ORTHODONTICS Flashcards
What is orthodontics?
- Growth and development of the teeth, face and jaws.
- Diagnosis, prevention and correction of dental and facial irregularities.
What Andrew’s 6 keys.
- Correct incisor relationship (class I)
- Correct angulation- The root is angulated distally to the crown.
- Correct inclination
- Upper incisors crown is labial to root.
- All other teeth- the occlusal part is lingual to the gingival part.
- Tight approximal contact with no rotations
- Correct molar relationship (class I)
- Flat occlusal plane.
What are the risks of orthodontic treatment?
- Decalcification- the begining of caries around the bracket.
- Relaspe (patient needs to wear their retainer)
- Pain/ discomfort
- Root resorption
- Soft tissue trauma
- Loss of tooth vitality
- Candida infections
- failure to complete treatment.
What is the frankfort plane?
A line from the earhole (porion) to the orbital rim of the eye socket (orbitale)
Classify and discuss this jaw relationship
Class I-
The mandible is 2-3mm behind the maxillary basal bone.
This is the normal relationship.
There can be bimaxillary protrusion/ retrusion when both jaws are set forward or back
Classify and discuss this jaw relationship.
This is the class II.
This is when the maxilla is positioned >3mm infront of the mandible.
This can be caused by:
Mandibular hypoplasia (smaller mandible)
Maxilla being too large
Mandibular Retrognathia (a normal sized mandible which is positioned too far back)
Classify and discuss this jaw relationship
Class III.
This is when the mandible is positioned further forward than the maxilla.
This can be caused by:
Maxillary hypoplasia- maxilla is too small.
Mandibular prognathism- mandible is too far forward
Mandible is too big.
How does a class II affect the way the patient bites?
The patient has an overjet.
How does a class III affect the way a patient bites ?
Reverse overjet.
What class is commonly found in a cleft lip and palate patient and why
Class III due to scar tissue preventing maxilla growth.
What is this abnormality?
Crowding
What is this abnormality?
Spacing
What is this abnormality?
Increased overjet
What is this abnormality?
Reverse overjet
What is this abnormality?
Hypodontia
What is this abnormality?
Anterior open bite.
The teeth do not overlap at all.
What is this abnormality?
Deep bite.
The upper teeth overlap alot.
**also known as an overbite**
what is this abnormality?
Ectopic teeth (teeth are in the wrong place)
What is this abnormality?
Anterior crossbite
What is this abnormality?
Posterior crossbite.
Classifiy this incisor relationship.
Class I.
The lower incisor edge contacts at or below the cingulum of the upper central incisor.
Classifiy this incisor relationship.
Class II division 1
The lower incisors lie posterior to the cingulum of the upper incisors.
The upper centrals are proclined (or increased overjet)
Classifiy this incisor relationship.
Class II division 2.
The lower incisors contact posterior to the cingulum.
Theupper central incisors are retroclined.
(minimal overjet)
Classifiy this incisor relationship.
Class III
Lower incisal edges lie anterior to the cingulum of the upper incisors.
Upper incisors proclined. Lower incisors retroclined.
Name and compare the 4 types of occlusion?
Ideal occlusion (all 6 of andrew’s keys have been achieved)
Normal occlusion- most common
minor deviations -no aesthetic or functional problem.
Malocclusion- Significant deviations from the ideal that can be considered unsatisfactory aesthetically or functionally.
What do we use to vertically assess the patient?
The frankfort plane and the mandibular plane angle
What occlusal relationship are we expecting if the Frankfort line and FMPA meet before the back of the head?
The planes meet before the External occipital protuberance causing an Open bite
What occlusal relationship are we expecting if the Frankfort line and FMPA meet after the back of the head?
A deep overbite
Due to the tendency of parallel jaws resulting in the planes not meeting.
What is the mid sagital reference line?
The line from between the eyes down to the cupid’s bow of the lips.
Describe this lip relationship.
Competent lips- the lips meet at rest. The mentalis muscle is relaxed.
Describe this lip relationship.
Incompetent lips- the lips don’t meet at rest.
Describe this lip relationship
This is a lip trap.
