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Questions and Answers
What is the primary purpose of the resistance form in class II amalgam cavity preparation?
What is the primary purpose of the resistance form in class II amalgam cavity preparation?
Which feature is included in the secondary retention form for class II amalgam preparations?
Which feature is included in the secondary retention form for class II amalgam preparations?
What is a key requirement for amalgam cavity preparation regarding the occlusal cavosurface angle?
What is a key requirement for amalgam cavity preparation regarding the occlusal cavosurface angle?
What is the recommended depth for the axial wall in a class II cavity preparation?
What is the recommended depth for the axial wall in a class II cavity preparation?
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Which of the following best defines the term 'convenience form' in cavity preparation?
Which of the following best defines the term 'convenience form' in cavity preparation?
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In the proximal part of the class II preparation, how should the buccal and lingual walls be oriented?
In the proximal part of the class II preparation, how should the buccal and lingual walls be oriented?
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Which bur is recommended for creating retention grooves in class II cavity preparations?
Which bur is recommended for creating retention grooves in class II cavity preparations?
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What is the recommended clearance between the proximal preparation and adjacent surfaces?
What is the recommended clearance between the proximal preparation and adjacent surfaces?
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What is the minimum thickness of amalgam recommended in areas of occlusal contact to help prevent amalgam fracture?
What is the minimum thickness of amalgam recommended in areas of occlusal contact to help prevent amalgam fracture?
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Which feature of the convenience form facilitates adequate access and visibility when preparing a tooth?
Which feature of the convenience form facilitates adequate access and visibility when preparing a tooth?
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What is the recommended cavo-surface angle to maintain maximal edge strength of amalgam?
What is the recommended cavo-surface angle to maintain maximal edge strength of amalgam?
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During the preparation of the proximal box, which step should be performed first?
During the preparation of the proximal box, which step should be performed first?
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What should the axial wall depth be when preparing a cavity?
What should the axial wall depth be when preparing a cavity?
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When preparing the proximal extensions, which limit should be followed for mesiofacial and mesiolingual clearance?
When preparing the proximal extensions, which limit should be followed for mesiofacial and mesiolingual clearance?
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What is the purpose of keeping the proximal enamel intact during cavity preparation?
What is the purpose of keeping the proximal enamel intact during cavity preparation?
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Which preparation technique should be altered for the mandibular first premolar?
Which preparation technique should be altered for the mandibular first premolar?
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What is the recommended height of the proximal marginal ridge when preparing for an amalgam restoration?
What is the recommended height of the proximal marginal ridge when preparing for an amalgam restoration?
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What is the primary purpose of the amalgam insertion technique?
What is the primary purpose of the amalgam insertion technique?
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What should be done after carving the facial and lingual areas of the amalgam restoration?
What should be done after carving the facial and lingual areas of the amalgam restoration?
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What instrument is best used for removing proximal excess and developing contours in the embrasure area?
What instrument is best used for removing proximal excess and developing contours in the embrasure area?
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What indicates that the amalgam restoration is too high during the occlusion evaluation?
What indicates that the amalgam restoration is too high during the occlusion evaluation?
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After how many hours should finishing and polishing of the amalgam restoration be conducted?
After how many hours should finishing and polishing of the amalgam restoration be conducted?
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Which abrasive point is used at low speed during the polishing step?
Which abrasive point is used at low speed during the polishing step?
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What can happen if amalgam restorations are carved completely out of occlusion?
What can happen if amalgam restorations are carved completely out of occlusion?
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Study Notes
Class II Amalgam Cavity Preparation
- Definition: Preparation required to correct carious lesions that develop on the proximal surface of posterior teeth.
