing the cost. Lingual brackets, invisible braces, can be used when patient aesthetics is important 8

9. Disadvantages Weaker attachment Better access for cleaning doesn’t guarantee better oral hygiene and improved gingival condition Protection against interproximal caries of well contoured bands is absent Bonding generally not indicated on teeth where lingual auxiliaries are required or where headgears are attached Rebonding requires more preparation Debonding is more time consuming. 9

10. MATERIALS AND DEVICES USED IN ORTHODONTIC BONDING Brackets – ceramic,metal Adhesives Light sources 10

11. Brackets The two most common types of orthodontic attachments are - stainless steel ceramic brackets 11

12. CERAMIC BRACKETS M achined from monocrystalline or polycrystalline aluminum oxide . Combine the aesthetics of plastic and the reliability of metal brackets. Ceramic brackets bond to enamel by : (1) mechanical retention via indentations and undercuts in the base (2) chemical bonding by means of a silanecoupling agent. 12

13. With mechanical retention, the stress of debonding is generally at the adhesive–bracket interface The chemical bonding may produce excessive bond strengths, with the stress at debonding shifted toward the enamel–adhesive interface Chemically cured and light-cured adhesives are useful for ceramic brackets 13

14. METAL BRACKETS Mechanical retention mesh structure - most common Bracket-base designs – standard mesh base supermesh base integral base microetched base laser-structured base 14

15. Mesh pad is the system most commonly used for retention. A new type of laser-structured base retention was found to produce double the bond strength produced by foil mesh without compromising debonding characteristics 15

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17. Base of the bracket Bracket has to bond either chemically /mechanically Mechanical interlocking Base attachments – Mesh base designs Non-mesh design 17

18. Base attachments MESH TYPE BASES - Foil mesh base - Mini mesh base - Micro mesh base - Laminated mesh base - Dyna bond base - Ormesh wide central - Supermesh MB base 18 NON-MESH TYPE BASES -Micro-loc base - Dyna lock integral base - Micro etch base -Peripheral perforated base - Laser structured base

19. 19 MESH TYPE BASES Foil mesh base DYNA bond mesh BASE Ormesh base Super mesh base

20. 20 LASER STRUCTURED BASE DYNA-LOCK INTEGRAL BASE MICRO-LOC BASES MICRO ETCH BASE Non Mesh type of bases

21. Adhesives Composite Resins Originated in Bowen’s classic work on the development of the monomer 2,2-bis-4(2-hydroxy-3 methacrylloxypropoxy phenylpropane. The essential chemistry of the synthesis of this substance is the reaction of glycidyl methacrylate with bisphenol A to create a molecule informally known as bisphenol A– glycidyl methacrylate ( bisGMA ). 21

22. BisGMA is the basis of most of the contemporary composite resin systems clinically used today. Polymerization of composite resins can be initiated chemically or by light exposure 22

23. No-mix adhesives . No-mix adhesives set when one paste under light pressure is brought together with a primer fluid on the etched enamel and bracket backing or when another paste on the tooth is to be bonded 23

24. Light-polymerized adhesives allows practitioners the freedom to choose when to initiate the adhesive curing cycle after bracket placement introduced in 1970s the curing process begins when a photoinitiator is activated. Most dental photoinitiator systems use camphoroquinone as the diketone absorber, with the absorption maximum in the blue region of the visible light spectrum at a wavelength of 470 nanometers (nm). 24

25. Advantages useful in situations during which a quick set is required, such as when rebonding one loose bracket or when placing an attachment on an impacted tooth after surgical uncovering, when the risk of blood contaminationis present. Light-cured adhesives are also advantageous when extended working time is desirable, which is usually the case when difficult premolar bracket positions need to be checked and rechecked with a mouth mirror before the bracket positioning is considered optimal 25

26. Primers. sealant permits a relaxation of moisture control because controlling moisture is no longer critical after resin coating. Sealants also provide cover for enamel in areas of adhesive voids, which is probably especially valuable with indirect bonding. The caries protection of sealant around the bracket base is more uncertain, and further studies are needed on the clinical merits of fluoride-containing sealants. 26

