Aetiology of Malocclusion Flashcards
What is considered a relevant feature to indicate the possibility of an unerupted ectopic canine
Mobility of the deciduous canine
palpable palatal elevation of the alveolar mucosa
Discolouration of the deciduous canine
Inclination/Angulation of the upper lateral incisor
What would early loss of a primary tooth cause
Crowding and dental centreline shift
what are the recognised effects of a digit-sucking habit on the developing dentition
Retroclination of the lower incisors
Proclination of the upper incisors
Anterior open bite
Unilateral posterior cross-bite
What supernumerary teeth are the most likely to erupt into the oral cavity
Supplemental and conical
what are the main factors that influence any decisions that need to be made regarding whether or not to balance or compensate the extraction of a grossly carious 6
Age of patient, degree of crowding, malocclusion type
lass II skeletal jaw relationship is most commonly associated with what
A retrognathic mandible
What is is most commonly associated with a Class III jaw relationship
Anteroposterior maxillary deficiency
Not as common but also Mandibular prognathism
What would be the signs of long face syndome
Backward growth rotation of the mandible.
Increased maxillary posterior dentoalveolar height.
An increased lower anterior face height percentage.
Ante-gonial notching of the mandible
What is the likely cause of a left-sided unilateral posterior crossbite that is not associated with a lateral displacement of the mandible on closure
A true asymmetry of the mandible with the chin point shifted to the left
What is the correct term used to describe a mismatch between the size of a patient’s teeth and jaws
Dento-alveolar disproportion
What are the geneeral aetiological factors of malocclusion
Skeletal: Size, shape and relative positions of the upper and lower jaws
Muscular: Form and function of the muscles that surround the teeth i.e. lips, cheeks and tongue
Dentoalveolar: Size of the teeth in relation to the size of the jaws
What are the components of the facial skeleton
Maxillary base
Mandibular base
Maxillary and mandibular alveolar processes
The maxillary complex is attached to the anterior cranial base while the mandible articulates with the posterior cranial base
What creates malocclusion
disharmony
between the components of the facial
skeleton
What is the aetiology of skeletal variation
Genetic and environmental factors
Possible environmental factors (Masticatory muscles, Mouth breathing, Head posture)
What are the 3 skeletal variations
- Antero-posterior
- Vertical
- Transverse
What are the Cephalometrics of class 1
SNA (relates maxilla to anterior cranial base)
- ave value 81 +/-3
SNB (relates mandible to anterior cranial base)
- ave value 78 +/-3
ANB(relates mandible to maxilla)
- ave value 3 +/-2
What is a class 2 skeletal base
Mandible placed posteriorly relative to maxilla.
Mandible too small (most commonly), maxilla too
large, or combination of both
Mandible normally sized but placed too far back
due to obtuse cranial base angle
What are the cephalometrics of class 2
SNA usually average but may be increased if maxilla prognathic
SNB usually decreased
ANB >5
What is skeletal class 3
Mandible placed anteriorly relative to maxilla
Maxilla too small (most commonly), mandible too large, or combination of both
Normally sized jaws but mandible positioned too far forwards due to acute cranial base angle
what are the cephalometrics of class 3
Expect SNA to be decreased if maxilla deficient.
SNB often average but may be increased if mandible prognathic.
ANB < 1° or negative
what may disguise underlying skeletal discrepancy
Dento-alveolar structures
When talking about the vertical jaw relationship what do you need to look at
Frankfurt plane
– Lower orbital rim to superior border of external auditory meatus.
Mandibular plane
– Lower border of mandible.
Planes normally meet at the external occipital protuberance
Upper anterior face height
– Brow ridge (glabella) to base of nose
Lower anterior face height
– Base of nose (sub nasale) to inferior aspect of
chin
What is the average ration of lower anterior face height to upper anterior face height
50%/50%
What does the frankfort plane and mandibular plane create
The frankfort mandibular plane angle (FMPA)
Frankfort plane is created by joining what together
orbitale to porion
Mandibular plane is created by joining what together
Menton to Gonion
What is the average value of the FMPA
27° +/- 4°
For a long facial type what are the values associated with its vertical jaw relationship
LAFH to UAFH >55%
(more LAFH)
FMPA > 31°
Steeply inclined mandibular plane
Backward mandibular growth rotation
Anterior open bite tendency
For a short facial type whatare the values associated with ts vertical jaw relationship
LAFH to UAFH <55%
FMPA < 23°
Tendency to parallelism of jaws
Forward mandibular growth rotation
Deep overbite tendency
What are arch width discrepancies and what do they cause
Disproportion of maxillary and mandibular dental arches
Causes unilateral or bilateral buccal segment cross-bites
Often exaggerated by antero-posterior
discrepancies
What happens in mandibular displacement and what would it cause
Occurs where inter-arch width discrepancy
causes upper and lower posterior teeth to
meet cusp to cusp.
