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BDS3: Clinical dental sciences > Orthodontics > Flashcards

Orthodontics Flashcards

1
Q

when do you do brief ortho exam?

A

9 years

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2
Q

when can an extensive ortho exam be done?

A

11- 12 – when premolars canine erupt

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3
Q

what is Ideal occlusion?

A

 Rare
 1. Molar relationship
* Distal surface of disto-buccal cusp of upper first molar occludes with mesial surface of mesio-buccal cups of lower 2nd molar
 2. Crown angulation
 3. Crown inclination
 4. No rotations
 5. No spaces
 6. Flat occlusal planes
(Andrews 6 keys)

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4
Q

what is malocclusion?

A

 Are more sig deviations from the ideal that may be considered unsatisfactory (aesthetically or functionally)
 May require tx but pt factor may influence decision

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5
Q

what must you ask about in relation to PDH for ortho exam?

A

 Ask about trauma to permanent dentition
* History of trauma
* Root resorption?
* RCT?

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6
Q

what habits are important to know of when doing ortho exam?

A
  • Thumb sucking
  • Lower lip sucking
  • Tongue thrust
  • Chewing finger nails
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7
Q

what are competent lips?

A
  • Competent – lips meet at rest
    o Relaxed mentalis M
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8
Q

what are incompetent lips?

A

o Lips that do not meet at rest
o Relaxed mentalis M

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9
Q

what is a lip trap? and what could a relapse lead to?

A
  • May procline upper incisors
  • May lead to relapse of overjet if persists at end of tx
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10
Q

what would hyper active lower lip do?

A

retrocline lower incisorS

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11
Q

What should you know about tongue when doing ortho exam?

A

 Position
 Habitual
 Swallowing

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12
Q

in terms of tongue position and swallowing pattern when doing ortho exam what should you know?

A
  • Tongue position and swallowing pattern
    o Tongue thrust on swallowing can be associated with an anterior (AOB)
    o Can be either endogenous or adaptive tongue thrust (cause or effect?)
    o May cause relapse of AOB at end of tx if endogenous
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13
Q

what are occlusal effects of a thumb habit?

A

o Proclination of upper anteriors
o Retroclination of lower anteriros
o Localise AOB or incomplete OB
o Narrow upper arch +/- unilateral posterior cross bite
o Remember that effects will be superimposed on existing skeletal pattern and incisor relationship

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14
Q

what should you know about TMJ when doing ortho exam?

A
  • Patho of closure
  • Range of movement
  • Pain, click from joint
  • Deviation on opening
  • Muscle tenderness
  • Mandibular displacement
    o Discrepancy in retruded contact position and inter cuspal position
    o RCP does not equal ICP
    o Displacement of mandible up and to the right from RCP to ICP -note center line position
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15
Q

what are the 3 planes facial skeleton is considered in?

A
  • Antero-posterior
  • Vertical
  • Transverse
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16
Q

what is a class I skeletal?

A

maxilla 2-3mm in front of mandible

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17
Q

what is a class II skeletal?

A

maxilla more than 3mm in front

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18
Q

what is a class III skeletal?

A

mandible in front of maxilla

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19
Q

how do you check skeletal bases?

A
  • Direct palpation of skeletal bases
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20
Q

how is vertical skeletal assessment done?

A

Frankfort – mandibular planes angle (FMPA)

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21
Q

how is lateral skeletal assessment done?

A

Mid sagittal ref line

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22
Q

what must you assess during IO for ortho exam?

A
  • Crowding
  • Space
  • Rotations
  • Palpate for canines if not erupted
  • Note teeth of abnormal shape/size e.g peg lateral
  • Lower arch – angulation of incisors to mandibular plane – upright, proclined, retroclined
  • Upper arch – angulation of incisors to Frankfort plane – upright, proclined, retroclined
  • Teeth in occlusion
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23
Q

what do you check when teeth in occlusion during ortho exam?

A

Max interdigitation or RCP

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24
Q

what involves with checking max interdigitation or rcp?

A

 Incisor relationship
 Overjet
 Overbite/ open bite
 Molar relationship (angle’s classification)
 Canine relationship
 Cross bites
 Centre lines

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25
Q

what is incisor relationship classes?

A

o Class I
 Lower incisor edges occlude with or lie immediately below cingulum plateau of upper central incisors
o Class II
 Lower incisor edges lie posterior to cingulum plateau of upper incsiors
 Division 1
- Upper incisors are proclined or of average inclination there is an increase in overjet
 Division 2
- Upper central incisors are retroclined. The overjet is usually minimal or may be increased
o Class II
 Lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed

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26
Q

what does molar relationship (angle’s classification) also mean?

A

buccal segment relationship

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27
Q

what is involved with buccal segment relationship?

A
  • Angles classification
    o Class I
    o Class II
    o Class III
  • Crossbites
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28
Q

what do you compare patient to parent for?

A

 Malocclusion
* Especially class 3 malocclusions
 Growth potential

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29
Q

what radiographs can you do for ortho exam?

A

 OPT
 Maxillary anterior occlusal
 Lateral cephalogram

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30
Q

what is aetiology of malocclusion?

A
  • skeletal
    -dental
  • soft tissue
  • other such as habits
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31
Q

what is definition of local cause of malocclusion?

A

localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion

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32
Q

what are some types of local causes of malocclusion?

A

 variation in tooth number
 variation in tooth size or form
 abnormalities of tooth position
 local abnormalities of soft tissues
 local pathology

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33
Q

what are types of variation in tooth number?

A
    1. Supernumerary teeth (extra)
    1. Hypodontia (developmentally absent teeth)
  • (variation of timing)
    1. Retained primary teeth
    1. Early loss of primary teeth
    1. Unscheduled loss of adult teeth
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34
Q

what is supernumerary tooth?

A

o A Tooth or tooth like entity which is additional to the normal series

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35
Q

where is a supernumerary most common?

A

 Most commonly in anterior maxilla
 Males > females

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36
Q

what are the 4 types of supernumerary?

A
    1. Conical
    1. Tuberculate
    1. Supplemental
    1. Odontoma
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37
Q

what is a conical supernumerary? where would it tend to be? what can it do?

A

o Small, peg shaped
o Close to midline (mesiodens)
o May erupt (extract)
o Usually 1 or 2
o Tend not to prevent eruption but may displace adjacent teeth

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38
Q

what does a conical supernumerary tend to do?

A

Tend not to prevent eruption but may displace adjacent teeth

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39
Q

what is a tuberculate supernumerary? what does it tend to cause? what does it tend to do and what do you tend to do?

A

o Tend not to erupt
o Paired
o Barrel-shaped
o Usually extracted
o One of the main causes of failure of eruption of permanent upper incisors

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40
Q

what is one of the main causes of failure of eruption for the permanent upper incisors?

