PERIAPEX AND ITS SIGNIFICANCE

Seminar by

Postgraduate Student

DEPARTMENT OF CONSERVATIVE DENTISTRY &

ENDODONTICS

CHENNAI

CONTENTS

INTRODUCTION 1

DEVELOPMENT OF ROOT 2

ROOT LENGTH AND APICAL CLOSURE 4

APICAL FORAMEN ANATOMY 5

LATERAL CANALS 8

ACCESSORY CANALS 10

APICAL PULP TISSUE 12

APICAL DENTIN 14

REASON FOR ROOT CURVATURE 15

ROOT RESORPTION 15

CHANGE OF ANATOMY OF ROOT APEX 16

AGE CHANGES AT APEX 17

RADIOGRAPHIC ASSESMENT OF APICAL THIRD 18

PREPARATION OF APICAL THIRD 21

APEXIFICATION 26

DENTIN CHIP APICAL FILLING 28

PERIAPICAL SURGERY AND APEX 30

RECENT ADAVANCES 34

CONCLUSION 36

INTRODUCTION

Achievement of a perfect seal at the apex using an inert filling

material is the ultimate goal for every endodontist. The crux of

endodontics revolves around the efficient and effective manipulation and

obturation of the apical third of the root canal. The importance of a

thorough cleaning and hermetic filling of the apical part of the canal for

successful healing of the periapex was highlighted analogically as early

as 1939 itself, by Kronfeld. He has equated the microorganisms in the

root canal to an army in the “mountains” which enters the ‘plains’

through the foramina or ‘the mountain pass’. As the bacteria enters in

small numbers, they are destroyed by the ‘army’ of leucocytes is

maintained at the ‘front’ to counter the attack. A thorough cleaning and

filling would make the maintenance of the army unnecessary allowing the

environment to return to normality.

Variations in external morphological features of crowns of teeth

occur with variations in shape and size of head. External morphological

features vary from person to person. In the same way internal

morphology of crown and root also varies. Among these, the anatomy of

the root apex, its morphological variations and treatment are technical

challenges for the endodontist.

Much of the knowledge of root apex is based on exhaustive work

of Hess who studied 3000 permanent teeth and showed minute details

like extensions, ramifications, branching as well as size, shape and

number of root canals in different teeth.

Fracture of the apical third, resorption, weeping canals, immature

foramina are some of the areas which continue to be under constant

research.

DEVELOPMENT OF ROOT

On completion of formation of crown, i.e. once the enamel and

dentin has been formed till the cementoenamel junction, the inner and the

outer enamel epithelium proliferates downwards to form Hertwig’s

epithelial root sheath. This root sheath determines the size and shape of

the root of the tooth.

Root sheath takes a bend horizontally towards the dental papilla to

form epithelial diaphragm. This process partially encloses the dental

papilla and delineates the apical foramen. Soon the ectomesenchymal

cells of dental papilla present above the epithelial diaphragm starts

proliferating and root dentin deposition takes place. According to Orban,

the epithelial diaphragm i.e. future root apex will remain in place while

the tooth crown and supporting structures move occlusally. Once the

dentin is deposited to the entire length of the root, the HERS split to get

the cells of the dental sac in contact with the dentin. These cells of the

dental sac get differentiated into cementoblasts and starts laying down

cementum on radicular dentin.

Two kinds of cementum are laid down on the root. If the

cementoblasts retracts as cementum is laid down, it will be acellular

cementum. If cementoblasts do not retract and get surrounded by new

cementum the tissue formed will be cellular cementum and the trapped

cementoblasts will be called cementocytes.

Acellular cementum will be formed around the coronal and middle

third of root where as cellular cementum will be formed in the apical

third of the root with alternating layers of acellular cementum. This

incremental deposition of the cementum continues throughout the life of

the tooth and makes the layer of cementum on the apical third of the root

thicker than cervical third. This continued deposition of the cementum on

apical third maintains the length of the tooth constricts the apical foramen

and also deviates the apical foramen from the center of the apex.

The island of HERS which are left behind migrates towards the

dental sac. They remain in the periodontal ligament close to the

cementum. These cells are called cell rests of mallasez. They have the

potential to differentiate into any cell as the need arises, when they are

stimulated.

