Transcript Document

AETIOLOGY AND
CLASSIFICATION OF
MALOCCLUSION
Rav Govender
BChD; MFDS RCS Edin.; MSc. Lond.; MORTH RCS Eng.
Learning objectives
• CLASSIFICATION
• AETIOLOGY
Skeletal Factors
Soft Tissue Factors, often not recognised
Dental factors
Habits
Iatrogenic Factors / local
Case Discussions
AETIOLOGY
Complex multifactorial
Genetically determined, both local and skeletal
factors
eg. class III, a skeletal factor and hypodontia a
local factor are both genetically determined.
Specific genetic syndromes, Pierre Robin or acromegaly
Environmental factors / Trauma, Local
Complex interactions among multiple factors
that influence growth and development.
CLASSIFICATION
• Dental
• Skeletal
Dental
• British standards institute OR BSI
• Angle’s classification
• Andrews classification
The British standards institute is based on the incisor
relationship.
Angle’s and Andrews classification is based on the molars
relationship.
BSI
The overjet should be 2-4mm with a vertical overlap
of one third of the crown of the lower incisors.
Classification by molar relationship
Andrew
Angle
A. The distal surface of the upper first molar occludes with
the mesiobuccal cusp of the lower second permanent
molar ANDREW
B. The mesiobuccal cusp of the upper first permanent molar
occludes with t he buccal groove of the lower first
permanent molar. ANGLE
C. Half class II
D. Full unit class II
Canine classification
CLASS I
Class II
CLASSIFICATION
SKELETAL: Antero-posterior
vertical
Transverse
Mild moderate and severe
In 3 planes
SKELETAL I PATTERN
ORTHOGNATHIC/
STRAIGHT PROFILE
Angle ANB 2° - 4°
SKELETAL II PATTERN
CONCAVE
PROFILE
ANB EXCEEDS 4°
SKELETAL II
Usually due to mandibular retrognathia.
Ceph. Study By Mc Namara et. al.
Class II is not a single entity,
But mandibular skeletal retrusion most
common.
Small % is maxillary protrusion
Almost half the sample had excessive vertical
dimension.
CLASS II INCISOR RELATIONSHIP
These diagrams show how partial
reduction of the overjet does not allow
the lip to cover the upper incisors.
The upper incisors will return to their
pre-treatment position.
SKELETAL III PATTERN
CONVEX PROFILE
ANB LESS THAN 2°
SKELETAL III
Caused by maxillary deficiency and /or
mandibular prognathism.
Definitive familial and racial tendency for
mandibular prognathism.
Maxillary deficiency not clear, but
environmental factors unlikely.
Hapsburg jaws. Royal Family in Spain that
ruled around 1660
Hapsburg Jaws
• Class I the mandible is 2 -3 mm posterior to the maxilla
• Class II the mandible is retrusive relative to the maxilla
• Class III the mandible is protrusive relative to the maxilla
CLASSIFICATION
Vertical assessment, Inherited
Assessment of lower facial height. The distance x from a
point between the eyebrows to the base of the nose is
equivalent to the distance y from the base of the nose to the
chin.
CLASSIFICATION
Vertical assessment
CLASSIFICATION
Vertical skeletal assessment
Frontal view, assess the vertical and transverse
discrepancy.
Vertical assessment
Factors that influence and increase the
vertical dimension.
Increased vertical dimension: AOB
Thumb sucking habit
Partial nasal obstruction. Harvold study,
Lopatiene et.al Lithuanian study. ( 7- 15 Yr s).
The main characteristics of the respiratory
obstruction syndrome
hypertrophied tonsils or adenoids,
mouth breathing,
open-bite, cross-bite,
excessive anterior face height,
incompetent lip posture,
increased upper incisor show
narrow external nares,
"V" shaped maxillary arch
Vertical assessment
Long face syndrome
Vertical growth pattern
Increased LAFH
Downward rotation of the mandible
(clockwise rotation)
Excessive eruption of molars leading to AOB
CLASSIFICATION
Vertical assessment
Anterior open bites are often associated
with an increase in lower anterior face
height
CLASSIFICATION
Vertical assessment
Profile of a patient with a much
reduced lower anterior facial height.