27. Moisture-Insensitive Primers To reduce the bond failure rates under moisture contamination, hydrophilic primers that can bond in wet fields have been introduced as a potential solution. For optimal results, the moisture-insensitive primers should be used with their respective adhesive resins. The hydrophilic resin sealants or primers polymerize in the presence of a slight amount of water, but they will not overcome routine saliva contamination 27

28. When bonding to enamel, the resin sealant or resin primer must be placed onto the prepared enamel before the pellicle (biofilm) formation from the saliva, which is not particularly difficult but is crucial to a successful enamel bond. Examples: Transbond MIP, 3M Unitek,Monrovia , CA; Assure or Assure Plus, Reliance Orthodontic Products, Itasca, IL) 28

29. Self-Etching Primers. The unique characteristic of these bonding systems is that they combine the conditioning and priming agents into a single acidic primer solution for simultaneous use on both enamel and dentin; therefore separate acid etching of the enamel and subsequent rinsing with water and air spray is not required 29

30. The active ingredient of the SEPs is a methacrylate phosphoric acid ester that dissolves calcium from hydroxyapatite MECHANISM The phosphate group of methacrylated phosphoric acid ester dissolves calcium and remove from hydroxyapatite the removed calcium forms a complex and is incorporated into the network when the primer polymerizes. Etching and monomer penetration to the exposed enamel rods are simultaneous, and the depth of etch and primer penetration is identical. 30

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32. mechanisms act to stop the etching process The acid groups attached to the monomer are neutralized by forming a complex with calcium from hydroxyapatite. as the solvent is driven from the primer during the airburst step,the viscosity rises, slowing the transport of acid groups to the enamel interface. as the primer is light cured and the primer monomers are polymerized, transport of the acid groups to the interface is stopped . 32

33. The minimal etch obtained with the SEPs indicates that the majority of the bond may be more of a chemical bond with the calcium in the enamel than the mechanical bond achieved with a conventional phosphoric acid etch Instead of the well-known distinct honeycombed structure with microtag and macrotag formation an irregular but smooth hybrid layer, 3 to 4 microns thick, and irregular tag formation with no apparent indentations of enamel prism or core material are found. 33

34. Glass Ionomer Cements Introduced in 1972, primarily as luting agents and as a direct restorative material, with unique properties for chemically bonding to enamel, dentin, and stainless steel and being able to release fluoride ions for caries protection . Modified to produce dual-cure or hybrid cements Glass ionomer and light-cured glass ionomer cements are the material of choice for cementing bands They are stronger than zinc phosphate and polycarboxylate cements, with improved adhesion to enamel and metal and less demineralization at the end of treatment. 34

35. LIGHT SOURCES 35

36. Halogen lights-conventional Most common source of blue light since 1970’s has been quartz tungsten halogen Halogen bulbs produce light when electric energy heats a small tungsten filament to high temperature Can cure orthodontic composite resin-20 seconds Light cured RMGIC 40sec 36

37. Use camphorquinone as absorber with absorption maximum in the blue region of the visible light spectrum at a wavelength of 470nm 37

38. Disadvantages Light power output is less than 1% of the consumed electric power Limited lifetime of 100 hrs because of degradation of components of the bulb by the high heat generated Prolonged curing time inconvenient for clinician and patient 38

39. Polymerization is initiated when a critical concentration of free radicals is formed. This requires particular no. of photons to be absorbed by the initiatior system. Fast halogens- higher intensity output accomplished by higher output lamps or using turbo tips that focus light and concentrate it into a smaller area.

40. Never turn off a halogen unit if the fan is still running. This will help to extend the life of the unit. The light guide must also be kept free of resin build up on the end. Either use a sleeve cover to protect the light guide or use some acetone to remove any residue that has formed. 40

41. Argon lasers Late 1980’s argon lasers promised to reduce curing time dramatically. Excited ions in an argon filled chamber produce a light that is focused and passed through the hand piece. They produce a highly concentrated beam of light centered around the 480nm wavelength. Light is collimated which results in more consistent power density over distance.

