Ortho Flashcards
1
Q
Define extra-oral traction
A
Extra-oral traction is a means of using forces transmitted via safety release spring pull mechanism from an area of the head or neck to move teeth
2
Q
What are the 3 basic types of retraction headgear?
A
- Low (cervical) pull / neckstrap
- Straight (combination) pull / headcap
- High pull / headcap
3
Q
What are the uses of extra-oral traction in Class II cases (3 things)?
A
- Anchorage reinforcement
- Distal movement of upper buccal segments (molar distalisation)
- Distal movement of upper arch
4
Q
What form of extra-oral traction is used in Class III cases?
A
Reverse headgear (protraction facemask)
5
Q
What form of extra-oral traction is used in Class II cases?
A
Retraction headgear
6
Q
What are the components of an extra-oral appliance?
A
- Extra-oral unit (provides the anchorage for the extra-oral force on a form of headcap, neckpad/strap or chin cup or a facemask)
- Force delivery system (spring-loaded device or heavy-force extra-oral elastic)
- Intermediate/connecting component (transmits the force to the teeth and underlying skeleton and connects the extra-oral and intra-oral components)
- Intra-oral component (the only headgear appliance that has no intra-oral component is the chin-cup appliance)
7
Q
How does low-pull traction work?
A
- Mainly for the correction of low angle Class II malocclusion by restraining the forward growth of the maxilla
- Believed to have a reciprocal effect on the mandible as well as extrusion of maxillary molars
- This latter effect results in a clockwise mandibular rotation, thus cervical headgear is indicated mainly for growing children with a deep OB
8
Q
How does high-pull traction work?
A
- Produces forces that pass apically through the centre of resistance of the maxillary teeth producing intrusive forces to the molars, which can therefore help the correction of an AOB
- Orthopaedic effects on the maxilla by restraining its vertical growth
9
Q
How does facemask therapy work?
A
- Correction of a Class III malocclusion through forward movement of the maxilla
- In addition to skeletal changes, reverse headgear can result in dental compensation to assist with the correction of a reverse OJ or Class III malocclusion
10
Q
How to fit a patient with retraction headgear
A
- Select correct facebow size (inner bow - 1.13 mm, outer bow - 1.45 mm for maximum rigidity)
- Facebow set parallel to the occlusal plane with slight expansion
11
Q
How to fit a patient with protraction headgear
A
Cams adjusted using the Allen key until they are 15 degrees below the occlusal plane
12
Q
How is the patient’s use of the headgear monitored? (4 things)
A
- Ask the pt/parent about compliance, using compliance charts
- Assess the ability of the pt to insert/remove the appliance
- Check for physical signs of wear and tear
- Identify positive tooth movement in comparison with pre-treatment study models/cephalometry and detecting molar mobility
13
Q
List the potential iatrogenic effects of headgear (5 things)
A
- Pain due to heavy force levels
- Increased risk of root resorption
- Trauma to the face and eye
- Nickel allergy (contact dermatitis - type IV delayed hypersensitivity)
- Latex allergy
14
Q
What safety mechanisms are in place in retraction headgear to reduce the risk of ocular injury? (3 things)
A
- Safety release mechanisms where the headgear is designed to ‘break away’ when excessive force is applied
- Safety facebows e.g. locking mechanisms and recurved reverse entry inner bows
- Additional safety mechanics e.g. blunt ends, locating elastics
15
Q
What advice is given to the pt/parent for headgear use? (4 points)
A
- Avoid wearing whilst playing sports
- Stop the use of the headgear and contact the orthodontist immediately if the headgear becomes detached during sleep
- Any ocular injuries occurring as a result of the headgear should be treated as a medical emergency
- Patients to bring headgear to each appointment and report any problem to their orthodontist
16
Q
What is a functional appliance?
