Invisible Tooth Movement Using Thermoplastic Retainers

CONTENTS
• Introduction
• History of Invisalign
• Overview of the Invisalign System
• Understanding the Invisalign System
• Diagnosis and Treatment Planning
• Polyvinyl Siloxane (PVS) Impressions
• Cutting process, creating the Final Setup
• Staging Process
• ClinCheck® Software
• ClinAdvisorTM
2

 Stereolithography process
 Aligner Materials
 Biomechanics
 Attachments
 Orthodontic Treatment with Invisalign Appliance
 Finishing with Invisalign
 Retention and Aligner Cleaning
 Why Invisalign?
 Advantages
 Limitations
 Summary & Conclusions
3

 Physically attractive people achieve higher levels of
success in life than unattractive people.
- Breece and Neilberg (JCO 1986)
 Influence of appearance in personal and professional
lives have led to a considerable interest among the
adult population seeking orthodontic treatment in the
last few years.
4

Minor Tooth Movements Using
Invisible Retainers
 Kesling in 1945 introduced tooth-positioning
appliance.
 Henry Nahoum in 1950’s developed the
vacuum formed dental contour appliance often
termed as the formed “invisibles”.
 In 1971, Ponitz of Ann Arbor, Michigan
introduced so-called “invisible” retainers.
6

Background and Process of
THERMOFORMING
 Thermoplastic sheets were manufactured as far
back as 1896.
 Thermoforming was not well known before
1950.
 Acrylics, styrene were developed in 1930.
 Ethyl cellulose, polyethylene, vinyls, oriented
styrene, celluose acetate and celluose acetate
butyrate followed quickly.
7

Two types of plastic thermoforming
machines dominate the market:
Pressure types
Vacuum types
Pressure machines such as the
Biostar (Great Lakes Orthodontics,
Tonawanda, NY) force heat-softened
plastic over a cast with positive
pressure within a chamber.
8

 A vacuum machine adapts heat-softened plastic
to a cast by negative pressure. Concentrating
the vacuum by reducing the surface area to
which it is applied amplifies the vacuum force
and improves the subsequent adaptation of the
plastic to the cast.
9

Dental Contour Appliance
 By Henry Nahoum
 It’s a vacuum-formed dental contour
appliance.
 Uses:
 Immediate retainer
 Close anterior spaces
 Correct minor rotations
10

 Other uses:
 Splints
 Night guard
 Carry medicaments to gingival tissue
 Hold surgical pack in place
 Control hemorrhage following surgical procedure
 Transport fluoride gels to teeth
 Disadvantages:
 Extra laboratory procedures
 Resetting teeth changes interproximal morphology,
which in turn compromises the fit of the appliance
12

ESSIX TECHNOLOGY
 Essix system is based on in-course
adjustments of what is essentially a single
appliance to achieve the treatment goals.
 Invisalign is unique in that the clinician is
able to plan the path to optimal results
before treatment is initiated so that a series
of aligners can be constructed to achieve
treatment objectives.
13

Case Selection
Clear plastic tooth moving appliances are
excellent options for adults or responsible
adolescents -
Who are reluctant to wear fixed appliances
Who will follow the clinician’s direction
Whose chief complaint centers around mild
to moderate alignment problems
14

3 Essential Elements of
OTM
 FORCE - adequate force to move teeth
without inducing pathology
 SPACE - enough space to accomplish desired
tooth movement
 TIME - appliance must be in place for an
appropriate length of time for the force to be
effective
15

Why Adult Patients?
The clinician can control two of the three prerequisites:
force & space.
As with any removable appliance, the patient must provide
the third essential, ie. time. Therefore the target
population that is most eligible for tooth movement with
plastic appliances is primarily, ADULTS!
In adults although the occlusion may not have ideal dental
relationships, the bite has usually adapted to a non
pathologic efficiency that is satisfactory for a particular
patient.
16

In absence of functional distress, the focus of
treatment with Essix appliances should be
directed at the patient’s chief complaint which is
usually the appearance of anterior teeth.
The clinician, of course, is responsible for
maintaining the pretreatment symptom free
functional occlusion.
17

Creating Space
 Within appliance:
 Blocking out the cast –
light cure composite
 Cutting window into the
plastic - plastic trimming
bur at slow speed
 Within dental arch:
 Interproximal reduction
18

 There are two primary systems of
creating a tooth moving force with an
Essix appliance.
1. Hilliard thermopliers to alter the
appliance by spot thermoforming.
2. Mounding which involves the
sequential placement of small mounds
(layers) of bonding composite to the
surface of the tooth.
19

Force-Inducing Divoter
A device called the Divoter that has been developed
specifically to quickly and accurately thermoform a precision
force-inducing divot in plastic. No cast alteration or resetting
of teeth is necessary.
The heating shaft of the Divoter is 1.5mm in diameter and
has a rounded end. It takes about 15 seconds for the shaft to
reach thermoforming temperature (for .040" Essix plastic
sheet, the temperature dial should be at about the 12:00-
1:00 position). When the shaft is hot enough, slowly press
the tip into the plastic at the exact point where the divot is
needed.
Sheridan, JCO 1994
20

Check the inside of the appliance to monitor the
depth of the forming divot . Before removing the
heated shaft, turn the unit off and dip the appliance
into cold water. Removing the shaft from the plastic
before it has cooled will distort the divot.
The heating shaft of the Divoter must be clean. Use
fine-grit sandpaper, supplied with the unit, to remove
any residual plastic debris prior to use.
Sheridan, JCO 1994
21

The original divot can be progressively deepened
throughout treatment. For example, after the tooth
has moved 1mm, the divot can be extended another
millimeter at the next appointment to produce more
movement.
Since divot depth is proportional to force, excessive
depth will create excessive pressure. We recommend
increasing divot depth by only 1mm at a time and
limiting total correction to 3mm. If the discrepancy is
greater than that, fixed appliances might be a better
option.
Sheridan, JCO 1994
22

