Orthodontic Assessment

Question 1

Permenent teeth eruption ages

Answer 1

Rule - contralateral must erupt withing 6 months of other and mandibular before maxillary

• 6s : 6-7yo (root formation 9-10)
• 1s : 6-8yo
• 2s : 7-8yo
• 4s : 9-11yo
• 3s : 10-11yo
• 5s : 10-12yo
• 7s : 12yo
• 8s : >17-19yo

Question 1

When is an orthodontic assessment carried out (3)

Answer 1

1. Minor assessment aged 9 (check if canines palpable)
2. comprehensive assessment aged 11-12 (premolars and canines erupting)

Question 2

what are andrews 6 keys of occlusion

Answer 2

1. crown angulation (mesial/distal)
2. crown inclination
3. rotations
4. spaces
5. flat occlusal plane
6. upper 6 distal of disto buccal cusp occludes with mesial of lower 7 mesiobuccal cusp
7. teeth correct size (extra)

Question 3

Contra-indications to orthodontic tx (4)

Answer 3

1. nickle or latex allergy
2. epilepsy
3. Drugs : bisphosphonates / cancer tx and calcium channel blockers (antihypertensives)
4. MRI imaging required

Question 4

what are habits effecting occlusion

Answer 4

1. tongue thrust (AOB, spaces, proclines uppers, relapse)
2. nail biting (crooked and gaps)
3. lower lip sucking (retro and procline)
4. digit habit
   * 13-14 latest teeth will reposition
   * proclined uppers, retroclined lowers
   * AOB
   * unilateral cross bite (narrowed arch and jaw displacment)

Question 5

avg. inclination of incisors and max you can change them for a class III Reverse OJ

Answer 5

• uppers : 109 degrees (120-proclined)
• lowers : 93 degrees (80-retroclined)

Question 6

skeletal class defintions

Answer 6

1. mandible 2-3mm behind maxilla
2. mandible >3mm behind maxilla
3. mandible in front of maxilla / <2mm in front

Question 7

how to assess vertical dimension of the face

Answer 7

FMPA
* border of mandible and frankfort plane liens extended back
* normal : 27 +/-4 degrees (meet at occipital protruberance)

Question 8

how to assess transverse plane of the face

Answer 8

symmetry face on

Question 9

incisor classification definitions

Answer 9

1. lower incisor occludes with cingulum of upper incisor
   * class II div 1 - behind cingulum with protrusion (OJ)
   * class II div 2 - behind cingulum with retroclination (over bite)
   * class III -

Question 10

canine classification description

Answer 10

1. top tip in region of distal of lower
2. upper tip in same plane as lower tip
3. upper tip distal to distal surface of lower

Question 11

molar classification descriptions

Answer 11

• class I = mesio palatal cusp of upper 6 occludes with centre fissure of lower 6
• Class II Half unit = mesiopalatal cusp occluding with mesial of lower 6 (cusp to cusp)
• class II full unit = mesiopalatal cusp of upper mesial to lower 6
• class III - mesiopalatal cusp of upper 6 occludes distal to lower 6 (half and full unit?)

Question 12

grades of crowding and their tx

Answer 12

• mild = 0-4 mm (No XLA / XLA 5)
• moderate = 4-8 (XLA 5 / 4)
• severe = >8 (XLA4)

• 4 gives more space due to 5 space being lost due to 6 mesial drift

Question 13

compensating and balancing extractions

Answer 13

• compensating = if XLA lower, must XLA upper (NOT vv) - teeth stay in occlusion as move, upper would have protruded
  *balancing = XLA tooth on opposite side of arch (maintain symmetry - prevent midline shift)

Question 14

best ages for functional appliances

Answer 14

growth spurts
* prepubertal = ?
* pubertal = (W 8-13 / M 10-15)

Question 15

run through a whole orthodontic assessment

Answer 15

1. C/O
2. MH (conditions, allergy, medication, visit gp/doctor/surgery)
3. DH (brushing, flossing, mouthwash, toothpaste, tx experience, complinace, regular attender, truama)
4. SH (habbits, how get here, where stay, parents work, school exams, diet)
5. E/O (skeletal, vertical, transverse, LAFH, nasolabial angle, lips - competent / trap - smile line, pathology)
6. I/O (teeth present, poor prognosis, OH, BPE, crowding, inclination of incisors, rotations, incisor / canine / molar class, OJ, OB/AOB, crossbites, centre lines
7. IOTN (dental health and aesthetics component)
8. summary (patient info, class … incisors on a class … skeletal base, main issues are: …)
9. other = radiogrpahs

Question 16

what are the two types of causes of malocclusion

Answer 16

1. skeletal (maxilla and mandible)
   * size compared to each other
   * positioning of mandible (hemi or bilateral cross bites)
   * size causing little space for teeth
   -
   -
2. local (teeth)

Question 17

difference bwtween unilateral and bilateral cross bites

Answer 17

• unilateral = mandibular displacement when cusp to cusp occlusion
• bilateral = hemimandiblar hyperplasia, condylar hyperplasia or class III skeletal base

Question 18

Local causes of malocclusion

Answer 18

1. teeth (number, varied shape/size, positioning)
2. soft tissue (tongue thrust, digit habit, labial frenulum, lip trap)
3. pathology (cyst, caries, tumour)

Question 19

what are the local causes of malocclusion caused by the teeth

Answer 19

1. number of teeth
   * supernumary (odontome, conical, tuberculate and supplemental)
   * hypodontia (common upper laterals / second premolars)
   * retained primary (abscent successor, ectopic/dilacerated, infraoccluded, delayed development, pathology / supernumary)
   * early primary tooth loss
   * unscheduled loss of permanent teeth i.e. 6s
   -
   -
2. tooth size / shape
   * macrodontia
   * microdontia
   * abnormal form (peg, dens in dente, fused, talon, dilaceration, acessory cusps and ridges)
   -
   -
3. abnormalities of tooth position
   * ectopic or transposition
   * ectopic = 8s, 3s, 6s, 1s

Question 20

extraction of lower 6s

Answer 20

• check prognosis around 8-9yo
• upper arch less important
• too early / distal drift of 5
• too late poor space closure by 7
• ideally = at time of development of the root where furcation starting to be formed