2. CONTENTS
• Introduction
• History
• Classification
• Benefits
• Limitation
• Steps in clear aligner
• Scanning and digitization
• Digital treatment planning
• Clincheck—an overview
• 3D printing
• Materials
• In house clear aligner
• Comparison between edge wise and clear aligner
• Generations of aligners
• Attachment design in the invisalign system
• Power ridges and pressure areas in the invisalign
system
• Biomechanics in clear aligner
• Root control ,rotation correction, extrusion In the
invisalign system
• Class II correction in Invisalign
• Open bite,Deep bite
• Clear aligner vs orthognathic sugery
• Auxiliaries and the invisalign system
• Invisalign teen
• Articles
• Conclusion
• References
2
3. INTRODUCTION
Majority of adult patients seek orthodontic treatment- to enhance facial
aesthetics.
• Buccal fixed metallic appliances are efficient treatment systems, the
reluctance of their use is mainly due to metal look, poor aesthetics and
fear of pain.
• Clear aligners offer an excellent alternative to unaesthetic orthodontic
treatment with labial fixed appliances.
3
4. HISTORY OF ALIGNERS
• The theory of using an aligner to straighten teeth was first postulated
in the 1945.
• Dr.Harold D. Kesling first advocated a rubber appliance for moving
teeth.
4
5. • Henry Nahoum (1950) developed the vaccum formed dental contour
appliance often termed as the “invisibles”.
• In 1964, Nahoum published a thorough article describing his vacuum
formed dental contour appliance.
• Ponitz (1971) introduced an ‘Invisible Retainer,’ which used Kesling’s
idea of pre-positioning teeth on a master study model.
5
6. • 1994-Sheridan et al. introduced the technique of interproximal tooth
reduction (IPR) for resolution of the lower incisor crowding and
alignment of teeth with the help of labio-lingual clear plastic retainer. His
appliance is named ‘Essix appliance’.
6
7. • 1995-further developed by Hilliard and Sheridan with a series of
special thermoforming pliers designed to enhance specific
movements.
• The laboratory construction always been tedious and limited the
widespread adoption of removable aligner techniques.
7
8. Invisalign
• Developed by two graduate business students at Stanford University in
1997, Kelsey Wirth and Zia Chishti.
• Used CAD-CAM to mass produce aligners that would be capable of
treating a broader range of malocclusions .
8
9. • Robert Boyd, chairman of the Department of Orthodontics, University
of the Pacific.
• He assisted in this endeavor by being a consultant.
• Align technologies received FDA clearance to market Invisalign in
august 1998, and began commercial operations in July 1999.
9
10. In 2005, a competitor emerged -OrthoClear® a clear aligner system
developed Zia Chishti.
It was withdrawn a year later due to lawsuits alleging patent infringement.
Many practicing clear aligner users suffered as a result, one of whom was
Dr. Willis Pumphrey whose 400 patients were stranded mid-treatment.
He responded by developing ClearCorrect-2006
10
11. • Clear aligners can be categorized into
four basic categories.
• First category- positioners or guide.
• This category includes the original
Allesee Orthodontic Appliances (AOA)
positioner described by Kesling.
11
Product Name
Orthodontics Positioner
Nite-Guide; Occlus-o-Guide;Preformed
positioner
Myobrace i-3, i-2, Myobrace
12. • The second category- thermoformed
appliances(Essix Retainers)and removable
appliances referred to as spring aligners.
• Can be fabricated in the orthodontist’s office
or sent to a commercial laboratory.
12
Aligners Currently Available: Activation
Aligners and Appliances
MTM Clear Aligner
Straight ‘N’ Clear Cosmetic Correctors
Inman Aligner
Clear Aligner
13. • The third category-aligners that are
fabricated from models that have had teeth
cut out and manually moved to the correct
position.
• If done in a series of models, an aligner can
be fabricated from each model. These
appliances can be used for minor
movement of upper and lower anterior
teeth and usually consist of three to five
aligners.
13
Aligners Currently Available: Teeth Manually
Reset
Clear Image Aligners
Red White Blue Simpli
Originator Clear Aligner System
Dual Laminate
14. • The last category-aligners fabricated from digitally manipulated models,
is the largest growing area in aligner treatment.
• Using digital technology to control tooth movement, intricate and
precise tooth movements can be staged for each sequential aligner.
14
16. Classification
1) Based on clinical applications
• Retention Appliances
• Active Tooth Moving Appliances
2) Based on method of thermo plasticizing
• Vacuum Formed..i.e.Invisalign, Orthoclear, 3D
Ortholine, Clear Aligner Intl.,Essix
• Pressure Formed..i.e.Essix
16
18. Benefits
i. Esthetics: A transparent, clear design that is discreet.
ii. Comfort: Free from brackets or wires and resultant cuts and ulcerations.
iii. Improved oral hygiene and periodontal health: Removable nature
allows proper brushing and flossing.
iv. No food restrictions: Patients are free to eat or drink anything during
clear aligner therapy (CAT).
19
19. v. Predictable treatment time: Digital planning ensures a precise
estimation of treatment time.
vi. Decreased dental office visits: Patients themselves change their
subsequent aligners, requiring fewer office visits.
vii. Minimal emergencies: Significantly reduced emergency
appointments with CAT as compared to fixed orthodontic treatment.
viii. Possible to include teeth with structural anomalies and difficult-
to-bond surfaces
20
Sunegha Kundal1 , Tulika Shokeen, Aligners: The Science of Clear Orthodontics- International Journal of Dental and
Medical Specialty · June 2020
20. 21
treatment with clear aligners could be associated with better OHRQoL ratings
compared to treatment with conventional labially placed, metal, fixed appliances.
21. Limitations
i. Dependency on patient compliance: A wear time of 22 h/day is
mandatory for therapy to be effective.
ii. Limited extent of tooth movements by aligners alone: For complex
movements, auxiliaries are required as an adjunct to aligners.
iii. Higher cost.
iv. Initial slurring of speech: Subsides subsequently after 2–3 days of
wear.
22
22. v. Breakages: While wearing or removing if the patient applies excessive
force.
vi. Chances of losing the aligners: Removable nature makes aligners prone
to being misplaced.
vii. Inconvenience: Removing aligners every time one eats or drinks can be
a burden.
viii. Manufacturing defects: Results in ill-fitting aligners
Growth skeletal
23
Sunegha Kundal1 , Tulika Shokeen, Aligners: The Science of Clear Orthodontics- International Journal of Dental
and Medical Specialty · June 2020
23. Overview of steps in clear aligner treatment
1. Case records and case selection
2. High-quality impressions or intraoral scans
3. 3D virtual set-up and treatment progress stages
4. Approval of treatment steps on the web
5. Construction of aligners’ delivery to treating doctor
6. Issue of aligners and review
7. Finishing and retention
24
25. • With the new improvements in the system, there are almost no
contraindications ‘per se’.
• It is up to the practitioners to decide the cases that are to be treated
by aligners.
• However, certain aspects are harder to handle, and it is important to
anticipate the dental movements and possible problems that may
need to be encountered.
26
26. High-quality impressions
• High-quality polyvinyl siloxane (PVS) impression.
