Development of Root Apex

8/13/2019 Development of Root Apex

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DEVELOPMENT OF ROOT APEX

Introduction

The root apex is of interest to endodontics because the stages of root

development and the type of tissue present within the roots of teeth are

significant to the practice of endodontics.

Also, appreciable knowledge of the morphology of the root apex and its

variance, ability to interpret it correctly in radiographs, and to feel it throughtactile sensation during instrumentation are essential for an effective rendering

of the treatment of root canals.

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

is the ultimate goal for every endodontist.

The development of the root begins after the enamel and the dentin

formation has reached the future cemento-enamel junction.

The enamel organ play an important part in root development by

forming Hertwigs epithelial root sheath, which molds the shape of the roots

and initiates radicular dentin formation.

Hertwigs root sheath consists of the outer and inner enamel epithelia

only !and therefore it does not include the stratum intermedium and stellatereticulum".

The cells of the inner layer remain short and normally do not produce

enamel.

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$hen these cells have induced the differentiation of radicular cells into

odontoblasts and the #stlayer of dentin has been laid down, the epithelial

root sheath loses its structural continuity and its close relation to the surface

of the root.

%ts remnants persist as an epithelia network of strands or tubules near the

external surface of the root.

These epithelial remnants are found in the periodontal ligament of

erupted teeth and are called &cell rests of 'alasse().

There is a pronounced difference in the development of Hertwigs

epithelial root sheath in teeth with one root and in those with * or more roots.

+rior, to the beginning of root formation the root sheath forms the

epithelial diaphragm.

The outer and inner enamel epithelial bend at the future cemento-enamel

junction into a hori(ontal plane narrowing the wide cervical opening of the

tooth germ.

The plane of the diaphragm remains relatively fixed during the

development of growth of the root.

The proliferation of the cells of the epithelial diaphragm is accompanied

by proliferation of the cells of the connective tissue of the pulp, which

occurs in the area adjacent to the diaphragm.

The free end of the diaphragm does not grow into the connective tissue,

but the epithelium proliferates coronally to the epithelial diaphragm.

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The difference of odontoblasts and the formation of dentin follow the

lengthening of the root sheath.

At the same time the connective tissue of the dental sac surrounding the

root sheath proliferates and divides the continuous double epithelial layer,

into a network of epithelial strands.

The epithelium is moved away from the surface of the dentin so that

connective tissue cells come into contact with the outer surface of the dentin

and differentiate into cementoblasts that deposit a layer of cementum onto

the surface of the dentin.

The rapid seuence of proliferation and destruction of Hertwigs root

sheath explains the fact that it cannot be seen as a continuous layer on the

surface of the developing root.

%n the last stages of root development, the proliferation of the epithelium

in the diaphragm lags behind that of the pulpal connective tissue.

The wide apical foramen is reduced first to the width of the

diaphragmatic opening itself and later is further narrowed by apposition of

dentin and cementum to the apex of the root. ifferential growth of the

epithelial diaphragm in multi-rooted teeth causes the division of the root

trunk into * or roots.

uring the general growth of the enamel organ the expansion of its

cervical opening occurs in such a way that long tongue-like extensions of

the hori(ontal diaphragm develop.

* such extensions are found in the germs of lower molars and in the

germs of upper molars.


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/efore division of the root trunk occurs, the free end of these hori(ontal

epithelial flags grow toward each other and fuse.

The single cervical opening of the coronal enamel organ is then divided

into * or openings.

0n the pulpal surface of the dividing epithelial bridges, dentin formation

starts.

0n the periphery of each opening, root development follows in the same

way as described for single rooted teeth.

Apical Foramen and Apical Constriction

1ocation and shape of the fully-formed foramen vary in each tooth and

in the some tooth at different periods of life. Awareness of these is considered

important for effective rendering of the treatment.

The foramen can change in shape and location because of functional

influences on the tooth, for e.g.2 tongue pressure, occlusal pressure, mesial

drift. 3ementum resorption occurs on the wall of the foramen furthest from the

force, apposition on the wall nearest. The net result is the deviation of the

foramen away from the true apex.

%t is a popular misconception that the apical foramen coincides with the

anatomical apex of the tooth. This is an infreuent occurrence and usually the

apical foramen opens 4.5-#mm fm the anatomical apex.

This distance is not always constant and may increase as the tooth ages

because of the deposition of *6 cementum on the outer surface of the root

and *6 dentin on the wall of the root canal.

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Type %?2 * separate and distinct canals extend from the pulp chamber to the

apex.

Type ? 2 0ne canal leaves the pulp chamber and divides short of the apex

into * separate and distinct canals with separate apical foramina.

