Etiology of Malocclusion
- Polygenetic
- Multifactorial
- Investigation: monozygotic vs dizygotic (independent is genetic) more diff = more genetic contribution
Etiology of Malocclusion
1| Equilibrium theory: Force
4| Specific causes
Soft tissue
Dentition
Vert: Opposing & PDL
Jaw
Hypo2: Red bite force = red LAFH
Trans: Cheek vs tongue
Hypo1: Inc usage = inc size
Eg1: Soft tissue growth postures mandible causing growth at condyles
Eg2: Atrophy of temporalis after injury
AP: Lips vs tongue
Habits
Sucking (Y)
Tongue (Y/N)
Mouth breathe (N)
Effect dental:
Effect skeletal:
Observed in:
Types of tongue thrust:
Extent: Contribute but not etiology
Cause: Enlarge adenoid, nasal block, allergy
2| Malocclusion characteristics
Class I
Skeletal: Cl I or DAC Cl II/III
Class II Div I
Class II Div II
Class III
Soft tissue: Secondary cause
Dental
Size: Tooth size, arch length
Position: Displace/Impaction
Anomalies: (Macro/Micro/Hyper/Hypo)
Late lower incisor crowding
Skeletal
Genetic
Skeletal: growth disturbances
Soft tissue: muscular dysfunction
Dental: disturbance
Acromegaly & Hemimandibular hypertrophy
Embryological Dev (<1%)
Congenitally missing
Malformed & supernumerary
Eruption interference
Ecotopic erruption 6s
Early loss of primary #4/5
Traumatic displacement
Specific
Soft tissue characteristics
Habits
Types of Cl II malocclusion
Dental
Skeletal
Soft tissue
Skeletal"
AOB
Ankylosis due to trauma
Bimaxillary proclination
Impaction
Soft tissue / Habits
Mouth breathing
Forward resting tongue posture
Thumbsucking
Skeletal
Deep OB (Q similiar to Class II Div II
POB
Soft tissue
Dental
Skeletal
Posterior Crossbite
Dental
Skeletal
Genetic disorders
Dental
Causes of delayed tooth eruption
Generalized (minority)
Localized (majority)
Ectopic erruption of #3 (Environmental)
Early loss of primary #3 (More severe than loss of Es)
What causes Ankylosis
Genetics
Skeletal problems