Ferrule 3

FERRULE-THE ONLY RULE!!

MEANING OF THE TERM

•FERRUM means “Iron”

•VIRIOLA means “Bracelet”

(Brown1993).

COMPONENTS OF TOOTH RESTORED WITH POST-CORE-CROWN

What is Ferrule?

•At one time dowel was thought to strengthen the remaining tooth structure and was referred to as IntracoronalCrutch by Rosen.

•This notion has been rejected now.

•A key element of tooth preparation when using a dowel & core is the incorporation of Ferrule

•A ferrule is a metal ring or cap used to strengthen the end of a stick or tube.

• It has been proposed that the use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing root-filled teeth.

MISINTERPRETED AS..

•The remaining amount of sound dentine above the finish line..

•As it is not the remaining tooth structure.

Jotkowitz A:Rethinking Ferrule:a new

approach to an old dillemma.British

Dental Journal,2010;209(1):25-33

•A ferrule, in respect to teeth, is a band that encircles the external dimension of residual tooth structure. A 2 mm height of tooth structure should be available to allow for a ferrule effect.

(Galen WW, Mueller KI: Restoration of the Endodontically Treated Tooth.

In Cohen, S. Burns, RC, editors: Pathways of the Pulp, 10th

Edition.)

FERRULE:• There are four advantages of this effect:

1: Promoting hugging action,

2: Preventing the shattering of the root,10

3: Reducing the wedging effect of a tapered dowel, and

4: Resisting functional lever forces and the lateral forces exerted during dowel insertion.11

Refrences:Rosen H: Operative procedures on mutilated endodontically treated teeth. J Prosthet Dent 1961;11:973-986. Sorensen JA, Engelman MJ: Ferrule design and fracture resistance of endodontically treated teeth. J Prosthet Dent 1990;63:529-536

•The role of a dental ferrule, an embracement of the hard tissue by crown restoration of a certain height, is mandatory for a post-endodontic reconstruction of severely damaged teeth. A dental ferrule preparation combines a shoulder preparation with parallel coronal dentin walls. The tooth tissue is enclosed by the crown improving the overall resistance of the restoration

A dental ferrule is an encircling band of cast metal around the coronal surface of the tooth.

DEFINITION

•The ferrule effect be defined as ‘‘a 360 metal collar of the crown surrounding the parallel walls of the dentine extending coronal to the shoulder of the preparation”. (Sorensen & Engelman)

•Sorensen & Engelman (1990) advised that as much coronal tooth as possible should be preserved, and a butt-joint margin between the core and tooth be used, i.e. minimal taper.

•The presence of a 1.5- to 2-mm ferrule has a positive effect on fracture resistance of endodontically treated teeth.

•The use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing root-filled teeth.

• A protective, or ‘ferrule effect’ could occur owing to the ferrule resisting stresses such as

•functional lever forces,

•the wedging effect of tapered posts and

•the lateral forces exerted during the post insertion.

(Sorensen & Engelman1990).

2mm Uniform Ferrule Vs Non-Uniform Ferrule

Aggarwal, et al:Effect of ferrule on fracture resistance. Journal of Conservative Dentistry , 2014 ;17 (2):183-7

CROWN FERRULE: Ferrules created by the overlying crown engaging tooth structure.

CORE FERRULE: Ferrules that are part of a cast metal.

CLASSIFICATION OF FERRULE

Jotkowitz A:Rethinking Ferrule:a new

approach to an old dillemma.British Dental

Journal,2010;209(1):25-33

Category A : No anticipated risk

Category B : Low risk

Category C : Medium risk

Category D : High risk

Category X : No ferrule

HEIGHT <2mmTHICKNESS <1 mm A: no

anticipated risk4 walls

3 walls

Distal or mesial

missing B: low risk

2 walls

buccal

lingual

1 wallBuccal or

lingual missing

Light lateral loads

Heavy lateral loads

Light lateral loads

Heavy lateral loads

C: medium risk

2 wallsmesial

distal

2 walls (adjacent)

1 wall

0 ferrule

D: high risk

Non restorable

FACTORS AFFECTING FUNCTIONALITY OF FERRULE

Trushkowsky RD:Restoration of endodontically treated teeth:

Criteria and technique considerations. Quintessence Int 2014;45:557–67

•1.Ferrule height

Greater the height of remaining tooth structure better the fracture resistance.

Ferrule height of 1.5 to 2 mm of vertical tooth structure would be the most beneficial.

The crown should encompass at least 2 mm past the tooth core connection to achieve the most protective ferrule effect.

2. Ferrule width

Esthetic restorations often require fairly aggressive preparations at the gingival margin and sometimes buccaldefects such as abfraction may compromise the buccal dentin wall.

It has been accepted that the walls are considered too thin if they are less than 1 mm in thickness, and would negate the ferrule effect.

3. No of walls and ferrule location

A circumferential ferrule would be optimal but caries may affect the interproximal areas and abrasion or erosion the buccal walls.

A crown preparation will further reduce the wall thickness and only a partial ferrule will remain.

Ng et al said that good palatal ferrule is as effective as having a complete “all around” ferrule.

Al-Wahadni and Gutteridge55 found having a 3-mm ferrule on the buccal aspect was better than having no ferrule at all.

4.Type of tooth and extent of lateral load

Anterior teeth are loaded non-axially

Posterior teeth are loaded occluso-gingivally.

Anterior teeth with a deep overbite and parafunction are at a higher risk of failure.

Teeth that are in group function with long maxillary buccal cusps produce higher lateral forces than if there was canine guidance.

5. Type of postCast posts have been used for many years for the support of the final restoration.

However, in recent years this type of restoration has been progressively replaced by composite cores with a glass fiber post or metal post.

Fiber-reinforced posts have shown positive results as compared to metal posts.

6. Core materials

Composite resin with dentin bonding agent has frequently been implicated as material that can strengthen the tooth and reinforced cusps as compared to amalgam.

TYPES OF FRACTURE

A B

•Repairable fractures :above cemento-enamel junction (CEJ), horizontal cervical fracture, core-tooth fracture

• Non-repairable oblique fracture :entirely below CEJ, fracture in the middle or apical third of the root, vertical root fracture.

Non repairable fractures are more common with cast dowel post and 2mm ferrule

Reparable fractures are seen with fiber-reinforced posts and 2mm ferrule.

Aggarwal, et al:Effect of ferrule on fracture resistance. Journal of Conservative Dentistry , 2014 ;17 (2):183-7

HOW TO CREATE FERRULE IN A NO FERRULE CASE????

• There are two methods:

1.Crown lengthening

2.Forced eruption