restoration of endodontically treated tooth 97

7/25/2019 Restoration of Endodontically Treated Tooth 97

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RESTORATION OFENDODONTICALLY TREATED TOOTH

dr shabeel pn


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Introduction

A tooth that has been properlytreated endodontically should have agood prognosis. It can resume fullfunction and if necessary servesatisfactorily as an abutment for axed or removable partial denture.

However, special techniques areneeded to restore such a tooth.


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Dierent clinical techniques havebeen proposed to solve theseproblems, and opinions dier as to

the most appropriate one. !ecentexperimental data have improvedour understanding of the di"culties

inherent in restoring anendodontically treated tooth


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#!$A#%$ '(A&&I&)

$xisting endodontically treated teethneed to be assessed carefully for thefollowing*

Good apical seal&o sensitivity to pressure

&oexudate

&o stula&o apical sensitivity

&o active in+ammation


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ne-piece post crowns were once made, theseprostheses are of historical interest only and areno longer attempted

A superior result can be obtained with a two-steptechnique. urrently a metal post is used to retaina core that replaces lost tooth structure and resultsin the shape of a conventional preparation

%orphologic and functional dierences between

anterior teeth and posterior teeth require that theybe treated dierently after endodontic therapy


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Considerations for anterior teeth

Anterior teeth do not always need completecoverage, except when plastic restorativematerials would have limited prognosis in

view of the extent of coronal destruction.%any function with composite resinrestorations.

when the tooth is loaded, stresses are

greatest at the facial and lingual surfaces ofthe root and an internal post, being onlyminimally stressed, does not help preventfracture


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Disadvantages to the routine use of a cemented post*

/. 'lacing the post requires an additionaloperative procedure.

0. 'reparing a tooth to accommodatethe post removes additional toothstructure.

1. It may be di"cult to restore the toothlater, when a complete crown is needed,because the cemented post may havefailed to provide adequate retention for thecore material.

2. #he post can complicate or prevent

future endodontic retreatment if thisbecomes necessar .


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onsiderations for posterior teeth

$ndodontically treated posterior teeth aresub3ect to greater loading than anterior teethare because of their position closer to theinsertion of the masticatory muscles. #his,combined with their morphologic characteristics, ma4es them more susceptible to fracture.

omplete coverage is recommended on teethwith a high ris4 of fracture, especially maxillarypremolars, because complete coverage givesthe best protection against fracture


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PROCEDURES


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#ooth preparation for endodontically treated teethcan be considered as a three-stage operation

!emoval of the root canal lling material to theappropriate depth,

$nlargement of the canal

'reparation of the coronal tooth structure.


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Removal of the endodonti !llin" material

It is recommended that the rootcanal system rst be completelyobturated and then space made for a

post. #his will ensure that lateralcanals are sealed. A post cannot beplaced if the canal is lled with a full-

length silver point, so these must beremoved and the tooth retreatedwith gutta-percha.


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#here are two commonly usedmethods for removing gutta-percha*with a warmed endodontic plugger

and with a rotary instrument* therotary instrument is sometimes usedin con3unction with a chemical agent

such as chloroform


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/. 5efore removing gutta-percha, calculate theappropriate length of the post.

0. Avoid the apical 6 mm if possible. urvatures andlateral canals may be found in this segment

1. #o prevent aspiration of an endodontic instrument,apply a rubber dam before preparing the post space.

2. 7elect an endodontic condenser large enough to holdheat well but not so large that it binds against the canalwalls.

6. %ar4 it at the appropriate length normally endodonticwor4ing length minus 6 mm, hi-at it. and place it in the

canal to soften the gutta-percha.8. If the gutta-percha is old and has lost iu thermo-

plasticity. use a rotary instrument, ma4ing sure that theinstrument follows the gutta-percha and does notengage dentin lest it cause a root perforation.


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9. If using a rotary instrument, choose it to beslightly narrower than the canal.

:. 5e careful that the instrument follows the center

of the gutta-percha and does not cut dentin.;.


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Enlar"ement of the anal

'rior to enlargement of the canal, adecision must be made regarding thetype of post system that will be used

for fabrication of the post-and-core.


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For prefabricated posts

/. $nlarge the canal one or two si=eswith a drill, endodontic le, or reamerthat matches the conguration of the

post.

