Bracket positioning : Five steps to align crowns and roots correctly

 Bracket positioning: Five steps to align crowns and roots consistently

A well-finished orthodontic case has the proper alignment of crowns and roots and level marginal ridges. With preadjusted brackets (straight-wire appliances), the position of the bracket on the crown determines the tooth’s final tip, torque,height, and rotation. Poorly positioned brackets result in poorly positioned teeth and necessitate many more archwire adjustments. This can lead to an increase in treatment time or a final occlusion that is less than ideal. 

Unfortu-nately, even under the best of circumstances, ideal bracket placement during initial bonding is often impossible because of limitations brought on by the existing malocclusion or operator error.

Initial leveling often reveals bracket-positioning errors. The orthodontist should first recognize and then correct these errors early in the treatment process so that wire adjustments can be minimized later.

The protocol below describes 5 steps for achieving crown and root alignment. We recommended that each step be performed on every patient undergoing

fully banded therapy. Once integrated into the treatment protocol, it can decrease treatment time and improve final results. 

STEP 1: INITIAL BRACKET POSITIONING

Ideally positioning brackets during initial bonding is challenging. 

In common there are 4 elements that demand attention when positioning brackets: (1) base adaptation, (2) rotational position, (3) vertical position, and (4) slot angulation. Regardless of the bonding technique used, one should strive to optimize each bracket placement relative to these 4 categories.

First, check to see that the contour of the bracket

base follows the contour of the tooth’s surface. The

bracket base may need to be modified to fit some teeth

either by flattening the base or by increasing its concavity. An ideal base contour helps to ensure an even flow of adhesive during bracket seating. However,even when the contour of the bracket base is ideal,incomplete bracket seating can lead to unwanted rotations .

Second, evaluate the rotational position of each

bracket from the occlusal . Center the bracket

mesiodistally for incisors and in line with the labial

cusp tips for canines and premolars. 

in the buccal groove for molars. 

Third, determine the vertical position of each bracket

by using well-fitted molar bands as benchmarks for the

vertical position of the rest of the appliance. Position all

the posterior brackets so the distance from the archwire

slot to the marginal ridge is equal for all neighboring

teeth . This will result in even marginal ridges

when a straight wire is used. The distances from the slots

to the cusp tips may vary. The anterior brackets should

be positioned on the basis of the heights of the posterior

brackets. The canine and adjacent premolar brackets

should be positioned equidistant from the cusp tip, or

with the canine cusp tip just slightly further from the

bracket slot. Upper incisor brackets should be positioned

in such a way that they can establish proper gingival and

incisal edge relationships . Position the lower

incisor brackets at equal distances from the incisal edges

and slightly more incisally than the neighboring canines

Do not use fractured or worn incisal edges as guides for bracket positioning.

Finally, determine the desired slot angulation of

each bracket by evaluating the position of the roots.

Use periapical radiographs as a guide during initial

bracket placement . If the root is well aligned on

the initial radiograph, be sure that the slot angulation is

neutral. If the root alignment needs correction, incor-

porate the needed adjustment into the slot angulation

during initial bracket placement .

STEP 2: PRIMARY EXPRESSION OF BRACKET
PRESCRIPTION AND POSITION

After initial bracket placement, the goal is to com-

pletely express the bracket’s prescription and position

through complete leveling and aligning. For example,

consider a patient who has a set of perfectly positioned

brackets with a bracket prescription that is ideal for the

shape of the teeth. In theory, treatment would required

only that the orthodontist level the bracket slots, finish-

ing with a full-sized wire. The resulting tooth-to-tooth

relationships should be ideal without wire adjustments.

We do not encounter this situation often, but the lesson

it provides is an important one—filling the bracket slot

provides complete expression of bracket prescription

and position.

If, during the initial alignment stage, you find a

severe bracket-positioning error, reset the bracket

while still in the light initial wire (.014 or .016-in

nickel-titanium). This reduces the need to drop down

in wire size at the reset appointment. Minor bracket-

positioning errors, on the other hand, are most effi-

ciently corrected at the reset appointment after the

reset evaluation.

Completely seat a full-sized wire in each bracket

slot before moving on to the reset evaluation. A

smaller wire will only partially express the bracket

prescription and position. 

STEP 3: RESET EVALUATION

The reset evaluation involves both a clinical exam-

ination and a radiographic evaluation. For most

patients, the reset evaluation can take place within the

first 6 months of active treatment. Perform the clinical

examination at the appointment before the reset

appointment and prescribe a root-paralleling radio-

graphic series . 

Examine each tooth individually for bracket-

positioning errors, paying close attention to base adap-

tation, marginal ridge height discrepancies, crown rota-

tions, and nonparallel roots. We note the deficiencies in

each category in a specially designated area on the

patient’s chart . 

Use abbreviations to specify the necessary reset

instructions for each bracket. Our recommended abbre-

viations are as follows : a check mark indicates poor

adaptation of the bracket base to the tooth. This might

be a bracket that was not fully seated or a band with a

distorted margin. An “MO” or “DO” indicates a rotational deficiency. An “MO” indicates that the mesial of that tooth needs to be rotated out toward the labial, and

“DO” indicates that the distal needs to be rotated out.

“I” for intrude and “X” for extrude indicate the neces-

sary vertical adjustments. Finally, a “D” indicates that

the root apex needs to be moved distally and an “M”

indicates that the apex needs to be moved mesially.

STEP 4: RESET APPOINTMENT

The information gathered during the reset evaluation are the instructions for the reset appointment.

Schedule the reset appointment with adequate time for

debonding, debanding, bracket preparation, tooth

preparation, rebonding, and rebanding. We recommend

at least an hour for this appointment.

It is easier to position brackets at the reset appointment than it is at the initial bonding. By the reset appointment, the tooth-to-tooth relationships have greatly improved, making it much easier to assess the relative positions of brackets between neighboring teeth. Also, visibility of each tooth’s facial surface is greatly improved.

Remove the brackets and bands from teeth with

positioning errors. Clean each tooth of excess compos-

ite or cement. Remove excess composite or cement

from the bands and brackets by using a micro-etcher.

Refit each band before cementation. Refitting the band

is particularly important for rotational resets because

initial band fitting and burnishing creates a “rotational

memory” in the band’s metal. This memory can be

removed by reshaping the band with bird-beak pliers

before refitting. Reposition the bands and brackets

according to the principles described in step 1. Use the

root-paralleling radiographs at chairside to determine

the amount of tip correction. 

After cementation and bonding, fully engage the

same .018 × .018-in Sentalloy wire (GAC Interna-

tional) that was used for primary expression of bracket

prescription and position. Use a lighter wire if the posi-

tional change of 1 or more brackets was severe. 

STEP 5: SECONDARY EXPRESSION AND
FINISHING

After the reset appointment, fully express the new

bracket positions by applying the same principles used in

step 2. Secondary expression is usually complete within 6

to 8 weeks. The amount of time depends on the severity of the original positioning errors. After secondary expression, an adjustable wire can be inserted for finishing.

At this stage the orthodontist can be confident that

root alignment has been achieved and no further adjust-

ments for root tip will be needed. Treatment can be

completed with your choice of finishing procedures.

SUMMARY

We have presented a protocol that addresses errors

of initial bracket positioning and facilitates consistent

crown and root alignment. By implementing this proto-

col, the clinician can expect decreased treatment times

and superior results. We have found that although repo-

sitioning does not completely eliminate the need for

wire bends during finishing, it does significantly reduce

their number and complexity. This protocol can be

adapted to fit numerous treatment philosophies and can

be applied to an appliance of any slot size.