3rd year Flashcards
4 common orthodontic problems
Crowding
Prominent upper teeth
Missing teeth
Extra teeth
What is malocclusion
An appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory
3 malrelationships of the arches
Anteroposterior
Vertical
Transverse
What is an anteroposterior arch malrelationship
The mandible is more or less protrusive than the maxilla
Describe a vertical arch malrelationship
The lower part of the face is too short or too long
Describe a transverse arch malrelationship
The face is asymmetrical when viewed from the front
3 common classifications of occlusion
Incisor classification
Skeletal classification
Angle`s classification
Equation for calculating crowding
Crowding = Total tooth size - Total arch length
3 severities of crowding
Mild < 3mm
Moderate 4-5 mm
Severe > 6mm
Describe overjet and what is considered normal
Horizontal relationship between the upper and lower incisors
Normal: 2 - 4 mm
Describe overbite and what is considered normal
Vertical overlap of the upper anterior teeth over the lower
Normal: 3-4 mm
Describe class I incisors
Lower incisor occludes with or lies directly below the upper incisor cingulum
Describe class II division 1 incisors
Upper incisors are proclined, lower incisor edges are palatal to the cingulum plateau of the upper incisors
Describe class II division 2 incisors
Upper incisors are retroclined and lower incisor edges are palatal to the cingulum plateau of the upper incisors
Describe class III incisors
Lower incisor edges lie anterior to the cingulum plateau of the upper incisors
Describe skeletal class I
ANB 2 - 4 degrees: balanced facial profile
Describe skeletal class II
ANB > 4 degrees: profile shows relative mandibular retrusion
Describe skeletal class III
ANB < 2 degrees: profile shows relative mandibular prominence
Describe Angle’s class I
Mesiobuccal cusp of the upper first molar occludes with the anterior buccal groove of the lower first molar
Describe Angle’s class II
The upper arch is at least half a cusp`s width anterior to Class I
Describe Angle’s class III
The upper arch is at least half a cusp`s width posterior to Class I
Describe the Index of Orthodontic Treatment Need (IOTN)
Used to describe need for treatment with an aesthetic and dental health component
Describe the Peer Assessment Rating (PAR)
Used for assessing the quality of treatment outcome
4 common congenitally absent teeth
Mandibular central incisor
Mandibular 2nd premolar
Maxillary lateral incisor
Maxillary 2nd premolar
4 types of supernumerary teeth
Supplemental
Conical
Tuberculate
Odontomes
2 differences of permanent incisors compared with primary
Larger (Mx 7 mm, Md 5 mm)
Greater proclination (10-15 degrees)
3 types of orthodontic appliances
Removable appliances
Fixed appliances
Functional appliances
3 types of removable appliances
Upper removable appliances
Lower removable appliances
Retainers
What is a removable appliance
Orthodontic devices which can be taken out of the mouth by the patient for cleaning
5 removable appliance actions
Tipping
Overbite reduction
Crossbite correction
Extrusion
Intrusion
5 advantages of removable appliances
Simple to use
Less chairside time
Reduced risk of decalcification
Simple to add pontic teeth
Well accepted by patients
4 disadvantages of removable appliances
Limited range of tooth movements
Require more laboratory time than fixed appliances, therefore expensive
Lower removable appliances are uncomfortable
They`re removable
3 components of removable appliances
Active component
Retentive components
Baseplate
6 removable appliances
Anterior / posterior biteplanes
URA - midline expansion screw
Palatal finger spring
Palatal finger spring retractor
Robert’s retractor
Buccal canine retractor
What is a fixed appliance
Devices that are attached to the teeth, cannot be removed by the patient and are capable of causing tooth movement
Forces required for bodily movements
50 – 120g
Forces required for torquing movements
50 – 100g
Forces required for rotational movements
35 – 60g
Forces required for extrusion movements
35 – 60g
Forces required for tipping movements
25 – 60g
Forces required for intrusion movements
10 – 20g
3 advantages of fixed appliances
All types tooth movement possible including bodily movement
Groups of teeth can be moved
Detailed movement possible
6 stages of treatment for straight-wire appliance
- Anchorage management
- Levelling and alignment
- Overbite correction
- Overjet correction
- Space closure
- Finishing and detailing
6 risks of orthodontic treatment
Recession
Root resorption
Pulpal damage
Periodontal ligament damage
Decalcification
Discomfort
5 reasons for orthodontic extractions
Relieve crowding
Reduce an increased overjet
Correct centrelines
Open space for missing teeth
Correct anterior open bite
