Quartz 4

L6 Principles and Techniques Optech

10 min read

Restoration of Endodontically Treated Teeth1

Clinical Overview

This presentation focuses on the principles and techniques involved in the restoration of endodontically treated teeth, as presented by Dr. Marrwa Ibrahim at the Oral Health Centre of Western Australia.

Fracture Susceptibility of Endodontically Treated Teeth2

Are endodontically-treated teeth more susceptible to fracture, and if so, why?

Clinical Goals

Understanding fracture mechanisms is essential for planning restorations that reduce fracture risk, preserve dentin, create a ferrule effect, and achieve a reliable coronal seal.

Common Assumptions About Tooth Fracture3

Dehydration and Brittleness

  • Common Assumption: Dehydration of teeth after Root Canal Therapy (RCT) due to the removal of pulp tissue leads to tooth fracture because of an increase in brittleness
    • This concept implies that the dentin itself undergoes a material property change post-treatment, which is contradicted by scientific evidence..

True or False?

Scientific Evidence on Dentin Integrity4

Numerous studies have investigated the assumption that endodontically-treated teeth are more brittle:

  • Dehydration does not appear to weaken dentin structure in terms of strength and toughness.
  • Root canal therapy does not significantly affect the hardness of dentin, even five to ten years post-treatment.
  • The intrinsic material properties of dentin remain largely stable post-RCT; therefore, the cause of fracture is not primarily intrinsic brittleness.

Actual Causes of Tooth Weakening5

Factors Contributing to Structural Weakness

  • Pre-existing Damage: In most endodontically treated teeth, there are missing tooth structures caused by caries and/or existing restorations.
  • Procedural Loss: Endodontic access cavities and root canal preparations lead to further loss of tooth structure.
  • Critical Structure Loss: The loss of specific structures (mainly dentin)—such as cusp ridges, the roof of the pulp chamber, and marginal ridges—increases the risk of coronal or root fracture.
    • Loss of peri-cervical dentin is a critical factor in structural weakening.
    • Increased tooth flexure under occlusal load, caused by the loss of cusp support and marginal ridges, elevates the risk of coronal and root fractures.

Purpose of Post Placement6

Evolution of Post Placement Philosophy

  • Past Belief (False): Posts were thought to strengthen the weakened tooth.
  • Current Understanding: Posts are used to provide retention for the core that replaces lost coronal tooth structure and to retain the definitive prostheses.

Indications for Post Use7

Clinical Decision Making

  • Post Not Necessary: Teeth with significant remaining structure, such as posterior teeth with only a conservative elective endodontic access cavity.
  • Post Necessary: Teeth with little tooth structure remaining above the gingival margin.
  • Assessment Criteria for Intermediate Situations:
    • Occlusal load
    • Tooth position
    • Type of opposing tooth
    • Function (e.g., acting as an abutment for a Fixed Partial Denture [FPD] or Removable Partial Denture [RPD])

Common Applications of Posts8

  1. Post + Direct Restoration: Post used with separate amalgam or composite filling.
  2. Post + Core for Crown Preparation: Separate post and core (amalgam or composite) used to support a crown.
  3. Cast Post and Core: A one-piece unit made of metal alloys (such as gold) for a crown preparation.

Classification by Mode of Fabrication9

  • Cast Post and Core: The post and the core are cast as a single unit.
  • Pre-Fabricated Post: The post is cemented into the root canal, and the core is built up directly using composite or amalgam.

Classification by Surface Characteristics10

Active Posts

  • Characteristics: Threaded; engage the walls of the canal.
  • Pros/Cons: More retentive but introduce more stress into the root.
  • Requirements: Require a substantial amount of root dentin.
  • Indication: Short roots where maximum retention is needed (limited use).

Passive Posts

  • Characteristics: Smooth or serrated; retained strictly by the luting agent.
  • Pros/Cons: Require close adaptation to the canal wall; result in less stress and fewer catastrophic failures.
  • Usage: More commonly used.

Classification by Shape11

Parallel Walls

  • Benefits: Increased retention and uniform stress distribution along the post length.
  • Risks: Lower incidence of root fracture, though stress may concentrate at the apical portion.

Tapered

  • Benefits: Follows natural canal form, preserving tooth structure at the post apex.
  • Risks: Creates a wedging effect leading to more stress; stress concentration at the coronal portion of the root.
  • Retention: Lower retentive strength.

Classification by Material12

Pre-fabricated Post Materials

  • Metal: Stainless steel, titanium.
  • Fiber Reinforced: Carbon fiber, glass fiber, quartz fiber.
  • Ceramic: Zirconia.

Cast Post Materials

  • Alloys: Semi-precious (gold) or non-precious (base metal).
  • Ceramic: Zirconia.