ROOT LENGTH AND APICAL CLOSURE

We should have knowledge about the dates of tooth eruption, the

completion of the root length and apical closure. Because the complex

root formation and apical closure plays an important role in the repair of

inflammed dental pulps following endodontic therapy.

Moorrees et al. (1963) studied the rot lengths and apical closure

completion dates by using images on lateral jaw radiographs. They found

that root length completion and apical closure dates by using images on

lateral jaw radiographs. They found that root length completion and

apical closure occurs early in females when compared to males.

The maxillary teeth were not studied because their images could

not be identified clearly on lateral jaw radiographs. But judging from the

data of maxillary incisors and mandibular teeth, they surmise that the

dates fro completion of root lengths and apical closures for maxillary

posterior teeth are slightly later than mandibular teeth.

Clinical significance

A funnel shaped opening exists at apex of young tooth that has

incompletely formed root. This incompletely formed root apex contains

connective tissue, blood vessels, nerves which enters and exit the root

canals. Therefore successful repair of inflammed dental pulps occurs in

teeth within complete apical closure when compared with the teeth with

completed apical closure. This may be possibly due to the unobstructed

metabolism.

The pulp capping and pulpotomy procedures are wide successful in

teeth with open apices and complete endodontic therapy has better

prognosis in teeth with complete root end formation. In young teeth with

incomplete root end formation, partial pulpitis can be treated by pulp

capping or pulpotomy procedures thereby permitting normal root end

development i.e. apexogenesis. But in teeth with severely inflammed or

necrotic pulps, the tissues must be removed and the root canals must be

debrided and cleansed. Ca(OH)2 is placed in root canals and completion

of root canal therapy should be delayed until the root end formations has

been completed. This process is known as apexification.

APICAL FORAMEN

Structure:

In young incompletely developed teeth the apical foramen is funnel

shaped with wider portion extending outward. This mouth of the funnel is

filled with fibrous tissue which later will be replaced by dentin and

cementum. As the root apex becomes lined with cementum which

extends to a short distance into the root canal. This is the cementodentinal

junction. CDJ is not present at the extreme end of the root but a few mm

within the main root canal. The apical foramen is not the most constricted

portion of the root canal.

Kuttler in 1955, perfomed studies on microscopic structure of root

apexes. He says that the narrowest diameter of the canal is definitely not

at the site of exiting of the canal from the tooth but usually occurs within

the dentin just prior to the initial layers of cementum. He refers this

position as the “minor diameter”. Some calls it “apical constriction” and

some as “histologic foramen”.

The diameter of the canal at the site of exiting from the tooth is

called “major diameter”. Major diameter was found approximately twice

as wide as minor diameter. In young patients (18-25 years) the distance

between minor and major diameter is approximately 0.5mm and in the

older patients (55 years and above), the distance between minor and

major diameter is approximately 0.67mm.

Clinical significance

Kuttler says that the canal preparations and obturations should be

terminated at the minor diameter. Major advantage is that during

obliteration procedures minor diameter provides a bottle neck area. This

allows the rapid development of a solid apical dentin matrix. This will

enhance the possibility of retaining the filling materials and sealers within

the canal. Pain free treatment can be done because of less or no

impingement on periapical tissues. However techniques to locate exactly

the minor diameter are lacking.

Location:

The apical foramen is not always located at the centre of the apex

of the root. According to Ingle, it is uncommon to find the foramen

exiting at the centre of the apex. It may exit on the mesial, distal, buccal,

lingual portions of the root.

Anatomic studies have shown that the apical foramen coinciding

with the apex is seen only in 17-34% of cases. On an average, it is located

0.4 to 0.7 mm away form the anatomic apex. In few cases the apical

foramen was found 2-3 mm away from the apex.

Shape:

Shape of the apical foramen can be round , oval. It may sometimes

have unusal shapes such as hourglass shape, semilunar or serrated.

Clinical significance of apical foramen:

The apical constriction acts as a natural stop for the filling

materials.

Size and shape of the apical foramen should always be maintained.

It should be neither enlarged nor blocked

Care should be taken to prevent over instrumentation or extrusion

of the root canal filling materials beyond the apex.

