Debonding

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.

Indirect Bonding

Indirect Bonding

Several techniques for indirect bonding are available. Most are based on the procedures described by Silverman and Cohen.

In these techniques brackets are attached to the teeth on the patient’s models, transfer to the mouth with some sort of tray into which brackets become incorporated, and then bonded simultaneously.

Advantages

1. More accurate positioning of brackets.
2. Reduction in clinical chair time.

Disadvantages

1. Removal of excess adhesive is more difficult and time consuming.
2. Risk for adhesive deficiencies under the brackets is greater.
3. Failure rates are slightly higher.

Several indirect bonding techniques have proved reliable in clinical practice. They differ in the way –

A. Brackets are attached temporarily to model

1. Caramel Candy
2. Laboratory adhesive
3. Bonding resin
4. Sticky wax

B. Type of transfer tray

1. Silicon
2. Vacuum formed
3. Acrylic with transfer arm

The two most popular techniques are the Silicon impression material and the double sealant.

Indirect Bonding with Silicon Transfer Trays

1. An impression is taken and a stone model is poured. The model must be dried. It may be marked for long axis and incisal or occlusal height on each tooth.

2. Brackets are selected for each tooth.

3. A small portion of water – soluble adhesive is applied on each base or tooth.

4. The brackets are positioned on a model and checked for all measurements and alignments.

5. For silicon tray fabrication, the material is mixed and the putty is pressed onto the cemented brackets. The tray is formed allowing sufficient thickness for strength.

6. After the silicon putty has set, the model and the tray is immersed in hot water to release the brackets from the stone. Any remaining adhesive is removed under running water.

7. The silicon tray is trimmed and the midline is marked.
8. The patient’s teeth are prepared as for a direct application.

9. The adhesive is mixed, loaded in a syringe and a sufficient portion is applied to the bonding bases.

10. The tray is seated on the prepared arch and held with firm and steady pressure for three minutes.

11. The tray is removed after ten minutes. The tray may be cut longitudinally or transversely to reduce the risk of bracket debonding when it is peeled off.

12. The bonding is completed by careful removal of excessive flash. Oval or tapered TC bur is used to clean the area properly around each bracket. The area around the bracket pad is inspected for adhesive voids and filled in with a small mix of adhesive if needed.

Disadvantages

1. Brackets are not visible under the tray.
2. Light cured resins cannot be used.

Indirect Bonding with a double-sealant technique

In this technique of bonding, adhesive pastes, rather than a temporary adhesive, are used to attach the brackets to the patient’s stone model.

1. Small portions of catalyst and universal adhesive pastes are dispensed side by side on a mixing pad.
2. On a per tooth basis, enough adhesive for one attachment is mixed and applied to the back of the bonding base.
3. The bracket is placed on the model, and the excess adhesive is removed from the periphery of the base. This step is repeated until all brackets are bonded to the stone model.
4. After at least 10 minutes, a placement tray is vacuum-formed for each arch.
5. Models with trays attached are placed in water until thoroughly saturated.
6. The trays are then separated and trimmed so that gingival edge of each tray is within 2mm of the brackets.
7. Midline is marked with indelible ink.
8. The embedded bonding bases are lightly abraded with a mounted stone point, after which the placement tray is ready for clinical use.
9. The clinical procedure is begun with the customary prophylaxis, isolation and etching of the patient’s teeth.
10. The lingual sides of the bonding bases are painted with catalyst sealant resin (Part B).
11. The dry-etched teeth are painted with the universal sealant resin (Part B).
12. The tray is then inserted into the patient’s mouth, seated and held in place for at least 3 minutes. It is removed by peeling from the lingual towards the buccal.
13. Excess flash of sealant is carefully removed from the gingival and contact areas of the teeth.

Advantage of this technique

Clean up is simple because little flash is present and consists of unfilled sealant only.





Newer Techniques

1. Use of Surebonder dual temperature hot glue – Larry White (1999) introduced a new matrix or tray material which is more rigid and still has enough elasticity and flexibility to permit easy removal after polymerization.

Previous trays used failed to get all the brackets to adhere to the teeth. Usually 2-3 brackets would come out with the matrix when it was removed.

Larry White used Surebonder dual temperature hot glue gun. The gun is simply a heating element that liquifies the solid glue stick and then places glue where it is needed. The gun has a dual temperature control. The low temperature is suitable for indirect bonding.