42. Advantages Protects enamel surface against decalcification reduces enamel demineralization around orthodontic brackets Curing time - 5 sec for unfilled resins - 10 sec for filled. Disadvantages High cost Poor portability Narrow output which sometimes did not cure all the resins.

43. Plasma arc lights Mid 1990’s the xenon plasma arc lamp was introduced for high intensity curing of composite resins in restorative dentistry. Plasma arc curing was introduced with a 3 second cure Lamp has tungsten anode and cathode in a quartz tube filled with xenon gas.

44. White light is filtered to blue wavelengths with a narrow spectrum between 430 and 490 nm. The plasma arc lights are contained in base units rather than in guns because of high voltage and heat generated. Whereas conventional halogen bulbs emit light with energy level of 300 mW , plasma arc lamp has a much higher peak energy level of 900mW.

45. Advantages polymerization can be done in shorter time Use for 5- 10 sec is safe regarding pulp temperature. Disadvantages They require filters Generate heat Expensive. It is suggested that two 3 sec cycles of curing is more beneficial than 1 cycle of 6 sec; moving the light after 3 sec of exposure not only minimizes any pulpal temperature effects , but it also provides a better distribution of light energy under bracket base.

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47. 1995 Mills et al proposed solid state LEDs for polymerization. Use junctions of doped semiconductors to generate light. They directly emit light in the blue region. Light emitting diodes

48. Advantages Have small size, are cordless generate minimal heat Life time of > 10000 hrs Undergo little degradation of output over this time Require no filters to produce blue light Resist shock and vibration Take little power to operate.

49. For success in bonding with light activated resins, bracket should be exposed to the curing light immediately after placement. Keep the time interval between placement and curing to a minimum. 49

50. BONDING 50

51. BONDING TO ENAMEL The steps of direct or indirect bracket bonding on facial or lingual surfaces of teeth are as follows: 1.PREMEDICATION 2. CLEANING 3.ENAMEL CONDITIONING 4.SEALING AND PRIMING 5.BONDING 51

52. 1 .PREMEDICATION Initial activation of orthodontic attachments may cause significant discomfort to the patient Naproxen sodium 550mg 1hr before archwire placement have significantly low levels of of pain at 2hrs,6hrs and night time 52

53. 2, 2.CLEANING Cleaning of the teeth with pumice removes plaque and the organic pellicle that normally covers all teeth. One must exercise care to avoid traumatizing the gingival margin and initiating bleeding on teeth that are not fully erupted. Improves the effectiveness of etching Bond strength appears to be unaffected if pumice used or not. Creation of surface irregularities microporosities and increasing the surface area. 53

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55. 3. ENAMEL CONDITIONING - MOISTURE CONTROL -ENAMEL PRETREATMENT

56. MOISTURE CONTROL salivary control and maintenance of a dry working field are essential after rinsing and drying. Lip expanders and cheek retractors Saliva ejectors Tongue guard with bite blocks Salivary duct obstructors Gadgets that combine several of these (saliva ejector, tongue holder, and bite block). Cotton or guaze rolls Antisialagogues . 56

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58. ENAMEL PRETREATMENT Conventional Acid Etching Necessary to make successful bonds Most commonly used etchant is 37% orthophosphoric acid for 15 to 30 seconds After etching,the etchant is rinsed of the teeth with abundant water spray 58

59. A high speed evacuvator is strongly recommended for increased efficiency in collecting etchant water Salivary contamination of the etched surface should best be avoided . If contamination occurs, then rinsing with the water spray or re-etching for a few seconds is recommended Since blood contamination has been shown to decrease the shear bond strength (SBS), teeth that are contaminated with blood should be rerinsed and dried 59

60. The teeth are thoroughly dried with a moisture and oil free air source to obtain the well-known dull, frosty appearance Teeth that do not appear dull and frosty white should be re-etched. 60

61. bleaching with 35% hydrogen peroxide significantly reduces bracket adhesion when bonded 24 hours after bleaching . no significant adverse effect of bleaching seems to occur after 7 days For deciduous teeth sandblast with 50 microns of aluminum oxide for 3 seconds to remove some outermost aprismatic enamel and then etch for 30 seconds with phosphoric acid gel is recommended Flurotic enamel is either sandblasted to promote microscopic conditioning or treated with 5.2% NaOCl for 1 minute to remove the exess of protein content before proceeding to conventional etching. 61

