This document discusses the management of deviated midlines. It notes that differential diagnosis is important to determine the cause of the midline deviation and appropriate treatment. Treatment may involve correcting dental asymmetries through orthodontics or expanding a narrow maxillary arch first if caused by a posterior crossbite. Functional appliances can be used to shift the mandible into the proper position if a skeletal deviation is present. Surgical correction may be needed for true skeletal asymmetries. The goal is to adapt the occlusion and correct dental or facial asymmetries causing the deviated midline.
3. Introduction
Perfect bilateral symmetry is largely a
theoretical concept that seldom exists in the
living organisms. Asymmetry of the face
and dentition is a naturally occurring
phenomenon.
Relative symmetry and midline
coordination are basic to an appreciation of
facial harmony and balance.www.indiandentalacademy.com
4. Definition
Symmetry is defined as equality or correspondence in forms
of parts distributed around a centre or an axis at the two
extreme pole or on the two opposite sides of the body.
Asymmetry in craniofacial areas can be recognized as
difference in size or relationship of the two sides of the face.
This may be a result of discrepancies in the form of
individual bones or malposition of one or more bones in the
craniofacial complex, or the asymmetry may be confined to
the soft tissue.
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5. Classification
Sarver evaluates the facial symmetry under the
following reference planes
Nasal tip to the mid sagittal plane
Maxillary dental midline to the mid sagittal plane
Maxillary dental midline to mandibular dental
midline
Mandibular dental midline to mid symphysis
Mid symphysis to the mid sagittal plane
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6. Midlines can also be classified as
Dental midline – related to the symmetry of the
dentition of the maxilla and mandible
Functional midline - related to the functions of
the stomatognathic system
Skeletal midline – related to the symmetry of the
osseous structures of the craniofacial region
Soft tissue midline – related to the symmetry of
the soft tissue of the craniofacial regionwww.indiandentalacademy.com
7. Functional midline
Centric relation is the relationship of the mandible
to the cranium when the condyles are in an
orthopaedically stable position. It is the most
retruded position of the condyle.{superoanterior
position}
Centric occlusion is the maximum intercuspation of
the teeth
Postural rest position - the synergistic and the
antagonistic muscular components are in dynamic
equilibrium. The balance is maintained with
minimal basic muscle tonus.www.indiandentalacademy.com
8. Postural rest position
Postural rest position
Myostatic anti stretch
reflex
Permanent
exogenous factors
Gravity Dependent and
altered with the head
positionwww.indiandentalacademy.com
9. Movement of the mandible
During the closing maneuver from the rest position
to the habitual occlusion two phases of the
movement can be observed
The free phase - from the postural rest position to the
point of initial contact or occlusal prematurity
The articular phase - from the initial contact position to
the centric occlusion or habitual occlusal position
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10. Laterocclusion
When the occlusal prematurity is present
Midline shift observed only during the centric occlusion
or intercuspation.
During the postural rest position the midlines are
coincident and well centered .
