Class II Amalgam Preparations Overview
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Questions and Answers

Class II caries affects which surfaces of which teeth?

the proximal surface of posterior teeth

If caries is on both the occlusal and proximal, it is classified as what class restoration?

still Class II

Where are Class II/smooth surface lesions typically found with respect to the contact area?

lesion typically begins just apical to the proximal contact area.

Class II lesions are also called smooth surface caries.

<p>True</p> Signup and view all the answers

What are Black's 7 Principles of Cavity Preparation?

<ol> <li>Establish outline form 2. Develop resistance form 3. Develop retention form 4. Obtain convenience form 5. Remove remaining carious dentin 6. Finish enamel walls 7. Clean the cavity preparation (i.e., rinse and dry)</li> </ol> Signup and view all the answers

When finishing enamel walls, what can be used?

<p>a hatchet with minimal force from occlusal to gingival and a 245 bur in slow speed handpiece</p> Signup and view all the answers

In order to prepare a conventional Class II cavity preparation, the ________ must be prepared first.

<p>occlusal</p> Signup and view all the answers

What are the 4 characteristics to consider when performing a conventional Class II cavity preparation?

<ol> <li>Occlusal 2. Depth 3. Walls 4. Shape</li> </ol> Signup and view all the answers

The occlusal portion of a Class II preparation is almost like a ________ occlusal amalgam preparation, except there is no...?

<p>Class I; no dovetail if a box is being added</p> Signup and view all the answers

Where is the cavity preparation box to be placed?

<p>Find the center of the proximal contact, then center the box around the proximal contact.</p> Signup and view all the answers

What are axial walls in Class II preparations?

<p>the internal wall that runs parallel to the long axis of the tooth</p> Signup and view all the answers

Describe the axial wall of a Class II preparation.

<p>the axial wall is vertical or slightly converging toward center of tooth. It also is convex bucco-lingually, parallel to outer surface of the tooth.</p> Signup and view all the answers

What is the measurement of the width of the gingival floor?

<p>Gingival floor width = the width of the 8-9 (small) hatchet</p> Signup and view all the answers

Name the walls of this MO prep.

<ol> <li>Buccal wall 2. Lingual proximal wall 3. Axial wall 4. Buccal proximal wall 5. Lingual wall 6. Pulpal wall 7. Gingival wall 8. Distal wall</li> </ol> Signup and view all the answers

What walls are present in Class II preps that are not present in Class I preps?

<p>proximal wall(s), gingival floor, axiopulpal line, mesiobuccal axial line angle, mesiobuccal-gingival point angle, etc.</p> Signup and view all the answers

What is the axio-pulpal line angle?

<p>Line angle where the pulpal wall and axial wall meet (the two internal walls)</p> Signup and view all the answers

What is the mesiobuccal axial line angle?

<p>Line angle where the mesial wall and buccal wall meet</p> Signup and view all the answers

What is the mesiobuccal-gingival point angle?

<p>Point angle where mesial wall, buccal wall, and gingival wall meet</p> Signup and view all the answers

What does the outline form of a Class II prep look like?

<p>Similar to Class I outline with a Reverse S-curve at proximal and 90 degree margin</p> Signup and view all the answers

You should converge which walls as a part of retention form? How much?

<p>buccal and lingual proximal walls; 7-10 degrees</p> Signup and view all the answers

There are slightly ______ corners at the gingival line angles which are also a part of resistance form.

<p>rounded</p> Signup and view all the answers

What are the aspects of resistance form?

<ul> <li>90 degrees cavosurface margins - Reverse S-curve - Reverse curve - Slightly rounded corners at the gingival line angles &amp; rounded axio-pulpal line angles - Proper occlusal depth (1.75 mm)</li> </ul> Signup and view all the answers

What should the occlusal depth be for resistance form?

<p>1.75 mm</p> Signup and view all the answers

Where is the reverse S more often required?

<p>on the buccal than the lingual</p> Signup and view all the answers

What is retention form?

<p>Converge the buccal and lingual proximal walls (7-10 degrees)</p> Signup and view all the answers

Why do we create a 'Reverse S-curve'?

<p>By creating an 'S' shaped curve in the proximal outline, the direction of the mesiofacial wall is parallel to the direction of the enamel rods.</p> Signup and view all the answers

The Reverse S is more often required on _______ than on the _______.

<p>buccal; lingual</p> Signup and view all the answers

What can we use to round the axio-pulpal line angles?

<ol> <li>Hatchet 2. 7801 bur</li> </ol> Signup and view all the answers

_______ can help gain a little space. _______ can protect adjacent tooth.

<p>wedge; matrix band</p> Signup and view all the answers

What is the buccolingual width of box?