• The most common shortcoming is failure to capture sufficient detail of the distal of
the second molars.- retention of the appliance is compromised.
• So when certain forces are applied to the anterior teeth, the appliance is easily
dislodged.
• multiple areas of “drag” near the gingival margin
• surface or immediate subsurface air bubbles in the impression
27
28. • Every scanner has a hand-held wand containing a camera that is
connected to a computer.
• The wand may project either laser or white light onto the tooth surface
where it is reflected back to the camera, after which hundreds of
thousands of measurements per inch are performed to recreate the
three-dimensional representation of the teeth.
• The technology engineered into the wand determines the measurement
speed, resolution, and accuracy of the scanner.
29
29. Four types of imaging technologies are currently used
30
Triangulati
on
Parallel
confocal
imaging
Accordion
fringe
interfero
metry
Three-
dimension
al in-
motion
video
30. Triangulation
• CEREC (Chairside Economical Restoration of Esthetic Ceramics or CEramic
REConstruction) was the first in-office intraoral scanner introduced to
dentistry in the early 1980s.CEREC works using triangulation.
• This technique measures the angles and distances from known points
(laser source and sensor) with projected laser light.
• Others (Dentsply Sirona)
31
31. Parallel confocal imaging
• Projects laser light through a pinhole to the target.
• The sensor is placed at the imaging plane where it is in focus (confocal).
• A small opening in front of the sensor blocks any light from above or
below. Only the focused light reflecting off the target tissue will reach the
sensor for processing.
• This type of system creates thousands of tomographic slices and stitches
them together to form the three-dimensional picture.
• used by iTero, Align Technology, and Trios, 3S
32
33. Accordion fringe interferometry
• Two sources of light are used to project three patterns of light, called
“fringe patterns,” onto the teeth and tissue.
• Based on the shape of the object, the fringe pattern distorts and takes on
a new pattern.
• Surface data points of the fringe curvature are recorded by a high-
definition video camera that is offset from the projector by
approximately 30 degrees.
• True Definition Scanner, 3M ESPE, St. Paul, MN
34
34. Three-dimensional in-motion video
• Uses three tiny high-definition video cameras at the lens to capture
three precise views of the target.
• A sensor behind the cameras converts the light energy into electrical
signals, which allows the distances between two data points to be
calculated simultaneously from two perspectives to create the three-
dimensional data.
• The data points are captured in a video sequence and modeled in real
time.
• Lythos Digital Impression Systems, Ormco Corporation, Orange, CA
35
35. • Amornvit et al. compared the accuracy of ten different intraoral scanners
and found that Trios series scanners showed the best scan results
compared to other scanners.
Amornvit P, Rokaya D, Sanohkan S. Comparison of accuracy of current ten intraoral scanners.
Biomed Res Int. 2021 2673040.
37
36. DIGITAL TREATMENT PLANNING
• After the IOS, the digital models will be exported or uploaded to the
software in stereolithographic (STL) files.
• OrthoAnalyzer, SureSmile (Dentsply Sirona, Charlotte, NC, USA),
OrthoInsight3D (MotionView software, Chattanooga, TN, USA), Formlabs
PreForm (Somerville, Mass), SoftSmile (SoftSmile Inc., NY, USA), Orth’up
(C4W, France), Archform (ArchForm Inc. CA, USA), Bluskybio (BlueSkyPlan,
IL, USA), and Ulab (uLab Systems, TN, USA).
39
37. The basic steps of the software use :
• Load or import scans
• Alveolar arch coordination
• Segmentation
• Visual treatment objective (VTO)
• Staging
• Defining the number of aligners
• Add attachments
40
D. Thakkar et al. Seamless Workflows for In-House Aligner Fabrication. Seminars in Orthodontics 29
(2023) 17−24
38. Load or import scans:
• In this step a new case is created in the name of the patient and their intraoral scan
is imported into the software, arranged, cleaned and a virtual base will be added.
• trimming the virtual base to a horseshoe shape matching the alveolar arch is
recommended;
To enhance the efficiency of the 3D printing workflow
To reduce the amount of material and time required to print the model
41
39. Segmentation:
• individual tooth margin is defined(boundary recognition software), and the tooth
is separated in the upper and lower dentitions, which is very similar to a digital
Kesling setup
• The impression generally does not capture the interproximal surfaces of the
teeth, so the software must interpolate that information and estimate the
location of interproximal surfaces and contact areas.
• Once that is accomplished, virtual “roots” are placed. 42
40. • ToothShaper is the software to prepare the impression and
section the teeth.
• There are two basic steps to performing of ToothShaper
process:
Identification of facial axis of clinical crown(FACC) and
detailing imperfections in the impression
The facial axis of the clinical
crown for each tooth is identified using
a three point registration 43
41. • The technicians recreate the virtual gingival margins using morphing-type
software to mimic the gingival conditions seen on the clinical photographs
44
42. • When all the teeth have been segmented and cleaned up, the
technician prepares the models for the setup process.
• The axes are set in X, Y, Z directions.
The teeth are painted as an aid to discriminate each tooth
The teeth are
Teeth are segmented
45
43. • The next step is to set the bite in centric occlusion using an automated
tool in the software.
• The Autobite tool in Toothshaper has been perfected so that class I
and class II and most of class III bites are nearly automated.
Red marks indicate The dental arches are brought into occlusion
Arches registered in occlusion
46
44. Visual treatment objective (VTO):
• Teeth are moved according to the treatment plan
Staging:
• Segmental movements are planned to ensure there is space to move
teeth toward their intended position.
47
D. Thakkar et al. Seamless Workflows for In-House Aligner Fabrication. Seminars in Orthodontics 29 (2023)
17−24
45. Defining the number of aligners:
• some software complete this automatically while performing the VTO,
whereas others require a special command to achieve the same.
Add attachments
• some software possess an inbuilt feature for automatic attachment
placement, while others need manual addition of the same.
48
46. CLINCHECK—AN OVERVIEW
• The virtual setup for Invisalign for orthodontist- ClinCheck.
• ClinCheck is not the treatment plan; rather, it is the three-dimensional
interpretation of the treatment plan by the technician from the
prescription form submitted online
• Strict attention to each crown and to the root movement in all three
planes of space is required
49
47. The technician’s responsibility is to provide a virtual set-up that
• Follows the instructions on the prescription form
• Delivers tooth movements that fall within the predetermined
defaults of Invisalign’s Treat software.
50
48. • The technician uses a very robust proprietary software called Treat,
and the orthodontist’s interface with that program is a scaled-down
version called ClinCheck.
• Once the orthodontist has completed the virtual setup, the true
power of the Treat program is exhibited by the application of
SmartForce enhancements.
51
49. • SmartForce features are patented engineered solutions designed to
create precise biomechanical forces on selected teeth or groups of teeth.
• Research and development of the SmartForce features, combined with
the proprietary plastic, are unique to Invisalign.
52
50. ClinCheck Pro (6.0)
• is the most recent version of the software.
• Cloud based software- compatible with mac,pc or tab anytime,any
where.
• ClinCheck Pro allows the orthodontist to control individual tooth
movements in all three planes of space.
• Add or remove attachments and precision cuts.