The mandible slides laterally from the rest position into a
cross bite and is caused by the tooth guidance,after the
initial contact of the free phase
LATEROCCLUSION
also called the pseudo cross bitewww.indiandentalacademy.com
11. Mandibular dental midline
coincident with the facial
midline in postural rest position
Mandibular dental
midline shifted to the
right in habitual
occlusion
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14. Laterognathy
Midline shift is present in both centric occlusion and
in the postural rest position
This condition is generally seen in the true
asymmetry of the mandible
Functional appliances have poor prognosis
Surgical correction required
LATEROGNATHY
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15. Mandibular dental midline not
coincident with the facial
midline in postural rest position
Mandibular dental midline not
coincident with the facial
midline in habitual occlusion
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16. Etiology
One of the common etiologic factor for the
deviation of midline, irrespective of the type of the
midline shift is GENETICS – due to the genetic
imperfections in the mechanism which was meant to
create symmetry and environmental factors
producing decided right and left differences
Examples –
multiple neurofibromatosis- familial incidence
associated with dominant gene
Hemifacial microsomia
Cleft lip and palatewww.indiandentalacademy.com
17. Lundstorm classified the etiological factors as
Genetic
Non genetic
combination
Another classification by the same author
Qualitative –
Size of the teeth
Location in the arches
Position of the arches
Quantitative
Differences in the number of teeth on each side or the presence
of cleft lip or palatewww.indiandentalacademy.com
18. Midline diastema
Mesiodens
Generalized spacing
Frenal attachments
Congenital absence of a tooth
Morphological variation of a tooth eg. Microdontia or macrodontia
Asymmetrical exfoliation
Retained deciduous teeth
Early loss of primary teeth
Crowding
Trauma
Habits such as thumb sucking and tongue thrusting
Traumatic occlusion leading to pathological migration
Pathological condition such as cysts
EtiologyDental midline shift
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20. The upper right central incisor
has shifted to the right due to the
congenital absence of lateral
incisor
The contact point upper central
incisor do not coincide with the
center of the philtrum
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21. Functional midline shift
Neurological disturbances
Disturbances in the tooth – tooth inter relationship
Anterior cross bite
Posterior cross bite
Contracted maxillary arch
Any other occlusal prematurity preventing the smooth
closure from the free phase to the articular phase
Compensation of a skeletal discrepancy
Etiology
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23. Skeletal midline shift
Genetics
Local
Trauma
Ankylosis
Damage to nerve – loss
of muscle function and
tone
Pathological state in
the form of cysts and
tumors
Unilateral posterior
edentulous area
Post operative sequale
of orthognathic surgery
Etiology
Temperomandibular
joint
Systemic
Intrauterine pressure
during pregnancy and
significant pressure in the
birth canal
Condylar resorption
Rheumatoid arthritis
Systemic Lupus
Erythamatosis
Sjogren’s syndrome
Marfan’s syndromewww.indiandentalacademy.com
24. Soft tissue midline shift
Neurological disturbances such as cerebral palsy
and Hemifacial microsomia
Massetric hypertrophy
Trauma
Scars including surgical scars
Dermatomyositis
Neoplasm
Adaptation to the existing skeletal asymmetries
Etiology
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25. Diagnosis
Asymmetry of the face is one of the more difficult problems
with which the orthodontists have to contend and which
presents serious diagnostic problems. The recognition of
actual site of asymmetry is essential for correct treatment
planning.
The point at which normal symmetry becomes abnormal
cannot be easily identified and is often identified by the
clinician’s sense of balance and patient’s perception of their
imbalance.
Vig and Hewitt studywww.indiandentalacademy.com
27. History
Patient history is important for the diagnosis, as it
aids in the knowledge of
Exfoliation of the primary teeth
Extractions undergone if any
Trauma
Familial tendencies
Congenital problems
Surgical procedurewww.indiandentalacademy.com
28. Clinical examination
Frontal view evaluation
Nasal tip to mid sagittal plane
Maxillary dental midline to midsagittal plane
Mandibular dental midline to midsagittal plane
Mandibular dental midline to midsymphysis
Midsymphysis to midsagittal plane
Evaluation of dental midline in the
Mouth open
Centric relation
At initial contact
Centric occlusion www.indiandentalacademy.com
29. Other features to be noted during clinical
examination are
Missing and supernumerary teeth
Tooth shape and size
Arch form symmetry
Frenal attachments
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32. Advantages
Inexpensive
No exposure to potentially harmful radiation
Better evaluation of the harmony relationship
among the craniofacial structure including the
contribution of muscle and adipose tissue
Readily used to posture the head and face and to
compare these with the relationship existing among
the different craniofacial structureswww.indiandentalacademy.com
34. Occlusograms
1992, JCO, Occlusograms in Orthodontic Treatment Planning -
RICHARD D. FABER,
Lower occlusal tracing
placed over arch
symmetry chart to
establish midline and
perpendicular
reference crosshairs.
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36. Orthopantamogram
Temperomandibular joint can be viewed
Asymmetry of the body or ramus of the mandible
Missing or supernumerary teeth
Pathological condition like cysts and neoplasmwww.indiandentalacademy.com
41. JCO 1982: Orthognathic and Craniofacial Surgical Diagnosis
and Treatment Planning: A Visual Approach. Farhad et al
Horizontal and vertical lines are drawn to indicate areas of
asymmetry. www.indiandentalacademy.com
42. Posteroanterior view
Disadvantages
Midline assessment is difficult
Difficulty in reproducing head posture
Difficulty in identifying landmarks because of
superimposition of structures
Exposure to radiation
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43. Submentovertex (SV)
Berger was the first to suggest the use of SV (problems and
promises of basilar view cephalogram) in orthodontics.
