Posts and Cores Flashcards
Give the radiographic requirements for a post to be placed
- Prev RCT with good apical and coronal seal, obturation within 2mm apex and well condensed
- If no RCT then assess and do elective RCT
- No radiolucency
Root anatomy
- Wide width
- Min 1:1 crown:root but ideally 2:1
- Min or no curvature
- Select largest canal (when mul root)
- No external or internal resorption
Bone
- No or min bone loss
- Post must be able to extend 4mm subcrestal
- No caries
- Absence of fracture lines
Give the clinical requirements for Post placement
- No sinus
- No abscess
- Not TTP
- No exposed GP
- No caries
- Min 1-2mm ferrule extending 75% circumferential around tooth
Stable perio
- No Bleeding pockets >4mm
- No pockets >5mm
- No pus
- BOP <15%
- No mobility
- No furcation
Occlusion
- Min 2mm interocclusal space after core placement
- Group function to balance occlusal forces through PDL of multiple teeth
- No toothwear or bruxism habits
Risks of Post placement
- Perforation
- Root fracture
- Post fracture
- Infection requiring re-RCT
Increases risk of post fracture
- Bruxism
- Class II div II +- deep overbite
- Mild Class III/ edge to edge
Give advantages and disadvantages of Direct and Indirect Post
Direct
- Same day placement and lower cost (prefabricated)
- But less accurate fit , not suitable for wider canals and not suitable if less than 2mm ferrule
Indirect
- More accurate fit , suitable for wider canals , suitable when less than ideal ferrule remaining
- Requires add appointments and more costly
What materials can Posts be made of?
Metal
- Cast gold
- Stainless steel
- Brass
- Titanium
Ceramic
- Zirconia
- Alumina
Fibre
- Quartz
- Carbon
Give advantages and disadvantages of Metal, Ceramic and Fibre posts
Metal
- Radiopaque
- Easily retrievable
- Better fit to overlaying metal crown
- BUT poor aesthetics , risk of foot fracture and corrosion
Ceramic
- High flexural strength and better aesthetics
- BUT difficult to retrieve and technique sensitive (diff to equally spread silanating agent )
Fibre
- Allows light cure through post and more closely replicates root modulus of elasticity
- BUT Difficult to retrieve , technique sensitive and less radiopaque
What is the general consensus for when should posts be placed in molar , premolars and anterior teeth?
Molars
- Avoid (usually suff retention for core within pulp chamber)
- If no coronal tissue remaining and lim pulp chamber depth then place post into largest and straightest canal for short distance
Premolars
- Cuspal coverage rest first option
- If need a post then use fibre post into largest and straightest canal
- If insufficient tooth structure for ferrule then use cast posts
Anteriors
- Bonded rest like veneers or dentine bonded crowns first options
- Posts as last resort and when considerable loss of coronal tooth tissue and retention of coronal rest would be diff (post space prepared immediately after obturation and following crown prep)
How to decide on what post to choose?
- Fibre post preferred when sufficient ferrule (1.5-2mm of remaining sound dentine on more than 75% tooth circumference)
- When no ferrule then used cast / prefabricated metal post and core
- Or when no ferrule consider surgical crown lengthening or orthodontic extrusion
What are the fibre post sizes and colours? What teeth should they be used with?
Size 0.5 = Black = Central and lateral mandibular incisors
Size 1 = Red = Central and lateral mandibular incisors / M&D canals max molars / Max and Mand premolars / M canal Mandibular molar
Size 2 = Yellow = Lateral max incisors / D canals mand molars / P canal max molars / Max and mand canines
Size 3 = Blue = Max central and canines / P Canals max molars / D canals mand molar / Large or wide canals
Technique for canal prep for Post placement
- Determine Post width and length (aim for 3-5mm GP remain at apex) from radiograph
- Dental dam
- Remove GP with 3 GG
- Use Pre-shaping drill (black) to complete prelim prep (determines the final depth of post)
- Chlorhexidine as lubricant, coolant and cleanser with the drill
- Use a endo rubber stopper on shaft of drill
- Always drill along long axis of tooth and positioned within canal (GP feels softer than dentine and if bits of GP come away with drill in correct place)
- Remove debris from canal with CH and dry with sterile paper points
- Use Post prep drills in order starting with Black , Red, Yellow, Blue
- Ideally final canal prep allows space for post and 30 microns around post for bonding materials
Technique for DT light fibre post placement
- Try in post and slide rubber ring to mark desired pos with locking tweezers
- Remove and cut with diamond bur to length that will provide suff post height that a core can be built
- Irrigant 0.2% CH in luer-lok syringe and dry with sterile paper points
- Apply 37% phosphoric acid etc for 15secs to canal and coronal dentine then rinse 10 secs
- Blot canal with paper point to remove excess moisture
- Apply 2 consecutaive coats of Scotchbond adhesive with Composibrush to canal and coronal area without wiating between coats
- Remove excess with paperpoints and gently air dry
- Light cure 10-20secs
- Clean fibre post with alcholo
- Apply one coat adhesive to post and lightly evap solvent with air for 5-10sces and light cure 20secs
- Discard first 2-3mm CORECEM to eliminate prev mixing and voids
- Apply CORECEM with disposable tip into canal (start apicaly and withdraw towards pulp chamber)
- Immediately seat post and maintain Pressure on post and cure 60secs
- Construct core build with CORECEM
*Or use Scotchbond adhesive , RelyX fibre post and RelyX cement (RMGIC)
Post removal technique
- Direct access to post by removing all coronal obstacles
- Drill orientation hole with pilot drill
- Use removal drill at 15000 rpm begin drilling within pilot hole (this hollows out the post)
- Use max P to ensure entire length of post reached
- Use Peeso reamer #2 safe tip and drill through hollowed post with P applied peripherally
- Stop drilling when cement reached
- Take control x-ray to verify direction and length with corresponing size insturment inserted entire length
- Use pre-shaping drill of the post for required corrections in direction or length
- Use corresponding size finsihing drill in post kit to remove any remaining quartz fibres and rinse well
- RCT and can retreated and new fibre post placed
Indirect post impression and temporisation technique stage
- Assess gingival condition
- Select rigid tray and apply adhesive and leave for 10mins
- Place gingival retraction cord with angulated cord packer (pre soak with ferric sulphate or aluminium sulphate in porcelain to avoid staining)
- Insert impression post (must be retentive) and serrate with high speed so at least 2mm interocclusal space present
- PA to confirm post prep pos
- Remove retraction cord and assess gingivae to ensure adequate haemostasis
- Wash and dry
- Syringe light bodied PVS or medium body polyether around prep, into gingival crevice and across occlusal surfaces on same arch
- Take impression with medium / heavy PVS or medium polyether and await final set
- Remove impression and inspect
- Take opposing arch alginate impression
- Take bite reg with silicone bite reg pastes in ICP
- Place temp post and build up core and place temporary
Send to lab saying
- cast post and core constructed
- Shade
- Request sandblasting of fit surfaces
- Casts articualated to jaw reg provided
- Use RMGIC like Rely-X for cast post cementation
What is a core build up?
- Internal part of tooth built up with restorative material to replace lost tooth tissue
- Provided retention and resistance for definitive rest