The central incisor gets trapped infront of the lower lip.
Describe this lip relationship
Tight lower lip- The hyperactive lower lip can cause retroclination of the lower incisors.
Compare the two types of tongue thrust?
Adaptive- will stop when you treat the AOB
Endogeneous- this will just relapse again.
Compare the problem caused by thumb sucking to digit sucking?
Thumb sucking causes assymetrical problems.
Digit sucking causes symmetrical problems
What are the occlusal features of a thumb sucking habit?
- proclination of upper anteriors
- retroclination of lower anteriors.
- AOB or incomplete open bite.
- Narrow upper arch.
How do we measure an overjet?
measure the biggest gap you can get with the 4 incisors when the patient is occluding.
Describe this bite
An increased and complete overbite contacting the tooth. .
The upper incisors overlaps 1/3 to 1/2 of the lower incisor.
Describe this bite
Increased and Complete overbite contacting the palate.
Describe this bite
Incomplete overbite.
Describe this bite
Average bite.
Describe this bite
Anterior open bite.
Describe this bite
reduced open bite.
What are the parts of an orthdontic examination?
- History
- Extra-oral examination:
- Anterior posterior skeletal assessment
- Vertical assessment
- Lateral assessment
- Soft tissues
- Intra-oral examination
- Teeth
- Oral hygine and periodontal risk
- Lower arch
- Upper arch
- Occlusion.
What is lateral cephalometry?
Standardised lateral radiographs of the face head and skull
How is a lateral cephalometry reproducable?
Because the patient is positioned in a cephalostat. This is a set distance away from the cone and film.
What is the SNA?
This relates the maxilla to the SN line.
What is SNB?
This relates the mandible to the SN line.
What is ANB?
The differnce between the SNB and SNA.
Give the SNA, SNB and ANB of a class I
SNA- 81
SNB-78
ANB-3
Give the SNA, SNB and ANB of a class II
SNA- average
SNB- decreased.
ANB >5
Give the SNA, SNB and ANB of a class iii
SNA- decreased if maxilla is deificent.
SNB- normally average
ANB <1
What is the FMPA
Frankford mandibular plane angle.
The angle between the frankford and the mandibular plane.
What is the TAFH and what is this measuring.
this is the upper anterior face height, This measures from the nasion to the anterior nasal spine.
What is the LAFH and what does it measure?
The lower anterior facial height. This measures from the anterior nasal spine to the menton ?
What are the average FMPA and LAFH: TAFH.
FMPA- 27* +/- 4*
LAFH: TAFH= 55%
What values of FMPA AND LAFH:TAFH constitute long face syndrome.
FMPA >31*
LAFH:LAFH= >55%
What values of FMPA and LAFH:TFAH cause a short facial type.
FMPA <23 *
LAFH:TFAH <55%
Discuss the impact of an arch width discrepancy?
This causes the upper and lower cusps to be occluding. As a result the mandible deviate to occlude in ICP causing mandibular displacement of the jaw. (resulting in crossbite)
What is transverse dento-alveolar compensation ?
When the tongue and cheeks mould the alveolar pocess to maintain the occlusal relationship affected by the arch discrepancy/
What causes crowding?
small jaws with normally sized teeth.
macrodontia. (large teeth)
What causes spacing?
Large jaws with normally sized teeth
Microdontia.
Discuss this clinical image?
This is a conical/ peg shaped tooth.
It is known as a mesodens when close to the midline.
Effect- this displaces the adjacent teeth.
What is the SN line?
The anterior cranial base.
Discuss this clinical image.
This is a tuberculate supernumerary
which is an extra tooth which does not erupt.
Effect- this commonly blocks the permanent tooth eruption e.g. incisor.
Discuss this clinical image .
This is a supplemental tooth (extra tooth of normal morphology)
Effect- takes up space causing crowding.
Most common- upper laterals or lower incisors.
What is this clinical image?
This is an odontome which is a mass of toothlike structure. This can be compound (discreet denticles) or complex (Disorgansied mass of dentine/ pulp and enamel)
Effect- This impedes eruption and displaces the surrounding teeth.
