intra arch malocclusion Flashcards
BSI definition of class i malocclusion
lower incisor edges occlude with/lie immediately below cingulum plateau of upper central incisor
BSI definition of class ii malocclusion
lower incisor edges lie posterior to cingulum plateau of upper incisors (div I upper central incisors proclined/average inclination, div II upper central incisors retroclined
BSI definition of class iii malocclusion
lower incisor edges lie anterior to cingulum plateau of upper incisors. Overjet is reduced or reversed
Angle’s classification of class ii malocclusion
Lower first permanent molar distal to upper first permanent molar by at least width of half a cusp
soft tissue features of patient with class ii div 1 malocclusion
- Convex facial profile
- Significantly retrognathic mandible and increased overjet
- Lower lip trap, incompetent lips
- Acute naso labial angle
skeletal features of patient with class ii div 1 malocclusion
- Protrusive maxilla
- Retrusive mandible, shorter total mandibular length
dental features of patient with class ii div 1 malocclusion
- Protrusive maxillary dento alveolus
- Retrusive mandibular dentoalveolus
- Proclined/retroclined upper incisors
- Increased overjet
cephalometric features of patient with class ii div 1 malocclusion
- Maxilla and teeth anterior in relation to cranial base
- Maxillary teeth anterior in normally positioned maxilla
- Mandible normal size but posteriorly positioned
- Mandible underdeveloped
- Mandibular teeth posteriorly placed on mandible which is in a normal position
soft tissue factors that can exacerbate class ii div 1
- Lower lip trap (due to increased over jet)
- Active lower lip
- Lip habit eg suck on lower lip
- Low lip line ie lower lip does not cover upper incisors at all
- Forward resting tongue posture
- Lip incompetence/reduced lip tonicity
- Short upper lip
- Lip to lip seal by circum oral muscle activity
how does lower lip trap exacerbate class ii div 1 malocclusion
Lower lip exerts subtle force on upper and lower incisors further proclining upper incisors and may further retrocline lower incisors
what soft tissue factors retrocline lower incisors, exacerbating class ii malocclusion
- Active lower lip
- Lip habit eg suck on lower lip
what soft tissue factors procline upper incisors, exacerbating class ii div 1 malocclusion
- Low lip line ie lower lip does not cover upper incisors at all –> Upper incisors pushed by tongue more labially
- Forward resting tongue posture
- Lip incompetence/reduced lip tonicity
- Short upper lip
What are the possible soft tissue features of patient with class II div 2 malocclusion
- Hypodivergent
- Short LAFH
- Prominent chin point
- Deep bite
- Well developed and very active orbicularis oris and mentalis muscles/high in tonicity
- Lower lip curl
- High lower lip due to reduced LAFH (exert force on upper incisors from lower lip and cause upper incisor retroclination)
What are the skeletal features of patient with class II div 2 malocclusion
- Acute gonial and mandibular plane angle
- Shorter LAFH
- Excessive overbite
- Upward and forward mandibular rotation
- Horizontal palatal plane
What are the dental features of a patient with class II div 2 malocclusion
- Inverted maxillary occlusal plane with two occlusal levels ie anterior teeth are over erupted, posterior teeth infraoccluded
- Exaggerated mandibular curve of spee
Children with incompetent lips and overjet greater than ___mm are at increased risk of suffering trauma to upper incisors
7-8mm
Etiology of class III malocclusion
- Skeletal
- Maxillary deficiency
- Mandibular excess
- Combination
- Forward growth rotation
- Dental
- Palatally displaced/retroclined upper incisors
- Labially displaced/proclined lower incisors
- Mesial drifting of lower 6s
- Functional
- Anterior superior functional shift
What are the dental etiologies for class III malocclusion
- Localised crowding/displacement
- Early loss of lower primary Es/missing lower second premolars
- Pseudo class III malocclusion
How does early loss of lower primary Es/missing lower second premolars lead to class III malocclusion
mesial drift of 6s hence molars appear to be in class III relationship
what is pseudo class iii malocclusion
Dental interference (premature contact usually between incisors). There is forward displacement of mandible to disengage incisors and permit further closure into posterior occlusion.
What are the skeletal etiologies of a class III patient
- Increased mandibular length
- More anteriorly positioned glenoid fossa
- Maxilla hypoplasia
- Reduced anterior cranial base length
- Forward growth rotation
What are the features of patient with pseudo class III MI
- Forward functional displacement of mandible
- Class III malocclusion/anterior cross bite in MI
- Premature contact between maxillary and mandibular incisors in CR
- Class I skeletal base in CR
- Max incisors retro, mand incisors proclined
- May have traumatic occlusion
What are the consequences of untreated pseudo class III MI malocclusion
- Functional occlusion remodel over time to become true mandibular skeletal asymmetry/mandibular prognathia via adaptive remodelling. Constant forward posturing induce growth stimulus.
- Dental asymmetry from DAC in presence of lateral component
- Teeth in traumatic occlusion may become mobile over time and/or present with gingival recession
What feature of the primary dentition indicates that patient has higher risk of developing class III malocclusion
Mesial step molar relationship; worsens with maturity due to cephalocaudal gradient of growth
What can cause displaced teeth
- Abnormal position of tooth germ
- Space deficiency (usually affect teeth that erupt last in a segment)
- Tooth size arch length discrepancy
- Early loss of primary teeth
- Retained primary teeth
- Habits eg forward resting tongue
- Supernumerary teeth/cysts that deflect path of eruption
What causes late lower incisor crowding
- Late anterior mandibular growth in class III patients –> bring lower incisors forward into lip
- Late mandibular growth in downward rotation in patients with hyperdivergent mandible –> bring lower incisors into lip
- Late mandibular growth in upward rotation of patient with deep bite –> bring lower incisors upwards against upper incisors
Physiological causes of median diastema
- Crowns of unerupted canines press against root of upper laterals, causing roots to tilt distally
- Labial frenal attachment in mixed dentition stage tends to attach to incisive papilla, migrates labially and apically as child matures
Pathologic causes of median diastema
- Supernumerary (mesiodens)
- Thick frenal attachment
- Frenal attachment close proximity to interdental papilla
- Digit sucking habit, forward resting tongue posture
- Microdontia (laterals)
