DEBONDING
Objectives
1) To remove the attachment and all the adhesive resin from the tooth.
2) To restore the surface as closely as possible to its pre-treatment condition without inducing iatrogenic damage.
General aspects of debonding are;
§ Clinical procedure
§ Characteristics of normal enamel
§ Influence of different debonding instruments on surface enamel
§ Amount of enamel lost in debonding
§ Enamel tear out
§ Enamel cracks (fracture lines)
§ Adhesive remnant wear
§ Reversal of decalcifications
Clinical Procedure
The clinical debonding procedure may be divided in two stages;
1) Bracket removal
2) Removal of residual adhesive
Bracket removal – Steel brackets
An original method was to place the tips of a twin-beaked plier 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 lift the bracket off with a peel force. This is particularly useful on brittle, mobile or endodontically treated teeth.
The brackets are easily deformed and less suitable for recycling when this method is used.
Bracket Removal – Ceramic Brackets
Because of differences in bracket chemistry and bonding mechanisms, various ceramic brackets behave differently on debonding.
The preferred mechanical debonding is to lift the brackets off with peripheral force application.
Cutting the brackets off with gradual pressure from the tips of twin-beaked pliers oriented mesiodistally close to the bracket–adhesive interface is not recommended because it might introduce horizontal enamel cracks.
Electrothermal Debracketing
Sheridan (1986) found an alternative to conventional bracket removal by Electrothermal Debracketing (ETD). They developed this technique for removing bonded brackets from enamel surface with a device that generated heat which deformed the adhesive bracket interface enabling the bracket to be gently lifted from the enamel surface without distortion of the bracket / damage to enamel.
Removal of Residual Adhesive
Because of the color similarly between present adhesives and enamel, complete removal of all remaining adhesives are not easily achieved.
The removal of excess adhesive may be accomplished by;
1) Scraping with a very sharp band or bond-removing pliers or with a scaler
- Fast method
- Frequently successful on curved teeth (premolars, canines), it is less useful on flat anterior teeth
2) Using a dome-tapered TC bur (No. 1172, 1171) in a contra-angle handpiece at speed of 30,000 rpm.
- Light painting movements of the bur should be used so as not to scratch the enamel
- Water cooling should not be employed when the last remnants are removed because water lessens the contrast with enamel
Amount of enamel lost in Debonding
§ An initial prophylaxis with bristle brush for 10 to 15 seconds per tooth may abrade away as much as 10mm of enamel, whereas only about 5mm may be lost when a rubber cup is used.
§ Enamel loss for unfilled resins may be 2 to 40mm and for filled resins 30 - 60mm depending on the instruments used for prophylaxis.
§ Using computerized three-dimensional scanning over the tooth surface, Van Waes et al concluded that only 7.4mm enamel damage (minimal) is associated with careful use of a TC bur removal of residual composite.
Enamel Tearouts
Localised enamel tearouts have been reported to occur established with bonding and debonding both metal and ceramic brackets.
Small filler particles may penetrate into the etched enamel to a greater degree than macrofiller may penetrate. On debonding the small fillers reinforce the adhesive tags. The macrofillers create a more natural breakpoint in the enamel – adhesive interface. With unfilled resins there is no natural breakpoint.
Ceramic brackets using chemical retention appears to cause enamel damage more often than those using mechanical retention. This damage occurs because the location of the bond breakage is at the enamel – adhesive rather than at the adhesive – bracket interface.
Clinical Implications
1) To use brackets that have mechanical retention and debonding instruments and techniques that primarily leave majority of the composite on the tooth.
2) To avoid scraping away adhesive remnants with hand instruments.
Enamel Cracks
§ Cracks, occurring as split lines in the enamel are common.
§ Generally they do to show up on routine intra oral photographs, thus finger shadowing in good light, fibre optic trans-illumination is needed to detect a crack.
In a study by Zachrisson, Skogan and Hoymyhr, (using fibre optic light technique, examined more than 3000 teeth in 135 adolescents).
The most important findings were;
1) Vertical cracks are common (>50% teeth) but there is great individual variation.
2) Few horizontal and oblique cracks are observed normally.
3) No significant difference exists between the three groups (debonded, debanded and orthodontically untreated teeth) with regard to prevalence and location of cracks.
4) The most notable cracks are on the maxillary central incisors and canines.
The Clinical Implications are if an Orthodontist;
1) Observes several distinct enamel cracks on the patient’s teeth after debonding, particularly on teeth other than maxillary canines and central incisors.
