Aetiology of malocclusion Flashcards
1
Q
What are the three main factors that contribute to occlusal development
A
Skeletal factors
Soft tissue factors
Dentoalvolar factors
2
Q
Environmental factors affecting occlusion
A
Habits
Early loss or trauma of primary tooth
3
Q
What are the three planes
A
Anteroposterior
Vertical
Transverse
4
Q
Describe class I skeletal anteroposterior pattern
A
Maxilla and mandible are in the correct position with respect to the cranial base
5
Q
Describe class II skeletal anteroposterior pattern
A
Mandible positioned more posteriorly than ideal
6
Q
What can contribute to a class II skeletal AP pattern
A
- Mandibular retrognathia or a small mandible
- Maxillary prognathia
7
Q
Describe class III anteroposterior skeletal pattern
A
Mandible in occlusion is positioned more anteriorly relative to the maxilla
8
Q
What contributes to a class III skeletal anteroposterior pattern
A
Retrognathia maxilla
Large mandible
Prognathic mandible
Combination
9
Q
What causes increased vertical dimensions of the face
A
High gonial angle
Posterior (clockwise) growth of the mandible
Vertical maxillary excess
10
Q
What occlusal discrepancies can occur due to an increased facial height
A
Incomplete overbite
AOB
11
Q
What causes decreased vertical dimensions of the face
A
Low gonial angle
Anterior (anti-clockwise) growth of the mandible
12
Q
What does vertical maxillary excess lead to
A
Increased facial height and chin point retrusion
13
Q
What is the ideal transverse skeletal relationship
A
Maxilla slightly larger than mandible allowing for the normal buccal overjet of 2-4mm
14
Q
Describe the two transverse discrepancies and their causes
A
Buccal posterior crossbite due to narrow maxilla or wide mandible
Lingual crossbite due to wide maxilla or narrow mandible
15
Q
Describe the equilibrium between teeth and muscles
A
The muscular forces acting directly on the teeth must be in balance in order to maintain a stable position
16
Q
What is the neutral zone
A
Where the forces of the lips and cheeks (outside) are balanced by the forces of the tongue (inside)
17
Q
What are the soft tissues that affect the occlusal development
A
Lips, tongue, adenoids and PDL
18
Q
What features of the lips can influence occlusion
A
Size
Form / fullness
Seal
Lip line
19
Q
Occlusion associated with full, everted lips
A
Bimaxillary proclination
20
Q
What type of lip form results in retroclined lower incisors
A
Tense lips
Strap like lips
21
Q
Describe the cause of strap like lips
A
Hyperactive mentalis muscle
22
Q
What is lip incompetence
A
Lips do not meet at rest
23
Q
What are potentially competent lips
A
Lips who are able to come together with slight circumoral muscle activity
24
Q
What are the types of adaptive swallowing mechanisms in incompetent lips
A
Circumoral lip to lip
Tongue to lip
Lower lip to palate
25
What does lip incompetence result in
Proclination of the incisors due to tongue positioned anteriorly
26
What type of adaptive seal is associated with class III
Tongue to upper lip
27
Define lip line
The level at which the lower lip meets the upper incisors in normal function
28
What is the ideal lip line
Lower lip should cover the lower incisal 1/3rd of the labial surface of the upper incisors at rest
29
What is a lip trap?
| What malocclusion is it associated with?
Lower lip is positioned behind the upper incisors at rest (CLASS2/1)
30
How does macroglossia influence occlusion
Large tongues rest on the front teeth causing bimaxillary proclination which can cause AOB or incomplete overbite
31
How does loss of PDL influence tooth position
Loss of PDL in perio disease results in loss of equilibrium resulting in spacing, extrusion, tilting, incr OJ
32
How do large adenoids affect breathing
Obstructed nasal breathing resulting in mouth breathing
33
What can large adenoids/mouth breathing influence
It can affect skeletal pattern
34
How does mouth breathing affect occlusion?
Head tilts upwards slightly therefore tongue position drops and cheek pressure is unopposed
35
What are the typical features of adenoid facies?
