management of asymmetry and canting.pptx

Diagnosis and
management of
asymmetry and canting
BY DR. DIDA BORU(DMD, MDS, ASSISTANT PROFESSOR AT JIMMA
UNIVERSITY)

outlines
 introduction
 classification
 Aetiology
 Evaluation of facial symmetry in three planes of space
 Prevalence of dentofacial asymmetries
 Dental midline deviations
 Definition and evaluation
 Effects of an altered tip of the incisors on the midline
 Reference planes

outlines
 Prevalence of midline deviations
 Clinical presentation of dental midline deviations
 Aetiology of the dental midline shift
 Management of dental midline shifts of purely dental origin
 Asymmetry of occlusion
 Definition and criteria of asymmetric occlusion
 Development of asymmetries with dental arches

outlines
 Common traits of asymmetrical occlusion
 Prevalence and features of asymmetrical occlusion
 Management Class II subdivision malocclusion
 Molar distalisation Asymmetric extractions
 Orthopaedic asymmetrical approach Class III subdivision malocclusion
 Cant of occlusal plane in transverse direction
 Introduction and definition

outlines
Aetiology of occlusal cant
 Clinical presentation and diagnosis
 Reference planes
MDCT/CBCT
 Management of canting

Introduction
 The word symmetry is derived from the Greek word ‘symmetria’ which means ‘of
like measure’. Symmetry which is defined as correspondence in size, shape and
relative position of parts on opposite sides of a dividing line or medianplane.
 Asymmetry is described as a lack or absence of symmetry. When applying this to
the human face, it illustrates an imbalance or disproportionality between the right
and left sides.
 A degree of asymmetry is normal and acceptable in the average face.
However, the importance of early diagnosis and the detection of progressive
causative conditions is essential for the management of facial asymmetry.

Introduction
 Facial asymmetry (FA) refers to the absence of, or the deviation from
the regular mirror image of facial structures, relative to a referenced midline
axis, and it is clinically perceived as an imbalance or difference in the proportion
of two sides of the face
 Symmetrical appearances frequently show variations, owing to embryonic
tissue development, evolutionary and environmental factors

Introduction
 Absolute symmetry in biological specimens including human body
and face is rare
 Slight facial asymmetry can be found in normal individuals, even in those
with aesthetically attractive faces.
 Right–left differences do exist in nature where two bilateral congruent
parts present in an entity.
 Humans frequently experience functional, as well as morphological
asymmetries

Introduction
 FA can be attributed to a wide spectrum of deformities, including congenital,
developmental, or acquired conditions, which can originate either prenatally or
postnatally, from hard or soft tissue facial, maxillofacial, and oral structures.
They may be perceived at rest (a.k.a. Static) or during facial expressions (a.k.a.
Dynamic)
 May pose as aesthetic, functional, and psychosocial concerns.

Classification of facial asymmetry
 Facial asymmetry does affect the craniofacial skeleton in any/all the
three planes of space.
 It is most easily assessed in the full face or frontal view.
 Several classification systems have been devised to assist in the
management of facial asymmetry

Type
I
Asymmetry caused by asymmetry of the symphysis of the mandible.
The maxilla and the body of the mandible are symmetric with the dental midlines in the
centre of the face.
Type
II
Facial asymmetry in which the discrepancy is primarily in the body, ramus or condyle of the
mandible. The maxillary dental midline coincides with the facial midline and the mandibular
dental midline coincide with the symphysial midline.
Type
III
Asymmetry in which the maxillary midline is still coincident to the facial midline, but the
mandibular midline is asymmetric to the maxillary midline and the symphysis is still more
asymmetric to the mandible.
Type
IV
Facial asymmetry, in which the discrepancy involves the maxilla, mandible and the
symphysis. The maxillary midline is asymmetric to the facial midline while the body of the
mandible to the maxillary midline is further asymmetric (mandibular midline is
asymmetric), and the mandibular symphysis is asymmetric to the body of the mandible.
Type
C:
Depicts facial asymmetry caused by a cant in the occlusal plane while the maxillary and
mandibular dental midlines and symphysiscoincide.
Box The categorisation
of facial asymmetry
by Reyneke (1997)

Facial asymmetry.
Structural classifications by Reyneke.

Classification
Author Based on details
Plint(1974) Etiology Laterocclusion (apparent
asymmetry due to occlusal
disharmony )
Laterognathism ( true facial
asymmetry )
Obwegeser and Makek (1986)
mandible only
morphology Hemi-mandibular elongation
Hemi-mandibular hyperplasia
Combined

Classification
Author Based on details
Bishara (1994) Involved structure
• Dental
a) Congenitally missing tooth or teeth
b) Premature loss of deciduous teeth
c) Deleterious oral habit
d) Midline discrepancies
e) Occlusal discrepancies
• Skeletal
a) Involving mandible and maxilla
b) Involving number of skeletal structures on one side of face as in
hemifacial macrosomia and Treacher Collin syndrome

Classification
Author Based on Details
Bishara (1994) Involved structure
• Muscular
a) Hemifacial macrosomia
b) Mobius syndrome
c) Cerebral palsy
d) Unilateral masseter or temporal
muscle hypertrophy
e) Untreated cases of torticollis
• Functional
• combination

Aetiology
 Some of the asymmetries are embryonically or genetically
determined and encoded in the central nervous system.
 Preferential laterality for some anomalies is striking, such as cleft
lip, which occurs more commonly on the left side.
Left–right tooth crown size asymmetry, evident by measurement, is
also a normal state in the general population

Aetiology
 When facial asymmetry is part of skeletal malocclusion, there is a
decrease of NSP genes in the masseter muscle.
 It has been found that NSP gene downregulation promotes the
development of asymmetry.
Pitx2 expression differences also contribute to both skeletal and
muscle development in facial asymmetry

Major causes of facial asymmetry

Diagnostic Evaluation for Acquired Facial
Maxillofacial, and Oral Asymmetries
Acquired FAs are predisposed by various external factors;
hence, an accurate diagnosis of these cases consists of a thorough…..
I. medical/dental history check-up
II. clinical examinations
III. study models
IV. photographic and radiographic records.