 The plastic within the divot becomes thinner with
successive thermal modifications. Therefore, use 1mm
(.040") Essix plastic sheet rather than the standard
.030" used for other Essix appliances.
 This makes for a slightly thicker appliance, but a
sturdier divot. If the divot becomes flimsy, it can be
reinforced with bonding composite, which effectively
converts the hollow divot into a shaft of solid plastic.
 The divot will initially hold the gingival margin of the
appliance slightly away from the tissue. As the tooth
moves, the appliance will conform. To be sure that
adequate divot force is being applied, ask the patient,
after seating the appliance, if there is pressure against
the target tooth. If not, make the divot slightly larger.
Sheridan, JCO 1994
23

Labio-
Lingual
Movements
Lateral
Movements
RotationTorque
Extrusion /
Intrusion
TOOTH MOVEMENTS
POSSIBLE
24

 Limitations:
 Only relatively small magnitudes of change
are possible.
 Technical difficulty of evenly dividing larger
overall movement into small, precise stages
manually.
 Movements are limited to 2 to 3 mm; beyond
this range another impression and a new
appliance are needed.
25

Invisalign® is an orthodontic treatment method in which removable,
clear, semi-elastic polyurethane aligners are used to correct
malocclusions.
The concept of tooth movements with a series of individually
manufactured elastic appliances can be traced back to Kesling,
who attempted in 1945 to achieve tooth movements with
positioners which were fabricated on a series of altered set-up
models. In the meantime, other authors have presented similar
approaches.
However, all these procedures were limited in their practical
use because the technical and financial effort involved in
the continuous fabrication of new models was out of all
proportion to the potential success.
27

HISTORY
 Credit - Zia Chishti and Kelsey Wirth, graduate
students in Stanford University's MBA program.
 Zia Chishti had finished adult treatment with traditional
braces, and wore a clear plastic retainer. He noticed
that if he did not wear his retainer for a few days, his
teeth shifted slightly -- but the plastic retainer moved
his teeth back to desired position when he wore it back.
 Together they started Align Technologies in April 1997
and with the help of a handful of forward thinking
orthodontists, they applied 3-D computer imaging
graphics and created the Invisalign method.
28

 They started it in a garage in Palo Alto,
California, USA.
 Today the company is based in Santa Clara,
California, USA.
 Now they have divisions in Europe, Mexico,
Costa Rica.
 They have 800 employees.
29

 This appliance was the first orthodontic treatment method to
be based solely on three-dimensional (3D) digital
technology.
 Align Technologies received FDA clearance to market
Invisalign in August 1998.
 The Invisalign System was introduced commercially in AAO
annual meeting in June 1999.
 It was first described in a peer reviewed publication in 2000.
 Over 70% of all U.S. and Canadian orthodontists have been
certified to use the Invisalign System.
30

 The technology behind Invisalign is cutting-edge, but the
idea of using a series of appliances to move teeth is not
new to orthodontics.
 In 1945, Dr. Kesling first described the concept of moving
teeth using a series of planned, individual stages.
 He realized that the lab requirements would be significant,
and could not envision a practical way to make the idea a
reality.
 Kesling did have the foresight to state that technology
would one day be available to make such treatment
possible.
 With the advent of the computer age, Align Technology
has developed Kesling's vision into a practical method of
orthodontic treatment.
31

32
Predictability of Successful Orthodontic Treatment Using Invisalign
Robert Boyd, DDS Med, Professor and Chairman
Department of Orthodontics, School of Dentistry, University of the Pacific

OVERVIEW
PVS impressions, waxbite,
radiographs, photos
CT scan is made of
impressions to produce a
virtual model
TREAT II software used to
simulate the teeth
movement
ClinCheck® allows Orthodontist
to reviews, modify, and approve
the treatment plan
Stereolithography
to build precise
molds of teeth at
each stage
Individualized, custom-
created clear aligners are
made from these models
33

34
Predictability of Successful Orthodontic Treatment Using Invisalign
Robert Boyd, DDS Med, Professor and Chairman
Department of Orthodontics, School of Dentistry, University of the Pacific

DIAGNOSIS & TREATMENT
PLANNING
 Patient selection criteria:
 Fully erupted permanent teeth,
 Growth has minimal or no effect on treatment (ie.,
late adolescents and adults),
 Mild spacing (1-3 mm), moderate spacing (4-6
mm),
 Mild crowding (1-3 mm), moderate crowding (4-6
mm),
 Narrow arches that are dental in origin (4-6 mm),
 Relapse
35

Space
closure
Movements
after IPR
Dental
expansion
Flaring
Distalization
Extrusion /
Intrusion
TOOTH MOVEMENTS
POSSIBLE
36

Crowding /
Spacing >
5mm
Skeletal AP
Discrepancies
CR-CO
Discrepancies
Severely
Rotated Teeth
> 20o
Open Bites
(anterior &
posterior)
DIFFICULT TO TREAT
MALOCCLUSIONS
37

Extrusion
Severely
Tipped Teeth >
45o
Teeth with
Short Clinical
Crowns
Multiple Missing
Teeth Arches
Closure of
Bicuspid
Extraction
Spaces
DIFFICULT TO TREAT
MALOCCLUSIONS
38

 Although some aspects of malocclusions are difficult to
handle with Invisalign, this does not preclude the use of
Invisalign completely, since there is an option to
undertake completely, combination treatment.
 Orthodontic problems not expected to become
appropriate for the Invisalign System include skeletal
expansion, patients with significant temporomandibular
joint pathology, and tooth impaction/forced eruption
problems.
39

FABRICATION OF
ALIGNERS
1.
• Select a Case and Treatment Goal
2.
• Submit Case
3.
• Align Technology procedure
4.
• Treatment finalization with the ClinCheck® software
5.
• Making aligners
40

1. Case Selection Criteria
Esthetic concern - is a significant factor for adult patients who
prefer Invisalign.
Patients with short dental roots may be better candidates for
clear aligners than for fixed appliances.
Anterior and posterior dental crossbites are also effectively
treated with clear aligners because of their disclusion effect.
It has recently been shown that presurgical treatment
involving clear aligners in combination with fixed appliances
can be effective in patients requiring complex orthognathic
surgery with corrections in all three planes of space.
Boyd, JCO 2007
41