A

tuberculate

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41
Q

what is a supplemental supernumerary? what is it most common? what do you do?

A

o Extra teeth of normal morphology
o Most often upper laterals or lower incisors
o Can be third premolars, 4th molars
o Often extract – decision based on form and position

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42
Q

what is a supplemental normally?

A

o Most often upper laterals or lower incisors
o Can be third premolars, 4th molars

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43
Q

what determines extraction of supplemental supernumerary?

A

decision based on form and position

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44
Q

what is an odontoma broken categorised as?

A

o Compound
 Discreet denticles
o Complex
 Disorganised mass of dentine, pulp and enamel

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45
Q

what is the definition of hypodontia?

A

developmental absence of more teeth

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46
Q

what is hypodontia commonly as?

A

o Females > males
o Commonly upper laterals (2s) > 2nd premolars (5s)

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47
Q

what is a retained primary tooth? when should you be worried?

A

o Disruption in sequence of eruption
o A diff of more than 6 months between the shedding of conta lateral teeth – alarm bells

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48
Q

when are you alarmed about a retained primary tooth?

A

A diff of more than 6 months between the shedding of conta lateral teeth

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49
Q

what are some reasons of retained primary teeth?

A

 1. Absent successor
 2. Ectopic successor or dilacerated
 3. Infra-occluded (ankylosed) primary molars
 4. Dentally delayed in terms of development
 5. Pathology/ supernumerary

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50
Q

what would you do in the event of an absent sucessor?

A
  • Either maintain primary tooth as long as possible (if good prognosis)
  • Or extract primary tooth early to encourage spontaneous space closure in crowded cases
  • Early ortho referral for advice
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51
Q

what is the defintion of infra-occluded (ankylosed) primary molars?

A

process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth

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52
Q

what are some reasons for early loss of primary teeth?

A

 1. Trauma
 2. Periapical pathology
 3. Caries
 4. Resorption by successor

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53
Q

what would happed if primary incisor is extracted?

A

o Very little
o No compensating or balancing ext

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54
Q

what would you need to do if primary canine is extracted?

A

o Unilteral loss in crowded arch, can givr centre-line shift
o Will get some mesial drift of buccal segments
o Consider balancing extraction

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55
Q

what would happen if primary molar is extracted?

A

o More space loss with E’s > Ds
o More space loss in upper > lower
o 6s drift mesially and steal 5 space

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56
Q

how does when a primary tooth is extracted effect?

A
  • Most effect when primary teeth extracted early
  • Little effect if done late
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57
Q

what does balancing extraction mean?

A
  • By extraction of a tooth from opposite side of same arch
  • Designed to minimise midline shift
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58
Q

what does balancing extraction designed to do?

A

minimise midline shift

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59
Q

what does compensating extraction mean?

A
  • By extraction of a tooth from the
    o Opposing arch of same side
  • Designed to maintain occlusal relationship
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60
Q

what does compensating extraction designed to do?

A

maintain occlusal relationship

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61
Q

what is ideal choice for relief of crowding?

A

6s
* Planned loss early is better than enforced older

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62
Q

what are some factors that influence impact of loss of 6s?

A
    1. Age at loss
    1. Crowding
    1. Malocclusion
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63
Q

what is has more impact in loss of 6? upper or lower arch?

A

lower arch

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64
Q

what happens if lower 7s erupted late when 6 is lost?

A
  • Often poor space closure
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65
Q

what happens if 6 is lost too early in lower arch? and when in particular?

A
  • Distal drift of 5s, particularly is Es lost at same time as 6s
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66
Q

what is there the potential of when 6s are lost in upper arch in regards to crowding?

A

Potential for rapid space loss

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67
Q

what is there the potential of when 6s are lost in lower arch in regards to crowding?

A

 Spaced -> will have spaces
 Aligned -> will have spaces
 Crowded -> best results likely

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68
Q

what does early unscheduled loss of central incisor result in?

A

result drift of adjacent teeth

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69
Q

what does late unscheduled loss of central incisor result in?

A

result long term space

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70
Q

what do you ideally do in instance of unscheduled loss of central incisor?

A

maintain space
- implant
- simple denture

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71
Q

what to do if lateral incisor drifts to fill space?

A
  • Re-open space for prosthesis
  • Build up lateral
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72
Q

what are types of variation in tooth size or form?

A
    1. Too large – macrodontia
    1. Too small – microdontia
    1. Abnormal form
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73
Q

what does macrodontia mean?

A

 Tooth/teeth larger than average
 Localised or generalsied

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74
Q

what are problems from macrodontia?

A
  • Crowding
  • Asymmetry
  • aesthetics
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75
Q

what does microdontia mean? what does it link to and lead to?

A

 Tooth/teeth smaller than average
 Localised or generalised
 Leads to spacing
 Linked to hypodontia

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76
Q

what are some types of abnormal tooth forms?

A

o 1. Peg shaped laterals
o 2. Dens in dente
o 3. Geminated/fused teeth
o 4. Talon cusps
o 5. Dilaceration
o 6. Accessory cusps and ridges

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77
Q

what are some types of abnormalities of tooth position?

A
  • ectopic teeth
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78
Q

what are ectopic teeth?

A

teeth that develop in abnormal locations in mouth

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79
Q

what are the most common teeth to be ectopic?

A

 8’s
 3’s
 6’s
 1’s

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80
Q

what do you check for upper 3?

A

Check for palpable buccal canine bulge from 9 years onwards

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81
Q

where do ectopic palatal 3s normal occur?

A

well aligned arches

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82
Q

when is there a higher incidence of ectopic 3s?

A

o Absent/peg shaped U laterals
o Class II, div 2 incisor relationship

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83
Q

what do you do for a clinical assessment of ectopic 3?

A

o 1. Visualisation/palpation of any obvious bumps of 3
o 2. Inclination of 2
o 3. Mobility of c or 2
o 4. Colour of c or 2

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84
Q

what kind of radiographic assessment is needed for ectopic 3? and what types of radiographs?

A

o 2 radiographs needed to localise position
 Usually OPT and upper anterior obloque occlusal
- parallax

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85
Q

what are the management options of an ectopic 3?

A

o 1. Prevention
 Appropriate monitoring from age 9 onwards
 Clinical assessment
 Symmetry
o 2. Extraction ‘c’ to encourage improvement in position of ‘3’ (interceptive)
o 3. Retain ‘3’ and observe (accept its position)
o 4. Surgical exposure and ortho alignment
o 5. (surgical) extraction
o 6. Autotransplantion

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86
Q

what do you do for palatally ectopic canines?