0. >se a prefabricated post thatmatches standard endodontic

instruments. 1. 5e especially careful not to

remove more dentin at the apical

extent of the post space than is


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For custom-made posts

/. >se custom-made posts in canals that havea non-circular cross section or extreme taper.$nlarging canals to conform to a preformedpost may lead to perforation.

0. 5e most careful on molars to avoidroot perforation.

In mandibular molars the distal wall of the

mesial root is particularly susceptible. Inmaxillary molars the curvature of themesiobuccal root ma4es mesial or distalperforation more li4ely.


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Pre#aration of the oronal tooth str$t$re

After the post space has beenprepared, the coronal tooth structureis reduced for the extracoronal

restoration. Anterior teeth requiring apost-and-core will best be restoredwith a metal-ceramic crown.


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/. Ignore any missing tooth structure fromprevious restorative procedures, caries, fracture,or endodontic access and prepare the remainingtooth as though it were undamaged.

0. 5e sure that the facial surface of the tooth isadequately reduced for good esthetics.

1. !emove all undercuts that would prevent with

drawal of the pattern.

2. !emove any unsupported tooth structure, butbe careful to preserve as much of the crown aspossible.

6. 5e sure also that part of the crown is preparedperpendicular to the post

8. omplete the preparation by eliminating sharpangles and establishing a smooth nish line.


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Availa%le materials

'refabricated parallel-sided posts are made of

'latinum-gold-palladium ?'t-Au-'d or ')'@,

&ic4el-chromium ?&i-r@

cobalt-chromium ?o-r@

stainless steel clasp wire.

7errated posts come in stainless steel, titanium, ornonoxidi=ing noble alloy.

#apered posts are available in Au-'t, &i-r. and

titanium alloys.

All these posts have a high modulus of elasticity andan elongated grain structure, which contribute totheir more suitable physical properties as compared

to cast posts. $ssentially, they are more rigid.


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Custom-made posts

A custom-made post can be castfrom a direct pattern or an indirectone. A direct technique utili=ing

autopolymeri=ing resin is recommended for single canals whereas anindirect procedure is more

appropriate for multiple canals.


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Direct procedure/. (ightly lubricate the canal and notch a loose-tting plastic dowel.

It should extend to the full depth of the prepared canal.

0. >se the bead-brush techniqueto add resin to the dowel and seat itin the prepared canal. #his is best done in two steps* Add resin onlyto the canal orice rst. An alternative is to mix some resin and roll itinto a thin cylinder. #his is introduced into the canal and pushed toplace with the monomer-moistened plastic dowel.

1. Do not allow the resin to harden fully within the canal. (oosen andreseat it several times while it is still rubbery.

2. nce the resin has polymeri=ed, remove the pattern

6. orm the apical part of the post by adding additional resin andreseating and removing the post, ta4ing care not to loc4 it in thecanal.

8. Identify any undercuts that can be trimmed away carefully with ascalpel.

#he post pattern is complete when it can be inserted and removedeasily without binding in the canal. nce the pattern has been made,

additional resin is added for the core.


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Indirect procedureAn& elastomeri material 'ill ma(e ana$rate im#ression of the root anal if a 'ire

reinforement is #laed to #revent distortion)*) C$t #iees of orthodonti 'ire to len"thand sha#e them li(e the letter +

,) -erif& the !t of the 'ire in eah anal) It

sho$ld !t loosel& and e.tend to the f$ll de#thof the #ost s#ae)

/) Coat the se"ment 'ith tra& adhesive)

If s$%"in"ival mar"ins are #resent0 tiss$e

dis#laement ma& %e hel#f$l) L$%riate theanals to failitate removal of the im#ression'itho$t distortion 1die l$%riant is s$ita%le2)

3) Usin" a lent$lo0 !ll the anals 'ithelastomeri im#ression material)


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4) Seat the 'ire reinforement to the f$ll de#th of

eah avit&0 s&rin"e in more im#ression materialaro$nd the #re#ared teeth0 and insert the im#ression tra&)

5) Remove the im#ression0 eval$ate it0 and #o$r the!nal ast

Aess for 'a.in" is "enerall& ade6$ate 'itho$ttrimmin" or setionin" the ast)

7) Ro$"hen a loose8!ttin" #lasti #ost 1a #lastitooth#i( is s$ita%le2 and0 $sin" the im#ression as a"$ide0 ma(e s$re that it e.tends into the entire

de#th of the anal) 9) A##l& a thin oat of sti(& 'a. to the #lasti #ost

and add soft inla& 'a. in inrements)

It is %est to start from the most a#ial and ma(es$re that the #ost is orretl& oriented as it is

seated to ada#t the 'a.) :hen this #ost #attern has


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!$ A5!IA#I&


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#he core of a post-and-corerestoration replaces missing coronaltooth structure, and thereby forms

the shape of the tooth preparation.

ast metal cores

'lastic restorative material such as

amalgam, glass ionomer, orcomposite resins


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Plastic lling materials.

maximum tooth structure can be conservedbecause undercuts do not need to be

removed,

treatment requires one less patient visit

there are fewer laboratory procedures

testing generally shows good strengthcharacteristics, possibly because of the goodadaptation to tooth structure.

