PROSTHO 1 (Lecture)

• Radicular crown


  Same as dowel crown
• Post


  There is a post inside the root canal
• Post-retained crown


  Artificial crown placed on a tooth that has undergone root canal treatment, non-vital tooth
• Indications for post-retained crown

  • Root canal treated tooth
  • Minimal tooth structure left externally and internally
• Not indicated for post-retained crown

  • Root is very curved
  • Sufficient tooth structure (rather simple jacket crown will do)
• Cemented customized dowel crown

  Non-vital tooth appears to be dark
• Factors that influence decision to restore tooth with dowel crown

  • Amount of coronal structure (external/internal)
  • Root morphology - no dowel post for excessively curved root
• Types of dowel


  • Attached - all components are fused together
  • Detached - dowel crown and all components are just cemented all together
• Types of dowel post according to fabrication

  • Custom post - fabricated by making a pattern first
  • Prefabricated post - readily available in the dental store
  • Combination custom and prefab post
• Treatment planning for endodontically treated teeth

  • Good apical seal from the root canal treatment
  • No sensitivity to pressure
  • No exudates like abscess
  • No fistula the drainage of exudate
  • No apical sensitivity
  • No active inflammation surrounding tissue of the tooth should be healthy
• Disadvantages to the routine use of cemented post

  • Placing the post requires an additional operative procedure
  • Preparing a tooth to accommodate the post removes additional tooth structure
  • It may be difficult to restore the tooth later when a complete crown is needed
  • The post can complicate or prevent future endodontic re-treatment if this becomes necessary
• The use of parallel-sided post in a tapered canal requires considerable enlargement of the post space, which can weaken the root significantly
• The dentin area may be thinned out which will indicate the tooth to fracture
• Parallel-sided posts


  • Great surface area, Retentive, but still choose post with the right fit to avoid fracture
• Requirements for traditional core and dowel construction

  • Ideally, the length of the post should be equal to or at least the length of the estimated clinical crown
  • The post must have an occlusal stop to prevent displacement apically
  • Included in this construction should be resistance to rotational forces
  • Post should be of sufficient thickness to resist displacement and assist in stabilization
• Proper measurement of post length

  From the margin, Canal filling (gutta percha), Gutta percha - apical seal (5mm), clinical crown and post length must be at least 5.5mm
• Extending a preparation apically creates a ferrule and helps prevents fracture of an endodonically treated tooth during function
• The rule of ferrule is to leave 2 mm ferrule
• Rotational resistance


  Can be obtained by preparing a small groove in the root canal (key way)
• Principles of post support (retention)

  • Minimum post length should equal restored crown length or engage a ⅔ of natural root
  • Cylindrical posts are more retentive than tapered posts
  • Wrought (bent/twisted/formed) gold alloy posts are two or four times stronger than cast gold alloy posts of equal diameter
  • Serrated posts are 30% to 40% more retentive than smooth posts
• 3 stages in tooth preparation

  • Removal of the root canal filling material to the appropriate depth
  • Enlargement of the canal 2-3 times bigger the original canal
  • Preparation of the coronal tooth structure
• 2 methods of removing gutta percha

  • With a warm condenser
  • With a rotary instrument (sometimes used with a chemical agent)
• Steps using warm condenser

  • Before removing gutta-percha, calculate the appropriate length of post
  • Avoid the apical 5 mm if possible
  • Apply a rubber dam before preparing the post-space
  • Select an endo condenser large enough to heat well but not so large that it binds against the canal wall
  • Mark it at the appropriate length, heat it and place it in the canal to soften the gutta percha
  • When the gutta percha has been removed to the appropriate depth, shape the canal as needed
• Enlargement of the canal for prefabricated posts


  • Enlarge the canal 1 or 2 sizes with a drill, endo file and reamer that matches the configuration of the post
  • Use a prefabricated post that matches standard endo instruments
  • Be especially careful not to remove more dentin at the apical extent of the post space than is necessary
• Enlargement of the canal for custom-made post

