Indications for Crowns and the Preoperative Assessment Flashcards
What is a crown?
A full coverage extra- coronal restoration.
What kind of restoration is a crown? (direct or indirect)
Indirect - made in the lab.
7 indications for crowns?
- Repeated failure of a direct plastic restoration.
- Difficulty achieving adequate contour, contact point and occlusal contacts with a direct restoration.
- Minimize risk of tooth fracture.
- Aesthetics.
- To include design characteristics to accommodate a metal-based removable prosthesis.
- Bridge abutment.
- Replacement of an existing crown.
2 ways in which a direct restoration can fail?
- Fracture.
- Debond.
why are inadequate occlusal contacts bad?
Increased risk of restoration FRACTURE and subsequent MICROLEAKAGE and SECONDARY CARIES.
4 materials a crown can be made from?
- Gold alloy (precious metal alloy).
- Ceramic.
- Metal bonded to ceramic.
- Non precious metal alloys (ex. cobalt chromium, nickel chromium).
Why are inadequate contact points bad?
- Increased FOOD PACKING.
- Difficult to CLEAN and MAINTAIN –> SECONDARY CARIES/ PERIODONTAL DISEASE.
Why are long/ broad contact points bad?
HARDER to CLEAN –> Increased risk of PERIODONTAL DISEASE + SECONDARY CARIES.
3 advantages of a crown compared to a direct restoration?
- Occlusal pattern can be made to conform to existing occlusion or to a reorganized occlusion.
- Can take into account guidance on excursive movements.
- Can be made with ideal contact points and appropriate contour.
What teeth are unrestorable (3)?
- Cracked tooth: crown to root extension.
- Split tooth: crown and root.
- Vertical root fracture.
- ANY CRACK THAT HAS EXTENDED ONTO THE ROOT SURFACE IS UNRESTORABLE.
When does a fractured cusp often occur (what clinical situation)? Why does this occur?
- LARGE restorations surrounded by THIN PIECES OF BONE.
- Occlusal forces cause WEDGING FORCES which PUSH OUT ONTO THE REMAINING CUSPS.
What can be used to prevent a fractured cusp? How?
- Can use a CROWN.
- Ensures forces propagate along the LONG AXIS of the tooth and thus PREVENT PROPAGATION OF CRACKS.
What did lucarotti find the survival of molar tooth to reintervention with regard to type of restoration to be for MOD amalgam vs crown at 15 years?
- MOD: 34.
- Crown: 60.
What is a cracked tooth?
Tooth that is cracked but remains in a SINGLE PIECE.
- Can be into enamel, dentine or pulp.
What can be used to stop crack propagation in a cracked tooth?
a CROWN (prevent crack from reaching pulp where it will allow ingress of bacteria and thus infection).
What are telescopic dentures?
DOUBLE CROWN DENTURES - Consist of double crowns
- Primary/inner crown: Cemented to the abutment.
- Secondary/ outer crown: Attached to the denture.
2 ways in which crowns can be used with removable prostheses?
- Rest seat preparations for denture.
- Telescopic/ double crown dentures.
3 downsides of telescopic dentures?
- Difficult and very technique sensitive.
- Expensive.
- Require excellent maintenance to avoid secondary caries (failure of one crown could lead to failure of the entire prosthesis).
3 ways in which a crown can fail?
- Biological failure.
- Mechanical failure.
- Aesthetic failure.
What are the 2 types of biological crown failure?
- Secondary Caries.
- Periodontal issues (periodontal disease, gingival inflammation, encroachment of the biological width).
What is the biological width? How big is it?
Junctional epithelium + connective tissue. Around 2mm long.
Where do we want the margin of our crown to lie? Why?
- Usually 3-4mm above bone crest.
- To avoid encroaching into the biological width (avoid inflammation and bone loss).
When is the biological encroached? What will occur as a result?
- When the margins of a crown are placed TOO SUBGINGIVALLY/ TOO CLOSE TO CRESTAL BONE.
- If crown margin within biological width, there will be too short of a distance between the crown margin and the bone crest –> gingiva will REJECT THE RESTORATION, INFLAMMATION AND POTENTIALLY BONE LOSS.
3 types of mechanical crown failure?
- Ceramic fracture.
- Occlusal wear
- Cement failure.
3 types of aesthetic crown failures?
- Visible margin.
- Colour.
- Shape and size.
3 complications that can arise during crown preparation?
- Heat generation and pulp damage.
- Exposure of dentinal tubules (increased sensitivity + potential ingress of bacteria).
- Direct pulp exposure due to preparation.
5 occasions to not use a crown?
- Lifestyle factors which adversely affect oral health.
- Active caries or periodontal disease.
- Inadequate crown height.
- Inadequate access for tooth preparation or impression taking.
- When there is a more minimally invasive option.
4 lifestyle factors that lead to crowns being contraindicated?
Risk factors for DISEASE.
- Sugar intake.
- Oral hygiene.
- Smoking.
- Parafunction.
4 types of active disease that lead to crowns being contraindicated?
- Caries.
- Periodontal disease.
- Periradicular disease.
- Tooth wear.
What can lead to inadequate access for preparation/ impressions (3)?
- Sclerosis: scleroderma, post-radiation changes.
- Post surgical changes.
What are 3 potential options after crown failure?
- New crown.
- Post retained crown.
- Extraction.
What are the 2 parts of the preoperative assessment for crowns?
- The patient.
- The mouth.
3 main questions to ask uyourself when considering the PATIENT for providing a crown?
- Can I meet the patient’s expectations?
- Can the patient tolerate the treatment? (anxiety, gagging).
- Will they be able to maintain the restorations (physical impairment - tremors, arthritis).
8 questions to ask when considering the MOUTH for providing a crown?
- Is the plaque control adequate?
- Is there active disease?
- Has the risk of damage from occlusal dysfunction been minimized?
- Is there enough tooth tissue? aka Will the preparation be retentive enough?
- Is there enough space.
- Existing occlusal relationships?
- Periodontal tissues? (bone levels-prognosis of tooth).
- Endodontic state?
How can the risk of damage from occlusal dysfunction be minimized (2)?
- Splint therapy.
- Psychological therapy (CBT, hypnosis).
What kind of guidance is preferred when providing a crown? Why?
- CANINE guidance preferred (unless crowning canine).
- If only canine guidance, only have to ensure the crown fits in ICP.
- Group function guidance means tooth must fit in ICP AND EXCURSIVE MOVEMENTS.
What happens if you provide a crown without adhering to the occlusal guidance?
Patient may return with a CROWN THAT HAS FALLEN OUT or PAIN DUE TO INTERFERENCE OF THE CROWN.
What must a tooth be prior to being prepared for a crown?
Tooth must be ASYMPTOMATIC endodontically.
What teeth are likely to become non vital following crown preparation? (2)
- Tooth has restorations very close to the nerve.
- Smaller teeth have higher risk of pulpal damage (ex. lower anteriors).
6 steps you must involve in your records when considering providing a crown?
- RFA.
- Risk factors.
- Clinical assessment.
- Special investigations.
- Diagnoses.
- Treatment plan.
What do you include in RFA for a patient who may receive a crown (2)?
- Presenting complaint.
- Expectations.
What are 3 characteristics that we want to note a patient’s risk factors for when considering providing a crown?
- Caries (sugar intake, OHI).
- Periodontal disease (OHI, smoking).
- Tooth wear (parafunction).
8 things to include in the patient’s clinical assessment for a patient who may receive a crown (8)?
- Extra oral
- Intral oral
- BPE
- OHI
- Hard tissues.
- Wear index/ tooth surface loss.
- Occlusal relationship.
- Guidance