62. A routine etching removes 3 to 10 microns of surface enamel. Another 25 microns reveal subtle histologic alterations creating the necessary mechanical interlocks laboratory studies indicate that the enamel alterations are largely (although not completely) reversible, the overall effect of applying an etchant to healthy enamel is not detrimental . 62

63. LASER ETCHING Laser treatment of dental enamel causes thermally induced changes within the enamel to a depth of 10to 20 μ m . etching takes place through a process of continuous vaporization and microexplosions due to vaporization of water trapped within the hydroxyapatite matrix The degree of surface roughening is dependent on the system used and the wavelength of the laser. Produce lower bond strength than acid etch 63

64. The surface produced by laser etching is also claimed to be acid resistant as a result of the modified calcium-to-phosphorus (Ca/P) ratio, a reduced carbonate-to-phosphate ratio, and the formation of more stable and less acid-soluble compounds, thus reducing susceptibility to acid attack and caries. 64

65. SEALING AND PRIMING After the teeth are completely dry and frosty white, a thin layer of bonding agent (sealant, primer) may be painted over the etched enamel surface The coating may be thinned by a gentle air burst for 1 to 2 seconds Bracket placement should be immediately started after all of the etched surfaces are coated . Separate curing of the bonding agent is not necessary when light cured products are used Reapplication of the sealed layer is not required when saliva contamination occurs, but the area should be air dried before bracket placement . 65

66. BONDING Immediately after all teeth to be bonded have been painted with sealant, the operator should proceed with the actual bonding of the attachments. The recommended bracket bonding procedure consist of the following steps 1.TRANSFER 2.POSITIONING 3.FITTING 4.REMOVAL OF EXCESS 5. CURING 66

67. TRANSFER The bracket is gripped with reverse action tweezer (bracket holding forceps) and the adhesive is applied to the back of the bonding base. The bracket is immediately placed on the tooth close to its correct position. 67

68. TRANSFER

69. POSITIONING The mandibular molar and premolar bracket wings must be kept out of occlusion, or the brackets may easily come loose. Therefore before positioning the brackets, the operator should do the following: The patient is asked to bite with his or her teeth together; the operator should then evaluate the tooth area available for bonding. 2. The mandibular posterior brackets are bonded out-of-occlusion, which may necessitate adjusting bends in the archwires . 69

70. Later, the clinician uses a placement scaler to position the brackets mesiodistally and incisogingivally and to angulate them accurately, relative to the long axis of the teeth . Proper vertical positioning may be enhanced by different measuring devices or height guides. A mouth mirror will aid in horizontal positioning, particularly on rotated premolars 70

71. Because of human limitations in the direct placement of brackets on both anterior and posterior teeth, using archwire bends or bracket repositioning to compensate for the inherent inaccuracies in bracket positions is still necessary. Placing the brackets too far gingivally should be avoided, unless dictated by the opposing teeth This leads to incomplete expression of the torque value built into the bracket and improper hygiene conditions. 71

72. Positioning

73. FITTING Next, the clinician turns the scaler and with one-point contact with the bracket, pushes firmly toward the tooth surface. The clinician should remove the scaler after the bracket is in the correct position and should make no attempts to hold the bracket in place with the instrument Totally undisturbed setting is essential for achieving adequate bond strength. 73

74. Tight fit will result in Good bond strength Little material to remove on debonding Optimal adhesive penetration into bracket backing Reduced slide when excess material extrudes peripherally.

