ACCESS CAVITY

PREPARATION

CONTENTS:

INTRODUCTION

RULES FOR ACCESS PREPARATION

PRINCIPLES FOR ENDODONTIC ACCESS PREPARATION

ARMAMENTARIUM FOR ACCESS CAVITY PREPARATION

ACCESS CAVITY PTREPARATION OF VARIOUS TEETH AND

ERRORS IN ACCESS PREPARATION

MODIFIED ACCESS CAVITY PREPARATION

RECENT CONCEPTS IN ACCESS CAVITY PREPARATION

CONCLUSION

REFERENCES

INTRODUCTION:

All the treatment that follows hinges on the accuracy and correctness

of the entry

Franklin S. Weine

Access cavity is first objective procedure done on an endodontically

compromised tooth.

Endodontic treatment may be considered as a stair, each step representing a

basic phase. To reach the top i.e. to effectively salvage a compromised tooth

to its form and function in the masticatory apparatus, meticulous care is

required to be shown at each step.

The main objective of this preparation is to enable direct access to the

apical foramen by an endodontic instrument, not just exposing canal orifice.

It has been well established that a root with locally tapered root canal and a

single apical foramen is more of a desire than a reality. From earlier studies

to the recent sophisticated works it is clear that multiple foramina, extra root

canals, lateral and accessory canals, deltas loops, cul de sac etc are present

in most teeth. This notes the need for a proper access opening even more

important, since without proper access, the root canal system cannot be

properly negotiated and therefore treated.

Case selection

X-ray examination

Access opening

Cleaning & shaping

Obturation

Proper restoration

Accessory canals: found in apical III of the root and are branches of main

root canal. End in accessory foramen. More in young age as they later get

obliterated by cementum.

Accessory canals: which opens approximately at right angles to the main

pulp cavity are termed lateral canals and generally found in furcation area.

Definition of access cavity preparation:

Defined as coronal opening into pulp cavity required for effective

cleaning, shaping and filling of pulp space during root canal therapy.

- Harty Rugston dental dictionary

RULES FOR PROPER ACCESS PREPARATION

To ensure the most efficient access cavity preparation, the following

rules should be observed:

1) The objective of entry is to give direct access to the apical

foramina, not merely to the canal orifices.

Because it is the apical foramen of each canal that must be sealed,

the access cavity must allow for removal of any tooth structure that might

impede the preparation and filling of that area.

Direct access to apical foramen

2) Access Cavity preparations are different from typical operative

occlusal preparation.

The typical occlusal cavity preparations used in operative dentistry

are based on the topography of occlusal grooves, pits, and fissures, and on

the avoidance of underlying pulp. The access cavity preparations for

endodontic therapy are designed for efficiently uncovering the roof of the

pulp, chambers and providing direct access to the apical foramina by way

of the pulp canals. Because the two types of preparations must satisfy

different criteria, it is only natural that they have differing configuration.

Different from typical occlusal cavity preparation

3) The likely interior anatomy of the tooth under treatment must be

determined.

Before starting the access, radiographs taken from at least two

different angles must be studied. Operator should have proper knowledge

regarding typical length, number and configuration of roots and canals.

Thus information gained before initiation of preparation will greatly

facilitate the entry as well as further treatment.

4) When canals are difficult to find, the rubber dam should not be

placed until correct location has been confirmed.

It is often difficult to prepare access in a malposesd tooth or one

that is part of a bridge or splint. The occlusal anatomy, which ordinarily

gives excellent clues to the position of the underlying canals, may be

considerably altered. Teeth with and / or deep restoration causing heavy

dentinal sclerosis also may cause problems. Therefore, in such teeth, it is

best to make the initial poison of the access preparation before the

placement of the rubber dam so that the shape and inclination or the

adjacent teeth, the gingival tissues, and the hard structures covering the

roots help in determining the position of the canals.

Once the roof of the chamber is penetrated and the correct access is

verified, the rubber dam may be applied. Because the canals will be

enlarged considerably with heavy irrigation, the effect of any

microorganism contamination before dam placement is minimal. If for some

reason it is mandatory to use the rubber dam for every phase of treatment,

the access cavity for complex cases should be prepared with multiple tooth

rather than single tooth isolation. This will allow for visualization of

adjacent teeth while the dam is in place.

5) Endodontic entries are prepared through the occlusal or lingual

surface never through the proximal or gingival surface.

When existing proximal or gingival opening is done from existing

restoration or carious lesion, the canal enlarging instruments must be bent

at severe angles to pass through the access and still perform their function.

Inadequate canal preparation and/or broken instruments may result. When

proximal or gingival tooth destruction occurs, affected areas should be

excavated and restored, with either a temporary seal, or a permanent filling

material .Then the normal access cavity is prepared through the occlusal or

lingual surface.

6) As part of the access preparation, the unsupported cusps pf

posterior teeth must be reduced.

Endodontic therapy requires the removal of much of the central

portion of the treated tooth, greatly reducing resistance to stress. Although

this problem is solved by the placement of a proper restoration after

treatment, the tooth is severely weakened until that time. Therefore, as part

of access preparation all unsupported cusps must be reduced by trimming

with a tapered fissure carbide or diamond stone until a definite clearance

in occlusal and lateral movement is obtained. This decreases the chances

for cuspal fracture beneath the gingival or bony attachments, which is so

difficult to repair, or vertical fracture of the root which is hopeless.

PRINCIPLES OF ENDODONTIC ACCESS PREPARATION:

Endodontic preparation deal with both coronal and radicular cohorts

each prepared separately but ultimately flowing together into a single

preparation.

Coronal cavity preparation principles:

I. Outline form: outline form of the endodontic cavity must be correctly

shaped and positioned to establish complete access for instrumentation from

cavity margin to apical foramen. External Outline form is established by

mechanically projecting the internal anatomy of the pulp onto the external

surface. This may be accomplished only by drilling into the open space of

the pulp chamber and then working with the bur from the inside of the tooth

to the outside, cutting away the dentin of the pulpal root and walls

overhanging the floor of the chamber.

3 factors of internal anatomy must be considered:

1) Size of the pulp chamber: in young patients, these preparations must be

more extensive than in older patients, in whom the pulp has receded and

pulp chamber is smaller in all 3 dimensions.

2) Shape of pulp chamber: finished outline form should accurately reflect

the shape of the pulp chamber. E.g. coronal pulp of maxillary premolar is

flat mesiodistally but is elongated buccolingually. The outline form is,

therefore, an elongated oval that extends buccolingually rather than

mesiodistally, as does blacks operative cavity preparation.

3) Number, position and curvature of root canals: to prepare each canal

efficiently without interference, the cavity walls often have to be

extended to allow an unstrained instrument approach to the apical

foramen. When cavity walls are extended to improve instrumentation the

outline form is materially affected.

II. Convenience form: makes more convenient preparation and filling of

the root canal.

