Bonding Procedure
Steps involved in direct and indirect bracket bonding on facial or lingual surfaces are as follows;
1. Cleaning
2. Enamel conditioning
3. Sealing
4. Bonding
Direct Bonding
1. Cleaning
Thorough cleaning of the teeth with pumice is essential to remove plaque and the organic pellicle that normally covers all teeth. Cleaning is done using rotary instruments, either a rubber cup or polishing brush.
2. Enamel Conditioning
A. Moisture control
After the rinse, salivary control and maintenance of a completely dry working field is absolutely essential. Some of the measures used are;
q Lip expanders and / or cheek retractors
q Saliva ejectors
q Tongue guards with bite blocks
q Saliva duct obstructers
q Cotton or gauze rolls
q Antisialagogues (generally not needed, when indicated, banthine tablets 50mg per 100 lbs body weight 45 kgs.) in sugar free drink 15 minutes before bonding, may provide adequate results.
B. Enamel Pretreatment
After the operating field has been isolated, the teeth to be bonded are dried. The conditioning solution or gel, 37% H3PO4 is lightly applied over the enamel surface with a foam pellet, brush for 60 seconds.
At the end of etching period, the etchant is rinsed off with abundant water spray.
Teeth are thoroughly dried with a moisture and oil free source to obtain dull frosty appearance. Salivary contamination of the etched surface must not be allowed.
Study of etched enamel surface under Scanning Electron Microscope
Various studies have been carried out to define optimal concentrations of the acid used for etching and the duration of etching with H3PO4. These investigations include study of the etched enamel surface pattern under Scanning Electron Microscope highlighting the loss of enamel, test of shear bond strength of a bonded attachment to a correlated etchant concentration and duration of etching and the trauma to the enamel and the amount of adhesive on the surface of enamel subsequent to debonding.
Diedrich typed action of the etchant on the enamel in three stages
Honeycomb pattern of the etched enamel (initially periphery of the prism head is delineated by micro clefts [0.1 to 0.2 micro meter]) continued action of acid leads to loss of substance predominantly in the area of prism cores with simultaneous conservation of the marginal areas.
Least amount of enamel is lost in this etch pattern designated as Type I.
As action of acid proceeds, there is dissolution of crest like marginal ridges, while the marginal clefts continue to widen. This is the transitional zone of central and peripheral etching pattern, in which existing marginal ridges are elevated approximately to 3 micro meter designated as Type III.
Peripheral etching pattern is an advanced stage in which the fragile prism peripheries break off. Maximum enamel loss takes place in this stage designated as Type II.
The above mentioned patterns of the etched enamel surface were named as Type I, II and III by Silverstone et al.
Galil and Wright described Type IV and Type V etching patterns.
Type IV etch pattern is commonly seen in cervical areas. It shows pitted irregular pattern and displays no rod or prism pattern.
Type V shows no pattern of prism outline. Enamel surface is extremely flat and smooth and they lack micro irregularities for penetration of resin.
3. Sealing
After teeth are completely dried and appear frosty white, a thin layer of sealant is applied over the entire etched enamel surface with a small foam pellet or brush with a single gingivoincisal stroke.
The sealant coating should be thin and even because excess sealant may induce bracket drift and unnatural enamel topography when polymerized. Bracket placement should be started immediately after all etched surfaces are coated with sealant.
Research is going on to determine the exact function of the sealant in acid etch procedure.
1. Some investigators conclude that sealant is necessary to achieve proper bond strength.
2. Sealant permits a relaxation of moisture control.
3. It permits easier bracket removal.
4. It protects against enamel tearouts at debonding.
Ceen and Gwinnett found that light polymerized sealants protect enamel adjacent to brackets from dissolution and subsurface lesions, whereas, chemical curing sealants polymerized poorly, exhibit drift, and have low resistance to abrasion.
4. Bonding
At present, the majority of clinicians routinely bond brackets with the direct rather than the indirect technique.
