ON FINAL: Restoration of Endodontically Treated Teeth: Posts and Cores Flashcards
The teeth become ________ and more susceptible to decay, fracture, and breakdown
softer
How do you decide what restoration to put on an endodontically treated tooth?
- Must have a ”global” perspective on your patient
- Evaluate the existing root canal
- Evaluate if the tooth is restorable
- 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? (post, core, crown lengthening, ortho)
What do you need to look for when evaluating the adequacy of the root canal?
- Is the tooth asymptomatic?
- Are the canals well filled?
- Does the apex appear sealed?
- Is there any suspicion of apical pathology?
- Is there a temporary restoration present?
- Is any restoration present sealed protecting the RCT from the oral environment?
- How long has the present restoration been
present? - Long standing temporary or lack of proper seal from restoration?
- Deep caries present
What do you need to think about when treatment planning a crown for an endo tooth?
- Is the tooth to be restored in a useful function in the patient’s occlusion?
- What is the prognosis of the restoration you want to place on the RCT treated tooth?
- Is the patient a bruxer? Grinder?
- Is the patient home care adequate?
Why do we need to examine RCT teeth more carefully and consider crowning RCT teeth quickly?
- Once pulp has been removed, and nerve sensation 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).
What is a favorable tooth fracture?
- Fracture in enamel only (crack line) or fracture in enamel and dentin
- The fracture line does not extend apical to the cemento-enamel junction
- There is no associated periodontal probing defect
- The pulp may be vital requiring only a crown
- If pulp has irreversible pulpitis or necrosis, root canal treatment is indicated before the crown is placed
What is a questionable tooth fracture?
- Fracture in enamel and dentin
- The fracture line may extend apical to the cemento-enamel junction but there is no associated periodontal probing defect
- There is an osseous lesion of endodontic origin
What is an unfavorable tooth fracture?
- Fracture line extends apical to the cementoenamel junction extending onto the root with an associated probing defect
Posterior tooth fractures occur because:
- Greater occlusal forces
- Divided occlusal surface (Cusps and Fossa)
- Fillings weaken tooth ability to hold together
In posterior teeth occlusal forces more inline with vertical axis of tooth. Therefore, __________
fractures more likely
vertical
Crowns did or did not significantly improve the success rates of endodontically treated ANTERIOR teeth when ample tooth structure remains?
DID NOT
Crowns significantly improved success rates of endodontically treated ____________ teeth
POSTERIOR
Crowns should be placed on RCT Treated POSTERIOR teeth…
as soon as possible with few exceptions
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
A crown needs at least ___mm for a ferrule.
2
What are the advantages and disadvantages of amalgam as a core material?
- Disadvantage – not retentive, does not bond, more tooth reduction needed
- Advantage – strength
What are the advantages and disadvantages of composite as a core material?
- Disavantage – not as strong
- Advantage – usability, bonding, more conservative tooth reduction
If tooth structure is missing, and restorability is compromised but not condemned, a _____ can be used to add strength to the core build up as you restore the lost tooth structure
post
Does a post increase the strength of a tooth?
NO
- adds support
Why 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
When do you not use a post?
Preparation of a post space adds risk to the restorative prognosis
- Higher likelihood of fracture or perforation
- Narrow roots
- Curved roots
The purpose of a post is to…
retain the core in a tooth when there is extensive loss of coronal tooth structure
If an anterior tooth has darkened due to RCT what can you do?
- you can try internal bleaching
- possible veneer or composite
What is the process for internal bleaching?
- 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 on an anterior tooth?
When more than 50% of coronal tooth structure has been lost
What does the post do for an anterior tooth?
The post and core is meant to resist lateral forces which would cause the crown to dislodge.
How do you decide when to place a post/core/crown versus extraction and implant?
- Remaining tooth structure
- Patient occlusion
- Patient habits
- Ferrule availability
- Crown lengthening may be needed
- Patient desires for esthetics
- Patient details (age, meds, etc.)
