orthodontics, overjet

2. PRESENTED BY:
MD. ISHTIAQ HASAN
FCPS-II TRAINEE,
DEPT. OF ORTHODONTICS,
DDCH
SUPERVISOR:
PROF. DR. MD. ZAKIR HOSSAIN
BDS, PHD(JAPAN)
PROF. & HEAD,
DEPT. OF ORTHODONTICS,
DDCH.

4. PT NAME: FATEMA
AGE: 24 YRS

5. LEFT AND RIGHT PROFILE VIEW

6. CHIEF COMPLAIN:
SPACING IN UPPER &
LOW JAW

7. MODEL ANALYSIS
UPPERJAW : 12 mm SPACING
LOWERJAW: 10 mm SPACING

8. DIAGNOSIS
• It is a case of ant. open bite with spacing
in upper and lower jaw .

9. TREATMENT PLAN
APPROXIMATE 12 12
12 12
THEN ?

10. ARCH
CONTRACTION
OR
PROSTHESIS ?

12. NASO-LABIAL ANGLE
For each mm of incisor retraction, 1.6 ° increase of naso-labial angle.
94°
Normal=102 +/- 8°

13. LABIO-MENTAL ANGLE
123°
Normal=122+/- 11.7°

14. The lips will move two-thirds of the
distance that the incisors are retracted , i.e.
, 3 mm of incisor retraction will reduce lip
protrusion by 2 mm , but only until
competence is reached. Beyond that
point , further retraction of the incisors
will not further reduce lip prominence.
---------- PROFFIT

15. 1 mm of lower incisor retraction resulting in
1 mm of lower lip retraction and on
average, 3 mm of upper incisor retraction
is needed for 1 mm of upper lip retraction.
--------BURSTONE

16. LETS TAKE A LOOK WHAT OTHER
BOOKS TELL US ABOUT THIS
TREATMENT PLAN

17. OVERJET REDUCTION

18. The following four dental and skeletal non-surgical
changes are responsible for overjet reduction----
Mesial movement of lower incisors
Distal movement of upper incisors
Distalizing or limiting forward growth of maxilla
Mesial movement of mandible by---(a)forward
mandibular growth or (b) limiting vertical
development
The first two changes involve dental tooth movement , while the last
two involve skeletal changes. In adult , non-growing patients , such
skeletal changes must be carried out surgically.

19. Overjet reduction from mesial
movement of lower incisors.
Overjet reduction from distal
movement of upper incisors.

20. Overjet reduction from mesial
movement of mandible
resulting from condylar
growth.
Overjet reduction from distalizing
or limiting forward growth of
maxilla.

21. Overjet reduction from mesial movement of
mandible by limiting development.

22. Mesial movement of lower incisors
The end treatment position of lower incisors is
important for several reasons ----
If lower incisors are too far back , then there is a
tendency to a retrognathic profile and a long
term deepening of overbite.
If the lower incisors are too far forward , then
there is a undue fullness of facial profile and
possibility of instability of lower labial segment
,as incisors drop back towards the tongue in
response to lip pressure.

23. If the lower incisors are left too
far back , there is a tendency to
a retrognathic profile and a long
term deepening of overbite.
If the lower incisors are left too
forward , there is a tendency to
undue fullness of the facial
profile and possibility of
instability of lower labial
segment.

24. The ideal position of
lower incisors should
be 2 mm infront of
APo line.

25. • At the end of
treatment , there
should be 90-95°
angulations between
lower incisors and
mandibular plane.

26. • There is usually a soft
tissue involvement when
require mesial movement
of lower incisors. For
example , if there is a
history of thumb sucking
activity or hyperactive
mentalis muscle function
where lower incisors have
been held back and
retroclined. In these
cases , it is mechanically
appropriate to move the
lower incisors forward.

27. • cl-II div 2 treatment sometimes involve the
mesial movement of lower incisors. There is
often soft tissue element to such cases , where
the high lip line with lip activity has retroclined
both upper and lower incisors.
During routine mechanics after the
incisors have been moved forward to create a cl-
II div 1 pattern with an overjet , it is frequently
found that the lower incisors are back in the
profile. It is then appropriate to tip the lower
incisors forward .

