Evolution of orthodontic brackets

Newer Brackets
www.indiandentalacademy.com

Self-ligating brackets
Ceramic brackets

Self-ligating brackets have an inbuilt metal labial face, whichcan be
opened and closed. Brackets of this type have existedfor a surprisingly
long time in orthodontics— the RussellLock edgewise attachment being
described by Stolzenberg in1935. New designs have continued to
appear, the Timebracket becoming available in 1994, the Damon SL
bracket in1996 and the TwinLock bracket in 1998, being three designs
from that decade. This continued activity is in spite of thefact that self-
ligating brackets have, until recently, neverattracted more than a small
percentage of bracket sales. Thelatest and most significant
developments have been the Damon2and In-Ovation brackets in 2000.
These brackets exhibit majoradvances in robustness and ease of use,
have rapidly grown inpopularity and merit a scrutiny of the current
situation inthis class of bracket

Ideal propertiesof any ligation system
Ligation should
be secure and robust
ensure fullbracket engagement of the archwire
exhibit low friction betweenbracket and archwire
be quick and easy to use
permit highfriction when desired
permit easy attachment of elastic chain
assist good oral hygiene
be comfortable for the patient

What is wrong with conventional ligation?
Failure to provide and to maintain full archwire engagement
High friction
For elastomerics, the force (and thereforetooth control) decaysand
they are sometimes lost
Potentialimpediment to oral hygiene
Wire ligation is very slow
Wireties are secure, robust, enable full, partial or distant ligation,
and have lower friction than elastomerics. Their largest
drawbackis the time required for ligation. Elastomerics are
quick, butless good in every other respect

Advantages of Self – ligating Brackets

Reduced Resistance
Brackets seat the arch
wire in the base of the
slot for predictable
results without the high
resistance associated
with traditional steel and
elastomeric ties

Reduced Chairtime
In terms of initial
placement (and then
eventual replacement)
conventional ligation
techniques are extremely
time consuming
Self-ligating systems
have been shown to
require up to 75% less
time for arch wire
changes

Enhanced Hygiene
Elastomeric ties deform and
decompose, and their decay
may attract plaque near the
enamel surface
Steel ties have sharp edges
that can attract plaque and
irritate the patient, while
increasing the risk of cross-
contamination
Self-ligation integrates clips
into the bracket body reducing
many of the potential “plaque
traps” that may be associated
with enamel discoloration or
gingival inflammation

Enhanced Inter-Bracket
Distance
Greater inter-bracket
distance equals greater
working range
Without the binding and
clutter of bulky
elastomers, the added
wire length – especially
with near constant, low
force type arch wires –
can relieve periodontal
stress

Active Vs passive Slide

Active and passive self ligation refer to the action of the locking
slide or clip on the wire
Active self- ligating bracket
eg: speed, sigma and time have active clips
The aim of active ligation is to seat the arch wire against the
back of the bracket slot for rotational and torque control
Passive self ligating bracket
eg: Damon SL,EdgeLok and Wildman twinlock
When the slide is closed, the lumen of the slot is full size
In active self- ligation, the energy to control rotations is primarily
derived from the clip; in passive ligation, the energy is stored
and expressed in the high-tech wires

The intended benefit of storing some of the force in the clip,as well
as in the wire is that - a given wirewill have its range of labio-
lingual action increased and, therefore,produce more alignment
than would a passive slide with the samewire
The question of active clip or passive slide may not be themost
fundamental aspect of self-ligation. Although the differenteffects
can be elucidated, it is hard to weigh the extent towhich the
differences between active and passive affect clinical
performance

Cost and treatment efficiency
Currently available self-ligating brackets are more expensivethan
most good quality tie-wing brackets. A modest balancingfactor
is the cost of elastic ligatures, which are, of course,not required
A study of treatment efficiency by Harradine found the following:
avery modest average time saving from a reduction in archwire
placement/removal of 24 seconds per arch
a mean reductionof four months in treatment time (from 23.5to 19.4
months)
a mean reduction of four visits during active treatment (from16 to
12)
the same average reduction in PAR scores for matchedcases
These reports support a view of clinicallysignificant improvements in
treatment efficiency with passiveself-ligating brackets. The more
recent bracket types wouldbe expected to show still better
treatment efficiency

Edgelok
Speed
Activa
Time
Damon SL
Damon SL 2
Damon SL 3
In ovation
Sondhi brackets

Edgelok (1972 - Ormco)

