Sure smile

RECENT ADVANCES
IN DIAGNOSTIC AIDS
www.indiandentalacademy.com

• Sure smile (computer assisted
diagnosis and treatment)
• EMG
• Finite element modeling and analysis

Sure smile
Computer assisted diagnosis and
treatment

Clinical procedure
• Oroscanner

• The image is reference independent,
meaning the image capturing process is
not affected by movement of patient or
scanner.
• Scanner is placed in mobile care smile
cart and that rolls from chair to chair.

• A full oral scan is taken and integrated
with the conventional; photographs and
x rays and entered into the electronic
patients record.

• Once the process is complete the teeth
can be moved in 3 dimensions with the
software controls.

• 3D viewing of the model like frontal,
lateral, posterior or occlussal views or
different perspective using navigation
tools.

• The teeth can also be viewed as
individual arches.

• The operator can diagnose and plan the
treatment with tools to measure tooth
and arc dimensions and symmetric and
asymmetric arc forms.

• A 3D coronal cross section like a 3D cat
scan is also available for evaluation of
3rd
order relationships.

• The clinicians plans treatment based on
the parameters such as midline,
occlussal plane and arc dimensions,
multiple plans are stimulated for
comparison.

Target occlusion

• The operator can manipulate by moving
the teeth with mouse or selected
menus.
• You can extract or reduce the teeth
mesially or distally to simulate
interproximal disking.

• The changes in x, y and z co-ordinates
can be done in individual case to show
case difficulty and treatment changes.
• Inter arch contacts and relations ,such
as over bite and over jet ,can be
viewed with a cutting plane tool ,which
displays interproximal or an transverse
view anywhere along the arch.

• After the target occlusion the digital
bracket placement system and
geometric calculation of the wires and
forces exerted and their impact on teeth
can be assessed.
• The operator can based on the forces
and amount of tooth movement
required can decide the optimum
treatment plan.

• Any errors in bracket positioning and
arch wire selection can be detected and
changed during any phase of the
treatment.

Advantages
• Reduce errors in treatment planning and
appliance management.
• Reduce undesirable toot movements ,bracket
placement errors, errors in wire selection,
bending and adhesive thickness are all
reduced.

Advantages
• It provides image capturing, 3D visualization
of the tools from diagnosis, monitoring and
patient communication, along with precision
appliances that can help the orthodontist
deliver truly customized treatment in a patient
centered practice.

Accuracy of the system
• Oro Scanner
• Digital Bracket Placement
• Wire Bending

Electromyography

• Electromyography is defined as the
recording and study of the intrinsic
skeletal muscle by means of surface or
needle electrodes .
• Electromyography is the instrument
used.
• The structural basis of EMG is the
motor unit.

Motor Unit Potential
• During each twitch of the muscle fibre, a
minute electrical potential is generated,
which is dissipated into the surrounding
tissues.
• The duration may be there for
2 –3 millisecond or 4 millisecond.

• Majority of the motor unit potential have an
amplitude of around 5mv.
• Einthoven first discovered a muscle
contraction gives a idiomuscular current.This
is referred to as an action potential.the
current is so small that it has to be amplified
several hundred times.
• Using electromyography one can get a
relatively accurate picture of the muscle
activity under diverse functional conditions.

Technique
• Two types of electrodes are mainly
used –
• Surface electrodes ( skin)
• Needle electrodes

Needle electrode
• Superior to surface electrodes and
produce better Electromyograms.
• Lesser technical artifacts
• Distance between muscle and electrode
is constant
• May cause infection and is painful

Surface electrodes
• non invasive and reduced risk of
infection
• Possibility of loosening of electrodes
while nerve stimulation.
• Errors in variation between distance of
muscle an electrodes.

• Important guideline for adequate needle
insertion is to observe and palpate the scale
while test maneuver is done.
• It is important to test the insertion by asking
the patient to contract the muscle being
tested.
• If the needle is correctly placed this
maneuver should produce correct and crisp
action potential.

Drawbacks
• Impossible to know how much activity of
the muscle being missed.
• Movement cannot be inferred from
electromyography alone, because
antagonistic muscles may be working
synergistically to produce movement or
provide stabilization.

Electromyography in orthodontics.
• Muscles of importance ( figure )

EMG activity in class II div 1
• Graber points out –
class I -normal muscle activity
(except open bite )
class II div 1 – abnormal muscle activity
class II div 2 – compensatory muscle
activity.

Pancherz study
• Class II div I patients .
• Recordings were made in patients in
maximal biting in centric occlusion
during chewing.

Results
• Using maximal biting class II exhibited less
EMG activity in the masseter and temporalis
than controls
• During chewing class II showed less muscle
activity in EMG than in controls in masseter
• For temporal muscles no differences were
found
• The impaired muscle activity fond in class II
cases may be attributed to Diverging
dentofacial morphology and unstable
occlussal conditions.