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Increased vertical dimension
Backward rotation of the mandible
Narrow maxilla / posterior crossbite
Reduced overbite
Narrow nose
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36
What effect can digit sucking have on the dentition
- Proclined upper incisors with increased overjet
- +/- Retroclined lower incisors
- Asymmetrical AOB or incomplete overbite
- Narrow maxilla with a unilateral buccal crossbite
37
How does digit sucking narrow the maxilla
Increased buccal pressure on the buccal aspects of the teeth resulting in lateral displacement of the mandible into ICP (buccal xbite)
38
What does the effect of digit sucking on occlusion depend on
Age of patient
Frequency during the day
Manner in which the digit is sucked
39
How many hours a day is digit sucking required to have a significant effect
>6 hours a day
40
What is an example of an iatrogenic environmental factor affecting occlusion
Poorly designed mouth gaurds allowing 7s to over erupt forming an AOB
41
List local dental aetiological factors of malocclusion
- Abnormal tooth number
- Abnormal tooth size
- Abnormal tooth position
- Abnormalities in local soft tissue
- Habits
42
List factors affecting tooth number
Hypodontia
Premature primary tooth loss causing impaction
Supernumerary teeth
43
What are the potential effects of supernumerary teeth
- Failure of eruption
- Displacement of unerupted tooth
- Crowding with supplementals
- No effect if unerupted
- Cystic transformation
- Root resorption
44
Management of a supernumerary tooth preventing eruption of a permanent tooth
Surgical removal of the supernumerary tooth
| Exposure of the permanent tooth with gold chain placement to move it into position
45
Management of supplemental teeth causing crowding
Removal the tooth which is most poorly formed or displaced
46
Why should unerupted supernumeraries be monitored
Resorption of roots
| They have potential for cystic formation (monitor for radiographic signs of follicular enlargement)
47
What dental anomalies are associated with hypodontia
- Impacted upper canines
- Delayed dental development
- Microdontia
- Retained primary teeth
- Reduced LFH and incr overbite
- Ectodermal dysplasia (anodontia)
48
Significance of hypodontia in class III patients
Space closure in a labial segment may compromise the incisor relationship further
49
Significance of hypodontia in class II div 1
Space closure in the labial segment may aid overjet reduction
50
Tx options for hypodontia
- Do nothing
- Maintain or redistribute space and place restoration
- Ortho space closure and disguise adjacent teeth
51
What is Kesling's trial set up used for
- Assess feasibility for treatment options in hypodontia
| - Show teeth after ortho tx
52
In which instances does premature loss of a primary tooth have a greater effect?
- Crowded dentitions
- Maxillary tooth
- Younger patients
- the type of tooth lost
53
In general, when is more space lost when a primary tooth is lost prematurely
Maxilla > mandible
| E > D
54
Effect of early loss of primary incisors
Minimal impact on occlusion
| Possibly some space loss in crowded dentitions
55
Effect of early loss of primary canine
If unilateral loss = centre line shift to affected side in crowded dentitions
- Space loss for permanent canines
56
Management of early loss of primary canines
- Balanced extractions in crowded dentitions to avoid loss of centreline
57
Effect of premature loss of primary first molar (Ds)
- Small centre line shift in crowded dentitions
- Mesial movement of E and 6 without rotation or tilting
- Space loss for canines in the maxilla
- Space loss for canines or 4s in the mandible
58
Management of premature loss of Ds
- Balancing extractions
| - Space maintainers
59
Effects of premature loss of second primary molar (Es)
- Little effect on centreline
- Mesial drift of molars with space loss
- If 6s unerupted, they will erupt anteriorly
- If 6s erupted - there is mesial tipping, rotation and impaction of 5s
60
Management of premature loss of Es
Space maintainers in all but spaced arches
61
List causes of abnormally placed teeth
Abnormal position of crypts
Infraoccluded teeth
Transposition
Displaced (e.g. due to crowding)
62
What would indicate an abnormal position of crypts
Displaced or rotated crypts
63
What are the occlusal complications of infraoccluded teeth
Tipping of adjacent teeth
Deviation of dental centreline to affected side due to stretching of transseptal fibres
Inhibition of vertical development of adjacent teeth
64
What is transposition
Position of the teeth are interchanged
65
Which teeth are commonly transposed
Maxillary canines and first premolars
66