What is the ferrule?
from the finish line up to the coronal part of the crown
- A ferrule is the vertical axial wall that encircles the tooth which a crown will use to resist fracture
Minimum ferrule = ___mm beyond the core
2
Without the proper ferrule, what happens to anterior teeth?
root fracture is much more likely on anterior teeth due to high lateral forces in mastication
When remaining tooth structure has large access and a shorter clinical crown, generally a post is or is not necessary?
Is NOT
True/false
In posterior teeth most instances a build up is adequate to aid in crown retention as opposed to a post
True
Where do you put posts in posterior teeth?
Use the longest and straightest root and canal
- Palatal root of Maxillary molars
- Distal root of Mandibular molars
What roots in posterior teeth should you avoid when placing a post?
AVOID – Buccal roots of Maxillary molars
AVOID – Mesial roots of Mandibular molars
Where do you place posts in premolars?
- Significant variation in root length, curvature, bifurcation, and width
- Use a post only in roots that have ample bulk and a straight root anatomy
Use a post on a premolar if…
- Substantial tooth structure is missing (eg –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 a good premolar to put a post in?
Mandibular 1st premolar
- The occlusion on Mandibular first premolars is usually favorable.
It may be possible to avoid both a crown and
post on which tooth after RCT with a conservative access fill?
mandibular 1st premolar
As a general rule, it is preferred to or not place a post unless needed to retain the build up
materia
to NOT
With extensive coronal destruction in ____________ generally requires a post as tooth is much smaller in relation.
premolars
Molars often only need a _________ and then secondary retentive features such as grooves, boxes, pins, bonding, or utilizing the access hole.
build up
Likely the most important factor in clinical success…
- Leave as much tooth structure a possible.
- The more you take away, the more you have to add, the more you weaken the tooth and restoration.
- Sometimes, you have to leave the tooth “ugly” as this improves retention and strength!
What allows for retention?
ability of the post to resist vertical dislodging forces
-Post length and taper
-Active or Passive
-Cement used
What allows for resistance?
ability of the post and core to withstand lateral or rotational forces
-Amount of remaining tooth structure
-Post length and rigidity
-Anti-rotation features
-Presence of a Ferrule
How long should a post be?
- ½ to 2/3 the length of the root is ideal
- Minimum length at least that of the clinical crown
- 4-5mm of Gutta Percha left to keep the seal of the Gutta Percha
A post too _____ allows the forces to act with greater stress leading to a higher incidence of root fracture
short
A post that does not leave _____ mm at the apical for the RCT seal will compromise the tooth
4-5
The post often is too big at the ____ and can cause root fracture
apex
As a general rule, molar post spaces greater than ___ mm apical to canal orifice increases the potential for root perforation
7
Post preparation diameter should not exceed ____ of the root at the CEJ
1/3
Leave at least ___ mm of sound dentin at mid-root
1
Ideal diameter of post should only be _______ mm depending on the particulars of the
tooth
0.6 - 1.2
Retain ___ mm of Gutta Percha at the apical aspect of root
4-5
- (Unless curvatures dictate otherwise)
- Often this is not possible on molars due to root anatomy
How do you remove gutta percha to create a post space?
- Rubber Dam isolation mandatory
- Can soften/melt the Gutta Percha to then be able to remove it. (Heat Method)
- Mechanical Method - Canal is instrumented with Gates Glidden and/or Peazo Reamer rotary instrument.
When can gutta percha be removed?
Years after RCT placed or immediately after obturation.
Why do you need to be careful when using heat to remove gutta percha?
Heated instruments are used with caution. They can overheat the tooth and cause soft tissue burns if not careful.
What helps to decrease perforations during the mechanical method of removing gutta percha?
There is a safety tip on the Gates Glidden and the Peaso to help decrese perforations
What type of speed is used to remove gutta percha?
- A slow speed handpiece is used.
- Gates used at 800RPM with Electric handpiece Peaso used at 1200RPM with Electric handpiece
How do you mechanically remove gutta percha?
