Aetiology of Malocclusion Flashcards
What are the 3 types of skeletal variation?
Antero-posterior
Vertical
Transverse
In cephalometrics what does SNA relate to?
Relates maxilla to anterior cranial base
In cephalometrics what does SNB relate to?
Relates mandible to anterior cranial base
In cephalometrics, what does ANB relate to?
Relates the mandible to maxilla
What is the definition of local causes of malocclusion?
A localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion
What are some 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 can cause a variation in tooth number?
Supernumerary teeth (extra)
Hypodontia (developmentally absent teeth)
Variation of Timing
–Retained primary teeth
–Early loss of primary teeth
–Unscheduled loss of permanent teeth
What is a supernumerary tooth?
A tooth or tooth-like entitity which is additional to the normal series
What are the 4 types of supernumerary teeth?
Conical
Tuberculate
Odontome
Supplemental
What is a conical supernumerary tooth?
Small, peg shaped
Occurs close to the midline (mesiodens)
May erupt (extract if so)
Usually 1 or 2 in number
Tend not to prevent eruption but may displace adjacent teeth
What is a tuberculate supernumerary tooth?
One of the main causes of failure of eruption of permanent upper incisors
Tend not to erupt
Paired
Barrel-shaped
Usually extracted
What are supplemental supernumerary teeth?
Extra teeth of normal morphology
Most often upper laterals or lower incisors
Often extract- decision based on form and position
What is an odontome supernumerary tooth?
Compound
-discreet denticles (tooth like objects in a mass)
Complex
-disorganised mass of dentine, pulp and enamel
What is the definition of hypodontia?
Developmental absence of one or more teeth
What is counted as a Retained Primary Teeth?
A disruption in the sequence of eruption
A difference of more than 6 months between the shedding of contra-lateral teeth
Why are some primary teeth retained?
There is an absent successor
Ectopic successor or dilacerated
Infra-occluded (ankylosed) primary molars
–ankylosed primary teeth remain in a fixed position, while the adjacent teeth continue to erupt, moving occlusally
Dentally delayed
Pathology/supernumerary
What to do if there is an absent successor?
Either maintain the primary tooth as long as possible (if there is a good prognosis)
Or extract deciduous tooth early to encourage spontaneous space closure in crowded cases
What is an infra-occluded primary tooth?
Submerged
Definition
–Process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
Temporary ankylosis
What is a balancing extraction?
By extraction of a tooth from the opposite side of the same arch
Designed to minimise midline shift
What is a compensating extraction?
By extraction of a tooth from the opposing arch of the same side
Designed to maintain occlusal relationship
What factors influence the impact of the loss of 6s?
AGE AT LOSS
-upper arch: less important
-Lower arch
–If 7’s erupted late there is often poor space closure
CROWDING
-Upper arch, potential for rapid space loss
-Lower arch,
–spaced- will have spaces
–aligned- will have spaces
–crowded- best results likely
MALOCCLUSION
What causes a variation in tooth size or form?
Macrodontia- too large
Microdontia - too small
Abnormal form
What is microdontia?
Tooth/teeth smaller than average
Localised or generalised
Leads to spacing
Linked to hypodontia
What is macrodontia?
Tooth/teeth larger than average
Localised or generalised
Problems
-Crowding
-Asymmetry
-Aesthetics
What are examples of abnormal form of teeth?
Peg shaped laterals
Dens in dente
Germinated/fused teeth
Talon cusps
Dilaceration
Accessory cusps and ridges
At what age can you bucally palpate canines from?
Why do this?
9 years onwards
Check for ectopic maxillary canines
What incisor relationship are ectopic canines more likely in?
Class II division2 incisor relationship
What 2 radiographs are normally used to localise position of an ectopic canine?
What technique is used?
OPT and upper anterior oblique occlusal
Parallex technique
- 3 P’s, Presence, Position, Pathology
What are the management options for ectopic canines?
Extraction of C to encourage improvement in position of 3 (interceptive)
Retain 3 and observe
Surgical exposure and orthodontic realignment
Surgical extraction
Autotransplantion
What is the prevention for ectopic canines?
Appropriate monitoring from age 9 onwards
Clinical assessment
Symmetry
What are ectopic first molars a sign of?
Crowding
Mesial path of eruption
Abnormal morphology of E
What is the management of ectopic 6’s?
Attempt to distalise 6’s
Extract E
Separator
What is a transposition?
Definition
Interchange in the position of two teeth
What are the treatment options for a transpositioned tooth?
Accept
Extract
Correct
What can a labial fraenum cause?
A median diastema
How does mandibular displacement occur?
Occurs where inter-arch width discrepancy causes upper and lower posterior teeth to meet cusp to cusp
Mandible is then forced to deviate to one side to achieve a position of inter-cuspation
Means mandible displaces from midline to achieve occlusion
What is a dental cause of facial asymmetries?
Displacement of normal mandible due to unilateral cross-bite
What is hemi-mandibular hyperplasia?
Asymmetry, increase in ramus height, rotated facial appearance and prominence of the lower border of the mandible
What is hemi-mandibular elongation?
Horizontal displacement of the mandible and chin on affected side
What is condylar hyperplasia?
Over enlargement of the mandible
What is dento-alveolar disproportion?
Discrepancy between size of teeth and jaws
What can crowding be caused by in dento-alveolar disproportion?
Small jaws, normally sized teeth
Large teeth (macrodontia)
What can spacing be caused by in dento-alveolar disproportion?
Large jaws, normally sized teeth
Small teeth (microdontia)
How do you assess anteroposterior relationship
Extra-oral?
Intra-oral?
Extra oral
-Maxilla to mandible relation
Intra-oral
-incisor classification
-overjet
-canine relationship
-molar relationship
-anterior crossbite
How do you assess vertical relationship
Extra-oral?
Intra-oral?
Extra-oral
-in facial thirds
-angle of lower border of mandible to maxilla
Intra-oral
-centrelines
-posterior crossbite
How do you assess transverse relationship
Extra-oral?
Intra-oral?
Extra-oral
-facial symmetry
Intra-oral
-overbite
-anterior open bite
What is the difference between overbite and overjet?
Overbite- Lower jaw too far behind upper jaw
Overjet- extent of horizontal overlap between maxillary central incisors and mandibular central incisors
