Open bite

openbite causes and management

1. Open Bite
Dr Alaaelkasaby
Under supervision of
Dr Maher Fouda
Mansoura Egypt
Professor of orthodontics

2. Definitions
Classifications of Open Bite
Anterior Open Bite (AOB)
-Incidence
-Etiology
Posterior Open Bite (POB)
-causes
Diagnosis and Treatment of Open Bite
---Diagnostic Tests-AOB
---Indication for Treatment of Open Bite
---Management of AOB
-Treatment modalities
Retention for AOB
Stability for AOB
Seminar Outline:

3. Definitions
Open Bite( Negative Overbite):
-Inherited ,developmental or acquired maloccluison
(vertical occlusal anomaly) whereby no vertical overlap
exists betweenmaxillary and mandibular anterior teeth
( anterioropen bite-AOB-)when posterior teeth are
brought in to maximum intertcuspation ,or no vertical
contact is exhibited between maxillary and mandibular
posterior teeth (posterioropen bite-POB-).An open bite
may be localized and thus involve only a few teeth due to
a digit sucking habit or other local factors(dentalopen
bite),or it may be caused by divergence of the skeletal
planes (skeletalopen bite or apertognathia).

4. Definitions
Vertical overlap of Incisors
Anterior open bite (AOB): there is no vertical overlap of the incisors
when the buccal segment teeth are in occlusion
Posterior open bite (POB): when the teeth are in occlusion there is a
space between the posterior teeth
Incomplete overbite: the lower incisors do not occlude with the upper
incisors or the palatal mucosa . The overbite may be decreased or
increased
Increase Over bie(o/b)Normal o/b Incomplete o/b AOB

5. .Posterior open bite.
.Anterior open bite.
Incomplete overbite .Anterior open bite.

6. Classifications of Open Bite
According to Moyers 1988 it can be classified in to:
1-Simple(Dental,functional) open bite:
Anterior or Posterior
2-Complex ( Skeletal) open bite:
which could be associated with
Class I ,Class II or Class III skeletal discrepancies

7. Classifications of Open Bite
A simple clinical diagnostic classification might be
as follows:
•1anterior open bite with increased facial
proportions
•2anterior open bite with history of digit
sucking and normal facial proportions
•3anterior open bite with no history of digit
sucking and normal facial proportions
EXCELLENCE IN ORTHODONTICS 2005

8. Anterior Open Bite (AOB)
Incidence:
1-2% of general population (Haynes 1970)
3.5 % 8-17 yrs old patients (Proffit et al 1988)
Incidence varies with:
Race : Black >White (Black American 16% Kelly
et al.1973)
Age: younger >Older
Neurological disorder>normal

11. AOB
Etiology :
1-Transitional
2-Skeletal
3-Habits
4-Soft tissues
5-Trauma
6-Iatrogenic
7-Mouth breathing & Head posture
8-Neurological disturbances.
9-Localized failure of development
10-Muscular dystrophy.

12. AOB
Etiology:
1-Transitional:
during eruption of teeth, patients are children
in the transitional dental stage, it is conceivable
that the rate of eruption of the anterior teeth will
slow down temporarily. These subjects are
often referred to as having "transitional or
pseudo open-bite".

13. 2-Skeletal: Discrepancy in vertical development
Anterior & PosteriorBackward Rotation (Bjork)
Skeletal features:
-1-Increased LAFH and there may be vertical maxillary
excess (supragnathism), ‘long face syndrome’ or
Ricketts’ dolichofacial type(1961).
-2-Steep mandibular plane & gonial angle.
-3-Reduced posterior FH.
-4-Divergent cephalometric planes (sassouni analysis)
In these cases AOB is usually symmetrical and in severe
cases only terminal molars contact.
Etiology
Clinical Success in early orthodontic treatment 2005

14. Etiology
2-skeletal
The Frankfort Mandibular Planes Angle (FMPA) is
usually increased. In contrast to open bites caused
purely by habit, in which there is impedance of incisor
eruption by the digit, in true skeletal open bite incisor
eruption may be increased in relation to the underlying
basal bone, although it still fails to compensate for the
excessive vertical development of the jaws.

15. Dung and Smith reported that, in 250 patients who
exhibited traditional cephalometric indicators of an
excessive vertical dimension, such as an increased
FMPA or LAFH, only 13% had actual anterior open
bites. They concluded that, in growing patients, an open
bite tendency is in large part synonymous with a
backward rotation to mandibular growth. Hence,
attention to the structural features as identified by Bjork
may be more useful than conventional cephalometric
analyses in predicting how patients will grow and how
they will respond to orthodontic treatment.
Dung DJ, Smith RJ. Cephalometric and clinical diagnoses of open bite tendency. Am J
Orthod Dentofac Orthop 1988; 94: 484–490.

16. Bjorkidentified seven
structuralsigns related to
significantly abnormal
mandibular growth rotations:
inclination of the condylar head;
curvature of the mandibular
canal;
shape of the lower border of
the mandible;
inclination of the symphysis;
interincisal angle;
interpremolar or intermolar
angle;
lower anterior face height.
Dental Update –June 2003

17. 3-Habits:
( Duration & Intensity)
Thumb sucking
Digit sucking
Dummy sucking( sucking
the pacifier)

18. This open-bite is caused by obstruction of
eruption of the anterior teeth. Classically, this
open-bite is asymmetrical and fits snugly around
the offending agent. Many of these cases show
spontaneous remissions , and about 75 to 80% had
marked improvement without any form of
treatment.

19. Digit sucking is a common cause of AOB .The
incidence of digit sucking is around 30% at 1
year of age, reducing to 12% at 9 years and 2%
by 12 years. Most persistent suckers are
female. The influence made by the digit
depends on the age of the patient and the
intensity, frequency and duration of the habit.
Open bites produced in the primary dentition
are of little consequence as they resolve
spontaneously once the child gives up the habit
.The thumb or finger effectively acts as a barrier
to the incisors erupting, whilst allowing
excessive eruption of the posterior teeth.