Advantages
Strength
Basic shape is of a slot surrounded on four sides by
contoured metal surfaces
The material is cast chrome alloy - much harder material
than machinable 300-series stainless steel
With a standard edgewise bracket you've got a small
weldin,g base incisco-gingivally and a long torquing arm -
edgelok has a short torquing arm - all but impossible to
shear Edgelok from a band

Smooth to tissue
Button shape provides a smooth, round surface which is
exposed to the tissue
Absence of ties is an obvious additional benefit
Low profile
Edgelok's button shape allows it to be large where needed
for strength, but small in the critical areas
• Occlusal boss can be reduced as much as necessary to
accommodate the occlusion
Even possible to use Edgelok as a bite block

Outline of Edgelok bracket (white
area) overlaid on standard
medium twin bracket with
ligature tie

Automatic locking and unlocking
Elimination of the tedium of tying
Reliable action
Because of Edgelok's strength and design characteristics,
the locking action is extremely reliable
• It clicks open and it clicks shut. There is no intermediary
position
Complete control in all planes of space
Acts like an eighth-inch buccal tube on each tooth
Enforces complete bracket engagement at all times
The bearing or rotating surface is similar to the bearing
surface of the traditional siamese bracket

Edgelok bracket is opened with
simple tool designed for that
purpose

Edgelok has no intermediate position
between open (above) and closed
(below). Complete bracket
engagement is forced at all times

Design
Bracket body – is cast and has the archwire slot
Sliding lock – assembled onto the body
Lock ring – placed on after bracket is welded to a band,
either band material or preformed
Edgelok comes only in one size – fits all teeth inspite of
greater bearing surface than a standard siamese edgewise
bracket - has a small welding flange and is convex in shape
like a lingual button
If lower anteriors are too crowded
• An open coil placed to open a little bit of room
• Wire tied with ligature to saddle horn of the bracket

.014 auxiliary or secondary channel
• Is part of the saddle horn designed so that there would be a
way of tying teeth together
• Allows a tooth that is tremendously malposed to be tied to the
archwire
• Used to keep Alastiks and elastic thread out of the gingivae
• Allows stretching elastics from tooth to tooth and locking it into
the auxiliary channel as you go - eliminates the tedium of
"figureeighting,“ and obtains a much cleaner appearance
Acts as initial bite-opening device
• The bracket cap is sufficiently thick and strong so that it can be
shaved or filed it off incisally without interfering with the strength
of the bracket

Elastic Power Thread engaged in .014
auxiliary channel of Edgelok bracket to
condense six anterior teeth (above) and
in cross-section (below)

Ligature tie to saddle horn of
Edgelok bracket may be used
on severely malposed teeth

A stone may be used to reduce the
incisal portion of the Edgelok
bracket to eliminate interference
and create a bite block effect

Bracket opens incisally
• Nothing is forced toward the gingivae
Opening and closing
• With a plier that works in a w edge fashion on the lock to open
it without any force in an occlusal or incisal direction
Collars
• Available for rotation or for placing an auxiliary tube
• Also for auxiliary elastic hooks, in Class II or Class III
• “Mini-collar" is now available which effectively reduces the
potential for hygiene problems

Collars for use of auxiliaries are available with .021x.021 square
tubes, .021 round tubes, and elastic hooks (left) and plain for
rotation. They are placed and removed with a How plier. The
open end of the collar is placed in the occlusal indents of the
bracket and the collar is snapped over the lock stop (right)

Close-up of newly designed mini-
collar— plain (left) and with
auxiliary tube (right)

Speed (1980 - Strite Industries)

The acronym SPEED has been chosen to identify the
appliance and the system of treatment which is
continuing to evolve with its use. The name is derived
from the descriptive terms
Spring-loaded
Precision
Edgewise
Energy
Delivery
all of which describe features of the design

The main components of the appliance are
Multislotted bracket body
Spring clip
Specially shaped foil-mesh bonding bases

Exploded view of components for a
lower right canine assembly
viewed from mesial, labial, and
occlusal aspects

Description of the SPEED appliance
Bracket Body – has four slots
0.018 by 0.025 inch horizontal arch wire slot opens to the
labial has an 0.75 inch lingually centered radius to its lingual
wall
An 0.017 by 0.017 inch horizontal slot opens to the lingual,
with its gingival wall continuous with occlusal surface of the
welding flanges