4 important benefits are:

a) Unobstructed access to the canal orifice: enough tooth structure must

be removed to allow instruments to be placed easily into the orifice of

each canal without interference from overhanging wall. Clinician must

be able to see each orifice and easily reach it with instrument points.

One should always search for extra canals.

Loebke stated that the entire wall need not be extended in the event

that instrument impingement occurs owing to a severely curved root or

an extra canal. In extending only that portion of the wall needed to free

the instrument, a cloverleaf appearance may evolve as the outline form

termed as SHAMROCK PREPARATION.

Shamrock preparation.

b) Direct access to the apical foramen: enough tooth structure must be

removed to allow the endodontic instrument freedom within the coronal

cavity so they can extend down the canal in an unstained position.

c) Extension to accommodate filling techniques: to make certain filling

techniques more convenient or practical. E.g. rigid vertical pluggers are

used in a vertical thrust, and then the outline form may have to be widely

extended to accommodate these heavier instruments.

d) Complete authority over the enlarging instrument: if the instrument

is impinged at the canal orifice by tooth structure that should have been,

the dentist will have lost control of the direction of the tip of the removed

instrument, and the intervening tooth structure will dictate the control of

the instrument.

If, on the other hands the tooth structure is removed around the orifice

so that the instrument stands free in this area of the canal, the instrument

will then be controlled by only 2 factors; the clinician fingers on the

handle of the instrument nothing is to intervene between these two

points.

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

Caries and defective restorations remaining in an endodontic cavity

preparation must be removed for 3 reasons.

1) To eliminate mechanically as many bacteria as possible from the

interior of the tooth.

2) To eliminate the discolored tooth structure, that may ultimately lead

to staining of the crown.

3) To eliminate the possibility of any bacteria laden saliva leaking into

the prepared cavity.

- If carious perforation of the wall is allowing salivary leakage, the area

must be repaired with cement, preferably from inside the cavity cavit,

cavit G.

- If lateral wall is extensively destroyed, it is important that restoration be

postponed until the radicular preparation has been completed as it is easy

to complete radicular preparation through an open cavity than through a

restored crown. As long as a rubber dam can be placed on the tooth, it

need not be built up with amalgam, cement or an orthodontic band,

having to work through a hole only complicate the endodontic procedure.

IV. Toilet of the cavity

All the caries, debris and necrotic material must be removed from the

chamber before the radicular preparation is begun. If the calcified or

metallic debris is left in the chamber and carried into canal, it can cause

obstruction.

- Soft debris - increases bacterial count

- Round burs

Long blade endodontic spoon excavation

Sodium hypochlorite irrigation

Chamber may be finally wiped out with cotton, and a careful flush of

air will eliminate the remaining debris.

Radicular cavity preparation:

Objectives: 2 objectives

- Through debridement of the root canal system and the specific shaping

of the root canal preparation to receive a specific type of filling.

- Ultimate objective, however, should be to create an environment in

which the bodys immune system can produce healing of the apical

periodontal attachment apparatus.

Cleaning and debridement of the root canal:

- Skillful instrumentation + liberal irrigation will help to eliminate most

bacterial contaminants of the canal as well as the necrotic debris and

dentin.

- Intracanal medication - sterilization during intra appointment period.

Principles

I) Outline form and convenience form: must be continually evaluated by

monitoring the tension of the endodontic instruments against the margins of

the cavity. They must stand free and clear of all interference. Access must

have to be expanded if instruments start to bind.

II) Toilet of the cavity: through douching through irrigation is important

for total debridement, through certain hooks and crannies of the root canal

system are virtually impossible to reach with any device or system. But

success is possible in spite of microscopic remaining debris.

III) Retention form: Initial primary GP point fit tightly in apical 2-3mm of

the canal. These nearly parallel walls ensure the firm seating of this

principal point. Other techniques strive to achieve a continuously tapering

funnel from the apical foramen to the cavosurface margin. Retention form in

these cases is gained with custom fitted cones and warm compaction

techniques. These final 2-3mm of the cavity are the most crucial as this is

where the sealing against future leakage or percolation into the canal takes

place. This is also the region where accessory or lateral canals are most apt

be present.

IV) Resistance form: resistance to overfilling is the primary objective of

resistance form.

Maintaining the integrity of the natural constriction of the apical foramen is

a key to successful therapy.

Violating this integrity by over instrumentation leads to complication.

1) Acute inflammation of periradicular tissue from the injury by

instrument, bacteria or canal debris forced into tissue.

2) Chronic inflammation of this tissue caused by presence of a foreign

body - filling material forced there during obturation.

3) Inability to compact the root canal filling because of the loss of the

limiting apical termination of the cavity apical stop.

Cretention form

Bresistance form

ARMANENTARIUM FOR ACCESS PREPARATIONS:

Tray set up should contain following things:

- Front surface mirror - For maximum visibility

- Endodontic explorer - One end comes to a point to aid in locating

orifices, while the other has a slight hook to cheek shelves at edges of the

preparation.

- Endodontic excavator - to remove decay and pulp tags.

- Plastic instrument

- Amalgam plugger

- Spatula

- Cotton pliers

- Broaches

- Glass slab, cotton pellets

- Burs - long shank no. 701/558, No. 4, No. 2 and specially prepared no.

701 or 558 with a rounded or safe tipped end to prevent going.

- Rubber dam materials should be available i.e. sheets, punch, frame,

clamp holder and clamps

- No. 26 and 27 - wingless clamps for molars SS White

- No. 12A and 12B - winged clamps for molars Colombus Dental

- No. 209 - for bicuspids and bulky anterior teeth SS White

- No. 211 or 9 - For small anterior and broken down teeth or a similar

assortment

- Temporary filling materials and Intracanal Medicaments.

-Weine.

ACCESS CAVITY PREPARATION FOR VARIOUS TEETH:

Because internal anatomy dictates the access shape, the first step in

preparing an access is visualization of the location of the pulp spaces.

Buccolingual angulations and coronal anatomy are judged visually.

Cervical anatomy can be determined tactically using an explorer

under the sulcus to feel the cervical shape. Palpation along the

attached gingiva will help determine root location and direction.

Diagnostic radiograph in one straight and one in mesial or distal

angulation atleast. Will help to estimate pulp chamber position,

degree of calcification of pulp chamber and approximate canal length.

In difficult situations it is sometimes recommended that the initial

access be prepared without rubber dam in place.

Any restorative material impinging on straight line access should be

removed before the pulp chamber is accessed to prevent the lodging

of debris in the canal. Generally only material in the path of an ideal

access also caries.

Occasionally necessary to place an interim restoration, creating an

efficient seal and facilitating rubber dam placement.

1-2mm of occlusal adjustment of teeth may be done to establish a

more accurate point for measuring canal length and to reduce

postoperative pressure sensitivity.

Endodontic entry

Ingle Initial entrance through the enamel surface or restoration Round

end 702U carbide tissue bur / endodiamond stone.

With this instrument enamel, resin, ceramic or metal perforation is easily

accomplished and surface extension may be rapidly completed. Used always

with coolant to reduce heat.

