Restoration of Endodontically Treated Teeth Flashcards
once a tooth is RCT treated the tooth is:
compromised
after RCT the teeth become:
softer and more susceptible to decay, fracture and breakdown
what are the considerations when deciding on restoring an endo treated tooth
- evaluate the existing root canal- is it sound? appear adequately filled? is there a PARL?
- evaluate if the tooth is restorable: how much tooth structure is left? will you need a post? will you need a build up?
- evaluate how important is this tooth in the patients overall treatment plan
- evaluate how important this tooth is in the patients functioning
- what might be needed to properly restore this tooth beyond a crown?
what needs to be considered in the adequacy of the root canal
- is the tooth asymptomatic? hot, cold, percussion
- are the canals well filled? short fill, pathy appearance
- does the apex appear sealed? puff of sealer
- is there any suscpicion of apical pathology? PARL
- is there a temporary restoration present? IRM in access
- is any restoration present sealed protecting the RCT from the oral environment? temp crown, sealed crown
- how long has the present restoration been present?
- long standing temporary or lack of proper seal from restoration?
- deep caries present?
what are the considerations in tx planning
- is the tooth to be restored in a useful function in the patients occlusion?
- what is the prognosis of the restoration you want to place on the RCT treated tooth?
- is the pt a bruxer or grinder?
- is the patient home care adequate
when do you examine the restorability of the remaining tooth structure
prior to the RCT
why do we need to examine RCT teeth more carefully and consider crowning RCT teeth quickly
- once pulp has been removed and nerve sensation has stopped, the tooth loses its ability to monitor changes in proprioception meaning you can bite harder on these teeth before you feel pain or discomfort
- in an RCT tooth, there is a loss of structural integrity from a variety of sources (access, caries, bone loss from infection)
- the tooth is less strong and both of the above criteria result in a higher likelihood of fracture
what is the primary reason to crown a tooth
prevent fracture
what fractures have a favorable prognosis
- fracture in enamel only or fracture in enamel and dentin
- fx line does not extend apical to the CEJ
- no associated perio probing defect
- pulp may be vital requiring only a crown
- pulp has irreversible pulpitis or necrosis, RCT is indicated before crown placement
what fractures have questionable prognosis
- fracture in enamel and dentin
- fracture line may extend apical to the CEJ but there is no association perio probing defect
- there is an osseous lesion of endo origin
what fractures have unfavorable prognosis
- fx line extends apical to the CEJ extending onto the root with an associated probing defect
posterior tooth fractures can occur becuase:
- greater occlusal forces
- divided occlusal surface (cusps and fossa)
- fillings weaken tooth ability to hold together
why are vertical fractures of posterior teeth more likely
- occlusal forces are more inline with the vertical axis of the tooth
when is cups coverage on posterior teeth after RCT recommended and why
always to prevent fracture
crowns ______ significantly improve the success rates of endo treated anterior teeth when ample structure remains
did not
crowns significantly improved success rates of endodontically treated ____-teeth
posterior
when should crowns be placed on RCT posterior teeth
as soon as possible
crowns are only indicated on RCT treated anterior teeth when:
- they are structurally weakened by large or multiple restorations
- they need substantial changes in form or color that cannot be achieved by more conservative means
for crown preparation why do you want to maintain the natural tooth structure as much as possible
because it is the strongest support of a crown
a crown needs at least ______ for a ferrule
2mm
if sufficienct natural tooth structure remains:
a build up/core will fill the RCT access and chamber to restore the lost tooth structure
____ are often used to help retain a core build up
pins
which is more common for a core material now: amalgam or composite
composite
what are the advantages and disadvantages of amalgam as a core buildup material
- A: strength
- D: not retentive, does not bond, more tooth reduction needed, can be hard to get out if you have to redo the endo
what are the advantages and disadvantages of composite as a core build up material
- A: usability, bonding, more conservative tooth reduction
- D: not as strong
when do you use a post
if tooth structure is missing and restorability is compromised but not condemned
how does the post help the core build up
adds strength
when do we use a post
- when RCT teeth have inadequate tooth structure to retain a core
- in teeth that have lost more than 50% of coronal tooth structure
- in single rooted teeth since the anatomy of the pulp chamber does not offer mechanical retention for a build up
- in teeth with significant response to lateral forces of occlusion
why do we not use a post
- if we dont need a post to retain a build up
- preparation of a post space adds risk to the restorative prognosis
- higher likelihodd of fracture or perforation
- narrow roots
- curved roots
what is the purpose of a post
to retain the core in a tooth when there is extensive loss of coronal tooth structure
are the needs for a post the same between anterior and posterior
no
if the tooth has darkened you can try:
- internal bleaching
- possible veneer or composite
why is a veneer risky for tooth discoloration
difficult to mask the color change
how is internal bleaching done
- in access hole, place bleaching material and seal the access with a temporary fill
