RECYCLING OF

ORTHODONTIC

BRACKETS

JERUN JOSE

3rd YEAR PG

CONTENTS

INTRODUCTION

METHODS OF RECYCLING

STAINLESS STEEL BRACKET RECYCLING

CERAMIC BRACKET RECYCLING

SELF LIGATING BRACKET

CONCLUSION

REFERENCES

INTRODUCTION

Orthodontists are commonly faced with the

decision of what to do with debonded or

inaccurately positioned brackets that require

re-positioning during treatment

One solution is to recycle the brackets

The aim of any bracket recycling system is to

remove the adhesive from the bracket base

completely without causing structural damage,

in order to eliminate all impurities related to

orthodontic treatment, so that the bracket can

be rebonded to enamel producing a new

adhesive bond of adequate strength

Methods of recycling

Stainless steel bracket recycling

Two types

In office method

Commercial methods

IN OFFICE METHODS

1. Grinding

2. Sandblasting

3. Direct flaming

4. Big jane machine method

5. Buchman method

6. Acid bath method

7. Laser recycling

Grinding

A green stone/ tungsten carbide bur operated on

straight slow-speed handpiece at a speed of 25,000

revolutions per minute for approximately 25

seconds

mechanical adhesive grinding is quick, simple and

easy to perform as a chairside in-office procedure

Basudan etal JO 2001

Changes

Grinded brackets shows continuous resin coverage that blocks all retentive areas.

Control Grinded

Here all available undercuts were filled with the

adhesive with a nearly continuous resin

coverage above the level of the wire mesh

intersections.

Recycling effects

Flattening and loss of meshwork was seen

Reduction in bracket bond strength(Wright and

powers ,1985)

This is the least efficient method

Sandblasting

Danville portable-sandblasting unit with

25,50,110 µm aluminium oxide abrasive

powder can be used.

The distance between the bracket base and the

handpiece head was fixed at 10 mm distance.

Each bracket base was sandblasted for 20 to 40

seconds under 5 bars (72.5 psi)

line pressure

Basudan etal JO 2001

Sandblasted bracket showing rough intact and clean base

Control Sandblasted

The sandblasted bracket bases were dull and

rough with an intact multi-stranded structure,

and the retentive areas were less well-defined

With sandblasting, as the sizes of the aluminum

oxide particle increased, SBS (shear bond

strength)decreased with successive rebonding.

With sandblasting, the greater the aluminum

oxide particle size and the greater the number

of rebondings, the greater the percentage of

bond material remained on the teeth

In other words, more bond failures occurred at

the bracket-adhesive interface

MONTERO, VICENTE Angle Orthodontist 2015

New bracket base

25 µm Al2O3 50µm Al2O3 110µm Al2O3

No significant differences were found in the

time needed to clean bracket bases clinically

using sandblasting with different aluminum

oxide particle sizes.

For recycling in the dental clinic, the use of

sandblasting with an aluminum oxide particle

size of 25 µm is recommended.

Recycling effects

Regan et al (1993) reported significant reduction in

SBS following sand blasting

sand blasting technique increased bond strength

and survival time of new brackets, Sonis

(1996),Millet etal(1993),MacColl etal(1998)

Sonis AJODO 1996

The increase in SBS values can be attributed to

the micro-roughness created by the alumina

particles, which therefore creates an increased

bonding surface area that is essential for

retention

Direct flaming

The flame tip of a gas torch flame was pointed at the

bracket base for 3 seconds, during which the

bonding agent started to ignite and burn out.

Then, the bracket was immediately quenched in

water at room temperature and dried in an air

stream.

Flamed bracket showing smooth intact wire

mesh and clean retentive areas

Control Flamed

Stainless steel can be heated to 400 to 500°C

before it begins to loose hardness and strength.

Beyond 650°C the temper is lost

Recycling effects

Effect of thermal treatment is evaluated by

measuring hardness and tensile strength

Hardness and tensile strength are decreased in

thermal treatment.

Flaming alone led to significantly lower shear

peel bond strengths that were even lower than

those obtained when grinding the base with a

greenstone only.

Bracket can discolour

Metal is softened by the heating process, and is

thus more vulnerable to masticatory damage

Decreased tarnish and corrosion resistance

If the steel is heated to high temperatures, a

chromium carbide precipitate is formed and, as

a result, becomes susceptible to intragranular

corrosion, leading to general weakening of the

structure.

This is the reason, in general, that recycled

brackets release higher amounts of ions than

new ones

Maria Francesca etal. Am J Orthod Dentofacial Orthop 2010

Ionic leaching can be accelerated by heat

treatment during the reconditioning process

It has been demonstrated that the release of

metals from stainless steel appliances increases

after heating to 400 C to800 C.