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Requirements for Amalgam Preparation:
- Uniform 1.5-2 mm minimum thickness for occlusal load resistance
- 90-degree occlusal cavosurface angle
- Removal of all unsupported enamel
- Undercut preparation form for mechanical retention
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Outline Form:
- Includes all carious lesions, defects, or existing restorative material
- Occlusal outline form: Same as Class I preparation
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Proximal outline form:
- Isthmus: Narrow part connecting occlusal and proximal portions of Class II, straight for small contact areas
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Proximal portion of Class II:
- Converges bucco-lingually
- Buccal and lingual walls parallel to corresponding surfaces
- Not more than 0.5 mm clearance with adjacent surface facially, lingually, and gingivally
- Axial wall depth 0.2-0.8 mm into dentin
- Straight or convex axial wall parallel to external surface of the tooth
- Gingival floor parallel to the long axis of the tooth
Resistance Form
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Resistance Features:
- Preserving dentin supporting cusps and marginal ridges
- Pulpal and gingival walls perpendicular to occlusal forces
- Rounded internal preparation angles to reduce stress concentration
- Remove unsupported tooth structure
- Height of the proximal marginal ridge at the same level as the adjacent tooth
- Rounded marginal ridges
Primary Retention Form
- Facio-lingual walls converge occlusally
Secondary Retention Form
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Retention Grooves:
- Recommended for preparations with extensive proximal boxes
- Bur: No. 169 or No. 1/4 round bur
- Position: axiofacial – axiolingual line angle
- Depth: 0.5 mm, 0.2 mm from DEJ
- Occlusoginigival height: at level or just occlusal to the DEJ
How to Prevent Iatrogenic Damage of the Proximal Surface of the Adjacent Tooth
- Keep the proximal enamel until the end of the preparation
- Place the matrix band around the adjacent tooth
- Use a fender wedge
Variations of Class II Preparations
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Mandibular First Premolar:
- Tilt the bur slightly lingual to establish the pulpal floor
- Preserve the large transverse ridge
- Prepare the proximal box first, then continue to the occlusal preparation
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Maxillary First Molar:
- Preserve the large oblique ridge whenever possible
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Maxillary First Premolar:
- On the mesial surface, facial wall extension is minimized for aesthetic reasons
Insertion of Amalgam
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Removal of Wedge:
- Before filling, remove the wedge to release the matrix band
- Condense the amalgam using a plugger
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Carving Facial and Lingual Areas:
- Use the side of an explorer and a Hollenback carver
- In the cervical areas, remove excess and develop the proper contour, usually convex
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Carving Proximal Embrasure Area:
- Use a scaler to remove proximal excess and develop contours and embrasures
- Place below the gingival margin and draw occlusally to shave off excess
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Post-carve burnishing:
- Lightly rub the carved surface with a small burnisher to improve smoothness
Occlusion Evaluation
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Steps:
- Remove the rubber dam
- Dry teeth and restoration for marking with articulating paper
- Place articulating paper over the restoration and adjacent teeth, instruct the patient to close gently into occlusion
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High restoration indicator:
- Cusp tips of adjacent teeth not in contact when they should be
- Opposing cusp prematurely occludes with the new restoration
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Identify excursive interferences by:
- Asking the patient to slide the teeth lightly from side to side and front to back
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Avoid carving amalgam completely out of occlusion:
- This can lead to supra-eruptive tooth movement and undesirable tooth contacts
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Patient instructions:
- Avoid chewing firm food for 24 hours
Finishing and Polishing
- Should be done after complete setting of the amalgam (24 hours)
- Reduces tarnish and corrosion
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Finishing steps:
- Use a white alumina stone
- A small round finishing bur can be used to accentuate grooves and fossae features without eliminating occlusal contact areas
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Polishing steps:
- Coarse rubber abrasive point at low speed and air-water spray
- Rubber points should be used at low speed (6000 rpm)
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Description
This quiz covers the essential concepts of Class II amalgam cavity preparation, including the definition, requirements, and outline forms necessary for effective treatment of carious lesions on posterior teeth. Test your understanding of the preparation techniques and critical details required for successful dental procedures.