But PFM : Tungsten carbide bur chatter severely, vibration results in

patient discomfort and tends to loosen the crown from luting cement so

diamond points are preferred.

After preparation of enamel / restorative penetration slow speed 3000

to 8000 contrangle handpeice is used.

Three round burs, 2, 4 and 6 - two lengths: regular 9mm, surgical 14mm.

It is used along long access for drop and also for removal of root of

the pulp chamber.

No. 2 Mandibular anterior, maximum premolars

No. 4 Maxillary anterior, mandibular premolars, adult molars.

No. 6 Molars with large pulp chambers.

After removal of roof again high speed fissure bur is used to finish

and slope side walls.

High speed burs should not be used to penetrate into / enlarge pulp

chamber unless operator is skilled in endodontic preparation as it reduces

tactile sense.

Weine - access cavity preparation begun by using tapered fissure bur

tungsten carbide 701 or 558. Once entered the pulp chamber then safe tip

tissue bur is used to enlarge the access.

Cohen (VII Edition) - Initial round bur for entry i.e. bur drop then switch on

to tapered tissue bur for preparation of side walls.

a) Endodontic preparation for maxillary anterior teeth.

Entrance is always gained through the exact center in the lingual

surface of anterior teeth.

Initial entrance prepared with round point tapering tissue bur

accelerated speed contrangle handpeice operated at right angle to the

long axis of the tooth. Only enamel is penetrated at this time.

Convenience extension towards the incisal continues the initial

penetrating cavity preparation. Maintain the point of the bur in the

central cavity and rotate the handpeice towards the incisal so that bur

parallels the long axis of the tooth. Enamel and dentin are beveled

toward the incisal.

Preliminary cavity outline is funneled and fanned incisally with a

fissure bur. Enamel has a short bevel towards the incisal, and a nest

is prepared in the dentin to receive the round bur to be used for

penetration.

Surgical length No.2 or 4 round bur in a slow speed contrangle

handpeice is used to penetrate the pulp chamber bur is operated

nearly parallel to the long axis of the tooth.

Then round bur is used inside the chamber to outside to remove the

lingual and labial walls of the pulp chamber. The resulting cavity is

smooth, continuous and flowing from cavity margin to canal orifice.

Then lingual shoulder is removed with round or long, tapering

diamond point.

Occasionally No. 1 or 2 round bur must be used laterally and incisally

to eliminate pulp horn debris and bacteria preventing future

discoloration.

Final preparation relates to internal anatomy of the chamber.

In young tooth with large pulp large triangular internal anatomy

(Same type access which allows through cleansing as well as passage

of large instrument).

In adult teeth chamber ovoid in shape due to secondary dentin

deposition.

Further the pulp has receded; the more difficult it is to reach to this depth

with a round bur. Therefore, when the radiograph reveals advanced pulpal

recession, convenience extension must be advanced further incisally to

allow the bur shaft and instruments to operate in central axis.

Final preparation with the reamer in place. The instrument shaft clears

the incisal cavity margin and reduces lingual shoulder allowing an

unrestrained approach to the apical third of the canal.

Endodontic preparation for maxillary anterior teeth

Maxillary Central incisor:

Pulp anatomy and coronal preparation: Pulp chamber of the maxillary

central incisor is located in the center of the crown equidistant from

the dentinal walls; it is broad mesiodistally, with its broadest part

incisally.

3 pulp horns that correspond to the developmental mamelons in

young tooth.

Chamber is ovoid mesiodistally.

Labio-lingual radiograph.

- 20 mesial-axial inclination of the tooth

- Apical distal curvature 8% of the time.

Distal view

- Presence of lingual shoulder where chamber and canal join.

- 290 lingual-axial angulation of the tooth.

Cross section at 3 levels Root canal is broad labiopalatally, large and

simple in outline, conical in shape and centrally located.

1) Cervical

Ovoid Mesiodistally

2) Midroot ovoid

3) Apical third round

Large triangular tunnel-shaped coronal preparation is necessary to

adequately debride the chamber of all pulp remnants.

Adult incisor: Pulp recession.

Narrow labio-lingual width of pulp.

Operator should recognize:

- Small orifice difficult to find.

- Careful alignment of bur to prevent gouging

Cross-section

Cervical - slightly ovoid. Becomes progressively more round.

Midroot slightly ovoid to round.

Apical III round.

Adult cavity preparation is narrow in M-D width but almost as

extensive in the incisogingival direction as preparation in a young

tooth.

Kasahara et al studied 510 maxillary central incisors to determine

thickness and curvature of the root canal and locations of the canals.

Data revealed that over 60% of the specimens showed accessory

canals and apical foramen was located apart from the apex in 45% of

the teeth.

Access cavity - maxillary central incisor

Maxillary Lateral incisor:

Pulp chamber: Shape is similar to maxillary central incisor but smaller.

Only 2 pulp horns corresponding to developmental mamelons.

Labiolingual radiograph:

- Apical distal curvature 53% of time..

- 160 mesial axial inclination of the tooth

Distal view

- Lingual shoulder.

- 290 lingual axial angulation of tooth.

Root and root canal: configuration of root canal is conical, it has a finer

diameter than maxillary central incisor and occasionally, may have a fine

constriction in its course towards the apex.

Cross sections:

Cervical - Ovoid labiopalataly.

Mid root ovoid

Apical III round

Large triangular funnel shaped coronal preparation is necessary to

adequately debride the chamber of all pulpal remnants.

Adult incisor pulp recession.

Marrow labiolingual width of the pulp

Operator should recognize:

Small orifice difficult to find

Axial inclination of root careful orientation and alignment. A Cork

Screw curve to the distal and lingual complicates preparation of the

apical III of the canal.

Cross section: Ovoid, Ovoid to round, and round

Ovoid funnel shaped coronal preparation should be only slightly

skewed toward the mesial to present better access to the apical distal.

Good to have extensive bevel toward the incisal to carry preparation

nearer central axis, allowing better access to the apical III.

Apical foramen is centrally located in the anatomic apex 22% of case

and apical delta 3% of cases.

Developmental anomalies:

Dens invaginatus

Peg lateral

Talons Cusp.

Access cavity -- maxillary lateral incisor

Require modifications in the

access openings

Maxillary cuspid:

Pulp chamber is largest of any single rooted teeth labiopalatally. The

chamber is triangular in shape, with the apex toward the single cusp and a

broad base in the cervical III of the crown. Mesiodistally it is narrow,

sometimes resembling a flame.

Only one pulp horn.

Chamber ovoid in cross section with greatest diameter labiopalatally

Division between pulp chamber and root canal indistinct.

Lingual view:

- Apical distal curvature 32%.

- 60 distal axial inclination of teeth.

Distal view:

Labial shoulder just below the cervical

Marrow canal in apical III

210 lingual axial angulation of tooth.

Root: larger than maxillary incisor. Wider labiopalatally than mesiodistally.