Clear aligners may also be a good choice for patients with
mild anterior open bite. The double thickness of the clear
plastic appliances on the occlusal surfaces, in combination
with the patient's own force of mastication, exerts an
intrusive force on the posterior teeth, slightly closing the bite.
Invisalign is indicated for patients with mild to moderate
crowding (1-6 mm), mild to moderate spacing (1-6 mm).
Boyd, JCO 2007
42

2. Submitting the Case
 Complete an Invisalign System diagnosis
treatment planning form specifying movements
one wishes to make over the course of
treatment as well as the desired final
occlusion.
 Submit copies of all diagnostic records and
treatment plans for review and approval by
Align Technology orthodontists.
43

 There are four required records that need to
be taken before submitting the case:
 impressions,
 bite registration,
 photographs, and
 x-rays, prescription form
44

2.1. Impressions
Impressions must always be taken using PVS
(polyvinylsiloxane) impression material.
Both upper & lower impressions are required
even if treating one arch.
It is recommended to cleanly capture the distal
aspect of the second molars.
Periodontal and pre-orthodontic restorations
should be completed prior to impression.
45

Align Technology’s trays are used
Designed to be read during scan
Tray sizes come in S, M, L, XL
Trays can be adjusted with acrylic bur or heat source
Tray adhesive is not needed if putty is used properly with
Align Technology trays
All bridges and/or undercuts are blocked out if necessary
ALIGN TRAYS
48

 The most common shortcoming
with impressions is failure to
capture sufficient detail of the distal
of the second molars.
 A common error is multiple areas
of “drag” near the gingival margin.
These are triangular voids caused
by seating the tray with impression
material too quickly into the mouth
and not allowing sufficient time for
the material to flow around the
gingival margins.
COMMON ERRORS IN IMPRESSION MAKING
51

 A third common error involves surface or immediate
subsurface air bubbles in the impression.
 The last common error is seating the impression tray
too far from or too close to the buccal or lingual tooth
surface so that the impression material bleeds through
to the impression tray and the material becomes too
thin to be resolved on the CT image.
52

2.2. Bite Registration
 Material is directly injected onto the patient’s occlusal
surfaces. A layer of about 5 mm of bite material is
usually sufficient.
 Patient is gently guided to close into desired position.
 After 1 minute from the start of mixing, the material may
be removed from the patient’s mouth and carefully the
bite registration is released from the teeth.
 Residual material in undercut areas is checked.
 Registration bite is rinsed under cold water and air blow
dried.
53

2.3. Photographs
 All the extraoral & intraoral photographs are taken.
 One full-mouth series x-ray and/or panoramic x-
ray is required.
 To specify the specific goals of the treatment and
to suggest the specific path of tooth movements
required to achieve the desired corrections.
2.4. Radiographs
2.5. Prescription Form
54

3. Align Technology
Procedure
 The patient's polyvinyl siloxane (PVS) impressions and
bite registration must first be converted into dimensionally
accurate 3-dimensional electronic study models by means
of a Computer Aided Tomography (CAT) scan.
 To create a virtual dental model directly from the
impression with CT scanning, the impression is mounted
on a platform that rotates in front of an amorphous silicon
x-ray sensor.
 Hundreds of digital radiographs of the impression are
captured as it rotates 360o.
55

 CT – generated radiographs.
 These radiographs are converted
to images called sinograms.
 Slice reconstruction from
sinograms.
56

 A 16 central-processing-unit fiber-optically linked
computing cluster uses the sinograms and a series of
mathematical algorithms to create 116 micron thick
reconstruction slices of the object.
Frames of 116 μm-slice reconstruction from sinogram:
(left to right) initial, early, late, final, and final inverted
57

 These slices are stacked electronically and inverted,
and the resulting surface is smoothened to yield a raw
electronic study model (ie., the virtual study model).
 The maxillary digital model is electronically registered
to the mandibular digital model in centric occlusion
(maximum intercuspation).
3.1. 3-D Virtual Models
58

 Once the virtual models are produced, they are then sent
electronically to Align’s facility in Costa Rica where the raw
electronic models are “detailed” by using software that
simulates standard dental lab procedures, such as bubble
removal, void filling, and gingival-line definition.
 Then the 3D image is accessed by technician who
transforms the raw data into a plan for the manufacture of
custom aligners.
 The process is comprised of 3 phases
 Cutting Process
 Creating the final setup
 Staging process
3.2. The Virtual Setup
59

 Align Technology uses TREAT® software which is a
sophisticated 3D graphics program that gives the
operator great control of tooth position as well as rate of
tooth movement.
 Virtual tools in the form of planar and curved cutters
that are part of the TREAT® software are used to isolate
data for each part tooth within the arch into separate
geometric units.
CUTTING PROCESS
60

 Each crown is painted to
distinguish between the tooth
anatomy and gingival tissue.
Landmarks such as the facial axis
of the clinical crown of each tooth
are identified.
 Now the separated teeth can be
moved as individual units into
arch form. The technician moves
the specific teeth into alignment
creating a final setup which
precisely matches the doctor’s
prescription.
61
CREATING THE FINAL SETUP

 Then the technician reapplies the gingival tissue that
were removed during the cutting process.
62

 The next step in the process is to determine the
number of intermediate stages (and thus the number
of aligners) between the original malocclusion and the
final treatment result.
 The two factors:
 Path of tooth movement
 Velocity at which the teeth are to be moved. The maximum
velocity of tooth movement currently is 0.20 - .25 mm per
tooth per stage
63
STAGING PROCESS

 The greater the distance that the teeth need to be
moved or rotated and the more complicated the
movement path, the greater the number of aligners
needed to treat the patient.
 The number of aligners varies from ten or less for
relatively simple problems to fifty aligners or more in
complicated malocclusions.
64

3.3. ClinCheck® Software
 After the forecast model and treatment sequence
have been generated, this information is sent over
the Internet to the orthodontist, who reviews the
forecast model and sequence by way of the
ClinCheck® software program.
65

