This document discusses midline discrepancies and facial asymmetry. It begins with definitions and discusses the etiology and diagnosis of asymmetries. Types of midline discrepancies are described. Treatment involves detailed evaluation of the soft tissues, dentofacial skeleton, and dentition using study models, radiographs, and photographs. Occlusion is also evaluated to assess compatibility between centric occlusion and centric relation. Accurate diagnosis of asymmetries requires a systematic approach.
3. Introduction
Definitions
Etiology
Database for diagnosis
Diagnosis
Types of midline discrepancies
Treatment
Conclusion
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4. o Midline coordination and relative symmetry are basic to an
appreciation of facial harmony and balance.
o Although a subtle asymmetry of the midlines is within normal
limits, significant midline discrepancies can be quite
detrimental to dentofacial esthetics.
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5. o Of all occlusal asymmetries, midline discrepancies are the
most obvious from the patients‘ perspective.
o Midline discrepancies maybe isolated, or may occur in concert
with other occlusal asymmetries, particularly molar occlusion
asymmetry, or the angle subdivision malocclusions.
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6. o According to
Lundstrom.A, these
asymmetries are
embryonically rooted and
are associated with
asymmetry in the central
nervous system.
o Woo in 1931 found that the human
skull could be markedly
asymmetrical.
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7. o Dorland’s Medical dictionary defines symmetry as
“The similar arrangement in form and relationships of parts
around a common axis or on each side of a plane of the body”.
o W.Schmid/Mongini mentioned two types of asymmetry
1. True Structural Asymmetry
2. Displacement Asymmetry
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8. We, orthodontists are often
preoccupied with the lateral
facial aspect of the
patient, where as the general
public tend to
judge, beauty, symmetry &
harmony from a frontal
projection.
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9. Washburn in 1946, reported the effects of paralysis of facial
muscles after unilateral sectioning of the facial nerve.
Bjork and Bjork in 1964 noted that compensatory
asymmetric growth of maxilla and mandible can occur when
the cranial base develops asymmetry at an early age.
Mulick in 1965 concluded that asymmetry of the face can be
related to the functional demands of the masticatory
apparatus and musculoskeletal system.
Sharad Shah and M.R. Joshi in 1978 observed that pleasing
and apparently symmetrical faces do exhibit skeletal
asymmetry, suggesting that the soft tissue of the face
attempts to minimize the underlying skeletal asymmetry
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10. 1. Genetic alterations
2. Glenoid fossa position-growth of cranial base.
3. Moulding of parietal and facial bones due to intrauterine
pressure.
4. Trauma/infection of TMJ
5. Pathological conditions- osteochondroma of condyle.
6. Local/environmental factors
7. Habits
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11. Genetics :
1. Clefts of the lip or palate
2. Hemifacial microsomia
3. Hemifacial Hypertrophy
4. Congenital muscular torticollis
5. Postural Scoliosis
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12. Intra-Uterine pressure during pregnancy and significant pressure
at the birth canal during parturition can have observable effects
on the bones of the fetal skull.
Molding of the parietal and facial bones from these pressures can
result in facial asymmetry. These effects are generally transient
with rapid restoration of the normal relationships of the skull
within a few weeks to several month
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13. ENVIRONMENTAL FACTORS
a. sucking habits
b. asymmetrical chewing habits caused by dental caries, extractions, and
trauma.
FUNCTIONAL DEVIATION.
Due to any premature contact.
LOCALISED PATHOLOGY
a.Osteochondroma of the mandibular condyle
b.condylar hyoplasia,hyperplasia
c.irradiation
d.lymphangioma
e.fibrous dysplasia etc.
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.
14. Trauma and infection must also be considered when
encountering facial asymmetry. Untreated fractures of the
mandible can display varying degrees of facial disfigurement.
Brodie concluded injury to the condylar region results in
growth arrest, and consequently, a characteristic distortion of
the mandibular form.
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15. Condylar fracture is not always followed by deviant growth of
the mandible however, and many of the cases may remain
undiagnosed as shown by Proffit et al.
