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Chapter 14 Bonding in Orthodontics

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Christine Chny

on 18 March 2014

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Transcript of Chapter 14 Bonding in Orthodontics

Bonding in Orthodontics
CERAMIC BRACKETS
Machined from monocrystalline or polycrystalline aluminum oxide
Bond to enamel by 2 mechanisms:
CERAMIC BRACKETS
DRAWBACKS:
1) The frictional resistance between orthodontic wire and ceramic brackets is greater and less predictable than it is with steel brackets
CERAMIC BRACKETS
4) Ceramic brackets are more difficult to debond than steel brackets, and wing fractures may occur easily during debracketing.
BRACKETS
3 types of attachments in orthodontic bracket bonding:
Plastic brackets
Ceramic brackets
Metal brackets (Stainless steel, gold-coated, titanium)

Bonding to Porcelain
Hydrofluoric acid
Bonding to Porcelain
Bonding to Amalgam
Modification of the metal surface (sandblasting, diamond bur roughening)
The use of intermediate resins that improve bond strengths
New adhesive resins that bond chemically to precious or non-precious metals
Bonding to crowns and restorations
MICROETCHER
Bonding to Amalgam
Bonding to Gold
High in vitro bond strengths to gold alloys have not been confirmed by satisfactory clinical results when bonding to gold crowns.
Bonding to Composite Restoratives
Brackets bonded to a fresh, roughened surface of old composite restorations appear to be clinically successful in most instances.
METAL BRACKETS
rely on mechanical retention for bonding:
Christine Joy S. Chny, DMD
PLASTIC BRACKETS
Polycarbonate
Esthetic reasons
DISADVANTAGES
lack strength
wire slot wear
uptake of water
discoloration
need for compatible bonding resins
INDICATIONS
minimal force situations
treatments of short duration
Plastic brackets with or without steel slot inserts
as an esthetic alternative, but added bulk is required to provide adequate strength to tie-wings
1) Mechanical retention
via indentations and undercuts in the base
debonding is at the adhesive-bracket interface
2) Chemical bonding
by means of a silane coupling agent
debonding is at the enamel-adhesive interface
2)Cermaic brackets are not as durable as steel brackets and are brittle by nature
3) Ceramic brackets are harder than steel and rapidly induce enamel wear of any opposing teeth
5) The surface is rougher and more porous than that of steel brackets and hence more easily attracts plaque and stain to the surrounding enamel.
6) The added bulk required to provide adequate strength makes oral hygiene more difficult.
a) mesh gauze
b) photoetched recessions or machined undercuts
small, less noticeable metal bases
base should follow the gingival margin
base must not be smaller than the bracket wings
must be kept out of occlusion
METAL BRACKETS
Disadvantage: Corrosion
type of SS alloy used
galvanic action
bracket base design
oral environment
thermal recycling of brackets
TITANIUM
GOLD-COATED BRACKETS
Maxillary premolars and mandibular anterior and posterior teeth
More esthetic than SS
Neater and more hygienic than ceramics
50Mm white or 90Mm tan aluminum oxide particles
7 kg/cm2 pressure