Procedure

1. After marking the teeth on the cast, two thin coats of separating liquid are applied to all tooth surfaces.
2. The brackets are sprayed with silicon spray to lubricate their surfaces and make it easier to remove the matrix.
3. The glue gun is used to form a molten matrix over the entire lingual and occlusal surfaces. The brackets are covered only partially with care taken not to get hot glue in the bracket slot.
4. Before the glue sets, the technician should pat the molten glue into a close conformation.
5. After the glue cools and hardens, the matrix and the brackets are submerged in water for about 30 minutes to dissolved the tacky glue and separate bracket and matrix from the cast.
J.C. ENDIRECT technique by Jay Collins (2000)

In this technique a new ultra viscous water soluble and tenacious bonding adhesive J.C. ENDIRECT is used.

Procedure

1. The casts are trimmed and the labial and the buccal surfaces to be bracketed are marked with a fluorescent yellow marking pen. This eliminates the need for separating media, while providing visual aid to improve accuracy of bracket placement.

2. The horizontal and vertical lines are marked.

3. 5cm bead of J.C. ENDIRECT adhesive is placed on mixing pad and each bracket base is placed against it until most of the bracket base is covered with adhesive. The bracket is then placed on the working cast.

4. A soft plastic mouth guard is vacuum formed.

5. The transfer tray is then trimmed into sections and returned to the cast.

6. A rigid clear plastic sheet is then vacuum formed over bracketed soft transfer tray. Therefore a dual tray system is formed.

A precise bracket location is reproduced and J.C. ENDIRECT has necessary viscosity to prevent bracket drift.



New products for Light Cured Indirect Bonding – Larry White (2001)

1. Quick Cure – A composite adhesive with a photoinitiator catalyst that is highly sensitive to a broader range of blue light.

2. Power Slot – It is the tip of a light curing unit that concentrates the beam of visible light and thus reduces polymerization time.

When Quick Cure and Power Slot are used, the composite will set with only 3 seconds of curing per tooth.

3. Prompt-L-Pop – It is all in one self etching adhesive supplied in a disposable single application unit. The etchant and sealant are combined and no rinsing is required after application.

Bonding Procedure

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.

bonding in orthodontics - part II

The adhesives introduced in the early 1970s were primarily those of the powder-liquid type of methyl methacrylate that did not incorporate a filler. During this period, all the adhesives introduced had to adhere to plastic brackets that were made of polycarbonate. As time passed, however, the weakness of plastic brackets became apparent and metal brackets began to be used.

From the mid 1970s, the paste type of adhesives emerged in which both the base material and the catalyst were dispensed as pastes to be mixed before being used for bonding. The reason for this change was mainly due to the change in the type of brackets used in bonding.

Most of the resins used in orthodontics presently are modifications of the Bowen’s resin. The modifications are mainly in the physical properties such as viscosity of the materials to achieve optimal penetration of the resin into the etched enamel spaces which enhanced the bond strength and increased the dimensional stability by cross-linking.

The future of bonding is promising. Product development in terms of adhesives, brackets, and technical details is continually occurring at a rapid rate. Also new avenues for bonding in orthodontics are opening up;
q Lingual bonding
q Various types of bonded retainers and splints
q Semi-permanent single-tooth replacements
q Resin build-ups addressing tooth shape & size problems and
q Bonded space maintainers.

Bracket Bonding

Optimal performance in bonding of orthodontic attachments offers many ADVANTAGES when compared with conventional banding.

1. It is esthetically superior
2. It is faster and simpler
3. It results in less discomfort for the patient (no band seating and separation)
4. Arch length is not increased by band material
5. It allows more precise bracket placement (aberrant tooth shape does not result in difficult banding and poor attachment position)
6. Bonds are more hygienic than bands, therefore an improved gingival and periodontal condition is possible and better access for cleaning is available
7. Partially erupted teeth can be controlled
8. Mesiodistal enamel reduction is possible during treatment
9. Attachments may be bonded to artificial tooth surfaces (e.g. amalgam, porcelain and gold) and to fixed bridge work
10. Interproximal areas are accessible for composite build ups
11. Caries risk under loose bands is eliminated. Interproximal caries can be detected and treated.
12. No band spaces are present to close at the end of treatment.
13. No large inventory of bands is needed.
14. Brackets may be recycled, further reducing the cost.
15. Lingual brackets, invisible braces, can be used when the patient rejects visible orthodontic appliances.

