Podcast
Questions and Answers
Which factor is NOT mentioned as a contributor to heat generation during dental procedures?
Which factor is NOT mentioned as a contributor to heat generation during dental procedures?
Chemical agents used for cleaning and degreasing tooth preparation are safe to use.
Chemical agents used for cleaning and degreasing tooth preparation are safe to use.
False
What is one of the basic tenets of restorative dentistry regarding tooth structure?
What is one of the basic tenets of restorative dentistry regarding tooth structure?
To conserve as much tooth structure as possible.
Cavity varnish forms an effective barrier and has little effect on the __________ of the cemented restoration.
Cavity varnish forms an effective barrier and has little effect on the __________ of the cemented restoration.
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Match the guidelines for conservation of tooth structure with their descriptions:
Match the guidelines for conservation of tooth structure with their descriptions:
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What is the minimum distance a crown margin should be placed from the alveolar crest to avoid bone resorption?
What is the minimum distance a crown margin should be placed from the alveolar crest to avoid bone resorption?
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A rough junction between a cemented restoration and a tooth decreases the length of the margin.
A rough junction between a cemented restoration and a tooth decreases the length of the margin.
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What happens when the crown margin intrudes into the biologic width?
What happens when the crown margin intrudes into the biologic width?
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The junction between a cemented restoration and the tooth is always a potential site for ___________ due to dissolution of the luting agent.
The junction between a cemented restoration and the tooth is always a potential site for ___________ due to dissolution of the luting agent.
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Match the following situations with their corresponding implications regarding crown margins:
Match the following situations with their corresponding implications regarding crown margins:
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Study Notes
Heat Generation
- Factors that increase heat generation: excessive pressure, higher rotational speed, bur type, shape, and condition
- Coolant: use water spray directed at the contact points of the tooth and bur.
- Challenges: coolant cannot reach cutting edge of the bur when preparing grooves or pinholes.
- Solution: prepare retentive features at low speeds to prevent heat buildup
Chemical Action
- Pulpal damage: certain dental materials are damaging to the pulp, especially when applied to freshly cut dentin.
- Materials: bases, restorative resins, solvents, and luting agents can be harmful.
- Protection: cavity varnish creates an effective barrier, minimally affecting restoration retention.
- Contraindication: cleaning and degreasing agents are pulpal irritants.
Bacterial Action
- Cause of pulpal damage under restorations: bacteria left behind or entering the dentin due to microleakage.
- Prevention: remove all carious dentin before placing the restoration.
Conservation of Tooth Structure
- Principle: preserve as much tooth structure as possible, balancing mechanical and esthetic principles.
- Factors affecting pulp: thickness of remaining dentin is inversely proportional to pulpal response.
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Guidelines:
- Use partial restorations when possible.
- Minimize convergence angle (taper) of preparations.
- Ensure even and anatomical reduction of the occlusal surface.
- Adequate reduction of axial surfaces.
- Choose a conservative margin compatible with other preparation principles.
- Avoid unnecessary apical extension of the preparation.
Subgingival Margins
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Advantages:
- Easier impression making with less soft tissue damage.
- Simpler evaluation of restorations at recall appointments.
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Circumstances necessitating subgingival margins:
- Caries, erosion, or restorations extending subgingivally, where crown lengthening is not indicated.
- Proximal contact area extending to gingival crest.
- Increased preparation stump for additional retention.
- Hiding the margin of a metal-ceramic restoration behind the labiogingival crest.
- Root sensitivity not manageable by conservative procedures.
- Required modification of the axial contour.
Biological Width
- Maintenance of bone: a crown margin should be placed at least 2.0mm away from the alveolar crest.
- Composition: epithelial and connective tissue attachments combine for a width of approximately 2.0mm.
- Inflammation and bone resorption: intrusion of the margin into this biological width causes inflammation and bone recession until 2.0mm distance is restored.
Marginal Integrity
- Essential for survival: restoration must closely adapt to the cavosurface finish line to survive in the oral environment.
- Factors impacting adaptation & seating: finish line configuration dictates the shape and bulk of the restorative material at the margin.
- Recurrent caries: junction between cemented restoration and tooth is a potential site for recurrent caries due to luting agent dissolution and inherent roughness.
- Importance of good adaptation: minimizes the risk of recurrent caries and periodontal disease.
- Well-designed preparation: smooth and even margins are key. Rough or stepped junctions increase margin length and decrease adaptation.
Margin Configuration
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Featheredge or shoulderless margins:
- Advantage: conserve tooth structure.
- Disadvantage: inadequate bulk at the margin, leading to over contoured restorations.
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Chisel edge margins:
- Advantage: conserve tooth structure.
- Disadvantage: over contoured restorations, challenges in controlling margin location.
- Indication: tilted teeth.
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Chamfer margins:
- Advantage: well-defined, distinct finish line, adequate material bulk, accurate placement.
- Disadvantage: care is needed during preparation to avoid unsupported enamel.
- Indication: cast metal restorations, lingual margins of labial veneer restorations, metal-ceramic restorations.
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Shoulder margins:
- Advantage: adequate bulk for restoration.
- Disadvantage: less conservative compared to chamfer, sharp internal line angle can lead to coronal fracture.
- Indication: full veneer metal-ceramic restorations, all-ceramic crowns.
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Shoulder with bevel margins:
- Advantage: adequate bulk for the restoration, bevel removes unsupported enamel.
- Disadvantage: less conservative for tooth structure, bevel should be placed apically.
- Indication: metal-ceramic restorations, previous caries or restorations at the finish line area.
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Beveled margins:
- Advantage: removes unsupported enamel, benefits of beveling.
- Disadvantage: less conservative, often needs to be placed subgingivally for optimal esthetics.
- Indication: ledges from previous caries or erosion at the cervical margin.
Margin configuration: summary table
- Feather Edge: Conservation of tooth structure, Can Lead to over contoured restorations
- Chisel: Conservation of tooth structure, Can lead to over contoured restorations, Difficult to control margin location
- Chamfer: Distinct, well defined finish line, Gives adequate bulk, Care during preparation to avoid formation of unsupported enamel
- Shoulder: Gives adequate bulk, Less conservative than chamfer finish line, Sharp internal line angle
- Shoulder with Bevel: Gives adequate bulk, Less conservative to tooth structure, Bevel need to be placed apical
- Beveled: Removes unsupported enamel, Less conservative, Need to extend subgingival for optimal esthetic results
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Description
This quiz focuses on the factors influencing heat generation during dental procedures and the effects of chemical actions on dental pulp. It also covers the role of bacterial action in pulpal damage and preventive measures to ensure effective treatment. Assess your understanding of these critical concepts in dental health.