A
• A removable or fixed appliance that uses the forces of the muscles of mastication, fascia and the periodontium to alter skeletal and dental relationships
- Designed mainly to correct Class II malocclusion
17
Q
How does a functional appliance work? (5 points)
A
- They all work by posturing the lower jaw forward, the stretched musculature and soft tissues creating a force, which is transmitted to the dentition
- Much of the effect is dentoalveolar (tipping maxillary teeth distally, mandibular teeth mesially)
- The soft tissue environment is changed
- A new occlusal relationship is established and the OJ is reduced
- Creation of an inter-maxillary force
18
Q
List some removable functional appliances (6)
A
- Andresen activator
- Teuscher appliance
- Bionator
- Bass or Dynamax
- Function regulators
- Twin Block
19
Q
What is the most well-known and popular fixed functional appliance?
A
Herbst appliance
20
Q
What is the advantage of the Bionator over the original Andresen activator?
A
Reduced bulk of the appliance making it easier to wear
21
Q
What is special about the design of a function regulator?
A
- Deliberately designed to have minimal tooth contact
- Buccal shields and anterior lip pads incorporated to relieve cheek and lip pressure and disrupt any abnormal perioral muscular activity
22
Q
Why is the Twin Block so popular?
A
- Robust and well-tolerated
- Can be worn all the time (including whilst eating)
23
Q
Describe the design of the Twin Block appliance
A
- Upper and lower removable appliances (cribs on 4s and 6s, labial bow - optional)
- Incisor capping (for retention)
- Bite blocks composed of bite ramps set at about 70 degrees
- When occluding, the lower block bites in front of the upper to posture the mandible forwards
24
Q
Describe the design of the Herbst appliance
A
Consists of separate superstructures cemented to the mandibular and maxillary dentition, and constructed from either ortho bands or Co-Cr cap splints connected by telescopic pistons that provide the protrusive force to the mandible
25
What is the effect of functional appliances on the growth of the jaws?
Short-term influence ONLY (favourable growth changes eventually lost)
26
What is the ideal timing of treatment with a functional appliance?
- When the child is entering their adolescent growth spurt
- Male: 14 yrs (+/- 2)
- Female: 12 yrs (+/- 2)
- This is typically in the late mixed/early permanent dentition
27
What are the indications for earlier referral for functional appliance therapy and what does the pt/parent need to understand as a consequence of this?
- Bullying (psychosocial impact)
- Increased risk of dentoalveolar trauma
- Extended period of retention will be required to allow the permanent dentition to establish itself before fixed appliance therapy (therefore, overall treatment time is longer)
28
How is the patient's use of the functional appliance monitored? (5 things)
- Measure the OJ (reduction over time)
- Monitor the buccal segment relationship (Class II --> Class I or even Class III)
- Speech adapted back to normal
- Evidence of general wear and tear
- Lateral open bite produced within a few weeks full-time wear with a Twin Block
29
What are the indications that a functional appliance is not being worn by the pt? (3 things)
- No reduction in OJ or correction of buccal segment relationship
- No improvement in speech
- Repeated breakages as the appliance is being removed too frequently
30
Why is a second phase of treatment with fixed appliances required post functional appliance? (2 things)
- Relieve crowding
| - Consolidation and detailing of the corrected occlusion
31
What are some of the limitations of functional appliances? (4 things)
- Major issue = compliance (removable)
- Fixed functional appliances: more prone to breakage, more expensive
- Increases LFH (not ideal for use in pts with increased LFH - e.g. reduced OB, AOB)
- Dentoalveolar effects (proclining lower incisors is inherently unstable)
32
Which functional appliances may be used to treat Class III pts?
- Reverse twin block
| - Frankel III
33
What is meant by environmental influences on occlusion?
• Environmental influence is a loose term used to describe a cause of malocclusion which is neither pathological nor genetic in origin
- It encompasses the influence of diet, behaviour and habits
34
What is meant by the zone of soft tissue balance?
• The soft tissue environment is thought to produce an equilibrium in which the various opposing forces are balanced to produce zero resultant force
35
What are the 4 forces as classified by Proffit acting on the teeth?
- Intrinsic (from the tongue and lips)
- Extrinsic (e.g. digit sucking habits and ortho appliances)
- Forces from dental occlusion
- Forces from the periodontal membrane
36
What is tooth movement dependent on?
