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Questions and Answers
What does Angle's classification of malocclusion refer to?
What percentage of molars are Class I?
65%
What percentage of molars are Class II?
30%
What percentage of molars are Class III?
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Define normal occlusion.
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What is the definition of malocclusion?
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What defines a Class I molar malocclusion?
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What is a Class II molar Division 1 malocclusion?
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What does a Class III molar malocclusion indicate?
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What is a 'flush terminal plane'?
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What percentage of flush terminal plane relationships become Angle Class I?
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All distal steps transition into a Class II molar relationship.
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What is leeway space?
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What is the definition of early mesial shift?
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What is the definition of late mesial shift?
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Study Notes
Angle's Classification of Malocclusion
- Dentoalveolar relationships defined by the anteroposterior positioning of upper and lower first permanent molars.
Class I Molar Relationship
- Occurs in approximately 65% of the population and indicates normal occlusion.
Class II Molar Relationship
- Found in around 30% of the population; characterized by the maxillary first molar positioned mesially to the mandibular first molar.
Class III Molar Relationship
- Present in about 5% of the population; maxillary first molar articulates distally to the mandibular first molar.
Normal Occlusion
- Achieved when molars are positioned correctly and teeth follow a smoothly curving line.
Normal Molar Relationship
- Mesiobuccal cusp of the maxillary first permanent molar fits into the mesiobuccal groove of the mandibular first permanent molar.
Malocclusion
- Describes any deviation from normal occlusion in the positioning of the teeth.
Intra-maxillary Deviations
- Includes issues such as tooth rotations, irregularity, spacing, and crowding.
Inter-maxillary Deviations
- Encompasses crossbite, overjet, overbite, and molar relationship abnormalities.
Class I Molar Malocclusion (Neutrocclusion)
- Molars maintain class I relationship but may have crowding and malpositioned teeth; often accompanied by increased overjet.
Class II Molar Malocclusion (Distocclusion)
- Molar relationship indicates the maxillary first molar is positioned mesial, varies by half or full cusp.
Class II Division 0
- Characterized by normal inclination of incisors within Class II relationship.
Class II Division 1
- Molars remain class II, maxillary incisors are proclined, with increased overjet and overbite.
Class II Division 2
- Molars are class II; maxillary incisors are retroclined while lateral incisors flare labially.
Class III Molar Malocclusion (Mesiocclusion)
- Molar relationship where maxillary molars are positioned distally; may show ½ or full cusp deviation.
Class III Malocclusion Examples
- Characterized by reverse overjet of incisors and potential open bite (absence of vertical overlap).
Cuspid Classifications
- Class I: Neutrocuspid, Class II: Distocuspid, Class III: Mesiocuspid.
Subdivision
- Occurs in Class II and Class III, where only one side deviates from the Class I relationship.
Mutilations
- Defined as occlusion changes due to premature tooth loss leading to drift; classification is based on original molar positions.
Drifting
- Illustrates how tooth relationships adjust following the premature loss of teeth.
Incorrect Classification
- Occurs when teeth are classified based on their post-drift alignment rather than original positions.
Limitations of Angle's Classification
- Doesn't account for skeletal and muscular patterns, vertical and transverse issues.
Flush Terminal Plane
- Deciduous molars positioned parallel; likely to transition to Class I.
Mesial Step
- As long as the mesial step isn't excessive, it typically transitions to Class I; larger steps may lead to Class III.
Distal Step
- All result in a Class II molar relationship; careful evaluation of terminal plane relationship is crucial.
Terminal Plane Percentages
- Flush terminal plane: 76%, Mesial step: 14%, Distal step: 10%.
Flush Terminal Plane Outcomes
- 56% transition to Class I, 44% to Class II.
Mesial Step Outcomes
- 76% develop Class I, 24% develop Class III; higher mesial step increases Class III likelihood.
Distal Step Outcome
- 100% of distal steps lead to Class II molar relationships.
Primate Spaces
- Distal to the deciduous canine in mandible, mesial in maxilla.
Early Mesial Shift
- Occurs when first permanent molars move into primate spaces during eruption.
Leeway Space
- Refers to space differences created when permanent teeth replace deciduous teeth.
Leeway Space Measurements
- Maxillary arch: 3 mm total (1.5 mm wider for each molar).
- Mandibular arch: 5 mm total (0.5 mm for first molar and 2 mm for second).
Late Mesial Shift
- Movement of molars into leeway space after loss of deciduous molars, often more pronounced in lower molars.
Effects of Late Mesial Shift
- Can create Class I molar relationships in 56% of cases; increases risk of Class III development if mesial step is present.
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Description
Explore the fundamentals of Angle's classification of malocclusion through this engaging quiz. Learn about the different classes of molar relationships, including Class I, Class II, and Class III. Test your knowledge on the percentages of each classification related to occlusion.