What is orthodontic anchorage
The source of resistance to the reaction from the active components
What is anchorage loss
Extraction space closes due to forward movement of the anchor teeth rather than those teeth that we wish to move
4 means of providing anchorage
Other teeth
Baseplate on removable appliances
Orthodontic mini-implants
Extra-oral aplliances
2 ways of reducing the demands on the anchorage
Reducing the number of teeth being moved
Limiting the force from the active components to the optimum level for tooth movement (25-50g)
Most common orthodontic extractions in upper and lower arches
Upper arch: 1st premolars, 2nd premolars
Lower arch: 2nd premolars, 1st premolars
6 ideal properties of a retainer
Keep each tooth in its new position
Strong enough
Good aesthetics
Facilitate plaque control
Allow settling to occur
Be removable for eating, cleaning
What is a functional appliance
Appliance that alters the posture of the mandible commonly in the management of Class II malocclusion
5 components of fixed appliances
Brackets
Bands / bonded buccal tubes
Archwires
Ligatures
Auxiliaries
Optimum range of force for producing tooth movement in a single rooted tooth
25-50g
5 orthodontic radiographs
Orthopantomogram (OPT)
Occlusal radiographs
Periapical radiographs
Bitewing radiographs
Cephalometric lateral skull radiographs
4 indications for cephalometric radiography
Descriptive
Treatment planning
Monitoring treatment progress and growth
Growth prediction
Describe the bioelectric theory of tooth movement
Tooth movements occurs as a result of piezoelectricity and bioelectric potentials
Describe the pressure-tension theory of tooth movement
Tooth movements occurs as a result of cellular changes and chemical messengers
What does the action of rank ligand result in
Activation of osteoclasts leading to bone destruction
What does the action of osteoprotegerin result in
Inhibits rank ligand from activating osteoclasts leading to reduction in bone destruction
Incidence of ectopic eruption of 1st molars
2-6%
Incidence of hypodontia
4-6%
Incidence of supernumerary teeth
1-2%
Describe juvenile occlusal equilibration
After teeth have erupted into the occlusion they must continue to erupt at a slower pace to match vertical skeletal growth
Describe adult occlusal equilibration
Once the adolescent growth spurt has passed the teeth continue to erupt to compensate for wear and the continued vertical skeletal growth
3 advantages of Tip-edge appliance
Permits tooth tipping in early stages
Anchorage saving
Versatile
4 advantages of straight-wire appliance
Reduced wire bending as preadjusted design
Use of sliding mechanics
Precision and finishing
Flexible
4 disadvantages of Tip-edge appliance
Narrow bracket with poor control
Requires intermaxillary elastics
Complex in stage 3
Based on extension philosophy
4 disadvantages of straight-wire appliance
Friction
Anchorage demands
Adjustments still required for individual patients
Deceptive simplicity
3 process involved in maxillary growth
Primary and secondary displacement
Intermembranous ossification
Surface remodelling
2 process involved in mandibular growth
Endochondral growth in the condylar region Intramembraneous growth at other growth sites
Predominant trend of growth in mandible and maxilla
Posterior and superior, which displaces the mandible/maxilla downward and forward
When does symphyseal suture close
During 1st year
2 components of orthodontic treatment need
Normative need
Subjective need
5 indications for Hawley retainers
To carry pontic teeth (in hypodontia cases)
To allow settling
To maintain transverse dimensions
To carry a biteplane
Can allow for tooth eruption
2 indications for vacuum formed retainers
To retain all types of irregularity
As an adjunct to a fixed retainer
6 indications for fixed retainers
Median diastema
Adults
Cleft patients
Missing laterals / centrals
Mandibular incisor extraction cases
Severe rotations
2 contraindications for fixed retainers
Poor plaque control
Occlusion deep bite
4 risks/problems of fixed retainers
Decalcification
Unwanted tooth movements
Only retain anterior segments
Hinder interdental cleaning
Prevalence of Class I incisors
50%
Prevalence of Class II Div 1 incisors
35-40%
Prevalence of Class II Div 2 incisors
10%
Prevalence of Class III incisors
3-5%
4 ways to create space
Extractions
Interproximal enamel reduction
Arch expansion
Distalisation of teeth
6 areas of discussion after fitting an appliance
Oral hygiene instruction
Diet advice
Discomfort
Sports
Speech
What to do if something goes wrong
How long does it take for periodontal ligament fibres to remodel?
3-4 months
How long does it take for gingival fibres (collagen) to remodel?
4-6 months
How long does it take for elastic supracrestal fibres to remodel?
