Appliances in Presurgical Orthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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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 www.indiandentalacademy.com
Review • Bracket systems • First generation
Andrews
1972
• Second generation Ronald Roth
1980’s
• Third generation
1990’s
MBT
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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. www.indiandentalacademy.com
Friction /frictionless mechanics Frictionless mechanics
Anterior segment Vs posterior segment
Friction mechanics
Anterior segment Vs posterior segment + Friction Increased anchorage demands
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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. www.indiandentalacademy.com
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 www.indiandentalacademy.com
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
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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
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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
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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
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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 laterals – buccal root torque
Detorqueing
Posterior
Anterior
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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 www.indiandentalacademy.com
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 www.indiandentalacademy.com
Pretreatment
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extra oral
Pretreatment
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intra oral
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During treatment intraoral
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Post treatment
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extra oral
Post treatment
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intra oral
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 www.indiandentalacademy.com
Anterior segmental osteotomy • Objectives – Coordinate arches in the transverse dimension – Leveling – Divergence of roots at the planned osteotomy site
• Treatment plan • Mechanotherapy • Anchorage preparation www.indiandentalacademy.com
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. www.indiandentalacademy.com
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 www.indiandentalacademy.com
Segmental mechanics
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Bonding modification
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Pretreatment
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extra oral
Pretreatment
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intra oral
During treatment
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intra oral
Post treatment
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extra oral
Cleft patients
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Problems in finishing • Tip • Torque • Mesio distal diameter (Bolton’s ratio) • Curve of spee
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Ideal finish •Consistency •Accuracy •Predictability •Convenience
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Tip
Change in tip alters the mesio distal diameter occupied www.indiandentalacademy.com
Torque Space closure Lower arch the complete space closure achieved
Inability of complete space closure in the upper arch
Loss of torque www.indiandentalacademy.com
Mesio distal diameter
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Proximal stripping
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Post treatment
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intraoral
Curve of spee
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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
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Acknowledgement Dr. Munirathinam Naidu Principal Dr.PJaykumar Vice Principal and HOD Staff and students Department of Orthodontics Meenakshi Ammal Dental College, Chennai www.indiandentalacademy.com
Thank you www.indiandentalacademy.com Leader in continuing dental education
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