29. Distal movement of upper incisors
• The ideal position of
upper incisors should
be 6 mm infront of
APo line with an
angulation of 110 ° to
the maxillary plane

30. Traditionally distal movement of
upper incisors has been
regarded as the main method
of correction of cl-II div1
malocclusion. However , since
it has been shown that true
maxillary protrusion occurs in
only about 20% cases ,
changes involving mesial
movement of chin point are
preferable for facial profile
reasons. In adults , this implies
orthognathic surgery to the
maxilla or the mandible.

31. • Where the
commencing upper
incisor angulation is
above 115° , the initial
retraction is often
achieved by a tipping
type of movement
until normal
angulation is
reached , and then
bodily movement is
attempt.

32. Distal movement or limiting forward
growth of maxilla
Assessment of the position
of maxillary bone may be
measured by---
 the SNA angle favoured
by Steiner and
 Dropping a perpendicular
line from Nasion to
Frankfort plane and using
a normal of 0 mm for A
point , as recommended
by McNamara.

33. • When it is clear that increased overjet is due to a
forward position of maxillary bone , it is
appropriate to attempt to use orthopedic
headgear or class II elastics to influence
maxillary growth in the growing individual. The
distalization of the maxilla itself is difficult and
require good co-operation with heavy orthopedic
forces. Usually such forces to the maxilla will
limit its forward growth , which would be
approximately 1 mm per year in a growing child.

34. Mesial movement of the mandible
• Normal position of
mandible is 4 mm
behind the Nasion
Frankfort
perpendicular line
(McNamara).
• Also SNB angle of 80°
as recommended by
Steiner can be used as
a reference for
horizontal mandibular
position .

35. • Mesial movement of the mandible also can be achieved
by limiting of vertical growth.
Any mechanical process which reduce or maintain
the MM angle will producee mesial movement of
pogonion in the facial profile. The use of high pull head
gear , palatal bar , lingual arch and post bite plate favor
control of this type. Also , the extraction of premolar
teeth makes vertical control easier.
Use of inter-maxillary elastics in high angle cases,
as well as, cervical headgear and ant. Bite plate tends to
open the MM angle and produce unfavourable change in
the position of pogonion. Non-extraction treatment also
makes it difficult to prevent the MM angle opening.

37. MM angle tends to open in response to—
• non-extraction treatment
• cervical headgear
• prolonged intermaxillary elastics
• ant bite plate
MM angle tends to close or be maintained in
response to---
• extraction treatment
• high pull headgear
• palatal bar and lingual arches
• post. Bite plate

38. In cl-II div 1 cases with increased MM angle ,
vertical control is important to reduce the
angle or at least prevent it from increasing.
Pogonion will move distally in the profile if MM
angle is allowed to increase .
•In summery, an understanding of the
importance of vertical factors is essential
to proper management of overjet
reduction.

39. THE MECHANICS OF OVERJET REDUCTION
There are primarily 3 methods used to correct cl-II
molar relationship and reduce overjet---
Cl II elastics
Headgear
Functional appliance
These 3 primary methods can be used separately
or in combination and ultimately their correct use
is the key to a successful result.

40. CLINICAL EXAMPLES

41. EXAMPLE A:  Lower arch
contraction
finished and the
lower incisors
are good
position in the
facial profile.
 Upper incisors
torque is correct
 3 mm excess
overjet to close
 overbite is
properly
controlled
 6 mm of upper
extraction need
to close
 Molar
relationship 3
mm cl-III
6 mm
3 mm
3 mm

42. TREATMENT PLAN:
 The remaining 6 mm of upper space
may be closed by reciprocal space
closure , using sliding mechanics ,
because molar relationship is cl-III. The
molars and premolars will move mesially
by 3 mm as the canines and incisore
move distally by 3mm.
 Night time head gear support can be
use if the molars move forward more
rapidly than anteriors.
The rectangular wire will allow bodily
control of the upper incisors , provided
force levels are light.
6 mm
3 mm 3 mm