Post Placement in Endodontically Treated Teeth13

  • Direct Technique: Pre-fabricated post combined with a direct core (composite or amalgam).
  • Indirect Technique: Utilizes an impression technique.
  • Direct-Indirect Technique: Burnout resin technique for a cast post and core.

Purpose of Post Placement

Historically, posts were believed to “strengthen” the tooth. This concept is incorrect. A post does not reinforce dentin; its modern indication is strictly functional: to provide retention for the core when there is insufficient coronal tooth structure.

Post Space Preparation14

Clinical Steps

  1. Determine post length based on Periapical (PA) radiograph.
  2. Apply Rubber Dam.
  3. Remove Gutta Percha (GP).
  4. Prepare post space.
  5. Prepare the coronal structure.

Determination of Post Length15

While there is no absolute guideline, post length should generally be:

  • Preserve the apical seal by leaving 4 to 5 mm of gutta-percha apically.

  • Respect root anatomy—thin, curved, or short roots impose physical limits on post dimensions.

  • At least equal to the crown length.

  • 2/3 of the remaining tooth length.

  • 1/2 of the clinical root.

  • 3/4 of the root canal length.

Rubber Dam Isolation16

Rationale for Isolation

  • Contamination Control: Avoid bacterial contamination from saliva or blood.
  • Safety: Prevent inhalation or ingestion of instruments (endo files, burs).
  • Chemical Protection: Avoid contact of sodium hypochlorite with the mucosa during canal cleaning.

Removal of Gutta Percha17

Procedure

  • Begin removal using a heated endodontic plugger.
  • Use a rubber stop to mark the Working Length (WL).
  • Use a Gates Glidden bur to reach the designated WL.

Preparation of Post Space18

Preparation Steps

  • Use ParaPost drills (ParaPost System).
  • Create parallel walls and remove internal undercuts.

Standard Post Widths (Diameters)

  • 1.50 mm (Ø0.060”)
  • 1.40 mm (Ø0.055”)
  • 1.25 mm (Ø0.050”)
  • 1.14 mm (Ø0.045”)
  • 1.00 mm (Ø0.040”)
  • 0.90 mm (Ø0.036”)

Post Width Considerations19

  • Retention vs. Strength: Increasing post width increases retention and resistance, but wide posts weaken the root due to excessive tooth structure removal.
  • 1/3 Rule: The post width should be no more than 1/3 of the total width of the root.
  • Prefer a longer post rather than a wider post, provided apical seal and root anatomy permit.
  • Prioritize dentin preservation first, especially peri-cervical dentin, which is fundamental for resisting bending and shear forces.

ParaPost System Overview20

The ParaPost® System by COLTENE offers a complete range of posts for both direct and indirect indications.

Clinical Goals

Regardless of the system used, the primary goals are to preserve dentin, achieve a passive fit, and create a retentive core with a reliable coronal seal.

ParaPost Fiber Posts21

Taper Lux®

  • Design: Cylindo-conical (4° taper) for narrow canals.
  • Features: Translucent for light-cured cementation; three-head design for length adjustment; rounded undercut head for core retention.
  • Sizes: Four options.

Fiber Lux®

  • Design: Cylindrical; ideal for universal applications.
  • Features: Translucent; rounded undercut double head; length adjustment possible at both head and apical ends.
  • Sizes: Six options.

Fiber White®

  • Design: Cylindrical; ideal for universal applications.
  • Features: Opaque fiber resin to mask discolored roots; rounded undercut double head; length adjustment possible at both ends.
  • Sizes: Five options.

Material Properties

Fiber posts are preferred because their elastic modulus approximates that of dentin, which offers more favorable stress distribution and superior aesthetics under translucent restorations.

Diameter Specifications

Diameter (inches)Diameter (mm)
0.070”1.75 mm
0.060”1.50 mm
0.055”1.40 mm
0.050”1.25 mm
0.045”1.14 mm
0.040”1.00 mm
0.036”0.90 mm

Clinical Application of ParaPost Fiber Posts22

Step-by-Step Procedure

  1. Assessment: Preoperative clinical situation (e.g., right lateral incisor #12) after RCT with provisional sealing.
    • Evaluate restorability and ferrule potential before initiating treatment
  2. Access: Removal of provisional sealing.
  3. GP Removal: Removing Gutta Percha.
    • Maintain the apical seal while removing material to the planned depth
  4. Drilling: Extending the post preparation with a ParaPost bur.
  5. Trial: Trial seating of ParaPost Fiber White to check length and fit.
  6. Bonding: Applying One Coat 7 Universal for 20 seconds; removing excess with air and paper points.
  7. Build-up: Freehand core build-up using ParaCore automix.
  8. Finishing: Finished core ready for impression.
  9. Finalization: Cementation of the final crown.
  10. Verification: Confirm the result clinically and radiographically before proceeding to the definitive restoration.