 For diagnosis and treatment planning – to evaluate the
need for IPR, expansion, extraction, distalization, or,
proclination
 For verifying that technician has performed
modifications
 As a consultation device to show treatment limits to the
patient
 As a communication tool to email the abbreviated
ClinCheck® to patients and to referring doctors
 For verifying if aligner is tracking
 For evaluating anchorage with the superimposition or
surgical simulation tools
67
USES OF CLINCHECK® SOFTWARE

 The single greatest benefit of ClinCheck ® is its
usefulness as a tool for therapeutic diagnosis.
Although the treatment outcomes cannot be
superimposed, they each can be superimposed on
the pretreatment virtual model for evaluation.
68
SUPERIMPOSITION TOOL

 The group of virtual model manipulation tools located
in the upper left of the screen.
69
VIRTUAL MODEL MANIPULATION TOOLS

 The next tool available is the gallery views, which
allows the orthodontist to view a single model, two
arches simultaneously in separate orientations or a
collage of six separate views.
71
GALLERY VIEWS

 Four navigation buttons that allow the user to move
the model around the screen, zoom in or out overall,
rotate the model or zoom into a specific location by
clicking the mouse on the desired spot.
72
NAVIGATION BUTTONS

 These allow the user to increase or decrease
resolution (lower resolution allows faster computer
operations).
 They also allow one to show or hide the upper model,
attachments, tooth numbers, interproximal reduction
instructions, comments, lower model, virtual pontics,
superimposition, grid tool, overcorrection stages.
73
RESOLUTION AND ILLUSTRATION BUTTONS

 Superimposed on occlusal to check symmetry
74
GRID TOOL

75
INTERPROXIMAL REDUCTION RECOMMENDATIONS

77
Central Incisor Lateral Incisor Canine
Mesial Distal Mesial Distal Mesial Distal
Maxillary 0.3 0.3 0.3 0.3 0.3 0.6
Mandibular 0.2 0.2 0.2 0.2 0.2 0.3
1st Premolar 2nd Premolar 1st Molar
Mesial Distal Mesial Distal Mesial Distal
Maxillary 0.6 0.6 0.6 0.6 0.6 0.6
Mandibular 0.6 0.6 0.6 0.6 0.6 0.6
Minimum amount of enamel (mm) that can be removed with IPR in the
anterior area
Minimum amount of enamel (mm) that can be removed with IPR in the
posterior area

 Comments are
displayed in two
colors, one
designating the
comments entered
by the orthodontist
and the other
designating
comments entered
by the TREAT
technician.
78
COMMENTS SECTION

 At the ADA’s 146th Annual Session in Philadelphia, Align
Technology launched ClinCheck® 2.0, the latest version of
Align's software application for Invisalign treatment.
 This latest version of ClinCheck® is designed to improve
usability and streamline ClinCheck® review and approvals
for Invisalign doctors. ClinCheck® 2.0 was designed to
provide greater ease-of-use and streamline treatment
planning and ClinCheck® review for doctors.
79
CASE ACCEPTANCE VERIFICATION

 ClinCheck® software provides viewing and navigation
tools that greatly facilitate treatment planning, and
ultimately allows for better clinical decisions. The
ability of ClinCheck® to allow diagnostic setups,
treatment planning, and evaluations makes it a
valuable tool for clinician.
 After orthodontist’s approval, Align Technology uses
these graphical images combined with CAD/CAM
technology to fabricate aligners.
81

3.4. ClinAdvisorTM Software
 On October 17, 2006, Align also announced the rollout
of ClinAdvisorTM, a new suite of software tools designed
to make Invisalign case selection, submission and
review processes more efficient for doctors.
 ClinAdvisorTM simplifies case selection by helping
doctors identify the skills necessary for a specific case.
A complexity rating system categorizes treatment plans
as "Easy," "Moderate" or "Advanced" and lists expected
treatment characteristics and potentially challenging
movements for each option.
82

 Doctors have the option of choosing from four
separate treatment goals for more efficient treatment
planning:
 Pre-Restorative: helps prepare teeth for restorative
procedures
 Esthetic: aligns the upper and lower anterior teeth
 Anterior Function Improvement: improves the canine
relationship in addition to esthetic alignment
 Optimal Setup: addresses all aspects of malocclusion
83

STEREOLITHOGRAPHY
 An orthodontic product like Invisalign requires from 6 to 40
sequential appliances per arch; manual fabrication of
these many appliances would be prohibitively expensive,
and it would be difficult to maintain the required accuracy.
 Instead, Align Technology uses stereolithography
technology to create its reference models.
 Stereolithography (SLA) is a rapid prototyping process by
which a product is created using an Ultra-violet (UV)
curable liquid resin polymer and advanced laser
technology.
 Each stage of treatment is converted into a physical
model with a machine called a stereolithography
apparatus (SLA).
84

 A stereolithography machine uses a computer controlled
machine laser to cure a photo-sensitive thermoplastic resin,
layer by layer, to create a model replicating each stage of
treatment for each patient.
 To begin with, one has to create a CAD file of a 3D virtual
model. From here, the model is imported into the SLA
software program where it is supported as needed. (These
supports generally occur in areas with undercuts and
overhangs.) Once all proper supports are in place, the file is
ready to be "sliced".
 The "slicing" process is how the CAD file is translated to the
Stereolithography machine. At this point the model is
"sliced" into layers and the “sliced” model is sent to the SLA
machine.
85

 During the building procedure, the laser beam is focused by
means of an optical system, directly on the surface of the vat
containing the liquid resin.
 The laser beam starts a polymerization reaction creating a
reaction solid layer. Once the layer is drawn, a sweeper
drags across the initial surface to smoothen it out and
prepare it for the next layer.
 The elevator is lowered to a thickness equal to that of the
photopolymer solidified and subsequently a thin layer of resin
covers the already built structure using a highly precise
recovering system.
 The process starts again with a further solidification of the
subsequent layer, which firmly sticks onto the previous
section and the process proceeds until the complete
production of the 3D virtual model dictated by the original
CAD file.
86

87
Align Technology uses the latest Stereolithography Apparatus SLA
7000 system from 3D Systems

88
These SLA resin models are loaded into an automated aligner forming
system that heats, forms, and laser marks plastic sheets over each
model

