Lab

Question 1

What grades qualifiy for NHS treatment?

Answer 1

Grade 4 or grade 5. Grade 3’s will usually be judged on an individual basis, but may be available if the appearance of the teeth, jaw or face is a concern.

Question 2

What two components is the I.O.T.N composed of?

What are they

Answer 2

AC
▪ The Aesthetic component of the IOTN is a scale of 10 colour photographs showing different levels of dental attractiveness.
▪ The grading is made by the orthodontist matching the patient to these photographs.

DHC
▪ The DHC records the various occlusal traits of a malocclusion that would increase the morbidity of the dentition and surrounding structures.
▪ There are 5 grades, ranging from Grade 1 (No treatment need) to Grade 5 (Significant need for treatment).

Question 3

What DHC score and AC rating qualify for NHS treatment?

Answer 3

a DHC score of 3 or above and a AC rating of 6 or above then treatment under the NHS is permissible.

Question 4

In AC what do grades mean?

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Answer 4

GRADE1,2,3& 4
No or minor requirement for treatment

GRADE 5, 6 & 7
Moderate/borderline need for treatment

GRADE 8, 9 & 10
Requires orthodontic treatment

Question 5

What does higher up on the scale mean in DHC?

Answer 5

• The higher up the scale, the more severe the malocclusion.
• If 2 or more occlusal anomalies are identified and have the same DHC grade, the secondary letters are used to identify which occlusal anomaly is higher in the scale.

Question 6

What acronym can be used in remembering the hierarchial scale?

Answer 6

M - missing teeth (including congenital, ectopic and impacted)
O - overjets (including reverse overjets)
C - crossbites
D - displacement of contact points
O - overbites (including open bites)

Question 7

What is dental cast protocol in the absence of additional clinical information

Answer 7

1 - Overjets 3.5mm-6mm on Dental Casts
Assume the lips are incompetent and award the Grade 3a.
2 - Crossbites on Dental Casts
Assume a discrepancy between RCP and ICP of than 2mm is present and award a grade 4c.
3 - Reverse Overjets on Dental Casts
Assume that masticatory or speech problems are present.

Question 8

What is ms?

Answer 8

ms – masticatory and/or speech difficulties

Question 9

What to grade borderline cases?

Answer 9

If an occlusal trait is borderline, the lower DHC grade should be recorded.

Question 10

What does buccal occlusion assess in IOTN?

Answer 10

Checks if canines, premolars, and molars have a full Class I relationship.
If any segment deviates from full interdigitation → DHC grade = 2.g

Question 11

When is a tooth considered in crossbite for IOTN?

Answer 11

Anterior: 1–3 incisors in lingual occlusion

Posterior: Cusp-to-cusp or full crossbite

Question 12

How is crowding classified in IOTN?

Answer 12

If space between teeth is <4 mm, tooth is impacted.
DHC grade = 5.i

Question 13

What defines contact point displacement in IOTN?

Answer 13

Measured between anatomical contact points when teeth deviate from alignment.
Exclude displacements between deciduous teeth or mixed dentition.

Question 14

When is a tooth classified as impacted or impeded eruption?

Answer 14

Tooth unerupted due to crowding or obstruction by adjacent tooth → 5.i

Tooth erupted but tipped against adjacent tooth → 4.t

Question 15

How is overjet recorded in IOTN?

Answer 15

Measured parallel to occlusal plane, from labial aspect of most prominent incisor.
Reverse overjet recorded if all lower incisors are in lingual occlusion.

Question 16

Are submerging deciduous teeth recorded in IOTN?

Answer 16

No — unless only the tooth’s cusps are visible and adjacent teeth have drifted together → 5.s

Question 17

How are rotated teeth handled in IOTN?

Answer 17

Contact point displacements between rotated teeth not recorded.
Discrepancy between RCP & ICP due to cuspal interference is graded like a crossbite.

Question 18

How is spacing recorded in IOTN?

Answer 18

Not generally recorded unless due to contact point displacement.
Spaces from extracted teeth are ignored.

Question 19

What does path of closure refer to in IOTN?

Answer 19

Discrepancies between ICP and RCP are recorded similarly to crossbites.

Question 20

Design a URA to retract canines given: 1st premolars extracted, 13 buccally placed, 23 in line, deep traumatic overbite, 6mm overjet.

Answer 20

Active: Palatal finger springs on 13 and 23 (0.5mm HSSW) to retract canines.

Retentive: Adams clasps on 16+26 and 14+24 (0.7mm HSSW).

Anchorage: All teeth except canines (good anchorage with premolars extracted).

Baseplate: Self-cure PMMA with anterior bite plane (ABP) to reduce deep overbite.

Aim: To retract 13 and 23 palatally and reduce deep traumatic overbite.

Question 21

What wire gauge is used for transpalatal arches and how are they attached to teeth?

Answer 21

0.9mm HSSW (hard stainless steel wire). Attached to first permanent molars using orthodontic stainless steel bands by spot welding or soldering.

Question 22

What are the three uses of a transpalatal arch?

Answer 22

Anchorage, rotation (of molars), and limited widening or contraction (of the arch).

Question 23

What is the sole primary use of a palatal arch with Nance button and how is it constructed?