DISADVANTAGES of bonding are;

1. A bonded bracket has a weaker attachment than a cemented band. Therefore it is more likely that a bracket will come off rather than that a band will become loosened.
2. Some bonding adhesives are not sufficiently strong.
3. Better access for cleaning does not guarantee better oral hygiene and improved gingival condition, especially if excess adhesive extends beyond the bracket base.
4. The protection against interproximal caries provided by well-contoured cemented bands is absent.
5. Bonding is more complicated when lingual auxiliaries are required or if headgears are attached.
6. Rebonding a loose bracket requires more preparation than recementing a loose band.
7. Debonding is more time consuming than debanding because removal of adhesive is more difficult than removal of cement.

Classification of Bonding Materials

A. Based on the basic bonding type
1. Acrylic based system
2. Diacrylate system
3. Glass ionomer system
B. Based on the curing system
1. Self curing system
2. Light curing system
3. Dual curing system
4. Laser curing system

C. Based on fluoride content
1. Fluoride releasing system
2. Non-fluoride releasing system

D. Based on filler content
1. Low or unfilled bonding system
2. Highly filled bonding system

Types of Adhesives

There are 2 basic types of dental resins currently in use for orthodontic bracket bonding. Both are polymers and are classified as;

A) Acrylic resins and B) Diacrylate resins

A. ACRYLIC RESINS – are based on self curing acrylics and consists of methyl methacrylate monomer and ultrafine powder. They formed linear polymers only. E.g. Orthomite, Directon, Genie.

B. DIACRYLATE RESINS – are based on acrylic modified epoxy resin (Bis GMA or Bowen’s resin). They polymerize by cross-linking into a three dimensional network. This contributes to greater strength, lower water absorption and less polymerization shrinkage.

q Both types of adhesives exist in either filled or unfilled forms.

q Investigations indicate that filled diacrylate resins of the Bis GMA type have the best physical properties and are strongest adhesives for metal brackets.

q Acrylic or combination resins have been most successful with plastic brackets.

q Some composite resins (Concise, Solo-Tach, Nuva-Tach) contain large coarse quartz or silica glass particles of highly variable size (3 to 20 micrometer) impart abrasion resistance properties.

q Others (Endur, Dynabond) contain minute filler particles of uniform size (0.2 to 0.3 micrometer) which yield a smoother surface that retains less plaque, but more prone to abrasion.

q Failure rates are significantly less with adhesives containing large filler particles and are recommended for extra bond strength but careful removal of excess is mandatory since such adhesives accumulate more plaque than others.

There are several alternatives to chemically autopolymerizing paste – paste systems.

1. No-mix adhesives – (Rely-A-Bond, System 1+) - These materials set when one paste under light pressure is brought together with a primer fluid on the etched enamel and bracket backing, or another paste on the tooth to be bonded.
Thus one adhesive component is applied to bracket base while another is applied to the dried etched tooth. As soon as it is precisely positioned, the bracket is pressed firmly into place and curing occurs usually within 30 to 60 seconds.

Little long term information is available on their bond strengths compared with those of the conventionally mixed paste – paste systems.

Furthermore, little is known about how much unpolymerized rest monomer remains in the cured adhesives, and its eventual toxicity. Invitro tests have shown that the liquid activators of the no-mix systems are definitely toxic, allergic reactions have been reported in patients, dental assistance and doctors when such adhesives are used.

2. Visible – Light polymerized adhesives (Transbond) - These materials are cured by transmitting light through tooth structure and ceramic brackets. Argon laser may also be used for polymerization. Light cured resins used with metal brackets are usually dual cure resins, incorporating light initiators as well as chemical catalysts. Maximum curing depth of light activated resins depends on the composition of the composite, the light source and the exposure time.

Light cured composites are useful in situations in which quick set is required, such as when placing an attachment on a palatally impacted maxillary canine after surgical uncovering, with the risk for bleeding.

But they are also advantageous when extra long working time is desirable. This may be the case when difficult premolar bracket positions need to be checked and rechecked with a mouth mirror, before the bracket placement is considered optimal.

Metallic and ceramic brackets pre-coated with light cure composite and stored in suitable containers have consistent quality of adhesive, reduced flash, reduced waste and improved cross-infection control, and appear to have adequate bond strength.

3. Glass Ionomer Cements - GIC were introduced in 1972 primarily as luting agents and direct restorative material with unique properties for bonding chemically to enamel and dentin, as well as to stainless steel, being able to release fluoride ions for caries protection.

