Bonding Orthodontic Brackets

7/31/2019 Bonding Orthodontic Brackets

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BONDING ORTHODONTIC BRACKETS

I. Introduction:Palmer notation used in Orthodontics

Right 2n

d

M

1s

t

M

2nd

B1st

BCu LI CI CI LI Cu 1st

B2nd

B1st

M2nd

MLeft

Upper 7 6 5 4 3 2 1 1 2 3 4 5 6 7 Upper

Tooth#

2 3 4 5 6 7 8 9 10 11 12 13 14 15

Tooth#

31 30

29 28 27 26 25 24 23 22 21 20 19 18

Lower 7 6 5 4 3 2 1 1 2 3 4 5 6 7 Lower

The bracket height chart is written in Palmer Notation (Figure 1A). This notationnumbers the teeth starting with the central incisors as 1. The laterals are then 2. The canines are 3. The 1st and 2nd premolars are 4 and 5 respectively, the 1st molarsare 6 and the 2nd molars are 7.

Figure 1A. Bracket Heights from Cusp tip or Incisal Edge

Right 2n

d

M

1st

M

2n

d

B

1st

B

C

u

LI CI CI LI Cu 1st

B

2nd

B

1st

M

2nd

M

Left

Upper 7 6 5 4 3 2 1 1 2 3 4 5 6 7 Upper

Brack et

height

33.5

4 44.5

3.5

4 43.5

4.5 4 4

3.5 3

Inmm

Occ

plane

→

Brack et

height

3.5

3.5 4 4

4.5

4 4 4 44.5

4 43.5

3.5

Inmm



Lower 7 6 5 4 3 2 1 1 2 3 4 5 6 7 Lower



II. Laboratory Exercise:

Step 1: Place Columbia typodont with complete dentition on pole to simulate aclinical situation.

Step 2: Pick up a bracket with the cotton pliers as shown in above figure. It isadvisable to begin with the maxillary central incisor, for this exercise.

Step 3: Place a small dab of white rope wax on back of bracket as shown in abovefigure. The wax is being used as a substitute for the composite bonding materialthat would be used for an actual patient.

Step 4: Place the bracket in center of the facial surface of the appropriate tooth andpress firmly to express the excess wax.

Step 5: Using a perio probe or a boone gauge (if your instructor has one) measurethe height of the bracket from the incisal edge of the tooth to the center of thebracket. For example, horizontal slot of the bracket for the maxillary central incisor

should be 4mm from its incisal edge.

Step 6: Idealize the bracket position mesio-distally and occluso-gingivally (refer toappropriate figure in following pages for tooth specific instructions).

Step 7: Continue with remaining brackets until all have been placed on theappropriate teeth. Evaluate vertical position of each bracket in relation to the incisaledge of the tooth where it is placed, then evaluate the vertical position of each



bracket in relation to the adjacent brackets. Evaluate the mesiodistal position of each bracket. Ask your GTA or faculty to evaluate your bracket positioning.



Bracket Positioning: General Instructions

• Dimple or paint dot identifies disto-gingival

• Center each bracket on the crown long-axis

• Vertical slot between the bracket wings parallel to theCROWN LONG AXIS!!!

• Posterior teeth the center of the bracket slot at theheight of convexity

• Bicuspids - the archwire slot is lined up parallel to a lineconnecting the mesial and distal crest of convexity(proximal contact pts.). This corresponds to the (occluso-

gingival) center of a normally fully erupted clinical crown.

• There are many different systems for bracketing teeth. Recommended bracketheight will vary depending on manufacturer and system.

• Mesio-distal positioning is often best viewed in a mirror similar to checking acrown prep for parallelism.

Maxillary Teeth

Upper Central Incisors

• Distance from the slot to the incisal edge =4mm

• From the occlusal, the bracket is centered

mesio-distally.• The bracket position usually appears somewhat

incisal.

• As a guide, approximate the incisal edge of thetooth with the base of the bracket, perpendicularto the clinical crown long axis.

4





Upper Lateral Incisor

• Distance from the slot to the incisal edge = 3.5mm

• The incisal edges of the maxillary laterals will line up on thesame level or slightly gingival to the central incisors. This is

one-half to one millimeter shorter than the maxillary cuspidtip.

• From the occlusal, the bracket is centered mesio-distally.

• On a fully erupted lateral, the correct vertical position forthe bracket is usually slightly more incisal relative to thecenter of the clinical crown

• Future restorative plan for malformed laterals should befactored into bracket placement

• As a guide, approximate the incisal edge with the slot to align the archwire slotperpendicular to the clinical crown long axis.