It has been found that mandibular fracture may affect the
growth of the middle facial area. The occurrence of maxillary
midline shift towards the fractured site and the degree of the
deformity are related to the site of the fracture of the mandible.
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16. o An increased incidence of crossbite and scissor bite is seen
in children with enlarged adenoids, tonsils and impaired
nasal breathing.
o Unilateral crossbite can be also associated with persistent
intensive finger or dummy sucking habits.
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17. THERE ARE THREE MAIN CAUSES OF FACIAL
ASYMMETRY AND DENTAL MIDLINE
IRREGULARITIES:
A. True skeletal asymmetries of the facial structures including
the mandible and/or maxilla
B. Dental asymmetries in one or both arches and
C. Functional shifts of the mandible during closure or opening.
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18. o Detailed facial and intraoral examination.
o Intra- and extraoral photographs/video.
o Dental models
o Occlusogram
o Lateral cephalogram
o P-A cephalogram
o 45o cephalogram
o Panoramic radiograph
o Submental vertex radiograph.
@ Ravindra Nanda, SO 1996
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19. o A diagnostic protocol, which includes systemic evaluation of
1. The soft tissue – clinical and photographic examination.
2. The dentofacial skeleton – PA
cephalogram, submentovertex view, TM Joint imaging.
3. The dentition – study model casts (model
analysis), occlusograms, OPG’s and occlusal x-rays
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20. IDEAL FCIAL PROPORTION
TRANSEVERSE FACIAL PROPORTION
Rule of fifth describe the ideal transverse relationship of the face.
The face is sagittally divided in to five
equal parts from helix to helix of outer
ear.Each of the segments should be one
eye distance in width
A-THE CENTRAL FIFTH OF THE FACE
B- THE MEDIAL TWO FIFTH
C- THE OUTER TWO FITTH
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21. oVERTICAL FACIAL RELATION-
THE FACIAL ONE THIRDS
oface is vertically divided in to equal
thirds by horizontal lines,
1. hairline to midbrow,
2. midbrow to subnasale,
3. subnasale to soft tissue menton.
oThe thirds are within a range of 55 to 65
mm, vertically.
oThe appearance of the landmarks (incisor
exposure, interlabial gap) within the lower third
are more important in assessing balance than are
the equality of the middle and the lower thirds.
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22. Facial level: With the patient in natural head posture, the pupils are
used as the horizontal reference line .
Structures compared with the pupil line are
1.upper canine level
2.lower canine level, and
3.chin and jaw level.
o Mandibular deviations commonly
have upper and lower occlusal cants
with chin and jaw line canting associated
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24. o In normal face, the profile is oriented to the vertical by
horizontal positioning of paired symmetrical features (rims of
lower eyelid, insertion point of the alae, direction of labial
fissure, and upper border of eyebrows) .
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25. Original
The composites of two
left sides and two right
sides display two
different individuals.
Right Left
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26. CEPHALOMETRIC EVALUATION
Most of the PA cephalometric analysis are quantitative and they evaluate
the craniofacial skeleton by means of linear absolute measurements of
a.width or height,
b.Angles,
c.Ratios and
d.Volumetric comparison.
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27. o An angle finder can be used to
confirm whether the required
position has been achieved and
also head position checking
device can be used.
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28. PA Cephalograms and refined diagnostic tools, such as
computerized tomographic images and
stereophotography, allow 3 – dimensional analysis of the
craniofacial complex
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30. PA cephalogram
o centric relation
@ The primary indication
for obtaining a PA view
is the presence of facial
asymmetry (Proffit
1991).
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31. Various methods of analysis:
Ricketts et al, 1972.
Hewitt 1975.
Svanholt and Solo 1977.
Grayson et al, 1983.
Chierici 1983.
Grummons and Kappeyne Van de Coppello 1987.
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32. RICKETTS ANALYSIS
Construction of midsagittal plane.
A transverse plane is constructed by connecting the center of the
zygomatic arches, then a perpendicular is constructred to the transverse
plane through the top of the nasal septum or crista galli.
Skeletal asymmetry is evaluated
by relating the point ANS and
pogonion to this mid sagittal plane.