Such cements are now used routinely for cementing bands, because they are stronger than zinc phosphate and polycarboxylate cements, with less demineralization at the end of treatment.

Larry White in 1986 described a method of bonding orthodontic brackets with GIC. The earlier chemically cured GIC typically took 24 hours to reach optimal bond strengths. Therefore arch wires use had to be deterred or else very light force generating arch wires could only be placed.

Silverman et al (1995) introduced a light curing GIC for orthodontic bonding (Fuji Ortho LC). They have recommended a no-etch technique for bonding and claims it to bond satisfactorily in the presence of moisture. They reported failure rate of approximately 3% comparable to that of bonding resins which indicates it is clinically satisfactory.

infecton control in orthodontic office

Sterilization is one of the most important basic aspects in the whole of medical practice. Adequate attention has not been given to the prevention of cross contamination in the dental offices. This has occurred because we think that orthodontic procedures are usually non tissue invasive and also since the disease most identified with dentistry like hepatitis-B, was thought to be transmitted only by contact with blood of an infected carrier.

Individuals who are at the greatest occupational risk from cross infection in dental practice are the health professionals themselves. Recent studies indicate that orthodontists have the second highest incidence among dental professionals of acquiring hepatitis-B. Most orthodontic practices today are seeing patients from a much broader age group and socio-economic status. These people have a high risk of infectivity especially hepatitis-B.
Individuals undergoing treatment in dental office, like undetected hepatitis- B carriers and patients secreting herpes simplex viruses in saliva are asymptomatic and have the potential for transmitting the diseases. Diseases such as hepatitis-B and tuberculosis have long incubation period and so it is difficult to trace the source.

It would be very easy for an orthodontist to become involved in litigation, if a group of people were to develop a particular disease such as hepatitis with their only common source, the orthodontic office. The main concern facing the dentist is cross-infection, specifically, by the hepatitis virus. Hepatitis-B causes more death and practice disruption in dentistry than any other pathogen.

Hepatitis-B used to be called serum hepatitis and was thought to be transmitted only by parental routes. However, recent studies indicate that hepatitis-B can also spread through saliva and any instrument which comes into contact with blood or saliva of an infected or a carrier person. This virus can be transmitted from patient to dentist or patient to patient.
The greatest danger for orthodontist and his staff is from puncturing of the skin with contaminated instruments, sharp edges of orthodontic appliance, as any cuts or abrasions will allow micro-organisms to enter into the body. The microorganisms can also spread by direct contact with a lesion, by indirect contact through contaminated instruments or office equipments, by inhalation of aerosols induced by hand pieces and ultrasonic cleaners, and while scrubbing of instruments.

DEFINITION OF TERMS

Infection

This is an invasion and multiplication of micro-organisms in body tissues which may be clinically unapparent or results in local cellular injury due to competitive metabolism, toxins, intracellular replication or antigen antibody reactions response.

Cross Infection

This is the passage of micro-organisms from one person to another. The potential for cross infection in the dental office exists for direct or indirect transmission, as well as via aerosols routinely created during clinical procedures.

Disinfection

This refers only to the inhibition or destruction of pathogens. This is an adequate treatment for cleaning working surfaces of a dental unit. Disinfectant is a chemical agent that kills pathogenic and non-pathogenic micro-organisms but not spores. Recent studies say that there is no difference between pathogenic and nonpathogenic organisms. All micro-organisms can be pathogenic under certain circumstances.

Sterilization

It is the destruction or removal of all forms of life, with particular reference o micro-organisms; in other words destruction of bacteria, viruses, spores and fungi. The criterion of sterility is the absence of microbial growth in suitable media. The instrument used for sterilization is called sterilizer and the agents capable of this are called as sterilizing agents.

WHAT IS INFECTION CONTROL?

This is the governing or the limiting of the spread of infections via different channels, in a specific or general environment.

The procedures in the orthodontic office are of two major categories.

1. Those which interfere with the spread of infectious agents by reducing contamination.
2. Those which remove or kill the disease agents after contamination has occurred.

Need for Infection control

Orthodontic professionals are exposed to a wide variety of micro-organisms in the blood and saliva of the patients. These micro-organisms may cause infections such as Common cold (influenza), Pneumonia, T. B., Herpes, Hepatitis, A I D S etc. The use of effective infection control procedures in the orthodontic office prevent cross contamination that may extend to the dentist, other staff and patients.

