Appliances in presurgical orthognathic surgery /certified fixed orthodontic courses by Indian dental academy

Appliances in
Presurgical Orthodontics
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Introduction
• Orthodontic treatment prior to and after surgical
correction of malocclusion is considered vital to
the stability of the achieved result
• Pre surgical orthodontics helps the oral surgeon
to align the skeletal bases on the operating
table

Review
• Bracket systems
• First generation

Andrews

1972

• Second generation Ronald Roth

1980’s

• Third generation

1990’s

MBT


Slot dimension
• .022 versus .018
• The slot dimension preferred and widely used
by the orthodontist for a surgical case is .022
slot, the stability is better as it allows the use of
stiffer wires.

Friction /frictionless mechanics
Frictionless mechanics

Anterior segment
Vs posterior
segment

Friction mechanics

Anterior segment
Vs posterior
segment +
Friction
Increased anchorage
demands


Tip
• Inbuilt tip VS expressed tip
• Inbuilt tip - The tip built into the bracket
• Expressed tip – on insertion of wire – the
change in the mesio distal inclination of tooth
• The effect of the inbuilt tip and expressed tip on
the mesiodistal inclination of teeth is very
minimal.

Torque
• Inbuilt torque and expressed torque
• loss of torque – cardinal rule

For every 0.001” play there
is loss of 40 loss of torque

PAE is highly inefficient in regaining
lost torque

Comparison of upper tip
7

6

5

4

Roth

00

00

00

00

MBT

00

00

00

00

3

2

1

Roth

+130

+90

+50

MBT

+80

+80

+40


Comparison of upper torque
7

6

5

4

Roth

-140

-140

-70

-70

MBT

-140

-140

-70

-70

3

2

1

Roth

-20

+80

+120

MBT

-70,00, +70

+100

+170


Comparison of lower tip
Tip

7

6

5

4

Roth

-10

-10

-10

-10

MBT

00

00

+20

+20

3

2

1

Roth

+70

+20

+20

MBT

+30

+00

+00


Comparison of lower torque
7

6

5

4

Roth

-300

-300

-220

-170

MBT

-100

-200

-170

-120

3

2

1

Roth

-110

-10

-10

MBT

+6,0,-60,

-60

-60


Bends in the rectangular wire

Palatal root torque on
the anterior and
posterior region

Anterior region – desirable
Posterior region - undesirable

Distal to the www.indiandentalacademy.com root torque
laterals – buccal

Detorqueing

Posterior

Anterior


Decompensation
Skeletal mal- relationship
Teeth compensate to mask the skeletal
discrepancy
Pre- surgical orthodontics
Eliminate the dental compensation that has
occurred with respect to the skeletal base

Class II decompensation
 Objectives
 Co-ordinate the arches in transverse dimension
Leveling
Class II molar and canine relation ship
Obtain sufficient over jet

 Treatment plan
 Mechanotherapy
 Anchorage preparation

Pretreatment
oral


extra

Pretreatment
oral


intra

During treatment
intraoral


Post treatment
oral


extra

Post treatment
oral


intra

Class III decompensation
• Objectives
– To coordinate the arches in transverse
dimension
– Leveling
– Class III molar and canine relationship
– Reverse overjet&

• Treatment plan
• Mechanotherapy
• Anchorage preparation

Anterior segmental osteotomy
• Objectives
– Coordinate arches in the transverse dimension
– Leveling
– Divergence of roots at the planned osteotomy
site

• Treatment plan
• Mechanotherapy
• Anchorage preparation

Segmental /Continuous
mechanics
• Segmental mechanics are more Bioefficient
with less adverse effects
• Statically determinate system – thus possible
to know the exact amount of forces and
moments in the system
• Though continuous mechanics is a statically
indeterminate system, it has been widely
preferred by the orthodontist due to the easy
cookbook approach.

Creating step at osteotomy site
• Aligning by a segmental approach at the
osteotomy site – most beneficial
• Altering the height of the bracket positioning to
achieve the extrusion of the to be intruded
segment
• Use of a stainless steel or a TMA spring to
create a step at the osteotomy site which TMA
is preferable
– Achieve stabilization of posterior segment with
stainless arch wire
– Insert the spring into the auxiliary tube

Segmental mechanics


Bonding modification


During treatment
oral


intra

Cleft patients


Problems in finishing
• Tip
• Torque
• Mesio distal diameter (Bolton’s ratio)
• Curve of spee


Ideal finish
•Consistency
•Accuracy
•Predictability
•Convenience


Tip

Change in tip alters the mesio distal
diameter occupied

Torque
Space closure
Lower arch the
complete space
closure
achieved

Inability of
complete space
closure in the
upper arch

Loss of torque

Mesio distal diameter


Proximal stripping


Post treatment
intraoral


Curve of spee


Conclusion
• Learn to appreciate the concept of inbuilt tip
and torque versus expressed tip and torque
• Develop individual orthodontic sense instead of
blindly following prescription and bracket
systems
• Having a thorough knowledge of biomechanics
involved will help the orthodontist to supplement
any deficiency present in the system that is
being used


Acknowledgement
Dr. Munirathinam Naidu
Principal
Dr.PJaykumar
Vice Principal and HOD
Staff and students
Department of Orthodontics
Meenakshi Ammal Dental College, Chennai

Thank you
Leader in continuing dental education


Appliances in presurgical orthognathic surgery /certified fixed orthodontic courses by Indian dental academy

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