43. 6 mm
3 mm 3 mm

44. EXAMPLE B:
Lower incisors are in
good position in facial
profile
Upper incisor torque
is correct
4 mm of excess
overjet to reduce
molars are Cl-I
4 mm of upper
extraction space to
close.
4 mm
4 mm

45. TREATMENT PLAN:
 The remaining space should
not be closed by reciprocal
space closure , because molar
relation is cl-I and it will
change into cl-II because
molars and premolars will tend
to move mesially as the
canines and incisors moved
distally.
 Support from a sleeping head
gear or a palatal bar is needed
to protect the molar
relationship during overjet
reduction.
4 mm
4 mm

46. 4 mm
4 mm

47. EXAMPLE C:
Lower arch space closure
finished.
But lower incisors are set
back by 2mm in facial profile
Upper incisor torque is
correct
4 mm of upper extraction
space need to close
4 mm of overjet need to be
reduced
molar relationship Cl-I
4 mm
4 mm

48. TREATMENT NEED:
 The remaining space can be
closed by reciprocal space closure
with Cl-II elastics which will protect
the molar relationship by bringing
the lower arch forward to a
position close to APo +2mm.
 In upper arch , the molars and
premolars will move mesially by
2mm as the canines and incisors
move distally by 2 mm.
 Here MM angle is 28° (average) ,
so Cl-II elastics can be used.
INTERMAXILLARY ELASTIC IS CONTRAINDICATED IN HIGH ANGLE CASES.
4 mm
A HIGH PULL HEADGEAR IS NORMALLY PREFERRED FOR UPPER MOLAR SUPPORT
DURING OVERJET REDUCTION IN HIGH ANGLE CASES.
4 mm

49. 4 mm
4 mm

50. EXAMPLE D:
 Lower arch space
closure finished.
 Lower incisor is good
position in facial
profile.
 Upper incisor torque is
not correct , they are
proclined at 122°
 7 mm of overjet to
reduce
 7 mm of upper
extraction space to
close
 Molars are Cl-I
7 mm
7 mm

51. TREATMENT PLAN:
 The remaining space should
not be closed by reciprocal
space closure as Cl-I molar
relationship will be lost.
 Excess 10° tipping can be
corrected by round wire first ,
then rectangular wire can be
used for bodily movement.
 If a large overjet needs to be
closed , rectangular wire is
essential and support from a
sleeping headgear or palatal
bar will definitely needed,
otherwise molars will come
forward and molar relationship
will lost.Also force level should
be low.
7 mm
7 mm

52. EFFECT OF TOO RAPID SPACE
CLOSURE----
 Reduced torque control when space
closure more than 1.5 mm/month
 Rapid mesial movement of upper molar
followed by palatal cusp hang down.
 Lateral open bite
 Soft tissue hyperplasia at extraction site.

53. 7 mm
7 mm

54. EXAMPLE E:
Lower arch appear to be
finished
Lower incisors set back
in the facial profile
Upper incisors torque is
correct
3 mm excess overjet to
correct
Molars are 2 mm Cl-II
3 mm
2 mm

55. TREATMENT PLAN:  Tieback are placed to hold the upper and
lower spaces closed.
 3 mm of overjet may be reduced by Cl-II
elastics , as MM angle is average (28°)
 The upper arch act as an anchorage unit
with teeth ligated to a rectangular wire.
 The lower incisors are at 89° and can
therefore be allowed to tip forward by
upto 6°
 As the overjet reduces , the lower teeth
move mesially and molar move in Cl-I
relationship
 The tips of the lower incisors can be
expected to move mesially more than the
lower molars do (3 mm compared to 2
mm) , because part of the incisor closure
involve tipping. The lower rectangular
wire can carry a little labial crown torque
in the incisor region to assist forward
tipping of incisors.
2 mm 3 mm
EVERY 2.5° PROCLINATION , MOVES THE LOWER INCISOR EDGE FORWARD BY 1 MM
(RESULTING IN SPACE GAINS OF 2 MM FOR EVERY 2.5° OF PROCLINATION).

