Post and Core: Latest Advancements (25 Marks)

Introduction

Objectives and Requirements (brief recap for completeness)

• Retain the core/crown, not the root itself
• Preserve maximum sound dentin (minimally invasive preparation)
• Distribute functional stresses evenly to avoid root fracture
• Provide a ferrule of 1.5-2 mm circumferential tooth structure wherever possible
• Modulus of elasticity ideally close to dentin to reduce catastrophic (non-repairable) fracture

Traditional Classification (baseline)

1. Cast post and core - custom, gold/Ni-Cr/Co-Cr alloys, single or multiple-rooted
2. Prefabricated posts - metallic (stainless steel, titanium) or non-metallic (zirconia, fiber)
3. By shape - parallel, tapered, parallel-tapered; by surface - smooth, serrated, threaded
4. By retention - active vs passive

Latest Advancements

1. Shift from rigid metal to Fiber-Reinforced Composite (FRC) posts

• Biomimetic rationale: modulus of elasticity close to dentin, so occlusal stress is transmitted more physiologically to the root and periodontium, reducing catastrophic root fracture. Failures with FRC posts tend to be de-bonding or post fracture (repairable) rather than vertical root fracture, unlike rigid metal/ceramic posts.
• Evidence: Network meta-analyses and systematic reviews (Martins et al. 2021; Tsintsadze et al. 2022; Giok et al. 2023) show fiber posts generally have comparable or superior survival to cast metal posts, especially in teeth without adequate ferrule, though results vary with ferrule presence.
• Short-fiber reinforced composite (SFRC) resins (e.g., everX-type materials) are now being used as a post-and-core-in-one material - injected/packed directly into the canal and core in a single visit, improving fracture resistance over particulate-filled composites.

2. CAD/CAM Post and Core Systems (major current focus)

• Digital workflow: intraoral/root canal scanning (direct scan or scan of an impression/silicone key of the prepared canal) → CAD design of an anatomically customized post-core → milling from a fiber-reinforced composite, resin-ceramic hybrid, or zirconia block, or additive 3D printing.
• Materials used:
  • Milled zirconia posts/cores - excellent esthetics and strength but high stiffness (stress concentration risk) and difficulty retrieving a fractured post if retreatment is needed.
  • CAD/CAM glass/fiber-reinforced composite blocks - combine the precision of digital fabrication with the favorable biomechanics of fiber posts; better marginal adaptation and reduced cement thickness than hand-adapted prefabricated fiber posts.
  • Resin-based hybrid CAD/CAM blocks - modulus close to dentin, no sintering shrinkage, faster and cheaper to mill, and more easily repairable/retrievable than zirconia.
• Advantages over conventional custom cast posts: no wax pattern/casting shrinkage, single-visit chairside possibility, better canal adaptation (thinner, more uniform cement layer improves bond strength and reduces microleakage), and improved esthetics under all-ceramic crowns (Vogler et al., 2023, describe a fully digital chairside fiber-CAD/CAM post-core workflow proposed as a new "gold standard" for severely destroyed anterior teeth).
• Ongoing challenge: standardizing scanning of the root canal (direct optical scanning limited by depth/moisture; indirect methods via silicone keys still commonly used).

3. 3D Printing / Additive Manufacturing

4. Advances in Adhesive Luting

• Self-adhesive resin cements and universal adhesives with silane/MDP-based primers for fiber-post surface treatment (silanization, sandblasting, or additional silica coating) to improve resin-to-fiber bonding.
• Surface treatments of fiber posts (hydrofluoric acid etching, airborne-particle abrasion, laser etching, plasma treatment) are being studied to improve the post-cement-dentin adhesive interface, since bond failure/decementation is now the leading mode of failure with fiber systems.

5. Reappraisal of the Ferrule and "Is a Post Even Necessary?"

• Al-Dabbagh et al. (2024) confirm a circumferential ferrule significantly improves survival of teeth restored with fiber posts, reinforcing that post design cannot compensate for absent ferrule.
• Jardim et al. (2025) and Alenezi et al. (2024) systematic reviews examine whether a post is essential at all when adequate coronal tooth structure/ferrule remains, concluding that posts mainly serve to retain a core in structurally compromised teeth rather than reinforcing the root - influencing a more conservative, case-selective approach to post placement.

6. One-Stage (Post + Core Build-up in One Material) Systems

7. Esthetic/Zirconia-Alternative Trends

Summary Table

Conclusion