Orthodontics Flashcards
What is orthodontics?
It is the branch of dentistry primarily concerned with the extent of normal variations of form and function of bones, soft tissues and teeth and the way in which they affect occlusion.
What are the main drivers for ortho treatments?
- Aesthetics
- Functional reasons: increased overjet, crossbites
- Societal and cultural pressures
What is interceptive orthodontis?
Interceptive orthodontics or primary orthodontics is an approach that uses phased treatments to manipulate growth, and particularly common growth patterns and correct developmental occlusion problems.
What is the difference between growth and development?
Growth - is an increase in size
Development - is an increase in complexity
What should a graduate dentist be able to do in terms of orthodontics?
- Distinguish abnormal development and growth from that which is normal
- Perform an orthodontic examination and explain the diagnosis, then devise treatment options, detailing the benefits and risks of each
- Commence, monitor and complete interceptive orthodontic treatment in a patient
What are some of the factors that influence growth?
- Genetic factors
- Environmental factors
Why should yo know about normal growth patterns?
In order to recognise deviations
What to do if you find growth is abnormal?
- Establish possible aetiological factors
- Seek assessments
- Understand suitable options for intervention
What is a cephalocaudal gradient?
It is a chart of proportional growth.
Structures towards to head grow first
What are growth curves?
Scammon’s curves They are graphs that represent that different tissues grow at different rates
What is more useful - developmental or chronological age?
Developmental. It is more useful to know stage of growth, rather than age, that specific growth occurs for orhtodontics.
What are the peaks of growth in people?
- Childhood peak at about 5 years
- Juvenile peaks at about 7 and years old
- Adolescent peak at about 11-13 years for females and 13-15 years in males
What is the use of lateral cephalometry?
Lateral cephalometry standardised, reproducible radiograph used primarily for orthodontic diagnosis and treatment planning.
It is used to compare jaw growth over time thus is a good guide in orthodontic treatment.
It is able to assist with cervical vertebrae maturation which is a type of biological indicator of skeletal maturity. The vertebrae C2-C4 is assessed.
When do you want to catach potential orthodontic case for interceptive treatment?
Class II treatment are most effective when you detect that the patient cephalogram is at CS 1 or 2 and you able to utilise maximum mandibular growth.
Class III treatment is most eefective when it is broken down itno two distinct stage: Maxillary expansion before maximum mandibular growth AND mandibular manipulation during pre-pubertal/pubertal stages.
Which structures make up the cranium?
- Cranial vault akak calvarium
- Cranial base
What structure make up the face?
- Naso-maxillary complex
- Mandible
How does the cranium grow?
2 distinct methods of growth:
- Intramembrenous ossification - provides gross growth
- Ectocranial resorption and remodeling - localised growth - the inner cortical plate resops and the outder cortical plate experiences deposition due to local growth of brain - think about all the cruves and bumb the brain has
What is the suture theory of craniofacial growth?
This theory was popularized by Sicher in 1941 which states that sutures are the primary determinant of the craniofacial growth. Expansion forces at the sutures lead to expansion of bone and thus growth of craniofacial skeleton.
What is the cartilage theory of craniofacial growth?
This theory was popularized by Scott in 1950s and states that cartilage determines the craniofacial growth. Proponents of this theory state that cartilage is responsible for the growth and bone just replaced it.
What is the functional matrix theory of craniofacial growth?
The functional matrix hypothesis was popularized by Melvin Moss in 1962. This theory said that neither bone nor cartilage is a major determinant of growth but soft tissue is. His view stated that as soft tissues around the jaw and face grow, bone and cartilage follow the growth of these soft tissues.
What type of bones are present in the cranial vault?
Flat membranous bones with suture in between. Osteogenesis occurs in the ossification centres + sutures. The cause of increase area of bones occurs due to brain growth. The out cortical plate usually deposits and inner cortical plate resorts.
What type of growth is responsible for ossification of the cranial vault?
Intramembranouse ossification - which is a direct transition of the mesenchymal tissue into bone due to osteoblasts deposition. This usually occurs in non-load bearing areas csuch as the cranial vault, maxilla and mandible (body)
What type of growth is responsible for ossification of the cranial base?
Endochondral ossification - where bone develops from carilagious precursor. It is usually occuring in load bearing areas like cranial base, long bone and mandibular condyle.
How does naso-maxillary complex grow?
It grows downwards & forwards in relation of the cranial base.
How does the mandible grow?
The mandible grows up and back.
It occurs via the bone remodelling via subperiosteal resorption & deposition.
Cartilaginous growth occurs in the condyle
From which branchial arch does the mandible originate?
1st Branchial arch.
Why is bone resorption in certain areas of the mandible essetial?
Bone resorption creates space for the eruption of teeth that don’t have of decidious pre-cursor - thus lower the probability of impacted molars (think surgical extraction or third molars)
What are the key points to craniofacial growth in orthodontics?
- Much of the vertical face height increase due to tooth eruption + alveolar bone production
- Mx & Md + dentitions desplaced down and forward relative to the cranial base
- Individuals experience differing amounts and direction of facial growth
- Around adolescence, slight differential growth of Md relative to Mx - meaning mandible tries to catch up
- Facial growth dependent on idividual growth patterns
- Factors infleuncing growth & development: genetics, SES, neural control, exercise, neural control, hormones and more.
What is an apical base?
