Post Retained Crowns Treating Endodontically Restored Teeth Flashcards
What is usually different about root filled tooth?
Extensive coronal damage +/- lack of tooth tissue, loss of radicular dentine associated with endodontic treatment, and general long term prognosis less favourable
What are considerations of endodontically treated teeth?
Restorability assessment, resistance to tooth/root fracture, and retention of core and final restoration with dental tissue remaining
What are options for restoring endodontically treated teeth?
Direct restorations, indirect extra-coronal restorations, and post-retained crowns
What happens with decreasing available alternative options?
Extraction
What is a post-retained crown?
A crown which relies for its retention, mainly, on a post which is inserted into root canal system of a root filled tooth
When is a post-retained crown indicated?
When remaining coronal tooth structure is not sufficient for direct retention
Why is a post-retained crown indicated?
To provide extra retention for crown restoration
What should be provided for root-treated posterior teeth?
Some form of cuspal coverage (unless endodontic access is only coronal tissue lost)
What can placing posts result in failure from?
Iatrogenic perforation/root fracture/cement failure
Why do the majority of root filled teeth fail?
Restorative reasons such as non-restorable caries and root fracture rather than endodontic failure
How do you decide whether to restore endodontically treated teeth?
Extent of coronal damage and tooth type, functional demands
Why are posts required in severely broken down teeth?
To improve retention of core material
What significantly improves prognosis in posterior root-filled teeth?
A cast restoration with occlusal coverage/full coronal coverage
What is prognosis for anterior root terated teeth not necessarily improved with?
Crown placement
What is general treatment planning for post crowns?
Assess restorability, assess root treatment status, assess periodontal condition, and assess occlusal relationship
How do you assess restorability?
Clinically prior to embarking on root canal treatment, examine and if appropriate remove caries and assess degree of coronal breakdown
How do you assess root treatment status?
Symptoms, clinical signs, and radiographs
How do you assess periodontal condition?
Mobility and support
How do you assess occlusal relationship?
Study models
What radiographs are indicated in treatment planning for post crowns?
Intra-oral periapical and OPT depending on clarity
How does an intra-oral periapical aid to diagnosis?
Status of periapical tissues, status of root filling, status of periodontal tissues, and root length/morphology
What are stages of deciding whether to re-root treatment or not?
Ensure tooth is restorable first (assess current status), assess for signs and symptoms of ongoing disease clinical and radiographically, undertake (re)root canal treatment if needed then…, start restorative phase quickly to avoid risk of coronal microbial leakage, and proceed with crown/post retained crown ASAP to secure a coronal seal
How do the different post types differ?
Post shape, active/passive fit, surface characteristics, material, and fabrication method
What are the different post shapes?
Parallel/tapered/hybrid
What are the different surface characteristics?
Smooth/serrated/threaded
What are the different materials?
Metal/fibre
What are the different fabrication methods?
Pre-fabricated/customised/lab made (bespoke)
What is an active post?
Engages dentinal walls of preparation upon insertion
What is a passive post?
Does not engage dentine, relying instead on cement for retention
What factors influence post crown success?
Post length, post shape, post surface characteristics, anti-rotation, material, production, and ferrule
How does post length effect post crown success?
Longer post = more retention, at least length of crown, and leave at least 4-5mm apical root filling
How does post shape effect post crown sucess?
Parallel/tapered depends on canal configuration and root shape, tapered less retentive but less destructive
How does post surface characteristics effect post crown success?
Smooth/serrated/threaded, threading into canal may cause damage especially tapered self-tapping , serrated preferred
Why is anti-rotation required?
To stop parallel/round posts from rotating
How does material effect post crown success?
Metal, fibres reinforced resin, flexural strength, elasticity rigidity, force transfer stress fracture
How does production effect post crown success?
Preformed vs cast/fabricated in a lab, recoverability, removal, and replacement
What height should ferrule be?
Maximum conservation of coronal dentine height to ensure crown margin is
placed apical to start of post
What is function of ferrule?
Helps protect from root fracture by transferring load on crown onto root rather than post root interface
What is scenario with a ferrule?
Crown locks post to root so rotational forces are transferred into and along whole root structure
What is scenario with no ferrule?
With crown and post interface at point of entry to canal we now have a screwdriver effect and rotational forces are transferred laterally to root, so tooth is now screwed and will split
What is scenarios with an internal ring ferrule?
Tet unproven to be superior to a conventional ferrule and requires a special bur to cut shape so may not conform to tooth appropriately
What are direct techniques of post and core systems?
Preformed metal post and core (amalgam/composite) and preformed fibre post and core (composite)
What are indirect techniques of post and core systems?
Cast gold alloys and hybrid (prefabricated metal post/cast gold core)
What post systems are used at dental school?
ParaPost Fibre White and ParaPost XP
What is ParaPost Fibre White?
Fibre reinforced preformed passive fit textured post
What is ParaPost XP?
Metal, preformed, textured
What are features of direct technique post and core systems?
No laboratory, overall clinical time saved, metal/fibre posts, anterior/posterior, and fiddly without experience
What are features of indirect technique post and core systems?
Traditional, cast gold/hybrid (e.g., titanium post and gold core), usually anterior, require straight canals, more time consuming, and more stages greater risk of errors
What are features of metal posts?
Traditional, stronger?, more likely to cause root fracture?, metal shines through in translucent crowns, can corrode, and removable with ultrasonics and burs
What are features of fibre posts?
Direct adhesive technique, less strong but less likely to cause root fracture (strengthen root?/fails first?), more aesthetic under some ceramic crowns, no corrosion, and removal usually damages tooth to beyond restoration
What should canal length of post be?
= crown height
What should canal width of post be?
Remaining dentine 1mm
What does parapost indirect system consist of?
Standardised increasing diameter post drills with corresponding textured burn out post (for lab) passive plastic impression post (adjustable) and metal temporisation post
What is parapost preparation technique?
Removal of coronal root filling, once GP is removed move onto parapost system of choice, and post space preparation
How is coronal root filling removed?
Start with ultrasonic scaler to identify canal and its direction and initial preparation of canal with Gates-Glidden burs smaller to larger
How is post space prepared?
Parapost drills start small and work up, and for safety use a hand-chuck
What are features of a hand chuck?
Shank with size banding, long narrow shaft for access and flexibility, and non cutting tip to follow canal
How can rotation be prevented?
By placing a groove in canal to serve as an anti-rotational element
Where should this groove be placed?
In area of tooth with greatest bulk of tooth tissue remaining
What is post and core direct technique fibre post?
Prepare crown margins, prepare canal (as for metal post), try in post (check occlusion), cement post, build up composite core (remove colour ring 1st), prepare core, and make a good impression
What is Nayyar core?
Coronal-radicular amalgam core
When can Nayyar core be used?
If reasonable amount of coronal dentine
What do some people advocate instead of amalgam?
A reinforced glass ionomer/paracore
What does Nayyar core remove need for?
Pins which weaken remaining dentine
What are points for success of restoring endodontically treated teeth?
Adequate apical seal, minimum canal enlargement, adequate post length to crown ratio, vertical stop to prevent rotation, presence of ferrule, good impression/cementation technique, and inter appointment seal and rapid provision