20. The upper incisors are invariably proclined whereas
the effect on the lower incisors is more variable. Not
infrequently there is a crossbite due to narrowing of
the upper arch. How much the teeth are displaced
correlates better with the number of hours per day of
sucking than the magnitude of pressure. Children
who digit suck for 6 hours or more each day,
particularly those who sleep with a digit between the
teeth all night, can develop a significant
malocclusion. There is some evidence that, as well
as dento-alveolar effects, persistent digit sucking
can have a minor effect on the skeletal pattern,
causing tilting of the maxillary plane in an anti-
clockwise direction and anterior displacement of the
maxilla. However, if the habit ceases during growth
the underlying growth pattern will be re-established.

21. 4-Soft tissues:
A -Tongue posture & Function:
All AOB exhibit anterior tongue thrust,but not all AOB
are caused by anterior tongue thrust.
Two Condition exists:
i-adaptive tongue thrust( secondary)
ii-endogenous tongue thrust (primary)rare
& difficult to distinguish
Features (to differentiate):-size of AOB
-incisors inclination
-mandibular curve of spee
-speech stigmatism (Lisping)
-poor motor control
-force of tongue thrust
-absence of gag reflex
(unexplained ,may be neurological)
Etiology

22. A -Tongue posture & Function:
The cause and effect relationship of abnormal tongue function
and open-bite is not clear.
This controversy still rages on because little scientific evidence
exists to establish the relationship. However, Cookereported
that young patients possessing anterior open-bite are
frequently presented with large tongues. Evidence also
suggests that in some cases, the aberrant tongue and tongue
behavior known as "endogenous tongue thrust" are the actual
cause of the anterior open-bite. The population of children
with such endogenous tongue thrust behavior is small (0.6%)
and they often demonstrate lisping with open-bite larger than
would be expected with a tongue to lower anterior oral seal
and also with excessive muscular activity around the lips
during swallowing.

23. Proffit suggested that the resting position of the
tongue has much greater influence on tooth position
than any tongue thrust, as the duration of any
thrusting activity would be too short to have a
significant effect. When the tongue is naturally kept in
a forward position, overlying the lower incisors then a
reverse curve of Spee is present in the lower arch,
which is particularly apparent on a lateral
cephalogram. This is often a warning sign that closure
of the AOB is unlikely to be stable owing to the
adverse soft tissue pattern. Tongue reduction is
sometimes considered in these cases, especially if it is
abnormally large (macroglossia).
Dental Update –June 2003

24. Etiology
B-Lymphatic tissues:
Large adenoid Mouth breathing Mandible
postured downward separation of posterior teeth
over eruption increase in Lower Vertical
Dimension Open Bite
The ‘Adenoid face’consists of a narrow face,
protruding teeth, and lips separated at rest, and has
often been attributed to chronic mouth breathing.

25. 5-Trauma (pathological) :
-Bilateral fractured of the condyles.
-Ankylosis of Condyles
-Le Fort II and III fracture cases often present
with gagging occlusion, hence anterior open-bite.
Etiology

26. Etiology
6-Iatrogenic:
-This open-bite is produced by active orthodontic treatment
obviously represent examples of poor treatment techniques, Poor
mechanics or inappropriate treatment planning.
More common mistakes in this category include:
1-the use of anterior bite plane in already reduced overbite
and the extrusion of upper molars in high angle cases.
Failing to prevent overeruption of second molars when
biteplanes or functional appliances are used may also
give rise to an AOB.
2-when High canines is engaged during alignment
3-Poor mechanics during fixed-appliance treatment may
cause extrusion of the molar teeth or ‘hanging’ palatal
cusps, which open the bite.

27. 7-Mouth breathing & Head posture:
--Mouth breathing (due to Nasal obstruction or Habit):
This per sedoesn’t play significant role in the development of AOB
--Head posture :Related to breathing: mouth breathing
extension of head stretch muscles increase
vertical dimension
Studies have shown that when the nose is completely
blocked, there is usually an immediate change of about 5°in
the craniovertebral angle . The jaws move apart as much as the
elevation of the maxilla because the head tips back by the
depression of the mandible. This was described by Solow and
Kreiborg as the soft tissue stretching hypothesis
Etiology
International Journal of Paediatric Dentistry 2007

28. Etiology
8-Neurological diturbances:
Neurological disorders contribute to the
development of anterior open-bite. Gershater
demonstrated a very high incidence (32.3%) of
anterior open-bite in his survey of mentally
retarded and emotionally disturbed children. This
supports other studies where problems in
controlling the tongue at rest or in function are
encountered.

29. Etiology
9-Localized failure of development:
In patients with cleft lip & alveolus ,although rarely it
may occur for no apparent reasons. Pathological
conditions may also present as anterior open-bite,
such as in cleft palate, acromegaly.

30. Etiology
10 -Muscular Dystrophy
The decrease in tonic muscle activity that occurs in
muscular dystrophy allows the mandible to rotate
downwards away from the rest of the facial skeleton,
resulting in increased anterior facial height, a posterior
growth rotation of the mandible,
excessive eruption of the posterior
teeth, narrowing of the maxillary arch
and AOB that worsens with growth.

31. Posterior Open Bite
Posterior open bite occurs more rarely than
anterior open bite and the aetiology is less well
understood. In some cases an increase in the
vertical skeletal proportions is a factor, although
this is more commonly associated with an
anterior open bite which also extends posteriorly.
A lateral open bite is occasionally seen in
association with early extraction of first
permanent molars, possibly occurring as a result
of lateral tongue spread. Posterior open bite is
also seen in cases with submergence of buccal
segment teeth.
An Introduction to Orthodontics , 2nd Edition 2001

32. Posterior Open Bite
There are two rare conditions which affect the eruption of
the permanent buccal segment teeth:
1-Primary failure of eruption: this condition almost exclusively
affects molar teeth and is of unknown aetiology. Although bone
resorption above the unerupted tooth proceeds normally, the tooth
itself appears to lack any eruptive potential . Extraction is the only
treatment alternative. The aetiology is not understood.
2-Arrest of eruption: this also usually involves molar teeth. Affected
teeth appear to erupt normally into occlusion, but then subsequently
fail to keep pace with occlusal development. As growth of the rest
of the dentition and alveolar processes continues, lack of movement
of the affected tooth or teeth results in relative submergence . The
aetiology is not understood and again the usual treatment is
extraction of the affected tooth or teeth.
An Introduction to Orthodontics , 2nd Edition 2001

33. Posterior Open Bite
3-More rarely, posterior open bite is seen in association
with unilateral condylar hyperplasia, which also results
in facial asymmetry. If this problem is suspected, a
bone scan will be required. If the scan indicates
excessive cell division in the condylar head region, a
condylectomy alone, or in combination with surgery to
correct the resultant deformity, may be required.