Mesiolabial view of a lower right
premolar bracket showing slot
dimensions

A vertical spring slot of uniform and appropriate depth for
each of five different base curvatures opens to the lingual
A shorter and narrower angled instrument-access slot
communicates with the spring slot from the labiogingival
aspect
The bracket body has a shallow transverse groove on its
labial surface a short distance occlusal to the arch wire slot,
a shallow triangular groove, short welding flanges, and no
gingival tie wing

Bracket without spring

The spring clip
Is highly resilient - formed from a high tensile precipitation
-hardened 0.005 by 0.060 or 0.005 by 0.072 inch stainless
steel strip
Each has a short labial arm joined to a somewhat longer
lingual arm by an 0.025 inch (radius) curved occlusal portion
with angle of wrap of 217 degrees 30 minutes when free
from external stresses
In this "resting'' condition spring arms converge at an angle
of 37 degrees 30 minutes

Spring clip prior to assembly.
Note angle of convergence between
its labial and lingual arms

Lingual arm of the spring has an 0.030 inch wide indent
centered near its gingival edge which projects labially
approximately 0.005 inch
After forming and prior to assembly, the springs are
precipitation hardened for 1 hour at 900° F (480° C)

The bonding bases
Just wide enough for a secure laser seam weld to each
bracket flange
Viewed from the labial, mesial and distal edges parallel to
one another and angulated relative to the occlusal edge in
accordance with amount of crown tip required by the type of
tooth to which it has been assigned
Gingival edge is curved gingivally in the form of a semi-
ellipse
Occlusal edge cut "level'' so that its parallel to long axis of
the arch wire slot after pre-angulated welding

SPEED bracket, spring, and pad
assembly for a lower right canine

Three mutually perpendicular axes
which intersect at the arch wire
slot centroid are used to
describe relative spatial
relationships. An experimental
arch wire and slot cross-
sectional geometry also shown

All pads requiring mesiodistal curvature are bent about a
central axis parallel to their mesial and distal edges. Typical
bend radii - 0.10, 0.15, and 0.20 inch
Premolar pads given an additional occlusogingival curvature
appropriately asymmetrical for conformity to usual anatomic
contours of these teeth

Lower right premolar bracket with
mesial half cut away

Shape of the lingual spring slot on a
premolar bracket where a tight-
radius mesiodistal curvature of
the base is required

Bracket-spring assembly
After stress relieving and heat hardening, spring clip
mounted on bracket body by a special procedure to prevent
any plastic deformation
In slot-closed position, arms held apart so as to reduce their
angle of convergence by at least 2 degrees - elastic
deformation - mounted spring embraces the bracket body
and creates a gingival component of force where inclined
inner surface bears against the occlusolabial corner of arch
wire slot
Spring regarded as attempting to propel itself even beyond
the fully closed position

Sectioned SPEED bracket assembly
showing spring clip in both the slot-
closed and parked-open positions.
Note the gingival component of
force which tends to hold the spring
in the closed position

The labially projecting indent on the gingival end of the long
spring arm is housed within the instrument-access slot,
which peters out at the appropriate level for limiting the
occlusal travel of the spring to that required for parking its
labial arm into the slot-open position
This construction also prevents accidental escape of the
spring through excessive opening force

Opening force being applied to the
labially projecting indent on the
gingival arm of the spring clip with
one prong of a ligature director,
while the incisal edge of the tooth
is being supported with the
operator's finger

Elastic deformation of the bracket
spring contributes to the force
system
Use of SPEED Appliance

Straight wire fit in the bracket slot
when the "truing-up" action of
the spring has been completed.
Note that the arch wire is
contacting the lingual wall of the
slot only in the middle

One activation resulting in 29
degrees of premolar rotation,
more than half of which is
attributable to the action of its
bracket

Labial root torque with one
activation of an 0.018 by 0.022
inch arch wire in 0.018 inch
slots

In the slot-closed position
• Converts the arch wire slot - trapezoidal tube having
three rigid walls and an elastic inclined labial wall
• The 0.017 inch lingual horizontal slot- tube, but the area
of the spring forming its fourth wall is next to the
restrained lingual arm – much more rigid – well suited for
receiving square-wire hooks for elastics, ligatures, or
even auxiliaries for various types of tooth movement
• Welding bracket-spring assembly to bonding base
transforms the vertical lingual slot into a conduit housing
the lingual arm of the clip in a close-tolerance (but not
frictional) fit

"L"-shaped hooks in the upper
canine and lower first premolar
brackets for applying "vertical"
elastics

