Ortho - Malocclusion Flashcards
What 3 things can you do to reduce the levels of radiation from a lateral ceph?
Triangular collimator
Thyroid collar
Rare earth/ LANEX screen
What film speed is used on a lateral ceph?
60-70kV
What do the letters in SNA stand for?
Sella tursica - Which is a part of the sphenoid bone which holds the pituitary gland.
Nasion
A - the deepest concavity of maxillary alveolus
In a class 1 patient what are the SNA, SNB and ANB values on a lateral ceph?
SNA - 81 +- 3
SNA - 78 +- 3
ANB - 3+- 2
What is the Eastman correction?
This is to address inaccuracies.
For every degree the SNA value falls below 81 half a degree should be added to ANB and vice versa
What happens to the values of SNA, SNB and ANB on a lateral ceph, in a class ll patient?
SNA - stays the same
SNB - decreases < 78
ANB - increases >5
What happens to the values of SNA, SNB and ANB on a lateral ceph, in a class lll patient?
SNA - decreases
SNB - stays the same increase if mandible prognathic.
ANB - < 1 or negative
What is dento-alveolar compensation?
This is when dentoalveolar structures try and disguise skeletal discrepancies.
It forces the lips cheeks and tongue teeth towards a position of soft-tissue balance.
What is a common sign of dento-alveolar compensation?
Incisors being tipped towards one and other
What is the normal value for the FMPA on a lateral ceph?
27 degrees +- 4
What is the anterior face height ratio value normally (AFHR)
55% to the lower 45% to upper
In a patient with a long face what happens to the FMPA and AHFR?
FMPA > 31 degrees
LFHR > 55% of total face height
How does mandible grow in a patient with “long face”? and how does it present?
mandible grows down and backwards
Patients struggle to keep lips together.
Presents with shallow bite and anterior open bite.
May need surgical intervention
In a patient with a short face what happens to the FMPA and AHFR?
FMPA - < 23 degrees
LHFR < 55%
Presents with very deep bite
What can arch width discrepancies cause?
Posterior unilateral or bilateral crossbites
How can you expand the upper arch?
URA
mid-palatal screw
What is mandibular displacement? and what is it associated with?
This is when the teeth contact cusp to cusp but in order to achieve ICP, the mandible is displaced to one side.
Associated with TMD
What is transverse dento-alveolar compensation?
This is when the soft tissues mould the alveolar process during growth to maintain occlusion.
This disguises skeletal discrepancies
What are some types and reasons for facial asymmetry?
Dental cause - mandible is displaced due to a unilateral crossbite.
True Mandibular asymmetry, asymmetric growth of the mandible (Hemi-mandibular hyperplasia)
Hemifacial microsomia - incomplete growth of one side of the mandible
Dentoalveolar disproportion relates to discrepancies within the size of teeth and jaw, what can this cause?
Overcrowding - macrodont and small jaw
space - hypodontia and big jaw
What are the 5 broad categories of local causes for malocclusion?
1) Variation in tooth number
2) Variation in tooth size
3) Abnormal tooth position (ectopic)
4) Local abnormalities of soft tissues
5) Local pathology
What is a supernumerary? and where is it most commonly found?
An extra tooth
Found in males more and the anterior region of the maxilla
What are the 4 types of supernumerary?
COST Conical Odontome Supplemental Tuberculate
What is the name for a supernumerary found between the two upper central incisors?
mesiodens
What is a conical supernumerary? How would you treat it?
It is a small, thin, peg-shaped tooth found close to the midline
Ex if erupted, If not erupted then can leave if causing no problems
Tuberculate supernumerary? what do they look like, what can they cause and how do you treat them?
Barrel-shaped
Can cause the upper incisors to not erupt.
Ex
What are the two types of odontome? and how do you treat?
Compound and complex
A compound is a discrete tooth-like structure in an organised form.
Complex a random disorganised mass
Surgical Ex
What is a supplemental supernumerary?
This is an extra fully formed normal tooth.
What is hypodontia?
Developmental absence of one or more teeth.
Commonly affects the 2’s and 5’s
The teeth present are often smaller and more slender in shape so need to be built up anyway.
How long in exfoliation of a contralateral tooth should you wait before alarm bells start ringing?
6 months or more between contralateral tooth eruption means something is wrong.
4 Reasons for a retained primary tooth?
No permanent successor
Ectopic or dilacerated successor
Infra-occluded - Anklyosed to bone (submerged)
Delayed dental development
What are the two treatment options for an absent successor?
Ex - if there is crowding and allow for spontaneous space closer
Keep tooth for as long as possible and build it up if it has a good prognosis
Why do infra-occluded primary molars appear submerged?
As the teeth around them are growing. But the primary molar is fused to the bone.
What is a possible problem with submerged primary molars?
They can allow caries to develop between the mesial of 6 and distal of them. As this area is difficult to clean.
How are submerged primary molars graded?
Mild - <2mm down from the occlusal table
Moderate - Within the occlusal gingival margins of IP contact
Severe - Below the IP contact point
Treatment of a submerged primary molar with and without a successor?
With - Usually resolve itself, If severe case then Ex as can cause caries
Without - keep if the tooth has a good prognosis as can place onlay.
If crowded then consider Ex for space
4 reasons for early loss of primary teeth?
Trauma
Periapical pathology
Caries
Resorption by successor
What is the biggest problem associated with the early loss of primary teeth?
Crowding
The effect of early loss in the primary dentition is dependant on?
Which tooth loss
When the tooth was lost
Levels of crowding
What is a balancing Ex?
When you remove a tooth in the same arch on the opposing side to prevent a midline shift.
What is a compensating Ex?
When you remove a tooth in the opposing arch on the same side.
This is done with upper teeth if a lower has already been Ex to minimise over eruption and therefore, effect on occlusion
For loss of one canine, what would you consider?
Balancing Ex
For movement of molars, in which arch is space more easily closed?
The upper arch.
7’s can easily close the gap left by 6’s.
What are the variations in tooth size?
Macrodont
Microdont
Abnormal from
Where are ectopic canines usually found?
Palatally - 80%
When should you start palpating in the buccal mucosa of ectopic canines as early intervention is extremely important?
9 years old
What are some clinical signs associated with ectopic canines?
Mobility of the C’s and 2’s
colour of the 2’s due to loss of vitality
Fell and palpate for lumps and bumps
The inclination of the 2’s
How might you carry out a radiographic assessment to see ectopic canine and work out where they are?
Take 2 radiographs
OPT and anterior oblique occlusal
If in the ABO the canine is now closer to the apex of the 2’s then it is palatally placed
This is parallax technique
What are the Tx options for ectopic canines?
Ex the Cs and allow them to come into space
Leave the 3’s and observe for any pathology or cysts
Surgical Ex of 3’s and ortho using fixed appliance
Ex 3’s
What are the local abnormalities of soft tissues to cause malocclusion?
Thumb and digit sucking
Tongue thrusting
Labial frenum
What can the persistence of a labial frenum cause?
midline diastema
What does thumb-sucking cause?
AOB
proclined uppers
Retroclined lowes
smaller upper jaw so unilateral posterior crossbite
Local pathologies that affect occlusion?
Caries
Cysts
Tumour