Medical and Dental History
 Following the patient’s chief complaint and evaluation of their medical and
dental history helps clinicians identify the precise cause of the asymmetry.
 Childhood traumas or infections related to the craniofacial area and records of
dental history, such as abnormal eruption or premature loss of the dentition,
should also be taken into account

Clinical Examinations
Extra oral evaluation
 Direct frontal assessment is performed with both visual and palpable
inspection of the facial framework, to detect any differences between the two
halves of the face.
◦ patients tend to mask their asymmetric appearance by titled head postures or
customized hairstyles.
◦ Thus, during the extra-oral evaluation, clinicians should keep the patient’s
face unveiled and the head in the standard position, as per the clinical
Frankfort plane or the interpupillary line, and parallel to the floor.

 Clinical FA may be due to disharmony in the skeletal, soft tissue, dental, and
functional structures of the face.
 The contribution of dental structures may cause minimal FA. However,
asymmetries of skeletal origin attribute to significant changes in an individual’s
facial harmony, owing to extensive involvement of the adjacent hard tissue
structures.
 Commonly encountered mandibular asymmetries, for instance, may produce
changes in size, volume, and position of the condyle or ramus, leading to
secondary skeletal changes in the maxillary counterparts.

 The gold standard for visible FA is considered as a skeletal deviation equal to or
greater than 4 mm.
 The degree of skeletal asymmetry may also be compensated by individual-
specific soft tissue thickness; thus, some authors suggest a craniofacial deviation
of 2 mm deviation as clinically discernible asymmetry
 The first step in examining facial symmetry is determining the reference
midlines of the face. The reference upper midline is often established by the line
connecting through soft tissue Glabella (G’—the center point of the eyebrows)
and Subnasale (Sn—the central point of the nasal septum and the upper lip)
points.

 Following this reference line, clinicians can assess the upper facial symmetry,
and any remarkable deviations from this line should be noted and examined
carefully.
 Regarding the lower midline, some authors consider a reference line through
Sn and Pogonion (Pg’—the most projecting median point on the anterior surface
of the chin.).
 If the reference lower midline is aligned with the upper midline, the chin is
centered, otherwise, the mandible is considered shifted and further
investigation should be made to determine whether the mandibular deviation is
functional or not

 The imaginary mid-pupillary line and the facial midline can
divide the face into four parts for gross evaluation, as displayed in Figure 1

Fig 2 Frontal view photographs of two patients at rest
and at smiling. An imaginary midpupillary line and a
facial median line are dividing the face into four parts
for asymmetric evaluation. Both patients are diagnosed
with FA with regard to these two reference lines. While
the first patient’s face (above) only displays
indiscernible asymmetric patterns, that can be
aesthetically acceptable, the second patient (lower) has
a greater degree of FA due to the shift of the mandible
to the right side. Therefore, the latter needs both
orthodontic treatment and surgical correction for the
optimal result of facial symmetry

 Another measurement for facial symmetry is “the rule of the fifths”. The
transverse proportions of the face are divided into five equal parts.
 Regarding the ideal facial aesthetics, each vertical fifth should have the
approximate width of an eye.
 The central fifth is measured by the interior intercanthal distance between two
eyes, this width is considered ideal if it is corresponding to the width of the
interalar base of the nose.

 The median two-fifths are characterized by the inner and lateral canthus of
both eyes. Lastly, the lateral two-fifths of the face are evaluated from the
furthest edge of the ears to the lateral canthus of the eyes.
 While the vertical fifth measurement can be utilized on both genders , the ratio
may vary depending on ethnicity and race
 Some authors also discovered that the nose width in the black population is
relatively greater than that of other populations

Fig 3. Facial proportions and symmetry in the frontal plane.
An ideally proportional face can be divided into central,
medial, and lateral equal fifths. The separation of the eyes
and the width of the eyes, which should be equal, determine
the central and medial fifths. The nose and chin
should be centered within the central fifth, with the width of
the nose the same as or slightly wider than the central fifth.
The interpupillary distance (dashed line) should equal the
width of the mouth.

Identifying the asymmetry
 The photos of a balanced face and beautiful model created by
collating the mirror image of each of the two halves, right to the
right and left to left have resulted in faces different from each other
and the untouched.
 Three pictures thus created will appear as (1) untouched apparently
symmetrical, (2) symmetrical made from right halves of
the face and its mirror image and (3) symmetrical but different from
previous two made by left half of the face and its mirror image.

Fig 4 Computerised images
of a relatively symmetric
face
reveal the extent of
asymmetry in each of us.
(A) This image is the original
photo of the patient.
(B) This composite is
made up of the patient’s left
side with a flipped mirror
image representing her right
side. (C) This composite is
similarly created with
two right sides. The effect
demonstrates how each half
of the patient’s face is
different. This can be an
interesting way to begin the
conversation about
asymmetries.

Identifying the asymmetry
 The point at which ‘normal’ asymmetry becomes ‘abnormal’ cannot be
easily defined for it is often determined by the clinician’s sense of balance
and patient’s sense of imbalance.
 According to the research study by Beyer and Lindauer, generally
speaking, a 2 mm (2.2 ± 1.5 mm) or greater deviation of the dental
midline appears to be easily detectable.
 However, in a recent study, Pinho concluded that midline shifts became
perceptible when equal to or greater than 1.0 mm for orthodontists and
3.0 mm for prostho-dontists; lay persons saw no alteration.

