Class 3 Malocclusion Flashcards
Class 3 Malocclusion definition
- Lower incisors occlude anterior to the cingulum plateau of upper central incisors
What percentage of population?
3% Caucasians
5% population
Feature of class 3 Malocclusion
- Skeletal
- Soft tissue
- Dentoalveolar and occlusal
- Facial growth
Skeletal AP
- class 3
- maxilla retrusion is most common factor effect 60% of cases.
- low cranial base angle, forward position of mandible
Skeletal vertical
- Average , increased and reduced
Skeletal - Transverse
- large mandible or small maxilla (hypo plastic) or combination of both.
- short and narrow max cause cross bites.
- Asymmetries due to,
1- Crossbite and occlusal displacement.
2- Growth
Soft tissue
- Upper to lower lip anterior oral seal
Not involve in Aetiology but encourage Dento alveolar compensation. - Tip teeth to compensate SK relationships
- Upper to lower lip anterior oral seal
- Increase vertical skeletal proportion, tongue ti lip seal
Dentoalveolar compensation.
A mechanism through which soft tissues (lips, tongue, cheeks) produce more class 1 incisor relatiohship when AP skeletal pattern is SK 2 or SK3.
Dentoalveolar Feature
Dentoalveolar compensation
- Upper incisor proclined
-lower incisor retroclined
- class 3 molar
- positive or negative OJ
- Decreased OB
Occlusal Features
Overjet
-Can be + OJ and -OJ
- displacement from E-E
Overbite
- depends on vertical discrepency
Buccal cross bite
- uni / bilateral
- broad mand to narrow max.
Occlusal and Dentoalveolar Feature
- Maxilla Retrognathia - crowding
- Mandible Prognathism- Spaced/ aligned/ crossbite
Facial Growth
Why facial growth matters?
- tends to Unfavourable
- wait until growth ends for treatment
- Mandible becomes more Prognathic
- Vertical growth reduce overbite
- Dentoalveolar compensation - Maintain positive Overjet
Timing of treatment
Mixed Dentition -
- Crowded upper lateral incisors
- Anterior crossbite with displacement
- Buccal crossbite with displacement
Permanent
- orthodontic alone
- orthodontics and surgery
Tteatment Planning on basis of?
- Patient concern
- Skeletal relationship severity
- Degree of overbite
- Growth Age, sex, facial pattern
Treatment planing Aim
Occlusal feature
- Normal or increased overbite
- able to achieve edge to edge
- level and align arches
- correct buccal segment relationships
- Upper incisor - retroclined / average
- lower incisor - Proclined/ average
- Refuced AOB
- No anterior displacement
- Significant Dentoalveolar compensation
Poor Prognosis what happens?
less favourable facial balance
Treatment planing - Mixed Dentition (crowding)
- Extract C’s to aling Incisors
Treatment planing - Permanent dentition ( crowding )
- If upper arch Xtn , tend to extract Upper5s’
- Expansion of upper arch by URA with expansion screw - provide space but reduce overbite
What movement should avoided in adult?
Distal movement and use of headgear
Treatment aim or Options?
-Accept (+/- interceptive Xtn)
- Procline Upper labial segmen
- Procline upper labial segment +retroclined lower labial segment.
- Surgery
Treatment Modalities or options?
-Removable appliances
- Functional appliances
- Fixed appliances
- Reverse headgear
Mixed dentition treatment
- incisors X cross bite tx?
- Extract C’s to create space for upper laterals
- Fit URA to Proclined upper incisors
- when incisors over the bite Remove posterior bite plane.
- Once overbite corrected it should not need retention because overlap of overbite protect retention
How do we maintain result ?? In mixed dentition
- Anterior crossbite- Protect by correction of overbite
- Posterior crossbite- Maintain with URA until Permanent dentition
Permanent Dentition Tx
-Orthodontic Camouflage
- Growth slowing down
- Proclination of upper incisors
- Proclination of upper incisors + Proclination of upper incisors with retrolcination of lower incisors
- Potentially good overbite
When do we do Proclination of Upper labial segment - PERMANENT teeth?
- Class 1 / Mild class 3 SK
- Upper incisors not proclined
- Good overbite
- Able to Edge to edge incisors before displacing forward
- Removable / fixed appliances
When do we do Proclination of ULS and Retroclination of LLS?
- Mild / moderate SK class 3 patter
- Reduced overbite
- Xtns in lower arch
- Fixed appliances/ Class 3 elastics / revers pull headgear
Severe Skeletal Problems? And tx
- Growth complete or slow down
- Orthodontic correction not possible
- ANB <4 degree
- LI- Mnp < 83 degree
- Patient unhappy with profile.
- Treat using orthodontic and surgery
Orthognathic Surgery Aim?
- Decompensate incisors prior surgery
- Co- ordinate arches
- Patient will look worse before surgery
Types of Orthognathic surgery
Depend on Sk pattern
-Small maxilla needs advancement
- Large mandible needs set back
-Combination of both - Bi- maxillary surgery
