3. post retained crown-midterm3

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  • 1. POST-RETAINED CROWN (Restoration of the Endodontically Treated Tooth )
  • 2. Cemented Dowel Crown
  • 3.
    • Cemented dowel crown
    • (radiographic view)
  • 4. Treatment Planning
    • Endodontically treated tooth need to be assessed carefully for the following:
    • 1.      Good apical seal
    • 2.      No sensitivity to pressure
    • 3.      No exudates
    • 4.      No fistula
    • 5.      No apical sensitivity
    • 6. No active inflammation
  • 5. Disadvantages to the routine use of a cemented post:
    • Placing the post require an additional operative procedure
    • Preparing a tooth to accommodate the post removes additional tooth structure
  • 6.
    • The use of a parallel-sided post in a tapered canal requires considerable enlargement of the post space, which can weaken the root significantly.
  • 7.
    • c.  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.
    • d. The post can complicate or prevent future endodontic retreatment if this becomes necessary.
  • 8. Requirements for traditional core and dowel construction:
    • a. Ideally the length of post should be equal to, at least, the length of the estimated clinical crown.
    • b. The post must have an occlusal stop to prevent displacement apically. This is of vital importance since displacement toward the apex commonly results in fracture of the prepared root.
  • 9.
    • c. Included in this construction should be resistance to rotational forces.
    • d. Posts should be of sufficient thickness to resist displacement and assist stabilization.
  • 10. Clinical crown Apical seal
  • 11.  
  • 12.  
  • 13.
    • PREPARED TOOTH
    • for
    • DOWEL CROWN
    ferrule
  • 14.  
  • 15.  
  • 16. Principle of Post Support (Retention)
    • A. Minimum post length should equal restored crown length or engage 2/3 of natural root
    • B. Cylindrical posts are more retentive than similarly size tapered posts
    • C. Wrought (bent/twisted/formed) gold alloy posts are two to four times stronger than cast gold alloy posts of equal diameter
    • D. Serrated posts are 30% to 40% more retentive than are smooth posts
  • 17. 3 Stages in Tooth Preparation
    • 1.   Removal of the root canal filling material to the appropriate
    • depth
    • 2.   Enlargement of the canal
    • 3.   Preparation of the coronal tooth structure
  • 18. REMOVAL OF THE ENDO FILLING MATERIAL
    • 2 Methods of Removing Gutta Percha:
    • a. With a warmed condenser
    • b. With a rotary instrument (sometimes used with a chemical agent such as chloroform)
  • 19. Endo condenser / plugger
  • 20. Gutta condenser
  • 21. Steps: (using a warmed condenser)
    • 1. Before removing gutta percha, calculate the appropriate length of the post.
    • 2.  Avoid the apical 5mm if possible.
    •  
    5mm. Apical seal
  • 22.
    • 3.  To prevent aspiration of an endo. instrument, apply a rubber dam before preparing the post space.
    • 4. Select an endo. condenser large enough to hold heat well but not so large that it binds against the canal walls.
  • 23.
    • 5.  Mark it at the appropriate length, heat it, and place it in the canal to soften the gutta percha.
    • 6.   When the gutta percha has been removed to the appropriate depth, shape the canal as needed.
  • 24. ENLARGEMENT OF THE CANAL
    • For Prefabricated Posts
    • 1. Enlarge the canal one to two sizes with a drill, endo file and reamer that matches the configuration of the post
    • 2. Use a prefabricated post that matches standard endo instruments
    •  
    • 3. Be especially careful not to remove more dentin at the apical extent of the post space than is necessary
  • 25.
    • For Custom-made Posts
    • 1. Use custom-made posts in canals that have a non-circular cross section or extreme taper. Enlarging canals to conform to a preformed post may lead to perforation.
    •  
    • 2. Be most careful on molars to avoid root perforation.
  • 26. PREPARATION OF THE CORONAL TOOTH STRUCTURE
    • Ignore any missing tooth structure and prepare the remaining tooth as though it were undamaged. 
    • Be sure that the facial surface of the tooth is adequately reduced for good esthetics.
    • Remove all undercuts that would prevent withdrawal of the pattern
  • 27.
    • 4. Remove any unsupported tooth structure, but be careful to preserve as much of the crown as possible.
    • 5. Be sure that part of the crown is prepared perpendicular to the post.
    • 6. Complete the preparation by eliminating sharp angles and establishing a smooth finish line.
