restorative endodontic interface - posterior Flashcards
indications for direct posts on anteriot teeth
ferrule required
need dentine remaining
indications for cast posts and cores on anterior teeth
not a lont of dentine
replacing a cast post
no ferrule - not ideal
possible tx for this lateral incisor
lot dentine remaining - maybe try build up with core material
use fibre post (Dt light posts)
when building up a core with fibre post what must you have
rubber dam - should be using resin cemetn which needs optimal moisture and control conditions
doesn a tooth need a post?
clinical judgement
- could you build up a core?
- esp anterior tooth
- enough dentine remaining?
- post should be last resort as lost so much tooth structure
- esp anterior tooth
- does toth need a post crown
- restrorative cycle
- want to stay simple for as long as possible before progressing
3 options for tx of endo tx tooth
- build up core (anterior or posterior teeth)
- fibre post - some dentine
- cast posst - so little dentine left and non-optimal ferrule
11 stages in cast post prep
- Assessment
- Design a new restoration
- Provisional restoration
- Gutta percha removal
- Post space prep and anti rotation features
- Provisional construction
- Impression
- Lab prescription
- Provisional placement
- Try in
- Fit
things to assess for in RCT
- when was it done
- how was it done
- is it acceptable (to apex, voids)
- has it been leaking - open for 3 months?
was it done using sodium hypochlorite?
- not sure -> consider redo it before post placement
why is it important to assess RCT before post placement
hard to dismantle one post placed -> root fracture possible
need to be sure foundations sound and root canal clean before placing definitive post retained crown onto tooth
gold standard for RCT
dental dam and sodium hypochlorite
3 aspects of favourable post design
- parallel sided (avoids ‘wedging’)
- non threaded (avoids incorporating stress)
- cement retained (buffer between masticatory forces post and tooth)
masticator load transfer by post
tapered pst act as wedges leading to root fracture
parallel sided posts do not cause wedging
posts retained solely by cement tend to distribute masticatory forces evenly to the supporting tooth, the cement acting as a buffer between post and tooth
5 considerations when designing new restoration
- How long will post be?
- Have you got a ferrule?
- How wide?
- 3-5mm remaining GP at apex beyond post
- Is canal straight?
- How much space for the core – need to factor in type of crown to be placed
- Need a retentive core to retain crown Or else no mechanical retention for crown – aim (function, aesthetics for pt)
why do you need a retentive core
Need a retentive core to retain crown
Or else no mechanical retention for crown – aim (function, aesthetics for pt)
assess space for core and factor in type of crown to be placed
ferrule preparation
place crown margins on solid tooth tissue rather tahn restorative material
1.5-2mm collar dentine extending supragingivally 360o circumferentially of post
ferrule effect
when place crown on, get some bracing in coronal portion of tooth where crown meets ferrule preparation and cement retains crown in place
- resistancce to rotational force and leakage
core design (2 main aspects)
- core - taper and length important
- 6 degree taper
- length required - to allow 2mm clearnace incisally for MCC
when to consider provisional restoration factors
before begin dismantling restorations
4 possible provisional restorations
provsional post core crown (temp bond)
immediate denture
dressing? Zinc oxide eugenol
essex retainer with teeth on
provisional post core crown (temp bond)
use
possible issue
especially if dismantling an exisiting crown
- can take putty matrix and make provisional post core wtih temp bond
- some posts in para post kit
chewing can dislodge provisional crown -> microleakage
issue with immediate denture as provisional restoration
can cause gingival problems - margin, haemorrhage (OHI not ideal)
use of dressings as provsional restorations
zinx oxide eugenol
not aesthetic but might prevent leakage
removal of gutta percha to
create post space
cons of dental dam use in removing GP
can obscure long axis of tooth - relatively easy to lose bearings
needs to be removed for definitive impressions
steps in removing GP
- dental dam
- soften GP