Type ?%2 Two separate canals leave the pulp chamber, merge in the body of

the root, and redivide short of the apex as * distinct canals.

Type ?%%2 0ne canal leaves the pulp chamber, divides and then rejoins within

the body of the root, and finally redivides into * distinct canals

short of the apex.

Type ?%%%2 separate and distinct canals extend from the pulp chamber to the

apex.

8enerally, the roots have a single apical foramina and a single canal

!Type %". However, it is not uncommon for other canal complexities to be

present and exit the root as one, two or three apical canals !Types %% @ ?%%%".

Apical Constriction

The apical foramen is not always the most constricted portion of the root canal.

reuently the narrowest portion of the root canal, termed the &apical

constriction) occurs about 4.5-#mm from the apical foramen.

Again, the position of the apical constriction varies with age as deposits

of *6 dentin, within the root canal, move the site of the constriction

away from the apex.

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%deally the root filling should stop at this constriction as it would serve

as &apical dentin matrix).

!an artificially produced ledge in the apical root canal, against which

gutta percha could be compacted without the fear of its protrusion into the

periapex."

%f the constriction is destroyed by over @ instrumentation and an apical

stop is not developed, the chances of long term success are greatly

lessened.

3alcification of the root apex occurs is essential for endodontic practice,

particular when dealing with pulp involved or pulpless teeth of children and

young persons.

As a general rule, a root apex is completely formed about *- years after

the eruption of the tooth.

The following table gives the approximate time in years of eruption of

the teeth and calcification of the root apices.

3% 1% 3uspid #stpm *ndpm #stmolar *ndmolar

Bruption >-C :-9 #4-#* 9-## ##-#* 5-: #*-#

3alcification #4-#* ##-#* #-#7 #*-#7 #-#7 #4-## #5-#>

%n young incompletely developed teeth the apical foramen is funnel

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

filled with periodontal tissue that is later replaced by dentin and cementum.

Any injury occurring before its closure may result in changes that may

lead to formation of the blunder burs canal.

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=uccessful repair of inflamed dental pulps in teeth with incompletely

apical root closure is enhanced compared to that of teeth with completed root

formation.

+ossibly therefore, the unrestricted metabolism in the former group

Thus pulp capping and pulpotomy procedures have a better chance for

successful resolution in teeth with open apexes. 0nce root end formation

has been completed, complete endodontic therapy has a better prognosis

than pulp capping or pulpotomy procedures.

Instrumentation

Time spent on the proper preparation of the apical portion greatly

simplifies the subseuent canal preparation.

The general principle to be adhered to while preparing the apical third is

confine cleaning and shaping procedures

#. 'aintenance of the spatial integrity of the foramen and

*. =mooth shaping of the original conese of the canal.

Adherence to this principle prevents violation of the preradicular tissues.

This principle is evident when foramina are transported !i.e. moved" during

excessive apical instrumentation.

oramina transportation can be either #. Bxternal, *. %nternal.

Bxternal transportation takes * forms and may occur when

instrumentation is carried out beyond the apical dentin matrix !constriction".

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0ne result is the ripping of the apical end of the canal resulting, #.

teardrop *. ethiptical or . Dipped foramen;

%n its grosser form external transportation leads to an outright

perforation of the root.

%nternal transportation can also occurs when excessively large

instruments are used in the apical third of a curved canal.

Bven though a perforation may not have occurred, there is a definite loss

of the narrowing apical preparation and the spatial relationship of this

preparation to the apical foramen.

8enerally, both types of transportation of the apical foramen can be

presented by containing cleaning and shaping procedures within the canal

system, by

#. Esing precurved instruments.

*. by resisting the temptation to excessively enlarge the apical portion of

the canal.

. by using voluminous irrigation.

7. by preventing a build up of dentin sharing during instrumentation

procedures by freuent recapitulation.

Met!ods of preparation

+reparation design has an influence upon the final seal.

=tep-back or flaring type of preparation of the apex is found to be

advantageous over the conventional method !Allison et al #9:9".

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lared preparation provides a strong apical dentin matrix !$eine #9C*".

3hances of apical ripping and shifting of foramen are less with step back

techniue !3heistic and +erkoff #954".

Fepeated instrumentation extending beyond the constriction is

uncounted. %t causes peri-ridiculer inflammation and often destroy the !n"

biologic constriction of the root apex.

Although, rare perforations of the floor of the nose, max sinus or

mandibular canal as a result of excessive overextension of instruments can lead

to sever post treatment pain, delayed healing and ultimate failure.

%nternational over extension of instruments is warranted only when

drainage must be established in the periradiculer tissues, such as in an acute

apical abscess etc.

