Orthodontics Flashcards
1
Q
What are the indications of fixed appliances?
A
3-dimensional tooth movements
Space maintainer
Arch expansion
2
Q
What are the indications for removable appliances?
A
Space maintenance
Retainers
To reduce deep overbite
Bite opening
Expansion
Adjunct to fixed appliances
Functional appliances
Other simple tooth movements
Aligners.
3
Q
How do fixed appliances work?
A
Extrusion
Intrusion
Rotational
Tipping
Bodily movement
Torquing
Force applied by FAs to achieve tooth movement = force couple.
4
Q
How do removable appliances work?
A
A force is applied via the active component which achieves a tipping movement around the fulcrum axis.
5
Q
What are the limitations of fixed appliances?
A
6
Q
What are the limitations of removable appliances?
A
- Only tipping - main limitation.
- Lower arch treatment
- Cannot use inter-arch elastics
- Vertical movements, precision movements, rotations and multiple teeth movements can’t be achieved easily with RA, and so fixed appliances are used.
- Removable - relies on pt compliance
- Require construction (cost)
7
Q
What are the phases of FA treatment?
A
- Levelling, derotation and alignment
- Overbite reduction
- Overjet reduction
- Space closure
- Finishing procedures
8
Q
What are the basic principles of archwire selection?
A
a. NiTi wires provide less force than SS wires (for a comparable dimension)
b. SS wires are more rigid
c. SS wires have less friction allowing teeth (brackets) to slide more easily
d. NiTi wires have shape memory – they can be deformed when trying in the wire and will pull the teeth out to the original shape of the archwire.
e. SS wires can be formed (able to add bends)
f. You cannot torque with round wires
9
Q
How do FA achieve root torque, derotation & bodily movement?
A
Torque - 3rd order in preadjusted brackets. Torque is the force couple generated between the archwire and the bracket. Incorporated in the bracket by the angle the bracket base makes with the bracket slot when viewed form the side. Need rectangular or square archwire.
Derotation - Thin and flexible wire with high elastic limit applied light forces onto teeth.
Bodily movement
10
Q
What are different types of fixed appliances?
A
x
11
Q
What is normal occlusion and malocclusion?
A
Normal occlusion = Minor but acceptable differences from ideal occlusion.
Malocclusion = Tooth position or jaw position outside normal range.
12
Q
What are some examples of malocclusions?
A
- Crowding
- Spaced
- Increased overjet
- Reverse overjet
- Deep overbite
- Anterior open bite
13
Q
What is the aetiology of malocclusion? General (4) and local factors (3)?
A
General
i. Skeletal pattern = position of roots.
ii. Soft tissues = position of crowns
iii. Jaw size
iv. Tooth size = crowding/spacing.
Local
i. Habits
ii. Anomalies = missing/extra teeth
iii. Fraenum
14
Q
Why is there a need for tx of malocclusion? (3)
A
- Dental health (e.g. crowding can make caries and restorations more difficult, crooked teeth prone to perio, increased overjet predisposes to tooth trauma)
- Function e.g. difficulty eating.
- Aesthetics = low self esteem, quality of life.
15
Q
What are 3 types of appliances used in orthodontics?
A
- Removable
- Fixed
- Functional
16
Q
DEFINITION: Removable appliance?
A
A device placed within the mouth to correct or alleviate malocclusion and designed to be removed and replaced by the patient.
17
Q
How do removable appliances work? (4)
A
a. Actively 1) Tips teeth and 2) moves blocks of teeth.
b. Passively 3) enables differential tooth eruption and 4) space maintenance.
18
Q
How do removable appliances tip teeth?
A
A force is applied via the active component which achieves a tipping movement around the fulcrum axis.
19
Q
What planes can the tipping of roots occur in removable orthodontic appliances?
A
a. mesio-distal in buccal segments
b. mesio-distal in labial segments
c. labio-lingual in class 2
d. labio-lingual in class 3
20
Q
What 4 factors do you need to consider when choosing to use a removable appliance?
A
A. Angulation/inclination of tooth.
B. Distance to move
C. Skeletal pattern
D. Overbite.
21
Q
Why are RA not commonly used in lower arch? (3)
A
- Less undercut for retention
- Less buccal sulcus for springs
- Tongue severely limits lingual space for springs.
22
Q
What is the role of space maintenance?
A
When there is early extraction or exfoliation of teeth in primary dentition, an appliance may be placed to prevent teeth from naturally drifting into the space left which would prevent the eruption of its permanent replacement.
23
Q
Name 2 main examples of removable retainers.
A
Hawley retainer.
Vacuum formed retainers (VFRs).
24
Q
What are the benefits of removable retainers? (6)
A
- All the teeth can be retained with the single appliance.
- Partial withdrawal possible.
- Less dental health hazard - no sharp wire present to traumatise tissues.
- Oral hygiene.
- Missing teeth can be replaced.
- Responsibility of the patient.
25
What are the disadvantages of removable retainers?
There is a release risk of both rotations and anterior diastemas if not worn everyday.
May not allow the vertical tooth position to settle.
Needs to be worn but this is down to the patient only so may have poor compliance.
26
How do bite planes in removable orthodontics work to reduce a deep overbite?
Passive eruption.
Enable differential tooth movement.
The patient bites on the front built up bite plane meaning the back teeth are no longer in contact.
Therefore due to passive eruption, the posterior teeth move up to become in occlusion once more which eliminates the overbite.
27
How can removable appliances be used to expand the arch to remove posterior crossbites?
Places acrylic on the posterior teeth to raise them above the opposing arch. This removes interference from opposing arch.
Then overtime active component of appliance is turned to slowly expand the arch to rectify the crossbite.
28
What are the 2 functions of functional appliances?
They reduce increased overjets and correct molar relationships.
29
What are the advantages of removable appliances?
Removable
Easy to clean
Adjunct to anchorage of teeth you want to keep stationary.
Simple/quick treatment (sometimes)
30
How do you check if a pt is using their removable appliance?
Good speech
Palatal gingivitis
Wear facets on acrylic
Springs passive, and no longer active as they have conducted their role.