• Mesio distal adjustments
• Occlusal contacts
• Antero posterior and midline correction.
53
51. • Auto and manual option for IPR and spacing.
• Arch shape can be changed by expanding or narrowing the posterior
segments.
• All changes made by the orthodontist appear in real time with
immediate adjustments automatically performed to adjacent teeth
and arch form.
54
52. • Four-dimensional printing involves using three-dimensional printing and
special geometric properties along with material characteristics to print
objects that can change their configuration based on outside influences,
such as motion or pressure.
55
53. STAGING OF TOOTH MOVEMENT IN
CLINCHECK
• An important aspect of controlling tooth
movement with aligners is staging.
• Staging is the sequence in which and the
speed at which teeth are moved with
aligners.
56
54. • The numbers across the top represent
different teeth
• Vertical axis represents an aligner
number.
• The vertical black bars in the diagram
indicate the timing and rate of tooth
movement. Each aligner number then
represents one stage.
57
Collision table
55. Estimating rate of tooth movement
• Estimating the total distance and dividing by the number of aligners,
assuming equal rates of movement occur throughout the entire
distance moved
58
56. Segmented tooth movements/staging
• Anchorage-one group of teeth is held stationary while a smaller group of
teeth is moved.
• Difficult movements were often left to the end of treatment- resulted in
prolonging treatment time by adding multiple additional stages.
• To reduce excessive numbers of additional stages, some difficult
movements were accelerated beyond a reasonable rate of movement.
59
57. • An alternative to segmented staging that more closely mimics fixed
appliance treatment is simultaneous staging.
• First suggested by Foy in 2004
• Refined by David Paquette (Staging Strategies, Effectiveness and
Efficiency with Invisalign Treatment, 2005 Invisalign Summit, Las
Vegas, NV)
• adopted by Align Technology in 2007
60
58. • This standard simultaneous staging pattern is also referred to as X
staging pattern.
• The basis for simultaneous movement is that all of the teeth within
each arch are moved together from the initial stage through the final
stage.
61
59. • Distalization of the maxillary dentition, starting with the molars, followed
by the bicuspids, and ending with the retraction of the anterior teeth, is a
type of staging known as V staging pattern and typically applies only to the
upper arch.
• The opposite of V staging pattern, in which the anterior teeth move
anteriorly, followed by posterior teeth moving anteriorly, is known as A
staging pattern.
62
60. • This pattern could be used in either arch to open previously closed
extraction spaces or to attempt to mesialize an entire arch in a segmental
fashion.
• M staging pattern is solely used for bicuspid extraction treatment.
movement starts by first closing the extraction spaces, followed by the
alignment of anterior teeth, and finishing with molar movement.
63
64. Materials for Thermoformed Aligners
• Clear aligner materials have evolved from single-layered or
monophasic plastic
• Second-generation polyurethane materials
• Third-generation multilayered materials that often comprise hard and
soft layers
• Soft layer-elastic deformation allowing smooth seating of the aligner,
hard -strength and durability
67
Y.M. Bichu et al. Advances in orthodontic clear aligner materials . Bioactive Materials 22 (2023) 384–403
70. • Ryu et al. studied changes in four types of thermoforming materials
after the thermoforming process.
• The study showed that thermoforming affects the transparency of
thicker material decreasing it, and increases water absorption
properties, water solubility and can also modify the surface hardness
of some plastics.
73
Ryu, J.H.; Kwon, J.S.; Jiang, H.B.; Cha, J.Y.; Kim, K.M. Effects of thermoforming on the physical and mechanical
properties of thermoplastic materials for transparent orthodontic aligners. Korean J. Orthod. 2018, 48, 316–325
71. Direct 3D printing/additive manufacturing
• Can avoid adverse effects of thermoforming processes, such as
alteration of mechanical, dimensional and esthetic characteristics of
the material
• Offering better geometric accuracy and precision, better fit, higher
efficacy and mechanical resistance and reproducibility
74
J.H. Ryu, J.S. Kwon, H.B. Jiang, J.Y. Cha, K.M. Kim, Effects of thermoforming on the physical and mechanical properties of
thermoplastic materials for transparent orthodontic aligners, Korean J. Orthod. 48 (5) (2018) 316–325.
C. Maspero, G.M. Tartaglia, 3D printing of clear orthodontic aligners: where we are and where we are Going, Materials
13 (2020) 5204.
72. 75
Y.M. Bichu et al. Advances in orthodontic clear aligner materials . Bioactive Materials 22 (2023) 384–403
73. Materials utilized
• Acrylonitrile-butadiene-styrene plastic
• stereolithography materials (epoxy resins)
• polylactic acid
• polyamide (nylon)
• glass-filled polyamide, silver, steel, titanium, photopolymers, wax, and
polycarbonates
76
S. Prasad, N.A. Kader, G. Sujath, T. Raj, 3D printing in dentistry, J. 3D Print. Med. 2 (3) (2018) 89–91
74. Tera Harz TC-85
• Photopolymer material introduced by Graphy to overcome the
current limitation of thermoforming sheet type aligners
• the Tera Harz direct aligner can be 3D printed directly with a 3D
printer.
• bio-compatible photopolymer material and is available in two colours
as clear and white.
• TC-85DAC (clear) is fully transparent, whereas TC-85DAW (white)
provides durability and aesthetics.
• Graphy Inc, claims that it can supply customized colours to meet
specific needs
77
Y.M. Bichu et al. Advances in orthodontic clear aligner materials . Bioactive Materials 22 (2023) 384–403
76. In-house aligner (IHA) or In-office aligners (IOA)
• clear aligner systems in which every aspect of aligner fabrication from
digital treatment planning to the delivery of orthodontic care is
managed in the orthodontic office itself
79
79. • Clear aligners fabricated in-house employ 3D resin printing.
• Resin printing in orthodontics involves different types of Stereolithography
(SLA) printing.
• There are three general types of SLA technologies commonly employed in
orthodontic clinical care:
laser SLA,
DLP (direct light processing)
LCD (liquidcrystal display ) masking.
82
80. • All these printing technologies have commonalities in that they all use
• The difference between laser SLA, DLP, and LCD technology is mainly the
way in which the light is projected to cure the photosensitive resin.
A photosensitive resin
A light source,
A membrane, and
A build plate.
83
81. Post-processing a crucial step in the 3D printing of the models.
• Washed in alcohol
• post-curing UV chamber
solidify the resin’s material properties
isopropyl alcohol (IPA)
tripropylene glycol monomethyl ether (TPM)
84
82. • Thermoforming
• Two types of thermoforming machines
• A compressor is required to warrant a tight fit between the aligner and
the model.
shaping of the selected type of sheet or
thermoplastic product with heat.
Vaccum forming
pressure forming
87
91. FIRST GENERATION
• The earliest forms of these systems were solely reliant
on the aligner shape to achieve their results.
• No auxiliary elements were incorporated.
• There is limited research available assessing the tooth
movements achieved by these aligners.
96
92. • Boyd was first to publish a case report of a mild crowding and space
closure case by Invisalign in 2000.
• Invisalign® (Align Technology, San Jose, CA, USA) used a polymer
mixture named Proceed30 (PC30) to fabricate aligners.