Cervical ovoid

Midroot ovoid

Apical round

Preparation Extensive ovoid, funnel shaped coronal preparation is

necessary to adequately debride the chamber of all pulpal remnants.

Long beveled extension towards the incisal.

Adult-tooth and view Pulp recession.

Narrow labiolingual width.

Operator recognize

Small canal orifice

Apical labial curvature

Distolingual inclination of the root calls for careful orientation and

alignment of the bur to prevent gouging

.

Cross sections at 3 levels:

1) Cervical slightly ovoid

2) Middle canal smaller but ovoid

3) Apical round

Preparation Ovoid funnel shaped preparation must be nearly as large as

for a young tooth.

The apical foramen is centrally located in the anatomic apex in 14% of cases

and apical delta present in 3% of times.

Fenestration is occasional finding. Accurate length determination is critical.

Another ramification of this fenestration is a slight, permanent apical

pressure sensitivity that occasionally occurs after endodontic therapy.

Access cavity -- maxillary canine

Maxillary anterior teeth:

Errors:

a) Perforation at the labiocervical caused by failure to complete

convenience extension toward the incisal, prior to the entrance

of the shaft of the bur.

b) Gouging of the labial wall failure to recognize 290 lingual

axial angulation of the tooth or distal wall failure to recognize

160 mesial-axial inclination of the tooth.

c) Pear shaped preparation of the apical canal caused by failure to

complete convenience extension. The shaft of the instrument

rides on the cavity Margin and lingual shoulder.

d) Discoloration of the crown : Failure to remove pulp debris

access with no incisal extension

e) Ledge formation at apical distal curve caused by using an

uncurved instrument too large for the canal. The cavity is

adequate.

f) Perforation at the apical distal curve using box large an

instrument through an inadequate preparation placed too far

gingivally

g) Ledge, formation at the apical labial curve caused by failure to

complete the convenience extension. The shaft of the

instrument rides on the cavity margin and shoulder.

b) Endodontic preparation of mandibular anterior teeth:

Lingual surface at center

Similar to upper anterior and initial entrance is by 701U tapering

fissure bur.

Pulp chamber penetrated by No.2 round bur surgical length inside to

outside and shift of bur should be parallel to long axis of the tooth

Lingual shoulder is removed with fine tapered diamond point

No.1 round bur to eliminate pulp horn debris.

Final preparation

Young tooth - triangular

In adult tooth pulp receded. So, convenience extension must be advanced

further incisally to allow bur shaft to operate in the central axis.

Final preparation should have unstrained approach to the apical III of

canal.

Access cavity preparation for mandibular anterior teeth

Mandibular central and lateral incisor:

Pulp anatomy and coronal preparation:

Central pulp chamber, small and flat mesiodistally, 3 distinct pulp horns

present in a recently erupted tooth but disappear early in life because of

constant masticatory stimulus.

Labiolingually

Wide and ovoid in cross section.

Lateral - similar to central but larger dimensions.

Lingual view

Slight apical distal curvature of the canal 23% of time.

Mesial axial inclination of tooth Central incisor -20 Lateral incisor -17

0

Distal view Lingual shoulder

200 lingual axial angulation of the tooth

Root canal: Central incisor- Root which is flat and narrow mesiodistally

but wide labiolingual.

Lateral incisor- Root configuration same but larger than CI.

Cross sections:

cervical - ovoid

Midroot ovoid

Apically - round

Preparation- young, large triangular, funnel shaped necessary to debride

the chamber of all the pulp remnants.

Adult- pulp recession, reduced size of lingual shoulder and unsuspected

presence of bifurcation of pulp into the labial and lingual canals nearly 30%

of the time.

Operator recognize- smaller canal orifice difficult to find, axial inclination

requires careful exploration.

Cross sections

Cervical III- ovoid

Midroot 2 canal, round

Apical - round.

Important that all mandibular anterior teeth be explored to both labial and

lingual for possibility of two canals

Adult -

Preparation is ovoid funnel shaped marrow in the M-D width but is

extensive in the incisogingival direction. Incisal edge may be invaded, will

allow better access to both canals and curved apical III.

Mandibular incisor roots and canal extensively studied by Rankine-Wilson

and Henry.

60% - type I They further stated that

35% - type II short squatty crowns and blunted

5% - type III roots, usually has divided or split canal.

Development depressions are found on both mesial and distal surfaces

of the root. Decrease the M-D dimension so preparation should be

extremely precise.

In terms of difficultly these teeth come right behind the molars and

the multicanaled mandibular bicuspid 40% time 2 canal

Because of their proximity, it is vertically impossible to radiograph

these teeth from a sufficient angle to know in advance that 2 canals

are present. It tooth is decoronized then the two canals can be

discovered.

Mandibular Central incisor has

Lateral canals - 20%

Apical delta - 5%

Apical foramen situated centrally in root - 25%.

Mandibular Lateral incisor has

Lateral canal - 18%,

Apical delta - 6%

Apical foramen in center of radiographic apex - 20%.

Access cavity for mandibular incisors

Mandibular cuspid:

Pulp chamber resembles maxillary cuspid but smaller in dimension.

Chamber is narrow mesiodistally. When viewed buccolingually, the

chamber tapers to a point in the incisal third of the crown, but it is wide in

the cervical area.

One pulp horn

Cross section of chamber is ovoid

Lingual view:

- Narrow M-D width of the pulp

- Apical distal curvature - 20%

- Mesial axial inclination of tooth - 130

Distal view:

- Narrow canal in apical III

- Apical labial curvature - 7%

- Lingual axial angulation of the tooth - 150

Root and root canals: generally has single root but may have two

Cross section

Cervical ovoid

Middle ovoid

Apical round

Preparation Extensive ovoid tunnel shaped canal preparation necessary

to adequately debride the chamber of all the pulp remnants.

Bevelled extension and towards incisal

Adult

Lingual - pulp recession.

Operator should recognize:

- Small canal orifice.

- Lingual axial in elevation gouging

Cross section - ovoid, ovoid and round.

Preparation - extensive ovoid funnel shaped and as young tooth. An apical

labial curve would call for extension incisally.

2 Canals - wider access

Lateral canal - 30%

Apical delta - 8%

Apical foramen located centrally - 30%.

Access cavity for mandibular canine

Mandibular anterior teeth - Errors in cavity preparation:

a) Gouging at the labiocervical caused by failure to complete

convenience extension toward incisal prior to entrance of the shaft of

the bur

b) Gouging of the labial wall - failure to recognize 200 lingual axial

angulation of tooth

c) Gouging of the distal wall - failure to recognize 170 mesial-axial

angulation of tooth.

d) Failure to explore, debride or fill the second canal caused by

inadequate incisogingival extension of the access cavity.

e) Discoloration - failure to remove pulp debris

f) Ledge formation caused by complete loss of control of the instrument.

c) Endodontic preparation of Maxillary premolar teeth:

Entrance always through occlusal surface of all posterior teeth. Initial

preparation is made parallel to the long axis of the tooth in the exact

center of the central groove. 701U tapering fissure bur in an

accelerated speed contra angle hand piece gold casting/virgin

enamel surface.