LATERAL CANALS AND ACCESSORY CANALS

According to the glossary of American Association of

Endodontists, lateral and accessory canals are differentiated as

Lateral canal: Is a canal that is located at approximately at right angles

to main root canal

Accessory canal: is the one that branches off from main root canal,

usually in the apical region of the root.

Accessory foramina: are the openings of the accessory and lateral canals

on the root surface.

Development:

They may form when the epithelial root sheath disintegrates before

the dentin is elaborated

They may also result firm lack of dentin elaboration around a blood

vessel which is present in the periradicular connective tissue.

Lateral and accessory canals are present in greater numbers in teeth

of younger individuals. As the tooth ages, some accessory canals may

become obliterated by further dentin or cementum formation. They

contain fibrous tissue. Fibroblasts, collagen fibers, nerves, capillaries

and some macrophages may be present within them. The connective

tissue is the same as that found in pulp but more closely resembles the

connective tissue of the periodontal ligament. Usually blood vessels

enter the tooth, some through the apical foramen, some through the

lateral aspects of the root through the accessory foramina.

According to green, the incidence of accessory canals ranged from

10% in maxillary central incisors and mandibular canines to 47% in

mandibular 2nd premolars with the other teeth having incidences

within this range.

Lateral canals: lateral canals are found more in roots of posterior teeth

and occasionally in roots of anterior teeth. More common in bifurcation

and trifurcations regions of molar teeth. Hess in 1925, by the use of

vulcanite corrosion specimens detected, the incidence of 16.9% of lateral

canals in all teeth.

Kramer in 1960 demonstrated large blood vessels in the lateral

canals in furcation regions using vascular injection technique. In some

instances the lateral canals in furcation region are seen traverse the root in

the apical direction and finally entering the root canal in the middle or

apical third.

Accessory canals:

In anterior teeth, Seltzer 1966, observed 34% incidence of

accessory canals. Accessory canals are seen frequently in apical third

of roots. According to Hess (1983) accessory foramina have a mean

diameter of 6 to 60 µm. In many teeth, the width of the accessory

canals and sometimes lateral canals is exceedingly small, permitting

only presence of small caliber blood vessels and their supporting

stroma. Usually these small canals cannot be observed on radiographs.

Apical delta:

The presence of multiple accessory and lateral canals is a rule

rather than an exception which raises the question regarding the fate of

pulp tissue in those canals following endodontic therapy.

The accessory and lateral canals arhe avenues for the interchange

of metabolic and breakdown products between the pulp and the

periodontal tissues. Exposure of lateral canals to the environment due

to the presence of deep periodontal pockets may lead to inflammation

or necrosis of pulp. Conversely breakdown products of inflammatory

pulp lesions may have effect on periodontal tissues via these ccanals.

Following endodontic therapy, in vital teeth, the lateral and

accessory canals tend to become obliterated by deposition of

cementum with passage of time. In teeth with totally inflammed or

necrotic pulps, granulation tissue is found in accessory canals prior to

endodontic therapy. Following endodontic therapy, inflammatory

tissue will get resorbed and replaced with uninflammed connective

tissue.

When pulp is extirpated from the main canals, a clot forms at the

site of the wound. Repair of the wound subsequently occurs if

accessory blood supply is present. In case of “Y” shaped branching of

the pulp i.e. apical delta, following endodontic treatment, the pulp

tissue in uninstrumented branches may become inflammed but usually

retains its vitality with passage of time, continous deposition of dentin

or cemntum tends to narrow the lumina of these canals.

Lateral and accessory canals are difficult to clean adequately.

Thorough and effective irrigation techniques should be carried out. A

tooth with multiple accessory canals in the apical third may harbour

microorganisms and debris which may continue to irritate the periapex

and cause pain inspite of proper filling of the principal canal.

Peripaical surgery is indicated in such cases.

Apical pulp tissue:

The apical pulp tissue is mainly found in the apical end of the root

canal. Most probably continuing into the surrounding periapical region.

The apical pulp tissue differs structurally from the coronal pulp tissue.

