This slide gives an full view of the important bio mechanics of temporary anchorage devices (TADS) this slide includes : # Bio-mechanical principles of miniscrews in orthodontics # Force Systems #Biomechanical Considerations : Miniscrews #Biomechanics For Anterior Retraction #Biomechanics For Molar Intrusion #Biomechanics For Molar Distalization #Biomechanics For Molar Uprighting #Biomechanics For Molar Protraction

1. By
Dr. Gejo Johns
Dr.GEJO JOHNS 1

2. Bio-mechanical principles of miniscrews in orthodontics
 Force Systems
 Biomechanical Considerations : Miniscrews
 Biomechanics For Anterior Retraction
 Biomechanics For Molar Intrusion
 Biomechanics For Molar Distalization
 Biomechanics For Molar Uprighting
 Biomechanics For Molar Protraction
Dr.GEJO JOHNS 2

3.  Miniscrews are used to generate a constant, single force with mild to moderate
magnitude, regardless of the patient compliance.
 To achieve predictable results with miniscrews
 Two factors are essential
1. Understanding of anatomic structures for appropriate insertion
2. Knowledge of biomechanics to construct precise force systems.
Dr.GEJO JOHNS 3

4.  The force delivered by miniscrew can be
1. Single linear force
2. Moderate magnitude of force
Dr.GEJO JOHNS 4

5. Components :
1. Single mini screw
2. Elastics – E-chains / NiTi coil springs
E chain or NiTi coil spring attached to the head generates a linear force whose line of
action is represented by the direction of the elastic component.
Line of action is represented by
 Insertion site of miniscrew
 Location of attachment on tooth / hooks in archwire
Dr.GEJO JOHNS 5

6. Components :
1. Multiple mini screws
2. Elastics – E-chains / NiTi coil springs
3. Uprighting springs
Line of action is represented by - Multiple force vectors
 A single miniscrew is expected to withstand more than 200-300 gms of force
 Provides anchorage in heavy load situations
Dr.GEJO JOHNS 6

7. EFFECT OF MINISCREW DIAMETER AND LENGTH ON STRAIN ON THE BONE
Dr.GEJO JOHNS 7

8.  Tapered design : Advantages over cylindrical design.
1. Reduced diameter at apical region – Minimizes possible root injury
2. Larger collar area : Better distribution of stress on the cortical bone.
3. More stability : Larger coronal portion lies in the cortical bone, tapered portion
in the trabecular bone.
4. Ease of insertion – Less micro gaps – less wobbling – more stability
Dr.GEJO JOHNS 8

9. Standard (universal type)
•Maxillary buccal alveolus
•Mandibular buccal alveolus
•Midpalatal area – minimal / thickness.
•Palatal slope – if soft tissue thickness is thin.
Wide-collared
•Host bone quality is
soft/thin.
•Growing patients with
immature cortical bone
Long-collared type
•Insertion sites with thick soft
tissue
•Maxillary palatal slopes
•Mandibular retromolar pad areaDr.GEJO JOHNS 9

10.  The button shaped head portion allows
engagement of elastic components.
 The non- threaded, smooth collar
portion forms the junction with the
overlying soft tissue.
 Reverse buttress thread around the
upper one third of the threaded area
contributes to wide distribution of
stresses during lateral loading
Dr.GEJO JOHNS 10

11.  Trapezoidal thread design makes the
penetration easy without pre-drilling.
 Cock-screw –like tip facilitates the initial
penetration on cortical bone.
 Sandblasting and acid etching maximize
osseointegration
Dr.GEJO JOHNS 11

12. Dr.GEJO JOHNS 12

13. Reinforcement of anchorage is primarily required in upper arch compared to lower
arch:
1. Comparison of root surface area
Maxillary anteriors: Higher root surface
area than Mandibular anteriors
Maxillary arch : Higher posterior
anchorage value that helps for anterior
retraction
Dr.GEJO JOHNS 13

14.  2. Tooth movement for anterior retraction :
Bodily Translation more frequently planned in upper arch in case of class II
Controlled Tipping planned in Mandibular arch
 3. Bone quality in posterior segment
Maxilla : Trabecular bone
Mandible : Thick cortical bone
Dr.GEJO JOHNS 14