A
  • surgically expose them and align them with fixed appliances
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87
Q

describe ectopic 6s? what can be done?

A
  • More commonly U arch
  • Reversible before age 8
  • Caries risk
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88
Q

what are signs of ectopic 6s?

A

o Crowding (greater in CLP)
o Mesial path of eruption
o Abnormal morphology of E

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89
Q

what is management of ectopic 6s?

A

o 1. Separator
o 2. Attempt distalise ‘6’
o 3. Extract ‘e’

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90
Q

what do you check for in regards to ectopic 1?

A

o Sequence
o Symmetry

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91
Q

what are some possible causes of ectopic 1s?

A

o No obvious cause
o Supernumerary
 Tuberculate
 Odontome
o Trauma to primary predecessor
 Ankylosis or primary tooth
 Displacement of tooth germ
 Dilaceration of root

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92
Q

what is dilaceration of root?

A

when the root of a tooth is abnormally curved or bent

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93
Q

what does transposition mean?

A

Interchange in position of 2 teeth

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94
Q

what is classification of transposition?

A

True/pseudo

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95
Q

what teeth are most commonly transposition?

A
  • Upper canines and first premolar
  • Lower canines and incisors
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96
Q

what are tx options for transposition?

A
    1. accept
    1. Extract
    1. correct
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97
Q

what are some local abnormalities of soft tissues?

A
    1. Digit sucking
    1. Fraenum
    1. Tongue thrust
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98
Q

what are outcomes of digit sucking?

A

 1. Proclined UI
 2. Retroclined LI
 3. Anterior open bite
 4. Unilateral posterior crossbite
* Due to narrow maxillary arch
* May cause mandibular displacement

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99
Q

what would labial fraenum cause?

A

median diastema

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100
Q

what are types of local pathology that would cause malocclusion?

A
    1. Caries
    1. Cysts
    1. Tumours
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101
Q

what is physiology basis of ortho?

A

 If an external force is applied to a tooth, the tooth will move as the bone around it remodels
 This bony remodelling is mediated by the periodontal ligament
 If a tooth has no PDL or is ankylosed it will NOT move
 Cementum is much more resistant to resorption than bone, although some degree of root resorption after orthodontics should be expected

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102
Q

what is bone remodelling mediated by?

A

PDL

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103
Q

what is piezo-electric theory?

A
  • piezo-electric currents are generated when crystalline structures, such as bone, are deformed.
  • once thought to be the prime mechanism by which tooth movement was modulated.
  • however , these currents are relatively short-lived and very small so unlikely to play a significant role in bone remodelling
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104
Q

what is differential pressure theory?

A

in areas of compression bone is resorbed and in areas of tension is deposited

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105
Q

what is mechano-chemical theory?

A

The mechano-chemical theory of orthodontics proposes that tooth movement during orthodontic treatment is the result of a combination of mechanical and chemical factors. The mechanical aspect involves applying a controlled force to the teeth, causing bone deformation and remodeling, while the chemical aspect involves the biological response of the bone to the applied force. The theory suggests that the effectiveness of orthodontic treatment depends on both mechanical and chemical factors, and an understanding of the underlying biological mechanisms can help optimize treatment outcomes. Different types of appliances are used in orthodontic treatment to apply forces to the teeth, and the forces are carefully monitored and adjusted to achieve the desired tooth movement and minimize any adverse effects.

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106
Q

mechanical load is put onto fibres of what?

A

PDL

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107
Q

what do osteoblasts produce?

A

prostagladins and leukotrienes

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108
Q

what do fibroblasts produce in mechano-chemical theory?

A

matrix metalloproteinases (enzymes that break down the extracellular matrix)

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109
Q

what do macrophages increase in mechano-chemical theory?

A

interlukin 1 (IL-1)

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110
Q

osteocytes produce?

A

cytokine

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111
Q

cytokines activate what to recruit what?

A

osteoblasts to recruit osteoclasts

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112
Q

when cytokines active osteoblasts what do they produce?

A

prostagladins and leukotrienes

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113
Q

what do the postroglandins and leukotrienes cause osteoblasts to produce?

A

intracellular messenger (secondary messengers)

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114
Q

what do the intracellular secondary messenger initiate?

A

the production of receptor activator of nuclear factor RANKL and colony stimulating factor and interleukin-1

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115
Q

what does interleukin (IL-1) increase production of?

A

RANKL

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116
Q

what does RANKL and colony stimulating factor cause?

A

blood monocytes to fuse and form multinucleated osteoclasts

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117
Q

what does RANKL stimulate?

A

osteoclasts to become active and resorb the bone

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118
Q

what does the osteoblast do in areas of compression?

A
  • they bunch up together to expose the osteoid layer giving osetoclasts the access to resorb bone
  • osteoblasts send signs to osteoclasts (e.g RANKL) to recruit and activate osteoclasts to resorb bone
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119
Q

what does the osteoblasts do in areas of tension?

A
  • they are flattened covering the osteoid layer and preventing osteoclasts from gaining access to the bone
  • they secrete collagen and other proteins forming the organic matrix into which they then secrete hydroxyapatite crystals which forms new bone
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120
Q

what protein do osteoblasts release?

A

osteoprotegrin (OPG)

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121
Q

what does osteoprotegrin (OPG) prevent?

A

osteoclastic differentiation and suppresses their activity

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122
Q

how is bone remodelling regulated?

A

balance between amount of RANKL and OPG produced

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123
Q

what are types of appliances?

A
  • removable
  • functional
  • fixed
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124
Q

how do functional appliances work?

A
  • mandible postured away from normal rest position
  • facial musculature is stretched which generates forces transmitted to teeth and alveolus
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125
Q

types of tooth movement?

A

 Tipping
 Bodily movement
 Intrusion
 Extrusion
 Rotation
 Torque

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126
Q

what is weight of optimum tipping force?

A

35-60 grams

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127
Q

what is weight of optimum bodily movement force?

A

150-200 grams

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128
Q

what is weight of optimum intrusion force?

A

10-20 grams

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129
Q

what is weight of optimum extrusion force?

A

35-60 grams

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130
Q

what is weight of optimum rotation force?

A

35-60 grams

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131
Q

what is weight of optimum apical root torque force?

A

50-100 grams

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132
Q

what is intrusion in relation to ortho?

A

pressure on the supporting structures is evenly distributed and bone resorption is necessary, particularly at the apical area and at alveolar crest

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133
Q

what is extrusion in relation to ortho?

A

tension is induced in the supporting structures and bone deposition is necessary to maintain tooth support

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134
Q

how long would you wear a twin block?

A

6-12 months

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135
Q

what is mode of action of functionals?