The coronal pulp tissue contains mainly of cellular connective tissue and

fewer collagen fibers, whereas the apical tissue is more fibrous and

contains fewer cells.

Histochemical studies by Yamashi et al. in 1986, demonstrated

large concentrations of glycogen in the apical pulp tissue, a condition

compatible with the presence of anaerobic environment. The fibrous

tissue in apical root canal is similar to that of periodontal ligament. In

gross appearance, the collagenous apical tissue is whitish in colour. This

fibrous tissue acts as a barrier against apical progression of pulpal

inflammation. In partial or total pulpitis, however complete inhibition of

inflammation does not occur.

Inflammatory exudates may be found in the periapical tissues, even

thorugh the apical tissue may be free of such exudates.

Blood and nerve supply:

The fibrous structure of apical pulp tissue supports the blood

vessels and nerves which enter the pulp. The pulp of the tooth is supplied

by number of blood vessels which originate in the medullary space of

bone surrounding the root apex. These blood vessels course through the

PDL before entering into the apical foramen as arterioles. The width of

these vessels may be same a s capillaries as they lack the elements in the

walls. The blood vessels ramify in the apical pulp tissue. Projection

microangiographs shows that, on entering the apical foramen the apical

artery divides almost into several principle or central arteries. The blood

vessels are surrounded by large myelinated nervous sheath also branch

after they enter the pulp. Scanning electron microscope studies have

shown the presence of small helmet like structures in the region of apical

foramen. They are thought to protect blood vessels and nerves from

damage due to the masticatory stresses or from minor trauma.

Nerve supplies of the pulp and periodontal ligament provides

background for the interrelationship of pulp and periodontal disease. An

inflammatory and degenerative process involving the PDL could affect its

blood supply and that of some portions of the pulp. Conversely a disease

process affecting the pulpal blood vessels would probably influence some

of the blood vessels of the PDL. Since nerve supply is laso closely

related, periodontal inflammation can cause pain similar tooth ache

caused by pulpitis.

Clinical significance in endodontic therapy:

The clinical significance is especially in giving endodontic therapy

for teeth with vital pulps. When vital pulp tissue is removed from the root

canal tissue especially with a barbed broach the severance of pulp tissue

from PDL is not under control of operator. The severance can occur

anywhere in the root canal or even beyond the apical foramen, however

in the periodontal ligament, when the later type occurs, ensuing

hemorrhage cause painful pericementitis.

Apical dentin:

In the apical region, odontoblats of the pulp are absent or flattened

or cuboidal in shape. The dentin that is not as tubular as coronal dentin,

but instead more amorphous and irregular. This type of dentin is called

sclerotic dentin. The amount of sclerotic dentin generally increases with

age. At the orifices of root canals of younger teeth, the dentinal tunules

become more oblique. In older teeth, the floor of the pulp chamber is

irregular and atubular with the presence of atubluar calcospheres.

Studies by Coughlam in 1985, have revelaed under gorund

sections that thie dentin has two zones;

a) Peripheral translucent zone

b) Inner opaque zone

Opaque zones are more closely packed and wider than those of

translucent zone. Couhlam concluded that transparency of apical dentin

was due to diminution in width of tubules.

The use of isotope studies by Hampson in 1964 have shown that

apical dentin is more sclerotic than coronal dentin. The sclerotic apical

dentin is considerably less peircable than the coronal dentin. This reduced

permeability has significance because the sclerosed dentinal tubules are

less readily penetrated or are impenetrable by microorganisms or other

irritants.

Reason for root curvature in the apical third:

When the tooth erupts into the oral cavity and becomes functional,

its root formation is not completed. It is wide open and the Hertwig’s

epithelial root sheath, a circular curtain like structure, is active with its

root formative function.

Two important things may happen as this tooth becomes functional

It is made to bear the biting stress which may move the tooth in

mesial direction and

The occlusal load may disturb the curtain like Hertwig’s epithelial

root sheath at the apical third.

Break in the continuity of the circular curtain like structure of the

root sheath, due to stress transmitted by the biting forces, may be the

reason for the abundant occurrence of accessory canals in the apical third.

