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orthodontics 4th year > Aetiology of malocclusion, Extractions and Local factors > Flashcards

Aetiology of malocclusion, Extractions and Local factors Flashcards

1
Q

what is malocclusion?

A

> an appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory

> malocclusion is not a disease but is regarded as a deviation from the normal

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2
Q

what are the categorical causes of malocclusion and malposition?

A

> skeletal pattern (genetically determined)

> Local factors

> soft tissues (pressure from lips, muscles, tongue)

> space deficiency and excess

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3
Q

what are the general factors causing of malocclusion?

A

> SKELETAL RELATIONSHIP

> TOOTH SIZE / ARCH SIZE DISPROPORTION

> soft tissues (macroglossia)

> genetic and developmental disorders

> TMJ trauma / growth abnormalities

> general factors tend to be things you can’t control for

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4
Q

what are the local factors causing malocclusion?

A

> EARLY LOSS / PROLONGED RETENTION OF
- DECIDUOUS TEETH
- ECTOPIC TEETH

> Absent teeth, supernumeraries

> Impaction, delayed eruption

> large Fraenum, local pathology

> Dental trauma

> local factors allow us to spot problems during development

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5
Q

how does skeletal relationship cause malocclusion?

A

> mostly genetic control

> jaw size has decreased since primitive populations

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6
Q

how does tooth and arch size cause malocclusion?

A

> relatively small arches may cause crowding

> larger teeth may cause crowding
- tooth size genetically controlled
- begg and aboriginal populations - found that softer diet led to smaller teeth

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7
Q

what are the common developmental and genetic disorders which cause malocclusion?

A

> Cleft Lip and Palate
- Surgical scarring: Class III, Crossbites
- local factors - supernumeraries / absent teeth

> Achondroplasia (he most common type of short limb (or disproportionately short stature)

> Acromegaly (abnormal growth of the hands, feet, and face, caused by overproduction of growth hormone by the pituitary gland.)

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8
Q

how does soft tissues cause malocclusion?

A

> Tongue posture and size
- anterior open bite
- cerebral palsy

> Tongue thrust not an aetiological factor

> Lip form and function
- bimaxillary proclination in Afro-Carribeans

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9
Q

what local factors involving the teeth are important in discovering the cause of maloclusion?

A

> Deciduous Teeth
- Early loss or prolonged retention of deciduous teeth

> Permanent: number of teeth
- Absent teeth (hypodontia)
- supernumeraries
- early loss (6s, 1s) - caries/ trauma

> Permanent: position of teeth
- ectopic canines (2% effect)
- impaction of 1st molars, or premolars

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10
Q

what might occur if the labial frenum is thickened?

A

> can lead to a midline diastema

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11
Q

what might happen if there is early loss of the Es due to caries?

A

> 6s move medially

> 4s and 5s unable to fit in the arch

> insufficient space = results in crowding + irregularities to the arch

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12
Q

how do you avoid problems with crowding caused by early loss of deciduous teeth?

A

> space maintainers

> best for of space maintenance is retaining the deciduous tooth

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13
Q

what are the effect of early loss of deciduous teeth?

A

> Tooth lost
- D, E = space loss as 1st permanent molars drift mesially (causes premolar crowding)
- C = incisor midline shift as permanent incisors drift into space
- A, B = minimal effect

> Age
- Effects more severe with earlier loss

> Degree of Crowding in the Arch
- more space loss with D or E loss if crowding present
- greater midline shift with C loss if perm incisors crowded

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14
Q

is prolonged retention of the deciduous teeth common?

A

> relatively common

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15
Q

what teeth tend to be affected by the prolonged retention of deciduous teeth?

A

> usually Es and Ds

> may delay permanent successor erupting

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16
Q

what may happen to retentive deciduous teeth?

A

> infraocclusion - (other teeth and bone continue to develop in the vertical dimension)

> May become “submerged” or “infraoccluded” due to ankylosis (root cementum attaching directly to the bone)
- tipping of adjacent teeth (first molars)
- almost all exfoliate naturally
- extract only if becoming completely submerged

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17
Q

what is the most common scene in the permanent dentition relating to malocclusion?

A

> hypodontia (congenital)

> 2-3%

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18
Q

what is severe hypodontia?

A

> 6 or more missing teeth excluding 8s

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19
Q

what do you call the complete absence of all permanent teeth?

A

> anodontia

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20
Q

excluding 3rd molars what are the most absent teeth seen in hypodontia cases?

A

> upper laterals

> 2nd premolars

> lower central

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21
Q

what is the treatment for hypodotia?

A

> space closure

> Open or maintain space then bridgework / implants / denture

> accept (e.g. lower 5s)

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22
Q

what is the treatment for hypodotia?

A

> space closure

> Open or maintain space then bridgework / implants / denture

> accept (e.g. lower 5s)

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23
Q

how common is missing upper laterals?