Upper Cuspids

• Distance from cusp tip to bracket slot = 4.5 mm

• The severe angulation and prominent anatomy of cuspids(10o) can make placement difficult

• From the occlusal view, the bracket is centered mesio-distally on the prominent buccal developmental ridge. Thisalso corresponds to the clinical crown long axis. This willusually be mesial to the center of the contacts

• Sharp cusp tips on newly erupted canines may need to bemodified

Upper Bicuspids

•

Distance from cusp tip to bracket slot = 4 mm• Upper bicuspid bracket placement is the most difficult

due to individual variability in tooth morphology. Oftenthe brackets are not placed gingivally enough, especiallyon smaller sized or partially erupted teeth, resulting in avertical step between the 1st molar and the 2nd bicuspid.

• From the occlusal view, the bracket is centered mesio-distally on the prominent buccal developmental ridge.

4.5

3.5



This also corresponds to the clinical crown long axis. Thus, the archwire slot islined up with the maximum convexities mesio-distally and occlusogingivally onthe crown.



Mandibular Teeth

Lower Incisors

• Distance from incisal edge = 4mm

• From the occlusal, the brackets are centered mesio-

distally.• Position the archwire slots so that the incisal edges of the

incisors will be one half to one millimeter shorter gingivallythan the cuspid tip after initial alignment.

• With the incisal edge and the base of the bracket as aguide, align bracket wings parallel to the clinical crownlong axis and the base of the bracket perpendicular to thecrown long axis.

Lower cuspid

• Distance from cusp tip = 4.5 mm

• From an occlusal view, the bracket is centered mesio-distally on the prominent buccal developmental ridge. This corresponds also to the clinical crown long axis.Like the upper cuspid this is mesial to the center of thecontacts

• The archwire slot is lined up parallel to an imaginaryline passing through the mesial and distal proximalcontact points. This bracket height will vary dependingon the size of the other teeth, and the size and shape of the cuspid and its cusp tip.

• Press firmly, checking carefully that a vertical line through the bracket wings isparallel with the clinical crown long axis.

Lower bicuspids

• Distance from cusp tip to bracket slot = 4 mm• Centered mesio-distally

• Bracket slot parallels the marginal ridges and contacts

• If a partially erupted 2nd bicuspid is bracketed too farocclusally the marginal ridges will be inferior to adjacentteeth after leveling

• Direct vision of the facial surface is important to properlypositioning the bracket relative to the marginal ridges



Positioning Errors

The most important factor in aligning teeth using contemporary orthodontictechniques is precise bracket positioning. Proper bracket position is critical if ourtreatment objectives are to be achieved with the preadjusted bracket (straight wireappliance).

Correct initial placement of the preadjusted brackets should minimize iatrogeniccomplications. The correction of bracket placement errors tends to be extrusive.Since orthodontic extrusion of teeth is the easiest movement, one can assume thatthe lowest bracket (tooth ) will come up to the level of the highest adjacent bracket.Each subsequent re-bracketing may tend to raise the entire occlusal plane.

III. Clinical Procedure

A. Band Positioning: General Instructions

Maxillary first molar bandsA) POSITION

a) Select a size by using the diagnostic modelb) If the initial band is not the right size then choose a

band 3 sizes larger or smaller and then work toward thecorrect size



c) Seat the distal of the band first, firmly using a band seater or bite stick to utilizebiting force.

d) Seat the band in the patient's mouth until the archwire slot is located in themiddle of the clinical crown occluso-gingivally

e) Excessive seating of the band will cause extrusionf) A small band insufficiently seated will position the buccal tube too far occlusally

g) Uneven seating on the buccal relative to the lingual will lead to torqueerrors, height of the cusps above the band should be equivalenth) Uneven seating on the mesial relative to the distal will lead to tip errors,the band should fit just below the marginal ridgesi) From the occlusal view, the entrance of the mesial of the buccal tubeshould line up with the mesio-buccal cusp tip. As the band is seated, theslot is to be horizontal and level in relation to the crown. Mesial and distalmarginal ridges indicate height and level.

B) ADAPTING BAND AFTER SEATING

a) Once the appropriate band size has been selected, adapt the metalmargins of the band with a plugger or Hauk file.

b) Both right and left bands should be checked to make sure they are in thesame vertical position on the crowns.

Mandibular first molar bands

A) POSITION

a) From the occlusal, the mesial of the buccal tubelines up with the mesio-buccal cusp tip.

b) Seat the lingual first with most of the seatingdone on the buccal and the mesio-buccal.

c) Seat until the archwire slot is located in themiddle of the clinical crown occluso-gingivally.

d) The slot is approximately horizontal and level inrelation to the crown. The buccal cusps canbe used as a guide as well as the marginalridges.