Root resorption:

Shallow resorption of dentin in the apical portion of the root canal

are normal occurrences. Resorption of cementum and dentin occurs on

the body of the root also at the periapical region. Apical root resorption is

mainly due to

a) Orthodontic tooth movement

b) Inflammation of apical pulp and peripaical periodontal

tissues

Orthodontically induced root resorption is mediated by

prostaglandins elaborated by localized cells which stimulate osteoblastic

activity. The resorption widen the apical foramen leaving a funnel shaped

structure. As inflammation subsides repair of resorbed region occurs by

deposition of secondary cementum.

Change in the anatomy of root apex:

As a result of resorption and repair change in the anatomy of the

root apex occurs with passage of time. During orthodontic tooth

movement, the anterior component of force causes the teeth to move

mesially. The teeth also have a continuous eruptive force. These

combined forces occlusally and mesially cause tension on the distal side

causing bone apposition and pressure on mesial side causing resorption.

Thus while the principal apical foramen which is in the centre of the root

s originally will gradually shift towards one side sometimes occlusally.

Age changes at the periapex:

-Denticles and dystrophic mineralisations

-Secondary dentin and cementum deposition

Dystrophic mineralisations:

Brynolf found diffuse, scattered dystrophic mineralisations in

approximately 7% of human upper incisors. These mineralisations are

located within and around the collagen fibres and rarely in the myelin

sheaths of the nerves in the apical pulp tissue. The mineralisations may

vary in appearance from fine, diffuse fibrillar variety to large denticle like

accumulation.

Denticles/pulp stones:

Denticles are formed around foci of mineralizing pulp tissue

components such as collagen and nerve fibers, blood vessels, ground

substance, inflammed and necrotic cells. Denticles are composed of

tubular dentin and atubular mineralized material and can be attached or

embedded being partially or completely surrounded by dentin. In the

apical third of the root approximately 15% of teeth show pulp stone and

more than one pulp stone is usually found.

Clinical significance:

Denticles found within the pulp tissue in the apical third of the root

may account for some difficulties in root canal instrumentation. During

reaming or filing of root canal they may become detached and impacted

into the apical foramen rendering further instrumentation difficult.

Secondary dentin and cementum deposition:

Secondary dentin is deposited contiuously by the radicluar pulp

tissue. Secondary dentin is seen on the root canal walls of some teeth and

in greater quantities in periodontlally involved teeth. Towards the apex of

the tooth, the dentinal tubules appear to blend with cementum canaliculi.

Clinical significance:

The apical foramen or foramina tend to become obliterate by both

the deposition of secondary dentin within the root canal and by the

deposition of cementum outside the root canal. Continuous dentin and

cementum deposition will reduce the size of apical foramen but complete

closure does not occur as long as vital pulp tissue remain.

Radiographic assessment of apical third:

The lateral canals, accessory canals and other anantomic

aberrations cannot be easily identified. The clinician shouls have sound

knowledge about these anatomic variations. Clinically also we shouls

examine carefully for extracanals by probing the potential area using a

sharp pointer or an endodontic explorer. Radiographically, we can assess

and sometimes identify the anatomic variations.

When the radiograph shows root canal that descends from the

puplpal floor and suddenly stops in the apical reion then, bifurcation or

trifurcation in the apical region can be expected. To conform this, a

second radiograph is exposed from a mesial or distal angulation of 10-

30º. This resultant film will show more roots or vertical lines indicating

peripheries of additional root surfaces.

If the root canal shadow abruptly stops in the middle third of the

root or if the diameter of the root canal suddenly narrows down then it

denotes that the root canal may be dividing into two. This is very

common occurrence in mandibular premolars. If there is a lateral

radiolucency present in the apical one third of the root, it may indicate the

possibility of lateral canal accessory canals or presence of periodontal

lesions.

If there is a radiolucent line running along the diagnostic

instrument whose long axis is not in relation to the instrument then there

is high chance of additional canal. The recent advancements like

xeroraiography, radiovisiography, digital substraction radiography,

computed tomography also will be helpful for identifying these minute

anatomical variations.