Confident removal and insertion.
31
Why do we use removable appliances?
OH issues
When limited tx is appropriate
Skeletal modification (functionals)
Improve efficiency e.g. anchorage
Preference - clinican (& pt)
Retention
Unable to use other types of appliances e.g. repeat MRI scans
Making our job easier.
32
What are the 4 main components of removable appliances? Acronym?
Active component --> this causes the orthodontic movement but also displaces the appliance so need retention to keep it in.
Retentive component --> keeps denture in mouth
Anchorage --> Keeps teeth you want to maintain in same stationary space
Base plate --> Joins all active, retentive and anchorage components together.
ARAB.
33
What are the 2 forms of active component in removable appliances?
Springs = Z springs (canines). T springs (incisors)
Screws --> a. unilateral or bilateral distal orthodontic movement. b. arch expansion. c. anterior cross bite correction.
34
DEFINITION: fixed appliance (FA)?
An orthodontic appliance which is fixed to the teeth. IT is a method of moving teeth using a combination of brackets, arch wires and auxiliaries to push or pull the teeth into chosen positions.
35
What are the actions of fixed appliances?
Extrusion
Intrusion
Rotational
Tipping
Bodily movement
Torquing
36
What is the name of the force applied by FAs to achieve tooth movement?
Force couple
37
What are force couples?
Equal forces applied in opposite directions creates a force couple.
The forces are applied through interactions between FA components: arch wires, brackets, auxiliaries.
38
What different materials can brackets be made from?
Stainless steel, ceramic and plastic.
SS - lower friction, easy to remove and keep clean.
Ceramic - tooth wear problem, higher resistance, bracket # on debond.
39
Name the pre-adjusted bracket prescriptions.
1st order = in-out
2nd order = tip
3rd order = torque
These built-in factors (prescriptions) make brackets diffferant for each tooth and allow clinician to place straight piece of wire.
40
What is first order in preadjusted brackets?
In-out control.
Variation in thickness of bracket base for different teeth. Takes into abbount bucco-lingual thickenss.
41
What is second order in preadjusted brackets?
Tooth tip
Controlled by the angulation of the archwire slot. Takes into account the mesio-distal angulation of each tooth crown relative to occlusal plane. Greatest for canines.
42
What is third order in preadjusted brackets?
Torque
Tooth inclination control or "torque" is incorporated into bracket by angle the bracket base makes with the bracket slot when viewed from the side.
The torque is the force couple generated between the archwire and the bracket.
43
What type of wires do you need to use to apply torque?
Rectangular or square wires.
Cannot torque with round wire.
44
Where are permanent identification markers?
Distal-gingival position of the bracket.
45
Where do brackets need to be placed?
LACC = on the Long Axis and in the middle of the Clinical Crown.
Must be fully seated so minimum glue thickness.
46
How do archwires stay in?
Ligated into the bracket with coloured rings (modules/o-rings) or metal ties (ligatures).
Some brackets are self ligating - door mechanism to hold the wire in place.
47
What are properties of archwires influenced by?
Different material - stainless steel, nickel titanium, TMA - changes features such as Young's Modulus (Modulus of Elasticity, E).
Different cross sectional shapes - round, square, rectangular.
Different cross sectional sizes - 0012" to 0.021" x 0.0025".
48
What different materials can archwires be made from?
Stainless steel --> more rigid. Less friction allowing teeth (brackets) to slide move easily. Can be formed (able to add bends)
Nickel titanium --> provide less force than SS. Have shape memory so can be deformed when placing wire and pull the teeth out to original shape of the archwire.
TMA.
49
Stages of fixed appliance tx?
1. Levelling, derotation and alignment
2. Overbite reduction
3. Overjet reduction
4. Space closure
5. Finishing procedures.
These stages use different archwires and auxiliaries to achieve movements.
50
What instrument is used to place the archwire?
Matheiu pliers.
51
What instrument is used to place o-rings?
mosquito forceps
52
What are Weingart pliers used for?
Placing and removing archwires.
53
DEFINITION: class I incisor relationship
The tip of the lower central incisor occludes with (or projects onto) the middle third (cingulum plateau) of the upper central incisor.
54
What is the aetiology of Class I malocclusions
Usually dento-alveolar.
55
What are the problems that may require treatment in class I malocclusion?
Crowding (most common)
Spacing
Open bites (anterior and posterior)
Bimaxillary proclination (Sk3)
Crossbite (uni or bilateral)
56
What percentage of people have each type of incisor relationship
Class 1 = 60%
Class 2 div 1 = 20-25%
Class 2 div 2 = 10-15%
Class 3 = 5-10%
57
How may incisor inclinations vary in class 1 occlusions and why?
Sk 1 = normal incisal angles.
Mild Sk 2 = retrocline U or proclined L or both.
Mild Sk 3 = proclined U or retroclined L or both.
Occurs due to dento-alveolar compensation.
58
What are the common skeletal patterns in class 1s? A/P, Vertical, Lateral.
A/P = usually Sk 1 but not always due to dento-alveolar compensation.
Vertical = mostly average face height and proportions.
Lateral = Usually symmetrical
59
What is dento-alveolar compensation and why does this happen?
A mechanism in which the soft tissue produce a more class 1 relationship when the skeletal class is 2/3.
The lips and tongue tend to guide the erupting teeth into more ideal positions than the skeletal class would suggest (class 1).
60
What are 2 possible aetiologies of facial asymmetry? What intra oral signs are there of facial asymmetry?
1. Biological variation - no one is symmetrical.
2. Pathological - e.g. condylar hyperplasia.
Signs: centre line discrepancies or posterior cross-bites +/- mandibular displacements.
61
What is the classification of crowding?
Mild = 0-4mm
Moderate = 4-8mm (distal movement or extract premolars)
Severe = 8+mm (extract premolars)
62
What is the cause of spacing in Class 1 malocclusions? How can you treat?
Too little tooth tissue for arch size (either small teeth normal jaws or normal teeth large jaws).
Tx: i. close space
ii. Redistribute space
iii. Combination of both.
63
When might we not close spaces?