75. REMOVAL OF EXCESS A slight bit of excess adhesive is essential to minimize the possibility of voids and to be certain that the adhesive will be buttered into the bracket backing when the bracket is being fitted. The excess is particularly helpful on teeth with abnormal morphology. Excess adhesive will not be worn away by toothbrushing and other mechanical forces; it must be removed (especially along the gingival margin) with the scaler before the adhesive has set or with burs after setting. 75

76. Prevents or minimizes gingival irritation, plaque build up around the periphery of bonding base It also reduces periodontal damage and possibility of decalcification Improves esthetics not only by providing a neater and cleaner appearance but also by eliminating exposed adhesive that might become discolored in the oral environment. 76

77. CURING Today’s light sources present different curing modes, including soft start modes to decrease polymerization contraction. polymerization contraction is irrelevant to the orthodontic setting where the bracket or the orthodontic attachment is actually free floating Therefore presetting the light-curing unit to the maximum available setting or to the boost mode is advisable. 77

78. Recent studies demonstrate no significant differences between the SBS values of brackets with curing distances of 0 to 4 mm The light is best initiated after being placed at the correct position and angulation as close to the bracket base as possible Divergent photon release will be avoided and curing efficiency increased if the light guide is brought into contact with the bracket after an initial cure of 1 to 2 seconds 78

79. Many manufacturers advise curing metal brackets from mesial and distal, direct bond molar tubes from mesial and distal or occlusal, and ceramic brackets through the bracket Most current light sources can cure adhesives in approximately 10 or 5 seconds per metallic and ceramic brackets, respectively. 79

80. A new plasma-emulating LED (VALO Ortho, Ultradent Products,Inc ., South Jordon, UT) was demonstrated to cure resin under brackets in as few as 3 seconds One clinical concern with this light source is the high heat reported by the patients at the gingiva, which is well tolerated when the patients are informed in advance. 80

81. laboratory studies, one of which was conducted under simulated blood circulation, the temperature increase in the pulp chamber was confirmed at 1.74° C, which is significantly lower than those resulting from longer exposures at lower power settings. However, not every resin is compatible with every light source, and each combination should be individually assessed to achieve optimal results 81

82. Bonding to Artificial Tooth Surfaces 82

83. PORCELAIN ZIRCONIA AMALGAM GOLD COMPOSITE 83

84. Bonding to Porcelain Etchant - 9.6% hydrofluoric acid in gel form for 1 to 2 minutes The etchant creates microporosities in the porcelain structure achieve a mechanical interlock with the composite resin Frosted appearance 84

85. For optimal bonding of orthodontic brackets and retainer wires to porcelain surfaces, the following technique is recommended 1. Adequately isolate the working field, and bond the actual crown separately from the other teeth. 2. Use a barrier gel such as Kool Dam ( PulpdentCorporation,Watertown , MA) on mandibular teeth whenever a risk exists that the hydrofluoric acid etching gel may flow into contact with the gingiva or soft tissues. 85

86. Deglaze an area slightly larger than the bracket base by sandblasting with 50 microns of aluminum oxide for 3 seconds. 4. Etch the porcelain with 9.6% hydrofluoric acid gel for 2 minutes. 5. Carefully remove the gel with a cotton roll, and then rinse using high-volume suction Apply a thin layer bonding agent over the etched enamel surface and bond the bracket 86

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88. Alternatives to Hydrofluoric acid Acidulated phosphate fluoride gel Irradiation of ceramic surface with CO2 Er:YAG lasers Silica coating 88

89. Hydrofluoric acid will not be effective for bonding to high-alumina porcelains and glass ceramics, and new technique improvements are needed for successful orthodontic bonding to such teeth 89

90. Bonding to zirconia Polycrystalline zirconia primarily consist of yttria –stabilized tetragonal zirconia polycrystals and is a frequently used ceramic system in load bearing areas with aesthetic demands Acid resistant (doesn’t contain silica particles) Therefore application of primers or bonding systems with functional monomers on zirconia ( eg:10 methacryloxydecyl dihydrogen phosphate ) on the roughened surface is recommended to increase the bond strength 90

91. Techiques for optimal bonding 1.deglaze an area slightly larger than the bracket base by sandblasting with 30 to 50 microns of aluminium oxide for 20 seconds 2. rince and dry the restoration surface 3.when bonding a metallic bracket, apply a ceramic primer ( clearfill ceramic powder)on the zirconia surface .apply primer on the bracket base too when bonding a ceramic bracket 4. dry the entire adherent surface sufficiently using mild ,oil free air flow and bond the bracket 91