Evaluation of facial symmetry in three planes of space
 Facial asymmetry is a complex morphological disorder and needs to
be evaluated in X, Y and Z-axis including cant of occlusal plane and
depth of curve of Spee.
Three aeronautical rotational descriptors (pitch, roll and yaw) are
used here to supplement the planar terms (anteroposterior,
transverse and vertical) in describing the orientation
of the line of occlusion and the aesthetic line of the dentition

Fig 5 The face and its structures
should be evaluated in all three planes
of space, i.e. sagittal, vertical and
transverse.
A relatively new concept proposed by
Ackerman, describing the spatial
orientation of dentofacial traits in a
fashion similar to the aeroplane’s
movement. 3D analysis of orientation
of the head, jaws and dentition is
incomplete without also considering
three rotational axes of pitch, roll and
yaw in addition to planar terms
anteroposterior, transverse and
vertical

 Pitch
The cant of occlusion in the sagittal plane, which makes the dentition
downward or upward displacement viewed along the aesthetic line, is
best described as translation (no tilt) or pitch upward or downward
anteriorly or posteriorly.
 Roll
The Rotation of so called occlusal plane in a transverse plane or
aesthetic line of dentition around a horizontal axis, up or down on
right or left side, is best described as a roll. A fox plane used is
prosthetics can help visualise the roll left or right.

 Yaw
When the entire dentition/jaw is asymmetric and rotated around an
axis presenting as asymmetry is described as yaw. A class III
malocclusion with posterior cross-bites, buccal on one and lingual on
the other is an example of yaw.

Fig 6 Chin: the hallmark of facial symmetry
 Facial symmetry is first evaluated with
chin point or menton, the hallmark of facial
asymmetry.
 Facial asymmetry has been perceived to
be clinically relevant when chin/menton
deviation is by 4 mm or menton deviations
of 4.28 and more
Shows yaw of jaw

Diagnostic Records
Comprehensive records of study models, photographic and radiographic
assessments are collected as an aid for measuring the degree of FA.
 The first step is to obtain standardized photographs of the patients, which
include extra-oral shots of the frontal, lateral, submental, and superior views,
intra-oral ones of each dental arch, and frontal and lateral view of the occlusion
in the centric position

Diagnostic Records
 Conventional cast models or virtual occlusograms of the patients are then taken
for a thorough evaluation.
 Appropriate study models transferred onto an adaptable articulator will provide
clinicians with a better perspective of two dental arches and their relationships.
 radiographic records are also essential to detect underlying hard tissue
irregularities that are usually undiscovered by clinical examination
 Two principal radiographs that are often prescribed for the diagnosis of
asymmetry are the posterior-anterior cephalogram and orthopantomogram

Diagnostic Records
Other advanced diagnostic procedures, such as stereophotogrammetry, 3D
stereolithographic models, and skeletal scintigraphy (radionucleotide scans),
have also been promoted as effective tools for FA diagnosis.
 The application of these three-dimensional imaging techniques for surface
asymmetric evaluation has been increasing enormously in recent years,
especially digital stereophotogrammetry, owing to its lack of exposure to
radiation and lack of requirements for patient compliance

Diagnostic Records
 Recently, more sophisticated techniques, such as 3D computed tomographic
scans, cone beam-computed tomography (CBCT), and magnetic resonance
imaging (MRI), have provided innovative diagnostic instruments for numerous
craniofacial defects
 The CBCT technique is widely used for the detection of maxillofacial bony
changes, such as tumors, fractures, osteitis, idiopathic osteosclerosis, and
condylar hyperplasia, as it can produce excellent details of the surrounding
tissues, with a relatively low dose of radiation

Evaluation of facial asymmetry using photographs.
The special views required. The facial asymmetry is much
more appreciated in submental view.

Management strategy of facial asymmetry
 Mild asymmetry with no other pathologies in growing children
 Mild asymmetry of the face with malocclusion treated with
orthodontics alone
 Mild asymmetry of the face with mild malocclusion treated with
minor surgical procedures such as genioplasty with or without
orthodontics
 Severe asymmetry treated with a combination of orthodontics and
orthognathic surgery

Management of facial asymmetry in a growing
individual.
Class II growing patient with mandibular deficiency. Presence of
mild facial asymmetry with deviation of the chin to the left. Initial
extraoral (A, B and C) and intraoral photographs (D, E, F, G and
H), as well as profile, panoramic and carpal radiographs (I, J and
K). Source: Reproduced with permission from Thiesen G, Gribel
BF, Freitas MP. Facial asymmetry: a current review. Dental Press
J Orthod 2015 Nov– Dec;20(6):110–25.

(A) Telescopic mechanism of the Herbst appliance
in place. Asymmetrical mandibular advancement was aimed at
correcting skeletal occlusal and facial asymmetry. Lateral intraoral
photographs on the right side, (B) in frontal view and (C) on the left
side. (C) Treatment outcomes for the patient presented after the
second phase of treatment conducted with a full fixed orthodontic
appliance. Final extraoral (A, B and C) and intraoral (D, E, F, G and
H) photographs. Profile and panoramic radiographs (I and J).
Source: Thiesen G, Gribel BF, Freitas MP. Facial asymmetry: a
current review.
Dental Press J Orthod 2015 Nov-Dec; 20(6):110–25.

Dental midline deviations
 Dental asymmetry or centre line deviations may be the outcome of
discrepancies in tooth dimensions or improper placement of dental units within
normal/symmetrical underlying jaw bones or be the outcome of asymmetrical
skeletal bases housing the dental units.
 Dental midline or centre line is evaluated at the junction of contact points of
the mesial surface of the central incisors in each arch.
Midline symmetry or deviations are recorded as coincident or non-coincident
to face and to each other

The dental midlines must coincide
with facial midlines.
Therefore, the dental midline is
assessed in relation to the facial
midline. MSR is used as a reference
plane to evaluate the deviations.
MSR is an imaginary line that divides
the face into two halves.