  • 28. Post Fabrication:
    • a.   Prefabricated Posts
    • - One advantage of using prefabricated posts is the simplicity of the technique
    • - A post is selected to match the dimensions of the canal, and only minimum adjustment is needed for seating it to the full depth of the post space
    • - Coronal half of the post may have an inadequate fit because the root canal has been flared, this is corrected by adding material when the core is made
  • 29. PREFABRICATED POSTS
  • 30.
    • b.   Custom-made Posts
    • - Can be cast from direct pattern or an indirect one
    • - Direct technique utilizes autopolymerizing resin and is indicated for single canals whereas an indirect technique is more appropriate for multiple canals
  • 31. Core Fabrication :
    • The core replaces missing coronal tooth structure, and thereby forms the shape of the tooth preparation.
    • It can be shaped in resin or wax and added to the post pattern before the assembly is cast into metal.
    • The core can also be cast onto most prefabricated post systems.
    • A third alternative is to make the core from a restorative material such as amalgam, GI or composite resin.
    • A
  • 32. 1 2 3 4 Casted metal post and core Post & core pattern Core pattern using wax Casted post & core cemented into the tooth Wax pattern for multiple root tooth
  • 33. Wax pattern for a single root tooth A B C
  • 34. AVAILABLE POST AND CORE SYSTEMS
    • ADVANTAGES DISADVANTAGES
    • Amalgam Conservative of tooth Low tensile strength
    • structure Corrosion with base
    • Straightforward technique metal
    •  
    • GI same Difficult condensation
    • Low strength
    •  
    • Composite same Low strength
    • Resin Continued polymerization
    • Microleakage
    •  
    • Custom cast High strength Less stiff than
    • Post & Core Better fit than prefabricated wrought
    • Time-consuming
    • Complex procedure
    •  
  • 35.
    • ADVANTAGES DISADVANTAGES
    • Wire post & High strength Corrosion of base metal
    • Cast core High stiffness Pt-Au-Pd wire expensive
    •  
    • Tapered pre- Conservative of tooth Less retentive than || sided
    • fabricated structure or threaded system
    • post High strength & stiffness
    •  
    • || sided pre- High strength Precious-metal post fabricated post Good retention expensive
    • Comprehensive system Corrosion of SS Less conservative of tooth
    • structure
    • Threaded post High retention Stresses generated in the canal may lead to fracture
    • Not conservative of coronal and radicular tooth structure
  • 36.
    • RECOMMENDED USE PRECAUTION
    • Amalgam Molars with adequate coronal tooth Not recommended in structure teeth under lateral load (anteriors)
    •  
    • GI Teeth with minimum tooth Not recommended in structure missing teeth under lateral load
    • Composite same same
    •  
    • Custom cast Elliptical or flared canal Care to remove Post & Core nodules before try in
  • 37.
    • RECOMMENDED USE PRECAUTION
    • Wire post & Small circular canal Care to avoid
    • Cast core perforation during prep.
    •  
    •   Tapered pre- same Not recommended for fabricated post excessively
    • flared canals
    • || sided pre- same Care during prep.
    •   fabricated post
    • Threaded post Only when maximum Care to avoid retention is essential fracture during seating
  • 38.
    • Tapered threaded post
    • (jacket crown)
    Tapered smooth-sided post
  • 39.
    • Tapered threaded post
    • (fixed bridge)
  • 40. Some Techniques In the Removal of Fractured Post
  • 41. Post Removal by High Speed Bur
    • A post that has fractured within the root canal cannot be removed with a post puller or forceps. The post can be drilled out, but great care is needed to avoid deviation.
    • This technique is best limited to relatively short fractured posts.
  • 42. Post removal by high speed bur A B
  • 43. Masseran Technique
    • Uses special hollow end-cutting tubes or trephines to prepare a thin trench around the post.
    • Removal or retrieval can be facilitated by using an adhesive to attach a hollow tube extractor or by using a threaded extractor.
  • 44. Maxillary incisor with a fractured post inside the canal (A and B). A B
  • 45. C. The diameter of the post is gauged with a sizing tool. D. The selected trephine is carefully rotated counter- clockwise to create a narrow channel around the post. C D
  • 46. E. When the instrument has removed sufficient material, the post is recovered. F. The fractured crown and post after removal. F E Fractured post
  • 47. Cementation of Post and Core
  • 48. A rotary (lentulo) paste filler or cement tube is used to fill the canal with cement.
  • 49.
    • The post is first coated with cement.
  • 50.
    • It is important that the luting agent fill all dead spaces within the root canal system.
  • 51.
    • The post and core is inserted gently to reduce hydrostatic pressure, which could cause root fracture.
  • 52.
    • It is recommended that a groove be placed along the side of the post to allow excess cement to escape, if a parallel-sided post is being used.