Special features of endodontically treated teeth
Alteration level | Specific changes | Possible clinical implication |
Composition |
No decrease in compressive and tensile strength associated with this change in water content
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Dentin structure |
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Tooth macrostructure |
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Esthetic changes |
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Pretreatment evaluation
Endodontic evaluation |
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Periodontal evaluation |
Critical for treatment success
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Biomechanical evaluation |
Important clinical factors
Clinical complications for teeth with minimal remaining tooth structures
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Tooth position, occlusal forces, parafunctions |
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Esthetic evaluation and requirements |
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Restorations of endodontically treated tooth are designed to
- Protect the remaining tooth from fracture
- Prevent reinfection of the root canal system
- Replace the missing tooth structure
Considerations for endodontically treated anterior teeth
- Do not always need a complete crown, except when the size of plastic restorative materials limits their prognosis (e.g., if the tooth has large proximal composite restorations and unsupported labial tooth structure)
- Moisture content may be reduced but similar resistant to fracture compared to untreated teeth
- Discoloration without significant tooth loss may be more effectively treated by bleaching than by the placement of a complete crown, although not all stained teeth can be bleached successfully. Resorption can be an unfortunate side effect of nonvital bleaching
- When extensive loss of coronal tooth structure or the tooth will be serving as an abutment for an FDP or for a partial removable dental prosthesis, a complete crown is mandatory
Considerations for endodontically treated posterior teeth
- Subject to greater loading than are anterior teeth because they are closer to the transverse horizontal axis + morphologic characteristics (having cusps that can be wedged apart) makes them more susceptible to fracture
- Careful occlusal reshaping reduces potentially damaging lateral forces during excursive movements
- Endodontically treated posterior teeth should receive cuspal coverage to prevent biting forces from causing fracture except mandibular premolars and first molars with intact marginal ridges and conservative access cavities not subjected to excessive occlusal forces (i.e., posterior disclusion in conjunction with normal muscle activity)
- Complete coverage is recommended on teeth with a high risk of fracture especially maxillary premolars, which have been shown to have fairly high failure rates if two or three surfaces are restored with amalgam
- When significant coronal tooth loss has occurred, a cast post and core restoration or an amalgam foundation restoration is needed
Requirements of successful crown restoration
- Ferrule (dentin axial wall height) must be at least 2 to 3mm
- Axial walls must be parallel
- Restoration must completely encircle the tooth
- Margin must be on solid tooth structure
- Crown and crown preparation must not invade the attachment apparatus
Clinical features should be provided by posts
- Maximal protection of the root from fracture
- Maximal retention within the root and retrievability
- Maximal retention of the core and crown
- Maximal protection of the crown margin seal from coronal leakage
- Pleasing esthetics, when indicated
- High radiographic visibility
- Biocompatibility
Mechanical features of endodontic post
- Should not break
- Should not break the root
- Should not distort or allow movement of core and crown
- Optimal combination of resilience, stiffness, flexibility and strength
Resilience : ability to deflect elastically under force without permanent damage
Stiffness : ability to resist deformation when stressed
- Resilient enough to cushion an impact by stretching elastically, thereby reducing the resulting stress to the root
- Stiff enough not to distort, permanently bend, or structurally fail under mastication forces
Features of successful post and core design
- Adequate apical seal
- Minimum canal enlargement
- Adequate post length
- Positive horizontal stop to minimize wedging
- Vertical wall to prevent rotation
- Extension of final restoration margin onto sound tooth structure
Disadvantages to the routine use of a cemented post
- Placing the post requires an additional operative procedure
- Preparing a tooth to accommodate the post entails removal of additional tooth structure
- It may be difficult to restore the tooth later, when a complete crown is needed, because the cemented post may have failed to provide adequate retention for the core material
- The post can complicate or preclude future endodontic re-treatment that may be necessary
For these reasons, a metal post is not recommended in anterior teeth that do not require complete crowns
Restorative materials and options
Direct composite restorations |
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Indirect restorations : composite or ceramic onlays and overlays |
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Full crowns |
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Principles of tooth preparation of post
Conservation of tooth structure |
Preparation of the canal
Preparation of coronal tissue
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Retention form |
Anterior teeth
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Preparation geometry |
Threaded post is not recommended because of residual stress in the dentin
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Post length |
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Post diameter |
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Post surface texture |
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Luting agent |
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Posterior teeth
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Resistance form |
Stress distribution |
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Rotational resistance |
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Types of posts
Prefabricated metallic posts |
Active posts
Passive
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Fiber posts |
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Zirconia posts |
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Type of core materials
Luting cements
Traditional cements |
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Glass ionomer luting cements |
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Resin-based luting cements |
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Self-adhesive cements |
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Three stage operation
- Removal of the root canal filling material to the appropriate depth
- Enlargement of the canal
- Preparation of the coronal tooth structure
Removal of the endodontic filling material |
2 methods to remove gutta-percha
Warm plugger method
Gates Glidden drill, Peeso Reamer drill
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Post system selection |
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Canal enlargement |
Prefabricated posts
Custom-made posts
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Preparation of coronal tooth structure |
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