2) Detects cracks in a predominantly horizontal direction, this is an indication that the bonding and / or debonding technique used may need improvement.
With ceramic brackets, the risk for creating enamel cracks is greater than for metal brackets. The lack of ductility may initiate stress build – up in the adhesive enamel interface that may produce enamel cracks at debonding.
3) Need for pre-treatment examination of cracks, notifying the patient and / or the parents if pronounced cracks are present.
Adhesive Remnant Wear
Adhesive wear depends on the size, type and amount of reinforcing fillers in the adhesive.
Gwinnett and Ceen reported that small remnants of unfilled sealant did not pre-dispose to plaque accumulation and did begin to wear away with time.
However, different types of filled adhesives have greater wear resistance and accumulate plaque more readily.
Brobakken and Zachrisson concluded that, it seems too optimistic to believe that residual filled adhesive will quickly disappear by itself after debonding, it appears irresponsible to leave large accumulation of adhesive.
Reversal of Decalcification
In a multibonded technique (with lack of any preventive fluoride program), Gorelick et al found that 50% of patients experienced an increase in white spots. The highest incidence was in the maxillary incisors, particularly the laterals.
Zachrisson BU (1975) recommended daily rinsing with dilute (0.05%) sodium fluoride solution throughout the periods of treatment and retention, plus regular use of a fluoride dentifrice.
In addition, painting a fluoride varnish / new effective anti caries agents such as titanium Tetrafluoride (TiF4) over caries – susceptible sites at each visit may be useful in patients with hygiene problems.
Artun and Thylstrup found that removal of cariogenic challenge after debonding results in arrest of further demineralization and a gradual regression of the lesion at the clinical level takes place primarily because of surface abrasion with some redeposition of minerals.
Ogaard et al observed that remineralization of surface softened enamel (such as under a loose band / bracket) and subsurface lesions are completely different processes. The surface – softened lesions remineralize faster and more completely than subsurface lesions, which remineralize extremely slowly, probably because of lesion arrest by widespread use of fluoride.
At present, it seems advisable to recommend a period of 2 to 3 months of good oral hygiene but without fluoride supplementation associated with the debonding session. More fluoride may tend to precipitate calcium phosphate onto the enamel surface and block the surface pores. This limits remineralization to the superficial part of the lesion and the optical appearance of the white spot is not reduced.
Objectives
1) To remove the attachment and all the adhesive resin from the tooth.
2) To restore the surface as closely as possible to its pre-treatment condition without inducing iatrogenic damage.
General aspects of debonding are;
§ Clinical procedure
§ Characteristics of normal enamel
§ Influence of different debonding instruments on surface enamel
§ Amount of enamel lost in debonding
§ Enamel tear out
§ Enamel cracks (fracture lines)
§ Adhesive remnant wear
§ Reversal of decalcifications
Clinical Procedure
The clinical debonding procedure may be divided in two stages;
1) Bracket removal
2) Removal of residual adhesive
Bracket removal – Steel brackets
An original method was to place the tips of a twin-beaked plier 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 lift the bracket off with a peel force. This is particularly useful on brittle, mobile or endodontically treated teeth.
The brackets are easily deformed and less suitable for recycling when this method is used.
Bracket Removal – Ceramic Brackets
Because of differences in bracket chemistry and bonding mechanisms, various ceramic brackets behave differently on debonding.
The preferred mechanical debonding is to lift the brackets off with peripheral force application.
Cutting the brackets off with gradual pressure from the tips of twin-beaked pliers oriented mesiodistally close to the bracket–adhesive interface is not recommended because it might introduce horizontal enamel cracks.
Electrothermal Debracketing
Sheridan (1986) found an alternative to conventional bracket removal by Electrothermal Debracketing (ETD). They developed this technique for removing bonded brackets from enamel surface with a device that generated heat which deformed the adhesive bracket interface enabling the bracket to be gently lifted from the enamel surface without distortion of the bracket / damage to enamel.
Removal of Residual Adhesive
Because of the color similarly between present adhesives and enamel, complete removal of all remaining adhesives are not easily achieved.
The removal of excess adhesive may be accomplished by;
1) Scraping with a very sharp band or bond-removing pliers or with a scaler
- Fast method
- Frequently successful on curved teeth (premolars, canines), it is less useful on flat anterior teeth
2) Using a dome-tapered TC bur (No. 1172, 1171) in a contra-angle handpiece at speed of 30,000 rpm.