15. Type A anchorage
• Firm anchorage required so as to
prevent mesial movement of posteriors.
• Miniscrews placed – beginning of
retraction in both upper and lower arch
• Favourable site : Between second
premolar and first molar.
Maximum anchorage case, where
more than 75% of the space is used
for retraction
Dr.GEJO JOHNS 15

16. Type B anchorage
•Anterior and posterior segment
moved reciprocally to close space
• Upper mini implant may be
indicated in the middle of retraction
phase, depending on the movement
of posterior segment
Dr.GEJO JOHNS 16

17. Type C anchorage
• When more than 75% of space is to
be closed by protraction of molars,
or when second premolar
extraction is indicated.
• Can be treated as non-extraction cases ,
using mini-implants for distalization of
whole arch or by second molar
extraction
Dr.GEJO JOHNS 17

18. • Sliding mechanics – Continuous
arch
• Force system – can be predicted
based on the Cres
• Loop mechanics – Discontinuous
anterior and posterior segment
• Force system - unpredictable
Dr.GEJO JOHNS 18

19.  In conventional mechanics a reverse curve of
spee is incorporated to the arch wire to reinforce
the posterior anchorage and counteract the
reactive mesial tipping of molars .
 Reverse curve of Spee along with miniscrews
may induce excessive distal tipping of the
posterior segment leading to posterior open bite.
Dr.GEJO JOHNS 19

20. 1. Controlled tipping
2. Root movement
3. Translation
 Establishing the line of force – below or through the Cres
 Achieved by : Posterior segment – Height of placement of screws
Anterior segment – Length of lever arm
Dr.GEJO JOHNS 20

21. LIMITATIONS IN ESTABLISHING A LINE OF FORCE :
• Height of attached gingiva and buccal frenum
• Possible soft tissue impingement
• And such possible soft tissue impingement limits the placement of miniscrews generally below
the centre of resistance of the maxilla.
 Thus an equivalent force system needs to be made – which is achieved by adjusting the height
of lever arm, and giving an additional torque in the rectangular arch wire
Dr.GEJO JOHNS 21

22. Appliance construction for controlled crown tipping.
 The line of force runs below the Cres of the anterior segment and thus controlled tipping of
the incisors is expected .
 Short hooks anteriorly
 Regular retraction force of 150-250 gm/side.Dr.GEJO JOHNS 22

23. Appliance construction for root movement
 Line of force : Below the Cres of the anterior segment
 Short hooks anteriorly
 Labial crown torque in the anterior segment.- increases the moment for root movement.
 Light continuous force from the miniscrew prevents flaring of incisor tip
 Reduced retraction force of 100 gm/side.Dr.GEJO JOHNS 23

24. Class II div 2 cases
 Line of force : Below the Cres of the anterior segment
 Short hooks anteriorly
 Additional mini screw in the anterior segment for intrusion
 Labial crown torque in the anterior segment. – Root movement
 Reduced retraction force of 100 gm/side. – prevents flaring of incisor tip
Dr.GEJO JOHNS 24

25. Pure bodily retraction of anterior – Labial
 Line of force : Through the Cres of the anterior segment
 Longer lever arms (hooks)
 Labial crown torque in the anterior segment.
 line passes slightly below the Cres, thus an anterior labial crown torque is given to
counter act the lingual tipping of crown.
 Reduced retraction force of 100 gm/side.Dr.GEJO JOHNS 25

26. Pure bodily retraction of anterior – Lingual orthodontics
 Line of force : Through the Cres of the anterior segment
 Miniscrews placed on the palatal slope.
 Easily extended lever arms (hooks)
 NO torque in the anterior segment.
 Reduced retraction force of 100 gm/side.
Dr.GEJO JOHNS 26

27.  Some of the common indications for molar intrusion are
1. Increased anterior facial height
2. To initiate auto-rotation
3. Prosthetic purpose : Making space for prosthesis
Increasing the interdental height.
Dr.GEJO JOHNS 27

28.  Force should be balanced bucco-lingually and mesio-distally for pure intrusion.
 Line of force should pass through the Cres of molar :
 Centre of occlusal table
 Near the furcation area
 Closer to the palatal root of maxillary molar.
 Recommended insertion site of miniscrews :
 Buccal surface – mesial interdental area
 Palatally – distal interdental areaDr.GEJO JOHNS 28