1 year
Sequence of arch wires
Initial alignment: NiTi
Intermediate archwire: CuNiTi
Working archwire: SS
Which teeth have the strongest anchorage value and why
Molars as they have the greatest root surface area
6 reasons why extraction pattern may be asymmetrical
Centreline correction
More space needed on one side
Supernumeraries
Caries / heavily restored tooth
More crowding in one quadrant
Anchorage situation more challenging on one side
Two types of power chain and where are the most commonly used
Open: upper jaw
Closed: lower jaw
3 types of clasps
Adams clasp
Southend and Half-Jackson
Ball ended clasps
5 reasons to treat orthodontic problems
Psychosocial benefits
Improves dentofacial aesthetics
Dental health (trauma, OH, periodontal health) benefits
Functional (TMJ, speech, eating) benefits
To facilitate restorative treatment
Sequence of eruption of primary teeth
A B D C E
5 ways to minimise relapse
Avoid enlargement of lower arch
Do not alter A-P position of lower incisor teeth
Achieve good incisor relationship at end of treatment
Maximise buccal interdigitation
Consider active retention for severe Class II cases
Use of an anterior biteplane
Correction of deep over bite
2 uses of a posterior biteplane
Correction of anterior open bite
Produce a vertical opening between anterior teeth to allow prolination of lingually placed upper incisors
Use of a mid-line expansion appliance
Correction of a crossbite
Use of a palatal finger spring
Proclination of a single upper incisor
Use of a palatal finger spring retractor
Retracting canines or premolars
Use of a Robert’s retractor
Retracting incisors in class II division 1
Use of a buccal canine retractor
Retract canines to reduce crowding or overjet
Spring diameter used in a buccal canine retractor
0.7mm
Labial bow diameter used in Robert’s retractor
0.5mm - supported by stainless steel tube
Spring diameter used palatal finger spring
0.5mm
Teeth to clasp for anterior biteplane
6’s (sometimes 4’s)
Teeth to clasp for midline expansion appliance
6 ‘s and 4’s
Teeth to clasp for palatal finger spring
6’s and 4’s
Teeth to clasp for palatal finger spring retractor
6 ‘s
Teeth to clasp for Robert’s retractor
6’s
Teeth to clasp for buccal canine retractor
6’s
Which teeth are Southend & Half-Jackson clasps placed on
Incisors
Which teeth are Adams clasps placed on
Premolars and molars
Material and diameter of an Adams Clasp
0.7mm stainless steel
3 active components of removable appliances
Springs
Labial bows
Elastics
Movement per month from removable appliance springs
1mm
Describe activation of palatal finger spring
By 2-3 mm
Describe activation of palatal finger spring retractor
By 1/2 width of the canine or premolar
Describe activation of Robert’s retractor
By pressing the vertical leg towards the tubing
Describe the activation of buccal canine retractor
By 1/3 width of the canine
How much space does extraction of upper 1st premolars provide
7mm space per side
How much space does extraction of upper 2nd premolars provide
3 mm space per side
How long is retention required before reorganisation
Minimum I year
Describe the standard retention protocol
0-3 months full-time
9-12 months part-time
Life time wear
3 pieces of information from a cephalogram
Relationship of maxilla and mandible to cranial base
Relationship of the teeth to the jaws
Relationship of the maxillary to the mandibular teeth
How is maxillary skeletal base position described
SNA 82° ± 3°
How is mandibular skeletal base position described
SNB 79° ± 3°
How is the relative relation of the maxilla to the mandible described
ANB 3° ± 2°
How is the inclination of the upper incisors to the maxillary plane described
109° ± 5°
How is the inclination of the lower incisors to the mandibular plane described
93° ± 5°
Describe crossbite
Maxillary teeth sit lingual to the mandibular teeth
4 changes that occur at the compression side
Compression of blood vessels
Cellular proliferation
Resorption of bone by osteoclasts and remodelling of PDL fibres
Tooth movement
4 changes that occur at the tension side
Stretching of PDL fibres
Cellular proliferation of fibroblasts and osteoblasts
Increase in length of PDL fibres
Deposition of bone
When does the transverse growth of arches cease
Once permanent incisors have fully erupted
Teeth that are most likely to undergo decalification
Maxillary lateral incisors
Most common ankylosed tooth
Mandibular D
Describe ankylosis
Fusion of alveolar bone and cementum
Sequence of eruption of permanent teeth
6 1 2 3 4 5 7 8
2 teeth that are most likely to undergo root resorption
Upper incisors
First molars
Teeth that are most likely to undergo pulpal damage
Upper incisors