Dental midline deviations
The maxillary dental arch midline is expected to coincide with midsagittal line of
the face and midline of the maxilla.
 mandibular dental midline is supposed to be placed in mid dental arch of the
mandibular symphysis and the face.
 Both maxillary and mandibular midlines are expected to be coincident with
each other and to the midline of the face.
 The dental midlines are evaluated with
1. teeth in occlusion
2. on the opening of the mandible

Definition and evaluation
 Dental midline shifts more than 2 mm are usually considered a matter
of concern, for these deviations compromise attractiveness of the face.
 It was estimated that the probability of a layperson recording a less
favourable attractiveness score when there was a 2-mm discrepancy
between the dental and facial midlines was 56%

A perfect coincidence of
maxillary and mandibular
midlines is desirable though
rare.
Up to 1 mm of midline
deviations is acceptable.
Note slight shift of
maxillary midline to right in
a girl following orthodontic
treatment. The
occlusion is perfect with
class I molar and canine
relationship. Bold
white line: refers to MSR;
red line: maxillary midline;
yellow line: mandibular
midline.

Reference planes
1. Mid-sagittal reference (MSR) plane.
• It corresponds to a median plane that divides the body into two halves.
• It is mainly constructed or follows the average of mid-sagittal structures of the
skull.
• MSR extends down from the head, in natural head position (NHP) or when a
subject is sitting upright or standing vertically.
• The face is bisected by a midsagittal vertical line running through the head, the
centre of nose, lips and chin.

Reference planes
 MSR plane can be visualised as an imaginary vertical, or plumb line
outside the face dropped at glabella.
 The plumb line also bisects dorsum of the nasal tip equidistantly
unless there is an asymmetrical nose.
In dental clinical settings MSR plane is easily visualised with a piece
of long floss or a ruler

Reference planes
2. Philtrum of the upper lip
 The ‘V’ at the vermillion border forms a suitable landmark that is much easily
appreciated by orthodontists and patients
 Arnett and Bergman noted that the philtrum is usually a reliable
midline structure and can, in most instances, be used as the basis for
midline assessment.

Reference planes
3 Corners of mouth
 Another guide for assessment of midline is to look at the distance
between the canine or first premolar and the corner of the mouth.
 If the midline is properly positioned, the patient will see the same
amount of tooth exposure on the right and left side.
4 Mid palatal raphe
5 Symphysis of the mandible
6 The base of dentoalveolar structures
7 Angulation of the incisors

Evaluation of midline shift in a clinical
setting.
(A) Using a long piece of dental floss.
(B) Using a ruler.

The ‘V’ at the vermillion border forms a
suitable landmark for the dental
midline evaluation that is much easily
appreciated by orthodontists and
patients. Source: Reproduced with
permission from Burstone CJ.
Diagnosis and treatment planning of
patients with asymmetries.Semin
Orthod. 1998 Sep;4(3):153–64.

(A) The dental and skeletal midlines are evaluated
in relation to MSR, which is constructed on a
conventional PA cephalogram. Incisor apical base
discrepancy between upper and lower arches.
Arbitrary skeletal mid-sagittal plane passes
through the lower apical base midline. (B) Upper
dental midline to the right of the lower midline.
Skeletal problem with apical base discrepancy. (C)
Upper midline to the right without an apical base
discrepancy. Upper incisors are tipped towards the
right. (D) Dental midlines correspond. Apical base
discrepancy is masked by compensatory tipping of
the upper incisors to the left side. Source:
Reproduced with permission from Burstone CJ.
Diagnosis and treatment planning of patients with
asymmetries. Semin Orthod. 1998 Sep;4(3):153–
64.

Clinical presentation of dental midline deviations
 Jerrold and Lowenstein (1990) described following major possible clinical
situations on midline deviations.
 Group A: Local/dentoalveolar type of midline shift when the face is symmetric,
and there are no major skeletal deviations. Four clinical situations can exist.
 1. When maxillary midline is off to the right or left side
2. A clinical situation in which both maxillary and mandibular midlines are
coincident but both are off from the centre line of the face in the same
direction. Both have moved to the right or left side.

3. A clinical situation when face, maxilla, mandible and maxillary midlines are
coincident however mandibular midline is off to centre line or plumb line of the
face.
4. While facial midline is correctly centred, the maxillary midline and mandibular
midlines are not in alignment due to the shift of each of them in their respective
jaws in a direction opposite to each other

Group B: Dental asymmetry comprises clinical situations of facial asymmetry
functional or true skeletal deviations.
The dental midline deviations may or may not be present. A major cause of such
asymmetries in otherwise normal faces involves a lateral functional shift of the
mandible.
1. The functional lateral shift of the mandible.
2. Occasionally in a situation as described in above (1) the local tilting or shifting
of teeth may lead to maxillary and mandibular midline coinciding while chin
remains deviated.
3. Both maxillary and mandibular midlines are coincident but deviated from
midline of the face to the side of chin deviation.

Aetiology of the dental midline shift
1. During the development of dentition, several dental factors can cause
asymmetry of the dental arches and midline shift.
a) Side differences in the pattern of exfoliation.
b) Position and orientation of the developing successor tooth buds in the
eruptive phase, eruption path ways
c) Differences in the site of tooth emergence, the sequence of eruption and
position of the antagonist.
d) Tooth rotations occur consequently to lack of space in the arch
e) Transverse problems in the dental arch or its bases leading to crowding
of the anterior segment are associated with midline shift.