34. Diagnosis and Treatment
Clinical assessment should include accurate medical
and dental history in addition to cephalometric and
study model analyses if one is to differentiate between
various types of anterior open-bite. Treatment
planning must be based on the assessment and
evaluation of every individual case which may be
unique. Some cases may undergo spontaneous
improvement without any treatment.A variety of
treatment philosophies and appliance techniques have
been used in the correction of anterior open-bite.

35. Diagnostic Tests-AOB
1-ODI(Overbite Depth Indicator)(Kim Y H 1974):
American Journal of Orthodontics 1974; 65:586-611
The Angle A-B planes makes with the mandibular plane
combined with the angle of palatal plane to FH .
The angle formed by palatal plane and FH is either added
(if +ve)to or subtracted (if -ve)from MP/A-B plane
The angle is negative if palate is tipped down posteriorly
or positive if the palatal plane is tipped down in front
A value of less than 68 degrees is said to indicate over
bite tendency .

36. Diagnostic Tests-AOB
1-ODI(Overbite Depth Indicator) [Example]:
(MP-AB). (Example: 76°).
Measure the angle of the (FH), and (PP). In case of a positive
value, write it in the corresponding positive rectangle, otherwise,
write it in the corresponding negative rectangle (Example: -3°)
Combine these values to obtain the Overbite Depth Indicator (76°-
3°=73°).In this example the ODI is 73 degrees,which is slightly
lower than the norm (74.5°, 6°); howerver, the diference is 1.5°.
Considering the standard deviation, it falls within the normal limit
with a sligth tendency to be an openbite
The Orthodontic CYBERjournal 2004

37. Diagnostic Tests-AOB
2-Dung & Smith (1988) on cephalometric & clinical
diagnosis of AOB :Dung DJ, Smith RJ. Cephalometric and
clinical diagnoses of open bite tendency. J Orthod Dentofacial
Orthop. 1988; 94:484–490
SN/MP≥ 40 degrees
OP/MP ≥ 22 degrees
Max/Mand ≥ 32 degrees
AOB –ve
PFH/AFH ≤ 58%
UAFH/LAFH ≤ 0.70
Success rate of the diagnostic tests varies from 12%(Jaraback
ratio) -62%(ODI)

38. Diagnostic Tests-AOB
Sassouni and Nanda and Nahoum reported
that the angle between the sella-nasion plane and
the palatal plane was significantly reduced in
their sample while Frost and associates,
Subtenly and Sakuda , Enunlu and Lowe
showed no significant difference in this
angle,which suggested that open-bite deformity
arises inferior to the palatal plane. Another area
of agreement among the many investigators
who studied skeletal open-bite is the statistically
significant increase in the angle between the
sella-nasion plane and the occlusal plane.

39. INDICATIONS FOR TREATMENT
Patients seek treatment mainly on aesthetic grounds.
However, there may be functional problems such as
difficulty incising food and problems with speech, such
as a lisp. Although closure of an AOB may help with
eating, there is little evidence to show that it helps with
speech, and certainly this should not be promised to
the patient. The Index of Orthodontic Treatment Need
(IOTN) is commonly used in the hospital service, and
may in the future be used in the General Dental
Services, to determine the needs of patients for
orthodontic treatment. Only patients with an AOB
greater than 4 mm fall into the ‘need’ treatment
category (IOTN 4). An AOB less than 4 mm would be
borderline or be considered not to be in need of
treatment, unless some other aspect of the
malocclusion took precedence.

42. Management of AOB
Many orthodontists are concerned about the difficulties
of management of high angle and open bite cases. The
underlying implication is that the establishment of a normal
overbite may be difficult in such cases. In reality, the term
high angle covers a number of conditions that include the
long face syndrome, posterior growth rotation, anterior
open bite and open bite tendency.
Betzenberger et al (1999) have shown that considerable
dentoalveolar compensation may occur in individuals with
high angle malocclusions which they defined as those
having a SN/MP angle ≥40°. Of the 191 subjects, 50%
had a normal overbite (0-4 mm), 30% had a deep overbite
(>4 mm) and only 20% had an open bite (<0 mm).
Skeletally, the open bite group had SN/MnP and an
MxP/MnP angles which were 3.2°higher than those in the
deep bite group.
EXCELLENCE IN ORTHODONTICS 2005

43. Management of AOB
The key to the management of open bite tendency:
1-Eliminate the etiology.
2-Avoidance of extrusion of posterior teeth.
3-Intrusion of molars rather than extrusion of incisors.
Treatment modalities:
1-No active treatment.
2-Habit breaker
3-Orthopedic appliances (myofunctional therapy)& Removable
appliances with bite blocks.
4-Fixed appliances.
5-Camouflage
6-Surgery & Implants( microscrew ,miniplate, distraction
osteogenisis & orthognathic surgery)
7-combination of two or more of the above.

44. 1-No active treatment
In this case treatment is aimed at relief of any crowding and alignment
of the arches. This approach can be considered in the following
situations (particularly if the AOB does not present a problem to the
patient):
1-mild cases.
2-where the soft tissue environment is not favourable, for
example where the lips are markedly incompetent and/or an
endogenous tongue thrust is suspected.
3-in more marked malocclusions where the patient is not
motivated towards surgery.
4-when anterior open bite is transitional due to partially erupted
incisor teeth
5-As first stage treatment in patients with sucking habits

45. 1-No active treatment
As first stage treatment in patients with sucking habits:
In the deciduous dentition, unless there is evidence
of trauma, the AOB is most probably due to a habit
such as dummy or digit sucking. No intervention is
indicated apart from encouraging the child to stop the
habit. As the patient gets older (and providing the
habit stops) a significant proportion of cases improve
spontaneously, usually during the changeover from
the mixed to the permanent dentition. However,
normalization of the overbite can take between 3 and
5 years.