Big jane machine method

From the company ESMADENT

The brackets were placed for 60 minutes in the

furnace, which was preheated to 850°F (454°C)

Then quenched immediately in room

temperature cement solvent

This was followed by ultrasonic cleaning for

10-15 minutes, rinsing in hot running water,

and drying in an air stream

then electropolished using the supplied cement

solvent for 50 seconds

showing intact wire mesh with few adhesive

remnants

Control Big jane treated

Method is relatively complicated and require longer

times to perform.

Recycling efects

No effects on slot width and interwing gap

measurements of the bracket

No damage to the multistranded structure of the

mesh work

Buchman method

a Bunsen burner flame was directed at the

bracket base for a few seconds (5-10 seconds)

until the bonding agent started to ignite and

burn, then quenched in water at room

temperature .

Then, a laboratory sandblaster with 50µm

aluminium oxide particles was used to

sandblast the bracket for 5 seconds.

Buchman.AJODO 1980

The distance between the bracket base and the

handpiece head was fixed at 10 mm distance

under 5 bars (72.5 psi) line pressure

Then electropolishing of bracket done

showing intact, but slightly rough wire mesh with clean retentive areas

Control Buchman bracket

Recycling efects

Buchman method can cause an increase in slot

width and interwing gap

But this is clinically insignificant

This mehod is complicated and requires longer

times to perform

Acid Bath

Technique from Salahudheen and Omana

Gheevarghese

After the adhesive has been burned off to

submerge the bracket for five to 15 seconds in a

solution of 32% hydrochloric acid and 55%

nitric acid, mixed in a 1:4 ratio

Recycling Debonded Brackets with an Acid Bath. JCO 2004

This process rapidly removes any tarnish,

dissolves any adhesive residue, and has a

disinfectant effect.

A simple, quick, and inexpensive way to clean a

bracket

The acid should be handled with great caution,

and it is absolutely essential that the bracket be

thoroughly rinsed under running water for 30

to 60 seconds after the acid bath

The bracket is then air dried and ready for

rebonding

New bracketFlame + micro

etcherFlame +acid

bath

Recycling effects

Slot enlargement

Base flattening

Power arm thinning

Recycling by LASER

The development of erbium : Yttrium

Aluminium garnet (Er, : YAG) laser permits

ablation in both soft and hard tissues without

any thermal side effects

Laser of 250 mJ energy at 12 Hz with an average

power of 3 W was applied to the bracket for 5 s.

The Er: YAG laser has a wavelength of 2940 nm.

The adhesive was removed by holding the

bracket with a bracket-holding tweezer away

from the body and lasing the base of the bracket

from top to bottom.

Protective eyewear provided by the

manufacturer was used for the whole

procedure.

Adhesive removal was found to be almost

complete with this group.

The bracket base was seen to closely resemble

that of the control group

The adhesive remnant on the bracket base was

negligible.

The meshwork was clearly visible

Normal bracket Laser applied bracket

Recycling effects

The increased shear bond values could be due

to the lower penetration energy of the laser and

the selective absorption toward composites.

SEM evaluation showed adhesive removal to be

almost complete with this group and the

bracket base was seen to closely resemble that

of the control group.

Commercial methods

Main commercial processes for recycling

orthodontic brackets use a thermal or chemical

method to remove the adhesive.

Vittorio etal. EJO 2004

Based on heat application

Recycling process used by the Esmadent

Company (Highland Park, Illinois, USA).

With this system, the brackets are heated to

454°C for 45 minutes.

Following this the hot brackets are immersed in

a cold cement solvent and ultrasonically

cleaned for 10-15 minutes

The brackets are then washed, dried, and

electropolished for 30-45 seconds and placed in

sodium bicarbonate solution to neutralize the

electrolyte, followed by hot water rinsing.

Fifty micrometres of metal are removed by this

method.

Recycling effects

Small decrease in hardness and tensile strength

Carbide separation of metallic granules

Chemical method

Method used by the Orthocycle Company

(Hollywood, Florida, USA)

A solvent stripping process together with high-

frequency vibration is carried out at

temperatures below 100°C to remove the

composite

This is followed by heating to 250°C for

sterilization and a very short electropolishing

stage (45 seconds).

The company states that 5-10 um of metal are

removed (Postlethwaite, 1992)

Recycling effects

No change in hardness ,tensile strength and

microstructure

Recycling of self ligating brackets

Self-ligating brackets have a mechanical device

built into the bracket to close the slot; this

device carries a much higher cost than that

associated with conventional brackets.

Therefore, it might be useful if the orthodontist

could manage the in-office reconditioning

processes without affecting the shear bond

strength (SBS) of these brackets

Reconditioning of self-ligating brackets .A shear bond strength study .AO -2012

In this study self-ligating brackets were tested:

Smart Clip (3M, Monrovia, Calif), Quick

(Forestadent, Pforzheim, Germany), and

Damon3MX (Ormco, Glendora, Calif)

The reconditioning process was carried out

using a sandblasting unit with 50µm aluminum

oxide abrasive powder.

