The document discusses various biomechanical considerations for using microimplants in orthodontic tooth movement. It describes how the placement location and height of microimplants, as well as the force applied, can be used to produce different types of tooth movement. Specifically, it discusses how low-, medium-, and high-pull microimplant mechanics can be used to control the rotation of the maxillary and mandibular occlusal planes during anterior retraction. It also describes how microimplants can enable intrusion of anterior and posterior teeth as well as other tooth movements.

1. Biomechanical considerations in
microimplant anchorage
By: Dr.Mamoun Khawileh under
supervision of dr Maher Fouda

2. The type of tooth movement that can be produced with
microimplant anchorage is determined by the same
biomechanical principles and considerations that operate
during conventional orthodontic treatment :
1. Force.
2. Moment.
3. Center of resistance.
4. Center of rotation.

3. Types of tooth movement can be produced depending on the
position of the microimplant, the height of the elastomare
attachment , and the magnitude of the force applied.

4. Maxillary anterior en masse retraction
mechanics in extraction cases
In masse retraction mechanics in extraction cases can be
classified in three categories much like the descriptors used
traditionally for headgear traction:
1. Low- pull mechanics.
2. Medium -pull mechanics.
3. High pull -mechanics.

5. Low –pull mechanics for the maxillary arch
When the microimplant is placed between the roots of the
maxillary second premolar and first molar and is less than 8mm
away from the main archwire, the term low-pull en masse
retraction mechanics is used. if force applied from a low-pull
microimplant to an anterior hook extending 6 to 7 mm above the
main archwire , the maxillary occlusal plane usually can be rotated
in a clockwise direction .therefore ,low-pull mechanics are useful in
treating patients who have an open bite tendency.

6. the maxillary occlusal plane will rotate in a clockwise direction during
anterior en masse retraction, if low-pull sliding mechanics are used.

7. Medium–pull mechanics for the maxillary arch
When a maxillary microimplant is placed about 8 to 10 mm
above the main archwire, the term medium –pull en masse
retraction mechanics is used. if force applied from a medium
–pull microimplant to a hook located between the lateral
incisor and canine that extend 6 to 7mm vertically, the
maxillary occlusal plane ordinarily can be maintained .thus,
medium-pull mechanics are useful in treating patients who
have normal overbite relationships.

8. The maxillary occlusal plane can be maintained during anterior en masse
retraction, if medium-pull sliding mechanics are used.

9. high–pull mechanics for the maxillary arch
When a maxillary microimplant is placed about 8 to 10 mm
above the main archwire, the term high –pull en masse
retraction mechanics is used. if force applied from a high –pull
microimplant to an anterior hook extending above the main
archwire, the maxillary occlusal plane usually will rotate in a
counterclockwise. The high-pull mechanics are usefull in
treating patients who have a deep bite .

10. the maxillary occlusal plane will rotate in a counterclockwise direction during
anterior en masse retraction, if high-pull sliding mechanics are used.

11. Mandibular anterior en masse retraction
mechanics in extraction cases
medium–pull mechanics for the mandibular arch:
Mandibular microimplants usually are placed between the second
premolar and first molar roots for anterior en masse retraction .
When a Mandibular microimplant is placed about 6 to 8 mm away
from the main archwire, the term medium–pull en masse retraction
mechanics is used. if force directed from a medium-pull
microimplant to a hook located between the lateral incisor and
canine that extends 4 to 6 mm below the main archwire, the
mandibular occlusal plane usually can be maintained .therefore,
medium high-pull mechanics are useful in treating patients who
have normal overbite relationships.

12. The mandibular occlusal plane can be maintained during anterior en masse
retraction, if medium-pull sliding mechanics are used.

13. Low –pull mechanics for the mandibular arch
When a microimplant is placed buccaly between the roots of the
mandibular second premolar and the first molar and is less than 6 mm
away from the archwire, the term low-pull en masse retraction
mechanics is used. if force applied from a microimplant in low-pull
location to an anterior hook extending 4 to 6 mm below the main
archwire a counterclockwise rotation of the mandibular occlusal plane
typically can be achieved. low-pull mechanics are useful in treating
patients who have an open bite tendency.

14. the mandibular occlusal plane will rotate in a counterclockwise
direction during anterior en masse retraction, if high-pull sliding
mechanics are used.

15. high–pull mechanics for the mandibular arch
When a microimplant is placed buccally between the roots of
the first molar and second premolar and more than 8 mm
away from the main archwire. if force applied from a high –
pull microimplant to an anterior hook extending 4 to 6 mm
below the main archwire. the mandibular occlusal plane
usually can be rotated in a clockwise direction . therefore,
low-pull mechanics are useful in treating patients who have
deep bite or deep bit tendency.

16. the mandibular occlusal plane will rotate in a clockwise direction during
anterior en masse retraction, if high-pull sliding mechanics are used.

