Post and Core Classification Flashcards
What should be assessed prior to restoration of endodontically treated teeth?
Endo: Good apical seal, mechanical preparation of the canal, sensitivity to pressure, exudate, apical sensitivity, fistula, active inflammation, apical radiolucency.
Perio: Periodontal disease, presence of subgingival margins (crown lengthening)
Restorative: Restorability of the tooth (amount of sound tooth structure), possibility to create ferrule and supragingival margins (pericervical dentin)
When should a post be used?
Tooth with little tooth structure.
Assess factors like occlusal load, tooth position, type of opposing teeth, and function (FPD/RPD)
What are the types of posts based on surface characteristics?
Active: Treaded, engages the walls of the canal, more retentive, introduces more stress into the root, requires a substantial amount of root dentin.
Passive: Smooth and serrated, retained by luting agent, requires close adaptation to the canal wall, less stress into the root, less catastrophic failures, more commonly used.
What is the indication for active posts?
Short roots in which maximum retention is needed
What are the post classifications based on shape?
Parallel and tapered
What are the advantages of a parallel post?
Increased retention
Uniform stress distribution along the post length
Less root fracture
Stress concentration at the apex position
What are the advantages of a tapered post?
Follows the natural canal form and configuration preservation of tooth structure at the post apex.
Wedging effect - more stress.
Stress concentration at the coronal portion of the root
Lower retentive strength.
What are the classifications of post based on material?
Pre-fabricated: Metal, fiber, ceramic, zirconia
Cast: Semi-precious alloy, non-precious alloy, ceramic and zirconia
What are the ideal physiacl properties used for posts?
Similar to dentin with same modulus of elasticity and stiffness to avoid root fracture.
Can be bonded to tooth structure
Biocompatible
Absorber forces (Shock absorber)
How do metal and fiber posts differ in their physical effects?
Metal posts are rigid and fiber posts may have mechanical forces that more closely match the tooth.
What are the disadvantages of a fiber post?
Insufficient stiffness will allow excessive distortion of the core restoration at the margins during function. This would lead to breakdown of the cement and the risk of secondary caries.
Low elastic modulus of the post is found to increase stress formation in root and decreased fracture strength of restored tooth.
Failure of cementation (this is because adhesion is not reliable to dentin)
Low-modulus posts fail sooner or at lower stress than high-modulus posts
What is the post stiffness?
A function of post diameter + Elastic modulus of the post material
What are the advantages of a fiber post?
Common failures are due to loss of marginal seal of crown and post, loss of post retention, core fracture, and post fracture. This means that catastrophic failure is much less common.
Aesthetics are good with fiber post (tooth colour post can be used)
Treatment time is less compared to cast post and core.
Corrosion resistance
Biocompatibility
What are the disadvantages to using a metal post?
Higher incidence of root fractures (catastrophic failures)
Metal posts concentrate stress on the root due to higher elastic modulus
Aesthetics (poor aesthetics)
More clinical time and cost
What are the advantages of using a metal post?
Higher post stiffness, less post failure
Higher survival rate of metal post-supported restoration in clinical studies
Greater retention of stainless-steel post than carbon fiber post