- Level of force
- Duration of force
- Direction of force
- Crown:root ratio
- Root SA
37
Which is more influential in the aetiology of malocclusion?
- Force magnitude
- Force duration
Force duration
38
How much does the lower lip usually cover the upper incisors?
3-6 mm
39
What can be a potential consequence of a large tongue on the lower incisors?
Proclination
40
What is the relationship between biting force and vertical face height?
- Individuals with a short vertical face height have greater biting forces than long-faced individuals
- Occlusal force is a RESULT of vertical facial form, not a cause
41
What abnormal lip activity may Class II div 2 patients present with?
- Thin, strap-like, hypertonic lips
| - High lower lip line
42
What is the primary determinant of the posture of the jaws and tongue?
Respiratory needs
43
What effect does mouth breathing have on the head, jaws and tongue?
- Head tips back
- Lowering of the mandible
- Lowering of the tongue
Hence, increased LFH
44
List possible causes of chronic nasal obstruction
- Enlarged adenoids
| - Common cold
45
What abnormal lip activity may be seen in Class II div 1 patients?
- Lower lip trap
| - Short upper lip (--> lip incompetence)
46
What role do soft tissues play in Class III patients?
Forces from the tongue, lips and cheeks promote formation of an anterior oral seal for swallowing and in so doing encourage dentoalveolar compensation by retroclining the LLS (soft tissues improve the malocclusion)
47
Which ethnic group is bimaxillary proclination commonly seen in?
Afro-Caribbean patients
48
Describe the lip form in patients with bimaxillary proclination
Full, flaccid, everted, hypotonic
49
What is the effect of soft tissue scarring post surgical repair of cleft lip/palate?
- Facial growth is inhibited
- Anterior and vertical growth of the maxilla is inhibited --> retrusive maxilla with a reverse OJ, narrow maxillary arch, associated crossbites and compensatory increased vertical mandibular growth
50
What is the role of the periodontal membrane in maintaining tooth position?
Forces within the periodontal membrane offset the imbalance in forces between the lips, cheek and tongue during function
51
What is the force duration threshold in humans?
6 hours
52
How do masticatory forces influence the jaws?
a) Shape/morphology
b) Bone density
c) Both
b) Bone density
53
Do digit-sucking habits during the primary dentition years have any long-term effect?
No
54
What are the effects of a prolonged digit-sucking habit persisting into the mixed dentition stage?
- Proclined upper incisors
- Retroclined lower incisors
- Reduced OB (or AOB - usually asymmetric)
- Unilateral posterior crossbite with displacement
- Narrowing of the upper arch (V shape)
55
How do patients with incompetent lips create an anterior oral seal?
- Increased mentalis activity (dimpling of chin visible)
- Posturing mandible forwards
- Tongue is placed between the anterior teeth (adaptive tongue thrust)
- Lower lip to palate
56
What is the malocclusion most often associated with mouth breathing called?
"Skeletal open bite" or "long face syndrome"
57
What are the landmarks for measuring upper lip length?
Subnasale to end of upper lip
58
What is the typical length of the upper lip?
20-22 mm
59
During smiling, how much clinical crown height should be visible?
Males - full crown height
| Females - full crown height + 1-2 mm attached gingiva
60
Where should the lips be in relation to Ricketts E line?
On or just ahead of it
61
Define lip competence
The lips are long enough to meet at rest with minimal muscular effort
62
What is important to achieve stability post correction of Class II div 1?
Lower lip covering incisal third of upper incisors
63
What may be the consequence of a persistently low fraenal attachment?
Midline diastema
64
What may be seen radiographically to indicate a persistently low fraenal attachment?
V-shaped notch (indicates insertion of the fibres of the fraenum into the bone)
65
Clinically, how can we test whether the fraenal attachment is low?
Blanching test (pull on the upper lip and look for blanching either labially or palatally)
66
What are the two different forms of habit cessation advice? Give examples of each
1. Physical
- Stop and grow (bitter tasting, non-toxic. Applied to nails AND skin. Needs to be reapplied after handwashing), thick fabric plasters
2. Non-physical
- Verbal advice/explanation, reward/motivation (e.g. star chart)
67
Malocclusion occurs as a result of...