The distance between the bracket base and the

hand-piece head was fixed at a 10-mm distance.

Each bracket base was sandblasted for 20–40

seconds under five-bar (72.5-psi) line pressure

Quick Quick

Before After

Smart Clip

Damon3MX

Quick

Effects of recycling

Smart Clip and Damon3MX reconditioned brackets

showed significantly lower SBS than did new ones.

On the contrary, Quick reconditioned brackets

showed significantly higher SBS than did new

brackets

Ceramic brackets recycling

Many orthodontic manufacturers state that

ceramic brackets are 'for single use only'.

According to the instructions issued by GAC

(GAC International, Inc., Commack, NY, USA),

during debonding, ceramic microcracks could

occur, causing the brackets to be broken, if

recycled.

Recycling effects on ceramic brackets .EJO1997

Unitek (Unitek Corporation, Monrovia, CA, USA)

state that ceramic bracket recycling would

considerably decrease the bond strength

Lew and Djeng (1990) described a simple chairside

technique for recycling used (Transcend) ceramic

brackets which involves heating the brackets to

cherry red to burn off the adhesive from the bracket

base

Lew ,Djeng JCO 1990

Technique

First, remove any composite resin remaining on

the bracket base .

Hold the bracket with a pair of tweezers and

heat it in a Mini-Torch until it turns cherry red.

Scanning electron microscopic picture of

ceramic bracket after debonding

On cooling, the residual composite resin will

turn chalky white and flaky.

It can easily be removed by gently tapping the

bracket on a table top or by lightly scraping the

base with a wax knife.

This produces a clean surface

Let the bracket cool for five to 10 minutes until

it reaches room temperature.

Dry it with compressed air to remove any

possible residue.

Rinse it in 100 percent isopropyl alcohol or-

pure acetone, and allow it to air dry.

Ceramic bracket bases use either a mechanical

or a chemical interlock to adhere to the etched

enamel surface.

The silane used for chemical retention will be

destroyed by this heating procedure.

To restore the silane layer on chemically treated

bases (or, if desired, to improve the retention of

mechanically interlocking bases), brush on a

thin layer of a porcelain primer such as Ormco

Porcelain Primer or 3M Scotch Prime

The primer's silane coupling agent chemically

unites the silica component of the bracket base

with the composite resin.

Heating procedure does not destroy the silica

component of the bracket base.

Recycled bracket Unused ceramic bracket

Effects after recycling

The shear bond strengths of recycled ceramic

brackets were clinically adequate

The amount of change in slot width and depth,

after ten cycles, was of little clinical relevance.

Advantages of recycling

The major advantage of recycling is the economic

saving, which could be as high as 90 per cent, due to

the fact that a single bracket can be reused up to five

times .

Smoother, more corrosion-resistant bracket after

electropolishing, and sterility as a result of the

temperatures employed in the recycling process.

Disadvantages

Reduction in bracket quality

Loss of identification marks

Lack of sterility

Increased risk of cross-infection

Commercial recycling, whether by heat or

chemical means, leads to a degree of metal loss

in certain areas of the bracket and a reduction

in the diameter of the mesh strands

Conclusion

Reconditioned brackets can be of benefit to the

profession, both economically and ecologically,

as long as the orthodontist is aware of the

various aspects of the recycling methods, and

that patients are informed about the type of

bracket that will be used for their treatment.

References

Comparison of shear bond strength of brackets

recycled using micro sandblasting and industrial

methods. Manuela M. Haro Montero Angle

Orthod.2015;85:461–467

Office reconditioning of stainless steel orthodontic

attachments. Andrew N. Quick European Journal of

Orthodontics 27 (2005) 231–236

Wright WL, Powers JM. In vitro tensile bond

strength of reconditioned brackets. Am J

Orthod. 1985;87:247–252.

Buchman DJL. Effects of recycling on metallic

direct-bond orthodontics brackets. Am J Orthod.

1980;77:654–668.

Quick AN, Harris AM, Joseph VP. Office

reconditioning of stainless steel orthodontic

attachments. Eur J Orthod. 2005; 27:231–236

Sonis AL. Air abrasion of failed bonded metal

brackets: a study of shear bond strength and surface

characteristics asdetermined by scanning electron

microscopy. Am J Orthod Dentofacial Orthop.

1996;110:96–98.

Martina R, Laino A, Cacciafesta V, Cantiello P.

Recycling effects on ceramic brackets: a

dimensional, weight and shear bond strength

analysis. Eur J Orthod. 1997;19: 629–636

Basudan AM, Al-Emran SE. The effects of in-office

reconditioning on the morphology of slots and bases

of stainless steel brackets and on the shear peel

bond strength. J Orthod. 2001;28:231–236.

Recycling effects on ceramic brackets .EJO1997

Reconditioning of self-ligating brackets .A shear

bond strength study .AO -2012

Lew ,Djeng JCO 1990