47. Class III malocclusion. Clinical manifestation and diagnosis Flashcards
(23 cards)
Class III malocclusion clinical manifestation and diagnosis
What is Class III Malocclusion?
- Buccal groove of mandibular first permanent molar occludes mesial to mesiobuccal cusp of maxillary first permanent molar.
Class III malocclusion clinical manifestation and diagnosis
List the types of Class III malocclusions.
- Mandibular prognathism
- Maxillary retrognathia
- Pseudo Class III (anterior cross bite)
Class III malocclusion clinical manifestation and diagnosis
What characterizes pseudo Class III malocclusion?
- Normal mandible
- Underdeveloped maxilla
Class III malocclusion clinical manifestation and diagnosis
Aetiological factors of Class III malocclusion
- Heredity
- Mental diseases
- Enlarged tonsils and naso-respiratory diseases
- Premature loss of deciduous molar
- Tongue thrusting habit
- Maxillary hypodontia
- Mandibular hyperdontia
- Hormonal disorders (e.g., acromegaly)
Class III malocclusion clinical manifestation and diagnosis
What are the vertical components of Class III malocclusion?
- Vertical deficiency
- Vertical normal
- Vertical excess
Class III malocclusion clinical manifestation and diagnosis
Sagittal components of Class III malocclusion
- Maxillary deficiency
- Mandibular excess
- Combination of both
Class III malocclusion clinical manifestation and diagnosis
Significant extraoral features for aesthetic evaluation in Class III malocclusion
- Configuration and form of forehead and nose
- Well formed nasiolabial angle
- Thickness of soft tissues of chin
- Increased lower facial third
- Concave profile
Class III malocclusion clinical manifestation and diagnosis
Intraoral features indicating Class III malocclusion
- Anterior cross bite
- Posterior cross bite
- Relative crowding with the arches
- Dentoalveolar compensation
- Anterior open/over bite
Class III malocclusion clinical manifestation and diagnosis
Significant cephalometric analysis finding in dentoalveolar Class III
No apparent sagittal skeletal discrepancy (normal ANB angle) w/ tipping of incisors.
Class III malocclusion clinical manifestation and diagnosis
What defines skeletal Class III malocclusion?
- Maxillary retrusion
- Mandibular prognathism
- Combination
Class III malocclusion clinical manifestation and diagnosis
True or False: Gingival recession or dehiscence can often be seen in early Class III malocclusion.
True
Class III malocclusion clinical manifestation and diagnosis
Fill in the blank: The premature loss of deciduous molar results in anterior mandibular _______.
displacement
Class III malocclusion clinical manifestation and diagnosis
Clinical significance of a well-formed nasiolabial angle
It is important for aesthetics.
Class III malocclusion clinical manifestation and diagnosis
What should be studied regarding the path of closure in Class III Malocclusion?
*Path of closure from postural rest position to occlusion=>
*Premature contact may cause anterior displacement into forced protrusion.
Class III malocclusion clinical manifestation and diagnosis
Prognosis for patients with anterior displacements in Class III malocclusion
*Anterior displacements have more favorable prognoses=>
*Compared to those w/problems from an anterior rest position=>
*Difficult to treat and may require orthognathic surgery.
Class III malocclusion clinical manifestation and diagnosis
Role of orthodontic pre-surgical treatment in Class III Malocclusion
*Must decompensate malpositions=>
* Caused by labial tipping of upper incisors and lingual tipping of lower incisors before surgical procedures.
Class III malocclusion clinical manifestation and diagnosis
Assessed regarding TMJ and tongue function in Class III Malocclusion
*Condyle’s position in temporal fossa
*Abnormal tongue function, size, and posture must be evaluated=>
*Especially in cases of mouth breathing or macroglossia.
Class III malocclusion clinical manifestation and diagnosis
Lip characteristics associated with Class III Malocclusion
- Short hypotonic retrusive upper lip often seen=>
- w/a heavy, redundant, everted lower lip
Class III malocclusion clinical manifestation and diagnosis
Diagnostic characteristics indicating unfavorable Class III growth
*Increased gonial angle *Antegonial notching
*Backward condylar growth
*Thin mandibular symphysis *Retroclination of mandibular incisors
Class III malocclusion clinical manifestation and diagnosis
Done to differentiate between true class III and pseudo class III malocclusion
*Mandible guided into centric relationship=>
*Reveal a normal overjet or edge-to-edge incisor relation in pseudo class III.
Class III malocclusion clinical manifestation and diagnosis
What cephalometric analysis shows in pseudo class III malocclusion if diagnosed early
*Normal SNA
*SNB could be slightly increased due to forward positioning of mandible.
Class III malocclusion clinical manifestation and diagnosis
Cephalometric findings in true class III case’s
*Large SNB angle or a small SNA angle may be found=>
* Depending on whether result due to an underdeveloped maxilla/ a long mandibular base, or both.
Class III malocclusion clinical manifestation and diagnosis
Common characteristic of most true class III cases
Most true class III cases have a strong hereditary component.