Other features of apex on radiographs:

i) Thin “pinched” apex – care should be taken during

instrumentation to avoid perforation.

ii) Bulbousapex – Bulbous appearance of apex is due to

hypercementosis. In cases of bulbous apex apical constriction

may be significantly shorter from the radiographic apex

compared to normal teeth.

iii) Resorbed apex – Advanced inflammation at the periapex

usually causes resorption of cementum, either widening of

apical foramen. Such changes will make working length

determination difficult with proper apical preparation and

condensation of gutta-percha. So apical stop should be created

in such teeth.

iv) Blunderbuss apex – a newly formed tooth would normally

show an incompletely forced root having a wide root canal and

an open apex. Such a canal is termed immature or blunderbuss

canal.

Apical Preparation:

Length determination:

The first step in the prepration is the location of the foramen in the

root apex. Although a radiographic assessment with a measured endo

instrument in the canal is an accepted procedure for the determination of

the tooth length, measurements using electronic instruments are

becoming increasingly popular. Electronic measurement of the tooth

length according Grossman (1981), is an effective method in 80 to 90%

of the cases compared to the radiographic method. Neosono D, according

to some clinicans, indicates the exact location of the foramen with

reasonable accuracy. Galland (1985) recommends electronic apex finder

for those who perform endo treatment infrequently.

Determination of the working length is an essential step in

obtaining the hermetic seal as wrong estimation could either lead to an

enlarged foramen resulting in i) periapical irritation, ii) possible weeping

of the canal, and iii) Loss of control during obturation, or lead to

apreparation short of foramen with the resultant ledge formation and

accumulation of dentin mud.

Instruments & instrumentation:

Time spent on the proper preparation of the apical portion greatly

simplifies the subsequent canal preparation. Two general principles to be

adhered to, while preparing the apical third, are

The maintenance of the spatial integrity of the foramen

Smooth shaping of the original course of the canal

Careful selection of instruments and special manipulative

techniques are essential requirements for a successful preparation of

apical zone. Improperly prepared access cavity would presupposedly

affect the preparation of the apical zone. Impingement of the endo

instrument coronally would result in either ripping of the foramen or

formation of a ledge and thus making it almost impossible to obtain a

satisfactory seal.

Ninety percent of the canals are curved (Christie & Peikoff

1980), and precurving of the files is a must in all such cases. By

precurving the instruments the original course of the canal and location

of the foramen are preserved.

Slight deviation from proper handling of the files could

disastrously spoil the preparation. Files are not to be given quarter turn

bites into dentin or pulled forcibly with lateral pressure along the canal

walls when preparing the apical end of the canal. Rotation of

instruments has been found to violate the basic principle as it forms an

‘hour glass’ outline rather than a smooth taper near the apex (Weine et

al. 1975).

Flexible files are preferred over stiffer varieties since they may

change the course of the canal, form a ledge or transport the foramen by

ripping. D- type files (produced from rhombus blanks) are more flexible

than regular K- type files (produced from square blanks) in size no: 30

and above (Anderson et al. 1985). The new K- type file (triangular cross

sections ) is more flexible than H- file (Roane et al 1985).

Methods of preparation:

Preparation design has an influence upon the final seal. Step back

or flaring type of preparation of the apex is found to be advantageous

over the conventional method (Allison et al. 1979). Flared preparation

provides a cleaner environment, better receptacle for the obturating

material, and a stronger apical dentin matrix (Weine 1982). Chances of

apical ripping and shifting I foramen are less with step- back technique

(Christie & Peikoff 1980).

Various special techniques have been introduced by different clinicians

for acceptable preparation of a curved apical third (Mullaney 1979;

Weine 1982; Roane et al. 1985). Roane et al. (1985) introduced a new

‘balanced force concept’ using the latest K- type file, triangular cross cut,

for the preparation of apical zone in deeply curved canals.

The traditional approach to canal prepration was to negotiate and

prepare the apical one third of the root canal first followed by a coronal

flaring technique to facilitate obturation. In this technique the clinician

selects a small diagnostic file, places an appropriate curve on the

instrument, then eagerly works the file to length. When a file cannot be

carried to the terminus, it is removed and the root canal space is

reirrigated. The file is then recurved and reinserted, and a more focused

effort is made to move it to length. The break down is the failure to

recognize that frequently the rate of taper of the instrument exceeds the

rate of taper of the canal that prevents the file’s apical movement. When

an instrument binds on its more shank side cutting blades, the clinican

loses apical file control.