Might leave space to replace missing teeth e.g. implant or bridge. e.g. missing lateral.
Need to commit pt to lifelong wear of retainer otherwise space will open back up again.
64
DEFINITION: Bimaxillary proclination?
The proclination of the upper and lower labial segments.
65
What is bimaxillary proclination caused by and why is it hard to treat?
It is caused by the soft tissues - normally flaccid lips and large tongue push teeth out, and lips don't resist this.
As it is caused by the soft tissues - it is prone to relapse.
66
What are the 5 categories of local factors which can affect a class 1 malocclusion?
Variation in tooth number (hyper/hypodontia).
Variation in tooth form and size (macro/microdontia/peg shaped laterals)
Abnormalities in tooth position (ectopic teeth/transposition)
Local abnormalities of soft tissues (median diastema etc)
Local pathology (dentigerous cysts etc).
67
What is transposition? What teeth are most commonly involved?
True transposition = both roots and crowns have swapped position.
Pseudotransposition = just the crowns have swapped position.
most commonly 3s and 4s. then 5s and 6s.
68
What are the causes of median diastema?
Big labial frenum
Digit habit causing proclination and spacing.
Unerupted supernumerary
Nasopalatine duct cyst.
69
DEFINITION: anterior open bite (AOB)?
When there is no contact or vertical overlap of the lower incisors by the upper incisors whilst the mandible is in occlusion.
70
What are the 3 main causes of AOB?
1. Skeletal causes (increased lower face height) (good indicator is symmetrical)
2. Habits such as digit sucking (normally asymmetrical)
3. Soft tissue cause - tongue pushing - (this is hard to diagnose and usually the diagnosis of exclusion).
71
What are the classic clinical features of a digit sucking habit?
A. Can produce an asymmetrical AOB or reduced overbite.
B. Proclined upper incisors.
C. Retroclined lower incisors.
D. Associated with unilateral posterior cross bite with a displacement on closure an centreline discropancy.
72
What are some features of soft tissue open bites?
They are v rare but are caused by endogenous tongue thrust.
Can cause anterior or posterior open bites.
AOB is commonly symmetrical.
It is a diagnosis of exclusion.
73
What is a buccal crossbite?
When the buccal cusps of the lower teeth occlude buccally to the buccal cusps of the upper teeth.
74
What is a scissorbite?
When the buccal cusps of the lower teeth occlude lingually to the lingual cusps of the upper teeth.
75
What can cause posterior transverse occlusal issues (cross and scissor bite)? (3)
1. A narrow maxilla i.e. transverse skeletal discrepancy.
2. Digit sucking habits.
3. Local problems often related to local crowding.
76
What are 3 forms of posterior cross bites?
1. Unilateral - one side
2. Local - only one tooth affected.
3. Bilateral - both sides affected.
77
What should you always check for when a crossbite is present? Especially unilateral crossbite.
Mandibular displacement.
78
DEFINITION: mandibular displacement?
When there is a significant movement (more than 1mm) of the mandible between the first contact in RCT and final position in ICP.
79
Why might you accept a bilateral cross bite? (3)
- They are not associated with mandibular displacement.
- Usually reflect a larger lateral skeletal discrepancy.
- If treated then there is a greater risk of relapse.
80
What are 2 common forms of treatment for Class 1 malocclusions?
- Usually orthodontic management alone is possible unless severe variation in vertical and lateral norms.
- Can be treated with fixed appliances.
- Can consider extractions if more than 4mm of crowding present.
81
How common is Class 1 malocclusion?
60%
82
When would you particularly check for mandibular asymmetry?
Centre lines are off.
Cross bite.
83
DEFINITION: Class II div 1
The lip of the lower central incisors occludes (or projects) behind the middle third (cingulum plateau) of the upper central incisor (Class II)
The upper central incisors are proclined or of averages inclination (div 1) (and the overjet is increased).
84
What are the aetiological factors of Class II div 1?
Skeletal factors
Soft tissue factors
Associated habits
Dento alveolar factors.
85
What is the incidence of class II div 1?
20-25%
86
What is the skeletal pattern of class II div 1 usually? (A/P, vertical, lateral)
- A/P = usually sk Class 2 (76% class 2 (ANB > 4 degrees) - usually small mandible rather than prominent maxilla.
- Vertical - mostly average (but can also have increased and reduced face height and proportions.)
- Lateral - usually symmetrical but facial asymmetry possible.
87
What are some associated intra-oral features of facial asymmetry?
Centre-line discrepancies.
Posterior cross-bite +/- mandibular displacements.
88
What do you look for if someone has centre-line discrepancies or posterior cross-bites +/- mandibular displacements?
Facial asymmetry
89
What soft tissue factors cause Class II div 1 malocclusion?
A. Lip competence
B. Low lower lip resting height - lower lip doesn't cover upper central when upper lip gently lifted.
C. Lower 'lip trapping' --> producing dento-alveolar effect - lower lip caught behind upper incisors.
D. Tongue to lower lip to help create anterior oral seal (AOS) - tongue to lower lip seal.
E. Influences stability of treatment cases.
90
What is the usual lip morphology in Class II div 1?
Usually incompetent lips, often markedly.
- Lip competence increases from age 8 to 14.
- Patient becomes more socially aware.
Lower lip line
- Resting height of the lower lip should ideally cover incisal third 21/12 to control upper incisor position.
Upper lip matters less in terms of control of upper incisor position, but a gummy smile may be cause of aesthetic complaint.
91
What are 2 causes of incompetent lips?
Class 2 skeletal class
Increased vertical dimension - lips can't meet.
92
What are common dental features of Class II div 1?
- Commonly influenced by soft tissues and habits if present.
- Increased OJ - commonly proclined upper incisors (caused by lower lip)
- Increased OB - commonly incomplete (tongue to lower lip action to create AOS)
- Buccal segments usually Class II - full unit class 2 molar.
93
What are features of malocclusion (can occur in any class of malocclusion)?
Crowding
Spacing
Bimaxillary proclination
Local factors
Pathology
Open bites (anterior or posterior)
Posterior transverse occlusal problems (local crossbite/scissorbite, unilateral crossbite, bilateral crossbite).
