Orthodontic Assessment

Question 1

When is the ideal age to carry out an orthodontic assessment?

Answer 1

Brief examination when the patient is 9 years old.
Comprehensive examination when the patient is 11-12 years old (once the premolars and canines have erupted).

Question 2

What factors should be included when taking a history of an ortho patient?

Answer 2

C/O- what is the patient concerned about?
Medical history
Dental history- regular attender? How often do they brush? Any trauma to the dentition? co-operation with previous treatment?
Social history- how far is it for patients to travel there? Motivation of parents and child.

Question 3

What are the 3 aspects that are examined during EO examination?

Answer 3

A-P
Vertical
Transverse

Question 4

What is assessed during A-P?

Answer 4

Skeletal assessment.
Determining the classification of the skeletal base.

Question 5

What is a class I skeletal base?

Answer 5

Maxilla 2-3mm in front of the mandible.

Question 6

What is a class II skeletal base?

Answer 6

Maxilla is greater than 3mm in front of the mandible.

Question 7

What is a class III skeletal base?

Answer 7

Mandible is in front of the maxilla.
Mandible is less than 2-3mm posterior to the maxilla.

Question 8

How do you determine the AP relationship?

Answer 8

Visual inspection
Palpate the skeletal bases

Question 9

What is assessed during the vertical examination?

Answer 9

Frankfurt-mandibular plane angle.

Question 10

What is the Frankfurt mandibular plane angle?

Answer 10

Frankfurt plane- inferior border of the orbital rim to the superior aspect of the external auditory meatus.
Mandibular plane- Gonion to menton.

Both lines should meet at the external occipital protuberance (back of the head).

Question 11

If the patient has a high FMPA, what does this mean?

Answer 11

The lines meet anterior to the back of the head.

Question 12

If the patient has a reduced FMPA, what does this mean?

Answer 12

The lines do not meet at the back of the head.

Question 13

What is assessed during the lateral examination?

Answer 13

Checking symmetry of the face and if the facial midline matches up with the dental midline.

Question 14

How do you assess the lateral aspect of the orthodontic examination?

Answer 14

Look at the patient from the front and from above.
Is cupid’s bow in line with the chin point of the mandible?

Question 15

After the 3 main features of the EO examination- what other factors should be assessed?

Answer 15

Lip trap
Competent or incompetent lips
Nasolabial angle
High, average or low smile line
Position of the tongue during swallowing
Lisping
Habits- digit sucking
TMJ
Mandibular displacement on closure

Question 16

What are the occlusal features of a digit sucking habit?

Answer 16

Proclaimed upper incisors
Retroclined upper incisors
Localised AOB or incomplete overbite
Narrow upper arch +/- Unilateral posterior cross bite

Question 17

What does it mean if the patient has competent lips?

Answer 17

Lips meet at rest, relaxed mentalist muscle.

Question 18

What may be a potential consequence of a lip trap?

Answer 18

Proclaimed upper incisors.
May lead to relapse of overjet if persists at end of treatment.

Question 19

What may be the consequence of an over-active lower lip?

Answer 19

Retroclination of lower incisors.

Question 20

What is associated with a patient that has a tongue thrust on swallowing?

Answer 20

Anterior open bite.

Question 21

What features should be examined intra-orally?

Answer 21

Oral hygiene adequate or inadequate?
Teeth present palpate for canines)
Caries
Restorations
BPE
Assess crowding/spacing/well aligned
Inclination of upper incisors (compared to Frankfurt plane) and lower incisors (compared to mandibular plane)
Rotations.
Incisor relationship
Canine relationship
Molar relationship
Overjet
Overbite
Cross bites
Centre lines

Question 22

What is the average inclination of upper incisors?

Answer 22

109 degrees +/- 6

Question 23

What is the average inclination of lower incisors?

Answer 23

93 degrees +/- 6

Question 24

What is the definition of a class I incisor relationship?

Answer 24

Lower incise edge occludes with or lies immediately below the cingulum plateau of the upper incisors.

Question 25

What is the definition of a class II div 1 incisor relationship?

Answer 25

Lower incisal edge occludes posteriorly to the cingulum plateau of the upper incisors.
Increased overjet
Upper incisors are either proclined or of average inclination

Question 26

What is the definition of a class II div 2 incisor relationship?

Answer 26

Lower incisal edge occluded posteriorly tot he cingulum plateau of the upper incisors.
Overjet is usually minimal or may be increased.Upper incisors are retroclined.

Question 27

What is the definition of a class III incisor relationship?

Answer 27

Lower incisal edges lie anterior tot he cingulum plateau of the upper incisors.
Overjet is reduced or reversed.

Question 28

For an average overbite, how much should the upper incisor cover the lower incisor?

Answer 28

1/3 of the crown.

Question 29

What is an incomplete overbite?

Answer 29

Upper and lower teeth do not contact but there is more than 1/3 of the lower incisor covered by the upper incisor.

Question 30

What is a class I molar relationship?

Answer 30

Mesio-buccal cusp of the upper first permanent molar occludes with the anterior buccal groove of the lower first permanent molar.

Class II- mesio-buccal cusp anterior to the anterior buccal groove

Class III- messy-buccal cusp posterior tot he anterior buccal groove

Question 31

What is a class I canine relationship?

Answer 31

Mesial slope of the buccal cusp of the upper canine occludes with the distal slope of the buccal cusp of the lower canine.

Class II- mesial slope is anterior to the distal slope.

Class III- medial slope is posterior to the distal slope.

Question 32

What special investigations might you want to request?

Answer 32

OPT
Maxillary anterior occlusal
Lateral Cephalogram

Question 33

Why might you want to request a lateral ceph?

Answer 33

Standardised lateral radiographs of the face.
Reproducible- patient positioned in a cephalostat.

Allows you to determine the starting point and end point of treatment, track progress throughout.

Eastman analysis.

Question 34

What is SNA, SNB and ANB?

Answer 34

SNA- sella, nasion and A point. Relates the maxilla to the anterior cranial base.
81 degrees +/- 3.

SNB- sella, nasion and B point. Relates the mandible to the anterior cranial base.
78 +/- 3

ANB- Relates the maxilla to the mandible.
3 degrees +/- 2

Question 35

For a class II skeletal relationship, what happens to the SNA, SNB and ANB?

Answer 35

SNA usually average
SNB is reduced
ANB increased- greater than 5.

Question 36

What is dento-alveolar compensation?

Answer 36

Dento-alveolar structures tend to try disguise the underlying skeletal discrepancy.

Forces from the lips, cheeks and tongue tend to incline teeth towards a position of tissue balance.

Question 37

How do you measure the upper and lower anterior face height?

Answer 37

Lower face height- soft tissue mentor to subnasale.
Upper face height- subnasale to glabella.
Lower face height should be 55% of the overall face height.

Question 38

What is the most common cause of a Class III skeletal base?

Answer 38

Maxillar hypoplasia.
But it can be due to mandibular prognathic or a combination of both.

Question 39

What is the most common cause of a Class II skeletal base?

Answer 39

Mandibular retrognathia.

Question 40

For a class III skeletal base, what happens to the SNA, SNB and ANB?

Answer 40

SNA is reduced if maxilla is deficient
SNB is average
ANB is reduced and potentially negative.