ParaPost X-System Metal Posts23

XP™ Post

  • Design: Cylindrical with a flat head; ideal for slim or multi-rooted teeth.
  • Retention: X-Shape pattern with cement venting.
  • Material: Titanium alloy (Ti6Al4V) or stainless steel.
  • Sizes: Seven sizes; compatible with ParaPost Drills.

XH™ Head

  • Design: Cylindrical with rounded, undercut double head for core retention.
  • Safety: Flat shoulder stop prevents over-insertion and apical stress.
  • Retention: X-Shape pattern with cement venting.
  • Sizes: Seven sizes; compatible with ParaPost Drills.

XT™ Thread

  • Design: Threaded, cylindrical post for high mechanical grip.
  • Features: Low-profile threads cut dentin with minimal stress; threads located only in the coronal area where walls are thicker.
  • Safety: Flat shoulder stop and rounded undercut double head.
  • Sizes: Six sizes; compatible with ParaPost Drills.

Metal Post Risks

Metals exhibit significantly higher stiffness than dentin, which can concentrate stress and lead to unfavorable (non-restorable) root fractures.

Sizes and Specifications24

Available Sizes (Direct Technique)

  • 1.75 mm (0.070”)
  • 1.50 mm (0.060”)
  • 1.40 mm (0.055”)
  • 1.25 mm (0.050”)
  • 1.14 mm (0.045”)
  • 1.00 mm (0.040”)
  • 0.90 mm (0.035”)
  • Select the smallest post diameter that provides adequate retention to avoid compromising root strength
  • Avoid over-flaring the cervical region during preparation

Casting Technique with XP Burnout Post25

XP™ Impression Post

  • Description: Rigid polymer post for precise impressions.
  • Function: Captures the entire length of post space without undercuts.
  • Sizes: Seven sizes; compatible with ParaPost Drills.

XP™ Burnout Post

  • Description: Rigid polymer post for casting one-piece post/cores.
  • Features: X-shape retention pattern; stabilizes wax core build-up during removal.
  • Sizes: Seven sizes; compatible with ParaPost Drills.

XP™ Temporary Post

  • Description: Plain titanium post for temporary crown retention.
  • Features: Friction grip for snug placement (no temporary cement needed in canal); preserves canal diameter.
  • Sizes: Seven sizes; compatible with ParaPost Drills.

Size Reference

  • 1.75 mm (0.070”)
  • 1.50 mm (0.060”)
  • 1.40 mm (0.055”)
  • 1.25 mm (0.050”)
  • 1.14 mm (0.045”)
  • 1.00 mm (0.040”)
  • 0.90 mm (0.036”)

Footnotes

  1. Original PDF page 1: L4 RETT CSSL, p.1 ↩

  2. Original PDF page 2: L4 RETT CSSL, p.2 ↩

  3. Original PDF page 3: L4 RETT CSSL, p.3 ↩

  4. Original PDF page 4: L4 RETT CSSL, p.4 ↩

  5. Original PDF page 5: L4 RETT CSSL, p.5 ↩

  6. Original PDF page 6: L4 RETT CSSL, p.6 ↩

  7. Original PDF page 7: L4 RETT CSSL, p.7 ↩

  8. Original PDF page 8: L4 RETT CSSL, p.8 ↩

  9. Original PDF page 9: L4 RETT CSSL, p.9 ↩

  10. Original PDF page 10: L4 RETT CSSL, p.10 ↩

  11. Original PDF page 11: L4 RETT CSSL, p.11 ↩

  12. Original PDF page 12: L4 RETT CSSL, p.12 ↩

  13. Original PDF page 13: L4 RETT CSSL, p.13 ↩

  14. Original PDF page 14: L4 RETT CSSL, p.14 ↩

  15. Original PDF page 15: L4 RETT CSSL, p.15 ↩

  16. Original PDF page 16: L4 RETT CSSL, p.16 ↩

  17. Original PDF page 17: L4 RETT CSSL, p.17 ↩

  18. Original PDF page 18: L4 RETT CSSL, p.18 ↩

  19. Original PDF page 19: L4 RETT CSSL, p.19 ↩

  20. Original PDF page 20: L4 RETT CSSL, p.20 ↩

  21. Original PDF page 21: L4 RETT CSSL, p.21 ↩

  22. Original PDF page 22: L4 RETT CSSL, p.22 ↩

  23. Original PDF page 23: L4 RETT CSSL, p.23 ↩

  24. Original PDF page 24: L4 RETT CSSL, p.24 ↩

  25. Original PDF page 25: L4 RETT CSSL, p.25 ↩

Graph View

Backlinks