- gates glidden to minimum size 3 (straight part of canal only)
- use working length and rubber stopper on GG
- essential to leave 3-5mm GP in apical third
- check GP plug remains
how much GP needs to be retained in apical third
3-5mm
how to soften GP
heat - super endo alpha
solvent - eucalyptus oil
why do you need to use rubber stopper and know working length when removing GP
need to leave 3-5mm GP in apical third
so need to know exactly how many mm of GP taking away from known coronal measurement point
GG3
0.9mm
3 ways to check GP plug remains
loupes
microscope
periapical radiograph
once obturated what is sensible practice
to leave tooth for 24hrs to allow AH plus (resin sealer) to set inside the tooth
what is the risk if there is post prep at same appointment as obturation
risk disruption whilst removing GP
para post components
- provisional post (titanium)
- use in conjuction with protemp and putty matrix to construct provisional post crown
- burn out post (not important)
- para post drill (colour coded)
- impression post
- smooth sided
- placed into tooth when taking deficintive impression for indirect cast post
para post narrowest post space bur
0.9mm - same as tip for GG3
how to use para post drills
parallel sided
run through sequence to desired size
post space prep
- heat source to remove some GP (super endo alpha)
- start with small gates glidden (2) with rubber stopper on to remove some coronal GP
- irrigate to wash out debris
- GG again – brushing motion
- Irrigate
- Larger GG size (3) to remove more GP
- Irrigate
- Rubber stop on parapost drill to same length GG got to (dentine collar is reference point), in slow speed do not force drill
- if feel hard surface, stop
- may have angulation wrong – risk perforation of tooth
- Irrigation – important for efficiency of parapost drill cutting to wash out debris
- Continue this sequence up parapost drills – widen post space
- Move up sequence of parapost drills
- Try in pre-op putty matrix once feel completed to ensure it fits
- Fabricate provisional post crown
provisional construction
- Try in provisional parapost
- Inject protemp into putty matrix and make sure firmly place into mouth
- Remove as one (provisional parapost retained in the protemp)
how to adjust provisional parapost
if too long cut with Mons wire cutters (as titanium)
- cut from apical end
- leave little nail head in place - retain para core
how long do you have provisonal para post
2mm short of incisal edge of adjacent tooth
how to take defintive master impression
Definitive master impression
- Use a putty wash technique – light body wash injected round prep
- incorporate all margins
- ensuring post is fully covered with wash material
- Place putty impression over the top
Remove and impression post should be retained – send to lab with instructions to make cast post and core
anti-rotation notch/groove
role
cut into preparation to try and prevent rotational displacement
anti-rotation notch/groove
placed when and why
If sufficient coronal structure is present rotation is prevented by a vertical coronal wall
- If coronal dentin is absent then a small vertical groove in the canal serves as an anti rotational element
- Located in the bulkiest area of the root, usually lingual
lab presciption for definitve restoration (sent with definitive impressions)
please construct a cast post and core
para post (colour)
core 6 degree taper
please leave 2mm space in occlusion for crown
enclosed registration/opposing impression/ (shade - making crown as well)
try in
received post and core back from lab
- check post space for temp bond, debris etc (ultrasonic cavitron to clean out)
- irrigation chlorhexidine 0.2% - can be under dental dam if you want
- can be slippy - protect pt airway
- dry paper points
- ensure fits around prep
- do you have enough occlusal cleanrance?
- be sure before cementing in
fit
cement
- be careful not to fill post space - prevent seating
- use firm apical pressure - to ensure seated properly
- remove excess
can ask lab for provisonal acrylic crown
practice fit sequence
- slick enough to get everything in right position (esp if placing crown too)
issue if not seat restoration properly
harder to remove
what to check for when taking crown impression/fitting MCC
no excess and no gingival bleeding
when may you ask for a provisonal acrylic crown from lab?