Mandible forced to deviate to one side to achieve position of inter-cuspation
Possible association with Temperomandibular joint disorders
What causes facial asymmetries
Displacement of normal mandible due to unilateral cross-bite
What causes true mandibular asymmetry
Hemi-mandibular hyperplasia/elongation
Condylar hyperlasia
What causes Dento-alveolar disproportion
Discrepancy between size of teeth and jaws
What causes crowding and spacing
Crowding caused by:
– Small jaws, normally sized teeth
– Large teeth (macrodontia)
Spacing caused by:
– Large jaws, normally sized teeth
– Small teeth (microdontia)
What is the prevalence of malocclusion
68%
What is the definition of Local Causes Of Malocclusion
a localised problem or abnormality within either arch, usually confined to one, two or several teethproducing a malocclusion
What are the local causes of malocclusion
Variation in tooth number
Variation in tooth size or form
Abnormalities of tooth
position
Local abnormalities of soft tissues
Local pathology
What could the cause of varation in tooth number be
- Supernumerary teeth (extra)
- Hypodontia (developmentally absent teeth)
- Retained primary teeth
- Early loss of primary teeth
- Unscheduled loss of permanent teeth
What is a supernumerary tooth and what are the stats of them
a tooth or tooth-like entity
which is additional to the normal series
most commonly in anterior maxilla
males > females
prevalence:
-1% in primary dentition
-2% in permanent dentition
What are the 4 types of supernumeray teeth
- Conical
- Tuberculate
- Supplemental
- Odontome
What is a conical supernumerary tooth
Small, peg shaped
Close to midline (mesiodens)
May erupt (extract)
Usually 1 or 2 in number
Tend not to prevent eruption but may displace adjacent teeth
What does mesiodens mean
A supernumerary tooth present between the central incisors
What is a tuberculate supernumerary tooth
tend not to erupt
paired
barrel-shaped
usually extracted
one of the main causes of failure of eruption of permanent upper incisors
What is a supplemental supernmerary tooth
extra teeth of normal morphology
Most often upper laterals or lower incisors
Can be third premolars, fourth molars
Often extract – decision based on form & position
what is a odontome supernumerary tooth
Compound
-discreet denticles
Complex
-disorganised mass of dentine, pulp and enamel
What is hypodontia and wha are the stats of it
developmental absence of one or more teeth
Females > males 3:2
4-6% population (excluding8’s)
Commonly upper laterals (2s) > second premolars (5s)
When would retention of primary teeth be alarming
A difference of
more than 6 months between the shedding of contra-lateral teeth
Why would a primary tooth be retained
- Absent successor
- Ectopic successor or dilacerated
- Infra-occluded (ankylosed) primary molars
- Dentally delayed in terms of development
- Pathology / supernumerary
If a patient has retained prim. teeth due to an absent successsor how would you treat it
Either maintain primary
tooth as long as possible
(if good prognosis)
Or, extract deciduous
tooth early to encourage
spontaneous space
closure in crowded cases
Wha causes early loss of primary teeth
- Trauma
- Periapical pathology
- Caries
- Resorption by successor
What affects the localisation of crowding in early loss of a primary tooth
which tooth is extracted
when the tooth is
extracted
patient’s inherent
crowding
What is meant by balancing extraction
extraction of a tooth from the opposite side of the same arch
Designed to minimise midline shif
What is meant by compensating exctraction
extraction of a tooth from the opposing arch of the same side
Designed to maintain occlusal relationship
What type of extraction would you do with each tooth in early loss of prim. teeth
incisors
-very little impact
-no compensating or balancing ext
canines
-Unilateral loss in crowded arch can give centre-line shift
-Will get some mesial drift of buccal segments
-Consider balancing extraction
Molars
-More space loss with E’s > D’s
-More space loss in upper > lower
-6’s drift mesially and steal 5 space
What factors influence the impact of the loss of 6’s
- Age at loss
upper arch less important
If L7s erupted (late)
-Often poor space closure
If too early
-Distal drift of 5’s, particularly if E’s lost at same time as 6’s
- Crowding
Uppers have potetntial for rapid space loss
- Malocclusion
What are the variations in tooth and form
- Too large - macrodontia
- Too small - microdontia
- Abnormal form
Talk about Macro/microdontia
Macrodontia
-tooth/teeth larger than average
localised or generalised
problems=crowding,asymmetry,aesthetics
Microdontia
-tooth/teeth smaller than average
-localised or generalised
-leads to spacing
-linked to hypodontia
What abnormal forms of teeth can you get
- Peg shaped laterals
- dens in dente
- geminated/fused teeth
- talon cusps
- dilaceration
- accessory cusps and ridges
What are ectopic teeth
Teeth not in the dental arch
What teeth are more commonly ectopic
third molars (8s)
upper canines (3s)
first permanent molars (6s)
upper centrals (1s)
Talk about ectopic canines
80% palatally and often in well aligned arches
Higher incidence with:
-Absent/peg shaped U laterals
-Class II, div 2 incisor relationship
Buccal canines more associated with crowding
What radiographs would you need to take to radiographically assess ectopic canines
Whattechnique would you use
usually OPT & upper anterior oblique occlusal
Parallax technique
-3 Ps= presence, position, pathology
What management options of an ectopic canine are there
- Prevention
- Extraction c to encourage improvement in position of 3
(interceptive) - Retain 3 and observe ( accept its position)
- Surgical exposure and orthodontic alignment
- (Surgical) Extraction
- Autotransplantion
What are the possible causes of ectopic central incisors
No obvious cause
Supernumerary
-Tuberculate
-Odontome
Trauma to primary predecessor
-Ankylosis of primary tooth
-Displacement of tooth germ
-Dilaceration of root
What does transposition of teeth mean and what are the classifications
Interchange in the position of two teeth
True/Pseudo
What teeth are more commonly transpositioned and what are the treatment options
upper canines & first premolar
lower canines & incisors
Treatment options:
1) accept
2) extract
3) (correct)
What can cause local abnormalities of soft tissues
- Digit sucking
- Fraenum
- Tongue thrust
What could a labial Fraenum cause
Median diastema