Regular length No.2 or No 4 round burs - used to open into pulp

chamber but will be felt to drop when the pulp chamber is reached. If

chamber is well calcified drop is not felt. Vertical penetration is made

until the contra angle handpeice rests against the occlusal surface.

Thus depth is approximately 9mm, the position of the floor of the

pulp chamber that lies at the cervical level. In removing the bur, the

orifice is widened buccolingually to twice the width of the bur to

allow room for exploration of canal orifices.

Working from inside to outside with round bur used at low speed to

extend the cavity buccolingually by removing the roof of the pulp

chamber.

Buccolingual extension and finish of the cavity walls completed with

701 U fissure bur at high speed.

Final preparation should provide unobstructed access to canal

orifices. Cavity walls should not impede complete authority over

enlarging instruments.

Outline form of final preparation: Buccolingual ovoid, reflecting the

anatomy of the pulp chamber and position of buccal and lingual canal

orifice. Further exploration at this time is imperative.

Access cavity preparation for maxillary premolar

Maxillary I premolar:

Pulp anatomy and canal preparation:

Pulp chamber is narrow mesiodistally 2 pulp horns under each cusp. Wide

buccopalatally and buccal pulp horn more prominent than the palatal in

young teeth. Roof of the pulp chamber is coronal to the cervical line. Floor

of pulp chamber is convex. Cross section of pulp chamber is wide and ovoid

in a buccolingual direction.

Buccal view:

- Presence of 2 pulp canals - generally straight

- 100 buccal axial inclination of the tooth.

Mesial view:

60 buccal axial angulation of the tooth.

Broad buccolingual dimension of the pulp.

Root and root canal:

Have 2 roots in 54.6% of cases. In 21.9% of the double rooted cases the

roots are separated, when s in 32.7% the roots are partially fused.

When 2 root canals are present:

The cervical III are ovoid, mid root almost round and apical III round

and small

Vertucci has stated when 2 canals are present in one root, the distance

between the orifices is a strong indicator of their ultimate relation

with each other. In order words, if the orifices are closer to each

other, the canals will merge short of the apex and if they are far apart,

will remain separate and distinct. This is more correct with

mandibular molar mesial root.

Many of these teeth have a concavity on the mesial, which make the

area below the pulp chamber laterally thin. This must be taken into

account when locating canals, opening the orifice of the canals and

during post build op procedures

Ovoid preparation and buccal and lingual walls smoothly flow into

orifices.

Adult:

- Pulp recession.

- Buccolingual width revealing the pulp to be ribbon shaped rather than

thread like

Operator recognize:

- Small orifices are found well to the buccal and lingual and are difficult to

locate

- Virtually always there will be 2 and occasionally 3 canals.

Cross section: narrow ovoid, round, round

- Ovoid preparation must be more extensive in the buccolingual

direction because of the parallel canals.

Access cavity preparation for maxillary I premolar

Maxillary II premolar:

Pulp anatomy and canal preparation:

Pulp chamber narrow mesiodistally wider buccopalatally than maxillary I

premolar with 2 pulp horns.

Root of the pulp chamber is similar to I premolar but floor is deeper if 2

canals are present.

In cross section pulp chamber is narrow, ovoid-shape.

Buccal view:

- Apical distal curvature - 34% of time

- 190 distal axial inclination of the tooth.

Mesial view:

- Broad B-L width revealing the pulp to be ribbon shaped.

- 90 lingual axial inclination of the tooth.

Root and root canals

Have only a single root 90.3% of patients. Only 2% have 2 well developed

roots where as 77% have 2 roots that are partially fused.

Weine 10% of time type IV canals.

Cross section-

- Cervical - very wide in B-L direction. Canal orifice is directly in the centre

of the tooth.

- Midroot - ovoid

- Apical - round. Preparation is ovoid. Allows Debridement of the entire

pulp chamber and tunnels down to the ovoid midcanal.

Adult view:

- Pulp recession thread like appearance.

- B-L width revealing canal pulp - ribbon shaped.

Operator recognize: small canal orifice deeply placed in the root and will

be difficult to locate

Cross section: Narrow ovoid, round, round

If Bayonet curve is present then preparation mesial of the occlusal

surface with a depth of penetration skewed toward the bayonet

curvature. Skewing the cavity allows an unstrained approach to the

first curve.

Apical foramen is centrally located in 12% of the cases and an apical

delta is present only in 3.2% of cases.

Errors in cavity preparation:

a) Underextended - exposing only pulp horns white color of the roof of

the chamber is a clue of the shallow cavity.

b) Over extended preparation.

c) Perforation mesiocervical indentation. Failure to observe distal axial

inclination and mesial groove.

d) Faulty alignment of the access cavity through full veneer restoration

placed to straighten the crown of a rotated tooth.

e) Broken instrument twisted off in a cross over canal. This frequent

occurrence may be obviated by extending the internal preparation to

straighten the canals.

f) Failure to explore, debride and obturate II or III canals.

Access cavity preparation for maxillary II premolar

d) endodontic preparation of Mandibular premolar teeth:

Initial preparation is made in the exact center of the central groove

with bur directed parallel to the long axis of the tooth. 702U tapered

fissure in an accelerated speed is used to the depth of the dentin.

A regular length No.4 for drop rest similar to upper premolar

Final ovoid preparation is a tapered funnel from the occlusal to the

canal, providing unobstructed access to the canal.

Buccolingual outline form reflects the anatomy of the pulp chamber

and position of the centrally located canal.

Outline form of the final preparation will be identical for both newly

erupted and adult teeth.

Access cavity preparation for mandibular premolars

Mandibular I premolar:

Pulp anatomy and coronal preparation:

Pulp chamber:

M-D width of the pulp chamber is narrow buccolingually; the pulp

chamber is wide with a prominent buccal pulp horn that extends

under a well developed buccal cusp.

In young tooth small lingual pulp horn that may disappear with age

and give the pulp chamber an appearance smaller to that of the

mandibular cuspid

Crown of mandibular I premolar about 300 lingual tilt.

Cross section- chamber is ovoid with greater diameter buccolingually.

Buccal view:

Narrow M-D width of the pulp

140 distal axial inclination of the root

Relatively straight canal

Mesial view:

Broad buccolingual extent of the pulp

Apical buccal curvature 2%

100 lingual axial inclination of the root.

Type IV canal system is present in significant number of cases

ranging from 15-25%

Roots are only slightly larger in circumference and generally shorter

than the root of the adjacent cuspid

Cross section:

Cervical - pulp enormous and wide in B-L dimension- ovoid.

Midroot - ovoid

Apical - round

Preparation - ovoid to allow Debridement of entire pulp chamber and large

enough B-L.

Adult:

- pulp resection and thread like

- Ribbon shaped coronal pulp.

Operator recognize: small orifices are difficult to locate and presence of a

bifurcated canal is determined only by exploration with a fine curved file.

Cross section: narrow ovoid, round, round.