Which teeth are commonly impacted
Maxillary canines
Second premolars (upper and lower)
Maxillary central incisors
67
What is the aetiology of displaced/impacted teeth
- Abnormal position of tooth germ
- Crowding
- Retention of primary tooth
- Presence of supernumerary
- Presence of pathology e.g. cyst
68
Management of a displaced tooth
If mild - extract primary + space maintain, surgical exposure of displaced tooth with traction
If severe - extract tooth
69
Which teeth become displaced if crowding is the aetiology
The last tooth in the series - upper 2s, upper 3s, 5s and 8s
70
Management of displaced teeth due to crowding
Relief of crowding and active tooth movement
| If severe, extract
71
What is the prevalence of ectopic upper canines
2%
72
Where can a canine be deflected in severe displacement
Horizontally near the floor of the nose
73
What are ectopic canines associated with
Small or absent lateral incisors
74
Management for ectopic canines
- Remove retained C for spontaneous repositioning
- if mild - extract upper 4s to provide space
- If severe - surgical exposure and traction OR surgical transplantation OR surgical extraction
- Leave it
75
Describe surgical transplantation of ectopic canines
The displaced canine is surgically removed and splinted in position for 2-3 weeks
76
Disadvantages of surgical transplantation of ectopic canines
Space needs to be present in the arch
| There is 50% risk of root resorption
77
When is extraction of ectopic canines indicated
Poor prognosis e.g. poorly formed crown or root
| No other option is feasible
78
DELETE
Microdontia
Macrodontia
Crowding
Spacing
79
What is microdontia linked to
Hypodontia
| Microdontia upper lateral with ectopic upper canine
80
What is macrodontia linked to
Supernumerary teeth
81
What is crowding a manifestation of
Dentoalveolar disproportion (mismatch between tooth size and jaw)
82
What is the aetiology of crowding
- Genetics determining dentoalveolar proportions
| - Environmental factors/local - early loss of primary teeth, supernumerary teeth, megadontia
83
What are the types of crowding
Primary - inherent discrepancy in tooth size to jaw size
Secondary - to environmental factors
Tertiary - late lower incisor crowding
84
What is the severity classification of crowding
Mild <4mm
Moderate 5-9mm
Severe >9mm
85
Tx options for mild crowding
- Arch expansion using a fixed appliance (common)
- Interproximal stripping
- Molar distalisation with headgear (not common)
- NO EXTRACTIONS
86
Tx options for moderate-severe crowding
- Extractions to relieve crowding
87
What influences extraction pattern in treatment of moderate-severe crowding
- Quality/prognosis of teeth
- Severity and location crowding
- Anchorage requirements
88
Anchorage requirements in extraction basis for crowded teeth
- If more space required anteriorly - extract 4s
| - If space required posteriorly - extract 5s
89
What are the best conditions allowing for spontaneous movement of teeth following relief from crowding (Extractions)
- Growing child
- Extractions occured just prior to eruption of adjacent tooth
- Adjacent teeth are positioned favourably (upright)
- No occlusal interferences
90
Aetiology of spacing
- Tooth missing in a well developed arch due to hypodontia, premature loss, displacement
- Microdontia is a well developed arch
- Midline diastema
- Dentoalveolar disproportion (rare)
91
Treatment of spacing
- Orthodontic space closure
| - Redistribute spacing posteriorly and restore with bridges
92
Where is the labial frenum attached in infancy
To the crest of the alveolar ridge in the midline between the central incisors
93
What happens to the labial frenal attachment with dentoalveolar growth
Attachment becomes higher with no influence on tooth position
94
How do diastemas close in children
Eruption of canines as the attachment migrates labially to the attached mucosa
95
What will indicate frenal aetiology of a midline diastema
- Blanching of incisive papilla if tension applied to frenum
- Radiograph showing V shaped notch at the crest in the alveolar bone
96
Tx options for midline diastema
- Wait for canines to erupt
- Accept diastema
- Fixed appliance +/- frenectomy and permanent retention
97
Why does late lower incisor crowding occur
Intercanine width increases up until 12-13 and then starts to decrease gradually throughout adulthood thus incr any pre-existing labial crowding or producing new crowding
98
Factors causing tertiary crowding
- Forward growth of the mandible
- Maturation of soft tissues
- Mesial migration of posterior teeth due to interseptal fibres
- Presence of erupting 8s pushing teeth anteriorly
- 8s preventing anterior pressure being dissipated distally around the arch