47. 2-Habit breaker
The treatment of non-skeletal open-bite in which
the child indulges in some form of non-nutritive
sucking should include adequate effort to dissuade
him from this habit, although most clinicians tend
to agree that intervention is not usually indicated
until about the age of 5 years when the permanent
dentition starts to erupt.
Proffit and Fields suggested a system whereby a
small tangible reward is provided daily for not
engaging in the habit. Other method of interrupting
such a habit, especially during sleep and other
recreation, is by placing a cotton glove on the
hand or a band-aid on the thumb or finger .Taping
a rolled up tea towel to the inside of the elbow as a
reminder often works well.

48. 2-Habit breaker
A child who is still sucking his/her thumb as the upper
permanent incisors erupt (7.5–9 years) should be
actively discouraged from doing so. Initially this
should take the form of advice, possibly in
conjunction with an aide memoiresuch as a plaster
on the associated finger, a glove or foul-tasting nail
polish. Alternatively, a small tangible reward can be
offered on a daily basis for not engaging in the habit.
If this is ineffective but the child wants to stop the
habit, a deterrent appliance can be used. The
appliance is either a removable or a fixed appliance
which prevents sucking of the digit, and must be
retained in place for a minimum of 6 months after
sucking has apparently ceased, to ensure the habit
has truly stopped .

49. 2-Habit breaker
Fixed habit breaking devices for control of digit
sucking and anterior tongue thrusting are used by a
number of general dental practitioners and
pedodontists .One of such appliances is the use of
quadhelix which facilitates expansion of the
constricted maxillary arch as well as discourages the
habit. Quadhelix appliance often causes buccal tipping
and extrusion of lingual cusps of molars resulting in
further increase of open-bite in the anterior region.
This side effect is minimized by actively tipping the
bands on the appliance lingually to counteract this
undesirable effect.

50. Removable appliances could be useful but are not
usually recommended because of its non-compliance.
Force should not be used to break the habit because
of psychologic problems .The use of dummy sucking,
which is more socially acceptable, has proved to be a
better alternative. Larsson demonstrated that children
who sucked dummies stopped using them by the age
of six years and showed no tendency to suck digits,
whereas the group that sucked digits continued with
the habit in significant number according to age-
groups that are socially unacceptable and
orthodontically harmful. ‘Orthodontic’ dummies are
now available; these flatten on use, thus preventing
undesirable effects on the deciduous occlusion. The
child, however, does not always accept such
dummies. Larsson E.Dummy and finger-sucking habits with special attention to their significance
for facial growth and occlusion. 1. Incidence study. Sven Tandlak Tidskr 1971; 64: 667–672.

51. Use of a tongue guard has been advocated as a
means of treating an AOB in a patient with a tongue
thrust: this frequently allows spontaneous correction
of the AOB, providing it is not skeletal in nature.
Stability depends on the thrust being adaptive rather
than endogenous.
Proffit and Masonsuggested limiting use of tongue
guards to patients who have reached puberty, as up to
80% of children who have a tongue thrust and AOB at
8 years showed improvement without therapy by age
12.
Proffit WR, Mason RM. Myofunctional therapy for tongue-thrusting: background and recommendations. J Am Dent Assoc 1975; 90: 403–411.
2-Habit breaker

52. These methods are likely to produce good
spontaneous resolution of the AOB in a pre-teen
patient, but in an older patient the proclined upper
labial segment is held forwards by mesial
movement of the buccal segments, and the AOB
may be maintained by the soft tissue pattern
and/or failure of further alveolar development
anteriorly. This is supported by Larsson, who
reported that, when the sucking habit is prolonged
beyond the pubertal growth spurt, the open bite will
not usually correct spontaneously.
2-Habit breaker

53. In this case further orthodontic treatment may be
indicated . However, it isessential that any digit
habit is stopped first, otherwise not only will the
treatment be unsuccessful, but there is also a risk of
root resorption of the upper incisors due to the
competing forces to which they will be subjected.
2-Habit breaker

54. 2-Habit breaker
Proffit’s protocol
Dent Update 2003; 30: 235-241

55. 2-Habit breaker
Designs:
Palatal crib
(Removable or
Fixed appliance)
Tongue guard
Quad helix
Goal post
Crib appliance prevents suction in palate

56. Goal Post

57. Quad helix function with tongue/thumb
habit reminder
Quad helix with more aggresive habit
function

58. Vertical crib appliance traps tongue thrust
Dillingham I

59. Mandibular tongue thrust appliance Dillingham Habit

60. Bead appliance to train tongue to proper
position
Palatal crib with a bead to train proper tongue
position

61. 3-Orthopaedic & Removable
appliances
a-Posterior bite blocks, Twinblock, Elastic
activator & Active vertical corrector
b-Frankel -4
c-Extra-Oral traction: High pull headgear &
Vertical pull chincup.
d-palatal crib and high-pull chin cup therapy

62. a-Posterior bite blocks, Twinblock, Elastic
activator & Active vertical corrector
Removable maxillary intrusion splints which carry
posterior bite blocks are very useful in closing
anterior open-bite. Passive posterior biteblocks are
functional appliances that are used to open the bite
3–4 mm beyond the rest position. In growing
patients this inhibits the increase in height of the
buccal dento-alveolar processes, thus preventing a
downwards and backwards rotation of the
mandible; it also allows differential eruption to
occur as the labial segments can erupt unhindered,
hence closing the AOB.

63. a-Posterior bite blocks, Twinblock, Elastic
activator & Active vertical corrector
Functional appliance with bite blocks, such as
Clark's twin block (CTB) and Bionator, have also
proved valuable in the vertical control of molars.
Both techniques carry extraoral tube for the use
of headgear.
Regardless of whether the mandible is brought
forward in the working bite, the bite must be
opened past the normal resting vertical
dimension if molar eruption is to be affected

64. Recently, Iscan et al described the use of spring-
loaded posterior bite-blockin the correction of
anterior open-bite. This appliance comprises upper
and lower posterior bite blocks held together by
helical springs which acts by intruding the buccal
segments with consequently forward and upward
mandibular autorotations. These methods are quite
effective in growing individuals.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

65. The spring-loaded bite block has helical springs
that are placed both lingually and buccally
between the first premolar region and the last
molar region. The ends of the springs are
embedded occlusally in the molar regions of the
acrylic part of the device. The upper and lower
acrylic occlusal blocks are connected by palatal
and lingual wires, which are activated to a force of
450 g bilaterally. Patients are instructed to use the
appliance for an average of 16 h daily .
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