Discuss the causes of retained primary teeth?
- Lack of permanent successor to cause exfoliation of the primary tooth.
- Infra-occluded primary molars
- Ectopic successor or dilacerated.
Compare balancing and compensating extractions?
Balancing- extracting the opposite tooth in the same arch. To minimise midline shift.
Compensating- extracting a tooth from the oposing arch on the same side. To prevent overruption which would prop open the occlusion.
How does losing primary incisors affect the dentition?
No impact.
How does loosing primary canine affect the dentition?
Would cause midline shift.
The buccal segments will mesially drift.
So we need to balance.
How does losing primary molars affect the dentition.
The space will close up.
6s will drift mesially and steal the space of the 5s.
More space is lost in:
- Crowded patients.
- When extracted early
- When Es are extracted rather than Ds.
- Uppers than lowers
When do we want to lose the lower 6s
at the development of the birfurcation of the 7s.
What effect does early loss of the lower 6s have.
The 5s will drift distally.
What effect does late loss of the lower 6s have?
the 7s will have already erupted resulting in poor space closure.
When do we compensate for molar extraction?
If we have lost the lower 6.
When do we balance the molar extraction
If there is premolar crowding.
Discuss ectopic first molars and how we can treat them?
- These are more common in the upper arch.
- Reversible before the age of 8.
- Are a plaque trap risk.
We treat them by:
- Separator
- Distalising the 6.
- Extracting the E
how do we treat ectopic upper centrals.
We want to space maintain.
- Surgical exposure and bonding of a gold chain.
- Creation of the space and using orthodontics to move the tooth into place.
Compare the two types of transposition.
When the position of a tooth has switched.
True- the root and the crowns have both been switched .
Pseudo-only the crown position has switched
How does a high labial frenum affect occlusion?
This can cause a median diastema
Canines eruption can cause spontaneous regression fo the frenulum allowing the diastema to close up.
How does tongue thrust affect occlusion?
The pateint pushes their tongue againt their front teeth causng an anterior overbite.
Compare the two types of tooth movement.
Physiological- Eruption and drifting.
Orthodontic- movement due to a force (Normally 1mm a month)
How does orthodontic tooth movement work and why?
Force is applied to the teeth which causes tooth movement due to the re-organisation of the bone around it. This is mediated by the PDL.
Discuss the differential pressure theory?
The force causes tension on one side of the PDL and compression on the other.
Tension causes bone deposition.
Compression causes bone resorption.
Discuss the mechano-chemical pressure theory?
- Mechanical stress on bone.
- Neuropeptides are released from nerve endings.
- Stimulation of fibroblasts, endothethial cells and alveolar bone.
- Fibroblasts communication to osteoclasts and osteoblasts.
- Remodelling of the alveolar bone and PDL.
Describe the tooth movement and forces required for Tipping?
It is a tipping movement
35-60g of force
Describe the tooth movement and forces required for Bodily movement ?
The tooth slides along a wire.
Force- 150g-200g
Describe the tooth movement and forces required for intrusion?
This is a gentle upwards pressure.
10-20g
Describe the tooth movement and forces required for extrusion?
Pulling the tooth down.
35-60g.
Describe the tooth movement and forces required for Rotation?
Two forces applied in opposite directions to rotate the tooth.
35-60g.
Describe the tooth movement and forces required for Apical root torque?
The movement of the tooth one way causes the root movement another.
50-100g.
Discuss the effect light force has on tooth movement?
- Hyperaemia of the pulp.
- Tension causing bone to be deposited. (Osteoblasts)
- Compression causing resorption of the lamina dura. (osteoclasts)
- Re-organisation of the PDL
Discuss the impact moderate force has on the tooth.
Tension side- hyperaemia of the vessels in the PDL.
Pressure side- Occlusion of the vessels of the PDL causing cell free areas (nothing going on- so no bone resorption)
There are osteoclasts underneath- nibbling from below.
There is a period of stasis then sudden movement of the tooth.
Compare light moderate and excessive force for use in orthodontics.
Light- what we use for tooth movement
Moderate- inefficient tooth movement and causes undermining resorption.
