ACCESS CAVITY PREPARATION IN ANTERIOR TEETH

Submitted By:

SONAL CHAUDHARY

Batch 2007-08

INTRODUCTION

COMPONENTS OF THE ROOT CANAL SYSTEM

OBJECTIVES AND GUIDELINES FOR ACCESS CAVITY PREPARATION

ARMAMENTARIA

PRINCIPLES OF ENDODONTIC CAVITY PREPARATION

ACCESS CAVITY PREPARATION

MORPHOLOGY & ACCESS CAVITY PREPARATIONS FOR INDIVIDUAL TEETH

ERRORS IN ACCESS CAVITY PREPARATION

REFERENCES

Introduction

The hard tissue encompassing the dental pulp can take a variety of configurations and shapes.

A thorough knowledge of tooth morphology, careful interpretation of angled radiographs, and adequate access to and exploration of the tooth's interior are prerequisites for treatment

Components of the Root Canal System

The entire space in the dentin where the pulp is housed is called the “ ROOT CANAL SYSYTEM”.

ROOT CANAL SYSTEM is divided into 2 portions:

PULP CHAMBER – located in the Anatomic Crown of the tooth.

PULP/ROOT CANAL (S) – located in the Anatomic Root.

OBJECTIVES

To Remove All Caries

To Conserve Sound Tooth Structure

To Completely Unroof The Pulp Chamber

To Remove All Coronal Pulp Tissue

(Vital Or Necrotic)

To Locate All Root Canal Orifices

GUIDELINES Visualization of the Likely Internal Anatomy :

Diagnostic radiographs;

Evaluating angled periapical radiographs;

Examination of tooth anatomy at the coronal,

cervical, and root levels.

. Law of Color change : The color of the pulp chamber floor

is always darker than the walls.

First Law of orifice location : The orifices of the root canals are always located at the junction of the walls and the floor.

2.Preparation Of The Access Cavity Through The Lingual & Occlusal Surfaces :

Access cavities of anterior teeth are usually prepared through the lingual tooth surface, and those on the posterior teeth are prepared through the occlusal surface.

3.Removal Of All Defective Restorations And Caries Before Entry Into The Pulp Chamber

4.Removal Of Unsupported Tooth Structure

5.Location, Flaring, And Exploration Of All Root Canal Orifices:

A sharp endodontic explorer is used to locate canal orifices .

Next, all canal orifices & the coronal portion of the canals are flared to make instrument placement easier.

The canals are then explored with small, pre-Curved K-files (#6,#8, or #10).

A lubricating agent (e.g., RC-Prep) may be used on instruments & introduced in the Canal.

6.Inspection Of The Pulp Chamber, Using Magnification And Adequate Illumination:

For determining the location of canals; negotiating constricted, curved & calcified canals; & debriding and removing tissue & calcifications from the pulp chamber.

ARMAMENTARIA

Magnification & Illumination

Handpieces

Burs

Endodontic explorer (DG-16, DE-17)

Endodontic Spoon

#17 Operative Explorer

Ultrasonic Unit & tips

Principles of Endodontic Cavity Preparation

According to Ingle, Endodontics follows the basic principles by G.V. Black with slight modifications to explain principles of endodontic cavity preparation:

Endodontic Coronal Cavity Preparation :

I. Outline Form

II. Convenience Form

III. Removal of the remaining carious dentin and defective restorations.

IV. Toilet of the cavity

Endodontic Radicular Cavity Preparation:

I and II. Outline form and Convenience form

IV. Toilet of the cavity

V. Retention form.

VI. Resistance form

Access Cavity Preparation

Removal of caries & permanent restorations Initial external outline form Penetration of the pulp chamber roof Complete roof removal Identification of all canal orifices Removal of the lingual shoulder & orifice & coronal

flaring Straight line access determination Visual inspection of the access cavity Refinement & smoothing of restorative margins

ACCESS PREPARATION FOR ANTERIOR TEETH

MAXILLARY CENTRAL INCISOR

Internal anatomic structure of Pulp chamber dictates Shape & Size of Access opening.

Average length : 23.0mm

Always has one Root & Type I canal configuration.

Root is bulky with slight distal axial inclination but rarely has Dilacerations.

Pulp cavity is wider towards incisal area and then tapers to the apex.

Majority of roots are straight (75%), some curve distally (8%), mesially (4%) palatally (4%) or labially (9%).

