Orthodontics Flashcards
What are the skeletal classifications? (3)
- class I maxilla lies 2-4mm in front of mandible
- class II maxilla lies >4mm in front of mandible
- class III mandible lies <2mm behind the maxilla
What is the vertical assessment of the patient? (2)
- frankfort mandibular plane angle
- lower facial height
What points does the frankfort plane intersect? (2)
- inferior margin of orbit
- superior margin of external acoustic meatus
What is class II div I incisors?
Upper central incisors are proclined. Lower incisor edges lie posteriorly to cingulum plateau of upper incisors
What are the types of overbite? (3)
- complete
- incomplete
- traumatic
What is the nasion?
The most anterior point of the fronto nasal suture in the median plane
What is the pogonion?
The most anterior point of the bony chin
What is the menton?
The most anterior inferior midline point on the mandibular symphysis
What is the gonion?
The constructed point of intersection of the ramus plane and the mandibular plane
What is the E plane angle?
Ricketts aesthetic plane
In a balanced force the lower lip is +2mm and the upper lip is -2mm
What materials do we use for fixed appliances? (5)
- brackets
- wires
- elastomers
- coil springs
- mini implants/screws
What materials do we use for removable appliances? (3)
- wires
- acrylic
- thermoplastic
What are the ideal material properties of orthodontic brackets? (5)
- strong
- bio compatible
- bondable
- aesthetic
- low friction
What are the types of ceramic brackets? (2)
- mono crystalline
- poly crystalline
What are the stages of fixed appliances? (2)
- aligning and levelling
- space closure/major tooth movements
What are the different shapes of orthodontic arch wires? (3)
- round
- rectangular
- square
What are the characteristics of nickel titanium wires? (2)
- shape memory
- super elasticity
What is resilience?
The amount of energy absorbed by a structure when it is stressed to its proportional limits
What is formability?
The amount of permanent deformation that a wire can withstand before failing
What are the ideal properties of aligning arch wires? (4)
- formable
- cheap
- low friction
- flexible
What is another name for heat treating?
Annealing
How do you heat treat SS? (2)
- removes stress
- increases elastic limit/resilience
What are the types of coil springs? (2)
- open
- closed
What materials are elastomeric made out of?
Polyurethane
What are the properties of polyurethane? (4)
- elongates on stretching
- contracts
- full recovery to original shape
- quick force degradation
What are the uses of thermoplastics? (2)
- retainers
- aligners
What are miniscrews?
Temporary anchorage devices that provide temporary mechanical retention
What are miniscrews made out of?
Titanium alloy
What are the comments types of fixed appliances?
Variations on the pre adjusted edgewise system
What are the indications for fixed appliances? (5)
- rotations
- multiple tooth movements
- bodily movement
- space closure
- lower arch treatment
What are the contraindications for fixed appliances? (4)
- poor oral hygiene
- active caries
- poor motivation
- mild malocclusions
What are the risks of fixed appliances? (6)
- decalcification
- root resorption
- loss of periodontal support
- TMJ dysfunction
- failed treatment and relapse
- pain, ulceration etc
What are the types of attachment to the tooth? (2)
- bands
- bonds
What teeth would you usually use bands on?
Molars or premolars or teeth with ceramic crowns
What are bonds?
Perforated or mesh bases held on to the teeth by acid etch composite
What are the types of brackets? (3)
- modules and wire ties
- self ligating
- ceramic brackets
What are the phases to active treatment? (3)
- alignment and levelling
- major tooth movement
- finishing
What types of wire would you use in the alignment phase?
Light flexible
What is the alignment phase? (4)
- usually arch wires changed each visit
- wires of increasing stiffness
- deformation energy dissipates as wires straighten and pull teeth into alignment
- each new wire is deformed less but has a higher deformation energy
What occurs in the major tooth movement stage? (2)
- usually left unchanged each visit
- sliding mechanics is when teeth are pushed or pulled along the arch wire by power chain, coil springs or elastic bands
What occurs in the finishing stage? (3)
- detailing of alignment and interdigitation
- fine adjustments to bracket position
- some bends to arch wire
What is intra membranous bone formation?
When mesenchymal cells differentiate into osteoblasts which calcify into bone
What is the location of intra membranous bone formation? (2)
- maxilla
- mandible
What is endo chondrial bone formation?
When cartilage cells hypertrophy into a calcified matrix and osteogenic invasion creates bone
What is the best age for treatment using a growth modifying appliance in females and males? (2)
- 12-14 for males
- 11-14 for females
What is the treatment for a class III occlusion maxillary deficiency?
Face mask
What is the definition for a functional appliance?
An appliance that utilises or redirects the forces of masticatory and/or circum oral muscles to produce or permit tooth movement and may modify facial growth
How do non functional appliances work? (3)
- stretch the muscles of mastication
- posture mandible
- differential tooth eruption
What are the skeletal effects of functional appliances? (4)
- causes forward displacement of the mandible
- places a backward force on the maxillary arch
- accelerates condylar growth
- redirects condylar growth
What functional appliance can you use if the patient is not very compliant?