Compare with long face syndrome
Low angle patient /short face
syndrome
Horizontal growth pattern
Increased overbite
Decreased LAFH
Upward and forward rotation of the
mandible, i.e. anticlockwise rotation of the
mandible.
Increased eruption of the mandibular
teeth, i.e. incisors
Both forward and backward growth
rotations results in LLS crowding, right
until the late thirties. (Bolton Brush Study
by Holly Broadbent, 1966)
CLASSIFICATION
Vertical Assessment
The reduced lower anterior face height is
often associated with a deep bite as shown
TRANSVERSE ASSESSMENT
The face is divided into fifths.
Middle fifth
Medial two fifths
Outer two fifths
Assess from above and behind the patient.
(assess facial centre, i.e. mid eye-brow, tip of
nose, philtrum of upper lip and chin point should
line up
Transverse discrepancy
True facial asymmetry
Apparent facial asymmetry, associated with
crossbite and mandibular displacement.
Intra-orally check for
-crossbite and mandibular deviation
-scissor bite and “
“
Compare mand-maxillary arches for shape
and size.
Clinically
Dental centre-lines
Check for a cant in the maxillary occlusal
plane. ( the patient bites on a tongue spatula
and relate to inter-pupillary line).
Transverse discrepancy
Asymmetric condylar growth.
Deviation of the lower dental midline to the
left.
Asymmetries are more common in class II and
class III malocclusions.
Intra orally
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
Lips
Tongue
Fraenum
Labio-mental fold
Nasiolabial angle
LIPS
Lip competency
Lip length
Lip tonicity (muscular, or flaccid and everted)
Degree of protrusion or retrusion,
All these factors are related.
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
LIPS
Lip competency,
Competent lips can be considered normal and
desirable, because
• Aesthetics: incompetent lips in conjunction with a
short upper lip can lead to the appearance of the
patient showing too much upper incisor tooth and
gingival tissue on smiling. (Gummy smile)
• Function: It provides the patient wit lip-to-lip
anterior oral seal during swallowing.
• Health: helps prevent gingival drying which can be
associated with gingival hyperplasia and gingivitis.
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
LIPS
Class II Division I
Proclined upper incisors
Lip trap
STABILITY the upper incisors should be under
the control of the lower lip.
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
LIPS
Lip incompetence, lips separated at
rest by more than 3 – 4 mm.
Increased incisal show at rest
Protrusion of the upper incisors
Lip trap, the lower lip rests behind the upper
incisors.
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
Lips
Incompetent
Flaccid and everted
Stability
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
Incompetent
Lip length
Flaccid and everted,
Gingival show
Bimaxillary protrusion
Stability
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLGY OF MALOCCLUSION
LIPS
Thin Strappy lips
Class II Division II
THE ROLE OF THE SOFT TISSUES,
IN THE AETIOLOGY OF MALOCCLUSION
Tongue thrust:
usually adaptive. The tongue is placed
between the teeth to achieve an anterior oral
seal.
Endogenous tongue thrust:
Rare,
On swallowing the tongue is pushed between
the upper and lower incisors. Associated with
sigmatism (lisping). May also be associated
with bimaxillary proclination.
An adaptive tongue thrust will cease when a
lip to lip contact can be achieved after
treatment.
Tongue Size: Macroglossia
Large Tongue
Tongue interposed between the
upper and lower incisors.
AOB OF 7MM
Large tongue
LABIOMENTAL FOLD
Indicative of
Deep bite
Reduced lower face height Low mandibular angle
THE INFLUENCE OF THE NASIO-LABIAL
FOLD
Retraction of the upper lip is contra-indicated
In adults consider orthognathic inetervention.