Severe- causes necrosis/pain/ undermining resorption and resorption of the root surface. BAD
Discuss other factors affecting the response to orthodontic force?
Duration- We want the patient to wear it at all times
Age- older patients will take longer initially for tooth movement.
Anatomy-
Dense/ thick/ little bone is much more difficult to move teeth through.
A digit or tongue thrust will overpower any appliance.
What is a functional appliance used for and how does it work?
This is for growing the jaw.
Postures the mandible away from its normal position and stretches the soft tissues.
Stretching the soft tissues generates pressure that is transmitted to the teeth and alveolus.
Upper teeth- we get reto-inclination and distal migration
Lower teeth- we get proclination and mesial migration.
What is the main reason for abnormalities of the head and neck and why?
Problems with the development of the neural crest.
As the neural crest migrates and differentiates into the:
Schwan cells
Bone and connective tissues.
Dentine, pulp, cementum and PDL.
Spinal and autonomic ganglia.
What is the face formed from?
Migrating neural crest cells in the frontal nasal process or the pharyngeal arches.
Compare the neurocranium and viscerocranium.
Neurocranium- forms a protective case around the brain.
Viscerocranium- a skeleton around the brain
What parts of the skull form by endochondrial ossification.
Base of the skull (cartilage precursor is laid down first)
What parts of the skull form by intramembranous ossification.
- Vault of the skull- Incomplete fusion at birth
- Anterior fontanelle (2 years)
- Posteiror fontanelle (2 months)
- Stops growing at 7 years.
- Maxilla- develops adjacent to the nasal capsule (cartilaginous)
- Mandible- Forms around Meckle’s cartilage. The growth of the mandible has to be stimulated. (e.g. no temporalis, no coronoid process)
Compare primary and secondary abnormalities .
Primary abnormalities- a defect in structure that can be traced back to an anomaly in development e.g. cleft lip.
Secondary abnormalities- Interuption of normal development that can be traced back to other influences e.g. Trauma/ thalidomide.
What is a deformation ?
Anomalies that occur due to outer mechanical effects on existing structures.
What is agenesia ?
Absense of an organ due to failed development during an embryonic period.
What is a sequence?
A single factor which results in numerous secondary effects.
What is a syndrome ?
A group of anomalies that can be traced back to a common origin.
Name and discuss this syndrome.
Foetal alcohol syndrome.
This is due to high alcohol consumption during pregnancy.
This causes:
small face
small eyes
small maxilla
small mandible
No philtrum.
Name and discuss this syndrome.
Hemofacial microsomia.
Problem with Neural crest migration.
Asymetry due to lack of development of one side of the face. This can affect the mandible, cheekbone and even the ear.
Name and discuss this syndrome.
This is treacher Collins syndrome.
Caused by deformity of the 1st and 2nd brachial arches.
Hypoplastic or missing zygomatic arch.
Hypoplastic mandible
Deformed pinna.
Name and discuss this syndrome?
This is cleft lip and palate.
Cleft palate- caused by incomplete fusion of the palatal shelves. This does not affect the teeth as it does not cross the alveolus.
Cleft lip-failed fusion of the maxillary prominenceswith the medial nasal prominences. This can cause:
Impacted teeth/crowding/ hypodontia/ supernumerary teeth/hypoplastic teeth/ caries/ maxillary hypoplasia.
Identify and discuss this syndrome.
Achondroplasia.
Problem with anyting formed by endochondrial ossification.
Shows defects in
A prominent forehead.
Retrusive middle third of the face.
Depressed nasl bridge
Skull base.
Identify and discuss this syndrome.
Crouzons-
Early fusion of the coronal and lambdoid suture.
Resulting in:
Shallow orbits
Retrusion and vertical shortening of the midface
Class III malocclusion
Narrow spaced teeth.
Identify and discuss this syndrome?
This is apert’s
This early fusion of all the sutures.
This results in increased pressure in the head.
Class III occlusion
AOB
Narrow spaced teeth.
Narrow high arched palate.
How does a baby’s head differ to that of an adults?
Smaller face compared to head size
Larger eyes
Lower set ears.