Primary Goals of Infection control

 To lower the risk of cross contamination by reducing the levels of pathogens.
 To correct any break in aseptic technique.
 To use universal precautions with every patient (treat every patient and instrument as potentially infectious).
 To protect patients and personnel from occupational infections.

INFECTION CONTROL IN ORTHODONTICS

Diseases transmitted in an orthodontic office

a) Hepatitis-A: - Commonly known as infectious or contact hepatitis. It is often transmitted through the food chain. If it is treated properly, one would not become carrier.

b) Hepatitis-B: - This virus can survive for a week on hand pieces, equipments or uniforms.

c) Hepatitis non-A non-B: - The most common form of hepatitis, it usually results from blood transfusions.

d) Delta hepatitis: - It kills 12 to 22% of those infected. It is transmitted primarily through intravenous drug use.

e) Tuberculosis

f) Herpes Simplex: - Herpes I virus is the most easily transmitted; Herpes II, the venereal herpes, can’t be transmitted through saliva.

g) A I D S: - This deadly virus can be transmitted only through blood.

h) C M V (Cytomegalo Virus): - (Day care disease) A herpes like virus, spreads through improper sanitation.

Areas of infection control

1. Orthodontist and staff.

Basically, good personnel hygiene is the keystone of protection. The most important aspect of this is careful hand washing. They should be washed at least for a minute in cold water with germicidal soap. Cold water is suggested because hot water may cause pores to open. Then the use of a hand disinfectant is administered. Of course, after all preparations, proper gloves should be used. As far as the Orthodontist is concerned a reasonably complete medical history of his patient is important in determining who are
more likely to carry pathogenic organisms.

2. Instruments

The Orthodontist must decide for himself, which instruments need to be sterilized. Instruments can be of three categories.

a) Critical: - Instruments that penetrate the mucosa must be sterilized. E.g. Bands, band removers, ligature directors, band forming pliers etc.

b) Semi Critical: - Instruments that touches the mucosa should be sterilized. E.g. Mirror, retractors etc.

c) Least Critical: - Instruments such as Ligature tier and distal-end cutter, tying pliers, arch forming pliers, torquing keys, boons gauge etc. should be disinfected.

3. Operator site.

We should have in mind that our chair, table, light handles, spittoon, three way syringes etc., all become contaminated. It should be wiped frequently with 70% isopropyl alcohol. It is advisable to have straight tubing for your hand piece, three-way syringe etc. and to have hand pieces fitted with nonretraction valve. Minimize the no. of tubing and wires which can accumulate dust.

Primary Infection Control Measures

Patient Screening

A regular informative medical history of the patient can help to identify factors that assist in the diagnosis of oral and systemic disorders. Many patients often fail to give the information. Every patient should be treated as potentially infectious. This important fundamental application of infection control is termed as UNIVERSAL PRECAUTIONS. The blood and body fluid precautions substantially reduce the clinical guess work of a patient’s infection status.

Personal Protection

Repeated exposure to saliva and blood during the dental treatment procedures may challenge the dentist’s immune defense with a wide range of microbial agents. In this context, immunological protection and barrier protection are required

Immunological Protection

For immunological protection the operator should go for available vaccines of proven efficacy to prevent the onset of clinical or sub-clinical infection. The occupational risk of contacting hepatitis B, measles, rubella, influenza and certain other microbial infections can be minimized by stimulating artificial active immunity. The Orthodontists, their family members & the staff should undergo vaccination.

a) Hepatitis: - It needs a booster.
b) Rubella Vaccination:- It is against measles & does not need a booster.
c) Tetanus Immunization: - It needs a booster dose every ten years.

Barrier Control

Barrier protection is against the range of potential pathogens encountered during patient treatment. The physical barriers like disposable gloves, face masks, protective eyewear during treatment procedure will minimize the infectious exposure.