66. Clark’s Twin-Block
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

67. a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

68. Highpull headgear to the biteblocks may increase
their efficiency. Where the AOB is associated with
aClass II skeletal pattern, a Twin Block appliance with
highpull headgear can be used to correct the
anteroposterior discrepancy whilst controlling the
vertical dimension.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector
Dent Update 2003; 30: 235-241

69. Elastic Activator
A modified activator is used treatment of open
bite cases. The intermaxillary acrylic of the
lateral occlusal zones is replaced by elastic
rubber tubes. By stimulating orthopaedic
gymnastics (chewing gum effect), the elastic
activator intrudes upper and lower posterior
teeth. A noticeable counterclockwise rotation of
the mandible was accomplished by a decrease of
the gonial angle.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector
British Journal of Orthodontics/Vol. 26/1999/89–92

70. Elastic Activator
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

71. Elastic Activator
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

72. Magnet-AVC (Active Vertical
Corrector)
Recently, removable and fixed appliances with acrylic
bite blocks incorporating magnets to intrude the
molars have been used to correct anterior open-
bite . Dellingerreported that the rate of tooth
movement with removable bite block system
containing repelling Samarium cobalt magnets (active
vertical corrector) was greater than conventional
approach. Kuster and Inger vall reported the
advantages of fixed magnetic bite blocks.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

73. a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector
Kalra, Burstone and Nanda (1989)have suggested that
magnets may be beneficial in treating anterior open bites
by:
•intruding upper and lower posterior teeth so as to allow
mandibular autorotation and
•distracting the condyle downwards and forwards to allow
compensatory condylar growth which would again favour
mandibular autorotation

74. Magnet-AVC(Active Vertical
Corrector)
Energized bite blocks. Energy is obtained from
repelling force of samarium cobalt magnets
hermetically sealed In S.S. capsule.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

76. AVC
Mode of Action:
Reciprocal intrusion of maxillary & mandibular teeth which
result in autorotation of mandible & overbite correction
Duration of wear 12 hrs/day
Force level:
-700 gm per unit with 0 gap
-In open bite cases no 0 gap is present ,so force 600-650 gm
per unit
-Magnets are placed over the teeth to be corrected.
Reported side effect: posterior crossbite owing to the lateral
force component of the repelling magnets.
a-Posterior bite blocks, Twinblock, Elastic activator & Active vertical corrector

78. b-Functional Regulator Appliance
Frankel (FR-4)
These are thought to be effective where the
open bite is at least partly due to faulty postural
activity of the orofacial musculature. The FR-4
works by allowing vertical eruption of upper and
lower incisors and retraction of the maxillary
incisors, and some authors have reported a
change in mandibular rotation from a downward
and backward direction to upwards and
forwards.

79. The use of other functional appliances,
open-bite bionators, kinators, in the
correction of anterior open-bites have also
been mentioned by some authors

80. c-Highpull Headgear
Highpull headgear applied to the
maxillary molar teeth and worn for 14
hours per day has been used to inhibit
eruption of the posterior teeth and
hence limit vertical growth. Headgear
can be applied directly to the upper
molar bands of a fixed appliance or use
in conjunction with a functional
appliance or an upper removable
appliance such as a maxillary intrusion
splint. This form of treatment is based
on the assumption that over-
development of the posterior maxilla is
responsible for the deformity.

81. c-Highpull Headgear
Functional appliances used for Class II maloclusions
with increased vertical proportions include the van Beek
appliance ,it incorporate high-pull headgear and buccal
capping. In many cases fixed appliances are then used
to complete arch alignment, together with extractions if
indicated.

82. c-Vertical Pull Chincup
Vertical pull chincup therapy has been used
to limit excessive vertical growth. Pearson
reported on 20 growing patients with
backward rotational tendencies treated by
the extraction of four first premolars, chincup
therapy and fixed appliances. He showed
that chincup therapy was effective in
reducing the angle between the maxillary
and mandibular planes and at closing all
anterior open bites.

83. c-Vertical Pull Chincup
Mandibular autorotation was attributed to
reduction in the ‘wedging’ effect by premolar
extraction, retardation of eruption of posterior
teeth and redirection of condylar growth.
However, chincup therapy generally has poor
compliance rates and there is some concern that
it may cause condylar damage.

84. c-Vertical Pull Chincup
Skeletal and dental open bites were successfully
corrected by using vertical chincaps. The
mandibular plane angle decreased significantly.
The gonial angle closed, the ramal inclination angle
decreased, and the corpus inclination increased, all
indicating anterior rotation of the mandible. Anterior
rotation of the mandible occurred as a result of
inhibiting the vertical growth in the mandibular
posterior dentoalveolar region. The eruption of the
mandibular incisors played an important role in
correcting the open bites in the vertical chincap
group.
American Journal of Orthodontics and Dentofacial Orthopedics November 2002

85. d-palatal crib and high-pull chin
cup therapy
Twelve months treatment with a palatal crib and chin cup
therapy resulted in the following changes:
1. Statistically significant extrusion of the incisors, as well as an
increase in overbite and exposure of the maxillary incisors.
2. Greater uprighting and retrusion of the incisors, with a
statistically significant difference compared with the controls.
3. No statistically significant changes in the level of eruption of
the molars, with no real or relative intrusion of these teeth.
4. No statistically significant skeletal changes, or significant
growth inhibition of LAFH, closure of the mandibular
plane angle or SNA/SNB modification.
F. TORRES ET AL ,European Journal of Orthodontics 28 (2006) 610–617.

86. HIERARCHY OF EFFECTIVENESS
IN LONG-FACE CLASS II
TREATMENT

87. 4-Fixed appliances
1-The use of transpalatal bar(vertical holding
appliance VHA) , 0.04" thick or half round
wire (5-6 mm) that had an acrylic pad & kept
away from the soft tissues of the palate , allows
the tongue to exert a depressive action on the
molars, reducing anterior open-bite. Some
researchers have concluded that the VHA is
useful in restricting and helping reduce the
percentage of lower anterior facial height in
growing patients .
DeBerardinis M, Stretesky T, Sinha P, Nanda RS Am J Orthod Dentofacial Orthop 2000

88. 4-Fixed appliances
2-Intermaxillary elastics:Anterior open bites can be closed
using fixed appliances and vertical intermaxillary elastics to
extrude the anterior teeth. This may be combined with a
transpalatal arch (TPA) and highpull headgear to limit vertical
development of the maxillary molar teeth. The TPA
functions to prevent buccal rolling of the first molars, which
could cause the bite to be propped open on their palatal
cusps. Use of anterior elastics may be successful in patients
in whom a digit-sucking habit has artificially inhibited
eruption, but is unlikely to work if the aetiology is primarily
skeletal.