A
  • skeletal change (30%), growth of mandible, restraint of maxilla
  • dentoalveolar change (70)% retroclination of upper teeth, proclination of lower teeth?
  • mesial migration of the lower teeth
  • distal migration of the upper teeth
  • combination of the above achieves class I
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136
Q

what is the effect of light force in ortho?

A

frontal resporption

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137
Q

what happens within PDL during light force?

A

hyperaemia

138
Q

what is there a resorption of from pressure side during light force?

A

lamina dura

139
Q

what happens to tension side during light force?

A

apposition of osteoid on tension side

140
Q

how is remodelling of socket known as for light force?

A

frontal resoprtion

141
Q

what happens to gingival fibres during frontal resorption?

A

appear not to become reorganised but remain distorted

142
Q

moderate forces during ortho is related to which type of resorption?

A

undermining resorption

143
Q

during moderate force what happens on pressure side?

A

occlusion of vessels of pdl

144
Q

during moderate force what happens on tension side?

A

hyperaemia of vessels pdl

145
Q

what kind of areas are on pressure side?

A

cell free areas on pressure side (hylinsation)

146
Q

theres a period of what during moderate forces?

A

stasis

147
Q

there is increases endosteal vascularity during moderate forces which is what?

A

undermining resorption

148
Q

what happens to tooth during moderate forces?

A

relatively rapid movement of tooth with bone deposition on tension side - tooth may become slightly loose

149
Q

what happens to pdl during moderate force at the end?

A

healing of pdl - reorganisation and remodelling

150
Q

what are unwanted side effects of excessive force? when is there root resorption significant?

A
  • Pain
    o Necrosis and undermining resorption takes place resulting in permanent changes
     Root resorption – significant If > 1/3 root length lost
     Anchorage loss
     Possible loss of tooth vitality
151
Q

what are factors that affect the response to ortho force?

A

o Magnitude
o Duration
o Age
o Anatomy
 No bone – wasting/cleft
 Soft tissues
 Mid-palatal suture

152
Q

what are deleterious effects of ortho force?

A

o Pain and mobility
o Pulpal changes
o Root resorption
o Loss of alveolar bone support
o Relapse

153
Q

how much movement of the tooth per month is ideal?

A

1mm

154
Q

how long is treatment time for fixed appliances?

A

24 months

155
Q

Why is the study of facial growth important to orthodontists?

A

o Insight into growth of the face
 predict changes
 utilize growth to correct malocclusion
 time our orthodontics and surgery
o Understand development of facial anomalies
o To measure changes in growth and treatment using cephalometry

156
Q

life in utero consists of what 2 phases and their times?

A

 embryonic – 1-8 weeks
 foetal – 8 weeks to term

157
Q

All of the limbs and organs including the face have formed within the…?

A

first 2 months

158
Q

what is nerual crest cell migration?

A

Neural crest cell migration is the process by which neural crest cells move from their site of origin in the neural tube to their final destination in various parts of the body during embryonic development

159
Q

when do the neural fold fuse to form the neural tube?

A

towards end of week 3

160
Q

what will failure of neural folds to fuse lead to?

A

failure to fuse will lead to spina bifida.

161
Q

what does the neural tube develop into?

A

brain and spinal cord

162
Q

what will failure of neural tube development lead to?

A

anencephaly

163
Q

what are neural crest cells?

A

During the folding of the neural plate, cells develop from the ectoderm along the edge of the groove, termed neural crest cells.

164
Q

what do neural crest cells do?

A
  • These undergo extensive migration within the developing embryo and ultimately differentiate into many cell types e.g. spinal and autonomic ganglia; Schwann cells, adrenal medulla, meninges of the brain.
  • This neural crest derived ectomesenchyme contributes to branchial arch cartilage, bone and connective tissue proper, as well as dental tissues - pulp, dentine, cementum and periodontal ligament.
165
Q

when does formation of face occur?

A

Formation of the face occurs during the first eight weeks after fertilisation

166
Q

defects of the face particularly midline is related to defects where?

A

defects of the anterior parts of the brain

167
Q

most of the face forms from what?

A

Most of the face forms from migrating neural crest cells, either in the frontonasal process or the branchial arches. Interference with this migration can lead to severe facial deformities.

168
Q

how does cleft formation come about?

A

Failure of fusion between the various facial processes or between the palatine processes

169
Q

what do the migrating neural crest cells do in week 4?

A

form the frontonasal process and laterally the branchial arches

170
Q

the skull can be divided into what 2 parts?

A

neurocranium
viscerocranium

171
Q

what is neurocranium?

A

forms a protective case around the brain

172
Q

what is viscerocranium?

A

forms the skeleton of the face

173
Q

what is intramembranous bone formation?

A

 Bone is deposited directly into primitive mesenchymal tissue.
 Intramembranous bones include the vault of the skull, the maxilla and most of the mandible.
 Needle-like bone spicules form, which progressively radiate from the primary ossification centres to the periphery. Progressive bone formation results in the fusion of adjacent bony centres.

174
Q

what is endochondral bone formation? What does it form?

A

 bones are preceded by a hyaline cartilage ‘model’
 forms base of skull
 Several centres of ossification which eventually fuse

175
Q

what does the base of the skull undergo?

A

undergo endochondral ossification from multiple centres, starting with the basi-occiput at 10-12 weeks.

176
Q

At birth cartilagenous growth centres remain between what?

A

the sphenoid and occipital bones and in the nasal septum

177
Q

when does the anterior fontanelle close?

A

2 years

178
Q

when does posterior fontanelle close?

A

1 year

179
Q

Growth occurs at fibrous sutures in response to what?

A

intracranial pressure

180
Q

growth of the skull continues until when?

A

7 years

181
Q

maxilla and mandible form in what way?

A

intramembranously

182
Q

what do maxilla and mandible develop adjacent to?

A

o Although the maxilla and mandible form intramembranously, they develop adjacent to a pre-existing cartilaginous skeletons - the nasal capsule and Meckel’s cartilage
o (6 weeks)

183
Q

the mandibular processes develops what units?

A

o A condylar unit
o An angular unit
o A coronoid unit
o An alveolar unit

184
Q

describe the condylar unit/

A

A condylar unit which forms the articulation and contains the largest secondary cartilage formation

185
Q

describe the angular unit?

A

An angular unit which forms in response to the lateral pterygoid and masseter muscles;

186
Q

describe the coronoid unit?

A

A coronoid unit which responds to temporalis muscle development (muscular processes).

187
Q

describe the alveolar unit?

A

o An alveolar unit which forms only if teeth are developing.

188
Q

the body of the mandible forms in response to what?

A

inferior dental nerve

189
Q

what are the 3 main sites of secondary cartilage formation in mandible? and when do they cartilages appear?