B) ADAPTATION

Adapt well with a band pusher, especially between the distal and the disto-buccal cusps. Bend over any excess band material above the occlusal and



marginal ridges and trim excess away with a stone. A fully seated bandshould fit just below the marginal ridges with no excess to trim off.



B. Direct Bonding: Bonding of Brackets Directly on the Facial

Surface of the Teeth

Direct bonding technique can yieldgood bracket placement withminimum chair time and no

laboratory time.1. All of the teeth are cleaned usinga prophy angle with a mixture of fineflour of pumice and water.2. The teeth are then isolated with acheek retractor and good salivaevacuation is performed. The teethare washed and dried with air waterspray. Maintain a dry field and keepthe tongue out of the way.3. To prepare the teeth for bonding, the facial

surface of each tooth is etched with phosphoric acid for 30 seconds. Wash and

dry all teeth thoroughly as for restorative

procedures.4. The teeth are desicated toexpose a chalky or frostedappearance, indicating an adequateetch has been achieved.5. The facial surface of each tooth issealed with an unfilled resin (or

sealant) and light cured for 5 – 10 seconds.

6. It is advisable to begin bonding in the mandibular arch, as it is the most susceptible to salivacontamination. Bonding material is mixed (if

necessary) and applied to each individual

bracket by the assistant7. Cotton pliers or special bracket placing instruments are used to transfer thebracket from the bracket set up to the tooth. The doctor places the bracket carefullyusing firm pressure to express excess material, removes the excess material andidealizes mesio-distal and inciso-gingival bracket placement.8. The recommended sequence is: lower left and then right bicuspids, cuspids andincisors, working from side to side to insure that the heights are even on both sidesof the mouth. Then the upper bicuspids, cuspids and finally the incisors again

working from side to side (e.g. left second bicuspid, right second bicuspid, left firstbicuspid, right first bicuspid and so on).

Bracket adjustment is done with aninstrument that will fit into the archwire slotof the bracket and allow manipulation of thebracket.



IV. Supplemental information on the direct bondingtechnique

Introduction:

In 1955 Buonocore wrote a paper entitled, A Simple Method of Increasing the Adhesion of Acrylic filling Materials to Enamel Surfaces. He is quoted as saying, " Inan attempt to obtain bonding between filling material and tooth structure, thealteration of the tooth surface by chemical treatment to produce a new surface towhich acrylic filling material might adhere must be explored." This very statementlaid the foundation for contemporary bonding techniques. Interestingly enough, thisconcept was borrowed from the use of preparations containing phosphoric acid inindustry to prepare metal surfaces for better adhesion of paint and resin coatings.Buonocore researched the preceding technique by using phosphoric acid ( 85%! ) toetch the surface to help acrylic adhere to human teeth for considerable lengths of time ( avg. 1070 hrs.). His study brought to light these important factors concerningetched tooth enamel:

a) the acid etching action creates a tremendous increase in surface areaavailable for bonding

b) the exposure of the organic framework of the enamel serves as a network,in and about which the acrylic can adhere

c) old fully reacted and inert enamel surface is removedd) a fresh, reactive surface more favorable for adhesion is exposed.

However, his clinical methods and observations did not take into account the importance of

removing the accumulated organic plaque on the surfaces of the teeth before etching.

Theoretical Considerations:

With the advent of better materials (i.e. orthodontic brackets, isolation devices,bonding systems etc.), the contemporary techniques of orthodontic bonding havegreatly improved. Certain principles must be clearly understood regardless of thenew materials and techniques.

1) Prophylaxis:

A thorough prophylaxis with wet pumice or oil-freeand non-fluoridated prophy paste of the tooth surfaceto be bonded is imperative. Plaque removal from the

enamel surface increases the wettability of thesurface (Figure 1). The greater the wettability thegreater the tendency for a fluid to spread over theenamel surface and the lesser the tendency for a fluidto bead on the surface. Care is taken not to agitategingival tissue during the cleaning procedure toprevent bleeding on the enamel surface to be bonded.After cleaning the enamel surface it is thoroughly



rinsed with water (Figure 2), isolated if needed, and dried (moisture and oilfree air). The success of the next phase of orthodontic bonding technique istotally dependent on proper prophylaxis to increase the wettability of thesurface.