89
These parts are transported on a conveyor belt to a robotic arm that
loads each part into an automated cutting machine for trimming where
they are trimmed to within ½ mm of gingival margin for patient’s
optimal comfort and minimal visibility

90
Automation enables aligner
trimming to be completed in less
than 30 seconds. Once trimmed, the
part is ejected, and the aligner is
separated, laser-etched with the
patients initials, case number,
aligner number, and arch (upper or
lower) then polished, disinfected,
and packaged for shipment to the
customer
Box of aligners and attachment template for
one patient. A patient start-up and care kit
accompanies this

ALIGNER MATERIAL
 Invisalign appliances are composed of polyurethane
with added methylene diphenyl diisocyanate and 1,6
hexanediol.
 The diphenyl structure provides stability and sufficient
reactivity to form a polymer free of byproducts.
 Polyurethane, the basic constituent polymeric
component of Invisalign aligners, is not an inert material
and is affected by heat, moisture, and prolonged
contact with enzymes.
91

CONTENTS
• Introduction
• History of Invisalign
• Overview of the Invisalign System
• Understanding the Invisalign System
• Diagnosis and Treatment Planning
• Polyvinyl Siloxane (PVS) Impressions
• Cutting process, creating the Final Setup
• Staging Process
• ClinCheck® Software
• ClinAdvisorTM
95

 Stereolithography process
 Aligner Materials
 Biomechanics
 Attachments
 Orthodontic Treatment with Invisalign Appliance
 Finishing with Invisalign
 Retention and Aligner Cleaning
 Why Invisalign?
 Advantages
 Limitations
 Summary & Conclusions
96

BIOMECHANICS
 With an aligner, the plastic encapsulates the tooth and in
doing so must provide both retention and activation to
move the teeth.
 In general the natural undercuts of the teeth provide the
retention and the active component to move teeth by the
elastic deformation of the aligner.
 This is important for two reasons:
 First, the aligner elastic deformation cannot be so great as to
overcome the retention forces;
 And second, there are certain directions in which aligner has a
greater inherent ability to undergo elastic deformation.
 The total desired movement is then subdivided in such a
way that the aligners remain within this range of elastic
deformation and a sequence of aligners is made to
accomplish the entire desired movement.
97

ATTACHMENTS
 Traditional orthodontic appliance systems are designed
around components that transmit forces (ie, wires) and
elements that apply these forces (ie, brackets) to the
teeth. The Invisalign System also follows this design:
 It directs force application to the teeth through
intermediary components — aligners and attachments,
where aligners are analogous to wires, attachments are
equivalent to brackets.
98

99
The key is to provide a ledge for the aligner to grip that is perpendicular to the
direction of displacement and of sufficient size to provide enough surface
area to offset the force delivered. Another simple rule of thumb is to place the
attachment far enough away from the gingival margin that the aligner will not
spread or stretch and slip off the attachment.

 There are three fundamental categories of
attachments:
 Those that assist movements,
 Those that augment appliance retention, and
 Those that provide or support auxiliary functions.
 Purpose:
 Help in retaining the aligner
 To provide a surface upon which additional force
can be exerted and, in doing so, to create a
moment arm for biomechanical advantage
100

All three act as force transmitters; however, they do so in
different ways.
The movement attachments are intended specifically to
induce or aid the repositioning of the teeth to which they are
bonded.
The retention attachments typically promote movements in
teeth other than the one to which the attachment is affixed;
retention attachments serve as relatively fixed points against
which the aligner can act.
The auxiliary attachments may be placed to act on the teeth
they are attached to, on other teeth in the arch, or in
conjunction with other components (eg, elastics) — on teeth
in the opposing arch.
101

 The attachments are created by bonding composite on
the target teeth using a special plastic template or the
treatment Aligners
102

1. Inject Compose-It
microhybrid flowable
composite into the
template (A). The viscosity
of this material is ideal for
eliminating voids.
2. After tapping the template
with an instrument to even
out the surface (B), light-
cure the composite.
103
Paul A. Rocke, JCO 2008

3. Apply the bonding liquid conservatively to the attachment and
the tooth.
4. Place the template in the mouth, holding the attachment
against the tooth with a ligature director. If the reservoir is
slightly underfilled, the hard attachment can be pushed
against the tooth for proper adaptation. Light-cure the liquid
interface. Any residual adhesive, which should be minimal,
can be cleaned up with finishing burs.
5. Create a gingival slope for easier removal of the aligners.
104

Ellipsoid Attachment
 The first attachments were ellipsoid in shape and
looked like a hemisected football bonded to the tooth
surface.
 Ellipsoid attachments are applied when an intrusion,
extrusion, or rotation is intended for the underlying
tooth.
105

Rectangular Curved Root Tipper
(CRT) Attachment
 Provide a straight surface against which the aligner
can apply force.
 The vertically oriented CRT attachments are most
effective for root tipping and root paralleling, whereas
horizontally oriented ones are most effective for
vertical and root torquing movements.
106

 Modifications:
 Beveled rectangular (BR) attachments; and
 Double horizontal rectangular (DHR) attachments
 Inverted T attachments
109

Controlling Torque
110
A net force of 40 g (base level force of an aligner after 48 hours) intended to
move the tooth lingually would require a moment of 320 to 400 g-mm (M/F
ratio 8-10) for bodily movement or greater than 400 gmm (F/M ratio less than
10) for lingual root movement

111
Improper attachment design or placement allows the delivery of only 280 g-
mm moment in conjunction with 40 g force, resulting in controlled lingual
crown tipping

113
In order to facilitate greater ease of insertion and removal, as well as
eliminate the all-or-none situation, the beveled attachment was developed by
rotating a portion of the rectangular attachment virtually into the tooth surface

 An alternative to attachments that help facilitate torque
control is the power ridge.
 Power ridges are engineered corrugations placed at
specific locations to enhance the undercut near the
gingival margin of teeth undergoing torquing
movements.
 The ridges function in two ways:
 The first is to stiffen the gingival third of the aligner to
make it more resilient
 The other is to provide additional force as close to the
gingival margin as possible to increase the effective
moment arm of the aligner
 Advantage - attachments need not be placed or
removed, and they are more aesthetically acceptable to
the patient.
114