It is the junction of alveolar & basal bones of the maxillary & mandible in the region of the apices of the teeth.
It is important for dento-alveolar compesation - which means that tooth eruption and alveolus dvelopment compensate for apical base dimension - making the teeth look “out of place slightly”
What is malocclusion?
It is a failure of the dento alveolar compensatory mechanism.
What influences tooth position post eruption?
It is influenced by soft tissues and oro-facial function.
What is crowding and what types of crowding are there?
Crowding - the discrepancy between tooth size & jaw size that results in the misalignment teeth.
Primary crowding - genetic origin
Secondary crowding - environmental factors such as extraction as a child
Tertiary crowding - occurs in the post adolescent period
Give a brief summary of growth of all cranio-facial structures?
- Cranial vault: sutures (intramembronous) and surface remodeling
- Cranial base: growth of cartilage in the
synchondroses (endochondral) - Maxilla: combination of soft tissue matrix and
cartilage (intramembronous) - Mandible: soft tissue matrix (intramembrounous body and endochondral condyle)
At 10 years old - what sould you do to the patient in order to recognise appropriate tooth growth and positioning?
Palpate around the areas that are distal and lingual of the primary canines in order to feel the permanent canines - because they are the most impacted teeth besides third molars.
What is a length of a dental arch?
It is the approximate distance from central incisors to most distal point of 2nd primary molars
What is dental arch circumference?
Distance measured round the arch from the mesial contact of first primary molar to the mesial contact of the other first primary molar
What is the inter-canine width?
The horizontal distance between cusp tips of the upper and lower canines
What is the inter-molar width?
The horizontal distance between the righ and left central fossae of the upper and lower first primary molars
What is leeway space?
It is the difference between the combined mesio-distal width of the permanent canine & premolars and the width of the corresponding precursors.
This space is eventually lost as mesial drift of first primary molars occurs following eruption of permanent canine & pre-molars
What is incisor liability?
It is the difference between the total mesio-distal dimensions of the decidous and permanents incisors
How do permanent incisors have enough space to fit in the arch during eruption?
Space is gained from:
- Residual spacing between deciduous incisors
- Permanent incisors erupt into more labial position and occupy a great arch perimetes
- Deciduous canines move distally as incisors erupt
- Transvers increase in intercanine arch width
WHat is a physiological explanation of a common upper midline spacing aka “ugly duckling gap?
It is a variation of normal dental development
It arises as the effcts of:
- incisor apicies initially close together as incisors erupt
- lateral pressure from erupting laters and canines
Diastema may close after laterla incisors erupt
Diastema may persist if:
- deciduous canines have been lost
- upper incisors are flared labially
What are the factors that facilitate dental arch allignment?
- Use of interdental, primate and leeway spaces
- Increased inter-canine width; mainly due to transverse growth
- Proclined eruption of permanent incisors, forming a wider arch & increases dental arch length
- Appositional growth of alveolar processes in 3 planes
- Appropriate size of apical base and teeth
What are the factors that hamper dental arch alignment?
- Lack of interdental, primate and leeway spaces
- Reduction in dental arch length after permanent incisors erupt
- Dento-alveolar disproportion (mismatch between tooth & jaw size)
- Early loss of primary teeth
- Soft tissue issues - low frenal attachment resulting in midline diastema
- Oral habits such is sucking on a pacifier or suck on a thumb
Why do we classify things?In general not just orthodontics?
It creates convenience of description and it also helps us to compare individuals and populations
What are the three different facial profiles?
- Convex profile - posterior divergence
- Straight profile - neutral divergence
- Concave profile - anterior divergence
What are the 3 different skeletal classifications in orthodontics?
- Class I - Maxilla is 2-4 mm anterior to the mandible
- Class II - Mandible retrusive relative to the maxilla
- Class III - maxilla retrusive relative to mandible
What is the definition of the Angle’s molar classification?
It is the relationship between the mesiobuccal cusp of the maxillary first molar and the anterior buccal groove of the lower first molar.
If the cusp is pushed forward it is class II if it is pushed back it is class III.
Also the extend difference - it could me 1/2 unit or full unit
What are the problems with Angle’s molar classification?
Does not account for:
- Absent permanent first molars
- Different molar relationship both sides
- Specify the magnitude of discrepancy
- Specify skeletal or facial patterns
What is the BSI classification?
It is a british classification that looks at relationships of the incisors
Class I - singulum plateau of the maxillary incisor is filled by the incisal edge of the lower, corresponding incisors with small overjet
Class II (div 1) - maxillary tooth has a great overjet with labila proclination
Class II (div 2) - maxillary tooth has a great overjet with no labial proclination
Class III - maxillary tooth is posterior to the mandibular incisor or is edge to edge
What does MOCDO stand for?
- Missing teeth
- Overjet
- Crossbite
- Displacement of contact points
- Overbite
What are some the signs that can point out that a patient is a forward or backward mandible rotator?
- Inclinations of condylar head
- Curvuture of mandibular canal
- Mis-shape of lower border of mandible (too straight for back rotators and angled for forward rotators)
- Inclination of mandibular symphysis
- Interincisal angle deviations
- Inter-premolar and inter molar angles deviations
- Anterior lower face height stand out
How can we divide the face into thirds?
Vertically
1. Trichion to glabela
2. Glabela to subnasale,
3. Subnasale to menton