  • Use custom-made posts in canals that have a non-circular cross-section (elliptical) or extreme taper
  • Enlarging canals to conform to a preformed post may lead to perforation
  • Be most careful on molars to avoid root perforation
• 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 aesthetics
  • Remove all undercuts also internally that would prevent withdrawal of the pattern
  • Remove any unsupported tooth structure but be careful to preserve as much crown as possible
  • Be sure that part of the crown is prepared perpendicular to post
  • Complete the preparation by eliminating sharp angles and establishing smooth finish lines
• Advantages of prefabricated posts

  • 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, this is corrected by adding material when core is made
• Types of prefabricated posts

  • Parallel-sided posts - made of platinum-gold-palladium, nickel-chromium, or stainless steel
  • Serrated posts - come in stainless steel, titanium, or non-oxidizing noble alloy
  • Tapered posts - available in gold-platinum, nickel-chromium, and titanium alloy
• All prefabricated posts are biocompatible
• Custom-made posts


  • Can be cast from direct pattern or an indirect one
  • Direct technique utilizes autopolymerizing resin and is indicated for single canals
  • Indirect technique is more appropriate for multiple canals
• Core


  Replaces missing coronal tooth structure, and thereby, forms the shape of the tooth preparation
• Core fabrication


  • Can be shaped in resin or wax and added to the post pattern before the assemble is cast into metal
  • Can be cast onto most prefabricated post systems
  • Can be made from a restorative material such as amalgam, GI or composite resin
• Location of dowel post for posterior teeth

  • Max premolars with 2 canals - utilize the palatal/lingual canal
  • Max molars - utilize palatal/lingual canal
  • Mandibular molars - utilize distal canal
• Techniques in the removal of fractured posts

  • Post removal by high speed bur - for short post fractures
  • Masseran technique - uses special hollow end-cutting tubes or trephines to prepare a thin trench around the post
• Advantages and disadvantages of post and core systems


  • Amalgam - Conservative of tooth structure, straightforward technique, low tensile strength, corrosion
  • GI - Same as amalgam, difficult condensation, low strength
  • Composite Resin - Same as amalgam, low strength, continued polymerization, microleakage
  • Custom cast Post & Core - High strength, better fit than wrought, less stiff, time-consuming, complex procedure
  • Wire post & Cast core - High strength, high stiffness, corrosion of base metal, expensive
  • Tapered prefabricated post - Conservative of tooth structure, high strength & stiffness, less retentive
  • Parallel-sided prefabricated post - High strength, good retention, comprehensive system, expensive
  • Threaded post - High retention, stresses generated may lead to fracture, not conservative
  • Carbon fiber post - Easy removal, low strength, microleakage, black color
  • Zirconia ceramic post - Esthetics, high stiffness, uncertain clinical performance
  • Woven fiber post - Esthetics, dentin bonding, more flexible, low strength, uncertain clinical performance
• Recommended use and precautions for post and core systems

  • Amalgam - Molars with adequate coronal tooth structure, not recommended in teeth under lateral load
  • GI - Teeth with minimum tooth structure missing, not recommended in teeth under lateral load
  • Composite - Teeth with minimum tooth structure missing, not recommended in teeth under lateral load
  • Custom cast Post & Core - Elliptical or flared canal, care to remove nodules before try in
• Cementation of post and core

  1. A rotary (lentulo) paste filler or cement tube is used to fill the canal with cement

  2. The post is first coated with cement

  3. Fill also the canal with cement

  4. The post and core is inserted gently to reduce hydrostatic pressure

  5. Remove any excess cements

  6. It is recommended that a groove be placed along the side of the post to allow excess cement to escape
• Fixed Partial Denture (Bridges)


  Dental prosthetic that replaces one or more missing teeth, with the replacement teeth attached to adjacent natural teeth
• Edentulous space


  • Space between abutments where teeth are missing
• Treatment options for edentulous space

  • FPD (Fixed Partial Denture)
  • RPD (Removable Partial Denture)
  • Implant
  • No treatment (if space is too small)