3. post retained crown-midterm3


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3. post retained crown-midterm3

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