A
  • condylar cartilage
  • coronoid cartilage
  • symphyseal end of each half of the bony mandible
  • between 12 and 14 IU
190
Q

growth at the condylar cartilage continues until when?

A

20 years

191
Q

Ossification of the face and skull commences when?

A

7-8 weeks

192
Q

what is a primary abnomality?

A

 Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in it’s development (spina bifida, cleft lip, CHD)

193
Q

what is a secondary abnormality?

A

 Interruption of the normal development of an organ that can be traced back to other influences

194
Q

what is deformation?

A

 Anomalies that occur due to outer mechanical effects on existing structures

195
Q

what is agenesia?

A

 Absence of an organ due to failed development during embryonic period

196
Q

what is sequence?

A

Single factor results in numerous secondary effects (PierreRobin)

197
Q

what is syndrome?

A

 Group of anomalies that can be traced to a common origin
(Trisomy 21 in Down’s Syndrome)

198
Q

what are some facial syndromes arising from early problems with facial development? (1-8 week)

A

 Foetal Alcohol Syndrome
 Hemifacial microsomia
 Treacher Collins syndrome (mandibulofacial dysostosis)
 Clefts of lip and palate

199
Q

describe foetal alcohol syndrome?

A

o microcephaly (small head)
o typical facies having
 short palpebral fissures,
 short nose,
 long upper lip with deficient philtrum,
 small midface
 small mandible.
o Mild mental retardation

200
Q

describe hemifacial microsomia?

A

o Multifactorial
o Neural crest cell migration? (day 19-28)
o 3D Progressive facial asymmetry
o Unilateral mandibular hypolasia, zygomatic arch hypoplasia, high arched palate, malformed pinna
o But clinical spectrum (ear tags only, to complete lack of condyle, coronoid and ramus)
o Normal intellect, deafness, cardiac and renal problems

201
Q

describe treacher collins?

A

o Deformity of 1st and 2nd branchial arches, (day 19-28)
o Anti-mongoloid slant palpebral fissures
o Colomboma of lower lid outer 1/3rd
o Hypoplastic or missing zygomatic arches
o Hypoplastic mandible with antigonial notch
o Deformed pinna, conductive deafness

202
Q

what are dental features of cleft?

A

o impacted Teeth
o Crowding
o Hypodontia
o Supernumeraries
o Hypoplastic teeth
o Caries

203
Q

Syndromes associated with problems of development of the skull and facial bones?

A

o Achondroplasia
o Crouzon’s (craniofacial dysostosis)

204
Q

what is achodnroplasia?

A

 Problem with endochondrial ossification
 Defects in long bones, short limbs =dwarfism(70%)
 Defects in base of the skull, retrusive middle third of the face, frontal bossing, depressed nasal bridge
 Defects in base of the skull, retrusive middle third of the face, frontal bossing, depressed nasal bridge

205
Q

what is crouzon’s?

A

 Premature closure of cranial sutures (esp coronal and lamdoid)
 Proptosis (shallow orbits), orbital dystopia, mild hypertelorism
 Retusion and vertical shortening of midface
 Prominent nose
 Class III malocclusion
 Narrow spaced teeth
 Early closure of the sutures is termed cranial synostosis and requires surgical intervention. e.g. Crouzon’s syndrome.
 Distraction osteogenesis

206
Q

what are sutures?

A

 Specialised fibrous joints situated between intramembranous bone
 Each suture is a band of connective tissue which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth

207
Q

growth of sutures is a response to what?

A

growing structures separating the bone – e.g. growth of the calvarium in response to development of the brain. Where the bones are pushed apart new bone forms in the suture. In the suture growth occurs in areas of tension.
 When facial growth is complete the sutures fuse and become inactive

208
Q

where are synchondroses found? Exist between what?

A

 These are found in the midline
 They exist between the ethmoid, sphenoid and occipital bones
 A cartilage – based growth centre with growth occurring in both directions. The bones on either side of the synchondrosis are moved apart as growth takes place.
 New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone

209
Q

when is the rate of growth greatest?

A

during first 3 years

210
Q

how does growth occur in cranial vault?

A
  • Bone growth at the sutures
  • External and internal surfaces are remodelled through surface deposition and resorption to displace the bones radially
211
Q

where do fontanelles form? How many present at birth and when do they close by?

A

more than 2 bones meet
-6 fontanelles are present at birth and these close by age 18 months. When facial growth is complete all of the sutures fuse

212
Q

how does growth occur in cranial base?

A

 Endochondral ossification
 Surface remodelling

213
Q

when does the spheno-ethmoidal synchondrosis fuse?

A

around 7 years

214
Q

when does spheno-occipital synchondrosis close?

A

13-15 years in females
15-17 in males

215
Q

when does spheno-occipital synchondrosis fuse?

A

around 20 years

216
Q

how does cranial base play and important role in determining how the maxilla and mandible relate? In terms of angles

A

 A small angle is more likely to be associated with a class III skeletal relationship
 A large angle more likely to be associated with a class II skeletal pattern

217
Q

what are Differences in the growth of the maxilla and mandible?

A

o Mandible
 Increases in length by 26mm in males 20mm in females between ages 4-20 years
 Growth accelerates significantly during the pubertal growth spurt
 Growth slows to adult level around age 17 years in females and 19 years in males
o Maxilla
 Increases in length by 8mm in males 5.5mm ( females) between ages 4-20 years
 After age 7 years growth of the maxilla proceeds very slowly
 Growth slows to adult levels at around age 12 years

218
Q

what is a growth rotation due to?

A

A growth rotation is due to an imbalance in the growth of the anterior and posterior face heights

219
Q

what does forward rotations lead to?

A

short face

220
Q

what does backwards rotations lead to?

A

long face

221
Q

how does adult facial growth affect you?

A

o Tendency to increased overall length and prominence of nose and chin (and forehead in men)
o Lips become thinner and more retrusive (soft tissue changes)

222
Q

how to measure facial growth changes?

A

o Casts of the face
o Cephalometry
o 3D laser scanning
o 3D photogrammetry

223
Q

what are indications for lateral cephalometry?

A

 To aid diagnosis
 Treatment planning
 Progress monitoring
 Research projects Indications for taking a lateral ceph.

224
Q

how are lateral cephalometry good?

A

Reproducible - patient positioned in a cephalostat a set distance from the cone and the film

225
Q

what do you identify and measure with a lateral cephalometry?

A

o Identify
 Points, landmarks with precise definitions
 Lines
o Measure
 Lengths
 Heights
 Angles
o Relationship between jaws and cranial base
o Relationship between the upper and lower jaw
o Position of teeth relative to the jaws
o Soft tissue profile Analysis

226
Q

what is eastman analysis?