1. Use of disposable gloves, masks, protective clothing, protective eye wear, surface coverings and disposable materials.
2. Gowns must be cleaned daily.
3. Avoid rings bracelets, watches etc.
4. Should scrub the hands and use disinfectant before use of glove.
5. Gloves should be changed after every patient.
6. Use protective coverings, cover for dental light, handle, tray, covers and tubing for hand pieces, aspirator and air water syringe.
7. Let the patient rinse with antimicrobial mouth wash before treatment.
8. Except for few backup instruments, all instruments and pliers should be kept on sterilized trays / sterilizer.
9. Avoid handling the chart, telephone, pen, pencil etc., in between patients.
10.Use sensor lights instead of switches wherever possible.
11.Use sensor controlled water filter / foot operated water tap.
12.Disposable items should be burned immediately.
13.Impression should be disinfected immediately in the lab.
14.Protective eye-wear should be used in the lab.
15.Should not allow the splash from the lathe or other waste materials to be on the floor or table.
16.Avoid reusing the mixed pumice powder. Gloves Cuts and abrasions often found in fingers will serve as roots of microbial entry into the system when ungloved hands are placed in patient’s oral cavity – WET FINGERED DENTISTRY. Hand washing is not a substitute for use of gloves. Improper fitting gloves and reuse of gloves are not recommended. Washing of gloves with antiseptics increases the size and number of pinholes.

Protective eye wear

Eyes are more susceptible to physical and microbial injury because of their limited vascularity and diminished immune capacities. Droplets containing microbial contaminants can lead to conjunctivitis. Operator should have a protective eye wear during working. If protection eye wear is available for patients, it is advisable because hand pieces, sharp instruments, arch wires etc. are routinely passed over the patients face. Removing a patient’s glasses during dental treatment for the sake of comfort can no longer be recommended.

Masks

Face masks can protect the operator from microbe-laden aerosolized droplets. The best mask can filter 95% of droplets of 3.0 to 3.2 microns in diameter. Mask should fit around the entire periphery of the face. It is better to change the mask between each patient.

Washing and care of hands

Everything that is used inside the patient’s mouth in a clinic should besterile. Short nails will avoid tears in gloves and decrease the chance of patient discomfort and reduce the number of bacteria that can get trapped below it. Jewelry also should be avoided. Hand washing procedure should begin with scrubbing of all surfaces of nails, fingers, hands and lower arms with an antimicrobial preparation or detergent, followed by 2-3 minutes rinse with cold water and then application of a disinfectant. Hands should be dried with hot air or disposable paper towels, and should be followed by the use of disposable gloves. Use of gloves is not a substitute for routine hand washing.

Avoidance

Reduce the number of items that become contaminated. Reduce reusable items as much as possible. Most of the dental instruments are now available in disposable form.

Proper clinical attire

Appropriate dental clinic attire is a misunderstood area. Many practitioners place too much emphasis on choice of attire and not enough emphasis on correct protocol.

Current recommendations state that clinical attire should be changed at least once a day or when it becomes visibly soiled. Studies have shown that clinical attire easily becomes contaminated whenever a rotary instrument is used in the mouth. For this reason, a disposable cover must be worn over the gown when using rotary instruments. Either a cotton weave or preferably a polyester-cotton blend is acceptable.

Although OSHA (Occupational Safety and Health Administration) statement indicates that all exposed skin surfaces should be covered, short sleeved uniform may be acceptable. Intact skin is an adequate barrier against blood borne pathogens. Gowns should be with less buckles and buttons.

OSHA emphasizes that Street clothes and shoes must not be worn during patient treatment. Personnel must not wear clinic attire to and from the work place. Aprons / lab coats are to be used wisely. It is mandatory to use the aprons while examining patients or while working in the laboratory. These procedures will inevitably sow microorganisms into the fabric of the apron. Wearing the same garment to public places can result in distribution of the microorganisms to the areas visited and vice-versa. Wearing an apron does not necessarily badge you as doctor. Misusing clinical attire is as bad as not
following it.

Isolation

In a polyclinic or a multichaired clinic it is better to have isolation between the chairs. Ultrasonic cleaner, three way syringe etc. will cause transmission of organisms through aerosols.

Other barriers

Use of mouth wash

The use of an appropriate mouth wash prior to treatment procedure will reduce the total number of microbes in the oral cavity. Such a mouth rinse can reduce the number of oral microbes over a period while dental procedures are being performed.

Sharps disposal system

A sharps container is a mandatory part of the overall waste disposal system with in the dental office. Sharps container must be rigid, puncture proof, leak resistant and should be sterilizable.

Disinfection

Please note that disinfection procedures are advised only for those operatory surfaces and materials that cannot be routinely sterilized, such as, the table, dental chair and working surfaces, and for certain orthodontic instruments.

Surface disinfection

The operatory surfaces may become contaminated with saliva, blood or exudates. Disinfection of environmental surface is a two step procedure. An initial mechanical removal of tenacious organic debris is required. This is followed by application of an appropriate disinfectant. Separate surface cleaners and surface disinfectants may be employed. Surface disinfection can be done by scrubbing the surface with the iodophor-soaked gauze pads and allowed to dry. Then 70% isopropyl alcohol should be used to remove the residue. Vita wipes can be used instead of iodophors to avoid staining.