94
Why treat Class II div 1?
Dental health considerations: to reduce risk of trauma to upper incisors.
Functional considerations: not a common reason, most people eat ok, unless v large OJ.
Aesthetic considerations: "teeth stick out" is most common complaint --> bullying.
95
What is the incidence of trauma to 12 yr olds with OJ > 9mm?
45% of 12 year old children with OJ >9mm had visible damage to upper incisors.
96
How much does an OJ >3mm increase injury by?
OJ >3mm twice as much risk of injury than OJ <3mm.
97
What are the treatment aims specific to Class II div 1?
Reduce overbite to normal as necessary condition of being able to reduce overjet.
Reduce overjet.
MUST REDUCE OVERBITE THAN OVERJET.
98
What are the treatment options for Class II div 1?
Accept, orthodontic only (camouflage Sk2), orthognathic.
Treatment methods - URA, functional appliance +/- fixed appliances, fixed appliances, joint orthodontic (fixed appliances) / surgical approach (orthognathic).
99
What are the clinical indications for URA to fix class II div 1?
Increased overjet due to proclined upper labial segment.
Mild sk Class 2.
(tooth tipping around fulcrum axis).
--> Be careful as may lead to class II div 2 malocclusions.
--> Cannot treat crowding, rotations - need fixed appliances.
100
When are functional appliances used?
When pt is growing.
Usually late mixed/early permanent dentition.
Better tolerated in younger pts.
Usually a removable appliance.
Most commonly used to treat Class II div 1 malocclusions.
101
How do functional appliances work?
Dentoalveolar affect - They harness forces which arise when the mandible is held in a postured position, with the forces being generated by the resultant soft tissue stretch.
They utilise forces generated by the orofacial soft tissues in order to move the teeth. - this is the dentoalveolar effect (70% affect) with the stretched tissues applying forces to the teeth which move by the usual mechanism (tipping).
Skeletal affect - a bit more growth of mandible (1mm average) and restraint of maxilla (1mm average).
Soft tissue effect - guiding bone development? Frankel soft tissue theory not generally accepted.
70% dentoalveolar, 30% skeletal, bit of soft tissue to guide bone development.
It is often a two-stage tx, with functional appliance followed by fixed appliance therapy with or without extractions.
E.g. twin block appliance.
102
What is the most common functional appliance used in the UK?
Twin block appliance.
- it is well tolerated. Two part appliance. Patients can eat in it. Various designs.
103
What malocclusions are treated with functional appliances?
Class II div 1 malocclusions, with or without crowding, on a moderate to severe Sk 2- commonest.
class II div 2 malocclusions, on a moderate to severe skeletal base - convert to class II div 1 FIRST THEN fit functional
(Class III malocclusions - rarely due to low success rate).
104
What are the dento-alveolar effects of functional appliances for the upper and lower arch?
Upper = Retraction of upper incisors (palatal tipping). Distal movement of upper buccal segment.
Lower = Proclination of lower incisors. Overbite reduction by reducing lower incisor eruption while permitting buccal segment tooth eruption. Mesial movement of lower buccal segment teeth which occurs because they move mesially as they continue to erupt.
105
When is the peak growth rate of girls and boys?
Girls 10 - 12 yrs
Boys 12 - 14 yrs
106
Name 5 examples of functional appliances.
Removable:
Twin block appliance
Bionator
Medium opening activator
Frankel (FRII)
Fixed:
Herbst (minority use)
107
How fast is an overjet reduced?
On average this should reduce by >1mm per month.
108
What might appear when using removable appliances?
Lateral open bite.
109
What are the usual indications for fixed appliances which may present?
Irregular arch alignment
Rotations
Space closure
Arch coordination
110
What are orthognathic treatment clinical indications for class II div 1?
Severe class 2 skeletal relationship (usually ANB >8)
Pt complains of a small chin
Growth MUST have ceased
111
When would a removable appliance alone be appropriate for class II div 1? (one stage treatment)
Well aligned arches - removable appliances are not good at correcting irregularity within an arch.
Class 2 molar relationship
Mild Sk 2
If teeth are irregular, two-stage tx is required.
112
DEFINITION: CLASS II DIV 2
The tip of the lower central incisors occludes (or projects) behind the middle third (cingulum plateau) of the upper central incisor (class II).
The upper central incisors are retroclined (division 2).
113
What is the incidence of Class II div 2?
10-15%
114
What is the aetiology of Class II div 2?
Skeletal factors
Soft tissue factors
Associated habits
Dento alveolar factors
115
What are the skeletal factors in Class II div 2 malocclusions?
A/P = usually Sk Class 2 - commonly mild. Mild SK 3 also possible.
Vertical = mostly reduced lower anterior face height and reduced maxillo-mandibular plane angle.
Lateral - usually symmetrical but facial asymmetry possible, broad upper arch.
Other features influenced by anterior growth rotation:
i. chin - well developed in relation to slightly retrusive mandible.
ii. angle of mandible - well developed.
116
Why is severe skeletal class II unusual for class II div 2?
It usually leads to class II div 1 because lips cannot control upper incisors.
Get lower lip trap forcing upper central and laterals forward, meaning they're proclined.
117
What can a broad maxillary base relative to mandible lead to?
Premolar scissor bite
118
What soft tissue factors play a large role in the aetiology of Class II div 2 malocclusion? (3)
1. Usually competent lips
i. well developed labiomental fold.
ii. often retrusive compared to nose and chin.
2. High lower lip resting line
i. resting height of the lower lip should ideally cover incisal third 21/12 to control upper lip position.
3. Lower lip may be described as 'strap-like' producing dento-alveolar effect.
i. this retroclines the upper incisors.
119
What inclination of Class II div 2 teeth often?
Bimaxillary retroclination because lip retroclines upper and lower incisors.
High lower lip line relative to 1/1 but not always 2/2.
120
What are common dental features of Class II div 2?
1. Decreased Overjet
i. commonly retroclines upper central incisors.
ii. upper lateral incisors may be retroclined or classically; proclined, mesially angulated and mesiolabially rotated.