Lateral canals are present 64.3% of cases.

Apical deltas are found 5.7%.

Apical foramen is centrally located in only 15% of the teeth.

Anomalies: Bifurcation and trifurcation of roots.

Access cavity preparation for mandibular I premolar

Mandibular II premolar:

Pulp chamber: Similar to I premolar except the lingual horn is more

prominent under a well developed lingual cusp.

Buccal view:

Apical distal curvature 40% of time

100 distal axial inclination of the root

Mesial view: 340 buccal axial inclination of the root

Root and root canals: Root has greater girth and is wider buccolingually

than that of the mandibular I premolar.

Cross section:

Cervical: B-L wide, ovoid; ovoid; root.

Preparation- ovoid, coronal funnel shaped preparation down to ovoid mid

canal.

Adult - pulp recession and buccolingual ribbon shaped pulp

Section - Narrow ovoid, less ovoid and round

Lateral canals are present 48.3% of time,

Apical delta 3.4%.

Apical foramen is centrally located in only 16.1% of these teeth.

Errors in cavity preparation:

a) Perforation at distogingival caused by failure to recognize that

premolar has a tilt towards distal.

b) Bifurcation of a canal completely missed. Caused by failure to

adequately explore the canal with curved instrument.

c) Perforation of apical curvature caused by failure to recognize by

exploration of buccal curvature.

Access cavity preparation for mandibular II premolar

e) Endodontic preparation of maxillary molar teeth:

Entrance through occlusal surface. Initial penetration is made in the

exact center of the mesial pit, with the bur directed toward the lingual.

The 702U tapering fissure bur in speed - for virgin enamel and gold

casting. Amalgam filling 4 - 6 round burs.

As per size of chamber No. 4 to open into pulp chamber. The bur

should be directed toward the orifice of the palatal canal or toward the

M-B canal orifice where the greatest space in the chamber exists.

Drop will be felt if pulp chamber is reached. (Contra angle rest -

9mm).

Work inside out, back toward the buccal, the bur removes enough

root of the pulp chamber for the exploration.

An endodontic explorer is used to locate orifices of the palatal, MB

and DB canals. Tension of the explorer against the walls of

preparation will indicate the amount and direction of extension

necessary. Orifices of canal form the perimeter of preparation. Special

care should be taken to explore II canal in MB root.

Work inside out to remove roof of the pulp chamber. Final finishing

and funneling with 702U fissure or tapered diamond points at

increased speed.

Further preparation can be eased for access by leaving the entire

preparation toward the buccal for; all instruments are introduced from

the buccal.

Preparation extends almost to the height of the buccal cusps. The

walls are perfectly smooth and orifices are located at the exact pulp

axial angles of the cavity floor.

Outline form reflects anatomy of pulp chamber with base towards

buccal, apex to lingual and cavity is entirely with in mesial half of the

tooth and need not invade the transverse ridge but is extensive enough

buccal to lingual, to allow positioning of instrument and filling

material.

Access cavity preparation for maxillary molars

Maxillary I molar:

Pulp chamber:

Largest in dental arch with 4 pulp horns MB, DB, MP and DP.

The arrangement of 4 pulp horn gives the pulpal root a rhomboidal

shape in cross section.

The four walls forming the roof converge toward the floor where the

lingual wall almost disappears; the floor of the pulp chamber thus has

a triangular form in cross section.

The orifices of the root canals are located in the 3 angles of the floor.

Anatomic dark lines in the floor of pulp chamber connect the orifices.

Palatal orifice is largest and is round / oval in shape.

MB orifice is under MB cusp, long buccopalatally and may have

depression at palatal end in which the orifice of a fourth canal may be

present.

DB orifice: Is located slightly distal and palatal to the MB orifice.

Floor of the pulp chamber is in cervical III and roof in the cervical III of the

crown.

Buccal view: 2 canals in MB root

Mesial view: Apical buccal curvature of palatal root 55% of time.

Has 3 roots.

MB root:

Broad in B-P direction canal narrowest of 3, flattered in a M-D

direction in the orifice but round in the apical III.

Lateral canal 1% of cases,

Apical delta 8%.

Apical foramen located centrally in only 14% of cases.

DB root:

Small and more or less round in shape, canal is narrow tapering canal

ending in a small round canal in apical III.

Lateral canals - 36%,

Apical delta 2%.

Apical foramen centrally located 19%.

Palatal root:

Largest diameter and largest root

Canal is ovoid mesiodistally and tapers towards apex when it

becomes a small, round canal.

Lateral canals present in 40%,

Deltas - 4%,

Apical foramen centrally located in only 18%.

Lateral canals in trifurcation - 18%

Triangular outline form with base toward the buccal and apex toward

the lingual with the orifice positioned at each angle of the triangle.

Both buccal and lingual walls slope buccally, mesial and distal walls

funnel slightly outward. The cavity is entirely within the mesial half

of the tooth. The orifice to an extra middle mesial canal may be found

in the groove near the MB canal.

Adult:

Pulp recession and thread like pulp.

A chamber constricted from secondary dentin formation.

Since the buccal roots diverge as they leave the crown, the canals

form a V shape and approach each other near the floor of the

chamber. As reparative dentin fills in the chamber and canal

diameter, the orifices are found further up their respective roots and

thus are further apart.

Weine Quadrilateral access with rounded comer to get adequate

debridement of palatal canal.

To uncover 4th canal safe tipped bur is moved form MB orifice

toward the palatal canal a distance of 2-5 mm.

Root:

MB - greatest difficult.

When viewed from buccal - MB canal curves first to mesial as it

leaves the floor of the chamber and then to the distal and also curves

initially towards buccal and then to the palatal.

Distobuccal and Mesiobuccal give cow horn appearance.

Good to give distal angulation.

Maxillary II molar:

Pulp chamber: similar to maxillary I molar except narrower mesiodistally.

Because of narrow dimension, roof of the pulp chamber is more rhomboidal

in cross section. Floor of Pulp chamber is obtuse in cross section. MB and

DB canals are close together and may appear to have a common opening.

Sometimes all 3 canal orifice may almost be in straight line.

View: similar to I molar

Root and root canal:

3 roots closely grouped. Because of this close grouping, the buccal

roots may fuse and occasionally all 3 roots fuse to form a single

conical root - 46%.

16% of roots are foramina centrally located.

3% apical delta.

Outline form: triangular form is flattened. DB orifice is nearer to the

center of the cavity floor. The entire preparation sharply slopes to the buccal

and is extensive enough to allow positioning of instruments.

Adult: pulp recessed and thread like. Ovoid outline form

Two rooted maxillary molar - 10% of cases.

Maxillary III molar:

Resemble II molar

Pulp chamber: Can be similar to that of maxillary II molar with 3 canal

orifices, but it may also have an odd-shaped chamber with 4 or 5 root canal

orifices or a conical chamber with only one root canal.

Root and root canals:

Variations

- 3 well developed roots

- Fused roots

- One conical root

- 4/5 independent root.