Aetiology of the dental midline shift
f. If anterior crowding results in an infra-position of canine or a palatally
positioned lateral incisor on one side, this leads to an upper midline shift
towards the crowded side.
g. Missing teeth/partial hypodontia, microdontic teeth leading to migration of
adjacent teeth, a situation often seen in missing maxillary lateral
incisors/missing second premolars/microdontic
laterals.
h. Deleterious oral habits, influencing facial morphology.
i. Mandibular functional shift or deflective contacts due to cross-bite.
j. The tooth-size discrepancy, unusually large teeth, such as macrodontia.

(A) Midline shift due to
microdontic laterals.
(B) Midline shift with
missing laterals;
(C) midline shift associated
with a mesiodens.

Midline shift with
palatally placed
lateral incisor.
Lower midline shifted towards canine
displacement in severe crowded case.

Midline shift in a
cleft patient.

Case of lower midline shift and
asymmetrical malocclusion associated
with class II division 2 malocclusion.
The left mandibular lateral incisor is
lingually displaced, leading to
shifting of lower midline to the left and
class I molar relation on that
side. Molar relation and canine
relationship on the right side remain
class II.

Midline shift due to premature functional
contacts.
(A) Midline shift in centric occlusion;
(B) maxillary and mandibular
midline coinciding during closure of mandible
with first initial contact
Midline shift due to periodontal migration.

Management of dental midline shifts of purely dental
origin
 Midline deviations in subjects with the normal skeletal pattern with no
apparent asymmetry of face, skeleton and occlusion can be corrected with
orthodontic mechanics alone.
 Subjects in which midline correction is required to correct migration of teeth
in spaces created by partial hypodontia or microdontic teeth will require one of
the following treatment plans to attain good proximal contacts:
1. Orthodontic space closure,
2. Prosthetic rehabilitation of the available space of a missing
tooth or teeth, and/or, and
3. Aesthetic restorations of the microdontic teeth to normal
dimensions.

Management of dental midline shifts of purely dental origin
 Asymmetric anchorage loss is associated with midline deviations which tend to
appear during stages of finishing. These clinical situations often require complex
orthodontic mechanics though the problem may initially appear simple.
 The force systems used for dental midline correction
1. Simple cantilever mechanics for tipped incisors
2. Simple cantilever mechanics for translation of incisors
3. Looped arch wire mechanics for bodily movement
a. Looped mechanics with push force
b. Looped mechanics with pull force
c. Looped mechanics with a combination of pull and push force
d. Open coil spring

Management of dental midline shifts of purely dental origin
4. Correction of midline with a simultaneous resolution of crowding
5. Correction of midline with the transverse expansion of the maxilla
6. Correction of midline with unilateral molar distalisation or asymmetric
extraction

Treatment of midline deviation in the mandible with use of cantilever forces.
(A) Midline discrepancy caused by tipping of the lower incisors. A simple force at the crowns of the teeth generated from molar
without an archwire will upright the incisors and achieve midline coincidence (A1). And midline correction by tipping (A2). (B)
Midline correction by translation. (B1) An anterior wire with a loop extended apically to approximate the centre of resistance of
the incisor teeth to provide a contact point for the force. (B2) A force applied through the centre of resistance will produce a
translation. The red dot represents the centre of resistance. Source: Reproduced with permission from Kulberg AJ Cantilever
springs: force systems and clinical applications. Semin Orthod 2001;7:150–9.

Treatment of midline deviation in the maxilla in a
continuous wire with a looped mechanism.
Migration of central incisors caused midline discrepancy to the
opposite side, across midline due to a missing contralateral lateral
incisor. (A) Pull force; (B) push force; (C) combination of pull and
pushnforce; (D) push coil spring

Dental midline and transverse deficiency of
maxilla.
(A) Bilateral constricted maxilla with upper midline shift; (B) type 1 RME appliance in the
mouth; (C) end of expansion; (D) correction of upper midline shift at the end of the retention
period. Source: Reproduced with permission from Alcan T, Ceylanoğlu C. Upper midline
correction in conjunction with rapid maxillary expansion. Am J Orthod Dentofacial
Orthop. 2006 Nov;130(5):671–5.

Asymmetry of occlusion
 Asymmetric occlusal relationships can result from an asymmetry within a single arch or
asymmetric skeletal relationships between the maxilla and the mandible.
 People with normal occlusion can have molar asymmetry greater than 1 mm in transverse and
anteroposterior directions
 The cause of asymmetries in the molar relationship can be multivariate. In some patients, the
problem originates with an abnormal dental eruption, premature loss of primary teeth, or loss
of permanent teeth; however, in other patients, the origin may be primarily skeletal in which an
asymmetric maxilla or, more likely, an asymmetric mandible is present

A case of mild asymmetry of
malocclusion.
There is a 2 mm midline shift of
the mandible to the right, left side
a mild class III premolar and molar
relationship, and mild class II
molar and canine on the right
side.

Development of asymmetries within dental arches
 Ankyloses of primary molars
 Ectopic eruptions of the maxillary permanent first molars
 Partial hypodontia
 Dental caries

Common traits of asymmetrical occlusion
 Asymmetric conditions of occlusion that can be possibly
managed with orthodontic treatment are:
1. Asymmetrical molar relationship
2. Asymmetrical canine relationship
3. Asymmetrical overjet
4. Asymmetrical overbite

Clinical evaluation
 A detailed clinical and radiological evaluation of the case with asymmetrical
occlusion is fundamental to establish the nature and severity of the problem.
 A comprehensive 3D evaluation with CBCT remains the gold standard to
measure the exact location and severity of the asymmetry; however, CBCT
should only be, prescribed with caution keeping in view Sedentexct guidelines
on the use of CBCT

CBCT applications in facial asymmetry.
(A) Facial asymmetry as visualised on a volume-rendered
CBCT image. (B, C)Maxillary dental midline deviation
caused by ‘Yaw’ of the maxilla.

