Questions and Answers
What is the definition of Class III malocclusion?
The lower incisor edge occludes anterior to the cingulum plateau of the upper incisors.
How common is Class III malocclusion in Caucasians?
3% of Caucasians
What are the features of Class III malocclusion?
Skeletal features, soft tissue features, occlusal and dento-alveolar features, facial growth factors.
What skeletal class is usually associated with skeletal features?
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What happens to the size of the maxilla and mandible in Class III malocclusion?
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Is the anterior cranial base short or long in individuals with Class III malocclusion?
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What are the lateral skeletal features in Class III malocclusion?
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What are the consequences of having a narrow upper arch and broad lower arch?
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What do soft tissues tend to do to compensate for skeletal relationships in Class III?
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Why do anterior crossbites occur in individuals with Class III malocclusion?
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What causes posterior crossbites in Class III malocclusion?
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With a Class III condition, what does the anterior and posterior crossbite indicate?
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Where may wear occur due to Class III malocclusion?
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Where may gingival recession occur in Class III malocclusion?
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What areas may experience crowding or spacing in Class III malocclusion?
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On average, how much more do individuals with Class III malocclusion grow and at what age?
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Is the growth in Class III malocclusion favorable compared to Class II?
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Can adverse growth in Class III be compensated for compared to Class II?
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Should you be pessimistic about future growth in Class III?
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When do we usually treat Class III malocclusion?
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What is an exception to the treatment timing for Class III?
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Why should mild Class III with mandibular displacement be treated early?
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What are the three categories of treatment for Class III?
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What are favorable features for predicting successful correction of Class III?
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Why is forward mandibular displacement favorable in treatment?
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When should treatment for moderate Class III start and how does the appliance move the teeth?
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When should treatment for marked skeletal Class III start and why?
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Study Notes
Class III Malocclusion Overview
- Defined by lower incisor edge occluding anterior to upper incisors' cingulum plateau.
- Approximately 3% prevalence in Caucasians.
Features of Class III Malocclusion
- Includes skeletal, soft tissue, occlusal, and dento-alveolar features.
- Influenced by facial growth factors.
Skeletal Features
- Often categorized as class III skeletal pattern.
- Characterized by a large mandible or small maxilla or a combination.
- Short anterior cranial base is common.
Lateral Skeletal Features
- Upper arch tends to be narrow due to size limitations.
- Lower arch is broad as it generally maintains larger dimensions.
- Consequences include the presence of crossbites.
Dento-Alveolar Compensation
- Soft tissues adapt by tipping teeth to adjust for skeletal relationships.
- Upper incisors become proclined while lower incisors are retroclined.
Crossbite Tendencies
- Anterior crossbites arise due to class III incisor relationships.
- Posterior crossbites occur from narrow upper arches opposing broad lower arches.
Mandibular Displacement
- Anterior and posterior crossbites are associated with forward mandibular displacement from edge-to-edge occlusion.
Wear and Recession
- Labial surfaces of upper incisors may experience wear.
- Gingival recession can occur on lower incisors.
Crowding and Spacing
- Narrow upper arches often lead to crowding.
- Broad lower arches may be aligned or spaced.
Facial Growth Patterns
- Individuals with skeletal class III grow about 2 mm more on average from ages 11 until the end of growth.
- Growth is considered favorable in class II but unfavorable in class III.
Compensation for Adverse Growth
- Less compensation possible for adverse growth in class III compared to class II due to skeletal structure limitations.
Treatment Timing and Prognosis
- Pessimism about future growth is warranted; treatment is usually postponed, with exceptions for mild cases with mandibular displacement.
- Treatment of mild class III early can prevent dental and periodontal damage and is relatively quick.
Treatment Categories
- Mild Class III: Procline upper incisors, typically using a removable appliance (URA).
- Moderate Class III: Procline uppers and retrocline lowers using fixed appliances (FAs).
- Marked Class III: Combines orthodontic treatment with orthognathic surgery.
Predictive Features for Successful Correction
- Mild class III with forward mandibular displacement is more favorable.
- Low or no dento-alveolar compensation may lead to instability post-treatment, whereas normal/increased overbite promotes stability.
Favorable Positions for Correction
- Forward mandibular displacement allows some correction through condyle repositioning.
- Slightly more edge-edge starting positions facilitate simpler corrections.
Treatment Considerations for Moderate Class III
- Treatment should begin later, focusing on bodily tooth movement with fixed appliances.
Marked Skeletal Class III Treatment
- Surgical treatment starts when growth has ceased to prevent changes from later growth.
- Patient dissatisfaction with both dental and facial aesthetics is a significant factor in initiating treatment.
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Description
This quiz focuses on the essential definitions and features of Class III malocclusion. It includes key skeletal characteristics, prevalence in different populations, and other relevant clinical details. Perfect for dental students and professionals looking to enhance their understanding of orthodontic classifications.