The recommended bracket bonding procedure consists of the following steps;
1. Transfer
2. Positioning
3. Fitting
4. Removal of excess
1. Transfer
The Clinician grips the bracket with a pair of cotton pliers or a reverse action tweezer and then applies the mixed adhesive to the back of the bonding base. The bracket is immediately placed on the tooth close to its correct position.
2. Positioning
A placement scaler, such as the RM 349 or, preferably, one with parallel edges, is used to position the brackets mesiodistally and incisogingivally and angulate them correctly.
The placement scaler with parallel edges allows visualization of the bracket slot relative to the incisal edge and long axis of the teeth, with the scaler seated in the slot.
Proper vertical positioning may be enhanced by different measuring devices (Boon’s gauge) or height guides on the brackets themselves.
A mouth mirror will aid in horizontal positioning particularly on rotated premolars.
3. Fitting
Next, the scaler is turned, and with one – point contact with the bracket, it is pushed firmly toward the tooth surface. The tight fit will result in good bond strength, little material to remove on debonding, and reduced slide when excess material extrudes peripherally.
The scaler should be removed after the bracket is in correct position and no attempts should be made to hold the bracket in place with the instrument.
Totally undisturbed setting is essential for achieving adequate bond strengths.
4. Removal of Excess
A slight bit of excess adhesive is essential to minimise the possibility of voids and to be certain that it will be buttered into the entire mesh backing when the bracket is being fitted. The excess is particularly helpful on teeth with abnormal morphology.
Excess will not be worn away by tooth brushing and other mechanical forces, it must be removed with a scaler before the adhesive has set or with burs after setting (oval or tapered tungsten carbide bur no. 7006, no. 2).
Removal of excess adhesives prevents gingival irritation and plaque build up around the periphery of the bonding base.
It also improves esthetics by providing a neater and cleaner appearance, and eliminating exposed adhesive that might become discoloured in the oral environment.
Bonding to Premolars
The visibility for direct bonding is facilitated if these teeth are bonded without a lip expander one at a time.
Bracket positions should be controlled using a mouth mirror.
For newly erupted mandibular premolars, gingivally offset brackets are recommended.
The gingival third of these teeth may have a high incidence of aprismatic enamel and an enamel rod direction that is less retentive of resin tags.
Bonding to Molars
The molar teeth are bonded separately from the other teeth to permit concentration on access, visibility and moisture control.
Dry field is obtained by a Dri-Angle in the buccal side and a cotton roll. The saliva is ejector is positioned on the side to be bonded, the mouth mirror is placed over the Dri-Angle for tissue retraction.
The bonding procedures are performed on one side, bonding the mandibular and maxillary molars in sequence. The same procedures are then repeated on the contralateral side.
Bonding to Crowns and Restorations
Many adult patients have crown and bridge restorations fabricated from porcelain and precious metals, in addition to amalgam restorations of molars. Banding becomes difficult, on the abutment teeth of fixed bridges.
The Micro Etcher (FDA approved intraoral sandblaster) uses 50 micro meter white or 90 micro meter tan aluminium oxide particles and approximately 7kg/cm2 pressure, has been advantageous for bonding to different artificial tooth surfaces.
This tool is also useful for;
q Rebonding loose brackets
q Increasing the retentive area inside molar bands
q Creating micro mechanical retention for bonded retainers and
q Bonding to deciduous teeth
Bonding to Porcelain
Following technique is recommended
1. Isolate the working field adequately.
2. Deglaze an area slightly larger than the bracket base by sandblasting with 50 micro meter aluminium oxide for three seconds.
3. Etch the porcelain with 9.6% hydrofluoric acid gel for two minutes.
4. Carefully remove the gel with cotton roll, then rinse using a high volume suction.
5. Immediately dry with air and bond bracket with highly filled Bis GMA resin. The use of silane is optional.
Bonding to Amalgam
Improved techniques for bonding to amalgam restorations may involve;
1. Modification of the metal surface (sandblasting, diamond bur roughening)
2. The use of intermediate resins that improve bond strength (All-Bond 2, Enhance, Metal Primer)
3. New adhesive resins that bond chemically to non-precious as well as precious metals (4-META resins)
The following procedure is recommended;