Upright and bulbous forehead.
A shallower vertical nasal region.
Compare sutures and synchondroses.
Sutures- Fibrous joints where the bone is laid down in the middle.(the areas of tension)
Synchondroses- the cartilage at the ends are converted into bone and new cartilage is formed in the centre.
Describe the growth of the cranial vault?
It grows by sutures and surface remodelling until the age of 7.
The forehead continues to expand in response to the air sinus (pneumatisation)
Describe growth of the cranial base?
Grows by endochondrial ossification and surface remodelling .
Half of the growth is completed by the age of 3.
The spheno-occipital synchondrois closes at 13-15(F) and 15-17 (M)
The cranial base angle affects the jaw relationship.
Describe the growth of the mandible?
This is displaced downwards and forwards.
We have bone resorption anteriorly and lingually.
We have bone deposition posteriorly and laterally
Increase in length of
20mm (F) and 26mm (M)
Describe the growth of the maxilla.
This displaces downwards and forwards relaetive to the anterior cranial base.
The forward growth creates space posteriorly for the maxillary tuberosities and molar teeth.
The length increases by 5.5mm (F) and 8mm (M)
Explain what is meant by growth rotations.
The idea:
More growth in the posterior face height- causes the mandible to rotate anticlockwise. This causes a forward growth rotation & a deep bite.
More growth on the anteiror face height causes the mandible to rotate clockwise. This causes a backwards growth rotation and could lead to an open bite.
Discuss the timing of mandibular growth?
This accelerates during puberty and lasts unitl 17 (F) and 19(M)
Discuss the timing of maxillary growth .
It slows down after the age of 7, so we want to complete any treatments that utilise maxillary growth pre-pubertal.
What is interceptive orthodontics?
Any procedure that will reduce or eliminate the severity of a developing malocclusion.
Discuss spacing in deciduous teeth.
We want spacing to prevent crowding
no spacing= 66% chance of crowding.
<3mm spacing= 50% chance of crowding.
3-6mm spacing= 20% chance of crowding.
> 6mm spacing= no crowding
What is the Leeway space?
This is the difference between cde and 3,4,5.
- 5mm in the maxilla.
- 5mm in the mandible.
At age 9- there should be a minimum of 18.5mm from the lateral incisor to the first molar to have enough space for the premolars and cannes (otherwise crowding)
What is the ugly duckling stage?
This is when we have
- distally ponted lateral incisors caused by the unerupted canines on the LI roots. (Eruption of the canines should fix this)
- Diastema
What size of diastema can be closed by eruption of the canines.
A gap <2.5mm.
What are we looking for to justify interceptive orthodontics?
Sequence (have the teeth errupted out of sequence)
Symmetry (has the contralateral tooth erupted within 6 months)
Supernumerary (is there an extra tooth blocking eruption? )
How do we deal with the early loss of deciduous teeth .
A- leave
B- leave
C- balance
D- balance.
E- leave.
How can an anterior crossbite affect the dentition?
It can cause:
Uneven wear on the incisal edge.
Recession- because the lower incisor is pushed forward out of the alevolar bone.
Discuss the dental impact of stopping a thumb sucking habit.
If you stop the habit before the age of 9- the teeth will erupt back into the normal position.
Discuss this primary molar and how we manage it.
This is an infra-occluded primary molar.
All of the other teeth around it continue to grow, but they stay in place.
managed-
If permanent successor is present-observe for 1 year.
No permanent successor- extract.
You extract the tooth if there is less than 1mm of crown showing.
How do we examine for ectopic canines.
Palpate a buccal cannine bulge from the age of 9
90% are palpable in the buccal sulcus.
Look for inclination of the 2s (caused by the permanent canine pushing against the 2s roots)
Look for mobility of the C or 2 (shows the canine is doing it’s job and resorbing the C away)
Look for colour change in the C or 2 (due to a loss of vitality or root resorption)
What do we want to know when looking at ectopic canines ?
The height of the canine.
How much does it cross over the lateral incisor.
What angle does the canine make (we want <30*)
How do we intercept ectopic canines?
We extract the C.
This treatment only works until the patient is 13.