• Pazzini L, Cerroni L, Pasquantonio G, Pecora A, Mussi V, Rinaldi A, et al. Mechanical properties of
“two generations” of teeth aligners: Change analysis during oral permanence. Dent Mater J.
2018;37(5):835–42
97
93. Second-generation aligners
• 2009 Invisalign introduced Smart Force attachments like, for extrusions and
rotations.
• which are patient specific and tooth specific and continuously deliver
forces to teeth.
• Power Ridges(TM) for specific tooth movements like lingual root torque
available.
• Velocity Optimization integrated.
99
94. • Interproximal Reduction can be planned at later stages in
cases where contact points are difficult to access before
alignment is complete.
• Exceed30 (EX30) was used which was 1.5 times more
elastic than PC 30(easy insertion and removal of aligner trays and
better adaption was achieved)
100
95. THIRD GENERATION
• In 2010 G3 attachments-for optimized rotation control of premolars
(earlier available only for canines), Power Ridge for lower anteriors
(earlier available only upper anteriors) and lingual power ridge for upper
anteriors.
• To improve the outcome in Class II and Class III malocclusions new
Precision Cuts (doctor prescribed pre-cuts) were introduced.
• Help in easy attachment of Class II & Class III interarch elastics, (earlier
doctors had to manually cut the aligners)
101
96. FOURTH GENERATION
• In 2011 G4 attachments- to enhance the clinical outcomes in
Open Bites cases with inclusion of multiple teeth and
improved Optimized Extrusion Attachments in cases of
anterior open bite.
• Predictability of upper lateral incisors tooth movement was
improved with help of New Multi plane movements feature.
102
97. 5TH GENERATION
• Multilayer aromatic material made of a copolyester and thermoplastic
polyurethane Smart Track (LD30) is been used.
• Highlights of this material-greater and constant force delivery, chemical stability
and precise fit.
• G5 attachments for correction of deep bite were introduced to level the curve of
spee by controlled premolar extrusion and anterior intrusion.
• Also Precision bite ramps for disocclusion of posterior teeth undergoing
correction of deep bite were introduced in same year
104
98. 6TH generation
• 2014 Invisalign G6 for first premolar extraction:
Optimized retraction attachments were introduced for bodily
movement of canine which would eliminate unwanted tipping and
anterior extrusion with or without elastics.
Also Optimized Anchorage Attachments were introduced to strengthen
posterior anchorage.
105
99. 7TH generation
• Aims to deliver better finishing outcomes of case which were faced by
some clinicians
• G7 delivers better upper lateral control, improved root control, and
features to address prevention of posterior open bites
106
100. 8th generation
• G8 attachments for crowding and crossbite cases:
• Optimized expansion support and rotation attachments to reduce the
potential for buccal crown tipping during posterior arch expansion
• SmartForce aligner activation for anterior intrusion with improvements in
the treatment plan set-ups to level the Curve of Spee
• Demonstrates up to 2x improvement in predictability of incisor intrusion for
deep bite cases.
107
101. • With 2021 update, a New Invisalign Professional Whitening System
• Invisalign trained doctors to straighten and whiten teeth at the same
time has been introduced
108
103. CONTENTS
• Introduction
• History
• Classification
• Benefits
• Limitation
• Steps in clear aligner
• Scanning and digitization
• Digital treatment planning
• Clincheck—an overview
• 3D printing
• Materials
• In house clear aligner
• Comparison between edge wise and clear aligner
• Generations of aligners
• Attachment design in the invisalign system
• Power ridges and pressure areas in the invisalign
system
• Biomechanics in clear aligner
• Root control ,rotation correction, extrusion In the
invisalign system
• Clear aligner vs Tads
• Clear aligner vs orthognathic sugery
• Open bite,Deep bite
• Class II correction in invisalign
• Auxiliaries and the invisalign system
• Invisalign teen
• Articles
• Conclusion
• References 110
104. Attachments and features of smart force
ATTACHMENTS
Conventional
standardized
shapes
standardized
sizes
Optimized
shape and size is determined by the software
based on each patient and tooth.
111
105. CONVENTIONAL ATTACHMENTS
• Conventional attachments are passive attachments that increase the
engagement of the aligner onto the tooth.
• They act as handles
• These attachments may be placed on teeth by default through the software,
by written request to the software technician, or by using the “drag and
drop” feature on the 3D controls.
112
106. • In 2013, Align Technology developed the Smartforce Features in
order to create the optimal forces to move the teeth in a predictable
way.
• They can be placed.
On teeth, as optimized attachments
On the aligner, as pressure points or
power ridges
113
107. There are three types of conventional attachments.
1.Ellipsoid attachments
1.Rectangular attachments
1.Beveled attachments
114
108. • Ellipsoid attachments are passive attachments that are primarily used for
retention or anchorage.
• Used when the tooth surface area is limited.
• Eg :- the labial surface of maxillary lateral incisors or the lingual surface of a
lingually inclined mandibular second molar.
Ellipsoid attachments
115
109. • Rectangular attachments are passive attachments
Rectangular attachments
VERTICAL
useful for root
control
HORIZONTAL
used for root
control
a short clinical crown or occlusal interference
does not allow placement of a
vertical rectangular attachment. 116
110. • Both the vertical and horizontal attachments may also be beveled.
• Beveled surface is the active surface.
• The bevel provides a flat surface for the aligner to push against to effect
the desired tooth movement.
• For extrusive tooth movements on posterior molars, a horizontal
attachment that is beveled on the gingival will be effective. For intrusion,
use a horizontal attachment beveled on the occlusal.
Beveled attachments
117
111. • Optimized attachments are automatically placed by the software when it
detects certain thresholds of tooth movement.
• They are designed :-
to control the point of application of force
the direction of the force
the amount of force applied
which is customized for each individual tooth.
• All optimized attachments have an active surface that varies in geometry
based on the unique morphology of each tooth.
OPTIMIZED ATTACHMENTS
118
112. • The aligner is designed at a more acute angle than the active surface on the
attachment in order to exert a force on the active surface to move the tooth in
the desired direction.
• Therefore, the size of the attachment on the tooth will be different than the
size of the space in the aligner for the attachment.
• For this reason, if an optimized attachment needs to be replaced midway
through treatment, the clinician will have to use the original attachment
template or order a replacement attachment template to rebond the
attachment.
119
115. INVISALIGN FUNDAMENTAL PRINCIPLES
1: ALIGNERS ONLY WORK BY PUSHING TEETH; THEY DON’T PULL
2: MULTIPLE MOVEMENTS AT THE SAME TIME
3: ANCHORAGE IS REQUIRED FOR EFFICIENT MOVEMENT
4: OVER-ENGINEERING CLINCHECK IS A MUST
5: TEETH NEED SPACE TO MOVE
122
117. The shape molding
effect
“molding” the movement of the target teeth
according to the shape of the aligner used
The primary means of force application since the
inception of clear-aligner treatment in the 1940s
Pre-established mismatches (activation) between the
aligner shape and the dental crown geometry generate 3-
dimensional (3D) force systems distributed all over the
contact surfaces
Auxiliary elements
Attachments and power ridges
The strategic arrangement of these auxiliaries in
aligners or on the teeth can enhance force delivery 124
118. ATTACHMENT DESIGN IN THE INVISALIGN
SYSTEM
Attachments can be used for
• the retention of the aligner
• to enhance or facilitate specific tooth movements.