2. Often increased Overbite
i. Commonly complete
ii. May be traumatic to palatal and buccal gingivae.
3. Often premolar scissor bite
4. Buccal segments commonly class II
121
What might the upper lateral incisors look like in a pt with Class II div 2 malocclusion?
Upper laterals may be retroclines or classically; prolcined, mesially angualted and mesiolabially rotated.
122
Why would we treat Class II div 2 malocclusion?
Dental health considerations - correct overbite if traumatic.
Functional considerations - may want to correct retroclined incisors to get a good occlusal fit. Traumatic overbite may need tx.
Aesthetic considerations - pt may dislike appearance of retroclined incisors. Pt may be happy with the incisor relationship but want correction of other features.
123
What are the treatment aims specific to Class II Div 2?
Reduce the overbite to normal
Correct interincisor angle
124
What are the treatment options/methods to fix Class II div 2 malocclusions?
Treatment options: Accept, Orthodontic only, Orthognathic.
Treatment methods:
> URA (rarely used alone)
> Fixed appliances
> Convert to Class II div 1 then functional appliance +/- fixed appliances.
> Joint orthodontic (fixed appliances) / surgical approach (orthognathic).
125
What do you do after overbite correction in class II div 2 malocclusion?
Reduce overbite then need retroclination as will have high I-I angle, so overbite reduction is unstable. Want 135 degree
The lower I-I angle gives an occlusal stop.
- Upper incisor torque needs a fixed appliance and rectangular wire.
- Lower incisor proclination is undertaken but is less stable and needs very good retention - because lower incisors are where they are because of soft tissue balance. So need to hold them there as will go back to where they start.
126
How do anterior bite planes work?
Enable differential tooth movement.
Lower incisors bite on plastic, unopposed teeth will continue to erupt until it comes into contact.
Posteriors will overerupt and reduce the overbite + GROWTH.
127
Are upper removable appliances used alone to correct Class II div 2?
Rarely used alone
commonly used as adjunct to other treatment.
i. Reduce OB prior to fixed appliance placement.
ii. Proclining upper labial segment prior to functional appliance treatment.
128
How are functional appliances used for Class II div 2 malocclusions? What are the 3 phases?
In growing pts, one option is to covert the incisors to class II div 1 by proclining the upper incisors and then reducing the overjet with a functional appliance.
A fixed appliance is then frequently needed to finish the case.
Phase 1 = class II div 2 incisor relationship is converted to a class II div 1 with URA or sectional FA.
- Z spring anteirorly to push incisors forward. Expansion screw to expand upper arch. Cribs for retention.
Phase 2 - Class II div 1, treated with functional appliance (e.g. twin block)
Phase 3 = once class I incisors treat with fixed appliances +/- extractions.
129
What is a core clinical indication of fixed appliances in class II div 2?
Torque control of upper incisors needed to allow correction of the inter-incisal angle.
130
What are the usual indications for fixed appliances? (4) all malocclusions
Irregular arch alignment.
Rotations
Space closure
Arch coordination
131
What can be used to treat mildly crowding class II div 2 cases?
- Headgear (EOT) extra oral traction to distalise the upper buccal segment teeth.
- URA to assist this and to reduce overbite.
- FA to complete tx.
132
What can be used to treat moderate/severe crowded class II div 2 cases?
- create space with planned extractions +/- extra oral traction.
- An upper removable appliance may be helpful to reduce overbite and make space for placment of lower fixed appliance.
133
What are core clinical indications for orthognathic treatment for class II div 2?
Commonly reduced vertical skeletal relationships.
Can be more moderate than the severe class 2 skeletal relationship.
Growth must have ceased.
--> Orthodontic alignment and decompensation of incisor inclinations prior to orthognathic surgery.
134
What factors influence the treatment option?
Age, severity of skeletal class, crowding, parental involvement, patient motivation, dental health.
135
DEFINITION: Class III incisor relationship?
The tip of the lower central incisor occludes (or projects) in front of the middle third (cingulum plateau) of the upper central incisors (class III).
136
What is the aetiology of Class III?
Skeletal factors
Soft tissue factors
Dento-alveolar factors.
Facial growth factors.
137
What is the incidence of Class III incisor relationship?
5-10%
138
What are the skeletal factors in Class III malocclusions?
A/P - usually Sk Class 3 - 76% have Sk Class 3 (ANB <2 degrees). Large mandible or small maxilla or combination of both. Shorter cranial base.
Vertical - most average but also increased and reduced face height and proportions.
Lateral - usually symmetrical but facial asymmetry possible. Often narrow upper arch and broad lower arch which can result in crossbites.
139
What is the ANB angle for Sk Class 1?
2-4 degrees
140
What is the ANB angle for Sk class 2?
>4 degrees
141
What is the ANB for Sk Class 3?
<2 degrees
142
What can cause facial asymmetry?
Biological variation - the usual situation.
Pathological e.g. condylar hyperplasia.
143
What are 2 associated intra-oral features with facial asymmetry?
Centre-line discrepancies.
Posterior cross-bite +/- mandibular displacements
(if you see on of these, go back and check for facial asymmetry).
144
What are the soft tissue factors that play a large role in Class III malocclusions?
Lip competence and form.
Tend to tip teeth to compensate for skeletal relationship producing dento-alveolar effect known as dento-alveolar compensation.
The lips and tongue tend to guide the erupting teeth into better positions than the skeletal class would suggest.
145
DEFINITION: Dento-alveolar compensation?
A mechanism through which the soft tissues produce a more Class I incisor relationship when the A-P skeletal class us Sk2 or Sk3.
146
What happens when there is dento-alveolar compensation in a skeletal class 3 case?
Proclined upper incisors
Retroclined lower incisors
Both
147
What direction and amount does facial growth occur?
Direction of growth:
-> generally downwards or forwards.
Amount:
-> on average, people grow 2mm more skeletal class 3 from age 11 to end of growth.
-> cannot predict, can only assume the average.
148
Why do we tend to treat Class III cases later rather than earier? What is an exception?