Canine-uprighting auxiliary made
from 0.016 by 0.016 inch wire.
Note 9 degree improvement in
canine inclination over a 7-week
period

Improvised elastic hooks for
reciprocal force to canine

Activa (1986 - A company)

Introduced by Irwin C. Pletcher
The arch wire is retained by a resilient clip that rotates into a
retaining groove gingival to the arch wire, positioning two straps
labial to the wire creating a bracket similar mechanically to a
molar tube with twin channel caps
The clips can be opened and shut with a wide range of
commonly used hand instruments including ligature tuckers, flat
plastics, and Mitchell's trimmers
All brackets have vertical slots (0.020 inch square) behind the
arch wire channel and permanent, as well as painted,
identification marks

Activa bracket with clip open. Clip
retaining groove is visible on
the gingival surface.
Activa bracket with the clip closed
Arch wires engaged in Activa
brackets.Alignment tabs and
distogingival marker dots can be seen

Brackets for the anterior teeth have gingival and occlusal tabs to
assist orientation relative to the facial axis of the clinical crown.
More recently, premolar brackets have been supplied with
rectangular bonding bases
The brackets are also available prewelded to bands

Initial bracket positioning. This
tweezers grip provides good
vision for orientation and control
of composite amount and
distribution but is not suitable for
final seating
Firm pressure for full bracket
seating can be applied through
orientation tags

Activa seating key can facilitate
complete arch wire engagement
and hold this engagement while
closing clip

Advantages of Activa brackets
There are essentially four worthwhile advantages, of which the first
two are much more significant clinically
Low friction between bracket and arch wire
More certain full arch wire engagement
Less chair-side assistance
A vertical slot for hooks and auxiliaries

Initial engagement through
previously closed bracket of
very rotated tooth

Initial visit (8 weeks) producing 40°
of canine derotation

One visit (8 weeks) of derotation
using 0.012-inch nickel titanium
arch wire in 0.022-inch slot

Three successive visits showing
canine retraction with 9-week
intervals between visits

Space closure using nickel titanium
retraction coil on 0.018-0.025-
inch arch wire over 19-week
period

Possible further advantages
It has been suggested that self ligating brackets have further
advantages due to the absence of ligatures and tie-wings
Smoother and more comfortable? (no wire ligatures)
Easier oral hygiene? (no ligatures)
Less cross-infection risk? (no wire ligatures with sharp ends)
Better esthetics? (smaller than many brackets and no
elastomerics to discolor)

Disadvantages of activa
Higher bond failure rate
Less convenient with elastomeric chain
Unfamiliarity
Harder to hold and seat when bonding
Partial slot engagement not possible
Breakage of arch wire retaining clips
Low friction increases wire displacement

Elastic string in lower lateral incisor
bracket to increase friction and
minimize wire swivelling

After overjet reduction with functional appliance, this case was
completed in 5 months with four pairs of arch wires shown here
(second premolars were congenitally absent)

Time (1994)

Introduced by Dr.WolfGang Heiser
The Time bracket is the first one-piece self-ligating system, was
developed over a period of three years using computer
technology
Opening
Can be opened
• dental probe
• its own special opening instrument
A hole machined in the spring clip places the probe in the
correct location
opens far enough for the wire to be inserted, opening limited
by stop between clip and bracket body
Resistance felt when full opening is reached, opening farther
deforms it requiring replacement

Schematic drawing of Time bracket

Instrument for opening/closing clip

If necessary, the spring clip can be removed by over-
opening it or by sliding it mesially or distally – allows bracket
to be used with conventional ligatures
It is possible to replace a spring clip in the mouth, but practically
speaking, the bracket should be removed first
Closing
Time bracket closed by inserting same instrument into the
hole in the spring clip and rotating into closed position

Archwire Friction
Smaller diameter wires
• With smaller wires, there is essentially no difference between
passive, tubelike self-ligating brackets such Damon SL and
active self-ligating brackets such as SPEED and Time
• The Time spring clip is stopped by the wire from contacting the
bracket base for wire sizes up to .018", therefore, it acts like a
convertible tube
• With lesser diameters, there is no contact between the archwire
and the spring clip, so friction is greatly reduced
Larger diameter wires
• When the diameter of the wire exceeds .018", in the case of
Time brackets, the force of the clip will produce friction
• The force delivered by a spring clip to the archwire is 250-350g,
depending on the width of the clip