Clinical evaluation
 The study models can be photocopied on occlusal view or scanned as 1:1 for evaluation
 One can use symmetry grid over the occlusal surface of the dental arch
 The asymmetric occlusion segment should be evaluated for excessive rotation of the teeth,
unusual tip and buccolingual position in the arch, such as a cross-bite or the excessive buccal-
palatal tip
Use of symmeterograph

Clinical evaluation
 Shroff and Siegel have recommended evaluation of rotation of the molars by
drawing a line along the mesial surface of the molar on each side of the arch and
observe the point of intersection of these two lines.
 If the right and left molars have the same amount of rotation, these lines will
intersect at the median raphe.
 If the right molar is more rotated than the left molar, the lines will intersect on
the right side of the arch

Assessment of molar rotation.
(A) Trace a line along the mesial surface of the molars on each side of
the arch. (B) If the molar rotation is bilateral and of equal amount, these
two lines will intersect at the median raphe. (C) If the molar rotation is
on one side only, these two lines will intersect on the side of the rotated
molar.

Management of asymmetric occlusion
 Depending on the patient’s age and the severity of the condition, a variety of
orthodontic and orthopedic options have been described in the literature.
• Asymmetrical mechanics
■ Molar distalisation
• Asymmetrical extractions
• Asymmetrical orthopaedic appliance activation
• Surgical interventions

Class II subdivision malocclusion
 Most class II subdivision malocclusion patients present with mandibular dental
midline displaced towards class II side.
Such a clinical situation depicting mild asymmetry, asymmetrical mechanics and
extractions tend to yield good results
 Asymmetrical mechanics necessarily involves orthodontic non extraction
treatment whereby heavy class II elastics are used on class II side and light
elastics on class I side.
Similarly, the severity of tip back bends in the maxillary archwire can be
enhanced on class II molar side.

A case of unilateral molar distalisation.
Top row: Pre-treatment occlusion. Middle
row (left): Shows molar
distalisation with a Jones Jig-type sectional
assembly. Right side: Shows occlusion
settlement with a fixed appliance. Bottom
row: Stable occlusion at 15 years of follow-
up. Note perfect interdigitation. A mild
midline deviation persists.
Molar
distalisation

Asymmetrical extractions.
(A–J) A case of class II subdivision malocclusion on the
right side with mild facial asymmetry with deviation of
the mandible to the right.
Source: Reproduced with permission from: Thiesen G,
Gribel BF, Freitas MP. Facial asymmetry: a current review.
Dental Press J Orthod
2015;20(6):110–25.

Treatment outcome with asymmetric extraction
pattern.
(A–J) The protrusion, crowding are corrected. Lower
midline is now coinciding with patient’s median sagittal
plane. The molar relationship is now full-cusp class II
with class I canine relation on the right side and
class I molar and canine on the left side.

Unilateral maxillary first premolar extraction
 This plan of treatment works out well in cases where unilateral class II molar
relationship exists because of mesially migrated maxillary first molar on one side
leading to midline shift and crowding in the maxillary canine/anterior region.
 In situations where maxillary molar distalisation cannot be considered due to
the age of the patient or severity of the crowding, unilateral extraction of the
maxillary first premolar is the treatment of choice.
 This approach will simultaneously correct the midline.

Class III subdivision malocclusion
 Class III malocclusion leading to the mandibular dental midline deviations may
present with anterior teeth in an edge-to-edge or even cross-bite relationship,
with asymmetrical overjet.
The option of one mandibular premolar extraction on the class III side would
allow for primarily class I closure mechanics, and minimize inter-arch elastics
 Class III subdivision malocclusion in subjects with a full component of teeth,
past pubertal growth spurt and one which does not have significant skeletal
dysmorphology can be considered for intra arch lower molar distalisation with
mini screw supported anchorage from retro-molar region

Cant of occlusal plane
Introduction and definition
 Cant of the occlusal plane more commonly refers to change in the inclination of
the occlusal plane showing a tilt, when viewed from the front
 Any canting of occlusal plane in frontal plane affecting smile aesthetics
originates from the vertical plane.
 canting of occlusal plane in frontal plane affecting smile aesthetics originates
mainly from facial asymmetry and/or vertical position asymmetry of the right
and/or left quadrants of the dental arches.

An adult who reported asymmetrical
show of teeth during the smile.
A case with class II division 1 malocclusion
with excellent soft tissue compensation
resulting in excellent facial profile with
lips in resting position. While smiling, she
shows a cant of an occlusal plane on her
left side which extends from left central
incisor to second molar teeth.
The left maxillary segment is in
infraocclusion in reference to the
palatal plane and occlusal plane on
another side.

 It has been reported that the detection rate for both untrained and trained
observers surpassed 50% at 3° of occlusal canting.
 Cants greater than 4° were detected 90% of the time by untrained observers
and 98% of the time by trained observers.
 Padwa et al. concluded that 4°, as the threshold at which occlusal cants are
detected with greater than 90% frequency and 3° is the threshold for greater
than 50% frequency.

 Occlusal cants of 0–3° are seen in normal occlusion subjects.
The cant up to 3° will not be noticeable, and occlusal canting of this magnitude
probably does not have detrimental effects on postoperative outcome.
 Any efforts to alter this inclination of cant with restorative or surgical
procedures are not desired and may have an adverse effect on TMJ.

Aetiology of occlusal cant
 Asymmetrical growth of the mandible
 Facial asymmetry
 Faulty biomechanics

Cant of occlusal plane in a subject
with unilateral ankylosis of the
mandible.
This patient has undergone
condylectomy of the left side. Note a
deviation of the chin on the affected
side.

A case of occlusal plane in a
subject with unilateral
condylar hyperplasia of the left
side.