- Light painting movements of the bur should be used so as not to scratch the enamel
- Water cooling should not be employed when the last remnants are removed because water lessens the contrast with enamel
Amount of enamel lost in Debonding
§ An initial prophylaxis with bristle brush for 10 to 15 seconds per tooth may abrade away as much as 10mm of enamel, whereas only about 5mm may be lost when a rubber cup is used.
§ Enamel loss for unfilled resins may be 2 to 40mm and for filled resins 30 - 60mm depending on the instruments used for prophylaxis.
§ Using computerized three-dimensional scanning over the tooth surface, Van Waes et al concluded that only 7.4mm enamel damage (minimal) is associated with careful use of a TC bur removal of residual composite.
Enamel Tearouts
Localised enamel tearouts have been reported to occur established with bonding and debonding both metal and ceramic brackets.
Small filler particles may penetrate into the etched enamel to a greater degree than macrofiller may penetrate. On debonding the small fillers reinforce the adhesive tags. The macrofillers create a more natural breakpoint in the enamel – adhesive interface. With unfilled resins there is no natural breakpoint.
Ceramic brackets using chemical retention appears to cause enamel damage more often than those using mechanical retention. This damage occurs because the location of the bond breakage is at the enamel – adhesive rather than at the adhesive – bracket interface.
Clinical Implications
1) To use brackets that have mechanical retention and debonding instruments and techniques that primarily leave majority of the composite on the tooth.
2) To avoid scraping away adhesive remnants with hand instruments.
Enamel Cracks
§ Cracks, occurring as split lines in the enamel are common.
§ Generally they do to show up on routine intra oral photographs, thus finger shadowing in good light, fibre optic trans-illumination is needed to detect a crack.
In a study by Zachrisson, Skogan and Hoymyhr, (using fibre optic light technique, examined more than 3000 teeth in 135 adolescents).
The most important findings were;
1) Vertical cracks are common (>50% teeth) but there is great individual variation.
2) Few horizontal and oblique cracks are observed normally.
3) No significant difference exists between the three groups (debonded, debanded and orthodontically untreated teeth) with regard to prevalence and location of cracks.
4) The most notable cracks are on the maxillary central incisors and canines.
The Clinical Implications are if an Orthodontist;
1) Observes several distinct enamel cracks on the patient’s teeth after debonding, particularly on teeth other than maxillary canines and central incisors.
2) Detects cracks in a predominantly horizontal direction, this is an indication that the bonding and / or debonding technique used may need improvement.
With ceramic brackets, the risk for creating enamel cracks is greater than for metal brackets. The lack of ductility may initiate stress build – up in the adhesive enamel interface that may produce enamel cracks at debonding.
3) Need for pre-treatment examination of cracks, notifying the patient and / or the parents if pronounced cracks are present.
Adhesive Remnant Wear
Adhesive wear depends on the size, type and amount of reinforcing fillers in the adhesive.
Gwinnett and Ceen reported that small remnants of unfilled sealant did not pre-dispose to plaque accumulation and did begin to wear away with time.
However, different types of filled adhesives have greater wear resistance and accumulate plaque more readily.
Brobakken and Zachrisson concluded that, it seems too optimistic to believe that residual filled adhesive will quickly disappear by itself after debonding, it appears irresponsible to leave large accumulation of adhesive.
Reversal of Decalcification
In a multibonded technique (with lack of any preventive fluoride program), Gorelick et al found that 50% of patients experienced an increase in white spots. The highest incidence was in the maxillary incisors, particularly the laterals.
Zachrisson BU (1975) recommended daily rinsing with dilute (0.05%) sodium fluoride solution throughout the periods of treatment and retention, plus regular use of a fluoride dentifrice.
In addition, painting a fluoride varnish / new effective anti caries agents such as titanium Tetrafluoride (TiF4) over caries – susceptible sites at each visit may be useful in patients with hygiene problems.
Artun and Thylstrup found that removal of cariogenic challenge after debonding results in arrest of further demineralization and a gradual regression of the lesion at the clinical level takes place primarily because of surface abrasion with some redeposition of minerals.
Ogaard et al observed that remineralization of surface softened enamel (such as under a loose band / bracket) and subsurface lesions are completely different processes. The surface – softened lesions remineralize faster and more completely than subsurface lesions, which remineralize extremely slowly, probably because of lesion arrest by widespread use of fluoride.
At present, it seems advisable to recommend a period of 2 to 3 months of good oral hygiene but without fluoride supplementation associated with the debonding session. More fluoride may tend to precipitate calcium phosphate onto the enamel surface and block the surface pores. This limits remineralization to the superficial part of the lesion and the optical appearance of the white spot is not reduced.
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