- Root canals vary from 4/5 in number

Access opening similar to II molar:

Careful examination of root morphology is recommended before

initiating treatment. Radicular anatomy is completely unpredictable and is

advisable to explore the root canal morphology before promising success.

Errors in cavity preparation:

a) Under extended : Only pulp horns are Nicked

b) Over extended : Badly gouged

c) Perforation: Using surgical length but failing to realize narrow pulp

chamber has been passed.

d) Inadequate vertical preparation: related to failure to recognize severe

buccal inclination of tooth.

e) Disoriented occlusal outline: A faulty cavity has been prepared in full

crown, which was placed to straighten a rotated molar. Palpating for

MB root prominence would reveal the severity of the rotation.

f) Ledge: Large straight instrument in curved canals.

g) Perforation: palatal root as buccal curve is present in apical III.

f) Endodontic preparation of mandibular molar teeth:

Initial preparation is made in the exact center of the mesial pit, with

the bur directed towards the distal.

The 702U tapering fissure bur in an accelerated speed for gold casting

/ virgin enamel upto depth of dentin

No 4 round bur for amalgam

As per size of pulp chamber, No. 4 / No. 6 round bur to open into

pulp chamber. The bur is directed towards the orifice of MB or distal

canal, when the greatest space in the chamber exists

Drop is felt when pulp chamber is reached.

Well calcified: Contra angle handpeice rest.

9 mm usual position of the floor of pulp chamber.

Working inside out, back toward the mesial, the bur removes enough

roof of the pulp chamber for exploration

Endodontic explorer to explore orifice and special care must be

taken to explore for an additional canal in the distal root. The distal

canal should form a triangle with 2 mesial canals. If it is asymmetric,

always look for fourth canal (29% of the time).

Final finishing and funneling of cavity walls is completed with 702U

fissure bur or diamond point at speed.

Improve ease of access by leaning the entire preparation toward the

mesial, for all instrument is introduced from mesial. Notice that

cavity outline extends to height of the mesial cusps. Walls are

perfectly smooth and the orifice located at the exact pulpal axial angle

of the cavity floor.

Square outline form. Both mesial and distal walls slope mesially.

Cavity is primarily with in the mesial root of the tooth. Further

exploration should determine if a fourth canal can be found in the

distal. If so the outline is extended in that direction and an orifice will

be positioned at each angle of the square.

Access cavity preparation for mandibular molars

Mandibular I molar:

Pulp anatomy and coronal preparation:

Pulp chamber:

Roof rectangular in shape. Mesial wall straight, distal wall round

and buccal and lingual walls converge to meet the mesial and distal

walls and to form a rhomboidal floor.

4 pulp horns

Root located in cervical III of crown just above canine and floor

located in cervical III of root.

3 distinct orifices:

MB orifice under MB cusp, ML orifice is located in a depression

formed by the mesial and lingual wells.

Distal orifice oval/kidney shaped with widest diameter

buccolingually.

If 2 canals are present then they are eccentrically placed. Further if

file No. 25 cannot penetrate distal canal, then 2 canals should be

suspected

Buccal View: curvature of mesial root 86% of time and distal axial

inclination of the tooth

Mesial View: 580 buccal angulation of the roots.

Roots and root canals:

Usual Roots

Mesial and distal both roots are wide and flat buccolingually with a

depression in the middle of the root buccolingually

Accentuated in mesial root.

Third root 5.3%.

MB canal curves first curves towards the mesial and then it gradually

turns towards distal.

MB canal first curves to the buccal and then to lingual. Coronal

portion of the ML canal is straighter and then in the middle III begins

a more gradual buccal curve therefore from this view canals diverge

coronally but then converge apically.

Cross section

Cervical: ovoid and enormous pulp

Midroot: Canals are ovoid and severe indentation on the distal surface of

the mesial root brings the canal within 1.5 mm of the external surface, an

area generally susceptible to strip perforation.

Apical III: round tapered preparation

General outline is trapezoidal with rounded comers. The shortest side

is to the distal aspect, and the mesial side is slightly longer. Buccal

and lingual walls are approximately of same length and taper toward

each other distally.

Some have suggested triangular shaped entry. However, the distal

canal is kidney shaped in most cases, with the greatest width

buccolingually. Also, two canals exiting the floor of the chamber are

found in distal root approx 30% of time. Attempting to enlarge the

single large canal or to locate the possibly present second canal

requires such wider access than that afforded at the apex of a triangle.

Adult: pulp recession, thread like

Cross section: oral, round, round

Mandibular II molar:

Pulp chamber is smaller than mandibular I molar and root canal orifices are

smaller and closer together.

Buccal view: mesial curvature of distal root 10%

Mesial View: 520 buccal axial inclination of the roots.

Roots and root canals:

Only one mesial canal does occur in II molar. This bicanalled tooth

access is trapezoid narrowed to the mesial to be move rectangular

27%

Teeth with

2 roots 71%

1 root 27%

3 root 2%

May have C shaped canal first described by Cooke and Cox, 1979 - 8%

[predominantly in mandibular II molar].

From occlusal surface it appears that the orifices of the canal are not

individually distinct but that there is a C shaped trough on the floor of pulp

chamber. C shaped configuration refers to a continuous slit between all the

canals so that the horizontal section through the root yields a space in the

shape of letter C.

Closed area of C may be towards buccal or lingual.

- If buccal Then canal is continuous from the MB to be ML around the

lingual to the DL to the DB.

- If lingual ML to the MB along the buccal to the DB to the DL and is

difficult to treatment.

Cross section: Ovoid, round, wound

- Strip perforation

Adult: Pulp recession, thread like

Access similar to mandibular I molar

Lateral Canals in mesial root - 49%. AD - 6%

Distal root 34%. AD - 7%

Lateral canals in furcation 11%

When a single apical foramen is present, it is centrally located in 19% of

cases in mesial root, 21% of cases in distal root.

Mandibular III Molar:

Pulp chamber: Anatomically resembles the pulp chamber of the

mandibular first and second molars. It is large and possesses many

anomalous configurations such as C shaped root canal orifices.

Judgment should be made as to the benefit derived from treatment of a third

molar balanced against its prognosis. In many cases the benefit is so

marginal that extraction is the best choice.

Root and root canals: Usually have two roots and 2 canals but occasionally

one root and one canal or 3 root and 3 canals. The roots are generally large

and short.

Access opening: Similar to mandibular I and II molars, with the variations

that anatomic structure dictates.

Anatomic relation in situ- root may project onto lingual plate of mandible

and apex of the root is in close proximity to the mandibular canal.

Access cavity preparation and enlargement of orifice:

Er : YAG laser ablate enamel and dentin.

MODIFIED ACCESS CAVITY PREPARATION:

Buccal access in case of lower incisor especially in the case of

crowding or for structural reasons and it may have less compromise of the

straight line principle.

If worn incisor: Access cavity positioned directly along the long axis

of the tooth Decision should be based on ease of access and conservation

of as much tooth structure as possible.