Thus, the brackets provide very less friction with the smaller
wires used for leveling, retraction, or molar distalization, and
provide torque control with rectangular wires
Not necessary to engage a full-size wire to achieve the
desired torque - spring clip presses the bottom and walls of
the bracket slot
Therefore, torque control achieved much earlier in treatment
An .018" X .025" or .019" X .025" stainless steel archwire
provides the same torque due to torque in wire in an .022"
slot
Time creates the torque; the torque does not need to be added
to the archwire

Torque in bracket

Bracket Profile and Height
One-piece machining allows significant reduction in bracket
profile and height - comparable to conventional brackets
• Minimizes occlusal interference - critical in the mandibular
anterior region
• Combined with an absence of ligatures, elastics, and hooks -
improves patient comfort and oral hygiene
In-out reduction
• The reduced profile required a concomitant reduction in the
bracket's in-out values in the bracket body between the corner
of the slot and the base.

• With a one-piece bracket, this distance is the width of the pad.
The Time bracket therefore had more potential for in-out
reduction than a conventional bracket
• The problem was to calculate seperate in-out values for these
brackets unlike the Tru-Arch form, which was designed
according to Andrews for preadjusted brackets with mesh
bases
• Such one-third reductions in bracket height resulted in a one-
third reduction in the prominence of the central incisor bracket
Time brackets were also designed to incorporate torque -in-
base, which is considered essential for exact bracket
placement

Reduced bracket profile

Rotation Control
Produces a light, continuous force for correction of rotated
teeth
overcorrection is possible with elastics or conventional
brackets
Another way to achieve overcorrection is placing bracket in
an unusual position - can keep a rotated tooth overcorrected
throughout treatment
Debonding Strength
Bracket base has microetched mechanical undercuts.
Several studies have found mechanical undercuts inferior to
mesh bases in terms of debonding strength

Rotation correction

Bracket base

Anatomical Design
Bracket placement is critical to achieving the desired treatment
results
The Crown placement system, which is available with Time and
Crown brackets, makes bracket location easier
Outline of the bracket pad follows the lines joining the
cementoenamel junction to the incisal edge
Contour lines of the bracket pad parallel to the gingival line and
the incisal edges

Bracket placement

Advantages
Early in treatment, when smaller wires are in place, the low
friction permits lighter forces for moving teeth
Unwanted rotations do not occur during retraction, because
of the spring clips and light forces
Additional benefits of light forces include
• less root resorption
• less stress on the TMJ from wear
Early torque control from the interactive spring clips allows
treatment to be finished sooner
The Crown placement makes bonding easier and more
accurate, and the spring clips make archwire changes faster

Damon SL (1996)

Design Criteria for the Damon SL Bracket
Major criteria
Andrews Straight-Wire Appliance concept
Twin configuration
Slide forming a complete tube
Passive slide on outside face of bracket
Brackets opening inferiorly in both arches

Damon SL, are self-locking brackets with passive slides. The
thrust of the Damon SL system is to minimize friction at all stages
of treatment
When the slide is closed, the lumen of the slot is full-size
Rotations
expressed by using high-tech flexible wires to nearly fill the
slot in a labiolingual or buccolingual direction, not larger than
an .019" X .025" archwire in an .022" X .028" slot.
Encroaching on this .03" tolerance from the wire to the back
of the slot increases frictional forces

Sliding mechanics
the intention is not to actively seat the edgewise wire against
the base of the slot
Friction reduced by moving teeth on the corners or edges of
rectangular wires rather than on their flat surfaces
Torque
expressed by the edges of the wire against the superior and
inferior walls of the contained archwire slot
For desired torque control, various bracket torques are
selected for the anterior teeth, prior to bonding

Biocompatible Mechanics
Leveling and alignment occur in much less time
• less harmful effects on roots, bone, or tissue
• fewer complaints from patients about discomfort from tooth
movement
Eg: high maxillary cuspids are engaged - normal response -
adjacent teeth to move superiorly cuspids move inferiorly.
With low-friction mechanics, cuspids erupt without adversely
affecting the adjacent teeth

Archwire Sequencing
First archwire, .014" superelastic nickel titanium
– flexible enough to fully engage in the closed bracket
without restricting the sliding of the teeth along the
archwire
Second archwires, .016" X .025" SE NiTi (.022 slot), .014"
X .025“ SE NiTi (.018 slot) brackets
– used to complete leveling, eliminate rotations, further
archform development, and initiate torque control.
Third and last archwire, an .019" X .025" (.022" slot) or .016"
X .025" (.018" slot)
– completes torque and archform, controls the vertical
dimension during major mechanics, and finishes the case