LOCAL FACTORS IN MALOCCLUSION
DEFN: local factors affect one or more
adjacent /opposing teeth to produce local
disturbances in in dental development.
The longer they act more severe the disturbance.
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Variations in tooth number
Abnormalities in tooth position
Labial fraenum
Trauma
Crossbites
Dento-alveolar disproportion.
Variation in tooth Number
Hypodontia, most common upper lateral
incisors, lower incisors and lower second
premolars.
Supernumery teeth
Supplemental , dichotomy of tooth germ. Incisor,
premolar (extract the most displaced tooth)
Early conical forming: offshoot of the dental
lamina. Develop between upper centrals. Single
but more common multiple. Erupts unless
inverted.
Causes median diastema. Remove if
orthodontics is planned.
Late tuberculate forming: thought to represent
a third dentition. Develops palatal to 1 / 1,
single or multiple
Prevents eruption of the incisors
Midline Supernumary
Odontome
Complex:
Mix of enamel dentine and cementum
Maxillary incisor region
Prevents eruption of the incisors
Surgical removal and bond an eruption
appliance to align the unerupted incisors.
Compound odontome:
Radiopaque mass of tissue, occurs in the
mandible or posterior maxilla.
The role of premature loss of
primary teeth
The factors that determine the outcome:
The tooth lost
Age of patient
Dentoalveolar disproportion, crowding vs
spacing.
Degree of intercuspation
High angle v low angle
Management of early loss
•Compensatory extractions- to maintain interarch relations.
•Balancing extractions- to maintain centreline.
•Space maintainers,
Advantages and disadvantages.
Prolonged retention of primary
teeth /ankylosis
•Tooth fails to maintain its position in the
developing occlusion.
More common in the mandible > Ds and Es.
Due to,
Absence of a successor
Genetic,
Trauma
Pathogenesis:
Ankylosis occurs during the reparative phase
of tooth resorption, the tooth fails to erupt
and the alveolus continues to grow in some
cases enveloping the tooth.
Effects of prolonged retention
primary teeth / ankylosis
•Progressive infraocclusion of the primary
molar, difficult extraction and lack of alveolar
height development.
•The permanent successor if present results
in delayed eruption, impaction disturbed
root formation/ cystic change
•Tipping and over-eruption of adjacent and
opposing teeth and crowding.
Management of infraocclusion
Factors to consider before treatment,
•Presence or absence of permanent successor
•Degree of infraocclusion
•Is there a co-existing malocclusion
•Long term prognosis of the primary molar
Treatment options
•Decision based on the above factors
Interceptive extraction (absent 5) –
spontaneous space closure
If there is a malocclusion then orthodontic
space closure.
Surgical subluxation, break the ankylosis
Restorative approach re-establish occlusion
18 15 14 24 25 28
48 45
35 38
Infra-occluding Es are difficult to extract , with
minimal damage to alveolus.
Abnormalities in tooth form
•Fusion, the tooth retains separate pulp
chambers.
•Gemination, common pulp chamber,
•Dilaceration, angulation between the crown
and root.
Requires a joint orthodontic restorative
and surgical approach.
Dilaceration
Dilaceration
Abnormalities in tooth position
Most common Maxillary cuspid
Genetic
Local and environmental factors
Important clinical signs, POSITION AND FORM
OF 2 / 2
Guidance theory, (peck and peck)
Transposition
Interchange in position of two permanent
teeth, one of which is almost always a canine.
Mx: canine and premolar
Md: canine and lateral incisor
Incomplete, crown overlap only
Complete, both crown and apex overley
Genetic and environmental
Migration during normal eruption
Local pathology.
Treatment options:
Orthodontic alignment of incomplete
transposition.
Orthodontic alignment in the transposed
position
Transposition
Labial fraenum and the midline
diastema
70% cases with a midline diastema associated with
a large fleshy fraenum attached to the incisive
papilla.
