Indications for crowns and the preoperative assessment Flashcards
What is a crown?
a full coverage extra-coronal restoration
it is an indirect restoration which is cemented/luted to a prepared tooth
what materials can be used for a crown?
- gold allow (precious metal alloy)
- ceramic
- metal bonded to ceramic
- non preciouus metal allow (e.g. CoCr, NiCr)
What are some indications for crowns?
- repeated failure of direct plastic restorations (e.g. composite/amalgam)
- difficulty achieving adequate contour, contact point and occlusal contacts with a direct restoration
- minimise risk of tooth fracture
- aesthetics
- to include design characteristics to accommodate a metal based removable prosthesis
- bridge abutment
- replace an existing crown
what can the problem with inadequate occlusal contacts in large direct restorations?
Increased risk of restoration fracture and subsequent micro leakage and secondary caries
what can the problem with inadequate contact points in large direct restorations?
- contact point not achieved
- increased food packing
- difficulty cleaning and maintaining restoration
- risk of periodontal disease and secondary caries
what can the problem with inadequate contour in large direct restorations?
- difficult to maintain oral hygiene, increased risk of caries and periodontal disease
- poor aesthetic outcomes
what types tooth fracture is deemed unrestorable?
a cracked tooth - extending into root
a split tooth
vertical root fracture
(anything where the fracture extends into the root)
what types of tooth fracture can be managed with a crown?
fractured cusp, limited to the crown
cracked tooth, limited to the crown of the tooth
how can a crown help prevent cracks on a tooth?
the crown helps to direct occlusal forces straight down the long axis of the tooth
why do root treated molars have a higher risk of root fracture?
due to the amount of tooth lost due to caries, caries removal, access cavity etc
how can crowns be used a useful denture abutment teeth
- crowns can incorporate rest seats within metal
- long guide planes to help with denture retention
briefly summarise telescopic (double) crown dentures
removable dentures that fit precisely over teeth prepared with an ‘inner crown’
- this is a expensive, difficult and very technique sensitive procedure
- requires excellent maintenance to avoid secondary caries
in what scenario would it be acceptable to crown a tooth for a bridge abutment tooth?
where the abutment tooth is heavily restored and you can justify preparing the tooth for a full coverage restoration
- would not be acceptable to prepare a unrestored/minimally restored tooth
what are the biological causes of crown failures?
- secondary caries
- periodontal problems - perio disease, gingival inflammation, encroachment of the biological width
what is the biological width?
the distance between the connective tissue and junctional epithelium of a tooth and the root surface
on average what height above the crest of the bone is the biological width found?
3-4mm above the crest of the bone
what happens if the crown does encroach on the biological width?
there will be too short a distance between the bone and the crown margin and the gingiva will start to reject the restoration - this can cause inflammation and result in bone loss
failure of a crown - what are some examples of mechanical failure?
- ceramic fracture
- occlusal wear
- cement failure
failure of a crown - what are some examples of aesthetic failures?
- visible margin
- colour
- shape and size
what lifestyle factors could indicate NOT to use a crown?
life style factors which are risk factors for disease:
- high sugar intake
- OH
- smoking
- parafunction (causing tooth wear)
active disease:
- caries
- perio disease
- peri-radicular disease
- tooth wear
when not to use a crown?
- lifestyle factors which adversly affect oral health
- active caries/perio
- inadequate crown height
- inadequate access for tooth preparation or impression taking
- when there is a more minimally invasive option
what should you consider about the patient when assessing them for a crown?
- can you meet the patients expectations
- can the patient tolerate the treatment (gagging, anxiety)
- will they be able to maintain the restorations (physical impairements, lack of motivation)
what should you assess in the mouth when carrying out the preoperative assessment for a crown?
- is the plaque control good enough
- is there active disease
- does the risk of damage from the occlusal dysfunction need to be minimised (splint therapy, phsycological therapy)
- endodontic state of the tooth (vital, non-vital, likely to become non-vital,) - must be asymptomatic
- is there enough tooth structure for preparation
- is there enough space
- will the crown conform with the existing occlusioon
what would you record in patients notes for assessment of a crown?
RFA - presenting complaint, expectations
Risk factors - caries, perio, tooth wear
Clinical assessment:
- E/O
- I/O
- BPE
- OH
- Chart (teeth)
- Wear index/tooth surface loss
- Occlusal relationship
- Guidance (canine, group function)
Special investigations
Diagnosis
Treatment Plan