29. • Additional miniscrews can be placed on either side of the alveolar slope to
adjust the force direction.
• Three or four miniscrews are useful to prevent or correct the tipping of severely
extruded molars.
Three miniscrews
Four miniscrews
Dr.GEJO JOHNS 29

30. • Insertion site of implant for intrusion of 2 adjacent molars : Interproximal buccal and palatal
area
• The Cres located below the inter-proximal contact close to the molar *
* Nanda R. Esthetics and Biomechanics in Orthodontics.Elsevier Health Sciences; 2012 May 7.
INTRUSION FOR MOLAR AND ADJACENT TEETH
Dr.GEJO JOHNS 30

31.  Symmetrical intrusion – Intrusive force delivered through transpalatal bar connecting both
molars
Control of palatal tipping :
1. Expansion of TPA
2. Additional miniscrews on buccal side
Control of mesio-distal tipping ( sagittal direction)
 Miniscrew should be inserted on the line connecting the central fossa of both molarsDr.GEJO JOHNS 31

32. Dr.GEJO JOHNS 32

33. ADVANTAGES :
 Non - compliance therapy doesn’t need patient compliance.
 Better than head gear
 Better than other intra oral distalization appliances: (distal jet / conventional pendulum
appliance)
 No undesired action in the anterior segment.
To achieve a distal translation of molar the line of force need to be established at the
vertical level of Cres of the molar
Dr.GEJO JOHNS 33

34. Indications :
 Non – compliant patient
 To establish Class I molar relation
 Regain space for non-extraction treatment
Limitations of insertion site :
 Buccal or palatal slope – prevent injury to developing tooth germs.
 Central suture area is not completely closed during the prepubertal stage, so the success
rate of miniscrews in prepubertal stage is not as good as the post pubertal stage
 Optimum site for placement :
Midpalate or Anterior rugae area
Dr.GEJO JOHNS 34

35. Biomechanics :
 Line of force : passes below (coronal) the Cres of maxillary molars .
 Initial distal tipping of molars
 Later, root movement of molars is required
( achieved by fixed mechanotherapy in permanent dentition)
Dr.GEJO JOHNS 35

36.  Possible appliance designs :
1. Miniscrew-reinforced Nance holding arch
Before Distalization After Distalization
Dr.GEJO JOHNS 36

37. 2. Bone-borne Pendulum appliance
Before Distalization
After Distalization
Dr.GEJO JOHNS 37

38.  Insertion site : Both palatal and buccal alveolar slopes
 Line of force : Through the Cres of molar
Indication
1. Non-extraction method of gaining space
2. Class II molar relation
 Lever arm from mid palatal miniscrews and transpalatal arch
Dr.GEJO JOHNS 38

39. 1 Combination of transpalatal arch and Lever arm from mid palatal miniscrews
 Insertion site : Mid palatal sutures
 Line of force : through the Cres of molar
Horse shoe shaped TPA
Mini-screws with lingual
sheath
Lever arms
E-chain attached
to the hooks on
the TPA
Dr.GEJO JOHNS 39

40.  Insertion site : Palatal alveolar slope
 Line of force : Through the Cres of molar
2 Miniscrews from the palatal slope and transpalatal arch
Dr.GEJO JOHNS 40

41.  Insertion site : Buccal alveolar slope
 Line of force : through the Cres of molar
3 Indirect anchorage from Buccal slope miniscrews and open coil spring
•Buccal open coil spring – Distal movement of the molars
•Ligature ties from the premolar to the miniscrew prevent anterior movement of the
premolars - indirect anchorage from the premolars
Dr.GEJO JOHNS 41

42. Dr.GEJO JOHNS 42

43. Molar uprightening is frequently indicated for Mesially tipped second molar.
Miniscrew insertion site : Mesial / distal side of the target molar depending on
following clinical situations:
 Mild mesial Tipping
 Moderate Tipping
 Severe Tipping
Dr.GEJO JOHNS 43

44.  Miniscrew insertion site : Interdental area mesial to first molar
 Line of force –
 Single Distally directed force by the open coil spring
 passes above the Cres of second molar
Segmented
stainless steel
wire from the
miniscrew head
with an open
coil spring
Dr.GEJO JOHNS 44