• Optimized attachments allow SmartTrack to produce the required
force, which creates the moment required to move the tooth as
shown in the ClinCheck.
125
119. POWER RIDGES AND PRESSURE AREAS IN THE
INVISALIGN SYSTEM
• An alternative to attachments-SmartForce
feature known as a power ridge- facilitate
torque control
• Power ridges are corrugations placed at
specific locations to enhance the undercut
near the labial gingival margin of teeth.
126
120. The power ridges function in two ways:
• To stiffen the gingival third of the aligner to make it more resilient
• To provide additional force as close to the gingival margin as possible to
increase the effective moment arm of the aligner.
• Advantage to power ridges
• Attachments need not be placed or removed, and they are more
aesthetically acceptable to the patient.
127
121. ROTATION CORRECTION IN THE INVISALIGN
SYSTEM
• Hahn et al. found that only a slight activation of ±
0.17mm or 0.5 ° per step during rotation could
produce ideal forces estimated between 0.35 and 0.6
N.
• Rotation of teeth with rounded anatomies such as
bicuspids and molars is particularly difficult
128
FIRST ORDER CONTROL
Hahn W, Engelke B, Jung K, Dathe H, Fialka-Fricke J, et al. (2010) Initial forces and moments delivered by removable
thermoplastic appliances during rotation of an upper central incisor. The Angle Orthodontist 80(2): 239-246.
122. • The limitations associated with rounded crown morphologies are due
to some extent to 3 particular realities;
1.The tangential nature of the forces produced during aligner-based
tooth rotation, along with very low coefficient of friction between the
two surfaces, facilitates a slipping effect between the aligner and tooth.
129
123. 2.The line of action of the normal force vectors
resultant from tangential forces delivered crosses at
a short distance from the center of resistance,
resulting in weaker rotational moments
130
Incorporation of bonded attachment increases the magnitude and
efficacy of rotational moment by increasing the perpendicular
distance (green dotted line) between the line of action (red dotted
line) and the center of resistance (cres)
124. 3.Unintended intrusion during rotational tooth movement.
During aligner-based rotation of an upper canine without attachment
displayed clinically significant intrusive forces that were found to be
3.71 times greater with attachments
131
126. SECOND ORDER CONTROL
• To improve second-order capabilities specialized attachments
• that generate equivalent force couples
133
A)Force couple produced during
bracket-based correction. (B)
equivalent force couple produced at
Optimized root control Attachments
(Align Technology, santa clara, CA)
127. 134
Producing equivalent moments (curved arrows), an increase in intervector
distance proportionately reduces force magnitude (blue arrows) acting at
attachment surface. Two degrees of distal tipping with a 4mm rectangular
attachment (A) will produce higher forces on the aligner than with a two
attachment configuration that significantly separates the force vectors (B) of
the acting couple.
128. Differential moments
135
class II case in which reciprocal moments between anterior and posterior segments during
extraction space closure (A)will result in 50% anchorage loss and class II occlusion (B).
129. 136
clockwise moments (blue curved arrows) produced by bonding rectangular horizontal attachments on
the buccal surface of posterior teeth (A) will counteract posterior anchorage loss, reducing it to 25%,
resulting in class I occlusion (B).
130. THIRD-ORDER CONTROL
137
(A) By preactivating (red shaded) and subsequently inserting (red) the archwire, a force couple (blue arrows) and
its corresponding counterclockwise moment (blue curved arrow) will be produced. (B) The same positive torque
can be achieved with aligners by producing an equivalent couple, with loser forces and increased intervector
distance
131. 138
(A) Aligner based expansive force (red arrow) applied at a distance from the center of resistance (CRes) will produce
counter clockwise moment (red curved arrow). (B) without preventive measures, buccal tipping followed by aligner
deformation and loss of control.
132. 139
(A) Opposing forces (blue arrows) acting at the occlusal surface and gingival aspect of a rectangular
horizontal buccal attachment will provide a clockwise moment (blue curved arrow) that reduces buccal
tipping, with apical migration of the center of rotation (CRot) (B).
133. Aligner Treatment in Class II Malocclusion
• CAT offers different possible therapeutic options
1 Distalization
2 Molar derotation
3 Elastic jump
4 Extractions
5 Mandibular advancement
6 Orthognathic surgery
140
134. MAXILLARY MOLAR DISTALIZATION
• In some nonextraction cases, maxillary molar distalisation is the
method of choice to gain 2 to 3 mm of space in the dental arch to
obtain a class I relationship in both teens and adults
• In 2016, Ravera et al demonstrated that distalisation is efficiently
achievable up to 2.5 mm on the first and second maxillary molars,
with optimal vertical control of posterior teeth and any loss of
anchorage on the anterior teeth
141
Ravera S, Castroflorio T, Garino F, et al.Maxillary molar distalization with aligners in adult patients a
multicenter retrospective study. Prog Orthod 2016
135. • maxillary molar distalization of 2.5 mm and premolar extraction
space closure (7 mm) are the most predictable and controlled
movements with CAT
142
Rossini G, Parrini S, Deregibus A, et al. Controlling orthodontic tooth movement with clear aligners
An updated systematic review regarding efficacy and efficiency. J Aligner Orthod2017
136. MAXILLARY MOLAR ROTATION
• Buccodistal rotation of maxillary molars can be considered a useful
procedure to partially improve class II dental relationship
• Molar rotation was indicated as one of the predictable movements
controlled by aligners
THE ELASTIC EFFECT
Simulated on virtual setups by a jumplike shift of the occlusion from class
II to class I
Fewer aligners are required when simultaneous staging is used along with
use of elastics as compared with distalization
Average period of 8.5 months for the correction of the class II discrepancy
with elastics only(predominant dentoalveolar effects)
143
137. The Clinical Protocol(Depending on the severity)
• Dental sagittal discrepancies where less than 3 mm- distalization
• dental discrepancies ranging between 3 and 5 mm-sequential
distalization combined, or not, with stripping, molar derotation, or an
elastic effect
• Dental discrepancy exceeds 5mm, either extraction treatment or
orthognathic surgery.
144
145. • 3D digital models were created, consisting of a maxillary dentition without
first premolars, maxilla, periodontal ligaments, attachments, micro-
implant, 3D printed lingual retractor, brackets, archwire and clear aligner
• The study involved the creation of five design models for clear aligner
maxillary anterior internal retraction and one design model for fixed
appliance maxillary anterior internal retraction, which were subsequently
subjected to finite element analysis
152
146. 1.The teeth movement pattern remained consistent across all five clear
aligners, characterized by lingual tipping and extrusion of anterior teeth,
as well as mesial tipping of posterior teeth during anterior retraction.
2.Fixed appliances exhibit superior control over torque in anterior teeth
and provide better protection against anchorage loss in posterior teeth
compared to invisible appliances.
153
147. • 3.The implementation of an additional force system in clear aligners
did not alter the observed trend of tooth movement, but it did exert
an influence on the magnitude of tooth displacement.