- Genetically determined factors
- Environmental factors
- Combination of both
68
What is the concept of a 'normal' occlusion?
Normal-minor deviations from the ideal that do not constitute aesthetic or functional problems
69
What is the concept of a malocclusion?
An appreciable deviation from the ideal occlusion considered functionally or aesthetically unsatisfactory
70
What is the concept of an 'ideal' occlusion based on?
Andrews six keys:
1. Correct molar relationship
2. Correct crown angulation
3. Correct crown inclination
4. No rotations
5. Tight contacts
6. Flat occlusal plane
71
When does calcification of deciduous teeth begin?
4-6 months in utero
72
When is deciduous root formation complete?
12-18 months after eruption
73
What is the ideal spacing between the deciduous lower incisors for alignment of the permanent incisors?
> 6 mm spacing (Leighton 1971)
74
What is the ideal deciduous dentition occlusion?
1. Good incisor occlusion
2. Spacing between incisors
3. End to end E relationship
75
What is the consequence of a lack of spacing in between deciduous incisors?
Crowding of the permanent incisors
76
When is permanent root formation complete?
2-3 years after eruption
77
At what stage is a midline diastema a normal occurrence?
Early mixed dentition
78
In order to accommodate the premolars, how much leeway space is available in:
a) the lower arch?
b) the upper arch?
a) 2.5 mm
| b) 1.5 mm
79
How is a Class I molar relationship achieved from an end to end E relationship?
Lower 6 moves 3.5 mm relative to upper 6
1. Leeway space
2. Differential growth of lower jaw
80
At what age is eruption of the upper 3 considered to be delayed?
13 yrs
81
What is considered the threshold time for an asymmetry in eruption?
6 months
82
What causes late lower incisor crowding?
Multifactorial, but mainly due to late growth changes occurring in the mandible during the late teens
83
What is the overall change in arch length?
Decrease of 1-2 mm
84
What is the overall change in arch width?
Maxilla: 2-3 mm increase
Mandible: 2.5 mm increase
85
What is orthodontics?
- The study of growth of the craniofacial complex
- The development of occlusion
- The prevention and correction of occlusal anomalies or malocclusion
86
Name the planes of space that the face is examined in
1. AP
2. Vertical
3. Transverse
87
What does BSI stand for?
British Standards Institution
88
What system is incisor relationship classified in accordance with?
BSI
89
What is the BSI definition of a Class I incisor relationship?
The lower incisor edges occlude with or lie immediately below the cingulum plateaux of the upper central incisors
90
What is the BSI definition of a Class II div 1 incisor relationship?
The lower incisor edges lie posterior to the cingulum plateaux of the upper incisors with the upper central incisors proclined or of average inclination
91
What is the BSI definition of a Class II div 2 incisor relationship?
The lower incisors lie posterior to the cingulum plateaux of the upper incisors with the upper central incisors retroclined
92
What is the BSI definition of a Class III incisor relationship?
The lower incisors lie anterior to the cingulum plateaux of the upper incisors
93
What system is molar relationship classified in accordance with?
Angle's classification
94
Describe Angle's Class I molar relationship
The mesiobuccal cusp of the upper first permanent molar occludes with the anterior buccal groove of the lower first permanent molar
95
Describe Angle's Class II molar relationship
The distobuccal cusp of the upper first permanent molar occludes with the anterior buccal groove of the lower first permanent molar
96
Describe Angle's Class III molar relationship
The mesiobuccal cusp of the first permanent molar occludes behind the anterior buccal groove of the lower first permanent molar
97
Name the 2 most commonly used cephalometric analyses and explain how they differ from each other
Eastman - maxilla and mandible are related to each other using the cranial base (S-N) as a reference plane
Wits - functional occlusal plane (FOP) used as a reference plane
98
Name factors which are largely genetically determined (3 things)
1. Dentoalveolar (size, shape and number of teeth)
2. Skeletal pattern
3. Soft tissues (morphology)
99
Name 2 environmental factors
1. Habits (e.g. digit sucking)
| 2. Pathology
100
What is an increase vertical dimension associated with?
