Purpose of Root Canal Obturation and method of root canal obturation.doc

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Purpose of Root Canal Obturation and method of root canal obturation

IntroductionRoot canal obturation involves the three-dimensional filling of the entire root canalsystem and is a critical step in endodontic therapy. There are two purposes to

obturation: the elimination of all avenues of leakage from the oral cavity or theperiradicular tissues into the root canal system; and the sealing within the root canalsystem of any irritants that remain after appropriate shaping and cleaning of thecanals, thereby isolating these irritants. Pulpal demise and subseuent periradicularinfection result from the presence of microorganisms, microbial to!ins andmetabolites, and the products of pulp tissue degradation. "ailure to eliminate theseetiologic factors and to prevent further irritation as a result of continuedcontamination of the root canal system are the prime reasons for failure ofnonsurgical and surgical root canal therapy.

The importance of three-dimensional obturation of the root canal system cannot be

overstated, with the ability to achieve this goal primarily dependent on the uality ofcanal cleaning and shaping as well as clinical skill. #ther factors that influence theultimate success or failure of each case include the materials used and how they areused. The ultimate coronal restoration of the tooth following canal obturation mayloom as the most important goal, for there is reasonable evidence that coronalleakage through improperlyplaced restorations after root canal treatment andfailureof the restorative treatment or lack of health of thesupporting periodontium are thefinal determinants of successor failure in treatment.

Factors influencing complete obturation $uality of the cleaning and shaping of the canal system

%kill and e!perience of the clinician

&aterials and their usage

Restoration of the tooth

'ealth of the supporting periodontium

Characteristics of an Ideal Root Canal Filling(n ideal root canal filling three-dimensionally fills the entire root canal system asclose to the cemento-dentinal )unction as possible. &inimal amounts of root canal

sealers, most of which have been shown to be biocompatible or tolerated by thetissues in their set state, are used in con)unction with the core filling material toestablish an adeuate seal. Radiographically, the root canal filling should have theappearance of a dense, three-dimensional filling that e!tends as close as possible tothe cemento-dentinal )unction. These standards should serve as the benchmark forall clinicians performing root canal therapy, and it is only through a knowledgeableapproach to root canal treatment that uality assurance can be continuallydemonstrated in the obturation of root canal systems.

The ideal root canal filling3-D filling of the entire root canal space as close as possible to the cemento-

dentinal junction
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Radiographically dense fill ith absence of !oids

"hape reflecting a continuously tapered funnel that is appro#imately the sameas the e#ternal root morphology
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*hile a plethora of materials has been advocated over the last + years for rootcanal obturation, historically, gutta-percha has proven to be the material of choice forsuccessful filling of root canals from their coronal to apical e!tent. (lthough it is notthe ideal filling material, gutta-percha has satisfied the ma)ority of criteria for an idealroot filling material. The disadvantages of gutta-percha specifically, its

adhesiveness, lack of rigidity, and ease of displacement under pressure do notovershadow its advantages. /n light of its shortcomings, a sealer0cement is alwaysused with gutta-percha. 'owever, regardless of the delivery system or techniueused, neither gutta-percha nor sealer0cement alone enables standard-ofcare canalobturation. /n addition, the available materials and techniues do not routinelyprovide for an impervious seal of the canal system; all canals leak to a greater orlesser e!tent./t is recommended that clinicians master multiple obturation techniues and becomecompetent with various root canal sealers0cements, to be able to manage thediversity of anatomical scenarios that may be encountered.

Contemporary "ealers$Cements

The use of a sealer during root canal obturation is essential for success. 1ot onlydoes it enhance the possible attainment of an impervious seal, it also serves as afiller for canal irregularities and minor discrepancies between the root canal wall andcore filling material. %ealers are often e!pressed through lateral or accessory canalsand can assist in microbial control should there be microorganisms left on the rootcanal walls or in the tubules.%ealers can also serve as lubricants, enabling thoroughseating of the core filling material during compaction. /n canals in which the smearlayer has been removed, many sealers demonstrate increased adhesive propertiesto dentin in addition to flowing into the patent tubules. ( good sealer should bebiocompatible and well tolerated by the periradicular tissues, and although all sealerse!hibit to!icity when freshly mi!ed, their to!icity is greatly reduced on setting and all
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are absorbable when e!posed to tissues and tissue fluids. %ubseuent tissuehealing or repair generally appears unaffected by most sealers, provided there areno adverse breakdown products of the sealer over time. /n particular, the breakdownproducts may have an adverse action on the proliferative capability of periradicularcell populations. %ome clinicians consider that a small puff of root canal filler

e!tending beyond the working length is indicative of a fully obturated canal spacewith a well-sealed apical constriction. 2!cessive sealer should not be routinelyplaced in the periradicular tissues as part of an obturation techniue.