e.g. if leaving in cast post in place for a while
can be useful as protemp provisional with post is now useless
- if have another putty matrix can construct another protemp restoration – but challenging
what may occur if get post core and crown made on same impression
one may fit and other won’t
but potentially less visits for pt
impact of NHS fee for post core
Metal alloy £39.95 (para) (lab fee £31) DTS
Non-precious metal £20.75 (lab fee £18.75) Leca
no large profit
post core is in what stage of restorative cycle
last resort
impact of post core being last resort tx on planning
may only get 1 go at doing it
ensure
- quality of root treatment
- ensure RCT right
- ensure post cornw fit right
issue here
post placement off to both sides and not deeply placed
issue here
parapost drill has gone through side of tooth
methods of post removal (6)
- ultrasonic (tips £££)
- trephan e.g. Masseran
- eggler device
- moskito forceps (screw retained)
- sliding hammer
- anthogyr (safe relax)
Maseran useful for removal of post by
coring around fracured post insturements/posts
hybrid post removal technique
US and masseran
core a channel around fractured pience and grab with Masseran tube
intact/post core removal fee
£0
can be timely for no £
may consider referral as not routinely done in GDP
fractured post removal fee (below dentine collar)
£18.20
consider referall
why are referral consider for post removal
can be timely for little £
can break an expensive US tip in process
may also need dental microscope £££
5 post removal problems
- you can’t remove it
- root fracture (immature or delayed)
- render tooth unrestorable
- post space too wide
- break post
tell pt as part of consent process
planning treatment key
if can do simple (build up core (avoid post)) - BEST
leave option for post at later date - as posts do not strengthen teeth
endo tx posterior teeth restorations avoid
posts at all costs
3 core materials for posterior teeth
composite
amalgam
Glass ionomer
composite as a core material
- most commonly used core material
- tooth coloured as good aesthetics
- bonds to tooth structure
- technique sensitive, so moisture control required
- used with fibre posts
amalgam as core material
- tend to avoid as retention is required
- poor aesthetics
- core cannot be prepared straightaway - needs 24hrs to set
- avoid pinned amalgams - ideally want bond to tooth
if assessing an amalgam core and unsure on its status (age, if secondary caries under) what to do
remove if in doubt to check what is underneath core
glass ionomer as a core material
not really used as it absorbs water and core expands in size
examples of core materials and how to use
- Biodentine
- Paracore (available in GDH)
can cure and prep tooth straight away (unlike amalgam)
utilise pulp chamber space
undercuts in roof of pulp chamber
cut 1-2mm into orifice
- inc SA for bonding, and mechanical retention
why to cut 1-2mm into orifice for core build up
inc SA for bonding, and mechanical retention
restoration of endo tx posterior teeth considerations
molars and premolars have narrow roots
- post preparation may lead to a strip or lateral perforation in these teeth
disadvantages of posts in molars outweigh advantages
core retention can be obtained from physical undercuts and dentine pins or preferably bonding agents
disadvantages of posts in endo tx posterior teeth
post preparation may lead to a strip or lateral perforation in these teethcurved roots
- perforation risk
- longer posts not possible retention poor
restoration of molars if no coronal tissue
posts may be inserted for a short distance into largest straightest root canal
restoration of molar teeth in general
- most cases have sufficient natural retention for a core
- at least 1mm ferrule of definitive coronal restoration required unless all-porcelain restoration
- nayyer core (amalgam) should be avoided
if posts need to be used in posterior teeth
use them in
- distal roots of mandibular molars
- palatal roots of maxillary molars
normally provide a large and usually straighter canal for post insertion
minimum tx required for endondontically treated molar or premolar
cast restoration with occlusal coverage
e.g. MOD onlay
why is it important to give coronal coverage to endo tx posterior tooth
94% of endodontically treated molars receiving coronal coverage were successful compared with 56% of occlusally unprotected teeth
what to consider prior to RCT of posterior teeth is restorations going to involve more than one surface
reducing cusp heigh by 1.5-2mm
3 reasons for posterior teeth cuspal protection
- prevent catastrophic fracture
- e.g. furcation
- maintain coronal seal
- prevents microbial ingress
why in GDH do we place coronal protection of endo tx posterior tooth
increases longevity of the tooth by placing an extra coronal restoration
short, narrow, spindly roots are easily damage
premolar restorations after endo
cuspal coverage should be considered first option
posts should only be used if roots are adequately long, bulky and straight
- only one canal should be used
- radix anker posts produce extreme stress on root structure (threaded, screw posts)
restoration when no post needed
build up with composite, paracore
restorative when dentine remaining but not enough to build up core
fibre post (need ferrule)
restorative when very little remaining tooth structure and no ferrule
indirect cast and post crown
tx for posterior teeth
avoid posts at all costs
1st line is cuspal coverage (MOD onlay)
but after consider extraction and aesthetic replacement