154
148. Functional treatment in growing class II
patients
• Cozza et al- Twin block is the most efficient removable functional
appliance because it can stimulate 0.23 mm/month of mandibular
growth (for a total of 3.4 mm in 13 months), followed by the Bionator
(0.17 mm/month, total 2.8 mm in 12 months), and then the Frankel II
(0.09 mm/month, total 2.8 mm in 18 months)
155
Cozza P, Baccetti T, Franchi L, et al. Mandibular changes produced by functional appliances in class II
malocclusion: a systematic review. Am J Orthod Dentofacial Orthop. 2006;129(5):599.e1-12; discussion e1-6
149. • Combining the twin block and the
aligner advantages to stimulate
growth of the mandible while aligning
and leveling in growing patients
• The Leone company appliance called
Runner
• The Align Technology company
appliance is the Invisalign aligner
incorporating lateral wings engaging
the mandible in a forward position
156
150. The mandibular advancement system is
divided into three clinical phases:
• Pre–mandibular advancement phase: the occlusal locks, which prevent
expression of mandibular growth, are removed (correction of overbite,
maxillary molar rotations, and overjet)
• Mandibular advancement phase: 2-mm advancement every eight aligners
is performed
• Transition phase (or stabilization phase): maintains the class II correction
157
152. • Aim: To evaluate the dentoskeletal effects of the Invisalign®
Mandibular Advancement (MA) (Align Technology, San José,
CA, USA) feature in skeletal Class II growing patients with
mandibular retrusion, at pre-pubertal and pubertal stages.
• The use of Invisalign® MA is effective in treating Class II
growing patient with retrognathic mandible in the short term
period. While treatment at prepubertal stage of growth results in
dentoalveolar rather than skeletal effects, treatment during the
pubertal spurt produces skeletal effects with an annual rate of
change of 5.8 mm.
159
157. Watermelon seed effect
• Aligners have the inherent ability to simultaneously engage the
occlusal, buccal, and lingual surfaces of teeth.
• This helps to apply compressive forces from all directions
• Create a resultant force vector that is directed through the center of
resistance of target teeth.
164
158. • Tooth crowns are not symmetrical structures.
• This asymmetry often creates an uneven distribution of forces, and the
resultant force will most likely miss the center of resistance and create a
moment.
• If this moment can be predicted in advance, then certain modifications
“pressure areas” can be added to the aligners to create an additional force
that will redirect the net compressive force through the center of resistance
165
159. Bite ramps
• Deep-bite correction is also achieved by
extrusion of posterior teeth. The key step is to
remove occlusal forces.
• Bite ramps or lingual prominences can be added
to the palatal surface of maxillary incisors or
canines near the cingulum area, to disocclude
the posterior teeth and encourage extrusion
166
160. • Simple tipping of anterior teeth can lead to pseudo correction of the
overbite
• This impact does not involve a “true” intrusion of anterior teeth (a
movement along the longitudinal axis of teeth) but rather just a
relative movement of the incisor crown downward and backward.
167
161. • This method might well be the easiest way to fix an excessive
overbite, because directing forces through the center of resistance of
target teeth is very difficult.
• “Power ridges” are indents placed on aligners in the gingival third of
the crown for enhancing the tipping of incisors.
168
Madhur Upadhyay∗ , Sarah Abu Arqub, Biomechanics of clear aligners: hidden truths & first
principles, Journal of the World Federation of Orthodontists 11 (2022) 12–21
163. Open bite
• Open-bite correction is the reverse of deep-bite correction
• Anterior teeth need extrusion instead of intrusion; posterior teeth
need intrusion instead of extrusion; and incisors have to be tipped
back or retroclined for pseudo correction of the anterior open bite
170
164. • The mechanics and auxiliary elements are also similar.
• The intrusion of posterior teeth will cause a forward and
counterclockwise rotation of the mandible, leading to a reduction in
open bite
171
165. • Harris et al-The primary mechanism of open-bite closure comes from
the drawbridge effect or simple tipping of incisors, accounting for
close to 60% of the correction.
• This closure is followed by autorotation of the mandible caused by
posterior teeth intrusion, accounting for another 30% of the total
correction.
172
167. • Attachments and anchorage optimized anterior extrusive attachments
are automatically placed on the incisors by the software when pure
extrusion of 0.5 mm or more is detected
174
168. Power-Grip pressure relief device
• Two buttons on the aligner at the adjacent teeth, and intra-
jaw elastics.
• Extrusion is activated by changing the elastics 3-4 times a
day.
• When the necessary extrusion is complete, the aligner locks
the tooth in the desired position
175
169. POSTERIOR INTRUSION
• The presence of interocclusal plastic may produce a bite-block effect
that potentiates bite closure and posterior intrusion capabilities
176
Intrusion in the posterior segment (red arrows) produces
reactive forces that will tend to dislodge the aligner anteriorly
(blue arrows). Adequate attachment selection on anterior teeth
will counteract this undesired occurrence.
170. COW-CATCH ALIGNERS
• Cow-Catch Clear Aligners could be used for finishing and detailing during
aligner treatment or for relapse treatment cases.
• The main benefit of Cow-Catch Clear Aligners over a tooth positioner is
the ability to extrude the teeth more rapidly with elastics
Park JH, Kim TW. A new approach to open bite treatment. Oral Health J. 2010;100(9):25-8. 177
171. COW-CATCH ALIGNERS
S. Alami, A. EL Aouame, A. EL Moutawakil, F. Benammar, F. EL Quars. Biomechanics of
Aligners: Literature Review. Adv Dent & Oral Health. 2021; 13(4) 178
172. MODIFIED COW – CATCH ALIGNER
• If the patient cannot open their mouth fully while wearing Cow-Catch Clear
Aligners, this can be easily corrected using lingual buttons on the target teeth .
It is also more convenient and comfortable for the patient because it allows
for normal function to continue
179
173. Surgery first and CAT
180
Two treatment modalities
• Placing labial orthodontic appliances including a wire prior to surgery
1-2 weeks before.
• These fixed appliances are used for 2to 4 months after surgery
• The appliances are then removed after this short phase of
orthodontic fixed therapy and invisalign trays are given to the patient
until treatment completion
1
174. • Uses Invisalign as the only appliance for orthodontic movement after
surgery without the use of any fixed labial appliances
181
2
180. AUXILIARIES AND THE INVISALIGN SYSTEM
• Other auxiliaries can be used to facilitate specific movements.
• Class II and Class III elastics are frequently needed.
• One can directly attach the elastics either to the aligner or to the
buttons bonded to the teeth.
• If the elastics are directly attached to the aligner, then attachments
are generally required to prevent displacement of the aligner.
187
181. • Miniscrews can also be effectively used with aligners.
• The two most common uses of miniscrews with aligners are for
vertical and sagittal movements. One such example is the extrusion of
an upper canine.
• Another vertical movement that is easily enhanced with miniscrews
is the intrusion of molars that have supererupted into an edentulous
space.
188
182. A miniscrew in the lower arch and then running a rubber band from a clear
button near the gingival on the upper canine to the miniscrew as the
aligner guides the tooth into the correct position.