Clinical presentation and diagnosis
 Subjects with suspected or apparent asymmetry are evaluated
through
 clinical examination
 frontal photographs
 posteroanterior (PA) cephalometry,
 OPG and 3D imaging techniques, which include CBCT and non-radiation 3D
imaging of the face such as 3dMD.

Clinical evaluation
 By placing a wooden tongue blade or ice cream stick across both sides of first
molars/premolars, while a patient is seated upright, his face at eye levels of the
operator, the left to right inclination of the spatula is evaluated in relation to an
imaginary line connecting the pupils.
 The detailed extra oral examination is followed by an intraoral examination to
record asymmetry in an overbite, arch form, and levels of buccal occlusion.

A severe case of cant of occlusion plane
in an operated case of unilateral cleft lip
and palate.
(A) Clinical evaluation of cant of occlusal
plane. A wooden spatula/or a
steel ruler is held between the teeth (L–
R) and its inclination can be visualised in
relation to a horizontal reference plane. A
horizontal reference plane is constructed
by connecting right and left supraorbital
arches or inter-pupillary line.
(B) Evaluation of cant of the occlusal
plane on a frontal facial photograph taken
during a smile.

Photographs of smile
 Photographs are the most traditional resources to study smile aesthetics, which
are important keys to diagnose asymmetries in the occlusal plane.
 First, a photograph of a spontaneous smile must be captured to show the
maximum elevation of the upper lip.
 The photograph of the smile during occlusion is a part of the regular
orthodontic documentation and may be used to identify any deviation in the
upper arch

Software
 Currently, with the aid of computers and software, such as PowerPoint or
Keynote, the analysis of smiles can be facilitated by the use of reference
 One of these lines is the bipupilar line, which may be transferred from the
original position to the commissures region, to the gingival contour or tip of the
cusp of one canine, or even the incisal edge of one incisor, depending on the
necessity

Figure 1 - Bipupilar line
transferred to the
commissures region (A)
and to the cuspid tip of
tooth #23 (B), to verify the
occlusal plane canting
in both the posterior and
anterior regions.

Possibilities of drawing
reference lines,
using software such as
Keynote or PowerPoint,
to verify the symmetry of the
upper occlusal plane in
relation to the lower lip (A)
and in relation to the lip
architecture (B) in occlusion.
Reference lines to verify the
symmetry of the upper and
lower occlusal planes in
relation to the lower lip (C)
and in relation to the lip
architecture (D) with open
mouth

Radiological evaluation
A detailed clinical and radiological evaluation of the TMJ is essential in such a patient
(A) The right side condyle is long and
thin. (B) PA cephalogram is showing
mandibular deviation towards the left.
(C) Technicium scan shows a hot spot in
the right condyle suggestive of active
growth and possibility of further
growth and thereby worsening of the
facial asymmetry with age.

Reference planes
1. A true horizontal represented by a tangent to the normal supraorbital rims
2. A vertical line is drawn through the crista galli and upper third of the nasal septum
representing mid-sagittal reference plane

(A) The magnitude of occlusal cant by measuring
the degree of canting relative to the true
horizontal. The reference lines for determining
the cant are as follows: a true horizontal
represented by a tangent to the normal
supraorbital rims (1) and a vertical line drawn
through the crista galli and upper third of the
nasal septum (2). The degree of cant is
determined with respect to the true horizontal.
On this PA cephalogram, the degree of canting
of the occlusal plane was 6°. (B) The magnitude
of occlusal cant can be measured by evaluating
the medial canthus-canine distance. In the
patient above, the medial canthus to right
canine distance was 62 mm; the distance to the
left canine was 56 mm, for a total vertical
discrepancy of 6 mm. Source:Susarla SM,
Dodson TB, Kaban LB. Measurement and
interpretation of a maxillary occlusal cant in the
frontal plane. J Oral Maxillofac Surg 008
Dec;66(12):2498–502. Reproduced with
permission.

Three-dimensional computed tomography (CT) can provide
information for use in diagnosis and treatment planning.
Because of the complex 3D nature of facial asymmetry, CT scan
can be recommended in the evaluation of asymmetry cases that
cannot be assessed using conventional methods. CBCT could
be a preferred mode of diagnosis over MDCT owing to lower
radiation doses.
Cant of occlusal plane as viewed on
CBCT volumetric image.
The cant is caused by roll malrotation of
the maxilla.

Management of occlusal cant
Growing patients with mild cant
 In young patients, asymmetry of the occlusal plane caused by infraocclusion of
dental units in a buccal segment on one side can be treated using the fixed bite
plate.
The correction of altered occlusal plane requires a complex biomechanics in all
the four buccal quadrants.
 While on one side maxillary buccal segment requires intrusion of maxillary
segment and extrusion of the mandibular segment on other side reverse
movements are required to correct the transverse tilt of the occlusal plane

The correction of altered occlusal plane

Selective intrusion/extrusion of anterior
segment
 van Steenbergen and Nanda suggested the use of vertical inter-arch elastics to
extrude the buccal segment on the side of the occlusal plane that is farthest
from the treatment occlusal plane.
 The inter-arch multiple vertical elastics exert reciprocal extrusive forces on
maxillary and mandibular arches. This option works best when both upper and
lower occlusal planes are equally diverging, and the treatment plan calls for
extrusion.
 in the majority of the patients, the problem is limited to either the upper or the
lower arch, or isolated to anterior or posterior segments

Selective intrusion/extrusion of anterior
segment
 Asymmetrical intrusion of incisors
I. The selective intrusion of the anterior segment.
II. The selective extrusion of the anterior segment

