Class III Malocclusion Flashcards
BSI Class III Incisal Relationship
Lower incisal edges are anterior to cingulum plateau of upper incisors
Angle’s Class III Classification
MB cusp of upper first permanent molar occludes distal to the MB groove of lower first permanent molar
Dental Problems of a Class III Malocclusion
- Localized crowding: Retroclined upper incisors and/or proclined lower incisors
- Pseudo-class III: CR-MI slide
- Missing lower second premolars, causing mesial drift or tilt of lower 6
What are Class III Skeletal Discrepancies?
Size: Maxilla too small or mandible too large
Position: Retrusive maxilla or prognathic mandible
Class III Skeletal Discrepancy can be exacerbated by?
Forward mandibular rotation relative to cranium
A forward mandibular rotation can result in?
Chin point more protrusive, with reduction in LAFH
Can be associated with a vertically deficient maxilla
Most common type of Class III Skeletal Relationship?
Maxillary retrusion and mandibular prognathism
Causes of Mandibular Prognathia
- Genetic
- Environmental: Posture of mandible, constant distraction of condyle from fossa → Growth stimulus → Pseudo-Class III malocclusion
Dental Components of Class III Skeletal Base
- Incisors, canines and molars Class III
- DAC: Proclined upper incisors and Retroclined lower incisors
Facial Profile of a Class III Skeletal base
Straight or concave but affected by shape of chin
Maxillary retrusion may correlate with?
- Deficient orbital rims
- Deficient cheek bones
Outline of the Cheekbone Contour
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
What is the Maxilla point and Nasal base-lip contour used for?
Indicator of maxillary and mandibular skeletal anterior-posterior position
Outline of Nb-LC
Extends inferiorly from the maxilla point → Ending just below and lateral to mouth commissure
Define Maxilla point
Most anterior point of the continuum of cheekbone-nasal-lip contour
In maxillary retrusion, the maxilla point will be?
Straight or concave
In mandibular protrusion, the Nb-LC will be?
Interrupted in the length of the upper lip
What is a Pseudo-Class III malocclusion?
- CR-MI slide
Premature contact between incisors at CR → Forward displacement of mandible to disengage incisors → permit further closure into posterior occlusion in MI
Skeletal Characteristics of Pseudo-Class III Malocclusion
- Decreased midface length
- Forward position of mandible with normal mandibular length
Dental Characteristics of Pseudo-Class III Malocclusion
- 75% showed a mesial step at MI and flush terminal plane at CR (primary molars)
- Retroclined upper incisors and proclined lower incisors
- Anterior crossbite
- Teeth in traumatic occlusion may present with gingival recession
Soft Tissue Characteristic of Pseudo-Class III Malocclusion
Retrusive upper lip
Clinical Significance of Pseudo Class III Malocclusion
A functional malocclusion may develop into a true mandibular prognathia via adaptive remodeling
Treatment Options For Class III Malocclusions
Phase I (Early) treatment in mixed dentition)
Phase 2 treatment in permanent dentition
or Single-phase comprehensive treatment in permanent dentition
Phase 1 Treatment in Mixed dentition involves
Growth modification before suture fusion
Dental correction
What are the potential benefits of early treatment?
- Guide skeletal growth to improve skeletal discrepancy → Simplify and shorten Phase 2 treatment
- Prevent progressive/irreversible skeletal, dental or soft-tissue changes
- Improve function
- Improve facial and dental esthetics → Psychosocial benefits
What do we do in Phase 1 treatment?
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
What do we do in the Phase 2 treatment?
Comprehensive orthodontic treatment
Skeletal discrepancies: Orthodontic camouflage or Orthognathic surgery
What is orthodontic camouflage in Class III?
Procline upper incisors and retrocline lower incisors using Class III elastics
Non-extractions or Extract
- Lower 4s
- Upper 5s and lower 4s
Indications of Orthognathic Surgery
Non-growing patients + Severe skeletal problems
