Working Length Determination and Root Apex AnatomyByDr.Mahavosh QaziBDS

Introduction •Determination of an accurate working

length is one of the most critical steps of endodontic treatment.

•Cleaning, shaping and obturation cannot be accomplished accurately unless working length is determined correctly.

Definition•It is defined as: “The distance from a

coronal reference point to a point at which canal preparation and obturation should terminate”

Reference Point• A reference point

is that site on the insical or occlusal surface from which measurements are made.

• A reference point is chosen which is stable and visualized during preparation.

Anatomy of the Root ApexThree anatomic & histologic landmarks at the root apex

•Apical Constriction•Apical Foramen•Cementodentinal Junction

APICAL CONSTRICTION• Also termed as Minor Diameter of the canal

• It is the part of the root canal which is smallest

• Reference point clinicians use to terminate cleaning/shaping & obturation

• AC is generally 0.5-1 mm inside the AF

• Postoperative discomfort is greater when this area is violated

Dummers classification

Cementodentinal Junction •CDJ is the point where cementum meets

dentine

•It is the point where pulp tissue ends & periodontium begins

•Approximately 1mm from AF

APICAL FORAMEN•Also termed as Major Diameter of the canal

•Not always located at anatomical apex of tooth

•Space between AC & AF is funnel shaped or hyperbolic

•Mean distance between AC & AF is 0.5 mm in young & 0.67 mm in older individuals due to cementum deposition

CLINICAL CONSIDERATIONS•Location of AC & AF is difficult clinically•Radiographic apex is a more reliable

reference point •Clinical & biological evidence indicates in

vital cases a favorable point to terminate therapy is 2-3 mm short from radiographic apex (RA)

•This leaves an apical pulp stump which prevents extrusion of debris & filling materials into periradicular tissues

Cont...•In cases of necrotic pulp & apical

periodontitis bacteria & by products are present in apical root

•In these cases terminate therapy 0.5-1 mm from RA

Apical ConfigurationAPICAL STOP

Complete barrier at the apexDentine chips are packed

APICAL SEAT Incomplete barrier at the apex

OPEN APEX No barrier

Wide vs Narrow Apical PreparationPREPARATION BENEFITS DRAWBACKS

NARROW APEX Minimal risk of transportation, extrusion of irrigants & filling materials

Little removal of infected dentine & questionable rinsing effect during irrigation

Can be combined with tapered preparation to counteract drawbacks

Possibly compromised disinfection Not suitable for lateral compaction

Wide Apex Removal of infected dentine

Risk of preparation errors

Access of irrigants & medications to apical third

Risk of extrusion of debris & filling materialsNot ideal for thermoplastic obturation

Armamentarium for WL determination•10 K file•15 and 20 K file•Radiographs•Apex locators•Paper points

WL determination methods• Radiographic Method

• Electronic Apex Locator

• Use of anatomical averages and knowledge of anatomy

• Tactile sensation

• Moisture on a paper point

Radiographic Method• Using pre op radiographs to gauge root morphology,

number and curvature of roots, acts as initial guide.

Apex Locator

Apex LocatorAdvantages Disadvantages

• Reduces number of radiographs which need to be taken so minimizes time

• Also useful in cases where apical foramen is at a distance from RA

• Helpful for detecting perforations

• Researches say it is useful in detecting fractures and resorptions as well

• Some have added vitality testing functions

• Intact vital tissue, inflammatory exudate and blood can cause inaccurate readings

• Metallic restorations, saliva or caries can cause short circuiting

• Dentine debris and calcifications can also affect

• Records not able to be maintained

• Not recommended for patients with cardiac pacemakers

Tactile Sensation

•If the coronal portion of the canal is not constricted, clinician may detect an increase in resistance as the file approaches the apical 2-3 mm. This detection is by tactile sense.

•In this region the canal frequently constricts before exiting the roots. There is also tendency for canal to deviate from radiographic apex.

Paper Point Moisture• In an immature (wide open) apex,

the most reliable means of determining working length is to gently pass the blunt end of a paper point into the canal after profound anesthesia has been achieved.

• The moisture or blood on the portion of the paper point that passes beyond the apex maybe an estimation of working length or the junction between the root apex and the bone.

Thanks For listening...