Conclusion
The impact of this new technology can be summarized as follows
• Improves the quality of treatment due to greater control
• Improves patient comfort during tooth movement
• Shortens treatment time for most cases
– Aligns teeth faster
– Saves time with sliding mechanics
– Requires less time for finishing
• Reduces the number of office visits per patient
• Shortens chairtime for each visit
• Expands treatment planning options
• Simplifies treatment mechanics
• Makes it easier to keep appliances clean
• Improves the work environment for staff
• Improves practice efficiency and profitability
• Attracts a larger segment of the population (more adults)

Disadvantages
Thesebrackets were a major step forward, but suffered two
irritatingproblems —
slides sometimes opened inadvertently
were prone to breakage
Slide breakage was due to
work hardening of the slidecorners
overall length of the slide
play in the slide/bracketcontact - permitted over-opening of the
slide, which couldpass beyond the stop provided by the underlying
U-shaped wire

Damon SL 2 (2000)

Damon SL 2

Damon 2 brackets retain the same vertical slide action andU-
shaped spring to control opening and closing, but place theslide
within the shelter of the tiewings
Manufactured with themetal injection moulding manufacture
technique, which permits closer tolerances
These developments have almost completely eliminated
inadvertentslide opening or slide breakage
Although special and excellentslide-opening tools are provided
with these brackets, they can—aftersome practice—be easily
opened and closed with conventionallight-wire pliers in
combination with the Cool-Tool archwire-seatingimplement

A side effect of this design change is reduced size - an
advantage - larger inter-bracketspan
Unique anduseful feature of the slides on Damon brackets -
theyopen inferiorly in both arches to give an unobstructedview
of the slot
Disadvantages
The lingualcrown torque in the lower second premolars,
although recentlyreduced by 5 degrees, makes slide
opening with conventionalpliers more awkward on thistooth
Whilst the slide closure is very secure, the closefit causes
the force required for closure to vary

Damon SL 3 (2005)

In- Ovation Brackets

• True Twin “Four Tie Wing” design offers rotational control and
versatile use of auxiliaries
• CoCr “Active” Clip provides full slot coverage to gently seat
the arch wire
• A Horizontal Auxiliary Slot for sectionals, uprighting springs,
and rotation springs
• Smooth Rounded ‘Mini’ Posts for versatility and comfort
• A Slot Blocker for preventing the arch wire from escaping the
bracket slotA
Features

6. Rhomboid-Shaped Base for ease of placement
7. Metal Injection Molding for Low Profile design
8. Torque In-Base for level slot alignment CNC milled for precision
and smoothness
9. A Compound Contoured Base for a more anatomical fit
10. Center of Slot ID Marker for better placement orientation
Another feature is bite-ramps used with In-Ovation brackets

Bite Ramps are made from a high
strength resin which resists water
absorption and erosion
Their swept design aids in
redirection of anteriors, and the
material used is more flexible than
stainless steel, making it easier on
the enamel they contact
Bite Ramps work with In-Ovation
brackets by protecting their clips in
deep bite situations.
Bite Ramps may also be used
gnathologically to unload the joint
and relax the mandible

Sondhi Bracket

Ceramic brackets

Fixed orthodontic appliances that combine acceptable esthetics
and optimal technical performance for the orthodontist constitute
a very desirable combination
Contemporary orthodontics provides service to a great number
of adults, especially women, hence the need for optimum
cosmetic appearance of orthodontic appliances has been
reinforced
After their introduction in 1986, various types of ceramic
brackets are currently available by all major orthodontic
manufacturers

Ceramic brackets, unlike plastic brackets, resist staining and
slot distortion and are chemically inert to fluids that are likely to
be ingested
However, are very rigid and brittle
Because of the latter property, debonding pressure on the
bracket base often results in partial or complete bracket failure
or fracture

In the mid 1980s, the first brackets made of monocrystalline
sapphire and polycrystalline ceramic materials became widely
available
All currently available ceramic brackets are composed of
aluminum oxide
However, because of distinct differences during fabrication,
there are two types of ceramic brackets
polycrystalline alumina – readily available
single crystal alumina – noticeably clearer than polycrystalline