AOB and incomplete OB
101
What is a decreased vertical dimension associated with?
A deep OB
102
How can a transverse discrepancy in the skeletal pattern manifest itself dentally?
As a crossbite
103
What discrepancy may a wide maxilla/narrow mandible result in?
Lingual buccal crossbite (AKA scissor bite)
104
What is a lower lip trap?
The lower lip at rest is positioned behind the upper incisors, causing them to procline and increase the OJ resulting in a Class II div 1 malocclusion
105
What effect can a forward resting position of the tongue have on the dentition?
AOB
106
What are the typical features of adenoid facies? (4 things)
- Increased vertical dimension
- Narrow maxilla, posterior crossbites
- Reduced OB
- Narrow nose
107
What is the definition of a fraenum
A small fold of tissue that secures or restricts the motion of a mobile organ in the body
108
Define gemination
A phenomenon in which two teeth appear to have developed from one. Caused by incomplete division of a single tooth bud resulting in a bifid crown
109
Define twinning
Twinning is referred to the development of two separate teeth that arose from the complete separation of one tooth bud
110
Define fusion
Union of two adjacent teeth at the crown level (enamel and dentine), causing the formation of a tooth with an enlarged clinical crown
111
Define concrescence
The cementum overlying the roots of at least two teeth join together
112
What is dens invaginatus ("dens in dente") and which tooth is most commonly affected by this malformation?
Infolding of dental epithelium during tooth development i.e. infolding of enamel into dentine. The condition is present in 2 forms - coronal and radicular.
Maxillary lateral incisor
113
What are the potential complications of dens in dente?
- The space between the original tooth and the growth = susceptible tooth surface --> plaque stagnation site --> increased caries risk
- RCT problematic (complex anatomy of the pulp)
114
What is dens evaginatus (talon cusp)?
Which tooth is most likely to be affected?
Presence of an extra (accessory) cusp arising from occlusal or lingual/palatal surfaces
Premolars
115
What is the congenital absence of all teeth referred to as?
Anodontia
116
What is the developmental absence of one or more teeth referred to as?
Hypodontia
117
What is the incidence of missing upper laterals?
2%
118
What constitutes severe hypodontia?
> 6 teeth missing
119
What is a supplemental tooth?
Duplication of a tooth in the normal series (i.e. an "extra copy") characterised by the same form and function of the adjacent tooth with no anatomical differences
120
What is a midline supernumerary referred to as?
Mesiodens
121
List the various types of supernumerary teeth (5)
- Supplemental
- Tuberculate (barrel shaped)
- Conical (peg shaped)
- Compound odontome (multiple small tooth-like forms)
- Complex odontome (a disorganised mass of dental tissue)
122
What local factors may cause failure of eruption? (5 things)
- Retained primary tooth
- Abnormal crypt position
- Missing teeth
- Obstruction e.g. supernumerary
- Dilaceration (trauma)
123
What is a balancing extraction and why is it performed?
Removal of the same tooth on the opposite side of the same arch to help minimise centreline shift
124
What is a compensating extraction and why is it performed?
Removal of the same tooth from the same side in the opposing arch to help minimise occlusal interference (e.g. prevent overeruption)
125
Disturbed eruption of which primary teeth may have a negative impact on centrelines?
C and D
126
What does the term tooth transposition refer to?
An interchange in the position of two permanent adjacent teeth located at the same quadrant in the dental arch
127
What is the difference between a true/complete transposition vs. a pseudo/incomplete transposition?
True/complete - total exchange in position of adjacent teeth (both crown and root)
Pseudo/incomplete - only the crowns of the adjacent teeth are transposed while the roots remain in normal position
128
When is space maintenance required and why?
When:
- Unerupted/delayed eruption
- Traumatic loss
Why:
- Maintain concentric dental centrelines
- Maintain space
- Better occlusion
129
What types of space maintainers exist?
- Band loop - single tooth
- Lingual/palatal arch
- URA
130
What are the main categories of orthodontic appliances and how do they differ from each other?