A. Small amalgam filling with surrounding sound enamel
1. Sandblast amalgam alloy with 50 micro meter aluminium oxide for 3 seconds.
2. Condition sound enamel with 37% H3PO4 for 15 to 30 seconds.
3. Apply sealant and bond with composite resin.
B. Large amalgam restoration or amalgam only
1. Sandblast amalgam alloy with 50 micrometer aluminium oxide for 3 seconds.
2. Apply a uniform coat of suitable metal primer and wait for 30 seconds (according to manufacturer’s instructions).
3. Apply sealant and bond with composite resin.
It is made sure that the bonded attachment is not in occlusion with antagonists.
Bonding to Gold
Different new technologies that bond chemically to precious metals include;
1. Sandblasting
2. Electrolytic tin-plating or plating with gallium-tin solution (Adlloy)
3. Intermediate primer
4. New adhesives that bond chemically to precious metals (Superbond C & B, Panavia Ex & 21)
Present clinical experiments include the use of new one component primer based on Triazine-Dithiol and 4-META adhesive resin.
Bonding to Composite Restoratives
The bond strength obtained with the addition of a new composite to mature composite is substantially less than the cohesive strength of the material.
Brackets bonded to a fresh, roughened surface of old composite restorations appear to be clinically successful in most instances.
It is advantageous to use an intermediate primer as well.
Lingual Bracket Bonding – Invisible Braces
When it became apparent into late 1970s that bonding of brackets was a viable procedure and that esthetic plastic and ceramic brackets were a compromise, placing the brackets on the lingual surfaces of the teeth appeared to be the ultimate esthetic approach.
The development was pioneered in Japan by Fujita who worked on the mushroom arch, and by several American Orthodontists (Kurz, Kelly, Paige, Creekmore).
The problems with lingual orthodontics are;
1. Pronunciation difficulties immediately after insertion.
2. Technique is difficult, time consuming, working position is awkward.
3. Considerable difficulties experienced by clinicians particularly in the finishing stages.
4. More precision is necessary for the adjustment of lingual arch wires, with reduced interbracket distance.
Steps involved in direct and indirect bracket bonding on facial or lingual surfaces are as follows;
1. Cleaning
2. Enamel conditioning
3. Sealing
4. Bonding
Direct Bonding
1. Cleaning
Thorough cleaning of the teeth with pumice is essential to remove plaque and the organic pellicle that normally covers all teeth. Cleaning is done using rotary instruments, either a rubber cup or polishing brush.
2. Enamel Conditioning
A. Moisture control
After the rinse, salivary control and maintenance of a completely dry working field is absolutely essential. Some of the measures used are;
q Lip expanders and / or cheek retractors
q Saliva ejectors
q Tongue guards with bite blocks
q Saliva duct obstructers
q Cotton or gauze rolls
q Antisialagogues (generally not needed, when indicated, banthine tablets 50mg per 100 lbs body weight 45 kgs.) in sugar free drink 15 minutes before bonding, may provide adequate results.
B. Enamel Pretreatment
After the operating field has been isolated, the teeth to be bonded are dried. The conditioning solution or gel, 37% H3PO4 is lightly applied over the enamel surface with a foam pellet, brush for 60 seconds.
At the end of etching period, the etchant is rinsed off with abundant water spray.
Teeth are thoroughly dried with a moisture and oil free source to obtain dull frosty appearance. Salivary contamination of the etched surface must not be allowed.
Study of etched enamel surface under Scanning Electron Microscope
Various studies have been carried out to define optimal concentrations of the acid used for etching and the duration of etching with H3PO4. These investigations include study of the etched enamel surface pattern under Scanning Electron Microscope highlighting the loss of enamel, test of shear bond strength of a bonded attachment to a correlated etchant concentration and duration of etching and the trauma to the enamel and the amount of adhesive on the surface of enamel subsequent to debonding.
Diedrich typed action of the etchant on the enamel in three stages
Honeycomb pattern of the etched enamel (initially periphery of the prism head is delineated by micro clefts [0.1 to 0.2 micro meter]) continued action of acid leads to loss of substance predominantly in the area of prism cores with simultaneous conservation of the marginal areas.