A

Measures the antero-posterior position of the maxilla and mandible relative to the base of skull

227
Q

what are errors in cephalometry?

A

o Radiographic projection errors
o Errors within the measuring system
o Errors in landmark identification

228
Q

what are radiographic projection errors in cephalometry?

A

 magnification
 distortion

229
Q

what are errors within the measuring system in cephalometry?

A

non linear fields

230
Q

what are errors in landmark identification in cephalometry?

A

 quality of image
 landmark definition and location
 operator and registration procedure

231
Q

what is eruption of deciduous teeth

A

o 6 months-2.5yrs
o a-b-d-c-e
o lowers before uppers

232
Q

when to extract natal/neo-natal teeth?

A

 mobile and presents a risk of inhalation
 Is causing difficulty with breastfeeding

233
Q

what are most common natal tooth?

A

lower incisors

234
Q

when does pre eruptive phase start and end?

A

 starts when the crown starts to form and ends when crown formation complete / root formation about to start.

235
Q

what is pre-eruptive phase?

A

 The developing crowns move constantly within the jaws
 Small mesial and distal tooth movements occur
 The developing crowns reposition themselves in response to increasing length , width and height of the jaws
 Movement of tooth crowns is contained within the bony crypts

236
Q

when does eruptive phase start and end? And what is it split into?

A

starts as soon as the root starts to form and ends when the teeth reach the occlusal plane Split into intra-osseous stage and extra-osseous stage.

237
Q

why do relative position of deciduous and permanent teeth alter in eruptive phase?

A

eruption of the deciduous teeth and increase in height of the surrounding alveolar bone

238
Q

movements in eruptive phase occur in response to what?

A
  • Positional changes of neighbouring crowns
  • Growth of the mandible and maxilla
  • Resorption of the deciduous tooth roots
239
Q

what is the root formation part of intra osseous in eruptive phase?

A
    1. Root formation – starts with proliferation of the epithelial root sheath and continues with the production of dentine and pulp
240
Q

just explain intra-osseous in eruptive phase?

A
    1. Root formation – starts with proliferation of the epithelial root sheath and continues with the production of dentine and pulp
    1. Movement of the developing tooth – in an occlusal or incisal direction (slow - several months)
    1. The reduced enamel epithelium fuses with the oral epithelium
  • Within the Dental follicle degeneration occurs. Blood vessels decrease in number, nerve fibres break up into pieces. The resulting area becomes known as the ‘eruption pathway’
    o In the periphery of the eruption pathway other fibres are formed from the dental follicle . This is known as the Gubernacular cord. Theory : this guides the teeth to erupt in the oral cavity
  • Adjacent to, and overlying, the teeth bone loss keeps pace with the occlusal movement of the teeth (osteoclasts and osteoblasts are constantly remodelling the bone)
241
Q

what is eruption pathway?

A
  • Within the Dental follicle degeneration occurs. Blood vessels decrease in number, nerve fibres break up into pieces. The resulting area becomes known as the ‘eruption pathway’
242
Q

what guides the teeth to erupt in oral cavity and what is it known as?

A

In the periphery of the eruption pathway other fibres are formed from the dental follicle . This is known as the Gubernacular cord. Theory : this guides the teeth to erupt in the oral cavity

243
Q

what is extra-osseous?

A
    1. Penetration of the tooth’s crown tip through the epithelial layers (fast 1-2 weeks )
    1. The crown continues to move through the mucosa in an occlusal direction until it contacts the opposing tooth (slow -several months)
    1. Environmental factors such as muscle forces from cheeks, lips and tongue help determine final tooth position
244
Q

what is post-eruptive phase?

A

 tooth movement / eruption continues as the root forms and throughout life in extremely small increments

245
Q

what does movement in post eruptive phase occur in response to?

A
  • Occurs in response to increases in height of the growing alveolar bone and jaws
  • In response to attrition and abrasion
    o teeth erupt slightly to compensate for wear on occlusal surfaces
    o proximal surface tooth wear leads to mesial drift
  • In response to loss of opposing teeth = over-eruption
246
Q

what does proximal surface tooth wear lead to?

A

o proximal surface tooth wear leads to mesial drift

247
Q

what causes teeth to erupt?

A

 Root formation
 Remodelling of the alveolar bone
 Development of the periodontal ligament (membrane)

combo of

248
Q

where does signalling for teeth to erupt take place?

A

It is believed that signalling takes place between the dental follicle and the reduced enamel epithelium

249
Q

what is tooth eruption controlled by?

A

Tooth eruption is controlled by a signalling cascade of cytokines (including Interleukin1, CSF 1, RANKL/ Osteoprotegerin pathway)

250
Q

what are the roles of the dental follicle?

A

 Initiates resorption of the bone overlying the tooth
 Facilitates connective tissue degradation and creates the eruption pathway
 Promotes alveolar bone growth at the base of the tooth
Provides traction forces within the periodontal ligament (special fibroblasts with contractile properties)
 Ectomesenchymal cells from dental follicle contribute to root formation (cementoblasts and cementum)

251
Q

what is definition of interceptive ortho?

A

Any procedure that will reduce or eliminate the severity of a developing malocclusion’

252
Q

how is space gained to accomomadate larger anterior teeth of the permanent dentition?

A
  • increase in the intercanine width through lateral growht of jaws
  • upper incisors erupting onto a wider arc
  • leeway space
253
Q

what is leeway space of upper arch?

A

primary canine + first molar + second molar

minus

permanent canine + first premolar + second premolar

=

1 to 1.5mm

254
Q

what is leeway space of lower arch?

A

primary canine + 1st molar + 2nd molar

minus

permanent canine + 1st premolar + 2nd premolar

=

2 to 2.5mm

255
Q

what is diastema?

A

gap in between teeth

256
Q

when should a diastema close?

A

<2.5mm

257
Q

what are the management options if a first permanent molar gets stuck between the ‘e’ and fails to fully erupt?

A
    1. If patient <7years wait 6 months (90% self correct)
    1. Orthodontic Separator
    1. Attempt to distalise the first molar
    1. Extract E
    1. Distal disking of ‘e’
258
Q

what is case assessment of unerupted central incisors?

A
  • Case history –esp. regarding trauma
  • palpate labially and palatally
  • if retained Primary tooth present, Is primary mobile? Is it discoloured ?
  • Radiograph (AOM/ Periapical)
259
Q

how to deal with unerupted central incisor supernumeraries?

A
    1. Remove primary teeth & Supernumeraries
    1. Create space/maintain space
    1. Monitor for 12 months
      If patient < 9 years (immature root apex)
      Still fails to erupt? OR patient >9 years (mature root apex)
    1. Expose/bond gold chain and apply orthodontic traction
260
Q

what does early loss of decidous teeth cause?

