Questions and Answers
What is Class 1 malocclusion?
The lower incisor occludes with the middle third of the upper central incisor.
What is the incidence of Class I occlusion?
What describes the skeletal pattern in Class 1 occlusions?
A/P - usually Skeletal Class I, but not always; vertical - full range; lateral - facial asymmetry possible.
What are some intraoral signs of facial asymmetry?
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Which of the following are local factors that may cause malocclusion requiring treatment? (Select all that apply)
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What are the skeletal causes of anterior open bite?
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What are transverse occlusal problems?
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What can cause posterior crossbites?
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What is mandibular displacement?
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What is a bilateral crossbite?
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Study Notes
Class 1 Malocclusion Overview
- Class 1 malocclusion is characterized by the lower incisor occluding with the middle third of the upper central incisor.
Incidence of Occlusions
- Class I malocclusion prevalence is around 60%.
- Class II division 1 occurs in 20-30% of cases.
- Class II division 2 represents about 5% of cases.
- Class III malocclusion accounts for 5-10% of the population.
Skeletal Patterns in Class 1 Occlusions
- Anterior/Posterior (A/P) pattern is generally Class I skeletal, but can include dento-alveolar compensation.
- Vertical dimension ranges from average to increased or reduced facial height.
- Lateral skeletal relationships may show potential facial asymmetry.
Facial Asymmetry
- Intraoral signs include center-line discrepancies and posterior crossbites, as well as mandibular displacements.
- Extraoral signs may indicate condylar hyperplasia.
Local Factors Causing Malocclusion
- Conditions requiring treatment include hypodontia, macrodontia, ectopic canines, transposition, supernumerary teeth, median diastema, and cysts.
Anterior Open Bite (AOB)
- AOB can stem from skeletal issues due to increased lower face height, digit sucking habits, or soft tissue influences from tongue activity.
- Diagnosis is challenging and often relies on exclusion methods.
- Symmetry noted between skeletal and soft tissue AOB, whereas digit-related effects tend to be asymmetrical.
Transverse Occlusal Problems
- Posterior crossbites can arise from various types and causes, including discrepancies in the buccal segments.
- Normal transverse relationship occurs when the lower jaw fits within the upper jaw, ideally with upper palatal cusps positioned within lower fossae.
Causes of Posterior Crossbites
- Typically caused by a relatively narrow maxilla, indicative of a transverse skeletal discrepancy.
- Digit sucking habits can lead to a narrowed upper arch.
- Local issues, often linked to crowding, may also contribute.
Mandibular Displacement
- In the presence of crossbite, upper and lower molars may contact cusp to cusp, leading to lateral sliding of the mandible, resulting in unilateral crossbite while maintaining normal molar relationship on one side.
Bilateral Crossbite
- Indicates a significant lateral discrepancy.
- Generally accepted as they are not associated with mandibular displacement, reflecting a broader lateral skeletal discrepancy while still allowing occlusion of the teeth.
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Test your knowledge of Class 1 malocclusion with these flashcards. Each card covers essential definitions and statistical information related to different types of occlusions. Perfect for dental students and professionals looking to reinforce their understanding of orthodontic classifications.
