Restoration of Endodontically Treated Teeth Flashcards
What is the aim of endodontic treatment?
To treat or prevent apical periodontitis.
Restoration should preserve the decontaminated environment.
Finally: Treatment should eliminate infection and protect the decontaminated tooth from future microbial invasion.
What are the reasons for root canal treatment?
Inflammation: mechanical trauma, heat, chemical injury
Infection: Caries, deep cavities, exposure of dentine
What is the success rate of RCT?
Teeth with no preop periapical lesions = 96%
Teeth with pulp necrosis and periapical lesions = 86%
Teeth with periapical lesions undergoing retreatment = 62%
Why does having a precious periapical lesion reduce the success rate of endodontic treatment?
Some bacteria survive intracanal disinfections procedures
Or it could be due to coronal leakage due to secondary intraradicular infection.
How should endodontically treated teeth be evaluated prior to being restored?
Good apical seal
No sensitivity to pressure
No exudate
No fistula
No apical sensitivity
No active inflammation
True or False: Fractures are more common in endodontically treated teeth than teeth with vital pulps.
True
True or False: Dessication or dehydration of teeth after RCT leads to tooth fracture.
Early studies showed there is less moisture content in calcified tissue of pulpless teeth than in vital teeth. In more recent studies there is less dehydration of dentin.
Dehydrated dentin is not weaker than dentin with higher moisture.
Therefore RCT does not decrease hardness.
What is the effect of dessication on teeth?
Dehydration increases stiffness and decreases flexibility of dentin
Dehydration does not appear to weaken dentin structure in terms of strength and toughness
Both compression and tension showed no significant differences between RCT and vital teeth.
How do endodontically treated teeth differ from vital teeth?
No significant differences in punch shear strnegth, toughness, and load to fracture between groups.
Vital dentin was 3.5% harder
Similar biomechanical properties
Are endodontically treated teeth more brittle following endodontic treatment?
No, other factors are more critical to failure.
What happens to tooth structure after RCT?
Aging -> Calcification of peritubular dentin -> Mechanical properties of fracture resistance
Irrigants such as NaOCl and EDTA in high concentrations for prolonged times cause reduced flexural strength, elastic modulus and microhardness
Why are endodontically treated teeth more susceptible to fracture?
In most endo treated teeth there are missing tooth structures caused by caries or existing restorations.
Endodontic access cavity and root canal preparation cause loss of lots of dentin (including anatomical structures: cuspal ridges, roof of pulp chamber, marginal ridges -> Increased risk of tooth fracture)
Lack of protective feedback mechanism in endo treated teeth leading to more occlusal overloading and this leads to more tooth fracture.
Do endodontically treated teeth need crowns?
Coronal coverage restoration (onlays, partial or complete metal crowns, and metal ceramic crowns)
Non-coronal coverage restorations (amalgams and composite fillings, pin coronal buildups
In anterior teeth coronal coverage wasn’t significant but in posterior teeth it did significantly improve clinical success. So use a restoration that provides coronal seal.
What is the effect of losing the marginal ridge in endodontically treated teeth?
Loss of marginal ridge decreases more than 60% of tooth stiffness
When is a post needed?
To provide retention for the core that replaces lost coronal tooth structure and to retain the definitive prostheses.
They are not needed if there is substantial tooth structure after teeth have been prepared.
A post and core may help prevent coronal fractures when the remaining coronal tooth structure is very thin after tooth preparation.
What are the most common applications of posts?
Post + direct restoration: Post is separate from the restoration. If there is leakage bacteria have direct access to the RCS.
Post + core for crown preparation (separate): Crown may leak but bacteria won’t have direct access to the RCS.
Cast post and core in one piece. Give strength and rigidity and are often made of metal alloys such as gold. Work when there is substantial tooth structure left.
Why arne’t one-piece post crowns used very often anymore?
Hard to get a perfect fit with them.
What are overdentures?
Posts are put into the teeth to create an attachment site for dentures called overdentures.
What are overdentures?
Posts are put into root stumps to create an attachment site for dentures called overdentures.
What are the types of post?
Pre-fabricated: Cemented inside the canal and then composite/amalgam are used to build the core.
Cast post and core: Only indicated if there is a ferrule
How is ferrule provided for a tooth?
Parallel walls of dentin extending coronally from the crown margin provide ferrule.
What is the benefit of having a ferrule?
Increases resistance and decreases stress within the tooth (tooth protection)
True or False: Ferrule is the dentine present above the CEJ line.
False; The ferrule is the tooth structure that is supporting the crown.
What is the amount of tooth structure needed for a ferrule?
Minimum amount of ferrule = 1.5 - 2mm
Determined by amount of sound tooth structure above the gingival margin.
What is the are the features of the height needed for a ferrule?
Minimum amount of ferrule = 1.5 - 2mm
Determined by amount of sound tooth structure above the gingival margin.
At least 4 - 5mm of tooth structure coronal to the bone crest. (2 - 3 mm of biological width)
The greater the height of remaining tooth structure above the margin of the preparation the better the fracture resistance provided.
What is the are the features of the width needed for a ferrule?
Minimal thickness of remaining dentine of 1 - 2mm
Axial reuction of the crown preparation and the width of the post preparation will determine the ferrule width
What is the ideal location of a ferrule?
Circumferential ferrule is the ideal
What can cause a circumferential ferrule to not be possible?
May not be possible due to caries, erosion and abrasion and overreduction during tooth preparation
TRUE OR FALSE: A complete lack of ferrule is better than an incomplete ferrule.
False; An incomplete ferrule is a better option than a complete lack of ferrule
What does the ferrule do for the tooth?
Providing an adequate ferrule lowers the impact of the post and core system, luting agents and the final restoration on tooth performance.
What should you do if there is no tooth structure to create a ferrule?
Check restorability of a tooth.
Crown lengthening - surgical procedure
Orthodontic extrusion
When should crown lengthening be used vs ortho extrusion?
Both reduce root length
Surgical crown lengthening reduces root length and increases crown length
Time and cost may limit orthodontic extrusion
How are posterior and anterior teeth different and how does that affect the ferrule?
Posterior teeth take more vertical forces and anterior teeth take more oblique forces making anterior teeth need even more ferrule than posterior teeth.
Which factors can increase the risk of fracture of anterior teeth?
Deep bite
Parafunction
Dietary habits
Which factors can increase the risk of fracture of posterior teeth?
Group function
High cusps
What factor is most important for survival of structurally compromised endodontic teeth?
Non-desirable forces introduced by the restoration (interferences, inadequate occlusal design, etc) is probably more important for survival of structurally compromised endodontic teeth than is the post and core system
Which post and core system is recommended?
No universal recommendation have been established BUT literature seems to favor bonded fiber reinforced post (pre-fabricated) As opposed to metal post.
Main reason is related to catastrophic failures (more favourable failure pattern, less root fracture, and tooth fracture more occlusally)
What are the advantages and disadvantages of an amalgam core?
Advantage: Good for posterior teeth due to high compression strength
Disadvantage: Does not bond to tooth structure. Require retentive features that may weaken remaining walls.
What are the advantages and disadvantages of composite cores?
Adv: Bond to tooth structure (less reliable ith dentin though), requires extensive retentive features (undercuts) that my weaken the remaining walls.
Disadv: Weak composite/tooth interface may compromise the final restoration.
What is the technique used to add retention for an amalgam using the roots?
Remove GP from the pulp chamber up to 2 - 4mm from canal
Leave undercuts and divergence of canals
Remove unsupported tooth structures
Place matrix band
Condense the amalgam into the cavity starting from the root canal.
Restore tooth anatomy
Next session = crown prep