Because the older the patient, the less the remaining growth, so the smaller the uncertainty. (from age of 11, get 2mm more sk class III to end of growth).
Exception is mild sk Class 3 cases with anterior crossbite + mandibular displacement.
149
What are common dental features of class III?
Commonly influenced by soft tissues
Decreased OJ, +/- anterior crossbite - extent depends on the severity of the Sk class 3.
Dentoalveolar compensation.
Buccal segments usually Class III, may have posterior crossbite (uni- or bilateral)
150
What are the occlusal features of Class III malocclusion?
Tendency for anterior and posterior crossbites.
--- Anterior crossbite because of Class III incisors.
--- Posterior crossbite because of:
1. Narrow upper arch, broad lower arch.
2. Class 3 A-P relationship means broader parts of lower arch opposite narrower parts of upper arch.
both may be associated with mandibular displacement.
Narrow arch --> crowding
Broad lower arch --> aligned/spaced.
151
Why do we treat Class II malocclusions?
Dental health considerations: Reduce risk of wear to upper incisors and possible gingival recession associated with lower incisors.
Functional considerations: not a common reason, most people manage to eat OK, unless OJ very negative or associated with AOB.
Aesthetic considerations: Appearance of reverse OJ.
152
What are the specific treatment aims for Class III?
Increase the overjet
Increase the overbite to normal if necessary.
153
What are the treatment options/methods for Class III malocclusions?
Accept
Orthodontic only (camouflage Sk3)
Orthognathic
- Upper removable appliance
- Fixed appliance
- Joint orthodontic (fixed appliances)/surgical approach (orthognathic).
154
What treatment do you do for Class III, mild, moderate and severe?
Mild class III = procline upper incisors usually with URA.
Moderate class III = procline upper and retrocline lowers with fixed appliances using torque control.
Marked Class III (usually ANB <-1 degrees) = combined orthodontics and orthognathic jaw surgery.
155
What are the favourable features for predicting successful correction of Class III?
Mild Class 3 skeletal pattern (or class 1)
Little or no dento-alveolar compensation
Normal or increased overbite - (when grows, might lose overjet, so want an increased overbite)
Forward mandibular displacement on closure from edge to edge.
156
What are the clinical indicationss for URAs in class 3 incisor relationships?
Mild Sk class 3 cases with anterior crossbites + mandibular displacement.
Mild sk class 3
157
What do you do in cases with a forward mandibular displacement?
Treat this early because:
> it may cause damage to teeth and periosteum
> it is quick and easy to treat, so even if later growth unfavourable, little is lost.
simple interceptive treatment - classic appliance to push tooth over the bite. --> Want positive overbite and positive overjet.
158
What are the 4 principles for designing URA?
Active
Retention
Anchorage
Baseplate
159
What are the core clinical indications for orthognathic treatment in class III malocclusions?
a. Severe class 3 skeletal relationship (usually ANB <-1 degree)
b. Pt complains of a large chin
c. Growth must have ceased.
160
What are the orthodontic aims of surgery in class 3?
Decompensate incisors prior to surgery.
Coordinate the arches.
161
What are different surgeries for Class III?
Small maxilla needs advancement --> Le Fort 1 osteomy
Large mandible needs set-back --> bilateral sagittal split
Frequently both jaws require surgery.
162
What are the common treatments of Class III malocclusions?
Orthodontic management alone is possible unless significant variation from vertical and lateral skeletal norms.
Most commonly treated using fixed appliances or function +/- fixed appliances.
Often consider Xtns if crowding present.
Orthognathic tx considered if skeletal discrepancy severe.
163
When would a removable appliance alone be appropriate in class 3 cases?
Mild cases where tipping teeth would be appropriate or at a young age interceptive when crossbite occurs +/- mandibular displacement.
164
At what age would it be appropriate to undertake orthognathic treatment?
Girls 16-18.
Boys 18-20.
165
Is mandibular displacement favourable for correction of Class III? What other features are favourable indicators of success?
Yes
Edge to edge.
166
What are ideal requirements of a satisfactory index? (list them)
index = a tool for categorising
1. Reliable - can be used repeatedly with accuracy.
2. Valid - measures what is meant to.
3. Acceptable - to the profession and public
4. Requires minimal judgement - easy to learn and use.
5. Administratively simple - cheap to use.
167
Name 2 key orthodontic indices.
Peer assessment rating (PAR) = outcome assessment
Index of Orthodontic Treatment Need (IOTN) = assessment for treatment need.
168
What is peer assessment rating?
Assessing OUTCOME.
Pre- and Post- tx models scored.
A cumulative socre.
5 occlusal traits scored using PAD 'ruler'.
i. upper and lower anterior segments
ii. L & R buccal segments
iii. OJ
iv. OB
v. centrelines
Weighted scores e.g. OJ weighting is 6.
Aim for 75% improvement in PAR scores.
169
What is IOTN?
Index of Orthodontic Treatment Need
Attempts to identify pts who 'would most likely benefit from orthodontic tx'.
It is used to categorise occlusion to assess the impact of dental health, function and psychosocial wellbeing.
170
What are the two components of IOTN?
Dental health component (DHC) 'scored' 1-5.
Aesthetic component (AC) 'scored 1-10.
171
What IOTN scores qualify for NHS tx?
IOTN must be 3.6 or above in under 18 year olds.
If dental health component of 4 or 5, qualify (don't need aesthetic component).
If dental health component 3, look at aesthetic component, need score of 6.
If dental health component of 1 or 2, they don't qualify.
172
What does the Dental Health Component (DHC) of IOTN look at?
Ranks occlusal traits according to their severity.
Looks for the SINGLE MOST DETRIMENTAL OCCLUSAL FEATURE in relation to dental health and function.
5 categories of severity: 1 = no need; 2 = little/no need; 3 = moderate/borderline; 4 = need 5 = severe need.
Each of the 5 categories is subdivided and given a letter.
Letters indicate the trait of the malocclusion.
i. e.g. OJ >6 but less than 9mm. = 4a.
ii. e.g. OJ >9mm = 5a
iii. e.g. impacted teeth = 5i
173
How do you decide on which letter to use in DHC of IOTN?