189
183. INVISALIGN TEEN
• Originally, Invisalign was anticipated for use with adults for those
individuals with a fully erupted permanent dentition.
• Its being able to treat the late mixed dentition with aligners provided
certain benefits as well.
191
184. • The shortcomings to overcome were anticipating
tooth eruption of one or more permanent teeth,
being able to monitor patient compliance to
discuss the progress (or lack thereof) with parents,
proper control of torque without the need for
attachments when crowns were not yet fully
exposed, and, finally, avoiding practice
management issues over lost aligners.
• Eruption tabs are used to prevent supereruption of
unerupted second molars.
192
185. • Wear indicators are placed on the facial
surfaces of the first molars .
• Two different types of chemical indicators are
available that turn from dark blue to clear as
the aligners are worn.
• These indicators are designed so that teenagers
cannot realistically figure out a method to have
both indicators change without actually
wearing the aligners.
193
187. Evaluation of the effectiveness of tooth
movement
• In 2005, no conclusion was possible concerning the
effectiveness of aligners in the correction of malocclusions
• 2009-Kravitz et al- who conducted an independent study
comparing the effectiveness of tooth movement with
Invisalign®. They obtained an average treatment efficacy of
41%
• They concluded that the most precise movement with this
device was lingual displacement (47.1% average precision) and
the least precise was extrusion (29.6%) and mesiodistal tilt
(26.9%), which can be explained, as the authors point out, by
the fact that Invisalign® cannot exert a vertical pulling action on
a tooth 195
188. • Recent articles have suggested that aligners present some
difficulties with specific orthodontic movement such as rotational
movements, vertical movements, obtaining adequate occlusal
contacts, torque control, and transverse expansion and found
that the accuracy of tooth movement (vs predicted) with aligners
still hovers around 50%. Fixed appliances fare much better on
accuracy and predictability of treatment
196
189. Evaluating the efficiency of conventional
orthodontic treatment vs. aligner
• The treatment time for the aligner’s technique was significantly
shorter than that for fixed appliances:
• According to Buschang: 11.5 vs. 17 months
• According to Djeu: 1.4 vs. 1.7 years
197
190. • Zheng et al., have shown that aligners have a significant
advantage over chair time
• Aligners have therefore been recommended mainly for simple
to moderate malocclusions
• Multi-attachment treatment requires more visits (+65%), more
time in the chair (+50%), and generates more emergencies
198
191. Assessing the quality of life of patients
using orthodontic treatment
• White DW et al., study confirm that both systems (aligners and multi-
attachments) can induce pain after insertion or activation
• Fixed systems cause more pain and discomfort than removable
appliances. Aligners can cause slight speech problems, which are
minimized by adjusting the aligners to the dental profiles
• The impact of the aligners on patients’ quality of life was favorable in
terms of pain, adaptation, and speech.
199
193. • Objectives: To assess if there is any difference in pain levels between
orthodontic treatment with clear aligners or fixed appliances
• Orthodontic patients treated with Invisalign appear to feel lower
levels of pain than those treated with fixed appliances during the first
few days of treatment.
• Thereafter -differences were not noted
201
194. ROOT RESORPTION WITH CLEAR ALIGNERS
There is no clear consensus on root resorption with CAT.
• A lower incidence and severity of root resorption has been reported,
with incisors being the most affected teeth
• Lower severity and prevalence of root resorption with aligners.
202
Gay G, Ravera S, Castroflorio T, Garino F, Rossini G, Parrini S, et al. Root resorption during orthodontic
treatment with invisalign®: A radiometric study. Prog Orthod 2017;18:12
Li Y, Deng S, Mei L, Li Z, Zhang X, Yang C, et al. Prevalence and severity of apical root resorption during
orthodontic treatment with clear aligners and fixed appliances: A cone beam computed tomography study.
Prog Orthod 2020;21
195. Retention and Stability Following Aligner
Therapy
• To date, there is no universal retention protocol
• most common retention devices are the Hawley retainers and clear
thermoplastic retainers. for the mandible, a fixed retainer is often
indicated
• thermoplastic retainers-good aesthetics
203
196. INDICATIONS OF VARIOUS RETENTION DVICES
Hawley retainers
• for patients who have need for an increased
stabilization of the canine positions
• patients after transverse expansion or after
treatment of a deep bite when the appliance
is also serving as a bite plate.
204
197. In class II cases where intermaxillary elastics or a bite-jumping device
was used
• an activator with van der Linden labial bow and Adams clasps on
maxillary molars or 2 clear thermoplastic appliances with class II
precision wings should be considered
205
198. Fixed retainers
• compromised periodontal health( periodontal splints)
• spacing or midline diastemas
• after complicated space closure following extractions
• severe tooth rotations
• open bite
• with impacted canines
• space maintainer before dental implants are placed
206
199. REFERNCES
• Orthodontics current principles and techniques- Graber vanarsdall
• Timothy T. Wheeler, Orthodontic clear aligner treatment, Seminars in
Orthodontics 2016.
• Boyd RL, Vlaskalic V. Three-Dimensional Diagnosis and Orthodontic Treatment of
Complex Maloccluslons With the Invlsalign Appliance. Semin Orthod. 2001;7:274-
283.
• Clear aligner technique
• Wong BH. Invisalign A to Z. Am J Orthod Dentofacial Orthop 2002;121:540-1
• Orthodontics: diagnosis and management of malocclusion and dentofacial
deformities- OP Kharbanda
• Kesling HD. The philosophy of the tooth positioning appliance. Am J Orthod
1945;31:297-304.
207
200. • Gay G, Ravera S, Castroflorio T, Garino F, Rossini G, Parrini S, et al. Root
resorption during orthodontic treatment with invisalign®: A radiometric
study. Prog Orthod 2017;18:12
• Li Y, Deng S, Mei L, Li Z, Zhang X, Yang C, et al. Prevalence and severity of
apical root resorption during orthodontic treatment with clear aligners and
fixed appliances: A cone beam computed tomography study. Prog Orthod
2020;21
• S. Alami, A. EL Aouame, A. EL Moutawakil, F. Benammar, F. EL Quars.
Biomechanics of Aligners: Literature Review. Adv Dent & Oral Health. 2021;
13(4)
• Park JH, Kim TW. A new approach to open bite treatment. Oral Health J.
2010;100(9):25-8.
208
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produced a tooth positioning appliance to refine the final stages of orthodontic treatment.
This positioner was a piece of pliable rubber manufactured from a laboratory wax up of the teeth in a class I occlusion (Phan and Ling, 2007). This appliance allowed for minor tooth movements to be achieved while maintaining alignment of the remaining teeth in the arch. Tooth control was difficult, and only tipping of crowns was possible
As the story goes, both were given Essix retainers to correct some minor orthodontic relapse and were struck by the same question: “Why couldn’t I have had these instead of braces?” Their orthodontists told them that it was only for very minor problems anddismissed the possibility of correcting complex malocclusions with aligners
Different aligners have patented different softwares like Invisalign uses ClinCheck, Nuvola aligner uses software NUVOLA CAD 3D, SureSmile has the software named Orasacanner 2.
In segmentation the virtual cast model is divided into a set of smaller surfaces one for each tooth. Software called tooth shaper is used during this step.
