Principles of Tooth Reduction for Restorations

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Questions and Answers

How does the thickness of remaining dentin affect pulpal response?

The thickness of remaining dentin is inversely proportional to the pulpal response; thinner dentin leads to a stronger pulpal response.

What factors determine the proper amount of axial reduction in tooth preparation?

Proper axial reduction depends on the removal of undercut areas, alignment with the path of insertion, and the tooth's resistance to deformation.

List two considerations that influence occlusal reduction during tooth preparation.

Occlusal reduction is influenced by the degree of occlusal wear and the area of occlusal contact.

What is a necessary step before constructing a fixed partial denture in the lower arch regarding opposing teeth?

Correction of overerupted opposing teeth to establish balanced occlusion is necessary. Signup and view all the answers

Why is it crucial to remove all caries before placing a crown or bridge?

Any caries left under the crown or bridge can lead to pulp involvement and periapical pathosis, causing restoration failure. Signup and view all the answers

What is the primary goal of tooth reduction when preparing for extra-coronal restorations?

The primary goal is to preserve the maximum amount of sound tooth structure. Signup and view all the answers

Identify one cause of pulp injury during tooth preparation.

One cause of pulp injury is excessive temperature from high-speed cutting instruments. Signup and view all the answers

Why is it important to protect adjacent teeth during tooth preparation?

Protecting adjacent teeth prevents abrasive damage and maintains their integrity during the restoration process. Signup and view all the answers

What type of finish line should be selected when conserving tooth structure?

A supragingival finish line should be selected whenever possible. Signup and view all the answers

How can preparing an occlusal surface conservatively affect tooth reduction?

An anatomically prepared occlusal surface ensures adequate clearance without excessive tooth reduction. Signup and view all the answers

What is the recommended path of insertion for mandibular molars during restoration?

The path of insertion should coincide with the long axis of the tooth, typically inclined 9 to 14 degrees lingually. Signup and view all the answers

What benefit does conserving tooth structure provide in relation to pulp vitality?

Conserving tooth structure reduces harmful pulpal effects from procedures and materials used. Signup and view all the answers

What is a common error to avoid when preparing a tooth for restoration?

A common error is preparing the tooth with a path of placement that is perpendicular to the occlusal plane. Signup and view all the answers

Study Notes

Principles of Tooth Reduction for Extra-Coronal Restorations

Restorations need to consider biological, mechanical, and aesthetic factors.
Biological: Preserve tooth structure, avoid overcontouring, maintain supragingival margins, ensure harmonious occlusion, and prevent tooth fracture.
Mechanical: Create retention and resistance forms, reduce deformation.
Aesthetic: Minimize metal display, maximize porcelain thickness, use porcelain occlusal surfaces, and shape subgingival margins for optimal restoration.

Reduction of Sound Tooth Structure

Biologic principles for tooth reduction focus on:
- Preserving maximum sound tooth structure.
- Maintaining pulp vitality.

Prevention of Damage During Tooth Preparation

Avoid harming adjacent teeth.
Protect soft tissues (cheeks, lips, tongue, gingiva).
Protect the pulp.
Pulp injury causes: Temperature (excessive pressure, high speed, type/shape/condition of the cutting instrument), coolant (air/water spray), chemical action (dental materials/luting agents), and bacterial action (left behind/gained access due to microleakage).

Protection of Adjacent Teeth

Prepare a proximal enamel lip to prevent damage to adjacent teeth when opening proximal contacts.
Use a matrix band to protect adjacent teeth from abrasive contact during preparation, but it should not be the only protection method. The band should be monitored effectively, as perforations could result.

Guidelines for Conservation of Tooth Structure

Favor partial coverage restorations over complete coverage restorations to preserve more tooth structure.
Maintain supragingival finish lines. Avoid unnecessary extension of the finish line subgingivally.
Use a conservative finish line that facilitates sufficient bulk for the planned restoration.
Prepare the occlusal surface anatomically. This will help maintain adequate clearance without excessive tooth reduction.

Conservation of Sound Tooth Structure (Path of Insertion)

Path of insertion should align with the long axis of the tooth (for a mandibular molar, this is typically inclined 9-14 degrees lingually).
Avoid perpendicular placement with the occlusal plane as this may lead to unnecessary tooth reduction.

Orthodontic Uprightening

Orthodontic uprighting is a helpful step before reduction to achieve a more conservative preparation.

Preservation of Pulp Vitality

Conserve as much tooth structure as possible to reduce harmful pulpal effects of procedures and materials.
The thickness of remaining dentin is inversely proportional to the pulpal response.

Determination of Proper Tooth Reduction

The proper amount of tooth reduction is determined by axial and occlusal reduction.

Axial Reduction

Remove undercuts to remove any areas of potential undercut.
Align the reduction with the path of insertion.
Consider resistance of the restoration to deformation.
Account for material of the intended restoration.
Consider possible tipping or tilting of the tooth during reduction.

Occlusal Reduction

Account for the degree of occlusal wear.
Consider the area of occlusal contact.
Account for overeruption of opposing teeth.

Amount of Occlusal Reduction

Uniform reduction to produce appropriate occlusal clearance is preferred.
Do not unnecessarily shorten the mesial walls.
Do not reduce more than necessary to accommodate the restoration. The needed structure may not need to be cut.

Correction of Overerupted Opposing Teeth

Correct overeruption of opposing teeth to ensure a balanced occlusion before constructing a fixed partial denture on lower arches.

Correction of Overeruption Methods

Simple contouring of plunger cusps and topical fluoride treatment.
Orthodontic intrusion.
Occlusal veneers.
Crown preparation for the overerupted tooth.
Endodontic treatment and crowning of affected teeth.
Extraction of overerupted teeth in certain instances.

Removal of Decay

Remove all decay to prevent future pulp involvement and periapical pathosis.

Removal of Decay & Cavity Restoration

Ensure no decay remains under a crown or bridge, which may result in pulp involvement, periapical pathosis, and restoration failure.

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Description

This quiz explores the principles of tooth reduction necessary for extra-coronal restorations. It covers essential biological, mechanical, and aesthetic factors to consider when performing tooth preparations. Test your knowledge on preserving tooth structure and preventing damage during procedures.