Attempting to negotiate and prepare the apical one third of the

canal first is challenging in the most delicate part of the microanatomy.

Often a straight root holds a curved canal. Clinician need to recognize

that most canals move through multiple planes of curvature over length.

Mesial and distal curvatures are best visualized radiographically.

However, buccal and lingual curvatures also need to be appreciated.

Additionally, canals typically exhibit their greatest curvatures and deep

divisions in their apical extents. The degree, length and abruptness of a

canal curvature, in conjunction with its propensity to divide, should be

factored into the preparation sequence. Specifically passing a precurved

negotiating file through a coronally tight and under prepared canal

straightens the instrument. Unknowingly attempting to work straighter

files to length in curved canals first invites the block, then predisposes the

patient to the formation of a ledge. Further contributing to breakdowns in

the apical preparations first, sequence is the fact that nonflared canals

hold a minimal volume of irrigating solution that inturn, invites the

accumulation of dentin mud. Working short, in conjunction with

attempting to prepare the apical one third first, has led to canals that have

been ledged, externally transported, or apically perforated.

Irrigation:

A strict rule to follow is to irrigate the canal copiously between

each instrumentation. It facilitates the removal of dentin shavings and

maintains the cutting efficiency of the instruments by relieving clogging.

Once the dentin mud settles at the apical level, it becomes difficult to be

dislodged.

Since 1955, Grossman (1982) has advocated the alternate use of

5% NaOCl with 3% hydrogen peroxide. The effervescence obtained on

using hydrogen peroxide, he advocated would bring the shavings to

surface. However, in a study conducted by Svec and Harrison (1981), the

difference in the accumulation of dentin mud after the use of NaOCl

alone and with 3% hydrogen peroxide is found to be statistically

insignificant. Furthermore, effervescence due to the use of 3% hydrogen

peroxide always bubbles upwards. Hence, the use of the same in the

upper teeth would detrimentally drive the mud apical wards instead of

crown wards (Schilder & Yee 1984). The circulation of the irrigant has

been found to remain short of the apical third of the canal, particularly in

curved teeth, unless specially made fine needles are used (Goldman et al

1976).

Chlorhexidine has been advocated for endodontic use due to its

broad spectrum antimicrobial activity and least irritant nature on the

periapical tissues. However, its inability to dissolve tissue fragments has

been a problem. Though NaOCl is considered as the irrigant of choice,

chlorhexidine gluoconate should be considered in conditions such as

young permanent teeth with immature apices or open apices.

Obturation:

Sealing is done to eliminate all the portals of entry from the root

canal into the adjacent periodontal tissues through which exudates,

bacteria or their toxins might pass; and to make the environment

favourable for healing. Ingle (1956) determined 63% of the root canal

failures to be due to inadequate filling. Accessory foramina if left open

and remain unfilled can lead to failure of treatment. The necessity to

provide hermetic sealing of the apical foramen as well as filling of the

accessory canals has brought forth many dynamic changes in the

obturation techniques.

Ideal response after endodontic treatment is the biologic closure of

the apex. Many methods were tried. Nysgaard Ostby (1961) attempted

natural healing at the apex by inducing bleeding. The subsequent

formation of the clot was hoped to serve as a matrix for tissue ingrowth.

However, the formation of biological closure was found negated as the

clot fibrin was observed to degenerate within the canal coronally.

Consistently successful results have been reported in teeth which had

treatment (Holland & Souza 1984). The pulp at the apex has been adviced

(Leonardo et al 1984) not to be disturbed either by way of

instrumentation or medicaments; extreme care and respect to be shown to

the vitality of the pulp.

Apexification:

In young teeth with incomplete root end formation, partial

pulpitides can be treated by pulp capping or pulpotomy procedures,

thereby permitting normal root end development (apexogenesis). In teeth

with severely inflammed or necrotic pulps, the tissues must be removed

and the root canals must be debrided and cleansed in the usual manner.