Answer 23

Primary use is anchorage. Constructed from 0.9mm HSSW in a rigid fixed manner requiring minimal adjustment, attached to first permanent molar bands by spot welding/soldering.

Question 24

What are the seven uses of a Quadhelix appliance?

Answer 24

Bilateral expansion, asymmetrical expansion, fan style expansion, rotation of molars, expansion in cleft palate, modified to procline incisors, and assist in habit breaking.

Question 25

How is a Quadhelix constructed and what makes it highly versatile?

Answer 25

Constructed from 0.9mm HSSW in rigid fixed manner with minimal adjustment needed, attached to first molar bands by spot welding/soldering. Versatile because it can be adapted for multiple scenarios including various types of expansion, rotation, and habit breaking.

Question 26

Compare the type of tooth movement achieved by fixed versus removable orthodontics.

Answer 26

Fixed orthodontics achieve bodily tooth movement (moving root and crown together). Removable orthodontics achieve tipping movement only (crown moves more than root).

Question 27

List five advantages of fixed orthodontics.

Answer 27

Bodily tooth movement, rotations easily fixed, can be used in lower arch as easily as upper, individual force applied to every tooth, not easily removed by patient, works 24/7, precise 3D movement, less invasive of tongue space, and minimal palatal coverage.

Question 28

List five disadvantages of fixed orthodontics.

Answer 28

Increased risk of root resorption, decalcification, can be perceived as visually unattractive, can cause soft tissue trauma, cost, requires high motivation for oral hygiene, poor anchorage, requires highly trained specialist, and etching teeth is destructive.

Question 29

List five advantages of removable orthodontics.

Answer 29

Tipping of teeth, excellent anchorage, generally cheaper than fixed, shorter chairside time, oral hygiene easier to maintain, non-destructive to tooth surface, less specialised training required, easily adapted for overbite reduction, and can achieve block movements.

Question 30

List four disadvantages of removable orthodontics.

Answer 30

Less precise control of tooth movement, easily removed by patient, generally only 1-2 teeth moved at one time, requires specialist technical staff to construct, and rotations very difficult to correct.

Question 31

Why is anchorage considered excellent with removable appliances but poor with fixed appliances?

Answer 31

Removable appliances use the baseplate and multiple clasps engaging many teeth to resist unwanted movement. Fixed appliances have less anchorage control as forces are applied directly to individual teeth without the same resistance from a large baseplate structure.

Question 32

What is meant by "block movements" as an advantage of removable orthodontics?

Answer 32

The ability to move multiple teeth together as a single unit (a block), such as retracting all anterior teeth simultaneously, which is facilitated by the baseplate connecting them.

Question 33

What are the key considerations for bracket positioning in fixed orthodontics?

Answer 33

Precise vertical and horizontal positioning on each tooth, correct angulation and torque, consistent height from incisal edge/cusp tips, and consideration of tooth anatomy and final desired position (specific measurements vary by tooth type).

Question 34

What is a laceback and when would it be used in fixed orthodontics?

Answer 34

A ligature wire extending from anterior brackets back to molar tubes/bands to provide anchorage and prevent forward movement of molars during space closure or retraction of anterior teeth.

Question 35

What are the different types of ligatures used in fixed orthodontics?

Answer 35

Elastomeric ligatures (colored elastic modules), stainless steel ligature wire, and power chains (connected elastomeric ligatures for space closure).

Question 36

What is the purpose of an anterior bite plane when retracting canines with a URA?

Answer 36

To reduce a deep traumatic overbite by disengaging the posterior occlusion, allowing the posterior teeth to over-erupt and the overbite to reduce while canine retraction occurs.

Question 36

Why would you use 0.9mm HSSW for palatal arches but 0.5mm HSSW for Z-springs?

Answer 36

0.9mm wire provides rigidity needed for anchorage appliances (transpalatal arch, Nance button, Quadhelix) that must resist deformation. 0.5mm wire provides the flexibility and spring action needed for active tooth movement components like Z-springs.

Question 37

What are the three main types of orthodontic retainers?

Answer 37

1) Conventional Removable Retainers (Hawley-type with wire and acrylic) 2) Thermoplastic Retainers (clear, vacuum-formed) 3) Bonded Retainers (fixed wire bonded to lingual surfaces)

Question 38

Why do all the teeth come down in line with the gold standard rather than the gold standard tooth going up?

Answer 38

It’s easier to extrude teeth than it is to intrude them → wire provides enough force to facilitate extrusion but not intrusion

Question 39

Why is nickel titanium particularly useful for ortho arch wires?

Answer 39

It has good shape memory - so it can be manipulated and it will want to return to its original shape.

Question 40

What determines the final positioning of teeth?

Answer 40

Brackets positioning: If the brackets in a different angle then the wire can be held at a different angle

Question 41

What are the parts of a fixed appliance?

Answer 41

- **Ligature = Holds wire, prevents displacement** - **Archwire = Applies the force** - **Brackets = facilitates the interface between the wire and tooth** - *Metal band = Often used on 6s or 7s if you have an additional component added on (not used as much)* - *Elastic Hooks & Rubber bands = Used to try help with occlusion*