Dental Occlusal Reduction Quiz

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Questions and Answers

What is the correct depth for reducing the central groove in occlusal reduction?

1.5 mm

0.5 mm

0.8 mm (correct)

1.0 mm

How should the functional cusp bevel be oriented in relation to the opposing triangular ridge?

Parallel to the ridge (correct)

Perpendicular to the ridge

At a 45-degree angle to the ridge

1.5 mm away from the ridge

Which instrument is recommended for placing guiding grooves during occlusal reduction?

Flat-end diamond.

Round-end tapered diamond

Straight diamond bur

Tapered carbide (correct)

What is the minimum clearance required on functional cusps during occlusal reduction?

1.5 mm Signup and view all the answers

Which method can be utilized to assess occlusal clearance?

Utility wax and wax caliper Signup and view all the answers

What is the ideal margin configuration recommended in the axial reduction aiming for a supragingival position?

0.5 mm chamfer finish line Signup and view all the answers

What is the correct total convergence angle between opposing axial walls during axial reduction?

6 degrees Signup and view all the answers

What is a primary requirement for the preparation of a full metal crown?

Preservation of remaining tooth structure Signup and view all the answers

How should the alignment grooves be placed on the buccal and lingual walls?

One in the center and one in each transitional line angle Signup and view all the answers

Which of the following advantages is specifically associated with full metal crowns?

Greater retention due to the inclusion of all axial surfaces Signup and view all the answers

What is a disadvantage of using a complete metal cast crown?

It does not allow for electric vitality testing due to metal interference Signup and view all the answers

What must be avoided during the axial reduction to prevent unsupported enamel?

Cutting too deeply with the diamond Signup and view all the answers

In which scenario is a full metal crown particularly beneficial?

For managing furcation involvement to improve oral hygiene Signup and view all the answers

What is the appropriate width of the cervical chamfer during preparation?

0.5 mm Signup and view all the answers

What instrument is primarily used for axial reduction?

A narrow, round-tipped diamond Signup and view all the answers

How does the strength of a complete metal crown compare to other types of restorations?

It has superior strength compared to other restorations Signup and view all the answers

What is the purpose of placing additional retentive features during finishing?

To secure the restoration in place Signup and view all the answers

What might be a concern for patients regarding the aesthetic aspect of full metal crowns?

They may display metal, especially in visible areas Signup and view all the answers

Why is it important to maintain one half of the tooth intact during preparation?

To serve as a reference for adequacy of preparation Signup and view all the answers

Which of the following is NOT a function or feature of a complete metal cast crown?

Performs effective electric vitality testing Signup and view all the answers

What specific modification can a full metal crown aid in regarding tooth contour?

Management of malaligned teeth Signup and view all the answers

What is the preferred instrument for finishing the chamfer margin?

A fine-grit diamond or carbide bur Signup and view all the answers

What is the advantage of having smooth transitions from occlusal to axial surfaces?

It reduces bubble formation during restoration fabrication Signup and view all the answers

What is the minimum recommended occlusal clearance for non-centric cusps during cast crown preparation?

1 mm Signup and view all the answers

What is the role of the periodontal probe during the preparation process?

To check the relative parallelism of alignment grooves Signup and view all the answers

What is the recommended taper or convergence between opposing axial surfaces?

6 degrees Signup and view all the answers

What is the primary indication for using a complete cast crown?

To provide maximum retention and resistance Signup and view all the answers

Which of the following statements about undercuts during crown preparation is correct?

Undercuts should not exist between any opposing axial walls. Signup and view all the answers

What angle should the functional cusp bevel be placed at relative to the long axis of the tooth?

45 degrees Signup and view all the answers

In what situation is a complete cast crown contraindicated?

When treatment can be met with a conservative restoration Signup and view all the answers

Which part of the preparation process involves determining the occluso-gingival length of the crown?

Occlusal reduction Signup and view all the answers

How much clearance should be provided for the non-functional (non-centric) cusp?

0.6 mm Signup and view all the answers

What configuration should the margin of the prepared tooth have for crown placement?

Chamfer Signup and view all the answers

What is the minimum occlusal clearance required for non-functional cusps in a complete cast crown preparation?

1 mm Signup and view all the answers

Which of the following describes over-tapering in tooth preparation?

Reduces retention of the completed restoration Signup and view all the answers

What is one of the main reasons for using a complete cast crown on endodontically treated teeth?

To compensate for lost tooth structure Signup and view all the answers

What is the recommended metal thickness at the margin of the crown preparation?

0.5 mm Signup and view all the answers

When are axial contours typically corrected in the preparation for a complete cast crown?

When correction is not feasible with conservative techniques Signup and view all the answers

What type of teeth are complete cast crowns particularly indicated for?

Teeth under heavy occlusal stress Signup and view all the answers

What is the goal of occlusal reduction in the preparation of a complete cast crown?

