vertical and transverse malocclusion Flashcards
What are the skeletal causes of mandibular buccal crossbite
can be due to absolute or relative transverse discrepancy
absolute discrepancy due to
- Mismatch in intermolar width of arches vs population age norms/of maxilla vs mandible, arch perimeter
- Maxillary constriction (get increased curve of Wilson due to DAC, increased buccal corridors)
- Wide mandible
relative discrepancy due to
- Anteroposterior relationship
- Skeletal asymmetry
What are the effects of non nutritive sucking
- Buccal cross bite
- Increased overjet
- Anterior open bite
how does non nutritive sucking lead to buccal cross bite
Tongue lowered and no longer in contact with upper posterior teeth —> decreased lingual pressure
Buccinators activated, exert strong palatal pressure on upper posterior teeth
how does non nutritive sucking lead to AOB
- Thumb inhibits eruption of anterior teeth
- Prolonged opening of mouth to accommodate thumb —> compensatory eruption of the posterior teeth
Non skeletal etiology of buccal crossbite
- Non nutritive sucking
- Macroglossia
- Lateral tongue spread
- Mouth breathing (questionable)
- Cleft lip/palate repair –> scarring secondary to surgery restrict transverse growth of maxilla
- Lateral functional shift
Define AOB
No vertical overlap at all between anterior teeth when posterior segments are in occlusion
What are the causes of AOB
- Skeletal
- Increased vertical growth of the maxilla
- Condylar degenerative disease eg idiopathic condylar resorption, juvenile rheumatoid arthritis
- Trauma —> TMJ ankylosis
- Cleft alveolus
- Dental
- Bimaxillary protrusion
- Impeded eruption
- Ankylosis of traumatised tooth
- Soft tissues
- Non nutritive sucking habits
- Forward resting tongue posture (inhibit eruption)
Characteristics in skeletal AOB patient
- Downward and backward mandibular rotation
- Vertical maxillary excess
- Upward tipping of palatal plane anteriorly
- Excess vertical growth of maxillary posterior dentoalveolar complex
- Short ramus
- Antegonial notching
- Obtuse gonial angle
- Divergent occlusal planes
- Straight mandibular canal
- Long and thin symphysis
- Distal condylar inclination
- Dental protrusion
- Increased incisor display at rest (DAC)
- High mandibular plane angle
- Lip incompetence at rest due to increased LAFH
Skeletal vs dental AOB
- Displaced teeth vs non displaced teeth
- Generalised vs localised
- Skeletal AOB more severe; occlusal planes diverge from first molar anteriorly vs dental diverge from first premolar anteriorly
- Bilateral vs unilateral AOB
- Presence of DAC
- History of habit, spontaneous resolution of AOB with cessation of habit
- Presence of ankylosed/impacted tooth at AOB
- Presence of bimax proclination
- Presence of condylar degenerative diseases
treatment of aob in children
- High pull headgear
- Exerts occipital force to hold molars in place in the vertical plane
- Posterior bite block
- Acrylic 5-6mm thick covers occlusal surface of teeth to prevent posterior teeth from erupting
treatment of aob in adults
- Temporary Anchorage Devices, usually placed at buccal bone –> exert apical force to bring posterior teeth apically ie molar intrusion, allowing mandible to rotate forward and upward
- Orthognathic surgery — Le Fort I surgery to create interocclusal space for molars to rotate upwards and forwards
What are the causes of posterior open bite
- Skeletal asymmetry
- Very hyperdivergent mandible (AOB extends posteriorly)
- Macroglossia
- Primary failure of eruption, ankylosis (usually primary molars), eruption. Suspect PEE when no signs of mechanical obstruction + no eruption for 6 months-1 year
- Mesial tipping of molars eg due to early loss of Es
What are the skeletal features of skeletal deep bite
- Square/acute gonial angle
- Reduced LAFH
- Lower mandibular plane angle
- Convergent rotation of maxilla and mandible anteriorly
- Horizontal palatal plane
Dental etiology of deep bite
- Over eruption of anterior
- Under eruption of posterior eg severe attrition, posterior bite collapse
- Bimax retroclination
Difference in growth modification appliances for deep bite and for anterior open bite
- Headgear
- Deep bite uses cervical pull headgear to pull molar downwards
- AOB uses high pull headgear with more occipital force to control eruption of molars
- Bite plate
- Deep bite uses anterior bite plate with thick acrylic anteriorly that discludes posterior teeth. This allows for eruption of lower posterior teeth.
- AOB uses bite plate that covers occlusal surfaces of posterior teeth to prevent posterior teeth from eruption