Least amount of enamel is lost in this etch pattern designated as Type I.
As action of acid proceeds, there is dissolution of crest like marginal ridges, while the marginal clefts continue to widen. This is the transitional zone of central and peripheral etching pattern, in which existing marginal ridges are elevated approximately to 3 micro meter designated as Type III.
Peripheral etching pattern is an advanced stage in which the fragile prism peripheries break off. Maximum enamel loss takes place in this stage designated as Type II.
The above mentioned patterns of the etched enamel surface were named as Type I, II and III by Silverstone et al.
Galil and Wright described Type IV and Type V etching patterns.
Type IV etch pattern is commonly seen in cervical areas. It shows pitted irregular pattern and displays no rod or prism pattern.
Type V shows no pattern of prism outline. Enamel surface is extremely flat and smooth and they lack micro irregularities for penetration of resin.
3. Sealing
After teeth are completely dried and appear frosty white, a thin layer of sealant is applied over the entire etched enamel surface with a small foam pellet or brush with a single gingivoincisal stroke.
The sealant coating should be thin and even because excess sealant may induce bracket drift and unnatural enamel topography when polymerized. Bracket placement should be started immediately after all etched surfaces are coated with sealant.
Research is going on to determine the exact function of the sealant in acid etch procedure.
1. Some investigators conclude that sealant is necessary to achieve proper bond strength.
2. Sealant permits a relaxation of moisture control.
3. It permits easier bracket removal.
4. It protects against enamel tearouts at debonding.
Ceen and Gwinnett found that light polymerized sealants protect enamel adjacent to brackets from dissolution and subsurface lesions, whereas, chemical curing sealants polymerized poorly, exhibit drift, and have low resistance to abrasion.
4. Bonding
At present, the majority of clinicians routinely bond brackets with the direct rather than the indirect technique.
The recommended bracket bonding procedure consists of the following steps;
1. Transfer
2. Positioning
3. Fitting
4. Removal of excess
1. Transfer
The Clinician grips the bracket with a pair of cotton pliers or a reverse action tweezer and then applies the mixed adhesive to the back of the bonding base. The bracket is immediately placed on the tooth close to its correct position.
2. Positioning
A placement scaler, such as the RM 349 or, preferably, one with parallel edges, is used to position the brackets mesiodistally and incisogingivally and angulate them correctly.
The placement scaler with parallel edges allows visualization of the bracket slot relative to the incisal edge and long axis of the teeth, with the scaler seated in the slot.
Proper vertical positioning may be enhanced by different measuring devices (Boon’s gauge) or height guides on the brackets themselves.
A mouth mirror will aid in horizontal positioning particularly on rotated premolars.
3. Fitting
Next, the scaler is turned, and with one – point contact with the bracket, it is pushed firmly toward the tooth surface. The tight fit will result in good bond strength, little material to remove on debonding, and reduced slide when excess material extrudes peripherally.
The scaler should be removed after the bracket is in correct position and no attempts should be made to hold the bracket in place with the instrument.
Totally undisturbed setting is essential for achieving adequate bond strengths.
4. Removal of Excess
A slight bit of excess adhesive is essential to minimise the possibility of voids and to be certain that it will be buttered into the entire mesh backing when the bracket is being fitted. The excess is particularly helpful on teeth with abnormal morphology.
Excess will not be worn away by tooth brushing and other mechanical forces, it must be removed with a scaler before the adhesive has set or with burs after setting (oval or tapered tungsten carbide bur no. 7006, no. 2).
Removal of excess adhesives prevents gingival irritation and plaque build up around the periphery of the bonding base.
It also improves esthetics by providing a neater and cleaner appearance, and eliminating exposed adhesive that might become discoloured in the oral environment.
Bonding to Premolars
The visibility for direct bonding is facilitated if these teeth are bonded without a lip expander one at a time.
Bracket positions should be controlled using a mouth mirror.
For newly erupted mandibular premolars, gingivally offset brackets are recommended.
The gingival third of these teeth may have a high incidence of aprismatic enamel and an enamel rod direction that is less retentive of resin tags.