 An idea dating back to the late 1800’s was to place an
attachment on the gingival aspect of a bracket extending
toward the center of resistance in an attempt to decrease
the amount of tipping when teeth are moved mesiodistally.
 These gingival extensions are often described as power
arms.
 Power arms have been added to the force system with
Invisalign in an attempt to alter the force–moment system.
 In theory, the addition of a power arm auxiliary
accomplishes two things.
 First, it moves the application of force closer to the center of
resistance.
 Second, it creates a secondary moment due to pressure
against the distal of the aligner.
119

ORTHO T/T WITH
INVISALIGN
 The initial treatment visit involves inserting the first
appliance of the series.
 Some patients require attachments to their teeth to
facilitate certain movements such as extrusion,
extraction space closure or rotation of lower premolars.
 Aligners typically are worn for 24 hours daily; the
patient is advised to remove them only while eating,
drinking, brushing and flossing.
 Aligners are commonly worn for 7 to 14 days, with
progress being patient and movement specific.
121

Protocol for Changing Aligners
 Recently Align developed a more rigid standard for
magnitude of tooth movement which now requires two
weeks for each Aligner (24 hours daily).
 May be more than two weeks per aligner in extraction cases
with bodily movement, for patients who wear Aligners less
than 22 hours/day, or if problems occur with Aligner seating
completely.
 Patients should keep the last 3 to 4 Aligners in order to go
back to a stage that fits if seating problems occur.
 If the patient does not wear an aligner for more than 2-3
weeks, new PVS impressions and rescanning may be
necessary.
 If patient loses an Aligner, they should try the next aligner
(wear for one month) or use the previous aligner.
122

TOOTH MOVEMENT
 The biomechanics involved with this appliance differ from
those described for traditional fixed appliances because of
the greater surface area of force application to the tooth.
 Preliminary finite element studies show that forces are
dissipated over the majority of the crown, which tends to
distribute the forces over more of the root surface than
with fixed appliances.
 Bodily tooth movement is possible, particularly if the entire
crown is tightly held with no space between the appliance
and the tooth.
 The activation in the appliance can then move the tooth
bodily because the tooth is a rigid body, and at least two
points of contact are in play.
123

 The forces involved for the 0.02 mm activations are
most likely of a light, continuous nature due to the
elastic properties of the appliance and the small
magnitude of individual activation at each stage.
 The effects of tooth movement can only be described
clinically at this point because of the lack of scientific
data on biomechanical principles involved with tooth
movement created by the Invisalign appliance.
124

Predictability of Treatment
125
Space closure
2-4 mm of
buccal or labial
expansion
Stripping and
incisor rotations
Lower incisor
extractions
Deep overbite
Cross-bite
correction (non-
skeletal)
HIGHLY PREDICTABLE

126
Root torquing
Distalizing
posterior teeth up
to 3-4 mm
Use in
periodontally
compromised
patients
Mature teenagers
(>14 years) with
fully erupted teeth
Closure of mild
open bite with
retraction of
incisors (non-Xn)
Closure of
moderate open
bite with incisor
retraction (Xn)
MODERATELY
PREDICTABLE

127
Severe rotations
of premolars and
lower canines
Extrusion with no
retraction
Mesial movement
of posterior teeth
(pre-molar
extractions)
Short clinical
crowns (partially
erupted teeth)
Less mature
teenagers
LESS PREDICTABLE

1. Rotations
 The addition of attachments on the labial or lingual
surfaces (or both) is required for some teeth to be
rotated.
 If the rotation is more than 45°, fixed appliances may
be employed initially to reduce the magnitude of the
rotation.
 Incisors usually rotate more easily with this appliance
with no need for attachments.
128

129
Rotational auxiliariesRotation beveled attachment

2. Anterior Intrusion
 For intrusions, the attachments add retention of the
appliance on the teeth adjacent to the tooth to be
intruded.
130

3. Anterior Extrusion
 Extrusion has proven to be one
of the most difficult movements to
achieve with this appliance.
 Aligner must completely cover
attachment and have 2 mm
space gingival to attachment with
aligner well adapted.
 Extrude teeth with an elastic from
a button on facial of tooth and
lingual of aligner.
 Must have slight interproximal
space; check with floss space
(stripping as necessary).
131

 Aligner itself is incapable of elastic deformation in the
direction needed for effective rotational movement, the
aligner cannot stretch within the plastic itself so an elastic
deformation in the direction needed for extrusion is not
possible.
 Use the gingivally beveled attachment to provide a longer
surface that can be elastically deformed and provide an
extrusive force on the tooth.
 In some cases a button bonded to the tooth together with
an elastic will assist with the extrusion.
132

4. Lower
Incisor
Extraction
133
5. Bicuspid
Extraction

6. Class II Correction
 Consider intra-arch movement using other teeth as
anchorage to achieve inter-arch corrections (i.e.,
distalization of molars in a class II).
 It is also possible to place inter-arch elastics on aligners
by cementing hooks to aligners (purchase kit from Align
Tech) to correct mild A-P problems but retention of
aligners when wearing elastics is a limiting factor.
 Toe nail clippers can be used to cut slits in the aligners for
elastic placement
134

7. Midline Discrepancy
 Midlines can be corrected by asymmetric Class II and
class III elastics attached to the teeth on clear
buttons.
137

PROBLEMS DURING T/T
 Any discrepancy between the actual clinical
appearance of the occlusion and the virtual treatment
sequence program indicates that treatment should be
fully reviewed.
 Possible reasons for this discrepancy are that the
patient has lost, or is not wearing their appliances for
a sufficient time (at least 20 hours per day), or that
the appliances have not been fully seated.
139

 This can usually be corrected by remaining in a
specific appliance for more than 20 hours per day for
2 weeks or more to allow the appliance to recapture
tooth position.
 For maximum treatment efficiency, it should be
stressed to patients at the outset that if they lose an
appliance, they should progress to the next stage
only if that stage seats fully, or return to the previous
stage.
 For this reason, appliances should not be discarded
until the patients are at least two stages ahead.
140