rebonding loose brackets
increasing the retentive area inside molar bands
creating micromechanical retention for bonded retainers
bonding to deciduous teeth.
A. The appliance consists of a container for the aluminum oxide powder, a pushbutton for fingertip control, and a movable nozzle. B. Improves retentive surface of loose brackets before rebonding.
A strong acid that produces an appearance of a frosted etched porcelain similar to that of an etched enamel
A, B, When hydrofluoric acid gel is used close to the gingival margin, particularly in the mandible, one must use a light-cured blockout resin such as Kool-Dam to protect the soft tissues from the acid.
Plastic
Steel-slotted ceramic
Metal
BRACKETS
Technique may involve:
Bonding to Amalgam
Sandblasting (Microetcher)
Diamond bur
Bonding to Amalgam
Lack of clinical relevance in laboratory studies on bonding
1) Different type of loading
2) Different debonding technique
3) Different environment
Ligation of Bonded Brackets
Rule of thumb: the ligature wire should be twisted with the strand that crosses the arch wire closest to the bracket wing. This tightens the ligature when the end is tucked under the AW.
Intraoral sandblasting of amalgam restoration,
frosted appearance indicates increased micromechanical retention
Bonding to Amalgam
(Small) Sandblasting (Large)
Surrounding enamel is conditioned with
37% phosphoric acid for 15s
Apply uniform coat of primer for 30s
Apply sealant and bond with composite resin
Indirect bonding
3M Unitek
CLINICAL PROCEDURE: Indirect Bonding
Preparation of the Patient
Indirect Bonding
Bonding placement is accomplished with chemically cured sealants or bonding resins
Indirect Bonding
ADVANTAGES:
1) Accurate bracket placement
2) Optimizing the use of the doctor's time
3) Avoids fitting of posterior bands
4) Eliminates the need for separators
5) Improved ability to bond posterior teeth
6) Improved patient comfort and hygiene
Precise Bracket Placement: Effective and Efficient Indirect Bonding
HEAT-CURED RESINS
GLUE
CANDY
DISADVANTAGES:
1) Technique sensitive
2) Additional set of impressions needed
3) Posterior attachments more likely to fall if the patient abuses the appliance
Increased viscosity
Quick set time of 30 seconds
Completely cured in 2 minutes
Place the upper and lower models in the TRIAD 2000 curing unit and cure for 10 mins.
Spray the brackets lightly with a separating spray for less than 1 second to facilitate easy removal of the tray from the brackets.
Silicone Impression Material
Remove the bonding trays from the models by soaking the model for an hour to permit the separating medium to dissolve or by sectioning them off with a bur.
Laboratory Procedure: Preparation of Bonding Trays
Position the brackets carefully on the working model and remove any excess resin.
The indirect bonding trays can now be placed over the brackets.
Bioplast layer (1.5 mm)
Biocryl layer (0.75 mm) provides rigidity of the tray
Alternative Method
One minute of additional curing is recommended to ensure complete polymerization of the resin base.
1) The author recommends using an antisialagogue such as atropine or propantheline
2) Apply pumice to all teeth
3) Rinse and suction the mouth well with water
4) Show the bonding trays to the patient and explain the value of proper bracket placement and the doctor's input on appliance design.
5) If bands need to be fitted, complete this procedure after completing the indirect bonding procedure.
Dab Etching solution onto teeth for 15 seconds. The etched teeth should have a frosty appearance and be completely dessicated.
Indirect bonding Resin A is placed onto the tooth surface and Resin B can be painted on the resin pads in the tray
Position the tray over the teeth and seat the tray in a hinge motion. Hold for a minimum of 30 seconds.
Remove the Biocryl or outer layer with a scaler.
A scaler being used to remove the excess resin around the brackets
Initial archwires engaged. Note the control over molar positioning with the initial AW and the verical control introduced by precise bracket placement.
Placement of Bonding Trays
The inner bioplast layer is removed with a scaler and the fingers.
Dental floss being used to check that all contacts are open
Rebonding
Technique:
1) Remove any adhesive remaining on the tooth surface with a Tungsten carbide bur. The adhesive remaining on the loos bracket is treated by sandblasting.
2) The tooth is etched with 35% phosphoric acid gel for 15 s.
3) After priming, the bracket is rebonded.
4) The neighboring brackets are religated first, and then the rebonded bracket is ligated.
*A loose ceramic bracket should be replaced with a new, intact bracketfor optimum bond strength.
Recycling
The main goal of the recycling process is to remove the adhesive from the bracket completely without damaging or weakening the delicate bracket backing or distorting the dimensions of the bracket slot.
Heat (450 degrees)
Electropolishing (to remove the oxide buildup)
Solvent stripping with high frequency vibrations
Debonding
The objectives of debonding are to remove the attachment and all the adhesive resin from the tooth and restore the surface as closely as possible to its pretreatment condition without inducing iatrogenic damage.
The clinical debonding procedure may be divided into
two stages:
1. Bracket removal
2. Removal of residual adhesive
Bracket removal: steel brackets
Technique:
To squeeze the bracket wings mesiodistally and lift the bracket off with a peel force.
The break is likely to occur in the adhesive-bracket interface which leaves adhesive remnants on the enamel.
Bracket removal: ceramic brackets
Technique:
To lift the brackets off with peripheral force application.
Separation is at the bracket-adhesive interface with little risk of enamel fracture.
Removal of residual adhesive
Accomplished by:
1) Scraping with a sharp band or bond-removing pliers or with a scaler
2) Dome-tapered carbide bur (#1171 or #1172)
Light painting movements
Water coolant
30,000 rpm
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