Denture Assymetry can be evaluated
by relating the upper and lower incisor
roots to the midsagittal plane.
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34. Using the MSR plane Various transverse and vertical reference
planes are constructed to measure the
Nasal cavity width,
Mandibular width,
Maxillary width,
Intermolar and intercuspid width
SVANHOLT AND SOLOW -
This method aims to analyze one aspect of transverse cranio-facial
development, namely the relationship between the midlines of the
jaws and the dental arches
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35. GRUMMONS ANALYSIS
This a comparative and quantitative PA analysis. The analysis consist
of different components including
1.A midsagittal reference line.
2. Horizontal reference line,
3. Mandibular morphology analysis
4 Volumetric analysis.
5. Maxillo mandibular comparison
of asymmetry.
6. Linear asymmetry assessment.
7. Maxillomandibular relation.
8. Frontal vertical proportion analysis
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36. The midsagittal reference line is Constructed from crista galli through
ANS to the chin point.
oMSR plane is constructed from the midpoint of the z plane through
ANS is used as a reference midsagittal plane .
Horizontal reference lines are
1.Z line,
2.ZA line,
3.J line.
4.One parallel to the z plane
through menton
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37. oMandibular morphology analysis
Triangle are formed by connecting
the head of the condyle,the antegonial
notch and the menton and the triangles
on either side is are compared .
Volumetric analysis
o polygon is formed by connecting
Condylion, antegonial notch, menton
and a perpendicular from MSR and
the right and left side polygon are
compared.
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38. Maxillo mandibular comparison of asymmetry
Four lines are constructed perpendicular
to MSR from Ag and from J bilaterally.
Line connecting cg and J and lines from
Cg to Ag are also drawn.
Two pairs of triangles are formed in this
way, and each pair is bisected by MSR.
If symmetry present, the constructed
lines also form two triangles namely
J – Cg – J and Ag – Cg – Ag.
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39. Linear asymmetry assesement
Perpendicular projection are drawn from
the MSR to CO, NC, J, Ag and Me.
the linear distance from MSR
Frontal vertical proportion analysis
Ratios of skeletal and dental measurements
are made with respect to MSR and those
ratios can be compared with common facial
esthetic ratios and measurements
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40. GRAYSON ANALYSIS
Landmarks are identified on different
frontal planes at selected depth of the
craniofacial complex and subsequent
skeletal midlines are constructed.
In this way the analysis enables
visualization of midlines and midpoints
in the third (sagittal) dimension.
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41. HEWIT ANALYSIS
•Analysis of craniofacial asmmetry
is performed by dividing the
craniofacial complex into constructed
so called traingulation of face.
•The different angles, triangles and
component areas can be compared for
both the left and right side.
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42. LIMITATIONS OF PA CEPHALOGRAM:
1. Chances that apparent distances will be affected by a tilt of the
head in the head holder. Because of this angular measurements
can be influenced in an uncontrolled manner.
2. Precise measurements of the structures are difficult.
3. The conventional use of two ear rods to stabilize the head in
radiographic cephalometry is based on the assumption that the
transmeatal axis of humans is perpendicular to the midsagittal
plane.
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43. o Thereby, the attempt to determine facial asymmetry
of a patient generally results in a compromise rather
than as an exact definition.
HOW TO OVERCOME THIS?
o Any one ear rod should be used.
o The other ear rod should be merely placed against any
part of the ear, or replaced by a small soft rubber cup
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44. 3. Evaluation of the dentition, by means of study
model casts (model
analysis), occlusograms, OPG’s and occlusal x-
rays;
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45. OCCLUSION EVALUATION
A. FUNCTIONAL EVALUATION: compatibility between centric
occlusion (CO) and centric relation (CR) and to assess tooth
wear. Since many Class II and asymmetric individuals have
"habitual occlusions,”.
• Failure to appreciate meaningful inconsistency in CO and CR
may result in significant errors in both treatment planning
and in surgery.