- may need to be repeated several times
- can last for a reasonable amount of time and may need to be touched up in the future
when do you need a post in the anterior
when more than 50% of coronal tooth structure has been lost post and core will be needed for retention of a crown
the post and core is meant to resist ____ forces which could cause:
lateral; crown to dislodge
how do you decide when to place a post/core/crown versus extraction and implace
- factors such as:
- remaining tooth structure
- patient occlusion
- patients habits
- ferrule availability
-crown lengthening may be needed - pt desire for esthetics
- patient details- age, meds
what is a ferrule
the vertical axial wall that encircles the tooth which a crown will use to resist fracture
when is a ferrule desired
every time a crown is done
without the proper ferrule:
root fracture is much more likely on anterior teeth due to high lateral forces in mastication
when is post not needed in a posterior tooth
when remaining tooth structure has large access and a shorter clinical crown
are posts common in molars
n
what is enough to resist fracture in posterior teeth
a crown preparation with a ferrule in harmonious occlusion with a build up in the access
what is an endocrown
a crown that fills the access with crown material
when would you use a post in posterior teeth
if extensive coronal destruction exists
what root and canal do you use for posterior teeth
the longest and straightest canals
what canal do you use in maxillary molars and which do you AVOID
- use: palatal root of max molars
- AVOID: buccal roots of max molars
what canal do you use in mandibular molars and which do you AVOID
- use: distal roots of mand molars
- AVOID: mesial roots of mandibular molars
why are premolars scary for posts
significant variation in root length, curvature, bifurcation and width
use a post in premolars only in roots that have:
ample bulk and a straight root anatomy
use a post on a premolar if:
- substantial tooth structure is missing- post is placed in canal to replace lost cusp
- if the tooth is under substantial occlusal forces
- if the height of the tooth in MI is tall
what is the possible exception for posts
- mandibular 1st premolar
- the occlusion on mandibular first premolar is usually favorable
- patient habits and conditions need to be assessed to ensure occlusal forces are not heavy or lateral
- it may be possible to avoid both a crown and post on this tooth after RCT with a conservative access fill
as a general rule it is preferred to NOT place a post unless:
needed to retain the build up material
using a core build up material only is desired if:
it provides adequate retention and resistance form
why do premolars require a post with extensive coronal destruction
the tooth is much smaller in relation
molars often only need:
a build up and then secondary retentive features such as grooves, boxes, pins, bonding, or utilizing the access hole
what is the most important factor in clinical success
- leave as much tooth structure as possible
why do you want to leave as much tooth structure as possible
the more you take away, the more you have to add and the. more you weaken the tooth and restoration
sometimes you have to leave the tooth ugly because:
it improves retention and strength
what is retention
ability of the post to resist vertical dislodging force
what helps with retention
- post length and taper
- active or passive
- cement used
what is resistance
ability of the post and core to withstand lateral or rotational forces
what helps with resistance
- amount of remaining tooth structure
- post length and rigidity
- anti-rotation features
- presence of a ferrule
what is recommended for the post length and diameter
- 1/2 to 2/3 of the length of the root is ideal
- minimum length at least that of the clinical crown
- 4-5mm of GP left to keep the seal of the GP
when forces are applied near the incisal the result is:
stress (R) concentrated at specific points
a post too short allows the forces to:
act with greater stress leading to a higher incidence of root fracture
a post that does not leave 4-5mm at the apical for the RCT seal will:
compromise the tootht
the post often is too big at the apex and can:
cause root fracture
the apical seal is compromised and therefore:
recurrent infection can occur
as a general rule, what length of molar post spaces increase the potential for root perforation
greater than 7mm apical to canal orifice
post preparation diameter should not exceed:
1/3 of the root at the CEJ
leave at least ____ of sound dentin at mid root
1mm
ideal diameter of post should only be ______ depending on the particulars of the tooth
0.6mm-1.2mm
in removal of GP to create post space, rubber dam isolation is ____
mandatory
how do you remove GP
- soften/melt - heat method
- system B
- flame and endo tool
when can removal of GP occur
at any time
a ______ melts the GP
heated instrument
a warmed plugger _____ the GP vertically
compacts
why are heated instruments used in GP with caution
they can overheat the tooth and cause soft tissue burns if not careful
what is the mechanical method of removal of GP
- canal is instrumented with Gates Glidden and/or Peazo Reamer rotary instrument
- Pink GP should be visualized being removed during the entire use of these instruments
- this should be done SLOWLY
why is there a safety tip on the Gates Glidden and the Peaso
to help decrease perforations
what are the considerations with the mechanical removal of GP
- correct angulation is critical
- do not force bur into hard dentin surfaces
- a slow speed handpiece is used
- Gates used at 800RPM with electric handpiece Peaso used at 1200 RPM with electric handpiece
- no HARD pressure is used the GP is soft and should guide the instrument