To create sufficient space for the restorative material Signup and view all the answers

Study Notes

Complete Cast Crown Preparation

Definition: A full metal restoration that restores a tooth's function.
Requirements:
- Removal of adequate tooth structure.
- Preservation of remaining tooth structure.
- Reduction to create a crown with acceptable strength.

Advantages

Greater Retention: Includes all axial surfaces in the preparation, providing superior retention compared to less extensive restorations like three-quarter crowns.
Resistance Form: The preparation has greater resistance form than partial-coverage restorations.
Superior Strength: Stronger material compared to other restoration types.

Additional Benefits

Modifying Axial Contour: Enables modification of the axial tooth contour for malaligned teeth or furcation involvements. Improved oral hygiene is also possible through re-contouring of buccal and lingual walls.
Removable Partial Denture Retainers: Often the only option that allows creation of properly shaped survey lines, guide planes, and occlusal rests.
Occlusion Modification: Easier modification of the occlusion, which can be difficult with more conservative restorations, such as with supra-erupted teeth or if the occlusal plane needs re-establishment.

Disadvantages

Less Conservative: Involves all tooth surfaces, which potentially carries risk for the pulp and periodontium.
Vitality Testing Restrictions: The conductive metal prevents electric vitality testing.
Aesthetic Concerns: Patients may object to the display of metal, particularly in those with a normal smile line, which might limit use to posterior teeth.

Indications

Single Crowns and Fixed Partial Dentures (FPDs): Suitable for posterior maxillary/mandibular molars and premolars.
Extensive Coronal Destruction: Used for teeth with significant loss of tooth structure.
Posterior Short Clinical Crowns: Ideal solution when the clinical crown is short.
High Displacement Forces: Useful for long-span fixed partial dentures where high displacement forces are likely.
Correction of Axial Contours (when necessary): Used when creating a more conservative preparation isn't possible.
Removable Partial Denture Support: Can act as a support for removable partial dentures.
Endodontically Treated Teeth: High strength compensates for loss of tooth structure in endodontically treated teeth.

Contraindications

Conservative Restoration Options: If a conservative restoration is sufficient.
Limited Retention/Resistance Needs: If less than maximum retention and resistance are required.
High Esthetic Needs: Not ideal for anterior teeth requiring high aesthetics.

Preparation Armamentarium

High-Speed Contra-Angle Hand Pieces— Instruments for various reductions.
Round-Ended Tapered Diamonds: Various grit sizes for different reduction types.
Occlusal Guiding Grooves: Prepare the occlusal surface.
Occlusal Reduction: Reduce the occlusal surface of the tooth.
Axial Alignment Grooves: Create grooves for appropriate axial reduction.
Axial Reduction: Reduce the axial surface to a specific shape and margin.
Finishing and Verification of Occlusal Clearance: The final process to check the preparation and confirm the desired occlusal clearance.

Occlusal Reduction

Initial Reduction: Perform half the occlusal reduction at first and maintain the other half as a reference.
Functional Cusp Bevel: A 1.5 mm bevel placed parallel to the opposing triangular ridge.
Correct Depth: 0.8 mm for non-functional cusps and 1.3 mm for functional cusps.
Instruments: Round-ended, tapered diamond instruments for optimal results.

Evaluation Methods

Utility Wax and Wax Calipers
Occlusal Reduction Gauges
Occlusal Clearance Tabs
Occlusal Reduction Rings
Rubber Base

Axial Reduction

Aim: Achieving a 6-degree taper or convergence angle between opposing axial walls and a minimum wall height of 3mm.
Margin Configuration: Chamfer finish line 0.5 mm following the gingival contour.
Alignment Grooves: Placing grooves in the buccal and lingual walls, one centered and one in each mesial/distal transitional line angles.

Finishing

Smooth surface finish for all prepared tooth surfaces.
Smooth transitions from the occlusal to the axial surfaces.
Use fine-grit diamond or carbide for finishing the chamfer margin.

Criteria for Complete Cast Crown Preparation

Occlusal Room: Adequate space for the restoration material.
Minimum Occlusal Clearance: 1 mm for non-centric cusps and 1.5 mm for centric cusps.
Conservative Reduction: Following normal anatomic contours.
Axial Reduction: Parallel to the tooth's long axis with a 6-degree taper.
No Over-Tapering: Maintaining adequate retention for the finished restoration.
No Undercuts: Ensuring smooth movement of the restoration across the opposing axial walls.
Functional (Centric) Cusp Bevel: A 1.5 mm bevel, angled flatter than the external surface at approximately 45 degrees.
Non-Functional Cusp Bevel: Minimum of 0.6 mm clearance for adequate strength.

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Description

Test your knowledge on occlusal reduction techniques in dentistry. This quiz covers essential concepts such as depth of groove reduction, orientation of functional cusp bevels, and the requirements for full metal crowns. Perfect for dental students and professionals looking to sharpen their skills.