92. Bonding to Amalgam Small amalgam filling with surrounding sound enamel. 1. Sandblast the amalgam alloy with 50 microns of aluminum oxide for 3 seconds 2. Condition the surrounding enamel with 37% phosphoric acid for 15 seconds. 3. Apply sealant, and bond with composite resin. Ensure the bonded attachment is not in occlusion with antagonists 92

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94. Large amalgam restoration or amalgam only. 1. Sandblast the amalgam filling with 50 microns of aluminum oxide for 3 seconds 2. Apply a uniform coat of Reliance Metal Primer (Reliance Orthodontic Products, Itasca, IL), and wait for 30 seconds(or use another comparable primer according to the manufacturer’s instruction). 3. Apply sealant, and bond with composite resin. Ensure the bonded attachment is not in occlusion with antagonists. 94

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96. Bonding to Gold Intraoral Sandblasting Electrolytic tin plating Plating with gallium-tin solution 96 Use of different intermediate primers and adhesives that bond chemically to precious metals ( Panavia ).

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98. Bonding to Composite Restoratives The bond strength obtained with the addition of new composite to mature composite is substantially less than the cohesive strength of the material However, brackets bonded to a fresh, roughened surface of old composite restorations after thorough air drying appear to be clinically successful in most instances Souface roughening with diamond bur Etching with phosphoric acid 98

99. INDIRECT BONDING 99

100. The brackets are glued with a temporary material to the teeth on the patient’s models, transferred to the mouth with a tray into which the brackets become incorporated, and then simultaneously bonded with a bisGMA resin. Most current indirect bonding techniques are based on a modification introduced by Thomas which attaches the brackets with composite resin to form a custom base . A transfer tray of silicone putty or thermoplastic material is used, and the custom bracket bases are then bonded to the teeth with a chemically cured sealant 100

101. Indirect Bonding with Composite Custom Bracket Base 1 .Take an impression, and pour a stone (not plaster) model. 2. Select brackets for each tooth. 3. Isolate the stone model with a separating medium. 4. Attach the brackets to the teeth on the model with lightcured or thermally cured composite resin, or use adhesive precoated brackets. 5. Check all measurements and alignments. Reposition if needed 101

102. 6. Make a transfer tray for the brackets. The material can be putty silicone, thermoplastics, or similar. 7. After removing the transfer trays, gently sandblast the adhesive bases with a microetching unit, taking care not to abrade the resin base. 8. Apply acetone to the bases to dissolve the remaining separating medium. 9. Prepare the patient’s teeth for a direct application 102

103. 10. Apply Sondhi Rapid-Set (3M Unitek , Monrovia, CA) resin A to the tooth surfaces and resin B to the bracket bases. If Custom I.Q. (Reliance Orthodontic Products, Itasca, IL) is used, then apply resin B to the teeth and resin A to the bases. Alternatively,apply a thin coat of the mixture of part A and part B adhesive to each custom resin base in the indirect bonding tray and to the tooth surface if using Transbond IDB Pre-Mix Chemical Cure Adhesive (3M Unitek, Monrovia, CA) 103

104. 11. Seat the tray on the prepared arch, and apply equal pressure to the occlusal, labial, and buccal surfaces with the fingers. Hold for a minimum of 30 seconds, and allow for 2 minutes or more of curing time before removing the tray. 12. Remove excess flash of resin from the gingival and contact areas of the teeth with a scaler or contra-angle handpiece and tungsten carbide bur. 104

105. 105 Indirect bonding using a Memosil 2 clear transfer tray (Heraeus Kulzer, Armonk,NY ) and a light cure adhesive

106. 106 Indirect bonding using light-cured base composite ( Transbond XT, 3M Unitek,Monrovia , CA) and chemically cured sealant ( Sondhi Rapid Set, 3M Unitek , Monrovia, CA).