Use of Quaternary Ammonium Compounds and chemical agents are not advisable for orthodontic instrument. 8% solution of formaldehyde in alcohol and 2% aqueous solution of activated gluteraldehyde are acceptable.

Impressions / casts

The following four methods are acceptable for the disinfection of impressions:

Immersion in a chemical disinfectant such as 0.5 % - 1% sodium hypochlorite containing 1% chlorine, 2% gluteraldehyde for 60 minutes, 4% formaldehyde for 10 minutes. Even though gluteraldehyde is not effective against HIV and HBV, it is generally accepted.

Spraying of a disinfectant on the impression – 0.5% chlorhexidine in 70% alchohol
Usage of an ultraviolet disinfection unit.

Usage of an antiseptic containing alginate impression material.

Dental casts may be disinfected by adding discinfectant like iodophor or neutral gluteraldehyde to dry gypsum during the mixing process.

Instruments

Soaking in 2% gluteraldehyde for 100 minutes at room temperature is acceptable for disinfection of those orthodontic instruments which have been categorized as Least Critical instruments. These instruments should be scrubbed in soap water and then rinsed gently before use of the disinfectant.

Sterilization

Types of sterilization

Steam autoclave sterilization: - This process is very robust having excellent penetrating power. Unfortunately, it will corrode carbon steel items like burs, cutting instruments, orthodontic instruments etc. It will produce wet pouches at the end of the sterilization process. After steam sterilization the wet pouches should not be removed from the sterilizer until they are dry. Wet pouches will easily tear when handled. Some steam sterilizers have a post sterilization dry cycle and that should be used.

Dry heat sterilization: - It has a cycle time that is longer than most steam sterilizers but there is no corrosion of carbon steel instruments as long as the instruments are dry when loaded. Dry heat sterilizer yields completely dry packages.

Unsaturated chemical vapor sterilization : - This has a cycle time similar to the steam autoclave, and there is no corrosion of carbon steel instruments as long as the instruments are dry when loaded and are dry at the end of sterilization.

Liquid chemical sterilization: - This can be used only for items that cannot be heat sterilized. To achieve sterilization rather than incomplete microbial kill, these liquid chemical sterilants must be used for the proper contact time ranging from 3 – 12 hrs. depending on the sterilants being used. Instruments The instruments that are indicated for sterilization should be washed in soap water and then rinsed in running water to remove all debris, blood stains etc. Then it should be kept in ultrasonic cleaner. After ultrasonic cleaning, dry the instruments thoroughly (either by hand drying or by applying alcohol) and use water soluble oil to lubricate the hinged instruments to prevent corrosion. The sterilization method used can be selected according to our choice.
It is advisable to have a sterilizer, which has a steam sterilizing facility, a self drying and a storing facility. Dipping of instruments and bands in a solution of 1% sodium nitrate in deionised water and shaking them to remove excess solution will help in resisting rust formation.

Orthodontic Bands Heat sterilization of orthodontic bands destroys the ink that indicates band size. By using a plastic box with holes and dipping in gluteraldehyde solution, bands can be sterilized Ready cassettes are also available in the market for sterilization of
instruments and bands.

Packaging of instruments

Packaging the instruments before placing them into the sterilizer keeps the instruments in functional sets and protects them from re-contamination when they are removed from the sterilizer and during storage. Unwrapped instruments and unwrapped instrument cassettes have a zero-sterile shelf life after removal from the sterilizer.

Monitoring sterilization

Monitoring the effectiveness of the sterilization process in a particular time interval is very important. Spores of Bacillus stearothermophilus are used to monitor steam and unsaturated chemical vapor sterilizers, and spores of Bacillus subtilis are used to monitor dry heat sterilizers. In spore testing the biological indicators (spore strips or vials) are kept inside a regular instrument package. Spore testing can measure the use and functioning efficiency of sterilizers.

The other way is chemical monitoring which uses a special ink that changes color or form when exposed to sterilizing temperatures. These are in the form of autoclave tape, strips or tabs or special marking on the outside of the pouches.

Storage of sterilized instruments

Unpackaged instruments removed from the sterilizer have a zero –sterile shelf life. Do not allow packages to become compressed. Store the packages in a low dust area. The sterile shelf life is dependent upon the integrity of the packaging material. This is determined by assuring that the package never becomes wet, by observing the packaging for tears upon removed from storage, and when delivered to chair side for use on the next patient.