Correction of cant with intrusion arch by selective
ligation of affected teeth.
(1) Intrusion arch with selective ligation of extruded teeth to level cant
of occlusal plane in the anterior segment. (A) TMA intrusion arch 0.017
× 0.025 in. comes from a molar auxiliary tube and is tied to one side of
the anterior segment (0.018 × 0.025-in. stainless steel) delivering
intrusive force on that side. (B) Activated intrusion arch, before ligation
on anterior segment. (C) Intrusion arch tied on one side only. (2) An
intrusion of the canine can be taken up separately. (A) Anterior view of
separate canine intrusion. 0.018 × 0.025-in. stainless steel arch wire
bypasses canine. A 0.017 × 0.025-in. TMA cantilever comes from the
molar auxiliary tube and is tied underneath canine bracket (point force
contact) delivering intrusive force. (B) Buccal view of separate canine
intrusion. Ideally, the wire should not be tied into bracket slot to deliver
force without moments. (C) Buccal view of separate canine intrusion.
(3) Extrusion arch with selective ligation to intrude teeth to level the
cant of occlusal plane in the anterior segment. (A) Diagrammatic
representation of unilateral extrusion of the canted anterior segment.
0.017 Å–0.025-in. TMA cantilever coming from an auxiliary tube of
molar is tied to one side of the anterior segment. (B) Patient with a
canted maxillary occlusal plane. (C) Correction of the canted occlusal
plane with cantilever hook tied on the affected side. Source:
Reproduced with permission from: van Steenbergen E, Nanda R.
Biomechanics of orthodontic correction of dental asymmetries. Am J
Orthod Dentofacial Orthop 1995;107(6):618–24.

Occlusal cant management supported by
TAD
 Temporary anchorages devices can be optimally utilised to support orthodontic biomechanics
for the purpose of selectively intrusion of the maxillary segment on one side and mandibular
teeth on another side thereby allowing the cant to be corrected
TAD supported biomechanics employed for
selective intrusion of anterior segment.
Source: Polat-Özsoy Ö, Arman-Özçırpıcı A,
Veziroğlu F, Çetinşahin A. Comparison of the
intrusive effects of miniscrews and utility
arches. Am J Orthod Dentofacial Orthop 2011
Apr;139(4):526–32. PubMed PMID:
21457864.

TAD
 In general, TAD supported mechanics can decrease or increase the vertical
height of nearby alveolar bone, with a maximum of 3 mm impaction potential,
and 1–2 mm possible extrusion.
Alveolar dental impaction leads to counter clockwise rotation of 3°. Xun. et al
reported intrusion of the maxillary and mandibular molars of 1.8 and 1.2 mm,
respectively, and a 2.3° counter clockwise mandibular rotation.

TAD
 Mechanics of selective intrusion and extrusion of the buccal alveolar segments
involves use of the TAD supported anchorage usually in two stages.
 The maxillary TADs are used for intrusion and mandibular TAD are used for
intrusion of lower buccal teeth on contralateral side. In the second stage, these
TADS can be used to level the arch by extrusion of the teeth from opposite
arches.
 In the maxilla intrusion mechanics can be applied simultaneously from two
sides, that is palatal and buccal and in the mandible, the only options are buccal
sites.

Controlling the side effects
Scheme of control of the side effects during the mechanics to
correct a canted occlusal plane with skeletal anchorage: A)
Torque control in the archwire during the intrusion on the left side
of the upper arch, B) auxiliary torque control through the
transpalatal bar (TPB).

CASE 1
Diagnosis and treatment plan
This case presents the sequence of an unsuccessful orthodontic treatment conducted for 3
years. A 29-year old woman has been treated to correct a Class II, subdivision left malocclusion,
with accentuated midline deviation, using unilateral intermaxillary elastics. The side
effects of the long period using the elastics were occlusal plane canting, mainly in the region of
canine and adjacent teeth, which can be identified in the frontal smile photograph. The upper
midline was deviated 4 mm to the right, with slight inclination of the anterior teeth to the right,
while the lower midline was correct. Similarly, the patient presented an accentuated gummy
smile, with 6-mm of gingival display on the upper central incisors region. Intraoral analysis
showed a Class II malocclusion on the left side, accentuated deviation between the midlines,
and a 4-mm overjet, whereas the lower anterior teeth were rotated. The chief complaint of the
patient was the gummy smile and occlusal plane canting, which according to her was non-
existent before the first treatment

Photographs of
treatment progress:
A, B) beginning of the
mechanics with
miniplates with 400g of
force in the left side,
with an upward
direction; and 150g in
the right side,
without vertical
component; C, D) two
months of mechanics
and application of 200g
of intrusive force in
tooth #26 region

E, F) end of Class II and occlusal plane canting correction
on the left side, stabilization with two elastics
with intrusive and retraction force, and beginning of the
use of intermaxillary elastics for extrusion of the lower
arch.

Final photographs after periodontal surgery and restorations

CASE 2
Diagnosis and treatment plan
A 32-year-old woman sought for orthodontic treatment, complaining about the crowding on the
anterior region of the mandibular arch. The smile analysis revealed an occlusal plane canting,
with more gingiva displayed on the left side. Intraoral analysis showed: Class I molar
relationship, slight Class III canine relationship, correct upper midline (measured in the papilla),
and lower midline deviated 2 mm to the right. The lower arch discrepancy was -7 mm, and
the upper arch discrepancy totaled -2 mm. Analysis of Bolton discrepancy revealed a 2-mm
excess on the anterior region of the lower arch

Photographs of treatment progress:
A, B) beginning of upper arch intrusion and
C, D) stabilization of the upper arch in the miniimplant and
extrusion of the lower arch with intermaxillary elastics.

REFERENCES
1. Om P. Kharbanda , 3rd edition Orthodontics: Diagnosis and Management of Malocclusion
and Dentofacial Deformities
2. Dental Press J Orthod. 2019 Jan-Feb;24(1):88-105
3. William profit edition 6

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