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