Hardness and Corrosion of instruments during sterilization.

Hardness

The stainless steel used in the manufacture of orthodontic pliers is formed at 18000 – 20000 F and tempered at 8000 - 9000 F. So these pliers cannot be damaged at temperature less than 8000 F. Carbide inserts in pliers can be damaged only at temperatures above 15000 F.

Studies shows cutters gain an increase in hardness after 500 cycles of sterilization. Dry heat produced the least and autoclave the most. Surface discoloration was visible on every plier after 500 cycles. The worst discoloration was seen in the chemiclaved instruments.

Corrosion

It is an electrolytic process in which the contact of two dissimilar metals or dissimilar areas within a single metal sets up a potential difference resulting in an electron flow. The electron flow leaves behind reactive ions that readily combine with atmospheric oxygen to form oxides (rust).

There are five types of electrolytic corrosion:

A) Solution corrosion: strong solutions such as blood or saliva formed electrolyte and caused corrosion as either an acid or base.
B) Debris corrosion: debris such as cement or dried blood sets up a potential difference resulting in electron flow and rust at the edges.
C) Heat corrosion: heat accelerates the corrosion process by increasing the rate of molecular reaction; heat itself will not cause corrosion.
D) Stress corrosion: it involves lattice distortion at the point of stress in metals, producing an area of differential electrochemical attack that may lead to breakage and corrosion.
E) Pit corrosion: the invaginated surface caused by scratches, hinge ware, or previous corrosion will produce pit corrosion. Galvanic reaction between dissimilar metals can also cause pitting.

Conditions such as extreme temperatures, physical abrasion, galvanism, or reactive extraneous ions that disrupt the chromium oxide layer will render the steel vulnerable to corrosion. Instruments made of carbon or 400 series steel are more susceptible than those of 300 series steel.

Recent studies showed no significant difference in mean wear whether sterilized with steam autoclave or dry heat.

To reduce corrosion:
 Clean and remove debris from the instruments and rinse with distilled water.
 Avoid tap water which contains dissolved alkali and metallic ions.
 Water must be deionized and of good quality.
 Keep the pH of steam above 6.4; otherwise pitting will occur.
 Chrome plated instruments and stainless steel instruments should be sterilized separately because the electrolyte action can carry carbon particles from the exposed metal of a chromium plated instrument and get deposited on stainless steel.
 It is better to keep the instruments in wrapping. Detergents with chloride bases should be avoided because chloride residue unites with steam to form HCl.
 Detergents with pH of more than 8.5 may disrupt chromium oxide layer.

CONCLUSION

Effective infection control must be a routine component of professional activity. The use of universal precautions in the management of all patients greatly minimizes occupational exposure to microbial pathogens.

Discrepancy between “the ideal” and “the real” in dental asepsis provide fertile ground for rash statements of two kinds “sterilize everything versus do nothing, the mouth is a dirty place”.

Both are expressions of compulsion, fear or frustration about a seemingly impossible dilemma. They may reflect the sentiment “go away; let me alone”.

It is incumbent upon each orthodontist to conduct his practice in a manner that will not cause harm to anyone. By following the procedures outlined here, the orthodontist can minimize and even prevent the possibility of cross infection. This may be the best protection against the transmission of hepatitis and other diseases and perhaps, the filing of a malpractice suit. Practical reality, of course dictates that to prevent possible spread of
infectious diseases, dental professionals must be provided with up-to-date information that can be utilized to develop an optimal programme of asepsis.

bonding in orthodontics

The introduction of bonding to orthodontics added a new dimension to fixed appliance therapy. With a considerable reduction in the need for banding teeth, there was an improvement in patient comfort, esthetics and oral hygiene maintenance. The incidence of caries was reduced as was chair side time and there were no interproximal spaces left after finishing the treatment.

Buonocore in 1955, was the first to demonstrate that bonding of acrylic restorative material was substantially increased by conditioning the enamel surface with 85% H3PO4 for 30 seconds.

Newman in 1965 was the first to apply these findings and bonded plastic brackets with an epoxy resin after etching with 40% H3PO4 for 60 seconds.

Mitchell in 1967 described a successful, although limited clinical trial using black copper cement and gold direct attachment.

Smith in 1986 introduced zinc polycarboxylate cement and bracket bonding with this cement was reported.