A

localised crowding

261
Q

how does the effect of localised crowding from early loss of deciduous teeth vry?

A
  • Degree of crowding already present
  • Age
  • Which arch? Which tooth?
262
Q

what is a balancing extraction and why?

A

o Balancing Extraction = removal of a tooth from the opposite side of the same arch
Why?
 To maintain the position of the dental centreline (preserve symmetry)

263
Q

what is a compensating extraction and why?

A

o Compensating Extraction = removal of a tooth from the opposing quadrant
Why?
 To maintain the buccal occlusion.

264
Q

what is management of early loss of A’s and B’s?

A

 little impact
 don’t balance or compensate

265
Q

what is management of early loss of C’s

A

balance

266
Q

what is management of early loss of D’s?

A

small CL. shift, balance under GA?

267
Q

what is management of early loss of E’s

A

 tend not to balance
 major space loss
 upper>lower
 Consider space maintainer

268
Q

describe compensating for a C?

A

if you remove an upper C you gotta remove a lower C

269
Q

what are types of space maintainers?

A
  • removable
  • fixed
270
Q

what is a type of removable space maintainer?

A

passive URA

271
Q

what are typical components of passive URA?

A

o Retention e.g. clasp UR6,UL6 (0.7mmHSSW) Labial bow UR3 to UL3 (0.7mmHSSW) OR Southend clasp (0.7mmHSSW)
o Baseplate – extend acrylic around teeth to prevent unwanted mesial drift
o +/-Mesial Stop (0.6mm HSSW) on individual teeth if required

272
Q

what would factors of extracting carious 6’s be?

A

o Age of patient / stage of dental development
o Degree of crowding
o Malocclusion type

273
Q

when would the most ideal result of extracting carious 6’s?

A

o 7’s bifurcation calcifying
o 8’s present
o Class 1 av/reduced OB
o Moderate lower crowding
o Mild/moderate upper crowding

274
Q

what are general rules for extracting class 1 6’s?

A

o If extracting lower take upper
o Don’t balance with sound tooth. Don’t balance if well aligned or spaced.
o If extracting upper don’tneed to take lower.

275
Q

how to clinically assess anterior cross-bites?

A
  • displacement
  • mobility of lower incisor
  • tooth wear
  • gingival recession
276
Q

what are types of cross bite?

A
  • Posterior Unilateral Crossbites
  • posterior cross-bites
  • anterior cross-bites
277
Q

what does anchorage mean?

A

prevention of unwanted tooth movements

278
Q

when is treatment of posterior unilateral cross bite needed?

A

only if it shifts midline by >2mm. so if pt bites down and between the motion to RCP he laterally shifts >2mm then thats treatment needed

279
Q

what is digit habit management?

A
  1. positive reinforcement
  2. bitter-tasting nail varnish
  3. glove on hand, elastoplast
  4. habit breaker appliance (habit deterrent) - fixed or removable
280
Q

breakdown interceptive ortho and what you do and for what?

A

-unerupted incisors - remove ob/space/obs
- impacted 6’s - observe 6/12 or intercept
- balance c’s - but not critical
- carious lower 6’s - take upper
- uni cross bites - IOTN displacement?
- habits - stop before 9

281
Q

what can be used to help fix habits?

A

detterents apliance

282
Q

Why is correct orthodontic diagnosis important?

A

Orthodontic appliances can move teeth very well,
but can modify skeletal relationship minimally.

A severe skeletal discrepancy may require
surgical intervention.

283
Q

what are objectives of ortho treatment?

A

To produce an occlusion which is:

  • Stable
  • Functional
  • Aesthetic

And to facilitate other forms of
dentistry (crowns, bridges etc.)

284
Q

what are stages of treatment planning?

A
  1. Plan around the lower arch (angulation of LLS is stable)
  2. Decide on treatment in lower (ext/nonext)
  3. Build upper arch around lower
    aim for class I incisor and canine relationship (OJ and OB normal*)
  4. Decide on molar relationshipClass I or full unit class II molar relationship

(if upper and lower incisors normal size, shape and number)

285
Q

what do you look to examine in lower arch?

A
  • Crowding / Angulation of incisors Mand plane
  • Angulation of the canines / Centrelines
  • Curve of Spee

Space required? What are the options?
Extraction or non extraction?

286
Q

what do you look to examine in upper arch?

A
  • Crowding /Angulation of incisors to the Max Plane
  • Angulation of the canines / Centrelines
287
Q

what do you examine when teeth in occlusion ICP?

A

Incisor relationship
OJ
OB (curve of Spee)
Centrelines
Canine relationship
Molar relationship

288
Q

what do you consider when assessing crowding?

A

Do you need to extract teeth?
Measure space available and space required
Overlap technique

289
Q

what are the general principles in space required in lower arch?

A

Mild (0-4mm)
moderate (5-8mm)
sever (8+mm)

290
Q

what are the general principles in space required in lower arch?
if mild (0-4mm)

A

non-ext (stripping)
ext 5’s

291
Q

what are the general principles in space required in lower arch?
if moderate (5-8mm)

A

ext 5’s
ext 4’s

292
Q

what are the general principles in space required in lower arch?
if severe (8+mm)

A

ext 4’s

293
Q

what are the general principles to consider when considering lower arch extraction when yes and no?

A

yes
- extract in upper arch (MR class I)

No
- extract in upper arch (MR class II)
- Distalise UBS using headgear (MR class I)

294
Q

what are treatment options?

A
  1. Accept malocclusion
  2. Extractions only
  3. URA
  4. Functional appliances
  5. Fixed appliances
  6. Complex treatment involving orthodontics and restorative treatment or orthodontics and orthognathic surgery
295
Q

what are limitations of ortho treatment?

A

Effects of orthodontic treatment are almost purelydentoalveolar and tooth movement, with little effect on theskeletal pattern.

Tooth movements are limited by the shape and size of thealveolar processes.

Teeth will only remain stable in a position where there isequilibriumbetween the forces of the soft tissues, theocclusion and the periodontal structures. All other positionsare unstable and will be prone to relapse.

296
Q

what do you asses clinical for anterior cross bites?

A

 Displacement?
 Mobility of lower incisor
 Tooth wear
 Gingival recession

297
Q

why treat anterior open bite early?

A

o To maximise potential for spontaneous correction of anterior open bite whilst there is still eruptive potential for incisors (8-10 years/ root formation still incomplete)
o To prevent effects on vertical and transverse skeletal development which could lead to permanent skeletal change if habit persists

298
Q

what are steps of digit habit management?

A

o 1. Positive reinforcement
o 2. Bitter-tasting nail varnish
o 3. Glove on hand, Elastoplast
o 4. Habit breaker appliance (habit deterrent) – fixed or removable

299
Q

what is the aetiology of infra occluding teeth?