89. 4-Fixed appliances
JCO 1991 Nov (697-698)

90. 4-Fixed appliances
Correction of Open Bite with Elastics and Rectangular NiTi
Wires
JCO 1991 Nov (697-698)

91. 4-Fixed appliances
In this situation the incisors have frequently erupted
further than normal as part of natural compensation,
and further extrusion would be aesthetically
inappropriate and highly prone to relapse. Distal
movement of teeth using headgear is contraindicated,
as this will tend to worsen any AOB. Similarly, Class II
or Class III elastics should not be used a they cause
molar extrusion.
Dent Update 2003; 30: 235-241

92. 4-Fixed appliances
3-Incisors retraction:Where
anterior open bites are associated
with proclined incisors, such as
some bimaxillary proclination cases
and Class II/I malocclusions,
retraction of the incisors results in
an extrusive movement, as the
crown is rotated around the centre
of rotation of the tooth. This
reduces/eliminates the open bite.
Stability depends on the tongue
adapting to a new functional
position after treatment.
Dent Update 2003; 30: 235-241

93. 4-Fixed appliances
4-Extractions:
a-Molar extractions
have been performed in an attempt to reduce the
magnitude of the open bite by forward mandibular
rotation. However, Nahoum suggested that, although
this may close the anterior open bite, the physiological
rest position of the mandible would not change, thus
leaving total face height unaltered. Mizrahi suggested
limiting extractions to the posterior region of the arch
where crowding was present. Richardson reported that the
extraction of four second permanent molars caused an
increase in the overbite compared with a control group;
they attributed this to a slight distal movement of the
dentition, with retroclination of incisors and increase in
the interincisal angle. Dent Update 2003; 30: 235-241

94. 4-Fixed appliances
4-Extractions:
Aras (2002) has confirmed that extracting
further back in the arch, i.e.: first molars or second
premolars compared with first premolars, results in
a reduction in the maxillary mandibular plane
during treatment.

95. 4-Fixed appliances
5-A one-couple extrusion archmay be used
to dentally correct open bites . The equilibrium
forces are extrusive at the incisors and intrusive
on the molars. Extrusion occurs much more
rapidly than intrusion, and treatment must be
carefully watched to prevent overtreatment.
Textbook of orthodontics ,Samir E. Bishara 2001

96. 4-Fixed appliances
6-Multiloop Edgewise Arch Wire(MEAW)
(Kim mechanics)

97. MEAW
The treatment of anterior open bite is
considered the most difficult task in the
orthodontic specialty.These malocclusions are
frequently subjected to orthognathic surgury,
with questionable results.Multiloop edgewise
archwire therapy, however, has been found to be
effective in treating open bite malocclusions

98. MEAW
Rationale behind choosing this mechanics:
Palatal plane is tipped upward & forward with
teeth tipped mesially.
Because of this ,treatment should be directed
toward extracting the terminal molars and distal
tipping of the dentition

99. MEAW
This is usually achieved using multi-loop
edgewise archwires made of 0.016×0.022 S.S.
wire. 5-L-shaped loops /side starting from
between lateral incisors and canines and moving
distally .
Vertically ,loops should be 2-3 mm and
horizontally it should be 5-mm except in molar
region where this increased to 8-mm

100. MEAW
Tip-back of 3-5 degrees are placed on each loop
to place a curve of spee(CS) on upper and
reverse curve of spee(RCS) in lower arches
.3/16”or 1/8”heavy elastics anteriorly will
counter act the curve of spee in upper and RCS
in lower.

101. MEAW
Although this method has proved successful,
excellent compliance with elastic wear is
essential and long-term stability has yet to be
determined.

102. 4-Fixed appliances
7-(Recent modification of Kim mechanics)
More recently, the use of reverse curve nickel-titanium
archwire, instead of multiloop wires, had worked well.
0.016×0.022 NiTi RCS in lower and accentuated CS in
upper arch.
Heavy anterior elastics(3/16”4.5 Oz) in canine region
At some stage ,molar become out of contact , then flat
0.016×0.022 S.S. wire is inserted and continue with
anterior elastics.

103. 4-Fixed appliances-RCS

104. Effects of MEAW & CS
1-Retraction and extrusion of anterior teeth
2-Up-righting & intrusion of posterior teeth
3-Few skeletal changes

105. 4-Fixed appliances
8-Rapid Molar Intruder(RMI) Appliance in
Growing Individuals
a.The RMI appliance provided effective bite
closure and favorable dentofacial changes for
nonsurgical open bite treatment in growing
patients.
b.This method could be regarded as a safe and
non-compliance alternative for early
intervention of skeletal open bite correction.
C ¸INSAR, ALAGHA, AKYALC ¸I NAngle Orthodontist, Vol 77, No 4, 2007

106. RMI
C ¸INSAR, ALAGHA, AKYALC ¸I NAngle Orthodontist, Vol 77, No 4, 2007

107. RMI

108. RMI
Initial clinical experiences with the RMI device are
promising, but a more structured research project is
needed to demonstrate the long-term stability of the
results. This noncompliance device for molar intrusion
opens new horizons in the complex treatment of
vertical excess. A follow-up study and future research
will contribute valuable information about stability. In
addition, significant new methods for retaining treated
open bites that have undergone intrusion of posterior
teeth might also be developed in future investigations.
American Journal of Orthodontics and Dentofacial Orthopedics December 2005

109. RMI
American Journal of Orthodontics and Dentofacial Orthopedics December 2005

110. 5-Camouflage
Occasionally incisor retraction following relief of
crowding is stable if the lips become competent
post-treatment .It is essential to avoid mechanics
which will worsen AOB ( e.g. cervical headgear,
intermaxillary elastics to maolars, anterior bitepalne
that will extrude moalrs).