#he advantages of amalgam, glassionomer, or resinare that


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Disadvantages

orrosion of amalgam cores

the low strength of glass ionomer

the continued polymeri=ation and high thermal

expansion coe"cients of composite resin cores

%icrolea4age with temperature +uctuations?thermocycling@ is found to be greater undercomposite resin and amalgam cores thanconventional crown preparations

Di"culty may be encountered with certain operativeprocedures such as rubber dam or matrixapplication particularly on badly damaged teeth.


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Amalgam cores

Amalgam cores are suitable forrestoring posterior teeth, particularly

when some coronal structureremains


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Ste#8%&8ste# #roed$re for amal"am

/. Apply the rubber dam and remove gutta-percha from the pulp chamber as well as 0 to 2mm into each root canal if less than 2 mm ofcoronal height remains >se a warmedendodontic instrument.

0. !emove any existing restoration,undermined enamel, or carious or wea4eneddentin. $stablish the cavity form usingconventional principles of resistance andretention form.

1. If you suspect that the +oor of the pulpchamber is thin, protect it from condensingpressures with a cement base.


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2. it a matrix band.

6. ondense the rst increments of amalgam?select a material with high early strength@ intothe root canals with an endodontic plugger.

8. ill the pulp chamber and coronal cavity in the

conventional manner, 9. arve the alloy to shape. #he impression can

be made immediately.

Alternatively, the amalgam can be built up to

anatomic contour and later prepared for acomplete crown. >nder these circumstances caremust be ta4en to avoid forces that would fracturethe tooth or newly placed restoration


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Cast metal.

ast metal cores have the followingadvantages* they can be cast directly onto a

prefabricated post, giving a restorationwith good strength characteristics

conventional high-noble metal-content

alloys can be used an indirect procedure can be employed,

ma4ing restoration of posterior teetheasier.


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Direct procedure

/. >se a prefabricated metal or customacrylic resin post.

0. Add resin by the CbeadC technique, dippinga small brush in monomer and then into

polymer and applying it to the post. 7omerecommend light-cured resin to facilitate thisstep.

1. 7lightly overbuild the core and let it

polymeri=e fully2. 7hape the core with carbide nishing burs

or paper discs. >se water spray to preventoverheating of the acrylic resin. orrect any

small defects with wax.


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Indiret #attern for #osterior teeth

/.


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'rovisional restorations

#o prevent drifting of opposing orad3acent teeth


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Investin" and astin"

A cast post-and-core should t somewhatloosely in the canal.

A tight t may cause root fracture. #he

casting should be slightly undersi=ed asting a core onto a prefabricated post

avoids problems of porosity, but thepreheating temperature of the investment

mold should be restricted if recrystali=ationof the wrought post is to be avoided.


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Tr&8in

#he practitioner must be particularly carefulthat casting defects do not interfere withseating of the post, lest root fracture result.'ost-and-cores should be inserted with gentlepressure

#he shape of the foundation is evaluated andad3usted as necessary. &o ad3ustments shouldbe made immediately after cementationbecause vibration from the bur could fracturethe setting cement and cause prematurefailure


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ementation

It is important that the lutingagent ll all dead space within

the root canal system. oids maybe a cause of periodontalin+ammation via the lateral

canals. A rotary ?lentulo@ paste ller or

cement tube is used to ll the

canal with cement.


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Removal of e.istin" #osts

ccasionally an existing post-and-core must beremoved ?e.g., for retreatment of a failed rootcanal lling@.

If su"cient length of post is exposed coronally,the post can be retrieved with thin-bea4edforceps.

ibrating the post rst with an ultrasonic sealerwill wea4en the cement and facilitate removal

post puller

special hollow end-cutting tubes ?or trephines@


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restoration of endodontically treated tooth 97

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