L7 Clinical journey for crown provision Flashcards
List the 8 steps of producing a dental crown.
1) Patient assessment, assess tooth restorability
2) Remove caries, restore tooth, core if neessary
3) Crown preparation, impressions of both arches, shade recorded
4) Send impressions and prescription to lab
5) Assess lab work, manage errors/faults
6) Try in, check if it seats properly, margins, occlusion, contact points, aesthetics (is pt happy)
7) Cement the crown in, check occlusion
8) Review
What are the features of a satisfactory impression?
- Accurate and clear margins
- No air pockets
- No drags or torn material
How do you assess the crown sent from the lab?
- Check for defects
- Look on the model, check the contacts, occlusion, margins flush with the tooth?
- Look for casting or ceramic defects
- Make sure the crown doesn’t rock
- Check for blebs: extension of model material which have filled air pocketsof the impression
What might you be able to tell when a patient returns with their temporary crown?
- Make note of if it is present, damaged, worn, missing
- Could indicate issues with tooth or crown prep, may not be as retentive as hoped
What should you do if the crown is not seating?
How do you permanently cement a crown?
- Moisture control
- Thin mix of cement covering internal surfaces and margins
- Insert crown, maintain pressure and ensure cement flows around whole margin
- Wait for intial set and clear excess
- Recheck occlusion
What are the ideal properties of a luting cement?
- Low viscosity and thin film thickness
- Long working time with a rapid set at mouth temperature
- Good resistance to aqueous or acid attack
- Adheres to tooth structure and restoration
- High compressive and tensile strength
- Resistant to plastic deformation
- Radiopaque
- Cariostatic
- Biologically compatible with pulp and soft tissues
- Translucent if required for aesthetic reasons (I.e. ceramic crown)
What cements are used most commonly for crowns?
Adhesive cement:
- Resin cement e.g. RelyX (good for metal ceramic crowns)
- Procera cement for all ceramic corwns (good aesthetics)
Conventional cements (less popular nowadays):
- Poly-F
- Zinc phosphate
What should you check at the review appointment?
- Aesthetics
- Retention
- Margins
- Contacts
- Occlusion
- Dynamic function e.g. chewing
- Speech
Why is retraction used?
- Retracts soft tissues and controls bleeding at the margin
- Provides a clear, controlled margin to accurately record with an impression material or intraoral scanner
What gingival retraction methods are there?
- Retraction cord (most common)
- Electrosurgery (see image, good for subgingival margins, not for pts with pacemakers)
- Retraction caulking agents (similair to cord, syringe delivery, clay based)
How is retraction cord used?
- First cord placed in contact with epithelium
- Second cord placed to push first cord down
- Second cord removed and impression material syringed into gap
Why do we provide patients with temporary crowns?
- Prepped tooth will be painful and sensitive, we want to cover the exposed dentine
- Maintains occlusion and tooth position, preventing tooth from drifting or over erupting
- Maintains gingival health, no overgrowth
- Allows function, patient can speak, eat, smile
- Aesthetics
What are the options for temporary crowns?
Pre-formed crowns:
- Directa crowns, polycarbonate shell
- Iso-form crowns, silver tin
- Usually relined with Trim to improve fit
Bespoke crowns:
- Pre-operative matrix used to shape acylic or resin temp material
- Acylic e.g. Trim
- Resin e.g. ProTemp, Integrity cemented using TempBond
What are the pros and cons of iso-form crowns?
- Cheap
- Useful in emergency
- Weak and can wear through the occlusal surface
- Poorly retained
- Alternative techniques more reliable
How do we take a good impression for a crown?
Describe the steps of taking a good impression.