17. Anterior intrusion mechanics in the maxillary arch
For intrusion of the maxillary anterior teeth, microimplant can
be placed between the roots of the upper incisors. Force can
be applied from the microimplant directly to the main
archwire. usually a force originating from a single
microimplant placed between the maxillary central incisor
roots is adequate to intrude the anterior dentition.

18. The maxillary anterior teeth can be intruded effectively using maxillary
anterior microimplants. The microimplant are placed between the roots of
the central or lateral incisors.

19. Anterior intrusion mechanics in the mandibular
arch
For intrusion of the mandibular anterior teeth, microimplant
can be placed between the roots of the lower incisors. Force
can be applied from the microimplant directly to the main
archwire. usually a force originating from a single
microimplant placed between the mandibular central incisor
roots is sufficient to intrude the anterior dentition.

20. The mandibular anterior teeth can be intruded effectively using
mandibular anterior microimplants. The microimplant are placed
between the roots of the central or lateral incisors.

21. anterior en masse retraction with anterior
intrusion
In deep bite extraction cases, high–pull mechanics are
recommended in the maxillary arch for intrusion of the
anterior teeth during en masse retraction. posterior
microimplants usually will be more effective in retracting the
anterior teeth, whereas anterior microimplants will be more
effective in intrusion. furthermore, anterior intrusion
microimplants will counteract the tendency for incisors to tip
lingually during their retraction.

22. Anterior microiplants are used to intrude and tip the crowns during en masse
retraction.

23. anterior en masse retraction and anterior intrusion with tow posterior
microimplants and one or tow anterior microimplants instead of traditional
high-pull headgear mechanics.

24. Sliding mechanics vs. loop
When a sliding mechanics are used for anterior en masse
retraction, fabricating the main archwire is relatively easy.
however if first, second or third order bends need to be
incorporated, sliding mechanics cannot be used effectively.
conversly, when loop mechanics are used for anterior en
masse retraction, fabricating the main archwire is more
complicated. however first, second or third order bends can
be incorporated with ease.

25. Step-up bends can be incorporated into the maxillary incisor segment
when loop mechanics are used.

26. when loop mechanics are used, it is possible to incorporate second-order
gable bends into the incisor segment.

27. Molar intrusion mechanics for openbite cases
In that it is possible to intrude molar using microimplants, openbite
can be corrected relatively easily, especially skeletal openbite. If 1
mm of absolute molar intrusion is achieved postriorly, an anterior
openbite of 2 to3 mm will be closed anteriorly. A microimplant is
placed between the roots of the maxillary second premolar and
first molar or / the first molar and second molar, buccally and/ or
palatally, for the intrusion of maxillary molar teeth. transpalatal
arch is used for palatal microimplants. In the mandibular arch,
however, it is not advisable to insert microimplants lingual to the
molar roots; a lingual holding arch can be used for support instead.

28. intrusion mechanics for maxillary posterior teeth using four
microimplants.

29. intrusion mechanics for maxillary posterior teeth using two
buccal microimplants and a transpalatal arch.

30. intrusion mechanics for mandibular posterior teeth using two
microimplants and a lingual arch.

31. Maxillary anterior lingual root torque mechanics
After anterior en masse retraction in an extraction case,
severe lingual tipping of the maxillary anterior teeth
sometimes is observed. Whenever lingual root torque then is
applied, labial crown tipping usually is observed instead. To
prevent this kind of labial crown tipping, class II Elastics are
required. Moreover, to prevent the side effect of the class II
elastics ,up-and down vertical elastics and high-pull headgear
are used.

32. Maxillary anterior lingual root torque mechanics combined with
microimplants. During lingual root torque application, labial crown tipping
can be prevented by connecting ligature wires from buccal microimplants
to a hook extending vertically from the main arch wire. mechanics

33. Molar distalization mechanics for non-extraction
cases
Microimplant can be placed between the roots of the second
premolar and first molar, and nickel titanium coil spring can be
used. A after molar distalization, the anterior Teeth will need
to be retracted. The first microimplant can be removed if it
interferes with this retraction, and a second microimplant is
placed just distal to the first one or between the first molar
and second molar roots.

34. Mandibular molar distalization mechanics in class III case. After molar
distalization, the anterior teeth will need to be retracted. The first
microimplant is removed if necessary, and a second implant is placed
distal to the first one or between the first molar and second molar roots.

35. Retraction of the entire maxillary or mandibular
dentition
Two buccally –placed microimplants can provide sufficient
anchorage to move the entire maxillary or mandibular
dentition posteriorly .Retraction of the enier dentition is more
effective in patient who have mesially tipped posterior teeth.
Thus, microimplants function nicely in combination with the
multiloop edgewise arch wire for retraction of the entire
dentition.

36. if there is sufficient bone buccal to the roots, the entire dentition
can be retracted with adequate space between the microimplant
and the roots of adjacent teeth.