 If the patient's occlusion cannot be recaptured by an
appliance, it may be useful to use the computer
program to identify which stage visually matches the
clinical appearance most closely, and return to that
particular stage.
 If this fails, the patient should be placed in clear,
overlay retainers and another PVS impression taken
for rescanning, with a new treatment plan devised.
141

ALIGNER FIT
 The aligner must fully “cup” the
tooth crown at all times to prevent
the occurrence of aligner
length/arch length discrepancy.
 If there is a problem with the
aligner fit, then the shortened
aligner will force the teeth into
segmental crowding. The ill-fitting
short aligner will apply significant
force (as the patient bites into the
tray to seat it better) at the distal
of the terminal molar.
142

 The iatrogenic crowding problem in the anterior
region, especially with triangular teeth, if vertical
traction is lost, it will be very difficult to avoid the
consequent development of tight interproximal
contacts and crowding.
144

 Thus, it should be
understood that poor
vertical fit of the aligner
promotes mesiodistal
problems.
 The aligner can be fully
seated with the help of
Chewies made of
polyurethane foam.
145

FINISHING WITH INVISALIGN
 Finishing is a critical part of orthodontic treatment. With
Invisalign, there are several factors that play an important
role that can affect the anticipated results of treatment.
 Because of the overlay design of the appliance, the
anatomy of the tooth plays an important role and can
cause minor alignment discrepancies.
 Variations in tooth shape such as irregular facial surfaces,
unusual crown shapes, and unfavorable crown shapes,
such as round teeth, require additional Aligners
(Refinement aligners) and also use of auxiliaries such as
detailing pliers to achieve the desired alignment.
146

Monitoring and Finishing with
Auxiliary Techniques
 An alternative to use refinement Aligners is the use of
“Invisa-Shims”.
 These are small composite bumps that the doctor
places on the portion of the tooth that is still rotated.
 Invisa-Shims can also be used for small in-out
adjustments.
 Buccal and lingual attachment on round teeth to
obtain couple.
147

 One can use the crimping pliers sold by Align
Technology to introduce pressure points in the
existing Aligner series and also to increase retention
by placing dimples in the interproximal undercuts.
 Detailing pliers have been shown to be successful for
movements at the end of the treatment that require
in/out movements and minor incisor rotations.
148

 The tip of the Detail Plier
features a unique design
that can create pressure
points on heating.
 To create a pressure
point, the tip is oriented
over the desired area of
the aligner and gently
squeezed.
149

OVERCORRECTION
 The procedure is recommended during the
refinement series. Over corrections may be
necessary for the following:
 Rotations
 Bite depth (deep or open)
 Torque
 Extraction spaces
150

RETENTION
 Usually, the final appliance or a thicker version - 0.04
inch, ie. Exceed-40 [EX40] of it, is worn full full-time
for 6 months.
 It is seen that more than 85% of patients have
posterior bite.
 To close posterior bite cut aligners distal to occlusal
contacts (usually 1st or 2nd premolars) and let it
settle for 2-4 weeks.
 This is followed by night-time wear indefinitely.
151

ALIGNER CLEANING
 Brush with toothbrush (powered better)
 Soak for 5 minutes with new Align dissolving
tablets or 3-4 drops of Clorox (both sodium
hypochlorite) in lukewarm water.
 Align also sells a sonic vibrating cleaning unit for
approximately $50.
152

WHY INVISALIGN..?
 Increased awareness for esthetics
 Patients are more aware of plaque associated
problems with fixed appliances
 Many patients do not want fixed appliances
(especially adults and re-treatments)
 Appreciation of the benefits of technology (especially
teenagers and young adults). Most orthodontic
patients are computer literate and appreciate how
technology can enhance treatment
 Invisalign website generates many referrals
 Alternatives to porcelain veneers
153

1. Improves Oral Health
Healthier Gums
 Clinical studies have shown that gum health may
improve with the use of Invisalign during orthodontic
treatment.
 Clements et al (AJO 2003) measured the response
of the periodontal tissues with the papillary bleeding
and pocket depth scores and found that these
measures improved during Invisalign treatment - not
just after treatment as they do with fixed appliances.
154

2. Easier Cleaning
 Unlike traditional orthodontics or braces, Invisalign
has no metal bands or wires to trap food and plaque.
 Maintaining a good oral hygiene program will also
reduce chances of plaque buildup, tooth decay and
periodontal disease.
155

3. Materials and Supplies Cost
 Infection control (sterilization) 12% much less
 Instruments 4% much less
 Wires, brackets & bands 18-20% rarely needed
 Impression trays & material 1-2% higher
 Lab fees (study models, retainers, etc) 4-5%
significantly higher
156

4. Total Treatment Time
 Treatment duration similar to fixed appliance
treatment
 Similar number of patient visits but much shorter
chair time
 Doctor and assistant time much less
 working patients appreciate less chair time and ‘mouth
open time’
 shorter visits easier to schedule at preferred times
157

5. Patient Discomfort & Speech
Effects
 Subjective evaluation of patient discomfort during
treatment has demonstrated generally less discomfort
with Invisalign than seen with traditional fixed
appliances.
 This is most likely because the magnitude of the tooth
movements are only 0.2 mm, on average. In addition,
speech problems have rarely been a problem,
particularly after the first week of treatment.
158

6. Patient Compliance
 Usually excellent because of slight posterior open
bite.
 The open bite is caused by slight posterior tooth
intrusion that occurs 3-4 weeks after treatment starts.
It results in heavier contact on anterior teeth when
patients are not wearing aligners.
 Patients generally prefer the occlusal pattern of the
more even contacts between their teeth when the
appliances are in place, rather than the heavier
anterior contact when the appliances are removed.
 ‘Splint effect’ is also seen – for MPDS treatment.
159

 A classification system establishing the level of
complexity of Invisalign treatment could help the
orthodontist decide whether to treat a given patient
with Invisalign or with fixed appliance.
 Such a system could also facilitate Invisalign
treatment planning and help determine appropriate
fees.
160

Level 1: “Invisalign Express; 10 or fewer aligners needed
 Spacing: minor anterior
 Crowding: minor in/out movements, expansion, minor
interproximal reduction (IPR)
 Minimal rotations, involving incisors only (<10°)
 No vertical movements
 Class I molar/canine occlusion
 No extractions
161