B. STATIC EVALUATION : anatomically oriented models
1. intraarch analysis,
2. interarch analysis
3. tooth mass evaluation
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46. INTRAARCH ANALYSIS - MAXILLARY ARCH
oArch should be analysed for both transverse and AP symmetry
oAP reference plane is constructed using mid palatal raphae
othe tuberosity plane(drawn perpendicular to AP plane) is used as a transverse
reference plane.
oCross section of the second palatal
Rugae
omid point between the paired
foveolae
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47. INTRAARCH ANALYSIS-MANDIBULAR ARCH
•The anterior point can be precisely
Marked using mental spine or
by using the lingual frenum
•The posterior point is determined by
a perpendicular, which runs from the
posterior edge of the MPR from the
maxillary to the mandibular cast
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48. Asymmetry in the dental arch can be assessed by placing a
transparent ruled grid over the dental cast so that the grid
axis is on the median palatal raphe.
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49. MASTICATORY MUSCLE EXAMINATION .
The masticatory muscle examination has two primary functions.
First, to identify any painful and / or trigger points.
Second, to identify the deficient masticatory muscle mass that often
exists in patients who have sustained trauma to this area or who have
undergone previous orthognathic surgery.
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50. oMANDIBULAR MOVEMENTS
oThe normal interincisal opening is about 50mm.
ominimum normal protrusive and excursive movements are
approximately 6mm.
oIf deviations of greater than 2 to 4 mm occur during
opening, they are noted and recorded.
oIf opening is reduced or deviations exist, it is important to
determine if this caused by true temporomandibular joint
abnormalities or masticatory muscle problems
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51. TMJ EXAMINATION
TMJ is palpated, auscultated and examined for any pain, clicking sounds
and for normal position and movements of condyle.
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52. Evaluation of dental midlines should be done in mouth
open, in centric relation, at initial contact, and in centric
occlusion.
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56. Quantitative asymmetry:
1. Size of the teeth
1. Microdontia
2. Macrodontia
2. Location of the teeth in dental arch.
1. Antero-posterior plane
2. Transverse plane.
3. Vertical plane.
3. Location of dental arches in the head.
1. Rotation in horizontal plane
2. Rotation in frontal plane
3. Lateral translation
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57. Antero-posterior position:
Posterior segment.
Ex - Class II sub div or Class III sub div
o This type of dental relation is seen in early/delayed
exfoliation of deciduous teeth.
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58. Anterior segment:
Upper/ lower anterior midline can be deviated because
1. early exfoliation of deciduous canine,
2. ectopic eruption or missing upper/ lower permanent
lateral incisors
3. peg shaped upper lateral incisors which might lead to
abnormal canine as well as incisor relationship.
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59. Transverse plane:
Dental asymmetry in the transverse plane can be due to
constricted maxillary/mandibular arch because of
1. digit sucking or mouth breathing habit
2. abnormal posture of the tongue.
3. Asymmetric chewing habits
4. Extraction of deciduous/permanent teeth
5. trauma
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60. Model analysis like Bolton’s should be considered in
correction of midlines.
The tooth size discrepancy can be corrected either by
restoring (build up) of small sized teeth or interproximal
reduction of larger teeth.
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61. Vertical plane:
Vertical discrepancy in
the arches can lead to a
cant in the occlusal
plane.
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63. 1. Maxilla
2. Mandible
3. Combination of both
Maxilla
o Constriction of basal arch- posterior crossbite
o Rotational changes relative to cranial base-asymmetric
occlusion
o Congenital anomalies-clefts
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64. Mandibular
o Abnormal growth of cranial base-position of glenoid fossa
o Congenital
o Hemifacial microsomia
o Trauma to mandibular condyle- scarring, fibrosis
o Unilateral condylar hypertrophy
o Infections – ankylosis
o Rheumatoid arthritis-destruction of TMJ & disc.
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65. Muscular asymmetries
o Hemifacial atrophy
o Cerebral palsy
o Soft tissue-masseter muscle hypertrophy
Functional problems
o Occlusal intrerferences
o Malposed tooth
o TMJ disorders- ant. Disc displacement without reduction
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66. Midline diastema refers to anterior midline spacing between
the two central incisors.