Gibert associated the film cassette parallel to the FH plane
Pearson found exceptional degree of symmetry in the
sphenoid bone
Keith and Campion used sphenoid bone as a fixed reference
in comparing the development of growth of skull
Marmary and associates showed that perpendicular bisector
of a line joining the foramina spinosa was a reliable and
accurate midline
Ritucci and burstone developed the ceph system for the
assessment of craniofacial regionwww.indiandentalacademy.com
48. Basilar multi plane cephalometric analysis
Put forward by Grayson et al 1985, AJO
Developed to facilitate the measurement of the
craniofacial complex from the submento vertex
view.
Basilar view is a two dimensional representation of
a three dimensional object
The cranium can be reconstructed in 3 dimensions
from the basilar view cephalograph by separately
tracing each of the three suggested horizontal plane
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49. Multi View Fluoroscopy
Permits three dimensional analysis of the
oropharyngeal components in motion
Combines the lateral, frontal and basal projection
Contrast medium is used to define the soft tissue
landmarks and to determine their function during the
variety of functions of the stomatognathic system.
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50. Management
Differential diagnosis and appropriate inter arch and
intra arch mechanotherapy is necessary to determine
and correct the midline problem.
Review of literature
Breakspear advocates adapting the occlusion by
‘stoning’- occlusal equilibration. This mode of
treatment allows the settling of occlusion to
function better but not to correct the dental or
facial asymmetry.
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51. Paul Lewis – dental asymmetries are more
commonly seen with class II malocclusion
The correction of mid line caused by the shift of the
mandible or rotation of the mandible is attempted only
after teeth in both arches are put into quite ideal
occlusion.
In midline deviation that occurs with posterior cross
bite,the narrow maxillary arch must be expanded first.
A class II elastic worn from a hook or sliding yoke on
the side towards which the mandible has shifted. A
second elastic is worn across the anterior teeth to swing
or pivot the mandible until midline correction is
achieved. www.indiandentalacademy.com
52. Angle’s treatment modality
. From Angle EH. Malocclusion of the teeth, 1907.
Angle suggests
Class III elastic with
tandem anterior
diagonal elastic in
conjunction with
area expansion for
correction of midline
discrepancies.
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53. Begg mechanotherapy
. From Begg PR, Kesling P. Begg orthodontic
theory and technique, 3rd ed.
Space-closing elastics
and Class II
intermaxillary elastics
applied at start of
second stage of
treatment.
Anterior diagonal
elastics,class II elastics
and class III elastics
and Uprighting springs
(Mollenhaeur) www.indiandentalacademy.com
54. Wick Alexander
Midline is corrected during the finishing stages
¼ inch, 6 ounce elastic ,one end attached to maxillary
lateral bracket and adjacent central bracket. The other end
attached to mandibular lateral incisor bracket on the
opposite side.
In case of class II tendency, a class II elastic is worn and in
class III tendency,class III elastics are worn.
The class II elastic is attached to the maxillary lateral
incisor and mandibular second molar. The two elastics
impart roughly parallel force vectors.
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56. In cases of midline discrepancy in class I buccal
relationship, only the midline elastic is worn, extra class II
or class III elastics are not worn.
Midline elastics are worn during the finishing stages of
active treatment with one exception. In an extraction case
during space closure the midline may be shifted
significantly, during space closure the elastic can be
attached to the closing loops. This will help to control the
direction of space closure, thus improving the midline.
Over correction
Ideal occlusion and midline
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57. Correction of midline in class II subdivision
Suppose class II on right and class I on left, the
midline is generally shifted to the left
To re establish the midline the extraction pattern
would be
Upper arch – left side – second premolar
right side – first premolar
Lower arch - left side – first premolar
right side – second premolar
4 5
5 4
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58. Gianelly
Introduced a biomechanical system with second
order bends to move the teeth distally and create
space for the midline correction
Class II and class III elastics are used to enhance the
couple force systems
Gianelly AA, Paul IA.