1. Passive (e.g. space maintainers, retainers)
- Maintain the position of teeth
2. Active
- Bring about tooth movement
- Incorporate active forces within the appliance
131
How do removable orthodontic appliances bring about tooth movement?
Forces are applied to the teeth by means of springs, screws and other mechanical components
132
What are the advantages of removable appliances?
- Cheap
- Readily cleansable
- Difficult to apply excessive forces
- Construction mainly in lab, therefore little chairside time required
- Easily adjustable
- Less risk of iatrogenic damage (e.g. root resorption) than with fixed appliances
- Can incorporate posterior bite capping
133
What are the disadvantages of removable appliances?
- Only limited type of tooth movements possible (tilting/tipping), therefore only suitable for correction of simple malocclusions
- Anchorage may be difficult
- Retention is more difficult
- Requires cooperation and some skill from the patient
- Less successful in the lower arch due to poor tolerance
- Speech initially affected
134
What are the 4 components of a removable appliance?
1. Active component
- Means by which forces are applied to the teeth to bring the required movement (e.g. springs, bows, screws)
2. Retention
- Means by which appliances resist displacement (clasps/cribs, bows)
3. Anchorage
- Site from which the forces are applied (teeth, baseplate; can reinforce with EOT)
4. Baseplate/connecting framework
- Supports wire components
- Contributes to anchorage
- Prevents unwanted drift of teeth
- Transmits forces from active component
- May be extended to form bite planes
135
How is posterior retention achieved in removable appliances?
```
Adams clasps (typically on first permanent molars. For additional retention - premolars, deciduous molars)
- Arrowheads engage in MB and DB undercuts
```
136
What are Adams clasps constructed from and how are they constructed?
0.7 mm hard stainless steel wire
| Easily constructed with Adams universal pliers
137
How is anterior retention achieved in removable appliances?
Southend clasp (engages undercuts of upper centrals)
138
What is a Southend clasp constructed from?
0.7 mm wire
139
Asides from a Southend clasp, how else may anterior retention be achieved and when is this form of retention useful?
Fitted labial bow
| Only effective if incisors are proclined
140
Define anchorage
Resistance to unwanted tooth movement
141
What provides anchorage?
Intraoral:
- Other teeth in the arch
- Palate
Extraoral:
- Head or neck
142
What does the anchorage value of teeth depend on?
1. Surface area of roots (molars = best anchorage; lower incisors = least anchorage)
2. Type of tooth movement permitted - teeth that can only move bodily give greater resistance than those free to tip
143
What are the 3 types of anchorage?
1. Simple anchorage
- Using a large tooth as anchorage to move a small tooth
2. Compound anchorage
- Using a group of teeth as anchorage to move a single tooth
3. Reciprocal anchorage
- Teeth with equal root surface area moved in equal and opposite/same direction
- e.g. moving central incisors together; bilateral expansion
144
What can an anterior bite plate help to correct?
Reduction of a deep OB
145
What can posterior capping help to achieve?
Disengages the bite (i.e. props the bite open) to aid in correction of:
- A buccal crossbite
- AOB
146
How can a spring be designed in order to keep force magnitude low?
Increase length (by incorporating a coil), reduce radius (i.e. long, thin wire)
147
State the wire widths for:
a) Palatal spring
b) Buccal spring
a) 0.5 mm
| b) 0.7 mm
148
What is the rate of tooth movement achievable with springs and how often do springs need to be adjusted?
1-2 mm per month
| Springs need adjusting once a month
149
List the types of palatal springs and their uses
1. Single cantilever spring (finger spring)
- To move teeth in line of arch
2. Double cantilever spring (Z spring)
- Positioned perpendicular to palatal surface
- Proclines incisors
- Useful in correction of instanding incisors/anterior crossbite
3. T spring
- Moves premolars buccally
- Useful in correction of instanding premolars
4. Coffin spring
- Heavy wire (1.25 mm)
- Transverse upper arch expansion
150
What is the use of a buccal canine retractor?
Retraction of a buccally placed canine