ETIOLOGY
1.NORMAL DEVELOPING DENTITION
Physiologic median diastema/ ugly duckling stage
Ethnic and familial
Imperfect fusion of midline of premaxilla
2. TOOTH MATERIAL DEFICIENCY
Microdontia
Macrognathia
Missing lateral
Peg laterals
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Extracted tooth
68. It is a transient or self correcting malocclusion which is
seen in the maxillary incisor region between 8-9 years. It is
particularly seen during the eruption of the permanent
canines.
As the permanent canines erupt they displace the roots of
the lateral incisors mesially.
This causes a divergence of the crowns of the two central
incisors causing a midline spacing.
This was described by Broadbent as the ugly duckling stage
as children tend to look ugly during this phase of
development. So it also known as Broadbent phenomenon.
It is a self correcting anomaly.
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69. 1. Selection of treatment midline.
2. Apical base discrepancy is 2mm- ass. with molar
occlusion- U/L midline which is closest to facial
2 nov 2011 69
70. 1. bracket placement: in apicalbase discrepancy, incisal brackets
are angulated- results in tipping.
2. Cantilevers – uprighting tipped incisors.
3. Asymmetric extractions
4. Varying time of extraction
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72. Age of the patient.
Growing individual with mild
asymmetry –
Growth modulation using Hybrid
appliances .
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73. Functional shift of the mandible due to maxillary constriction:
Treatment
Expansion of maxilla.
Unilateral Fixed Functional Appliances –
Jasper Jumper, Churro’s or Fielo’s appliance.
2 nov 2011 73
74. Moderate to severe asymmetries →
Distraction osteogenesis
2 nov 2011 74
75. Guidelines –
o More concern about transverse than vertical asymmetry
o More concern about chin position than mandibular angles
o Maxillary midline more critical than mandibular midline
o If nose and jaw are deviated to the same side, both should be
corrected
o Asymmetry of higher structures - infra-orbital
rims, Zygomatic arch – onlay grafts should be considered
2 nov 2011 75
76. o Unilateral or bilateral constriction of the upper arch/lower arch
in conjunction with a functional shift of the mandible.
o Sutural patency
o Conventional rapid palatal expansion
o Surgical assisted palatal expansion
A mandibular bilateral constriction can be corrected →
oIn growing individuals: expansion appliances (tooth-borne
appliances) can be used.
oSympyseal distraction (bone-borne).
oOrthognathic surgical procedure .
2 nov 2011 76
77. Dental asymmetries can exist in solo or in combination with a
skeletal problem; but, the rectification strategies remain the
same.
Asymmetric Midlines ( Antero-posterior / transverse plane):
1. In Begg Appliance
o placing uprighting springs on the side to which the midline
is shifted along with Class II elastics or Class I elastics on
the opposite side.
o Diagonal elastics can also be used.
2 nov 2011 77
78. In PAE:
oMidline shift because of tipping of the incisors can be
corrected by ligating figure of 8 ligature wire, which causes
tipping of the engaged teeth.
oMidline corrections by bodily movement can be achieved using
PAE brackets with a combination of open loop and a closed loop
design in a rectangular S.S wire or by using a fixed functional
appliances .
2 nov 2011 78
79. TREATMENT OF CROSS BITE
factors to be considered
1.Age and growth potential of the individual
2.Type of cross bite- dental or skeletal
3.Anterior or posterior
APPLIANCES USED
REMOVEABLE APPLIANCE-includes catlans appliance posterior bite plane with Z
spring
BANDED APPLIANCE -lingual arch, quad helix
MYOFUNCTIONAL APPLIANCE face mask for maxillary retrusion reverese
activator, FR III and chin cap for excessive mandibular growth
EXPANSION SDREWS- slow and rapid palatal expansion screws
FIXED APPLIANCE-asymmectrically expanded arch wire and cross elastics
OCCLUSAL GRINDING- if the asymmetry is due to any occlusal interferences
2 nov 2011 79
80. Although some amount of discrepancy is
treated as normal,….
Correction of midline discrepancies and
asymmetric molar relationships need a
careful diagnosis, treatment plan and
biomechanical plan in order to achieve
predictable results.
2 nov 2011 80