111. Hints
For cases with increased vertical dimension and
decreased overbite or AOB:
1-Avoid extruding molars (mentioned above)
2-Avoid upper arch expansion as this will tip down
the palatal cusps of the buccal segment teeth ,
reducing overbite.
3-Extraction of molars help “close down the bite”,
but no scientific evidence to support this .
4-Space closure is said to occur more readily in
patients with increased LFH and MMPA.
Oxford Handbook of Clinical Dentistry 2005,D&L.Mitchell

112. 5-Surgery & Implants
A-Microscrews & Miniplates (skeletal anchorage)
B-Distraction Osteogenisis
C-Tongue reduction
D-Orthognathic Surgery.

113. A-Microscrews & Miniplates
 Until recently, orthognathic surgery was
considered the treatment of choice for a severe
skeletal open bite. The advent of skeletal anchorage
has expanded the boundaries of orthodontic
treatment. The use of surgical bone plates in a
skeletal anchorage unit was first described in 1985 .
Skeletal anchor-age can produce treatment outcomes
that cannot be obtained by conventional orthodontic
treatment but only from orthognathic surgery. In an
earlier report, we showed that the maxillary incisors
can be retracted 14mm against microscrew implants.
This is beyond the limit of orthodontic treatment.
American Journal of Orthodontics and Dentofacial Orthopedics September 2006

114. A-Microscrews & Miniplates
The recent development of orthodontic
miniscrews has made it possible to achieve stable
correction of open bite with orthodontics alone.
a skeletal open bite was corrected by intrusion of
the posterior teeth, using titanium miniplates for
anchorage. The long-term stability of molar
intrusion for the correction of open bite is still
controversial; Sugawara and colleagues reported
one-year relapse rates of 27.2% for first molars
and 30.3% for second molars, although the
skeletal changes were maintained.
JCO/MAY 2007

115. A-Microscrews & Miniplates
American Journal of Orthodontics and Dentofacial Orthopedics September 2006

116. A-Microscrews & Miniplates

117. A-Microscrews & Miniplates
JCO/MAY 2007

118. A-Microscrews & Miniplates
JCO/MAY 2007

119. A-Microscrews & Miniplates
JCO/MAY 2007

120. A-Microscrews & Miniplates
American Journal of Orthodontics and Dentofacial Orthopedics November 2004

121. A-Microscrews & Miniplates
Methods of Molar intrusion with Microscrews &
Mini implants :
Various methods of using skeletal anchorage for the
correction of overerupted maxillary molars have
recently been proposed, including buccal miniplates
or miniscrews with transpalatal bars; buccal and
palatal miniscrews with extension wires ; and a
combination of buccal miniplates and palatal
miniscrews. The last technique is relatively convenient
and effective, but requires a morecomplex and
invasive surgical procedure for insertion of the
miniplates.
JCO/JUNE 2006

122. A-Microscrews & Miniplates
JCO/JUNE 2006
Maxillary Molar Intrusion

123. A-Microscrews & Miniplates
JCO/JUNE 2006
Maxillary Molar Intrusion

124. A-Microscrews & Miniplates
JCO/JUNE 2006
Maxillary Molar Intrusion

125. A-Microscrews & Miniplates
Mandibular Molar Intrusion
JCO/FEBRUARY 2006

126. A-Microscrews & Miniplates
Mandibular Molars Intrusion
American Journal of Orthodontics and Dentofacial Orthopedics April 2007
preadjusted
edgewise appliances
were placed
sectionally on both
mandibular molars
A mandibular lingual
arch was placed
between the
first molars to
compensate for the
buccal crown torque.

127. A-Microscrews & Miniplates
Titanium miniplates, as used in this study, offer
stable skeletal anchorage for intruding molars.
True intrusion of molars can be accomplished in
adults. The occlusal plane angle of open-bite
patients changes accordingly. Anterior open bites
can be closed orthodontically by intruding
posterior teeth, resulting in reduced anterior
vertical face height, decreased mandibular plane
angle, and counterclockwise rotation of the
mandible.
American Journal of Orthodontics and Dentofacial Orthopedics December 2002

128. A-Microscrews & Miniplates
American Journal of Orthodontics and Dentofacial Orthopedics December 2002

129. A-Microscrews & Miniplates
American Journal of Orthodontics and Dentofacial Orthopedics December 2002

130. A-Microscrews & Miniplates
American Journal of Orthodontics and Dentofacial Orthopedics November 2007

131. B-Segmental alveolar distraction for the
correction of unilateral open-bite
caused by multiple ankylosed teeth
A case with unilateral open bite caused by familial multiple
ankylosed teeth was successfully treated using segmental alveolar
bone distraction. A good occlusion segmental osteotomy on the
left maxillary alveolar bone and downward bone distraction were
performed as an alternative. A distractor consisting of
orthodontic bands, wires and screws was devised and worn in the
left mandibular dentition. Multi-bracket orthodontic appliances
were also used for distraction. The amount of vertical movement
was 7 mm at the premolar region. Five months after distraction,
the multibracket appliance was removed, and fixed and removable
retainers were placed. The unilateral open bite was successfully
treated and a good occlusion was obtained. The occlusion has
shown good long-term stability for more than 3 years.
Journal of Orthodontics, Vol. 33, 2006, 153–159

132. B-Segmental alveolar distraction for the
correction of unilateral open-bite
caused by multiple ankylosed teeth
Journal of Orthodontics, Vol. 33, 2006, 153–159

133. B-Segmental alveolar distraction for the
correction of unilateral open-bite
caused by multiple ankylosed teeth
Journal of Orthodontics, Vol. 33, 2006, 153–159

134. B-Segmental alveolar distraction for the
correction of unilateral open-bite
caused by multiple ankylosed teeth

135. B-Segmental alveolar distraction for the
correction of unilateral open-bite
caused by multiple ankylosed teeth

136. D-Tongue Reduction
A severe open bite and macroglossia treated with a standard
edgewise appliance and without partial glossectomy . The lower
arch relapsed during the retention period, with a widening of the
intermolar distance, flaring of the anterior teeth, and increased
mobility of the teeth. tongue reduction is chosen to resolve these
problems and one-third of the middle dorsal part of the tongue
was excised. After the tongue reduction, the patient experienced
no functional problem in mastication, swallowing, and gustation,
but she complained of mild speech difficulty and slight pain on
the dorsal portion of her tongue. These symptoms disappeared 6
months after surgery. At this time, the mandibular dental arch was
markedly improved. The flared lower dental arch had returned to
an upright position and the tooth mobility reduced to normal. No
appliance was used after surgery. Most of the recovery changes
occurred within 4 months.
Angle Orthod 2001;71:228–236

137. D-Tongue Reduction
Angle Orthod 2001;71:228–236

138. D-Tongue Reduction

139. D-Tongue Reduction
Angle Orthod 2001;71:228–236

140. D-Tongue Reduction
In addition to the various surgical procedures
described in the literature, many clinicians have also
advocated a partial glossectomy in the management
of open-bite cases. However, in recent times, partial
glossectomy appears to have fallen out of favor in the
management of such cases, possibly because of many
reports on disturbance to sensation, speech difficulties
and the doubtful efficacy of glossectomy in improving
the progress or preventing the relapse of the open-
bite correction.

