Post Diameter The diameter of the post is dictated by the root canal anatomy. A minimal dentin thickness of 1 mm around the post should be provided. The width of the post should not be greater than one third of the width of the root at any point along the dowel. Smaller posts not only conserve tooth structure, but also provide increased resistance to fracture compared with larger posts.

(A) too narrow (B) optimum size post (C) too large

Post Design Posts can be serrated, smooth, roughened or threaded. Parallel, serrated posts are cemented into the canal passively. They are retentive and produce less stress in the root dentin than threaded systems

The Ferrule Effect The ferrule is the circumferential ring of sound tooth structure that is enveloped by the cervical portion of the crown restoration. A minimum sound dentine height of 1.5-2 mm is required between the core and crown margins. This should provide adequate resistance to the lateral forces imparted on the restored tooth. Ideally, this ferrule should be continuous around the entire circumference of the tooth.

The Ferrule Effect The ferrule provides bracing or casing action to protect the integrity of the root.

Requirements of An Ideal Post Minimum preparation. Resistance to fatigue. Elastic modulus similar to dentin. Non corrosive. Retentive (post & Head). Easy to adjust and fit. Radiopaque. Adequate material Easy Removal

Types of Posts Prefabricated Post Cast Post (wax pattern needed)

Prefabricated Post

Cast post direct waxing

Indirect impression technique

Cast Posts Advantages Preservation of maximum tooth structure Provision of anti-rotational properties Core retention Less chances of vertical fractures during preparation High strength Disadvantage Time consuming complex procedure Indications: Elliptical canals Flared canals

Prefabricated Tapered Posts Advantages: Conserves tooth structure High strength and stiffness Disadvantages: Low retention Longitudinal splitting of remaining root Indications: Small circular canals Very tapered canals

Prefabricated Threaded Posts Advantage High retention Disadvantages Stresses generated in canal may lead to fracture Does not conserve coronal and radicular tooth structure Indication Only when maximum retention is essential

Fiber Reinforced Post Advantage Esthetic Disadvantage low strength Indication when there is sufficient tooth structure when there is no high occlusal loads

Fiber Post

CORE part

Materials Used For Core Build Up Direct Placement: Amalgam Composite Glass ionomer type II Indirect Placement Casting

Composite Core Advantages Good compressive strength Easy to manipulate Rapid polymerization Dentin bonding Disadvantages Polymerization shrinkage Poor dimensional stability Water sorption Technique sensitive Air bubbles and spaces Indication Excellent build-up material for posterior and anterior teeth if isolation assured

Amalgam core Advantages Reduced marginal leakage Better dimensional stability Better compressive strength Better modulus of elasticity Disadvantages Mercury sensitivity Low tensile strength Corrosion with base metal Indication Molars with adequate coronal tooth structure

Glass Ionomer Core Advantages Anticariogenic Adhesive Easy to manipulate Disadvantages Low resistance to fracture Low retention to preformed post Sensitive to moisture Indication Teeth with minimum tooth structure missing

Gingival management Retraction cord Gingivectomy Laser Electro-cautery Rubber dam