37. If a microimplant touches the root of a maxillary second
premolar during retraction of the maxillary dentition. The first
microimplant is removed and a second microimplant is placed
distal to the first one.

38. The first microimplant was removed and a second microimplant was
placed just distal to the first one for further retraction of the
mandibular dentition.

39. Microimplant mechanics for retraction of the entire maxillary dentition in combination
with the MEAW technique of Kim(1999b,2000).

40. Microimplant mechanics for retraction of the entire maxillary
dentition of both arches in combination with the MEAW technique
of Kim.

41. Microimplant mechanics for retraction of the entire mandibular
dentition of both arches in combination with the MEAW technique
of Kim.

42. Midpalatal microimplant placement for molar
distalization
The midpalatal area is a good site for microimplant placement
because the palat is covered with relatively thin keratinized mucosa
and has an adequate bone volume. For molar distalization ,
orthodontic force can be applied from a microimplant to the center
portion of a transpalatal arch. If a bracket head type of
microimplant is used in the midpalatal area, a transpalatal arch, can
be inserted directly to the teeth from the transpalatal arch, much in
the same manner as with a pendulum appliance.

43. Various ways of using midpalatal microimplant anchorage. Two
microimplants were joined together with metal plates using light-
cured composite resin, and lingual sheaths were attached to the
metal plates for insertion of transpalatal arches(courtesy of
Dr.S.H.Kyung).

44. In a young patient with an unossified sutural area,
microimplants can be placed slightly laterally. adjacent to the
midpalatal suture. Also, if bracket head type microimplants are
used, a transpalatal wire can be inserted directly into the
bracket slots of the microimplant heads.

45. Protraction mechanics in extraction cases
Sometimes molar protraction is needed in minimum or moderate
anchorage cases or unusual extraction cases. however, molar
protraction is one of the most difficult tooth movements to
accomplish, especially in patients with a low mandibular plane
angle and deep bite. if microimplants are incorporated into the
treatment protocol, molar teeth can be moved forward more
effectively and without disturbing the anterior teeth.
Microimplants for molar protraction are placed between the roots
of mandibular canine and first premolar or first premolar and
second premolar.

46. Microimplant mechanics for molar protraction.

47. Retromolar microimplants for single molar
uprighting
Elastic chain or ligature wire can be connected from a
retromolar microimplant to an attachment on the tipped
molar. These mechanics produce an intrusive force during
molar uprighting and prevent the occlusal trauma that
normaly would occur with conventional uprighting
techniques. However, this type of simple retromolar
microimplant mechanics cannot control the movement of a
tooth precisely.

48. Microimplant mechanics for uprighting a single molar. This type of mechanics
can produce an intrusion force during molar uprighting.

49. Molar uprighting and/or portraction or distalization
mechanics using two microimplants in edentulous area
To resist rotational and torqueing forces, two microimplants
can be placed side-buy-side in an edentulous area and then
joined together using light-cured resin. Subsequently, a
bracket can be bonded to the resin of the microimplant –
supported structure. A rectangular wire inserted into this
bracket will facilitate three –dimensional movement of the
involved tooth.

50. Two microimplants used for molar uprighting.

51. Two microimplants used for molar protraction.

52. Buccal crossbite (scissors bite) correction
To correct a scissors bite without causing molar extruusion, intra-
arch mechanics, rather than interarch mechanics, must be used.
Transpalatal and lingual arch can be used to reinforce anchorage in
conventional intra-arch methods. If microimplants are used, the
same type of uprighting and intrusion is obsarved during buccal
crossbite correction. With only one microimplant, however, it is
difficult to apply orthodontic force in the proper direction; if a
bracket head type of microimplant is selected, a wire can be
extended from the slot of the bracket to allow the force to be
applied more effectively.

53. Schematic diagrams of conventional intra-arch methods used to correct a
scissors bite: transpalatal arch (top); lingual arch(bottom).

54. Conventional methods for correcting a scissors bite often use a transpalatal
and /or lingual arch to reinforce anchorage.

55. Schematic diagram comparing conventional through-the-bite elastics(left)
and microimplant mechanics(right)for correcting a buccal crossbite. Note the
difference between vertical force vectors, i.e., extrusive versus intrusive.

56. Through-the bite elastics extrusion of the posterior teeth, and patients often
experience significant pain during scissors-bite correction. This protocol is not
efficient for the correction of a buccal scissors bite.

57. Microimplant mechanics to correct a scissors bite using bracket head type
microimplants. The bracket head microimplant is very useful in applying
orthodontic force in the proper direction. as the elastic force tends to move
the hooked metal wire occlusally, the bracket head screw tends to rotate in a
clockwise direction. thus the force transferred to the screw tend to insert
deeper into the bone, which serves as a good anti-dislodgment mechanism.

58. Thank you
Thank you