45.  Miniscrew insertion site : Interdental area mesial to first molar
 Line of force –
 Step 1 : Linear distal force - open coil spring
 Step 2 : Tip back moment – uprighting spring
 Line of force passes above the Cres of second molar creates distal tip back moment
Linear distal force from the open
coil spring - unlocking of the
second molar
Distal Tipback moment by the
uprighting springDr.GEJO JOHNS 45

46. Linear distal force from the open
coil spring - unlocking of the
second molar
Tipback moment by the uprighting
spring
Mesially tipped second molar
Dr.GEJO JOHNS 46

47.  Miniscrew insertion site :
 Distal to the target molar.
 Retromolar area
 Line of force –
 Single distal force above the Cres of second molar
- creates distal tip back moment
Dr.GEJO JOHNS 47

48. Dr.GEJO JOHNS 48

49. Dr.GEJO JOHNS 49

50. Frequently required in Mandibular arch in case of missing molars.
- Because the increased cortical bone density hinders the natural mesial movement of
molars.
Dr.GEJO JOHNS 50

51.  INDICATION :
 Closure of space anterior to molars.
 Congenitally missing premolars
 Miniscrew insertion site : between first and second premolars at the level of furcation
area of molar.
 E-chains are engaged to protract the molars
Dr.GEJO JOHNS 51

52.  Line of force : should pass through the Cres of Molar.
 Makes use of lever arm made of rigid SS wire.
Protraction with a single force without lever arm
- mesial tipping of molar which lead to bowing of
arch wire in premolar region
Protraction with a lever arm -
passes the line of force through
the Cres – prevents tipping.Dr.GEJO JOHNS 52

53.  Indication :
 Molar which has already mesially tipped into the anterior space.
 Missing, impacted or ankylosed tooth.
 Miniscrew insertion site : Mesial interdental space buccally in relation to the target molar
 Force system :
1. Tip back moment – For uprighting of molar
2. Mesio-gingival force – To counteract extrusion and distal crown movement.(Passive elastic tie)
And the Net result is Pure root movement.
Dr.GEJO JOHNS 53

54. The MAUS – Generates an extrusive force and tip back moment on the molar – mesial rotation of molar
Passive Elastic tie from the miniscrew – mesio gingival force vector :
1. Counteracts the extrusion of molar
2. Counteracts the distal crown movement of molar
Blue– The extrusive force and tip
back moment generated by
uprightening spring
Red – Light mesio gingival force
vector counteract the extrusion and
distal crown movement from the
passive elastic.
Dr.GEJO JOHNS 54

55.  Indication :
 when an already mesially tipped second molar needs to be protracted into a
Mutilated first molar space.
 Miniscrew insertion site : Two screws - mesial interdental space buccally in relation
to the target molar.
 Second screw – supports the long range of action of the spring.
Dr.GEJO JOHNS 55

56. Force system :
1. Miniscrew assisted Uprighting spring - intrusive force – creates moment for root movement
2. Active elastics – mesio-gingival force for protraction of molar
Net result : Root movement (uprighting) + mesial translation
Blue- Tip back and intrusive
force are generated by root
spring because of presence of
second miniscrew.
Red – Additional mesial force
by E-chain
Dr.GEJO JOHNS 56

57. Pre treatment OPG
I molar – indicated for extraction
OPG after 14 months of treatment
Dr.GEJO JOHNS 57

58.  Contemporary orthodontics- Proffit
 Orthodontics-current principles and techniques-Graber,Vanarsdall,Vig
 Nanda, R. and Uribe, F.A., 2009. Temporary Anchorage Devices in Orthodontics.
 Sugawara J. Skeletal anchorage system using orthodontic miniplates. Temporary Anchorage
Devices in ORTHODONTIC. 2009:427-68.
 Park Y. Biomechanical Principles in Miniscrew Driven Orthodontics. Temporary Anchorage
Devices in ORTHODONTIC. 2009:317-41.
 Kook YA, Park JH, Bayome M, Kim S, Han E, Kim CH. Distalization of the mandibular
dentition with a ramal plate for skeletal Class III malocclusion correction. American Journal of
Orthodontics and Dentofacial Orthopedics. 2016 Aug 1;150(2):364-77.
Dr.GEJO JOHNS 58

59. Dr.GEJO JOHNS 59