107. Advantages brackets can be more accurately positioned in the laboratory the clinical chair time is decreased. cost effectiveness similar adhesive quality and bracket survival rate with those of direct bonding. Clinical chair time is decreased Marginal ridges are better leveled 107

108. DISADVANTAGES Technique sensitive Chairside procedure is more crucial, at least for inexperienced clinicians Removal of excess adhesive can be more difficult and more time consuming with some techniques The risk for adhesive deficiencies under the brackets is greater The risk for adhesive leakage to interproximal gingival areas can disturb oral hygiene procedures; and the failure rates with some methods seem to be slightly higher. 108

109. REBONDING 109

110. The adhesive remaining on the loose bracket is best treated by sandblasting until all visible bonding material is removed from the base. Any adhesive remaining on the tooth surface is removed with a tungsten carbide The tooth is then etched with phosphoric acid gel for 30 seconds. On inspection the enamel surface may not be uniformly frosty because some areas may still retain resin. The phosphoric acid will re-etch any exposed enamel and remove the pellicle on any exposed resin. 110

111. After priming, the bracket is rebonded . The neighboring brackets are first religated , and then the rebonded bracket is ligated the brackets’ SBS decreased as the size of the aluminum oxide particle used for sandblasting increased and as recycling was repeated. a loose ceramic bracket should best be replaced with a new, intact bracket for optimal bond strength. 111

112. DEBONDING 112

113. DEBONDING OBJECTIVE to remove the attachment and all the adhesive resin from the tooth to restore the surface as closely as possible to its pretreatment condition without inducing iatrogenic damage CLINICAL PROCEDURE (1) bracket removal (2) removal of residual adhesive Whether metal or ceramic, the brackets should be individually removed to avoid force transfer from tooth to tooth, which may increase the risk of enamel crack formation 113

114. Removal of Steel Brackets place the tips of a twin-beaked pliers against the mesial and distal edges of the bonding base and cut the brackets off between the tooth and the base.. A gentler technique is to squeeze the bracket wings mesiodistally and then lift the bracket off with a peel force. This technique is particularly useful on brittle, mobile, or endodontically treated teeth. 114

115. A peel force, as in peeling an orange, creates peripheral stress concentrations that cause bonded metal brackets to fail at low force values The flexion of the metal body also helps breaking of the mechanical bond between the bracket and the adhesive resin 115

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117. Removal of Ceramic Brackets Wood burning pens Warm air dryers Electrochemical debonding devices Ultrasonic instruments These methods thermally soften the adhesive by heat transmission through the ceramic bracket 117

118. More recent ceramic brackets have a mechanical lock base and a vertical slot that will collapse the bracket by squeezing. Debonding collapsible ceramic brackets with the archwire in place and ligated to hold together the debonded bracket parts is recommended. Er:YAG LASER - laser energy is transferred through the ceramic and absorbed at the composite layer where microexplosions occur, resulting in the detachment of the bracket without any thermal damage to the tooth 118

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121. Enamel Tearouts and Cracks (Fracture Lines ) Most common in maxillary central incisor and canine Clinical precautions to taken are; (1) to use brackets that have mechanical retention and debonding instruments and techniques that primarily leave all or the majority of composite on the tooth (2) to avoid scraping away adhesive remnants with hand instruments. 121

122. Removal of Residual Adhesive Debonding of brackets usually leaves a residual adhesive volume of 0.6 to 2.48 mm3 on the enamel surface. The preferred method for the removal of excess adhesive is to use a suitable dome-tapered tungsten carbide bur (No. 1171 or No. 1172) in a contra-angle handpiece Clinical experience and laboratory studies indicate that approximately 30,000 rpm is the optimum for rapid adhesive removal without enamel damage. Light painting movements of the bur should be used so as not to cause deep scratches on the enamel. Water cooling should not be used when the last remnants are removed because water lessens the contrast with enamel 122

123. Speeds higher than 30,000 rpm using fine fluted tungsten carbide burs may be useful for bulk removal but are not indicated closer to the enamel because of the risk of marring the surface When all the adhesives has been removed ,the tooth surface may be polished with pumice (or a commercial prophylaxis paste)in a routine manner 123

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125. CONCLUSION Successful bonding in orthodontics requires careful attention to three components of the system: the tooth surface and its preparation, the design of the attachment base, and the bonding material itself. The future of bonding is promising. Product development in terms of adhesives, brackets, and technical details is continually occurring at a rapid rate. It is necessary for the orthodontist to update and stay oriented. 125