Antero-posterior discrepancies Flashcards
what is the prevalence of class II malocclusion in the general population
30%
what is the prevalence of class II malocclusion in all orthodontic patients in the US
33%
what are the categories of class II malocclusion
- maxillary excess
- mandibular deficiency
- combination
what is the etiology of a class II malocclusion
skeletal or dental
what is the most frequent problem presenting in the ortho practice
class II malocclusion
what factors are involved in the etiology of class II malocclusion
hereditary and environmental
class II malocclusion may reflect:
- maxilla- mandible disharmony with underdevelopment of mandibular growth
- dental disharmony (angle classification)
- combination
what are the clinical features in the diagnosis of the maxillary first molar and what is another name for it
the maxillary first molar in a mesial position in relation to the mandibular first molar (distoocclusion)
what are the two different types of class II malocclusion
- class II division 1
- class II division 2
describe class II division 1
convex profile
- mandibular retrognathism
- variable facial height
- increased overjet
-proclined maxillary incisors
- narrow and tapered upper maxillary arch
describe class II division 2
straight to convex profile
- decreased lower facial height
- normal overjet
- deep overbite
- retroclined maxillary central incisors
- labially inclined maxillary lateral incisors
in severe skeletal class II division 1 the lips are:
usually incompetent
vertical dimension is usually decreased in class II division 1 or 2?
class II division 1
dental crowding in class II division 2 is created by:
retroclination of the maxillary central incisors
deep overbite in class 2 division II is caused by:
over eruption of the maxillary central incisors and lower incisors
skeletal class II malocclusion components may be classified by:
- maxillomandibular relationship: mandibular retrognathism, midface protrusion or both
- vertical discrepancy: anterior upper face height often greater than normal and steep occlusal plane
treatment strategies of class II malocclusion are categorized based on:
growing and non growing status of patients
what is the treatment of class II malocclusion in growing patients
ideally tx should focus first on improving the skeletal discrepancy
- use functional appliances while the individual is still growing - growth modification
what is the tx of choice of class II maloclussion in adults/non growing individuals
- orthognathic surgery: adjusting the position of both in relation to the cranial base in the three dimensions and improving overall facial esthetics
- dentoalveolar compensation alone: camoflage dental treatment
what is the flow chart for treating dental class II malocclusion
-growing -> dentoalveolar correction
- non growing -> camouflage
what is the flow chart for treating skeletal class II maloclussion
- growing -> growth modification and functional appliances
- non growing -> orthognathic surgery or camouflage
removable functional appliances and headgear therapy depend on:
the cooperation of the patient
which removable appliance is used more often
twin block
what does the twin block do
- promote mandibular growth
- restrict further forward growth of the maxilla
- improve skeletal relationships in growing skeletal class II individuals with mandibular retrusion
what are the key differences between removable and fixed appliances
different working hours (intermittent vs continuous) and optimal treatment timing (before puberty growth vs at or after puberty spurt) and direction of further growth
dental changes with fixed appliances including mesial movement of lower molars and proclination of lower incisors were _____ than skeletal changes when compared to removable appliances
more significant
limited range of treatment for class II skeletal and dental malocclusions in non growing or growing individuals
non growing/adults
depending on the severity of the malocclusion you can also use
class II elastics, compensatory extractions
- maxillary premolars and/or mandibular premolars
orthognathic surgical modalities may be used to:
alleviate the functional and esthetic problems associated with this type of malocclusion
what is done in orthognathic surgery for severe class II malocclusions
- mandibular advancement with or without maxillary impaction (class II openbite)
what should be done before orthognathic surgery for severe class II malocclusion
proper presurgical orthodontic tooth movements and alignment of arches are essential to maximize the amount of discrepancy correction during surgery
what might prevent patients from choosing orthognathic surgery in severe class II patients
cost of the surgery and fear of undergoing surgery
what malocclusion is the most difficult and complex orthodontic problem to treat
class III
skeletal class III malocclusion is characterized by:
- mandibular prognathism
- maxillary deficiency
- some combination of these two
what is the prevalence of class III malocclusions in caucasians
1-4%
what is the prevalence of class III malocclusion in asians
20% of japanese
what are the factors for the etiology of class III malocclusions
hereditary and environmental
more than half of all skeletal class III malocclusions are reported from:
maxillary deficiency
what is the incidence of class III malocclusions suffering from maxillary deficiency
65-67%
what are the extraoral features of a class III malocclusion
- concave profile
- anterior facial divergence
- prominent lower third of face/chin
what are the intraoral features of class III malocclusion
- class III molar and canine relationship
- narrow upper arch
- decreased or reverse overjet
- crowding in upper arch
what are the 3 groups of class III malocclusions and describe each
- skeletal: hypoplastic maxilla, hyperplastic mandible or combo
- dental: anterior crossbite of functional origin
- pseudo class III: anterior crossbite due to a forward functional displacement of the mandible, CR-CO shift
a pseudo class III is not a true class III malocclusion if:
corrected early
what is the main etiological factor in most cases of a pseudo class III malocclusion
retroclined maxillary incisors
when and why must an anterior crossbite be corrected
as soon as it is deteched to increase the orthopedic effects thereby increasing the long term stability of the treatment results
when would you know that a crossbite is functional
manipulate the condyles in their physiologic rest position. if the occlusion is end to end then it is probably functional
what is the flow chart for treating a skeletal class III malocclusion
- growing -> growth modification
- non growing -> orthognathic surgery or camouflage
what is the flow chart for dental class III malocclusion
- growing -> removable appliance
- non growing -> orthodontic treatment- elastics
what is the treatment of choice for class III malocclusion in growing patients and what is its goal
- maxillary expansion protraction face mask
- expand upper jaw to accommodate the lower dentition. apply traction to the maxilla to reposition it more anteriorly. slow down growth of mandible
a facemask attached to a maxillary expansion appliance to promote anterior maxilla repositioning by:
inducing growth at the maxillary sutures
the chance of true skeletal change in class III malocclusion appears to decline when?
beyond age of 8
the chance of clinical success in treating class III malocclusion declines at:
ages 10 to 11
the principles involved in the comprehensive treatment of class III dentoalveolar malocclusions are:
- relief of crowding
- level and align arches
- increase overbite and overjet
- compensation by over proclination of upper incisors and retroclination of lower incisors
what is involved in the late manageemnt of class III malocclusions
- moderate or severe class III anteroposterior skeletal discrepancies, a combo of orthodontic tx and orthognathic surgery at the completion of skeletal growth (earlier in females than males) will be required to create an acceptable and stable class I occlusion
- usually an anterior and vertical maxillary repositioning is done
- more rarely a mandibular set back is done
what does presurgical orthodontic treatment involve in the late management of class III malocclusion
- align the maxillary and mandibular arches in order that they will coordinate when their respective skeletal bases have been surgically repositioned (decompensation)
a short period of orthodontic treatment is often required after surgery in late management of class III malocclusions to finish and detail the occlusion. how long?
ideally less than 6 months
