Questions and Answers
What is a surveyed crown?
A crown used as abutments to retain an RPD.
What is a good survey line?
Path of insertion of an RPD allowing the denture to go in and out without damaging soft and hard tissue.
To provide denture retention, what do we need to create?
Desirable undercut.
What is a pre-planned or surveyed restoration?
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Match the characteristics of surveyed crowns with their descriptions:
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How do you determine which RPD abutment tooth to serve as a surveyed crown?
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Does every RPD natural abutment tooth need to be a surveyed crown?
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What should you do prior to preparing a tooth to be an SC?
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What is the addition method for RPD?
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What is the subtraction method for RPD?
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On a surveyed crown, what is required in the preparation where the occlusal rest seat is?
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Rest seat and guiding planes are prepared for what material?
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In terms of tooth preparation for SC, what is crown ledge or shoulder?
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When writing a lab prescription for an SC, what should you specify?
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What can a laboratory technician follow your prescription to fabricate an SC that has?
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Why should extra consideration be made when an SC is fabricated on an endodontically treated tooth?
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Why is the amount of existing coronal tooth structure an important consideration for SC?
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A distal extension RPD with an ETT should have frequent what?
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The longer the RPD, the more what?
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What is important to do when the SC comes back from the lab?
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Study Notes
Surveyed Crown Overview
- A surveyed crown serves as an abutment specifically designed to retain a removable partial denture (RPD).
- It is critical to establish a good survey line, which is the path of insertion allowing for smooth placement and removal of the RPD without causing tissue damage.
RPD Retention Mechanisms
- Achieving denture retention requires the creation of a desirable undercut on the abutment tooth.
- Restorations should ideally be pre-planned to support future RPD or removable overdentures, which may include full contour restoration or a metal substructure.
Characteristics of Surveyed Crowns
- Surveyed crowns feature ideal retentive contours, definite guiding planes, optimum occlusal rests, and effective reciprocation.
Selection and Preparation of Abutment Teeth
- To determine which tooth to use as a surveyed crown (SC), first, identify the RPD abutment tooth and assess the necessity of an SC.
- Not every natural abutment tooth requires preparation as a SC; modifications to reduce tooth damage should be considered first.
Modifying Survey Lines
- Prior to preparing a tooth as an SC, modify the survey line and explore for favorable undercuts. Options include:
- Addition method: Intentionally adding bonded materials to enhance undercut.
- Subtraction method: Intentionally removing part of the tooth structure to create a desirable undercut.
Tooth Preparation and Material Considerations
- Additional occlusal reduction may be needed at the occlusal rest seat of a surveyed crown.
- Rest seats and guiding planes are typically prepared for metal restorations.
- A crown ledge or shoulder enhances lingual contour restoration and reciprocation effectiveness.
Laboratory Collaboration
- When writing lab prescriptions for surveyed crowns, clarity is key:
- Specify desire for a surveyed crown aligned with a specific RPD design.
- Always survey and tripod the working cast.
- Include RPD design details along with the working cast.
Outcomes from Laboratory Work
- A well-fabricated surveyed crown will provide an ideal retentive contour, definite guiding plane, optimal occlusal rest, and effective reciprocation.
Special Considerations for Endodontically Treated Teeth
- Extra consideration is given when fabricating surveyed crowns on endodontically treated teeth, which have a reported success rate of 77.4%.
- The coronal structure of the tooth is vital for crown retention, as RPD retainers exert additional forces.
Follow-Up and Maintenance
- Distal extension RPDs with an SC on endodontically treated teeth should be followed up regularly and relined as needed.
- A longer RPD increases torque applied to the surveyed crowns.
Final Verification
- It is essential to verify that the SC delivered from the lab matches the prescribed specifications before cementation, as discrepancies may necessitate crown removal.
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Description
Test your knowledge on surveyed crowns and their application in removable partial dentures (RPD). This quiz covers key concepts such as survey lines and denture retention. Perfect for dental students and professionals looking to reinforce their understanding.