2) Etching:

After prophylaxis the tooth surfaces are ready for etching. The principle of etching is to simply remove microscopic amounts of enamel leaving porosities. This creates an increase in surface area and an architecture favorable formicroretention. There are two types of etching media, liquid and gel. Liquid isapplied by saturating a small sponge pellet with acid and carrying it to theenamel surface (Figure 3). The time for the etching solution (35% to 65%phosphoric acid) to remain on the enamel, is approximately 30 seconds.Etching gel is applied to the tooth with a syringe and remains on the surfacefor 20 – 30 seconds. The surface is rinsed with water for approximately oneminute and thoroughly dried. The final etched surface will have a white chalkyappearance (Figure 4). Etching should be done carefully (avoid contact withthe gingiva and oral mucosa) and in accordance with the manufacturer'sinstructions. This step is one of the most critical factors in successful bonding.Improper etching and moisture control are probably the major causes of failure in bonding.

There are a few precautions to consider during etching. Rubbing the etchanton the surface of the enamel must be avoided since pressure will break newlyexposed enamel rods. The liquid etchant solution should be replenished every10 to 15 seconds to avoid partial evaporation and a more viscous solution, thisis not required with the gel. Salivary contamination of the newly etchedenamel will greatly reduce the eventual bond strength. Isolation andmaintenance of a dry uncontaminated field is critical. Operator inducedcomplications include oil and water contamination from the air hose to the airsyringe. Check the air hose tubing routinely by blowing air on a gauze pad orpaper tissue which will reveal oil and water particles. Minimizing thepreviously mentioned complications, is the KEY to successful orthodontic

bonding.

3) Use of adhesives:

The bonding adhesives used to adhere orthodontic bracket to enamel haveimproved tremendously over the years. During the middle 1970's differentbrands of bonding adhesives strong enough for routine clinical use becamecommercially available to the orthodontist. Clinical research led tocontemporary bonding adhesives that exhibit these qualities:

a) a coefficient of expansion relative to enamel with minimal waterabsorption

b) development of full adhesive strength in a relatively short period of time so arch wire placement can be accomplished in the same visitc) long enough working time to allow the orthodontist to properly

position the bracketd) no toxic effectse) stain resistant



It is important to prevent the bonding system (i.e. etching solution, sealants, and pastes) fromtouching the marginal gingiva during application to the tooth surface. The etchant may chemically

burn the gingiva and cured adhesive near the gingiva will encourage plaque accumulation.

Running an explorer along the gingiva after bonding will detect the thin transparent sealant thattends to form there.

The bonding systems for placement of orthodontic brackets, are of two types:chemical cure or light cure. The chemical cure can be either; a) one step (nomix) or b) two steps. The one step involves no mixing of the bondingadhesives. The polymerization catalyst (liquid) is painted on the back (mesh)side of the bracket pad and the etched enamel surface. The bonding adhesiveor paste is placed on the back (mesh) side of the bracket pad in anunpolymerized form. When the bracket is placed on the tooth surface; thepaste polymerizes. The unpolymerized paste around the margins can beeasily cleaned away. The two step system is the most common and consistsof polymers and catalysts. It usually requires the mixing of a sealant andpaste to accomplish adherence of the bracket to the tooth. The sealant ismixed (two liquids) and applied to the etched enamel surface to preventmicroleakage and to wet the surface. (Figure 5). The paste is mixed (usuallytwo components) vigorously for approximately 20 seconds and applied to theback of the bracket pad (Figure 6). The bracket is placed in the properposition on the prepared tooth (Figure 7). Once the paste on the mixing padbegins to polymerize, do not move or reposition the bracket. At that moment,start a new mix for the next bracket placement. Arch wires can usually beinserted approximately five minutes after the placement of the final bracket. The light cure adhesive is placed similar to restorative composites. Theetched surface is coated with a light cured sealant. Then the adhesive isdispensed directly on to the bracket base and pressed to place. After

positioning the bracket is “tacked” into place with a quick 5-second cure thatprevents drifting while the other brackets are placed. After all brackets arepositioned the full cure of 40 seconds is applied to each tooth. The advantageof the light cure system is nearly unlimited positioning time

References:

Buonocore, M. A simple method of increasing the adhesion of acrylic filling materialsto enamel surfaces. J. Dent. Res. 34: 849, 1955

Sheykholeslam, Z. and Brandt, S. Some factors affecting the bonding of orthodontic

attachments to tooth surfaces. J. Clin. Orthod. 11: 734, 1977Brandt, S. Servoss, J. and Wolfson, J. Practical methods of bonding direct andindirect. J. Clin. Orthod. 9: 610, 1975

Profitt, W. Contemporary Orthodontics, The C.V. Mosby Company, 1986



Bonding Orthodontic Brackets

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