what are the steps in mechanical GP removal
- follow the pink GP with gentle vertical movements
- press in gently, pull back and repeat
- you may need to start with a small drill and step up to a larger one depending on the size of the canal
- what angulation
what are the classifications of post systems
- active post vs passive post
- parallel post vs tapered post
- pre-fabricated vs custom post
- fiber vs metal
-describe active vs passive posts
- active posts engage the surrounding root material usually via threads or a serrated edge
- passive posts fit into the canal without engaging the surrounding root material
what is the most retentive post to the least retentive post
- threaded parallel post
- serrated parallel post
- threaded tapered post
- serrated tapered post
- parallel passive post
- tapered passive post
whatis the downside to threaded parallel posts
create higher stress on the root and therefore have a higher incidence of root fracture
what is the downside to serrated parallel posts
high stress at apex and therefore higher incidence of fracture
what is the upside to tapered passive posts being the least retentive
less incidence of root fracture due to least amount of stress on root
how are active posts inserted
screwed into the teeth with a handpiece or special tool to engage the surrounding root surface
passive posts gain their retention and support through:
cementation
describe the custom passive post
resin pattern sent to lab to be cast in metal alloy
what are pre fabricated posts cemented in root with
core build up of composite or amalgam
what are the shapes of posts
parallel, tapered or a combo
- some are serrated
what materials can posts be
metal or fiber
what are the advantages and disadvantages of the custom cast post
- A: anti-rotational properties, core is part of post, can be preservative of tooth structure as the post fits the space
- D: multiple appointments needed
- tapered design is not as retentive
- dark un esthetic core
- higher incidence of root fracture as post is harder material than root and if occlusion is off, post will not break, root will
what are the advantages and disadvantages of the pre fabricated post
- A: increased retention within root, ease of placement, more versatile to a wider range of tooth root shapes, post will often break before root will
- D: post space needs to be slightly larger than cast, core retention to post can be a problem, possible perforation, metal posts still have un-esthetic color
what is the caution with pre fabricated posts
parallel posts have difficulties at times with narrowing of tooth root and can lead to root tip fracture
what type of premolar presents a dillemma with posts
a canal shape that is ovoid
which posts can and cant be used with ovoid premolars
- a pre fab post is not stable on its own as the canal shape allows the post to rock back and forth
- a cast post can be made
- a pre fab post can be used and cemented
- a two pre fab post technique can be used to stabilize the pre-fab post
what is the two post technique
one major post goes to length and height for core build up but canal orifice allows post to wobble
- a minor (smaller) post can be placed into other canal as far down as it can go to stabilize the major post
- then the two points are cemented in the canal together and core build up placed
what is the advantage of the two post technique
it reduces stress on the major post which would have been supported only by cement
when is the two post technique used
mostly for anterior and select premolars
describe the cast post technique
-a red duralay resin impression is made of the post space
- tooth is temporized while duralay is sent to the lab
- post is tried in and cemented
- cast post is used as build up as well
with a tapered post how do you keep it from being able to rotate?
- small grooves in canal can allow cement to fill those spaces decreasing rotation
- use multiple posts
- a cast post that includes a slight fill in a neighboring canal
why is is hard to be able to remove post cement and retreat
often canals are made too wide and too much tooth has been removed
how far should the post extend coronally
to the height of your build up so that the build up has full support of the post
why are posts difficult in the anterior
- challening occlusion
- little occlusal room
- significant vertical overlap
if the patient is a bruxer or grinder what post do you use and why
- a cast post becuase it will not break or separate
what are the metal posts and describe each
- cast metal: type 3 gold with gold and palladium
- stainless steel- very rigid, used most often
- titanium alloy- biocompatible but weaker
- brass- not used, corrosion occurs
what are the non metal posts and describe each
- fiber reinforced composite - glass/quartz
- ceramic (zirconia) post / composite core: difficult to remove, increased fracture potential
- possibel other ceramic post/core (milled or pressed in lab
describe fiber reinforced posts
- main advantage is better esthetics
- modulus of elasticity is similar to dentin
- must use RMGI (self adhesive)
- less root fx than metal posts
- post will usually break before root does
- failrues typically occur in teeth with little coronal tooth structure
give the pre fab post summary
- used by a majority of clinicians
- can be used in immediate or emergnecy situations
- either parallel or taper and round in cross section
- can be fiber reinforced or metal alloy
- usually stainless steel or titanium allow
do luting cements increase post retention
not significantly
what cement is better to use with posts and why
dual or self cure resin because improved retention
how is dentin pre treated prior to cementation and why
with etch and bond because it can give significant increase in strength of the bond