<p>Dimensions are based on obtaining 'clearance.' Clearance = break contact so that the diameter of the last 0.5 to 1mm of explorer tip slides between the prep and adjacent tooth.</p> Signup and view all the answers

What is the gingival depth of box?

<p>Clearance should be the diameter of the last 0.5 to 1mm of explorer tip slides between the prep and adjacent tooth. (~1.5mm passed the pulpal floor)</p> Signup and view all the answers

Handpiece angulation should be _______ to the occlusal surface.

<p>perpendicular</p> Signup and view all the answers

We need to have 90 exit angles due to...?

<p>the orientation of the enamel rods</p> Signup and view all the answers

What are the features of a Class II amalgam preparation?

<ul> <li>90 degree cavosurface margins - Reverse S curve (more often on buccal than on lingual) - Gingival floor - Axial wall - convex bucco-lingually - Convergence of proximal walls - Convergence of walls under cusps - Divergence at groove extensions - Divergence at distal marginal ridge - Clearance at gingival margin - Rounded axiopulpal line angle</li> </ul> Signup and view all the answers

Study Notes

Class II Amalgam Preparations Overview

  • Class II caries affects the proximal surfaces of posterior teeth.
  • If caries impacts both occlusal and proximal surfaces, it remains classified as Class II.
  • Smooth surface (Class II) lesions typically start just apical to the proximal contact area.
  • Class II lesions are also referred to as smooth surface caries.

Black's Principles of Cavity Preparation

  • Key principles include:
    • Establishing outline form
    • Developing resistance and retention forms
    • Obtaining convenience form
    • Removing remaining carious dentin
    • Finishing enamel walls
    • Cleaning the cavity preparation

Finishing and Preparing the Cavity

  • Finishing enamel walls can be achieved using a hatchet or a 245 bur in a slow-speed handpiece.
  • In conventional Class II cavity preparations, the occlusal portion must be prepared first.
  • Characteristics to consider during preparation include occlusal, depth, walls, and shape.

Design and Structure of Class II Preparations

  • The occlusal part of Class II preparation resembles a Class I occlusal amalgam preparation but lacks a dovetail if a box is included.
  • The cavity preparation box is centered around the proximal contact for a conservative approach.
  • Axial walls run parallel to the tooth’s long axis and are prepared to provide effective support and retention.

Wall Characteristics and Angles

  • The axial wall of a Class II preparation is vertical or slightly convergent toward the center, and convex bucco-lingually.
  • Gingival floor width should match the width of an 8-9 small hatchet and maintain a uniform width parallel to the outer tooth surface.
  • Important wall definitions include:
    • Axiopulpal line angle: where pulpal wall meets axial wall.
    • Mesiobuccal axial line angle: junction of mesial wall and buccal wall.
    • Mesiobuccal-gingival point angle: convergence of mesial, buccal, and gingival walls.

Outline and Angulation

  • Class II outline form resembles Class I with a Reverse S-curve at proximal margins and 90-degree margins.
  • Proximal walls converge at 7-10 degrees for retention.
  • Rounded corners at gingival line angles enhance resistance form.
  • Proper occlusal depth for resistance form is established at 1.75 mm.

Additional Considerations

  • Reverse S-curves are primarily needed on buccal walls rather than lingual.
  • Rounding axio-pulpal line angles can be done with a hatchet or a 7801 bur.
  • Wedges provide space, and matrix bands protect adjacent teeth.
  • Buccolingual width of the box achieves clearance, ensuring that the last 0.5 to 1 mm of explorer tip can slide between prep and adjacent tooth.
  • Gingival depth also aims for similar clearance, which is approximately 1.5 mm past the pulpal floor.

Handpiece and Exit Angles

  • Handpiece angulation should be perpendicular to the occlusal surface to facilitate proper design.
  • 90-degree exit angles are crucial to align with the orientation of enamel rods.

Key Features of Class II Amalgam Preparation

  • 90-degree cavosurface margins.
  • Reverse S-curve often more pronounced on buccal surfaces.
  • Presence of a gingival floor.
  • Convex buccolingual axial wall.
  • Convergence of proximal walls and walls under cusps.
  • Divergence at groove extensions and margins as required.
  • Rounded axiopulpal line angles to support structural integrity.

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Description

This quiz covers the key principles and techniques for preparing Class II amalgam restorations. You'll learn about the characteristics of Class II caries, finishing cavity walls, and Black's principles of cavity preparation. Test your knowledge on effective cavity design and structure.

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