Cemento"Dentinal #unction

According to Gutler !#95C" the root canal is divided into a long conical

dentinal portion and a short funnel shaped cemental portion.

The cemental portion is usually in the form of an inverted cone with its

narrowest diameter at or near the cementodentinal junctions its base at

the apical foramen.

However, occasionally the cementum abuts directly on the dentin at the apex.

At times, the cementum extends for a considerable distance into the root

canal, lining the dentin in an irregular manner.

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?ariations are especially likely to occur in periodontaly involved teeth

or in teeth which have been moved orthodontically. %n those instances, the root

canals as well as the apexes may almost become obliterated by heavy

deposition of *6cementum.

The extent of cementum deposition on each wall of the root canal varies,

one wall is usually covered with a greater uantity of cementum than the other

wall.

0ccasionally, tissue which resembles both dentin and cementum is seen.

The uantity of this intermediate tissues varies among the teeth of

different patients.

o definite morphological pattern of the cementodentinal junction is

found consistently.

The thickness of cementum around the apical foramen is inconsistent

and varies greatly.

$inificance

The significance of the cementodentinal junction leis in its implication

by a number of investigators !8rove, #94I Hall #94I Gutter #95C" as the

precise region to which the root canal should be filled.

Guttler !#955" claimed that the distance between the 3J and the apical

foramen averaged 4.54:mm in young people and 4.:C7mm in older people,

thereby enabling the clinician to measure more precisely the distance to which

the root filling should extend.

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Accessor% Canals and Foramina

The apical and accessory foramina provide an opening for micro-

organisms and ;or toxins to diffuse into the apical periodontal space, setting up

on acute or chronic apical periodontitis.

This irritation or infection may then follow the path of least resistance,

which maybe in a coronal direction along the lateral root surface, initiating a

marginal gingivitis or periodontitis.

The inflammatory process may occur in the opposite direction from the

gingiva and along the periodontal ligament space to the apical and accessory

foramina and into the pulp space to establish pulp inflammation and its

seuence.

References&

#. =amuel =elt(er !*nd

Bdition" !Bndodontology"

*. 8rossman !##thBdition" Bndodontic +ractice

. +araneswarm !current trends in Bndodontology"

7. .J. Harty !Bndodontics in clinical practice"

5. 3ohen !Bndodontic"

>. %ngle !Bndodontic"

Apical Resorption

=hallow resorptions of the dentin in the apical portion of the root

canal are normal occurrences.

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Fesorption of the apex can occur due to several seasons.

%n periodontally involved teeth, the cementum and occasionally some

apical dentin, is completely resorb from the rot apex.

A divided scalloped, funnel-shaped structure remains.

The root ends maybe resorbed during orthodontic tooth movement of

the teeth. The root apex may be obliuely resorbed or have a cupped-out

appearance.

'ost resorptions are repaired by cementum.

%n any event if apical resorption has taken place, the apical foramen will

be in the centre of the root.

%f the root resorption has a &moth-catin appearance) it is possible that

the tooth, by accident, was ripped loose fin its ligaments and ; or wasreplanted.

=ometimes an unexplained lesion in the region strongly suggests a

malignancy.

$hen resorption has enlarged apical portion of the canal, apical closure

techniues show be used to ensure.

%t would be difficult if not impossible by our current techniues to

instrument and cleanse the accessory canals, even with thorough remaining and

filing.

%n teeth with totally inflamed ; necrotic pulps, gramlomatous tissue is found

in the accessory canals prior to endodontic therapy.

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The significance of the involved tissue remaining in the accessory foramina

as a factor of failure of repair after endodontic therapy has yet been

definitely determined.

+resumably, following endodontic therapy, the inflammatory tissue should

be resorbed and replaced with uniflamed connective tissue.

An accessory canal also create a periodontic endodontic pathway of

communication and possible portal of entry into the pulp if the periodontal

tissues lose their integrity.

%n periodontal disease the development of a periodontal pocket may

expose an accessory canal and thus allow micro organisms or their metabolic

products to gain access to the pulp.

Conclusion

The morphological variations and the technical challenges involved in

the treatment of the apical third seems infinite.

Fesorption, weeping apex, immature foramen are some of the areas

which continue to invite fresh views from clinicians and researches.

%t 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 and inferior alveolar nerve.

%nadeuate attention and improper handling of the apical rd of these

teeth may lend to serious clinical implications.

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=ince in endodontics has grown to a great height compared to how it

was * decades ago. 3ases which were ill understand and found difficult to treat

than are presently managed with case and confidence.

The drawback which is yet to be tackled is the consumption of

considerable chairside time.

$ith the introduction of high technologies and advancement of science

in endodontics, the problem is bound to be solved soon.

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Development of Root Apex

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