4 - Local causes of malocclusion Flashcards
Define a local cause of malocclusion.
Localised problem or abnormality within either arch, usually caused by one, two or several teeth producing a malocclusion
What are categories of local causes of malocclusion?
- variation in tooth number
- variation in tooth size or morphology
- tooth position
- abnormalities of soft tissues
- local pathology
Describe different ways in which tooth number can vary.
- supernumerary teeth
- hypodontia
- retained primary teeth
- early loss of primary teeth
- unscheduled loss of permanent teeth
What are supernumerary teeth?
- tooth or tooth like structure which is additional to the normal amount of teeth
- most commonly found in anterior maxilla
- more common in males
What are the different types of supernumerary teeth?
- conical
- tuberculate
- supplemental
- odontome
Describe a conical supernumerary tooth.
- small, peg shaped
- close to midline
- may erupt
- do not prevent eruption but can displace adjacent teeth
Describe a tuberculate supernumerary tooth.
- do not erupt
- paired
- barrel shaped
- can cause permanent upper incisors to not erupt
- usually extracted
Describe a supplemental supernumerary tooth.
- extra tooth with normal morphology
- most commonly upper laterals or lower incisors (can be premolars)
- usually extracted based on treatment plan
Describe an odontome supernumerary tooth.
- two types, compound and complex
- compound are discreet denticles
- complex are a disorganised mass of dentine, pulp and enamel
- require extraction
- can prevent eruption of surrounding teeth
Define hypodontia.
Developmental absence of one or more teeth
Describe the prevalence of hypodontia.
- more common in females
- hereditary
- most commonly affects upper laterals and second premolars
When should you investigate retained primary teeth?
Difference of more than 6 months between exfoliation of contralateral teeth
What are causes of retained primary teeth?
- absent successor
- ectopic successor or dilacerated
- ankylosed primary molars (can become infraoccluded)
- delayed development
- pathology
- supernumerary
What is the management for an absent successor?
- maintain primary tooth as long as possible
- extract early to encourage spontaneous space closure
Define an infra-occluded primary molar.
- process where tooth fails to achieve or maintain occlusal relationship with opposite teeth
- tooth appears to become more submerged under gingiva
Define slight infra-occlusion.
Between occlusal surface and interproximal contact, less than 2mm
Define moderate infra-occlusion.
Within occluso-gingival margins of interproximal contact
Define severe infra-occlusion.
Below interproximal contact point
What are the causes of early loss of primary teeth?
- trauma
- periapical pathology
- caries
- resorption by successor
Define a balancing extraction.
- extraction of tooth from opposite side of side arch
- designed to minimise midline shift
Define a compensating extraction.
- extraction of tooth from opposing arch of the same side
- designed to maintain occlusal relationship
What is the management of early loss of primary incisors?
- little impact
- no compensating or balancing extraction
What is the management of early loss of primary canines?
- unilateral loss in crowded arch can cause midline shift
- consider balancing extraction
What is the management of early loss of primary molars?
- more space loss with Es than Ds
- more space loss in upper than lower (roots are mesial of crown so tilt more easily)
- 6s drift mesially and impinge on space for 5s
- no compensating extraction
At what age do you assess prognosis of 6s?
8-9 years
How does loss of 6s affect the upper arch?
Potential for rapid space loss
How does loss of 6s affect the lower arch?
- spaced dentition will be left with spaces
- aligned dentition will be left with spaces
- crowded dentition will be left more aligned if extracted early
What effect does timing have on the unscheduled loss of permanent central incisors?
- early results in drift of adjacent teeth
- late results in permanent space
How should you manage unscheduled loss of permanent central incisors?
- reimplant
- simple denture
- if lateral shift, reopen space for prothesis or build up lateral to mimic central
Define macrodontia.
- tooth is larger than average
- can be localised or generalised
- causes issues with crowding, asymmetry and aesthetics
Define microdontia.
- tooth smaller than average
- can be localised or generalised
- leads to spacing
- linked with hypodontia
- genetic link
- can be managed by composite bonding
Describe the different abnormal forms teeth can take.
- peg laterals
- dens in dente (communication to pulp from enamel)
- geminated teeth
- talon cusp
- dilaceration
- accessory cusps or ridges
What teeth are more commonly ectopic?
- 8s
- upper 3s
- 6s
- upper 1s
Where are ectopic canines typically found?
80% palatal
What circumstances are ectopic canines typically associated with?
- class 2 div 2
- small or absent upper laterals
- due to long path of eruption
What makes up the clinical assessment for ectopic canines?
- palpate for buccal canine bulge from 9 years
- inclination of laterals (distally)
- mobility of c or 2s
- colour of c or 2s
How are radiographs used to assess ectopic canines?
- 2 required, OPT and upper anterior oblique occlusal
- parallax technique (canine moves up = palatal side)
What are the management options of ectopic canines?
- prevention
- extract C to encourage 3 to erupt in correct position (interceptive)
- retain and accept position
- surgical exposure and orthodontic alignment
- surgical extraction
- autotransplantation
Describe ectopic 6s.
- uncommon
- more common in upper
- reversible before age of 8
- caries risk
What does an ectopic 6 indicate?
- crowding (common in CLP)
- mesial path of eruption
- abnormal morphology of Es
How you manage ectopic 6s?
- distalise 6s
- extract Es or allow to exfoliate
Define transposition.
Interchange in position of two teeth
What are the classes of transposition?
- true = crown and root aligned
- pseudo = crown has moved position but roots are crossed
Where are transpositions most common?
- upper 3s and 4s
- lower canines and incisors
What are the treatment options for transpositions?
- accept
- extract
- (correct)
What are the soft tissue causes of malocclusion?
- digit sucking
- tongue thrust
- frenum
- lip strap
What are the consequences of digit sucking?
- proclined upper incisors
- retroclined lower incisors
- AOB
- unilateral posterior crossbite (due to narrowed maxillary arch)
How can a labial frenum influence tooth position?
Can cause median diastema
What are the consequences of a tongue thrust?
AOB which relapses if treated
What local pathology can effect tooth position?
- caries
- cysts
- tumours
How can cysts impact tooth position?
- cause resorption of roots
- move roots