Bonding to Molars
The molar teeth are bonded separately from the other teeth to permit concentration on access, visibility and moisture control.
Dry field is obtained by a Dri-Angle in the buccal side and a cotton roll. The saliva is ejector is positioned on the side to be bonded, the mouth mirror is placed over the Dri-Angle for tissue retraction.
The bonding procedures are performed on one side, bonding the mandibular and maxillary molars in sequence. The same procedures are then repeated on the contralateral side.
Bonding to Crowns and Restorations
Many adult patients have crown and bridge restorations fabricated from porcelain and precious metals, in addition to amalgam restorations of molars. Banding becomes difficult, on the abutment teeth of fixed bridges.
The Micro Etcher (FDA approved intraoral sandblaster) uses 50 micro meter white or 90 micro meter tan aluminium oxide particles and approximately 7kg/cm2 pressure, has been advantageous for bonding to different artificial tooth surfaces.
This tool is also useful for;
q Rebonding loose brackets
q Increasing the retentive area inside molar bands
q Creating micro mechanical retention for bonded retainers and
q Bonding to deciduous teeth
Bonding to Porcelain
Following technique is recommended
1. Isolate the working field adequately.
2. Deglaze an area slightly larger than the bracket base by sandblasting with 50 micro meter aluminium oxide for three seconds.
3. Etch the porcelain with 9.6% hydrofluoric acid gel for two minutes.
4. Carefully remove the gel with cotton roll, then rinse using a high volume suction.
5. Immediately dry with air and bond bracket with highly filled Bis GMA resin. The use of silane is optional.
Bonding to Amalgam
Improved techniques for bonding to amalgam restorations may involve;
1. Modification of the metal surface (sandblasting, diamond bur roughening)
2. The use of intermediate resins that improve bond strength (All-Bond 2, Enhance, Metal Primer)
3. New adhesive resins that bond chemically to non-precious as well as precious metals (4-META resins)
The following procedure is recommended;
A. Small amalgam filling with surrounding sound enamel
1. Sandblast amalgam alloy with 50 micro meter aluminium oxide for 3 seconds.
2. Condition sound enamel with 37% H3PO4 for 15 to 30 seconds.
3. Apply sealant and bond with composite resin.
B. Large amalgam restoration or amalgam only
1. Sandblast amalgam alloy with 50 micrometer aluminium oxide for 3 seconds.
2. Apply a uniform coat of suitable metal primer and wait for 30 seconds (according to manufacturer’s instructions).
3. Apply sealant and bond with composite resin.
It is made sure that the bonded attachment is not in occlusion with antagonists.
Bonding to Gold
Different new technologies that bond chemically to precious metals include;
1. Sandblasting
2. Electrolytic tin-plating or plating with gallium-tin solution (Adlloy)
3. Intermediate primer
4. New adhesives that bond chemically to precious metals (Superbond C & B, Panavia Ex & 21)
Present clinical experiments include the use of new one component primer based on Triazine-Dithiol and 4-META adhesive resin.
Bonding to Composite Restoratives
The bond strength obtained with the addition of a new composite to mature composite is substantially less than the cohesive strength of the material.
Brackets bonded to a fresh, roughened surface of old composite restorations appear to be clinically successful in most instances.
It is advantageous to use an intermediate primer as well.
Lingual Bracket Bonding – Invisible Braces
When it became apparent into late 1970s that bonding of brackets was a viable procedure and that esthetic plastic and ceramic brackets were a compromise, placing the brackets on the lingual surfaces of the teeth appeared to be the ultimate esthetic approach.
The development was pioneered in Japan by Fujita who worked on the mushroom arch, and by several American Orthodontists (Kurz, Kelly, Paige, Creekmore).
The problems with lingual orthodontics are;
1. Pronunciation difficulties immediately after insertion.
2. Technique is difficult, time consuming, working position is awkward.
3. Considerable difficulties experienced by clinicians particularly in the finishing stages.
4. More precision is necessary for the adjustment of lingual arch wires, with reduced interbracket distance.
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