Polycrystalline
• manufactured by blending aluminum oxide particles with
a binder so that the mixture can be molded into a shape
from which a bracket can be cut
• The molded mixture is heated to temperatures in excess
of 1800°C to burn out the binder and fuse the particles
together
• This fused part is then machined with diamond cutting
tools to provide the slot dimensions and other critical
tolerances. The machined bracket must be heat-treated
to remove surface imperfections and relieve stresses
created by the cutting operations

Monocrystalline
• Single crystals of man-made sapphire are produced by
making a molten mass of aluminum oxide at
temperatures in excess of 2100°
• This mass is slowly cooled to allow a carefully controlled
crystallization. The resultant crystal is purer than its
natural counterpart
• Orthodontic manufacturers purchase these large single
crystals and mill them into the shapes and dimensions of
various brackets, using ultrasonic cutting techniques,
diamond cutting, or a combination of the two
• After milling, the sapphire crystals are heat-treated to
remove surface imperfections and to relieve stresses
induced by the milling operations

The manufacturing process plays a very important role in the
clinical performance of the ceramic brackets
The presence of pores, machining interferences, and
propagation lines contribute to compromises of bracket use
anytime during clinical use
Because production of polycrystalline brackets is less
complicated, these brackets are more readily available at
present
The most apparent difference between polycrystalline and
single crystal brackets is in their optical clarity - Single crystal
brackets tend to be translucent and clearer
Both are stain resistant

A. GAC's Allure polycrystalline
brackets
B. Ormco's Gem single-crystal
brackets

A. Placement caps used for Unitek's
Transcend brackets
B. Placement caps used for Ormco's
Gem brackets

Disadvantages
Extremely brittle
Surface flaws
Their low fracture toughness results in frequent tie-wing # in
clinical use
Advantages
Esthetically 100%Mode of retention:
Either mechanical or chemical
Chemical bond provided by a layer of silica & silane is
extremely strong and may cause the enamel adhesive
interface to be stressed either during debonding or function

Steel ligatures used with
Gem brackets

Mode of retention of ceramic bracket
Mechanical - underules or through indentation in bracket
base
Chemical - to obtain chemical adhesion between the
ceramic bracket & bonding agent in bracket base - Glass is
added to the alumina oxide base
Strong Si-o-Ceramic Bond - Treated with a Silane
coupling agent, which acts as a molecular bridge linking
inorganic fillers to organic polymers
Combination of above

Contraindication of ceramic brackets
Crack lines
Heavy caries
Large restoration
Hypoplasia & hypo calcification
Thin enamel
Non vital teeth (?)
Inherent defects seen in the morphology of polycrystalline ceramic
brackets severely limit their fracture strength

Remedies suggested
• Reduce the dimensions of the alumina particles to the
size and possibly the number of grain fragment pullouts
• Produce a glazed surface one of the bracket to reduce
the overall surface roughness
• Treat the surface of the bracket either thermally or
chemically to place it in compression, thereby increasing
the applied tensile stress required for fracture
• Ceramic (alumina) bracket fractures easily, by
introducing zirconia in ceramic brackets above
disadvantages have been reduced

Zirconia brackets
Advantages
Surface hardening treatments are available - increase
fracture toughness and there by reduce the likelihood of
fracture by crack propagation
Bond strength obtained with chemically cured composite
adequate for clinical use
Less enamel fracture during debonding
Disadvantages
Zirconia brackets to have problems related to colour and
opacity, which detract from the esthetic and can inhibit
composite photopolymerization

Future of zirconia
May be considered as alloplastic material for the T.M.J.
In that application, low frictional coefficient good wear
resistance light toughness and biocompatibility are critical
parameters
Zirconias are already attractive candidates for biomedical
application such as total hip replacement

Ceramic bracket with metal slot insert

Lingual orthodontics
Pioneered by Dr. Craven Kruz in 1975
Bracket design
Bracket are composed of hardened stainless steel, varying
in width with each tooth in the arch
The bracket are bonded / brazed to a diffusion bonded foil /
mesh base

Difficulties
lnterbracket distance is decreased because bracket
placement is difficult especially in crowded cases, hence
bracket width must be decreased
Since bracket width is decreased mesio-distally, mesiodistal
root control is difficult and cuspid and bicuspid uprighting
after closure of extraction spaces become more difficult – a
possible solution could be use of vertical slot for arch
auxiliaries
Great variation in lingual surface topography – sometimes
malleable base bracket is used

Modern lingual bracket design
Bite plane parallel to occlusal plane and arch wire
Gingival ball hook - facilitates, elastic ligature/ placements,
rotational control, intra, intermaxillary elastics
Edge wise bracket are provided with various degrees of
torque, angulation