141. D-Orthognathic Surgery
Pre –surgical orthodontics
Leveling
Alignment
Decompensation
Coordiantion

142. Pre-sugical orthodontics
Treatment should not be commenced until growth
has ceased, as further growth is very likely to be
unfavourable . Presurgical orthodontics is aimed at
individual arch alignment and arch co-ordination.
Mild –Moderate open bite cases continuous
archwire
Severe AOB segmented archwire
If segmented mechanics is used space will be needed
for surgical cuts.

143. Pre-sugical orthodontics

144. D-Orthognathic Surgery
Orthognathic surgery continues to play an important role in the
treatment of anterior open bite. In cases where anterior facial
height is to be reduced surgically (skeletal open-bite), most of the
orthodontic tooth movement is accomplished prior to surgery.
Maximizing the presurgical orthodontics lead to minimal
postsurgical mechanics. Avoidance of intrusive mechanics in the
buccal region, e.g. high pull headgear, and concurrent avoidance
of any extrusive mechanics in the anterior region will also
facilitate maximum surgical correction and reduced relapse of the
open-bite. This is usually followed by one-piece Le Fort I
osteotomy with more impaction of posterior maxillary segment.
An alternative surgical approach is presurgical segmental leveling
in the upper arch followed by Le Fort I osteotomy with a three-
part maxillary surgery. Autorotation of the mandible helps close
down the open-bite. In some cases, bimaxillary procedure may be
necessary.

145. D-Orthognathic Surgery

146. D-Orthognathic Surgery

147. D-Orthognathic Surgery

148. D-Orthognathic Surgery

149. Retention for AOB
Removable appliance with thin acrylic cap
appliances with bite blocks-, such as open-bite
activator worn at night in addition to daytime wear
of removable appliance retainer over a long
retention period, has also proved valuable in the
prevention of relapse of anterior open-bite
High pull head gear with bands on molars or
removable appliance-conventional removable
retainers-night time prevent relapse of open-bite.
Long-term prognosis of anterior open-bite is
somewhat unpredictable.

150. Stability
Prediction of the response to treatment and the
stability of the outcome is generally unreliable.
Relapse rates after treatment of AOB are high. As a
rule, the more the skeletal elements contribute to
the aetiology of the malocclusion the poorer the
prognosis for orthodontic treatment alone.
Neither the extent of the pretreatment open bite
or mandibular plane angle nor any other single
parameter of dentofacial form was a reliable
predictor of post-treatment stability.

151. Stability
Lopez-Gavito et al.(1985)10 yrs post retention:
35%of treated cases had AOB of > than 3mm
Kim et al.(2000) Stable correction after 2 yrs of retention
with less than 0.5 mm relapse.(kim mechanics)
Janson et al.(2003) –AOB treated non extraction with anterior
elastics 62% of subjects had a positive overbite at the end
of retention( increase relapse)
De Freitas et al. (2004)AOB treated with extraction
(HPHG, anterior elastics) 74% of subjects had a positive
overbite at the end of retention(8.4 yrs)
Denison et al.(1989)AOB treated surgically 43% relapse

152. Stability
Relapse of AOB has been attributed
to:
unfavourable growth (a posterior mandibular growth
rotation);
soft-tissue factors such as an unfavourable tongue
posture;
resumption of a digit-sucking habit;
inappropriate orthodontic tooth movement, such as
extrusion of incisors where their eruption had not been
previously impeded; and
surgery that has increased the posterior face height –as
would occur if the AOB is closed using a mandibular
procedure only.

153. References
Proffit WR, Fields HW. Contemporary orthodontics. 4
th
Ed . Mosby Year Book
Inc, 2007.
Oxford Handbook of Clinical Dentistry 2005
An Introduction to Orthodontics, Laura Mitchell 2002
Textbook of orthodontics, Samir E. Bishara.2001
Glossary of Orthodontic Terms, J.Daskologiannakis 2000
Twin block Functional Therapy W.J.Clark 2
nd
. Ed. 2002
Essintials of Orthognathic Surgery 2003
Orthodontic & Paediatric dentistry (colour guide) D.Millett 2000
Dentistry For The Child and Adolescent, 8
th
ed. 2004, Mosby, Inc. All rights
reserved.
Handbook of paediatric dentistry ,Cameron
The Angle Orthodontist Journal
American journal of orthodontics
Europian journal of orthodontics
British journal of orthodontics
J Orthod Dentofacial Orthop
The Orthodontic CYBERjournal
Dental Update journal

154. Haynes S. The distribution of overjet and overbite in English
children, 11-12 years. Dent Pract Dent Rec 1972;22: 380-83
Proffit WR, Fields HW, Moray LJ. Prevalence of malocclusion and
orthodontic treatment need in the United State estimate from the N-
HANES III survey.Int J Adult Orthod Orthognath Surg.1988; 13:97–
106
Kelly JE, Sanchez M, Van Kirk LE. An Assessment of the Occlusion of
Teeth of Children 6–11 Years[US Public Health Service DHEW Pub
No 130]. Washington, DC: National Center for Health Statistics;
1973:3
Larsson E. Dummy and finger-sucking habits with special
attention to their significance for facial growth and
occlusion. 1. Incidence study. Sven Tandlak Tidskr
1971;64:667-72.
Lopez-Gavito G, Wallen TR, Little RM, Joondeph R. Anterior open-
bite malocclusion: a longitudinal 10-year post retention evaluation of
orthodontically treated patients. Am J Orthod 1985;87:175-86.