Herbst appliance
When should you prescribe a functional appliance? (4)
- mild to moderate increase in overjet
- increase in overbite
- active facial growth
- willingness to comply
What are the indications for functional appliances? (6)
- motivated patient
- pre adolescent growth phase
- skeletal discrepancy mild or moderate
- increased overjet/overbite
- procaines maxillary incisors
- well aligned arches
What are the contraindications for functional appliances? (5)
- poor motivation
- age>14
- poor dental health
- condylar disease
- proclaimed lower incisors
What are the advantages of functional appliances?(5)
- removable and easy to clean
- may avoid extractions
- accelerates skeletal growth
- early treatment
- less damage to tooth tissue
Why do functional appliances have less damage to tooth tissue? (3)
- less root resorption
- less chance of decalcification
- less effect on bone levels
What are the disadvantages of functional appliances? (3)
- compliance
- lack of detailed tooth movement
- candidosis
What are the types of functional appliances? (5)
- anderson
- twin block
- frankel
- bass
- herbst
What are the examples of removable appliances? (4)
- an active plate
- functional appliance
- space maintainer
- retainer
What are the drawbacks of removable appliances? (5)
- can tip teeth only
- can only move a few teeth at a time
- can be taken out by the patient
- adverse effects on speech
- poorly tolerated in lower arch
What are the advantages of removable appliances? (4)
- relatively simple to use
- difficult to over activate
- good anchorage
- less chair side time and low cost
What are the components of removable appliances? (4)
- active components
- retentive components
- anchorage
- baseplate
What is the value of forces required to move teeth?
No more than 24-40grams per teeth
What kind of clasps can you get? (3)
- adams or delta clasps
- southend clasps
- ball hooks
What is the definition for anchorage? (2)
- the area from which the force is applied to move the teeth
- for every action there is an equal and opposite reaction
How do you increase anchorage? (5)
- clasp more teeth
- move only one or two teeth at a time
- use lighter forces
- occlusal capping
- add headgear
What is the role of the baseplate? (4)
- connects all components
- vehicle for transmission of force from anchorage to active components
- supports anchorage through palatal coverage
- can incorporate bite planes
What are the uses of anterior bite planes? (2)
- reduce deep overbites
- rarely used to free occlusal interferences
How do anterior bite planes work? (2)
- work by allowing posterior teeth to erupt
- temporary increase in face height accommodated by facial growth
What are the additional claimed effects on an anterior inclined bite plane? (2)
- proclamation of lower incisors
- functional effect
What are posterior bite planes used for?
To free occlusal interferences
What are the advantages of removable appliances? (3)
- removed for cleaning
- excessive forces cannot be applied
- little clinical time needed
What are the disadvantages of removable appliances? (4)
- limited to tipping movements only
- limited rotational movement on incisors only
- problems with retention
- not well tolerated in lower arch
What are the indications for removable appliances? (4)
- minor tooth movements in mixed dentition as first phase of 2 phase treatment
- to prevent damage to dentition and periodontium whilst permanent dentition established
- to establish normal function
- to reduce deep overbites in growing patients
What are the active components? (2)
- springs
- screws
What are the advantages of springs? (2)
- cheap
- less pt compliance
What are the disadvantages of screws? (2)
- expensive
- bulky
What are the advantages of screws? (4)
- effective speech more
- ease of insertion
- minimal operator skill
- retention on teeth being moved
What are the alternative sources of space? (4)
- extractions
- increased arch length
- increased arch width
- inter proximal reduction
What factors should you consider for borderline extractions? (4)
- profile
- skeletal pattern
- class II div 2
- MH
When should you extract upper central incisors? (3)
- trauma
- dilaceration
- ectopic
When should you extract 2 lower incisors? (2)
- severe lower incisor crowding
- severe displacement of incisors
When would you extract one lower incisor? (4)
- class 3 malocclusion
- lower incisor crowding
- severe rotation
- severe displacement
Why are premolars the favourite choice for orthodontic extraction? (4)
- no aesthetic impact on smile
- space near to crowding
- straightforward extraction
- molars provide good anchorage for appliances
When would you extract second permanent molars? (3)
- only provides a very little space to relieve crowding
- can help with moving upper posterior teeth distally
- may dis impact 3rd molar
What non orthodontic factors would you consider for tooth extractions? (5)
- tooth quality
- pathology
- congenitally absent teeth
- abnormal tooth shape
- difficult extractions
What factors should you consider when choosing the retention regimen? (5)
- likely stability of result
- initial malocclusion
- oral hygiene
- compliance of patient
- pt preference
What are the types of retainers? (3)
- essex retainer
- hawley retainer
- bonded retainer
What is the overjet normally?
2-4mm
What features of the lip do we assess? (4)
- lip competence
- lip fullness
- nasolabial angle
- method of achieving an anterior seal
What is the nasolabial angle?
Formed between the base of nose and the upper lip and should be 90-110*
What factors indicate that a low fraenal attachment is causing a midline diastema? (3)
- when the frenum is placed under tension there is blanching of the incisive papilla
- radiographically a notch can be seen at the crest of the interdental bone between upper central incisors
- anterior teeth may be crowded