Initial External Outline Form

(A) For an intact tooth, begin in the center of the lingual surface of the anatomic crown.

A #2 or #4 round bur or a tapered fissure bur in a high-speed handpiece is used to penetrate through the enamel and slightly into the dentin (approximately 1 mm).

(B) An outline form is created, similar in geometry to an ideal access shape for the particular anterior tooth; it is one half to three fourths the projected final size of the access cavity.

(C)The bur is directed perpendicular to the lingual surface as the external outline opening is created.

Penetration of the pulp chamber roofExperienced clinicians - high-speed handpiece, but less experienced - tactile sensation of a slow-speed handpiece.

(D) With the same round or tapered fissure bur - change the angle of the bur from perpendicular to the lingual surface to parallel to the long axis of the root .

Penetration into the tooth is accomplished along this root's long axis until the roof of the pulp chamber is penetrated; frequently a “drop-in effect” is felt when this occurs.

Complete Roof Removal

(E) The remaining roof is removed by catching the end of a round bur under the lip of the dentin roof and cutting on the bur's withdrawal stroke - allows the internal pulp anatomy to dictate the external outline form of the access opening.

All of the pulp chamber roof, including the pulp horns, must be removed.

All internal walls must be flared to the lingual surface of the tooth.

Identification of canal orifices With an endodontic explorer

Used for reaching, feeling, and often digging at the hard tissue using tactile sensation.

Removal of the Lingual Shoulder

This is the lingual shelf of dentin that extends from the cingulum to a point approximately 2 mm apical to the orifice . Its removal aids straight-line access and allows for more intimate contact of files with the canals walls for effective shaping and cleaning.

MAXILLARY LATERAL INCISOR: Similar to that for Maxillary Central Incisor.

Average length : 22.5mm

Always has one Root & type I Canal Configuration

Access is Smaller in all dimensions & More ovoid

Access opening – similar to central, but is smaller and more ovoid in shape.

Technique for entry is same except that a smaller i.e. a no. 2 round bur may be used instead of no. 4 as for central.

Access cavity preparation in maxillary lateral need to be modified in certain cases such as in anomalies such as dens invaginatus, peg laterals and talon cusps.

Maxillary canine Average length – 26.0mm.

Lateral canals 24%

Roots have a Distal curve 32%; Labial curve 13%, straight 39%, lingual curve 7%

Extensive, ovoid, funnel shaped coronal preparation.

Long, beveled, incisal extension.

Maxillary Anterior Teeth: Errors in Cavity Preparation

Perforation :-Failure to complete convenience extension toward the incisal

Gouging of the labial wall caused by failure to recognize the 29-degree lingual-axial angulation and

LATERAL PERFORATION

Pear Shaped preparation

Discoloration Ledge Formation

MANDIBULAR CENTRAL INCISOR Average length : 21.5mm

One root & Canal configuration can be type I ,II, III.

For central incisors: type 1 canal configuration in 70.1% cases, type 2 in 23.4% cases & type 3 in 6.5% cases.

Average length : 22.4 mm

One root & Canal configuration can be type I ,II, III.

Type 1 (56.9%), Type 2 (14.7%) & Type 3 (29.4%);

Lateral Canals (13.9%).

When Two Canals are present , Labial canal is straighter.

Point of division for divided canals is generally in Cervical third of root

Shape is Long Oval, with greatest dimension oriented inciso-gingivally.

MANDIBULAR CANINE: 

Average length : 24.0mm

One root; rare cases : 2 roots

One root may have type I (94%)

& III Canal Configurations.

Access cavity is Ovoid & may extend Incisally for access

Lateral canals – 9.5%

Distal curve – 20%

Extensive, ovoid, funnel shaped coronal preparation. Beveled incisal extension.

Mandibular Anterior Teeth: Errors in Cavity Preparation

Gouging at the labio cervical wall

Gouging of labial wall: failure to recognise the 20-degree lingual-axial inclination of tooth

Gouging of distal wall: failure to recognise 17-degree mesial-axial angulation of the tooth

Failure to explore, debride

or fill the second canal

Discoloration of crown Ledge formation

REFERENCES

Pathways of pulp; COHEN -10th

editionEndodontic therapy- Franklin Weine

Endodontics - Ingle 5th edition and 6th edition

Endodontic practice -Louis I. grossman