Thereafter, completion of endodontic therapy should be delayed until root

end formation has been completed. Such a procedure has come to be

known as apexification. In comparing the results of treatment in 166

traumatized incisors, Kerkes et al (1980) found that, in 9 to 12 year old

patients, apexification procedures produced better results than standard

root canal treatments with filled root canals. In 18 year old patients,

standardized root canal therapy yielded the best results.

Various procedures and medicaments have been recommended for

inducing apexification. These have induced Tricresol and formalin

(Cooke and Rowbotham, 1960); antibiotic pastes (Ball, 1964); Tricalcium

phosphate (Koenigs et al, 1975) and calcium hydroxide.

Based on the results of numerous investigations, calcium hydroxide

has emerged as the drug of choice for apexification. Both the alkalinity

and the calcium ion are apparently needed to induce hard tissue formation

(Tronstad et al 1981). Other calcium compounds, such as calcium

chloride, have not been effective nor have other hydroxides, at the same

pH, such as ammonium or barium hydroxide.

Numerous recommendations have been made for vehicles to be

used for the Ca(OH)2. These include camphorated p-chlorophenol,

iodoform, water local anesthetic solution, glycerol and other

medicaments.

For increasing radio opacity, additions of barium sulfate (Stewart

1975), solutions of 10% iodine and 20% potassium iodide or diatrizoate,

a form of organic iodine, have been recommended. According to Smith

and Woods (1983), the diatrizoate compounds are more and absorbable

than barium sulfate.

Histologic studies indicate that various types of hard tissue that

resembles bone or cementum or dentin or osteodentin are induced at the

apex. Satisfactory results have been reported from standard endodontic

therapy and root canal filling considerably short of the developing root

apex. Under such circumstances, if Hertwig’s root sheath has not been

damaged, there is a reasonable probability that the apex will develop in a

normal manner.

Dentin chip apical filling:

A method finding increasing favour, is the apical dentin chip plug

against which other materials are then compacted. Dentin chip plug

provides a “biologic seal” rather than a mechanochemical seal. Gottlieb

and Orban noted cementum forming around dentin chips in the PDL as

early as 1921. El Deeb stated that apical dentin plug is significantly

effective in confining the irrigating solutions and filling materials to the

canal space. Oswald and Friedman concluded that dentin chips lead to

quicker healing, minimal inflammation, and apical cementum deposition,

even when the apex is perforated.

Method of use:

The dentin chip technique has been used and taught at the

universities of Oregon and Washington. After the canal is totally debrided

and shaped and the dentin no longer “contaminated”, a Gates Glidden

drill or Hedstroem file is used to produce dentin powder in the central

position of the canal. These dentin chips may then be pushed apically

with the butt end and then the blunted tip of a paper point. They are

finally packed into place at the apex using a premeasured file one size

larger than the last apical enlarging instrument. 1-2mm of chips should

block the foramen.

The Japanese found they could totally prevent apical microleakage

if they injected 0.02ml of clearfil bond dentin adhesive into the coronal

half of the dentinal apical plug. Completeness of density is tested by

resistance to perforation by a no. 15 or 20 file. The final gutta-percha

obturation is then compacted against the plug.

Efficacy of dentin chip apical obturation:

One of the positive effects of a dentin plug filling is the elimination

of extrusion of sealer or gutta-percha through the apex. This reduces

periradicular inflammation. In a monkey study done at Loma Linda

indicated that the inorganic component of dentin, Hydroxyapatite is the

principal stimulant in proceeding more hard tissue formation and less

inflammation than fresh dentin chips.

The dentin chip apical plug is a valuable contribution to endodontic

success and deserves to be more widely employed.

Conclusion:

The morphological variations and the technical challenges involved

in treatment of the apical third seems infinite. It has to be remembered

while treating the apical third that the proximity of the apices of certain

teeth are in close association with important structures like maxillary

sinus an inferior alveolar nerve. Inadequate attention and improper

handling of the apical third of these teeth may lead to serious clinical

implications.

The root apex is morphologically the most complex region

therapeutically a challenging zone and prognostically an important and

unfortunately most obscure and unclear area. So, endodontist should have

detailed knowledge of the anatomic variations and mechanical challenges

involved in the treatment of apical third for effective and efficient

management during endodontic therapy.