A procedure for midline correction. AJO 1970www.indiandentalacademy.com
59. Strang
Double vertical spring loop auxiliary adjusted for the mass
movement of the four incisor teeth to the left. From strang
R, Thompson W. A textbook of orthodontia, 1958.
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60. Source: AJO-DO , 1990 Jun : The midline – diagnosis
and treatment, Jerrold
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61. Profitt
Minor midline discrepancy can be corrected during
the finishing stages
Large discrepancy correction becomes difficult after
the closure of extraction spaces
A correct maxillary midline is more important for
good facial aesthetics and mild mandibular midline
creates no esthetic difficulty
Use of class II or class III elastics bilaterally with a
heavier force on one side
Combination class II and class III elastics
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63. Parallel cross elastics used to correct mild tranverse
discrepancy leading to the lateral mandibular shift
late in the treatment
Anterior diagonal elastics with rectangular arch wire
in the lower arch and a round wire in the upper to
shift the maxillary arch
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64. When midlines are
deviated to the opposite
side,correction
accomplished with
Uprighting springs
Functions are normal
Not healthy from
periodontal point of view
Esthetic results are poor
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78. Careful attention to midline coordination and
attendant facial symmetry helps to achieve
Maximum intercuspation
Normal function with anterior disocclusion and without
any loading of the anteriors
Stability in the finished result
Promotion of anterior dental and facial esthetics
Decreased potential for Temperomandibular joint
dysfunction
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79. Functional midline deviation
The functional midline shift can be corrected
by unlocking the mandible
Removal of the occlusal prematurities
Expansion of the upper arch
Functional appliances
Inter arch elasticswww.indiandentalacademy.com
80. Surgical options
Nasal tip to midsagittal plane
Rhinoplasty
Camouflaging grafting of the tip of and /or the dorsum
Maxillary dental midline
Subapical procedure to rotate midlines
Mandibular dental midline to symphysis
Subapical procedures to rotate the mandible
Mandibular asymmetry{functional mandibular
shift}
Two or three piece maxillary expansion via Le fort I
osteotomy
Surgically assisted maxillary expansionwww.indiandentalacademy.com
81. True mandibular asymmetry
Distraction osteogenesis
Bilateral ramal osteotomies
Camouflage through bone grafting or alloplastic
augmentation
Transverse cant of the maxilla
Maxillo mandibular surgery
Chin asymmetry
Rotational genioplasty
Lateral or vertical movement of chin via inferior border
osteotomy
Camouflage via bone graft,ostectomy or alloplastic
augmentation www.indiandentalacademy.com
82. Soft tissue asymmetry
Augmentation with bone grafts, alloplastic material and
silicone implants to re contour the desired areas of the
face
Muscular stripping
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87. Ajo 1991 Assessment of structural and displacement mandibular asymmetries - Schmid,
Mongini, and Felisio The following conclusions may be drawn:
1. In the growing patient, craniomandibular asymmetry with transverse deviation of
the mandible and the chin, with no genetic or congenital origin and without a
history of trauma, infection, or tumor, is possibly the result of mandibular
displacement consequent to occlusal alterations.
2. If the mandibular displacement is not detected and treated in a timely manner,
adaptive mandibular asymmetry may develop.
3. Depending on the elapsed time between the onset of mandibular displacement
and the examination, the patient can show displacement asymmetry, structural
asymmetry, or a combination of both. The last possibility may be the most frequent
in a population of growing patients.
4. The different patterns of asymmetry can be identified and to some extent
quantified in each patient.
5. Successful treatment during the growing period is possible in some patients. If
the subject remains untreated, asymmetry can become a permanent feature in the
adult.
6. However, mandibular displacement may not be all or even part of the cause of a
craniomandibular dysfunction. In such cases any kind of orthopedic treatment may
be completely or partially ineffective.
7. Because the symmetry in one of the control subjects improved in the absence of
intervention, other factors besides treatment may be responsible for the different
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89. Correction of arch asymmetries as suggested by
Lewis
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