1) Access through full veneer crowns:

Crowns are constructed with the occlusal relationship of the opposing

tooth as a primary consideration. A cast crown may be made in any shape,

diameter, height or angle; this cast crown alteration can destroy the visual

relation to the true long axis. Careful study of preoperative radiograph

identifies most of these situations.

Should be done with use of coolants as friction generated heat can

damage adjacent soft tissues including the PDL.

Frequent irrigation to remove small slivers can cause large

obstruction in the fine canal system.

Access without rubber dam in place this allow correct angulation of

the bur, as the operator is not distracted by the angulation of the crown.

Access when anatomic crown is missing Better to palpate for root

anatomy to determine root angulation for correct bur angulation.

2) Achieving access through complex restorations:

Ideal access can only be achieved by total removal of all restorative

material. In the case of gold crowns and porcelain fused to metal crowns,

financial constraints may influence the choice for gaining access. Under

such condition patient should be informed of all risk.

3) Methods of locating calcified canals:

Pulp stone and irritation dentin may make the location of root canal

orifices difficult. Special tips of ultrasonic Handpeices are invaluable in this

situation as they allow the precise removal of dentine from the pulp floor

with minimal risk of perforation. In absence pointed ultrasonic sealer tip.

A solution of 17% EDTA is excellent for cleaning floor of the

chamber and let it stand for 1-2 min. Dentin chips and other debris can then

be washed away with a syringe of NaOCl.

4) Sclerosed canals:

Illumination and magnification are vital. There is no rapid technique

in dealing with calcified cases. Painstaking removal of small amounts of

dentin has proven to be safest approach.

Loupes, microscope and thorough knowledge

Chelating agents like EDTA should not be used as it softens dentin

indiscriminately and may lead to formation of false canal or

perforation.

Dentin removed with ultrasonic tips CT4 design or long shank low

speed no. 2 round bur. Take frequent radiograph with ultrasonic tip /

drill in place to see its relation with root canal.

Endodontic explore DG 16. Examining instrument and chipping tool

often used to flake away calcified dentin. A slight tugback in the area

of canal orifice often signals the presence of a canal.

At first indication of space, the smallest instrument No. 6 or No. 8 file

should be introduced. Gently passive both apical and rotational,

further access to canal orifice widened by G.G bur.

If pulp chamber filled with irrigates, bubbles can occasionally be seen

appearing from the canal orifice or dyes and Iodine in Potassium

iodide or methylene blue for location of canal orifices.

5) Location of extra canals:

MB 2 in maxillary molars 60%

Location of the orifice can be made by visualizing a point at the intersection

between a line running from the MB to the palatal canal and a perpendicular

from DB canal. There is often an isthmus between the main MB canal and

the second MB this can be traced until the orifice is located.

Four canals in mandibular molar 38%

If distal canal is not in middle of the tooth than a second distal canal should

be suspected and canals are often equidistant from midline.

Two canals in mandibular incisor 41%

To gain proper access to both canals - access has to be extended very near to

the incisal edge.

Two canals in mandibular premolar 11%

There are rarely two orifices. The lingual canal normally projects from the

hall of the main buccal canal at an acute angle. It can usually be located by

running a file with a sharp bend in the tip along the long wall of the canal.

6) C shaped mandibular molar:

2 types

1) Those with single, ribbon like C shaped canal from orifice to apex and

2) Those with 3 or more distinct canals below the usual C shaped orifice.

Fortunately C shaped molars with a single swath of canal are the

exception rather than the rule.

Increases common in Asians than in Caucasians

China 31.5% incidence Hadad, Mehma and Ovnsi found a 19.1% in

Lebanese subjects.

ANATOMY OF PULP CHAMBER FLOOR:

A study has been done by Paul Krasner and Henry J Rankow where they

used 500 extracted maxillary and mandibular anterior premolar and molars.

400 teeth were cut off horizontally at level of CEJ, 50 teeth sectioned

buccolingually through crown and roots, 50 teeth sectioned mesiodistally

through crown and roots.

Following observations were noted:

1) Pulp chamber has always in the center of the tooth at the level

of CEJ

2) Walls of the pulp chamber were always concentric to the

external surface of the crown at the level of the CEJ.

3) The distance from the external surface of the clinical crown to

the wall of the pulp chamber was the same through out the

circumference of tooth at the level of the CEJ.

These observations were consistent enough that several laws could be

formulated.

Law of centrality: The floor of the pulp chamber is always located in the

center of the tooth at the level of CEJ.

Law of concentricity: The walls of the pulp chamber are always concentric

to the external surface of the tooth at the level of the CEJ.

Law of CEJ: CEJ is most consistent, repeatable landmark for locating the

position of the pulp chamber.

Following observations were noted relative to all the teeth except maxillary

molars.

1) If a line is drawn in a mesial-distal direction across the center

of the floor of the pulp chamber, the orifices of the canals on

either side of the line are equidistant.

2) If a line is drawn in mesial distal direction across the center of

the floor of the pulp chamber, the orifices of the canals on

either side are perpendicular to it.

Several laws regarding pulp chamber floor that can be proposed.

Law of symmetry 1: Except for maxillary molars, the orifices of the canals

are equidistant from a line drawn in a mesial distal direction through the

pulp chamber floor.

Law of symmetry 2: Except for the maxillary molars, the orifices of the

canals lie on a line perpendicular to a line drawn in mesial distal direction

across the center of the floor of the pulp chamber.

Relationship on the pulp chamber floor:

1) Floor of pulp chamber is always a darker color than the

surrounding dentinal walls.

2) This color difference creates a distinct junction where the walls

and the floor of the pulp chamber meets.

3) The orifices of the root canals are always located at the junction

of the walls and floor.

4) The orifices of the root canals are located at the angles in the

floor wall junction.

5) The orifice lay at the terminus of developmental root fusion lines

(DRFL)

6) DRFL are darker than the floor color

7) Reparative dentin or calcification are lighter than pulp chamber

floor and often obscure it and the orifices

Law of color change: Color of the pulp chamber floor is always darker than

the walls.

Law of orifice location 1: The orifices of the root canals are always located

at the junction of the walls and floor.

Law of orifice location 2: The orifices of the root canals are always located

at the angles formed at the junction of the walls and the floor

Law of orifice location 3: The orifice of the root canals are located at the

termination of developmental root fusion line.

CONCLUSION

Thus the hard tissue repository of the human dental pulp takes on many

configurations that must be understood before the treatment can begin.

Detailed knowledge of anatomy of the teeth, armamentarium and

knowledge regarding access cavity preparation are critical for the success of

root canal therapy.

REFERENCES

1) Endodontics.Ingle,Bakland V edition.

2) Endodontic theraphy.Weine VI edition

3) Pathways of pulp.Cohen VIII edition.

4) Endodntics. Stalk Walker & Gulabivala III edition.

5) Advanced endodontics for clinicians.Jacob Daniel

6) Endodontics problems solving in clinical practice Pittford.