MOCDO!
Missing teeth
Overjet
Crossbites
Displacement of contact points (Crowding)
Overbites
174
What is a flaw with IOTN?
Spacing is not measured unless tooth deviates from the line of arch.
If tooth lies out the arch, then it can be measured as displacement of contact points.
175
When only can you record reverse overjet? (IOTN)
When all 4 incisors are in lingual occlusion, then you can record reverse overjet.
176
What is the aesthetic component of IOTN?
Need for tx
1-4 = none/slight
5-7 = moderate/borderline
8-10 = need
it is up to the pt to score themselves. It is subjective and an individual judgement.
Look at the photo which is an EQUIVALENT AESTHETIC CONCERN.
177
What are bad points about IOTN?
Class II div 1 - AC (all pts on aesthetic score are class II div 1)
Complexity not assessed e.g. 3 impaction.
Some versions of crowding - no score.
Evidence for DHC
Decisions?
178
What is the role of the GDC in ortho tx? (5)
Assessing pts including IOTN.
Informing pt of options & appropriate referral.
Understand xtns
Support during orthodontic tx e.g. OH
Monitoring retention
179
What OH and diet advice would you give to an ortho pt as a GDP?
OHI - brush 2x per day for 3 mins with fluoride toothpaste. Quick brush after lunch. Manual or electric. Interdental brushes are useful. Won't be able to floss with fixed appliances.
Diet - sugar onlay at meal times and not in between (max 3 times a day). avoid fizzy drinks + energy drinks. limit fruit juices due to acidic content. if chewy + sugary never. Sugare free chewing gum ok. Water, milk, tea safe. avoid hard foods - chop up first or avoid.
Give wax or trim if rubbing. Encourage to see orthodontist.
180
How long to orthodontists normally review retainers for?
A year
181
What are different types of retainers?
Vacuum formed retainers - wear every night for a year. Can gradually reduce but to maintain long-term alignment, part-time long-time wear is usually recommended. They can not fit if pt doesn't consistently wear.
Hawley retainer - metal wire and plastic.
Bonded retainers - must make sure still attached to each tooth. superfloss to clean around. Can break, refer back to orthodontist or replace. can support with VFR.
One type is not necessarily better than another.
182
What are 4 types of orthodontic emergencies/problems?
Patient discomfort
Fixed appliance breakages
- soft tissue trauma
- lost bracket/band
- # archwire
- lost o-ring/elastic chain
Removable appliance breakages
Retainer problems
183
What is general advice about patient discomfort w orthodontics?
Discomfort expected for first 3-5 days after braces first fitted.
Discomfort common for first 3 days after any adjustments.
Reassure pt.
Analgesics (ibuprofen and paracetamol) orthodontic wax.
184
Why do wires behind 6s dig into cheek and cause soft tissue trauma? (hint: what happens to the 2 different types of wires)
Light wires (0.12", 014", 018" NiTi)
i. Swivelling
ii. Displacement
iii. Left long!
Heavy wires (later in tx)
> during space closure teeth will slide along arch wires resulting in wire sticking out.
185
How can you prevent light wires behind 6s digging into cheek?
Light wires may be sintered before use (by heating with a flam) & tucked in to prevent cheek damage.
186
How can you treat heavy wires behind 6s digging into cheek?
Give wax
Bend it in carefully
Trim carefully if possible (care needed with tubes)
If you dont have distal end cutter, remember that wire will be sharp so hold on to piece whilst you cut it or use gauze to 'catch it' (avoiding losing the piece risk of inhalation).
187
What can you do if a bit of brace is digging in to cheek/lip?
Try bend it out the way
Wax (orthodontic or ribbor wax).
188
Why do brackets detach from tooth?
Patient non-adherence e.g. diet. Try and prevent with OH advice.
Failure of the bonding process - lack of moisture control, operator error, enamel structure.
189
How do you treat a detached/lost bracket?
Remove the module (elastic band) with probe.
Remove bracket from archwire to allow cleaning.
If bracket on 6 lost can trim archwire distal to last attachment.
Patient MUST INFORM THE TREATING ORTHODONTIST.
190
How do you treat a molar band which is loose?
Refer to treating orthodontist
Consider:
Bending wire out the way (light wire) & remove loose band.
Cut archwire distal to the next tooth in the arch (heavy wire) & remove loose band.
If band present you remove it - GIVE IT to the pt.
191
Why does a broken archwire happen?
Patient chews hard things e.g. pens.
Archwire high on bite.
192
What is treatment for broken archwire?
Remove loose fragment. Tuck any ends if possible. Refer to treating orthodontist.
193
How can you treat lost elastic modules from the bracket?
Reassure pt
If wire in good position - reassure
If wirse coming loose, advise pt to contact the orthodontist.
194
What is a power chain used for?
Used to close spaces, and may connect individual teeth, groups of teeth or all of the teeth in the arch.
195
How do you treat an elastic chain broken or lost?
Advise to contact orthodontist. Any bits handing about can be cut off, or attached to a bracket/hook.
196
What do you need to watch for with broken quadhelix or trans-palatal arch?
#
'embedding' of wires
wires digging in
Loose bands
197
How can you treat broken quadhelix or trans-palatal arch?
If wires are diggin in, can bend them up out of the way.
Refer to treating orthodontist.
198
What is possible tx to a hook or ligature detached or digging in?
If broken gather & tuck around bracket or archwire.
Tuck loose ends under the archwire with tweezers.
Cut.
199
What 6 problems can occur with a removable appliance?
1. Fractured acrylic on biting surface
2. Fractured acrylic palatally
3. Fractured wize
4. Mid-line screw loose.
5. Soft tissue trauma
6. Does not fit.
200
What questions do you ask pt when there is a problem with URA?
When was the brace last worn?
Can the pt carry on wearing the brace without discomfort?
Can the brace be repaired?
201
What are the problems with a broken removable appliance?
If not worn the appliance can't work.
If not worn the teeth will move and erupt.
If not worn then any achieved expansion and tooth movements may relapse.
