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Y3T3 Orthodontics > Class III Malocclusion > Flashcards

Class III Malocclusion Flashcards

1
Q

BSI Class III Incisal Relationship

A

Lower incisal edges are anterior to cingulum plateau of upper incisors

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2
Q

Angle’s Class III Classification

A

MB cusp of upper first permanent molar occludes distal to the MB groove of lower first permanent molar

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3
Q

Dental Problems of a Class III Malocclusion

A
  1. Localized crowding: Retroclined upper incisors and/or proclined lower incisors
  2. Pseudo-class III: CR-MI slide
  3. Missing lower second premolars, causing mesial drift or tilt of lower 6
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4
Q

What are Class III Skeletal Discrepancies?

A

Size: Maxilla too small or mandible too large

Position: Retrusive maxilla or prognathic mandible

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5
Q

Class III Skeletal Discrepancy can be exacerbated by?

A

Forward mandibular rotation relative to cranium

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6
Q

A forward mandibular rotation can result in?

A

Chin point more protrusive, with reduction in LAFH

Can be associated with a vertically deficient maxilla

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7
Q

Most common type of Class III Skeletal Relationship?

A

Maxillary retrusion and mandibular prognathism

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8
Q

Causes of Mandibular Prognathia

A
  1. Genetic
  2. Environmental: Posture of mandible, constant distraction of condyle from fossa → Growth stimulus → Pseudo-Class III malocclusion
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9
Q

Dental Components of Class III Skeletal Base

A
  1. Incisors, canines and molars Class III
  2. DAC: Proclined upper incisors and Retroclined lower incisors
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10
Q

Facial Profile of a Class III Skeletal base

A

Straight or concave but affected by shape of chin

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11
Q

Maxillary retrusion may correlate with?

A
  1. Deficient orbital rims
  2. Deficient cheek bones
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12
Q

Outline of the Cheekbone Contour

A

Anteriorly facing, curved line that starts from anterior to ear → extending forward through cheekbone point → anterior-inferiorly → ending at maxilla point adjacent to alar base of bone

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13
Q

What is the Maxilla point and Nasal base-lip contour used for?

A

Indicator of maxillary and mandibular skeletal anterior-posterior position

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14
Q

Outline of Nb-LC

A

Extends inferiorly from the maxilla point → Ending just below and lateral to mouth commissure

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15
Q

Define Maxilla point

A

Most anterior point of the continuum of cheekbone-nasal-lip contour

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16
Q

In maxillary retrusion, the maxilla point will be?

A

Straight or concave

17
Q

In mandibular protrusion, the Nb-LC will be?

A

Interrupted in the length of the upper lip

18
Q

What is a Pseudo-Class III malocclusion?

A
  1. CR-MI slide

Premature contact between incisors at CR → Forward displacement of mandible to disengage incisors → permit further closure into posterior occlusion in MI

19
Q

Skeletal Characteristics of Pseudo-Class III Malocclusion

A
  1. Decreased midface length
  2. Forward position of mandible with normal mandibular length
20
Q

Dental Characteristics of Pseudo-Class III Malocclusion

A
  1. 75% showed a mesial step at MI and flush terminal plane at CR (primary molars)
  2. Retroclined upper incisors and proclined lower incisors
  3. Anterior crossbite
  4. Teeth in traumatic occlusion may present with gingival recession
21
Q

Soft Tissue Characteristic of Pseudo-Class III Malocclusion

A

Retrusive upper lip

22
Q

Clinical Significance of Pseudo Class III Malocclusion

A

A functional malocclusion may develop into a true mandibular prognathia via adaptive remodeling

23
Q

Treatment Options For Class III Malocclusions

A

Phase I (Early) treatment in mixed dentition)

Phase 2 treatment in permanent dentition

or Single-phase comprehensive treatment in permanent dentition

24
Q

Phase 1 Treatment in Mixed dentition involves

A

Growth modification before suture fusion

Dental correction

25
Q

What are the potential benefits of early treatment?

A
  1. Guide skeletal growth to improve skeletal discrepancy → Simplify and shorten Phase 2 treatment
  2. Prevent progressive/irreversible skeletal, dental or soft-tissue changes
  3. Improve function
  4. Improve facial and dental esthetics → Psychosocial benefits
26
Q

What do we do in Phase 1 treatment?

A

Growth modification

  • Growing patients, reverse-pull headgear or chin cup
  • Best performed < 8-10 years old

Dental correction
- To correct dental crossbites
- Removable appliance with auxillary spring
- Maxillary lingual arch with finger springs
- Sectional fixed appliances

27
Q

What do we do in the Phase 2 treatment?

A

Comprehensive orthodontic treatment

Skeletal discrepancies: Orthodontic camouflage or Orthognathic surgery

28
Q

What is orthodontic camouflage in Class III?

A

Procline upper incisors and retrocline lower incisors using Class III elastics

Non-extractions or Extract
- Lower 4s
- Upper 5s and lower 4s

29
Q

Indications of Orthognathic Surgery

A

Non-growing patients + Severe skeletal problems

Y3T3 Orthodontics (11 decks)

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