INDICATION, CONTRA-INDICATION AND FACTORS AFFECTING ADHESION OF POST CORE

SYSTEM

PRESENTED BY

DR AGHIMIEN OSARONSE

OUTLINE• INTRODUCTION• POST....DEFINITION AND CLASSIFICATION• CORE....DEFINITION AND CLASSIFICATION• INDICATIONS FOR POST CORE SYSTEM• CONTRA-INDICATIONS.. GENERAL CONSIDERATION TOOTH ASSESSMENTADHESION OF POST-CORE SYSTEM DEFINITION OF ADHESION MECHANISMS OF ADHESION INTERFACES OF ADHESION

OUTLINE COND’T

• FACTORS AFFECTING ADHESION OF POST CORE SYSTEM

WORKING ENVIRONMENT INTEGRITY OF ROOT CANAL DENTIN TYPE OF LUTING OR ADHESIVE USED POST CORE MATERIALS AND THIER

PROPERTIES

INTRODUCTION

The longevity of a post core system depend highly on how well they adhere together whether between the post and core, post and tooth, core and tooth or between the post-core and the coronal restoration.

POST

Definition; these are restorative dental materials place in the

root of a structurally damage tooth to provide adequate retention for the core and coronal restoration.

when insufficient crown tissue is left on a vital tooth to accommodate placement of a core (to support a crown), elective root treatment may be undertaken to allow for placement of an intra-radicular post

CLASSIFICATION OF POST

Preformed or custom made;Rigid or non-rigid; Au-Pd and carbon fibres

respectivelyStiff or resilience; rigid post are stiffer

compare to non-rigid posts.Aesthetic or non aesthetic; ceramics post are

of better aesthetic anteriorly than carbon fibre[black]

CORES

Definition; these are restorations place in order to build

up a broken down tooth replacing carious, fracture or missing coronal structures before the final indirect restoration

CLASSIFICATION OF CORE

Base on function; Space filler; amalgam, RmGIC, GIC Structural; amalgam, GIC, Composite

Base on method of preparation; Direct; amalgam, resin composite, GIC Indirect; cast metal e.g gold

INDICATIONS FOR POST-CORE SYSTEM

A. Amount of tooth structure remaining; excessive loss from caries, fracture or from previous restoration weaken tooth and would not provide enough support for the extra-coronal restoration.

B. Functional load of the teeth; abutement teeth for fixed or removable partial denture that is compromised; teeth that exhibit extensive wear from bruxism, heavy occlusal load or heavy lateral function require post, core and crown.

3. Teeth liable to fracture following endodontic treatment; creation of access and cleaning and shapening of the tooth during endo treatment further weaken a tooth hence, the need for a post-core for the indirect restoration.

4. vital tooth with insufficient coronal tooth that will support the indirect restoration; these teeth would require an elective root treatment for the post-core that will provide the scaffold for the crowning.

5. Anatomic position of teeth; a posterior tooth that would loss more tooth structure from an endo treatment compare to an anterior teeth would be needing a post-core to support the extra-coronal restoration to help withstand the masticatory stress.

CONTRAINDICATIONS FOR POST-CORE

General considerations; Poorly motivated patients; these patients will not

keep to appointment and probably can not maintain the restoration.

Poor oral hygiene; it shows a low level concern about the oral environment. This could predispose to periodontal disease condition, thereby compromising the tooth support

TOOTH ASSESSMENT

A. Tooth support; bony support restricted to less than one third of the apical regions is contra-indicated for a post-core. Tooth extremely mobile i.e > grade 3

B. Presence of persistent periapical pathosis that is refuses to subside. If a post-core is place there could be apical re-infection

C. Poorly root- filled tooth; marginal leakage from apical aspect could precipitate apical re-infection

ADHESION OF POST-CORE SYSTEMADHESION; this is the proper adapting or close fitting of a post core system to

the root canal space.MECHANISM OF ADHESION; chemical e.g silanization micro-mechanical e.g from phosphoric acidINTERFACES OF ADHESION B/W root canal space and luting/adhesive agent B/W post and luting/adhesive agent B/W post and core B/W core and coronal restoration

FACTORS AFFECTING THE ADHESION OF POST-CORE SYSTEM

1) WORKING ENVIRONMENT; moisture control saliva and blood contamination; this could encourage bacterial colonization with

further release of enzyme that would breakdown the interface.

INTEGRITY OF ROOT CANAL DENTIN

Adequate removal of root filling; if this is not done properly, it could desiccate the canal surface there reducing the adhesive strength of the luting agent e.g GIC

Presence of sealing; eugenol have been said to reduce bonding strength of Zinc phosphate and decrease polymerisation of resin, ethyl alcohol and phosphoric acid etching can be use to remove eugenol residue.

Presence of smear layer; in case of further instrumentation of the canal dentin, the smear layer if not removed could interfere with bonding. Acid treatment would do for this.

A sound dentin integrity is needed for the resin tag[ especially the minor tags] formation which would aid chemical bonding to the mayerials

LUTING AGENTS AND ADHESIVES USED

1. ZINC PHOSPHATE; it retention is by mechanical means only, it doesn’t bond to tooth surface [ hence, sandblasting of the post is advocated] leaving space for bacterial proliferation which would eventually cause decementation and postoperative sensitivity.

2. GIC and RmGIC; it bonds chemically, its setting is moisture sensitive causing to expand. This does favour metallic post but causes all-ceramics to fracture. Adhesion can be improve when polyacrylic acid or phosphoric acid is used to pre-treat the preparation to remove smear layer

• Adhesive cement; this tend to give better adhesion to the post and canal surface with greater resistance to debonding. Self cure, chemical and the dual cure can be used. The dual cure has the advantage of command set, with the need of extending the length of the post for retention.

POST CORE MATERIALS AND THIER PROPERTIES

Materials range from cast gold to fibre[ carbon, quartz, glass] , to ceramic, and to fibre re-inforce composite[FRC] post.

SURFACE FINISHING; metal post-core system could be smooth or rough. Adhesion of these post can be improve by sandblasting or micro-abrasion.

chemical constituent; e.g FRC post can be pre treated with silanization alone or with potassiun permanganate, sodium ethoxide e.t.c

porcelain post can be pre-treated with hydrofluoric acid and ammonium bifluoride for ceramics.

These mtds allow for both chemical and micro-mechanical adhesion.

Other considerations

1. Amount of functional load applied on the tooth and the restoration

2. Effect of repeated thermocycling

conclusion

It is obvious the post core system adhesion is an important factor to consider when embarking on such treatment procedure to ensure longevity of the treatment.

GOOD MORNING.