56. 2 mm 3 mm

57. EXAMPLE F:
 Cl-II div 1 cases with
extraction of all four
bicuspids.
3 mm of lower extraction
space need to close.
4 mm of upper extraction
space need to close
4 mm of overjet need to
close
Molars are 3 mm Cl-II
4 mm
4 mm
3 mm
3 mm

58. TREATMENT PLAN:
 4 mm of overjet may be reduced
by Cl-II elastics as MM angle is
average (28°)
 Sleeping hadgear is necessary ,
otherwise upper molar will come
anteriorly.
 Cl-II elastics causes lower molars
and premolars to move mesially ,
thus helping 3 mm of lower
extraction space closure and 3
mm of molar relationship to be
corrected.
 Month by month monitoring is
needed and good patient co-operation
is needed.
 Upper second molar should be
included.
4 mm
4 mm
3 mm
3 mm

59. 4 mm
4 mm
3 mm
3 mm

60. EXAMPLE G:
Cases with extraction of
all 4 bicuspids
Lower incisors are 2 mm
forward position than ideal
position
4 mm of overjet to
reduce
4 mm of upper and
lower extraction space to
close
Molars are 4 mm Cl-II
4 mm
4 mm
4 mm
4 mm

61. TREATMENT PLAN:
• cl-II elastic can not be
used as it is a high angle
case.
• upper labial segment
move distally by 6 mm
• headgear support is
needed for 2 mm upper
molar distalization
• lower space closure will
need to be reciprocal ,
with molar traveling
mesially by 2 mm and
incisors going distally by
2 mm
4 mm
4 mm
4 mm
4 mm

62. 4 mm
4 mm
4 mm
4 mm

63. EXAMPLE H:
Non-extraction
case
Lower incisors set
back 1 mm in facial
profile
Upper incisors
torque is correct
3 mm overjet to
reduce
Molars are 3 mm
Cl-II
3 mm
3 mm

64. TREATMENT PLAN :
 Only a reduced amount od Cl-II
elastic traction is needed to
reduce the overjet and headgear
support to the upper first molar is
essential for distalization of 2 mm.
 A headgear during sleeping and
Cl-II elastics during the day time
can be used. This will give a 24
hour distalizing force on the upper
arch and only a 12 hours of
mesializing force on lower molars.
 The lower rectangular wire has
additional lingual crown torque in
the incisor region to resist forward
tipping movement of the incisors.
Lower teeth should be ligated
hard.
3 mm
3 mm

65. 3 mm 3 mm

66. EXAMPLE I:
 Cl-II div 1 malocclusion
 Molar 7 mm Cl-II
 OJ 7 mm
7 mm
7 mm

67. TREATMENT PLAN:
Cervical pull headgear on upper
arch for 14 hours per day , usually
when pt is at home and sleeping
Cl-II elastics with an upper sliding jig
for 10 hours per day

68. After 6 mm of molar
distalization , upper
cuspids and bicuspids are
bracketed
Headgear continue to wear 14
hours per day to initiate overjet
reduction
During day time, 10 hours of
Cl-II elastics are worn to the
hooks on archwire rather than
to the sliding jig to complete
overjet reduction
A 24 hour of force is applied to the upper arch to complete the molar
relationship first & then to complete overjet reduction & only an intermittent
force of 10 hrs per day is applied to the lower arch with Cl-II elastics

69. 7 mm
7 mm

71. 8
7
6
5

72. • NEITHER FULL ARCH CONTRACTION
NOR PROSTHESIS

73. THE MORE VERTICAL THE UPPER INCISORS ARE, THE MORE
TORQUE IS NEEDED.

75. BEFORE AFTER

76. BEFORE AFTER

77. NASO-LABIAL ANGLE
94°
Normal=102
+/- 8°
104°
BEFORE AFTER

78. MENTO-LABIAL ANGLE
137°
123°
Normal=122+/-
11.7°
BEFORE AFTER