What incisor angulation provides you with room to correct the teeth in an overjet.
<80 (Lowers) and >120 (uppers)
How can we intercept a class III.
Maxillary protraction e.g. reverse headgear
Camoflauge RA (give someone class I teeth but ignore the underlying skeletal relationship)
How can we intercept a class II?
Functional appliances e.g. a twin block - which forces the patient to posture forward.
Compare comprehensive and compromised treatment.
Comprehensive-
Full correction of the malocclusion:
Class I incisor relationship
Class I canine relationship
Class I molar relationship
Andrew’s 6 keys
Compromised treatment
Correct certain aspects of treatment and just accept others.
What is the lower labial segment and why do we need a stable angulation?
The lower labial segment is the incisors.
If this is not stable, the soft tissues (lip and tongue) will pu tpressure on the incisors resulting in relapse.
There is 0-4mm of space required in the lower lap, what do we do?
Stripping- interproximal enamel reduction.
Extract the 5s.
There is 4-8mm of space required in the lower lap, what do we do?
Extract the 5s (But only for small crowding as the mesial drift of the 6s will reduce the space you make)
Extract the 4s.
There is 8mm of space required in the lower lap, what do we do?
Extract the 4s
If we have extracted it the lower what do we do to the upper arch and why?
We extract in the upper arch to avoid a class II molar relationship.
We want the upper canines distal to the lower canines.
What is the IOTN?
This is the index of orthodontic treatment need which is used to determine the level of malocclusion. This decides which patients qualify for orthodontic treatment on the nhs.
At what IOTN grade do patients normally get offered NHS orthodontic treatment?
Grade 4 and Grade 5
Patients with grade 3 are decided case by case.
Compare the two components of the IOTN?
Aesthetic Component- This is where you select one of the 10 images which best matches the patients anterior teeth. Grade 5 and above is borderline need for treatment. Grade 8 and above require orthodontic treatment.
The Dental Health Component- this identifies the single worst occlusal trait.
Explain the acronym used for the Dental health Component of the IOTN?
M- Missing teeth (including congenital absence, ectopic and impacted teeth)
O-Overjet & reverse overjet
C- crossbites
D- Displacement of contact points
O- overbites.
What assumptions are made if you are doing the IOTN on a dental cast?
If there is a 3.5mm-6mm overjet you assume that the lips are incompetent and award grade 3a.
If there is a crossbite- assume a discrepancy of >2mm between RCP and ICP is present (Grade 4c)
If there is a reverse overjet- assume the patient has mastigatory or speech problems.
What can we use the dental health component ruler for?
Measuring positive overjet, negative overjet and displacement of the contact points or open bite.
What are the Li-MxP and the UI-Mxp angles
The li-Mxp is the angle between the lower incisors and the mandible.
The ui-max is the angle between the upper incisors and the maxilla.
What is the naso-labial angle?
This is the angle that indicates the position of the upper lip. It is formed by tangents of upper lip and columella of the nose.
It can be increased/ Average (100*) / Decreased.
What is the average value for the UiMxp
109+-6 degrees
What is the average value for the LiMxp
93 +-6 degrees
How do the LiMxP and UiMxp dictate treatment options
If the Ui-Mxp is >120 then we cannot procline the incisors anymore.
If the li-Mxp is <80 then we cannot retrocline the incisors anymore.
What is the mandibular plane?
A line from the mention to the gonion.
What is angle’s classification?
This is how we describe the canine relationship.
Name this angle’s classification
Class I-
When the upper 1st permanent molar mesiobuccal cusp occludes with the buccal fissure of the lower 1st permanent molar.
Name this angle’s classification
Class II.
When the mesiobuccal cusp of the 6 is anterior to the buccal fissure of the lower 6.
Name this angle’s classification
Class III.
When the mesiobucal cusp is posterior to the buccal fissure of the lower 6.
Name this angle’s classification
Class III.
When the mesiobucal cusp is posterior to the buccal fissure of the lower 6.
When would you not need to compensate a molar extraction and why?
When there is a class II molar relationship.
Occlusion of the molars with a premolar would prevent overeruption.