A

ankylosis of primary tooth. surrounding alveolar bone continues to grow. primary tooth gets left behind?

300
Q

what is the diagnosis of infra occluding teeth?

A
  • perucssion
  • check for mobility
  • radiographs
301
Q

what do you assess radiograph for with infra occlusion?

A
  • presence /absence of successor
  • Ankylosis of primary tooth (no PDL space/no clear lamina dura)
  • Root resorption of primary
302
Q

what do you do if permanent successor is present when dealing with infra occlusion?

A
  • Monitor 6-12 months
  • Extract if primary tooth is below the interproximal contact point
  • Consider extraction if root formation of successor near completion
  • If extract …..maintain space
  • Be more vigilant in upper arch
303
Q

how long do you monitor permanent successor present for infra occlusion?

A

6- 12months

304
Q

when do you extract if permanent successor is present when dealing with infra occlusion? and what do you do after if you extract?

A
  • Extract if primary tooth is below the interproximal contact point
  • Consider extraction if root formation of successor near completion
  • If extract …..maintain space
305
Q

what are doing nothing if permanent successor is present when dealing with infra occlusion?

A
  • Permanent successor can become more ectopic
  • Infra-occlusion worsens with tipping of adjacent teeth - primary tooth becomes inaccessible for extraction
  • Caries and periodontal disease
306
Q

when does infra occlusion worsen?

A
  • Infra-occlusion worsens with tipping of adjacent teeth - primary tooth becomes inaccessible for extraction
307
Q

when dealing with infra occlusion what does treatment plan depend on if permanent successor is absent?

A

o degree of crowding
o degree of infra-occlusion
o any other features of malocclusion ?

308
Q

when dealing with infra occlusion what do you do if you extract when permanent successor is absent?

A

plan space mangement
o Either maintain space for prosthetic tooth
o Reduce space to one premolar unit ( requires fixed appliance)
o Close space ( fixed appliance)

309
Q

in delayed eruption when should you assess position of upper canines?

A
  • Assess position of upper canines from (9 to) 10 years onwards
  • Should palpate by 11 years
  • Mobile C’s, symmetry
  • Angulation of lateral incisors
310
Q

when is extraction fo the c’s likely to be successful?

A

o Patient is age between 10-13 years
o The canine is distal to the midline of the upper lateral incisor
o There is sufficient space available
o The canine is less than 55 degrees to mid-sagittal plane

311
Q

what are the risks of doing nothing when dealing with ectopic primary maxillary canines?

A

o Permanent successor can become more ectopic
o Permanent canine then fails to erupt (Impacted Canine)
o Risk of root resorption of adjacent teeth
o Risk of root resorption of canine crown (lower risk)
o Risk of cyst formation around canine (rare)

o Permanent canine can become ankylosed (incidence tends to increase with age)

312
Q

what are the options for growth modification for interceptive treatment of class III?

A
  • Protraction headgear +/- RME (rapid maxillary expansion)
  • Functional appliances e.g.Reverse Twin Block / Frankel III
313
Q

when is growth modification in class III most successful?

A
  • skeletal I or only mild class III
  • maxillary retrusion
  • anterior displacement on closing
  • avergae or reduced lower face height
  • patient age 8-10 years
314
Q

what are general aetiological factors of malocclusion?

A

 Skeletal
 Muscular
- form and function of muscles that surround teeth
 dentolveolar
- size of teeth in relation to size of jaws

315
Q

what are possible environmental factors of malocclusion?

A

 masticatory muscles
 mouth breathing
 head posture

316
Q

in class 1 skeletal what may jaws have?

A

jaws usually correctly sized but may have bi-maxillary protrusion or retrusion

317
Q

what is a lateral cephalogram?

A
  • standardised lateral radiographs of the face and base of skull
  • reproducible – pt position in a cephalostat a set distance from cone and film
318
Q

what is radiographic technique of lateral cephalogram?

A
  • ALARA
    o Aluminium soft tissue filter
    o Thyroid collar
    o Triangular collimation
    o Fastest film possible (60-70kV)
319
Q

where is the frankfurt plane measure from?

A

lower orbital rim to superior border of external acoustic meatus

320
Q

where is mandibular plane?

A

lower border of mandible

321
Q

where do manibular and frankfurt planes meet?

A

external occipital protuberance

322
Q

what is a long facial type from? what tendency does it tend to have?

A
  • backward mandibular growth rotation
  • anterior open bite tendency
323
Q

what is a short facial type from and what does it tend to have? what tendency does it have?

A
  • forward mandibular growth rotation
  • deep overbite tendency
324
Q

what doe arches with discrepancies tend to have?

A

causes unilateral or bilateral buccal segment cross bite

325
Q

when does mandibular displacement occur?

A

occurs when inter arch width discrepancy causes upper and lower teeth to meet cusp to cusp

326
Q

what is dental causes of facial asymmetries?

A
  • displacement of normal mandible due to unilateral cross bite
327
Q

what is crowding caused by?

A

small jaws normally sized teeth
macrodontia

328
Q

what is macrodontia?

A

large teeth

329
Q

what is spacing caused by?

A

large jaws, normally size teeth or small teeth microdontia

330
Q

in class 1 cephalometrics what does SNA, SNB and ANB relate to?

A

o SNA relates maxilla to anterior cranial base
o SNB relates mandible to anterior cranial base
o ANB relates mandible to maxilla

331
Q

in class 1 cephalometrics what is average value of SNA?

A

ave value 81 degrees +/- 3 degrees

332
Q

in class 1 cephalometrics what is average value of SNB?

A

ave value 78 degrees +/- 3 degrees

333
Q

in class 2 cephalometrics what is ANB value?

A

ANB > 5 degrees

334
Q

in class 3 cephalometrics what is ANB value?

A

ANB < 1 degree or negative

335
Q

what is upper anterior face height measured from?

A

 Brow ridge (glabella) to base of nose

336
Q

what is lower anterior face height measured from?

A

 Base of nose (sub nasale) to inferior aspect of chin (soft tissue menton)

337
Q

what is average ratio of lower anterior face height to total anterior face height?

A

Average ratio LAFH to TAFH = 50 percent

338
Q

what is average value of FMPA?

A

27 degrees +/- 4 degrees

339
Q

for long facial height what is the fmpa and LAFH to TAFH values?

A

o LAFH to TAFH proportion > 55 percent
o FMPA > 31 degrees

340
Q

for short facial height what is the fmpa and LAFH to TAFH values?

A

o LAFH to TAFH proportion < 55 percent
o FMPA < 23 degrees

BDS3: Clinical dental sciences (11 decks)

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