202
What is the tx for a fractured acrylic on biting surface or acrylic palatally?
Smoothening sharp acrylic with bur.
Try to ensure pt keeps wearing brace if possible, consider nights only.
Refer to treating orthodontist.
203
What are 3 problems with VFR retainers?
Lost
Broken
Does not fit
204
What do you do if the VFR is lost, broken or not fitting?
Check when retainer was being worn - should wear at night-time, every night for first year then at least 2x a week indefinetly.
Can consider replacing retainer, if so
i. advise pt that this will only keep the teeth in their current position, will not re-align any teeth.
ii. advise of cost of new retainer and take new impression.
Or refer back to treating orthodontist.
i. advise pt there may be cost of new retainer if pt has been discharged.
205
What problems can occur with a fixed retainer?
lost, # wire, composite loose.
206
How can you treat a fixed retainer with a problem?
Repair composite if wire intact and teeth has not moved.
Refer back to treating orthodontist - advise pt there may be a cost if pt has been discharged.
207
What are key points to orthodontic emergencies in practice?
Reassure
Try to remove source of discomfort.
Advice/analgesics if not possible to remove problem.
Try to maintain active component of appliance if possible.
Advise them to contact orthodontist to arrange an earlier review if necessary.
Support with advise e.g. OHI, advice re: care on eating, regular attendance with both dentist and orthodontist.
208
What factors do you take into account when treatment planning?
AIMS of ortho tx planning must take into account:
- pt wishes and motivation.
- skeletal and soft tissue background
- dental features
209
What is orthodontic anchorage and why is it needed?
Orthodontic anchorage is the resistance to the reactive forces to the intended tooth-moving forces.
Tooth-moving forces create equal and opposite (reactionary) forces. These reciprocal (reactionary) forces must be resisted to minimise unwanted reciprocal tooth movement. The resistance is called anchorage.
210
What are the different sources of orthodontic anchorage. (I/O x4, E/O x1)
Intra-oral:
i. Teeth in same arch (inter-maxillary)
ii. Teeth in opposing arch (inter-maxillary)
iii. Oral mucosa/vault of palate
iv. (Implants/TADS)
Extra-oral:
i. Headgear/facemasks
211
What are general treatment aims of orthodontics? (4)
Relieve crowding
Level and align arches
Correct OB and OJ
Correct the buccal segment relationships.
Aim for class I incisors and fully interdigitated molars (Cl I, full unit class II or III).
212
What factors do you consider when planning where to place occlusion?
1. Facial profile
i. contour of nose
ii. chin profile
2. Skeletal base
3. Dental features:
i. periodontal health
ii. lower labial segment position.
213
Why do we not want to move the A-P of the lower incisors?
They lie in a position of balance between the soft tissues. We risk producing an unstable position. We treatment plan around their stable position.
Usually aim to not move the lower incisors substantially forwards or backwards and not expand the arches very much because those changes make stability less likely.
214
What are some exceptions to not moving the lower incisors substantially?
Digit-sucking habits
Class II div 2 cases
Lower incisors 'trapped' in palate in class II div 1 cases.
Very mild crowding (<1-2mm).
215
When can you use a removable appliance?
To tip teeth
--- Correct an anterior crossbite
---Correcting an increased overjet with proclined upper teeth
216
What are the 4 stages of tx planning?
1. Gathering data - assessing malocclusion
2. Compiling problem list - think about order
3. Deciding tx AIMS
4. Deciding tx MEANS
217
DEFINITION: Orthodontic anchorage?
learn: orthodontic anchorage is the resistance to the reactive forces to the intended tooth-moving forces.
Haworth's definition = orthodontic anchorage is the resistance to unwanted tooth movement.
218
Why is orthodontic anchorage necessary?
Tooth-moving forces create equal and opposite (reactionary) forces. These reciprocal (reactionary) forces must be resisted to minimise unwanted reciprocal tooth movement.
The resistance is called orthodontic anchorage.
Must be taken into account when planning tooth movement.
Anchorage helps plan space requirement (XLA necessary?). Knowing how and where teeth will move during tx. Planning mechanics (use of inter-maxillary elastics, when to stop head gear etc).
219
What is the rate of tooth movement related to?
Tooth movement is related to the level of force per unit tooth root area (i.e. size of the roots).
This is called the Differential Force theory.
220
Why can large forces intended for tooth movement be bad?
Large forces crush the periodontal blood vessels and decrease tooth movement.
220
DEFINITION: Loss of anchorage?
Unwanted movement of the anchor teeth during orthodontic treatment to an extent which prevents the planned tooth movements from being achieved.
220
What is intra-maxillary anchorage?
Anchorage obtained from structures within the same arch that the movement is happening.
the root surface area of other teeth (not being moved) in an arch is a source of anchorage.
220
Why is inter-maxillary anchorage not used with removable appliances?
When open mouth, will pull out appliance.
221
How is the oral mucosa/vault of palate a source of anchorage?
A steep palate and its overlying mucosa may contribute resistance to movement.
The palate is a source of anchorage for removable (and functional) appliances.
222
What is extra-oral anchorage?
This means a force applied from outside the mouth to reinforce anchorage. This force is resisted by the bones of the head (or sometimes the forehead & chin).
Unlike the teeth, these bones will not move in response to those forces.
223
Why do we need headgear?
Not enough anchorage in the mouth.
Can also use as tooth-moving force to move all teeth distally.
Uses:
i. anchorage - 250g per side for 10-12 hours.
ii. distal movement - 500g per side for 12-14 hours.
224
What is orthodontics and friction? When does orthodontic friction occur? What factors influence orthodontic friction?
Ideally there would be no friction when want to move teeth and loads when don't want to move teeth. If get wrong can result in loss of anchorage.
Occurs during alignment and sliding mechanics.
Archwire factors, bracket factors, ligation factors.
225
Why is it important to make a problem list?
Turns a mass of data into short relevant list.
No problems forgotten - now or later
Focuses thoughts into real problems
Records 'negative' aims i.e. problems which we are going to accept.
Simplifies explanations to the pt
Help you decide if pt needs referring
Helps write a referral letter.
226