A common misconception is that the technician providing the initial setup has diagnosed the patient’s malocclusion and has sent back a ClinCheck treatment plan that is ready for approva
The technician is neither qualified nor responsible for delivering a treatment plan for the patient.
Construction of aligner
The modulus of elasticity or Young’s modulus is a measure of the stiffness of a material and can be defined as the ratio between stress and corresponding strain. An aligner material should ideally possess adequate stiffness to exert the forces and moments needed to achieve the planned tooth movement. If the material used for aligner fabrication exhibits a very high modulus of elasticity (or high stiffness), then the resultant aligner would be very stiff leading to difficulty in aligner placement and removal for the patient. Likewise, a material with low stiffness will not be able to generate adequate forces required to move teeth
The complete workflow for the fabrication of IHAs essentially consists of the following st eps
Laser SLA printing uses a laser
DLP uses a digital micro-mirror device (DMD)
LCD projection uses an LCD light source and a “masking” screen to cure a whole layer of photosensitive
Each of these printing technologies, when properly employed, can be used for the fabrication of in-house aligners
These differences affect the accuracy, speed, and cost associated with various printers
3D printed models should be washed in
two washes will be needed to fully clean the 3D-printed models
A UV chamber is often required to achieve the post-curing by exposing the 3D-printed models to light and heat to help solidify the resin’s material properties
In-office aligners today, can be fabricated from both thermoformed materials and direct printing resins
this paper chiefly focuses on in-house aligner fabrication from thermoformed materials
The thermoplastic polymers most commonly used to manufacture commercial clear aligners include polyester, polyurethane or copolyester, polypropylene, polycarbonate, ethylene vinylpolyvinyl chloride, and many other materials
Two types of thermoforming machines are commonly available: vacuum forming (which operates on the principle of air depression and pressure forming (Biostar, Ministar, Erkopress) which generates pressurized air above the thermoplastic sheet to press it against the model
with pressure forming being more efficient and accurate.
In clear aligner treatment, the anchorage segments can be predetermined and may change at different stages in treatment. In this respect, clear aligners offer extremely good control of anchorage because the anchorage teeth may be made immovable at different stages of treatment. For example, in the staging of sequential distalization of the maxillary arch, only the second molars are distalized in the initial stages of treatment. The remaining teeth in the arch from first molar to first molar do not move in the initial stages and act as an anchorage segment to push the second molars distally for anteroposterior correction
For example, in a case where a buccally erupted canine requires extrusion, as the canine extrudes, the adjacent lateral and central incisors and firstpremolar will intrude (Fig 2-8). This may create a temporary cant to the occlusal plane. Eventually as the treatment progresses into more rigid archwires, the occlusal plane will level out. In the event reciprocal tooth movements are undesirable, a rigid archwire may be placed to stabilize the occlusal plane, and a flexible twin-wire overlay may be placed to extrude the buccally erupted canine
Extrusion of a single tooth is a moderately difficult tooth movement for clear aligners, depending on the amount of extrusion required. At times, some auxiliary treatment such as buttons and elastics may have to be placed to assist with single-tooth extrusion. However, extrusion of groups of teeth, for example when maxillary incisors are extruded to close an anterior open bite, may be performed successfully with clear aligners
Clear aligners offer the power ridge feature for lingual root torque (Fig 2-13). The incisor torque in the finished occlusion may be predetermined for individual patients depending on the initial malocclusion, desired final occlusion, and soft tissue lip support. Clear aligners are very efficient in managing incisor torque where excessive torque is not desired. Excessive torque may be undesirable in cases with mild incisor protrusion that are treated nonextraction, just like with fixed appliances, there is an element of play between the aligner and the teeth, making the actual torque expressed clinically less than that prescribed. Therefore, in extraction cases where someadditional tprq final
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to accomplish with plastic aligners without the help of specialized attachments, which improve biomechanical capabilities.
) otational forces produced by the aligner (purple arrows) are transmitted to the tooth as normal force components (red arrows), hich are perpendicular to tooth surface tangents (purple dotted lines). (B) ncorporation of bonded attachment increases the magnitude and efcacy of rotational moment by increasing the perpendicular distance (green dotted line) beteen the line of action (red dotted line) and the center of resistance (es)
Intrusive forces observed at the periodontal ligament without attachments as . for every degree of rotation, while iath attachments the load as reduced to . for every degree. ATT, Attachment. (Adapted from óme P, Peña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation ith plastic aligners a three dimensional nite elements analysis. J Align Orthod. .)
A 25year old female patient
class 2 division 1
moderate crowding in the upper arch The overjet 10mm
class 2 elastics for at least 21 hours per day she used the Acceldent device for 21 minutes e
r 63 aligners-3mm) 30months
maxillary molar distaliation of about 6 mm without signicant tipping and an excellent control of the buccolingual inclination of the incisors
The class 2 elastics were responsible for a mandibular protraction of about 1.5 mm
17.8 mm of movement was required in the maxilla and 14.8mm in the mandible
2-mm distal movement of the upper rst molars and 2-mm mesial movement of the lower rst molars
overepansion of the dental arches
10 months
10 month class 2 continue
Orthopulse-10minuts
ligner changes to 3 day
Mandibular advancement can be reached only if other eventual occlusal features have been modified (i.e., maxillary molar derotation, dentoalveolar expansion of the upper arch, deep bite and consequent leveling of the curve of Spee, and retroclination of the incisors), so that a prior preparation phase is required before starting mandibular advancement.
At the end of treatment, mandibular advancement is maintained by arch coordination and anterior interference removal.
9-year-old girl, in mixed dentition, with molar class II relationship, deep bite, proclined upper incisors, and retruded mandible. Cephalometric analysis shows a moderate skeletal class II malocclusion, with an ANB angle value of 5 degrees, and Wits value of 7 mm
An Invisalign Teen treatment with the mandibular advancement feature was performed
advancement of the mandible together with deep bite correction
2 mm of advancement every eight stages, and aligners were changed every week. After 6 months of treatment, a bilateral class I molar relationship was achieved
; hence, the term “watermelon seed effect.“
local deformation of the inclined inner surfaces of the appliance and with a reduced fit during progressiveaxial rotation, which tends to deform the appliance like a bow, by raising it in the anterior region
This improves treatment outlook, in cases in which anterior extrusion is not desirable and intrusion of posterior teeth, with the consequent mandibular rotation, are to be considered as part of the strategy for bite closure.
A New Approach to Open Bite Treatment
A New Approach to Open Bite Treatment
during which time major intra arch movements are accomplished and intermaxillary vertical elastics are use
19-year-old female patien
Al ready done camouage treatment for a class skeletal relationship addressed through the extraction of maxillary rst premolars
adequate arch alignment and a class 2 occlusion with a 5-mm overje
denture base was anteriorly positioned to the apical base in the mandible and the lower incisors were signicantly labially inclined.
The rst one required the extraction of two mandibular premolars to retract the mandibular incisors achieving a large overjet to obtain a signicant mandibular advancement with surgery
The second option was a nonextraction approach with a counterclockwise rotation of the maxillomandibular complex in conjunction with a genioplasty