• Moyers investigated EMG in children in
class II div I and concluded that there
was dysplasia in function in the
temporal muscle in habitual occlusion
and at rest.
• He asserted this as an etiologic factor
for post normal occlusion.

Functional appliances
• James Mcnamara (jr) studied change in
muscle activity in functional appliance
treatment.
• During first few hours after functional
treatment – no change
• Distinct change after first few weeks.

• Decrease in activity of the
posterior-temporalis
• Increase in activity if the masseter
muscle and the lateral pterygoid
muscle.
• As the experiments progressed the
pterygoid response decreased and the
gradual return to pre treatment levels
occurred.

• Lacouture et al ( AJO DO 1997)
• Three types of appliances – Herbst,
twin block and the Frankel.
• To test the lateral pterygoid
hypotheses.

• Ingervall and Thuer ( AJO DO 1991)
• Muscle activity during first year of
treatment during activator therapy
• No decrease in degree of activity of the
posterior temporal muscle.

Class III subjects
• Deguchi and Iwaara (Angle Orthod 1998)
• It is believed that there is decrease in
co-ordination between the masseter and
temporalis muscles in treatment of open
bite.
• The integrated activity of the masseter
and the temporal muscle activity in
class III less than normal occlusion
subjects

Electromyographic activity during
swallowing
• Winders et al (Angle Orthod) buccal
and lingual musculature do not contract
during swallowing unless there is an
anterior open bite and anterior skeletal
dysplasia.

Electromyographic activity during
swallowing
In tongue thrust habit there is increase in
genioglossus activity and hypertrophy
of the tongue muscles (EMG activity
increases during hypertrophy).

Effect from pain in orthodontic
treatment on EMG activity
• Goldreich et al (AJO DO 1994)
Reduction ion muscle activity
Ngan et al (Ang Orthod 1997 )

Lip and cheek activity in sucking
habits
• Ahlgeren et al 1997
• Increase in mentalis activity
• Buccinator muscle was less evident.

Cleft lip and palate patients
Li et al (Cleft Palate Craniofac 1998 )
In unilateral ceft lip an palate activity
- a higher activation levels of temporalis
and masseter in rest position
- Lower potential function of masseter in
temporalis and masseter
- In harmonious activity of the muscles
during movements

Finite element modeling

• Originated from advances in aircraft
structural analysis.
• Clough in 1960 first coined the term
finite.
• Zienkewic and Chung published the first
book in 1967.

Definition
• Technique of discrediting a continuum
into simple geometric shapes elements
enforcing material properties and
governing relationships on these
elements giving due consideration to
loading and boundary conditions which
results in set of equations ,the solution
which gives approximate behavior of
the continuum.

Applications
• Stress and vibration analysis
Ex – automobile,aircraft,aerospace
• Field analysis
• Ex – heat flux, fluid flux, seepage etc

Role of computers
• With the advances in computer
technology and CAD system complex
problems can be modeled with relative
ease.
• Alternative configurations can be
tried/analyzed on the computer before
the first prototype is built.
Ex – design and development of the first
Boeing 747 aircraft.

Advantages
• Model irregularly shaped bodies easily
• Handle general load conditions without
difficulty
• Model bodies composed of several different
materials because the element equations are
evaluated individually.
• Handle united numbers and kind of boundary
conditions .

• Vary the sizes of elements to make it
use small elements wherever
necessary
• Induce dynamic efforts
• Handle non collinear behavior existing
with large deformations and non linear
materials.

Computer programs
• Algor
• Ansys
• Cosmos/m
• Stardyne
• Images 3D
• Sap 90

Finite element analysis software
• There are three basic components-
• Preprocessor ( step 1 )
• Processors ( step 2 to 4 )
• Post processor ( step 5 )

Methods of finite element generation
• Single node and element generation.
• Digitizing input
• Pattern generation
• Duplication
• Region generation
• Dragging generation

Applications in Orthodontics

• Finite element model of apical force
distribution from orthodontic tooth
movement
David et al (Angle Orthodontist 2001)

• 3 D finite element analysis orthodontic
forces in periodontal tissue
Lu et al (Angle orthodontist 1999)

• 3 D finite element analysis of mandible
and tmj during distraction osteogenesis
Kofod et al (j craniofac surg 2005)

• Anchorage effects of palatal
osteointegrated mini implants
Chen et al (Angle Orthodontist 2005)

• Used for appliance selection and
analysis of orthodontic mechanics
• To determine the center of resistance
and center of rotation
• To evaluate canine retraction by sliding
mechanics

NEW REALM OF ORTHODONTIC
DIAGNOSIS

Sure smile

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Sure smile