Level 2: 10-20 aligners needed
 Space closure: moderate anterior/posterior
 Crowding: moderate in/out movements, buccal expansion,
minor IPR
 Minor rotations, including canines/premolars (5-15°)
 Minimal extrusive/intrusive vertical movements (1-2mm)
 No extractions
162

Level 3: 15-30 aligners needed
 Crowding: buccal expansion, moderate-to extensive IPR
 Moderate rotations, including canines/premolars (>15°)
 Moderate vertical movements (3-4mm)
 No extractions
 Molar uprighting
163

Level 4: More than 30 aligners needed
 Class II or III occlusion (including end-on)
 Crowding requiring extractions (including incisors)
 Substantial vertical movements (more than 4mm)
 Crossbite (anterior/posterior)
 Presurgical setup
 Substantial root movement: torquing, root preparation for
restorative procedures
164

INVISALIGN TEEN
 It soon became apparent that
there were certain benefits in
being able to treat the late
mixed dentition with aligners
as well.
 Eruption tabs are used to
prevent supereruption of
unerupted second molars.
 Two different types of
chemical indicators that turn
from dark blue to clear as the
aligners are worn.
165

ADVANTAGES
 Esthetic - rarely noticed even at close distance – attracts
additional patients
 Removable - unlike fixed appliance, one can eat and drink
what one wants during treatment
 Comfortable - no metal brackets or wires to cause mouth
irritation
 Better oral hygiene than fixed appliance
 Simplicity of care
 Possible to treat “brittle” periodontal problems
 No decalcification of teeth (WSL)
 3D control of tooth movement
 Teeth can be bleached with the appliance at the beginning
and during treatment
166

 Shorter appointments
 Decreased doctor & auxiliary time
 Enables the clinician to treat different parts of the arch in
different sequences
 Decreased allergic response (no metal or latex) -
aligners are made from polyvinyl material
 Controlled overcorrection possible
 Less damage to existing restorative dentistry (especially
porcelain) and tooth structure than fixed appliances
 Retention facilitated (does not require a new patient
experience)
 Ideal for retreatment
 Decreased occlusal abrasion from para-functional habits
during treatment
167

 Disarticulation of the teeth may be advantageous for
patients with TMJ problems
 Technically much easier than lingual appliances
 Ability to present case to patient with final result prior to
treatment
 Ability to review treatment progress during treatment to
increase compliance
 Provides a record of projected results which enables
future review
 Disappearing patients have very minimal potential for
periodontal or caries damage
168

LIMITATIONS
 Primary among them is compliance. Because the
aligners are removable, the orthodontist must rely on the
patient’s motivation and dependability to achieve the
desired results. The removability of Invisalign is an
advantage to the patient but not to the clinician. So, it’s
biggest advantage becomes its biggest disadvantage.
 All permanent teeth should be fully erupted for treatment
using this appliance, as it is difficult to achieve retention
of the appliance on short clinical crowns. The treatment
procedures do not allow for continued eruption of teeth,
or significant dental arch changes during growth that
may occur during the mixed dentition phase.
170

 There is currently no capability to incorporate basal
orthopedic change with this appliance system, thus
restricting it to malocclusions requiring purely dental
movement.
 Due to the fact that the surface anatomy of the teeth
cannot undergo change during treatment as it will affect
the fit of aligners, major restorative work should be
performed before the commencement of treatment.
 Lack of operator control - Unlike fixed or other types of
removable appliances, the treatment plan cannot be
changed once the appliance series has begun. If
change in treatment goals is desired, the current series
may be completed and a new plan and appliances
made, or the current series may be stopped. Either
scenario, however, will lead to increased cost for
treatment and increased treatment time.
171

 Inability to integrate hard and soft tissues of the head
into the computer treatment. Thus, the clinician has no
direct indication of where teeth are in relation to basal
bone or in relation to the lips or other soft tissues of the
head.
 Generally, the cost to patients is greater for this
appliance than fixed appliances. They typically cost
$3,000 to $9,000 (average is about $5000) depending
on the number of aligners needed for treatment. This is
due to the cost of the technology used to scan the
models and to develop a virtual treatment, in addition to
manufacturing, packaging, and shipping costs for as
many as 40 to 80 appliances. However, doctor and chair
time, instrument and sterilization costs are significantly
lower when compared with other esthetic orthodontic
options, such as clear or lingual appliances.
172

 Currently, only crown position is displayed on the
computer program. Because the clinical appearance of
crown inclination is not always predictive of root
inclination, the potential exists for a virtual treatment to
be approved, in which crown position appears optimal
but root position is not ideal.
 However, upcoming advances in the design of patient
imaging and software programs make it possible to
include virtual roots onto the software application.
173

1. Compliance
2. Erupted permanent teeth
3. No orthopedic changes
4. Restorations to be performed before
5. Lack of operator control
6. Non-integration of hard & soft tissues with basal bone
7. Increased cost
8. Only crown position is displayed on the computer program
174

SUMMARY & CONCLUSIONS
 With Invisalign, a new system for orthodontic tooth
movement using the established methods for minor
correction to achieve greater magnitudes of correction has
been introduced.
 The major advantage of the system is the esthetic,
hygienic, low discomfort and removable nature of the
appliance.
 There are currently limitations to this appliance in terms of
case selection, increased cost, experience required for
computer treatment planning, difficulty obtaining certain
tooth movements, and the lack of potential in cases
involving mixed dentition or impacted teeth.
185

 One needs to understand that Invisalign is only an
appliance, and the technique for working with it is
continually being developed. Refinement, adjustment at
each appointment, and rebooting are all part of the
technique, and all depend on the orthodontist's skill – just
as with a patient in any fixed appliance.
 Many new aspects of treatment techniques must be
learned about Invisalign to be proficient with treatment to
full malocclusions.
 Like any other appliance, Invisalign is one of its kind of
appliance with its own advantages and disadvantages.
 Ultimately, much will depend on the research and
development that can be generated to improve aligner
control over tooth movement, and our understanding of
treatment and ability to plan prospectively.
186

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