A

> 2-3%

24
Q

what are missing upper lateral incisors associated with?

A

Associated with ectopic canines and small contralateral lateral incisors

25
Q

what is the treatment for missing upper laterals?

A

> space closure (crowding, Class II cases, 3s acceptable)

> bridgework (no crowding, 3s poor colour)

> usually need fixed appliances

26
Q

how common is absent second premolars?

A

> common - 2%

> can appear on radiographs as late as age 8

27
Q

what is the treatment for an absent second premolar?

A

> space closure (extract deciduous early)

> bridgework

> use space to treat crowding

> accept and retain Es

> Prognosis of Es uncertain, unusual to last beyond age 30

28
Q

are absent lower centrals common?

A

> very rare

> A’s usually retained

29
Q

what is the treatment for absent lower centrals?

A

> close space

> bridgework

30
Q

what is the incidence of supernumerary teeth?

A

> 1-2%

> 80% are in the anterior maxilla (OPG/ Anterior occlusal to find)

31
Q

what is the classification of supernumerary teeth

A

> Morphology = Coniform and Tuberculate

> Position = Mesiodens, Supplemental (looks like another tooth), Paramolar

32
Q

what are the clinical effect of supernumerary teeth?

A

> causes delayed eruption of teeth (e.g. Upper centrals)

> may erupt (mesiodens), causing crowding

> midline diastema (mesiodens)

33
Q

what is the treatment of supernumerary?

A

> No treatment

> Extract

> Exposure and alignment of teeth with delayed eruption (Upper incisors)

> However, more than 70% of unerupted upper central incisors will erupt following removal of a supernumerary tooth

34
Q

what are the common impacted teeth?

A

> first permanent molars

> premolars

> third molars

35
Q

what is the incidence of impacted permanent first molars?

A

> 3-4%

36
Q

where is the impacted 6s most commonly found?

A

> maxilla

37
Q

what is the treatment options for impacted 6s?

A

> two thirds will correct spontaneously, although unlikely to improve after age 8 years.

> extraction of E

> Simple URA to disimpact

38
Q

what causes the impaction of premolars?

A

> early loss of Es

39
Q

what is the more common impacted premolar?

A

> second premolar

40
Q

what is the treatment for impacted premolars?

A

> Extract 4 to allow eruption of 5

> Extract 7 and distalise 6 to create space

> Extract 5 (surgical)

> No treatment and review regularly

41
Q

what is the incidence of ectopic canines?

A

> 2%

42
Q

what can happen to a upper labial frenum?

A

> it can become abnormally thick

43
Q

what are abnormally thick upper labial frenums associated with?

A

> midline diastema

44
Q

what is the treatment for an abnormally thick labial frenum?

A

> wait until upper canines erupted before treating

> fraenectomy during or after space closure

45
Q

what is the common causes for early loss of permanent teeth?

A

> 6s = caries

> 1s = trauma

46
Q

why is the early loss of permanent 1st molars a problem?

A

> Residual space

> overeruption of opposing first molar

> space is difficult to use with appliances for treating anterior crowding or overjet

47
Q

what is the ideal age for spontaneous closure of early loss of permanent 1st molars?

A

> 8-9 years

48
Q

does the upper or lower spaces caused by early loss of 6s close better?

A

> upper spaces close better

49
Q

what happens to unopposed upper 6s?

A

> they over erupt

50
Q

what happens to the midline in unilateral loss of 6s?

A

> midline shift is minimal so not to worry

51
Q

what is the management of carious 1st molars?

A

> Extraction best age 8-9, if 6s are of poor prognosis at this age then consider extraction

> Later extraction –> tipping

> Consider extraction of upper with lower

52
Q

would you extract 3rd molars due to crowding ?

A

> no - very weak association with lower incisor trauma

> lower incisor crowding in 70% of patients

53
Q

what are the tx options if upper perm incisors are lost or unsaveable?

A

> Maintain space with prosthesis

> Close space orthodontically and crown lateral poor gingival margin & canine colour

> however try to save eg RCT, reimplant

54
Q

what are the biggest risk of early loss of perm upper incisors?

A

> 8-10

> trauma

> > boys

> class 2 div 1 = poor lower lip coverage (incompetent) no protection

55
Q

what are common examples of abnormal tooth forms?

A

> dilaceration of perm upper incisors

> peg shaped upper lateral incisors

56
Q

what is the dilaceration of permanent upper incisors?

A

> root bent away from the crown

> trauma to deciduous predecessor, age 4-5

> causes delayed or non-eruption

> tx - orthodontic alignment sometimes possible

> a lot less common than supernumerary - use radiograph to differentiate

57
Q

what is peg shaped upper lateral incisors often associated with?

A

> strong association with ectopic canines

> other lateral may be absent

orthodontics 4th year (12 decks)

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