Diagnosis:
blanching of the incisive papilla on gentle lip
retraction.
Orthodontic space closure in the absence of
fraenectomy has a 84% relapse.
Collagenous fibres of a large fraenum disrupt the
normal transeptal fibre system between the 1 /1
Radiographically a V shaped crestal notch between
the 1 / 1 is seen.
Treatment
Aim of fraenectomy is to promote the
transeptal fibres across the defect.
Timing:
Must be after the eruption of the 3 / 3.
Done just prior to orthodontic space closure.
The post op. scar contraction across the
defect aides stability.
If done after orthodontic space closure,
access is limited, and risk of root damage.
Crossbites
Discrepancy in arch relation, lateral or sagittal
mandibular movement as a result of cuspal
interference from CR to CO.
Aetiology:
Skeletal V dental
Soft tissue
Dentoalveolar
Habits, digit sucking
Why treat
Aesthetics
Dental, pain and wear
Periodontal loss of attachment
TMJ risk
Risk of developing of a true asymmetry if left
untreated during the developmental stage.
Treatment options
Address the problem in the primary dentition
Removable and fixed appliances
Slow expansion v rapid expansion. (RME v
quad).
Cross arch elastics.
Selective grinding of Cs
Role of dental trauma in malocclusion
Damage to permanent tooth germ from an
injury to primary tooth.
Type of injury , intrusive v avulsion
determines the damage to the successor.
Prior to crown formation < 4yrs disturbance
in enamel formation resulting in coronal
defect.
Later injuries will displace the crown relative
to the root resulting in dilaceration and
impaction of the permanent successor.
Treatment will require SE and bonding an
eruption appliance.
Drift of permanent teeth ffg. early loss of
primary teeth.
Direct injury of permanent incisor =
Avulsion
Intrusive injury = Ankylosis
Discussion
Problems,
Mobile 41,
Gingival recession of 41
Deep bite
If not corrected 41 will have a poor long term
prognosis.
Appliance design
To correct anterior crossbite
Problems: severe skeletal III
Maxillary hypoplasia
peri-nasal flattening
thin soft tissues does not camourflage the
underlying skeletal III discrepancy.
Problems: increased vertical dimension
7mm AOB cuspid to cuspid
ms crowded arches
bimaxillary proclination
24 crossbite
poor rct on 46, guarded prognosis
Steep mandibular plane angle
Proclination
Lip incompetence
Increased vertical proportions
AOB.
Adverse swallowing pattern
46 rct
Aims of treatment
Address the crowding
Correct the crossbite
Establish an overbite
Level and align the arches.
Extraction:
4 4
6 5
Palatal tads to intrude upper buccal segments.
Near end treatment
Thank you
[email protected]
WWW.ORTHODONTICSCENTRE.CO.ZA
Questions
1. Ankylosis of a primary tooth can result in
(a) in its infra-occlusion. T / F
(b) delayed root formation in the permanent
successor.
T/F
(c) cystic change in the permanent successor.
(d) None of the above. T /F
2. A dilacerated tooth,
(a) has genetic aetiology,
(b) environmental aetiology
(C) None of the above
(b) both of the above
T/F
T /F
T/F
T/F
3. A large tongue interposed between the upper
and lower incisors.
(a) causes an anterior openbite. T / F
(b) associated with short face syndrome. T / F
(c ) proclination of the incisors. T / F
(d) none of the above.
T/F
Questions
Deep overbite can be associated with,
(a) reduced lower anterior face height. T / F
(b) palatal trauma. T / F
(c) Stripping of the lower labial gingivae. T / F
(d) All of the above. T /F
A severe skeletal III discrepancy,
(a) has reverse overjet. T / F
(b) Dental compensation for the underlying
skeletal III base.
T/F
(c) Best addressed with joint orthodontic /
orthognathic intervention. T / F
(d) All of the above. T / F