Update on the Fujita lingual bracket .J.C.O. 1999
Fujita's bracket introduced in 1979, featured a slot that
opened toward the occlusal
A lock pin inserted M-D into a groove in the slot that opened
toward the occlusal. To secure the arch wire, in conjunction
with a conventional elastomeric or steel ligature
Current Fujita bracket has gone number or modifications
The 0.019 x 0.019 main occlusal slot allows easier arch wire
insertion seating and removal than with lingually opening
slots
An additional benefit is that the arch wire will not pull out of
the slot during space closure
Rotational control is more efficient with the occlusal slot,
since it requires only the insertion of the light wire. The 0.018
x 0.018 lingual slot is generally reserved for sliding
mechanics such as partial canine refraction and various
Tandem archwire systems

During alignment, inhibition of tipping at extraction sites, and
axial alignments such as uprighting and paralleling was possible
Also can be used in space closure and final detailing
The 0.016 x 0.016 vertical slots permits insertion of auxiliary
springs or elastic hooks on one or more teeth at any time during
treatment
The molar bracket has 0.028x 0.022 outer and 0.018 x 0.018
inner lingual slots [slot in slot]
The outer slot of the maxillary molar bracket can engaged a
transpalatal arch to retain an expanded maxillary arch or to
inhibit extrusion of the maxillary 1st molar during leveling

Summary
The multiple slot of the Fujita lingual bracket allow positive
tip and rotation control for a wide variety of more mechanics,
despite the reduced bracket width
Occlusally opening slots are effective in controlling rotations
and vertical slots are useful for M-D root control of individual
teeth with uprighting springs
Lingual slots allow even more treatment possibilities through
the use of Tandem arch wires

Manufacturing Of Brackets

Brackets made by milling are too expensive and at the same
time too prone to human error, in comparison with those made
with the help of molds
The dramatic step forward made by Unitek by milling a one-
piece attachment on the lathe (Dynalock) has opened new
horizons, several companies following suit and coming up later
with one-piece brackets
This has opened the door to one-piece brackets made by
casting (Ortho-Organizers, San Macros, Calif.)
sintering (the partial welding together of metal particles
below their melting point)
metal injection molding (MIM)

Casting
While casting has long been a mainstay for "A" Company, -
first ones to build-in identification marks and torque in the
base, as well as to use more corrosion resistant alloys
the company has not extended the process to one-piece
appliances, fearing retention problems - building in a rough,
high-surface area on the base side of the bracket while
rendering the bracket side smooth and shiny is quite difficult,
considering the minute size of the appliance

Sintering uses only metal powders, which are melted
as such in molds
MIM
adds to these, various thermoplastic polymers, lubricants,
and other additives, which are subsequently pyrolyzed and
gasified
To compensate for the shrinking that occurs, the molds have
to be larger than the parts
the operation is quite sophisticated and requires the use of
computer-aided design, along with computer-numerical
controlled machines tools
The resulting built-in accuracy and microstructural
homogeneity, if not plagued by pores, leads to appliances
having superior mechanical and chemical properties
(brackets made of powders have been found to have a
smaller corrosion rate than both the cast and the cold
worked ones)

Cast,one-piece bracket with built-
in base and power arm
(Edgeway from Ortho-
Organizers, San Macros,
Calif.)

Brackets showing opposite
working principles

Brackets showing different
orientations

Bracket slot sizes
022 versus 018

Evolution
022
Original appliance – gold archwires and 22x28 slot size
Angle’s concept – no sliding required, maximum torque
control
Provided only by large dimension gold wires hence 022 slot
suitable
018
Advent of steel archwires – large dimension wires had
increased stiffness
Reduction in slot size from 022 to 018

Pros and Cons
Sliding teeth became new concept with introduction of
extraction treatment
Requires atleast 2 mm clearance
18 mil wire better than 16 mil wire for sliding
Fit of 18 mil wire in 022 slot better than in 018 slot –
advantage of 022 over 018
Finishing stages – 21 mil wires - increased stiffness,
reduced springiness and range in torsion, 19x25 wire is an
alternative but torquing auxiliaries still necessary with
undersized wires in 022 slot – advantage of 018 over 022
Role of new Titanium, Niti wires becomes clearer…with
continued use of original edgewise slot size……..

Evolution of orthodontic brackets

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Evolution of orthodontic brackets

Similar to Evolution of orthodontic brackets (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Evolution of orthodontic brackets