- Follow the pink GP with gentle
vertical movements. - Press in gently. Pull back. Repeat
- You may need to start with a small drill and step up to a larger one depending on the size of the canal.
- Watch your angulation!!!
What is an active versus a passive post?
- Active posts (smooth) engage the surrounding root material usually via threads or a serrated edge
- Passive posts fit into the canal without engaging the surrounding root material
Is threaded, smooth, or serrated post more retentive (all parallel)?
threaded
serrated is second
What kind of stress do serrated parallel posts have?
High stress at apex and therefore higher incidence of root fracture
What kind of stress do threaded parallel posts have?
Create higher stress on the root and therefore have a higher incidence of root fracture
What types of posts are most retentive and which are least retentive when considering…
Parallel Post vs Tapered Post
Active (threaded/serrated) Post vs Passive (smooth) Post
Most retentive
-Threaded Parallel Post
-Serrated Parallel Post
-Threaded Tapered Post
-Serrated Tapered Post
-Parallel Passive Post
-Tapered Passive Post
Least retentive
________ posts are often screwed into the teeth with a handpiece or special tool to engage the surrounding root surface
Active
Passive Posts gain their retention and support through ___________
cementation
What is a custom passive post?
-Resin pattern sent to lab to be cast in metal alloy
What is a pre-fabricated post?
Cemented in root with core build up of composite or amalgam
What are the advantages of a custom cast post?
- Anti-Rotational properties
- Core is part of post
- Can be preservative of tooth structure as the post fits the space
What are the disadvantages of a custom cast post?
- 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 of a pre-fabricated post?
- Increased retention within root
- Ease of placement
- More versatile to a wider range of tooth root shapes
- Post will often break before root will
What are the disadvantages of a pre-fabricated post?
- Post space needs to be slightly larger than cast
- Core retention to post can be a problem
- Possible rotation
- Metal posts still have un-esthetic color
Why do you need to be cautious with pre-fabricated posts?
Parallel posts have difficulties at times with narrowing of tooth root and can lead to root tip fracture
What is the issue with a post in a premolar with an ovoid shaped canal?
A pre-fab post is not stable on its own as the canal shape allows the post to rock back and forth
How do you fix the problem of an unstable post in a premolar?
- A cast post can be made
- A Pre-Fab post can 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.
- This reduces the stress on the major post which would have been supported only by cement.
- Then the two posts are cemented in the canal together and core build up placed.
- Primarily for Anterior and select premolars
What is 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 wel
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
- Using multiple posts
- A Cast post that includes a slight fill in a
neighboring canal
The post should extend to the height of your…
build up so that the build up has the full support of the post
Why is a post challenging in the anterior?
- Challenging occlusion in the anterior
- Little occlusal room in the anterior
- Significant vertical overlap in the anterior
- Bruxer/Grinder?
If a post is challenging in the anterior what type of post should you use?
Cast post
What are metal posts made of?
- 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 non-metal posts made of?
- Fiber-Reinforced composite (glass/quartz)
- Ceramic (zirconia) post / composite core
— Difficult to remove
— increased fracture potential - Possible other ceramic post/core (milled or pressed in lab). Not enough data to recommend
What the features of fiber reinforced posts?
- Main advantage is better esthetics
- Modulus of Elasticity is similar to dentin
- Must use Resin cement (self-adhesive)
- Less Root fractures than metal posts
— Post will usually break before root does - Failures typically occur in teeth with little coronal tooth structure
What are the main features of the pre-fab post summary?
- Used by a majority of clinicians
- Can be used in immediate or emergency situations
- Either parallel or taper and round in cross section
- Can be fiber reinforced or metal alloy
- Usually stainless steel or titanium allo
Luting cements do or do not increase post retention in a significant way?
DO NOT
What is better for cementation: luting cement or dual/self cure resin cement?
dual or self cure resin cement
A pre-treatment of the dentin prior to cementation through etch and bond can have significant increase in ________ of bond.
strength