%ealers0cements can be grouped based on their prime constituent or structure, suchas 3inc o!ide-eugenol, polyketone, epo!y, calcium hydro!ide, silicone, resin, glassionomer, or resin-modified glass ionomer. 'owever, many of the sealers0 cementsare combinations of components, such as 3inc o!ideeugenol and calciumhydro!ide,45 with the addition of calcium hydro!ide claimed to create a therapeuticmaterial that can be inductive of hard tissue formation.2po!y-based andmethacrylate-based resin sealers that can be bonded to the root canal dentin 6but

not to gutta-percha7 are also now available.%ealers should be mi!ed to a creamy consistency, allowing them to adhere to themaster cone and not ball up at the shaft of the cone, leaving the gutta-perchae!posed. The sealer should adhere to the cone evenly along its length and at theend of the cone. 8linicians should read the product insert and material safety datasheet for each product chosen before using it.

Contemporary Core Filling %aterials9utta-percha is the standard material of choice as a solid core filling material forcanal obturation. /t demonstrates minimal to!icity and minimal tissue irritability, is theleast allergenic material available when retained within the canal system,and incases of inadvertent gutta-percha cone overe!tension into the periradicular tissues,is well tolerated provided the canal is clean and sealed. 8hemical solvents havebeen used for almost + years to soften gutta-percha, with methods ranging frommerely dipping the gutta-percha cones into the solvent for one second for bettercanal adaptation, to creating a completely softened paste of gutta-percha with thesolvent. %olvents used have included chloroform, halothane, rectified whiteturpentine, and eucalyptol. Periradicular tissues may be irritated if the solvent ise!pressed beyond the canal or significant amounts of softened gutta-percha areinadvertently placed into the periradicular tissues. "ailure to allow for dissipation ofchemical solvents, if volatile, or the removal of e!cess solvent with alcohol can result

in significant shrinkage and possible loss of the apical seal. The use of chemicalsolvents has been both praised and uestioned, but with the advent ofthermoplastici3ed gutta-percha, the need to consider the use of solvents at any timemust be uestioned. The use of solvents, however, may still be considered for anumber of challenges the clinician may face in daily practice, such as the customfitting of master cones in irregular apical preparations or following ape!ification.

&utta-percha ConesThe composition of gutta-percha cones is appro!imately + to


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percentages of gutta-percha and 3inc o!ide. The antimicrobial activity of gutta-percha is also primarily due to the 3inc o!ide.

The cones are manufactured in both standardi3ed and nonstandardi3ed si3es. Thestandardi3ed si3es coordinate with the /%# root canal files si3es + through +4 and

are used primarily as the main core material for obturation. They generally have a


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/n particular, for techniues that use vertical compaction of heat-softened gutta-percha, both the non-standardi3ed and more tapered cones have become uiteacceptable. 8ustom cones can also be developed for canals with irregular or large

apical anatomy, #ver time, numerous methods have been advocated for obturatingthe prepared root canal system, each with their own claims of ease, efficiency, orsuperiority. &ost contemporary techniues still rely on gutta-percha and sealer toachieve their goal. "our basic techniues e!ist for the obturation of the root canalsystem with gutta-percha and sealer

('( the cold compaction of gutta-percha) *+( the compaction of heat-softenedgutta-percha ith cold instruments

Cold compaction carrier ,eated compaction Presoftened core
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until it has cooled; 657 the compaction of gutta-percha that has beenthermoplastici3ed, in)ected into the system, and compacted with cold instruments;and 647 the compaction of gutta-percha that has been placed in the canal andsoftened through the continuous wave techniue 68alamus7. ( multitude ofvariations on these four basic themes e!ists. "or in)ectable thermoplastic obturationtechniues, gutta-percha may come in either pellet forms or in cannulae.

Cold compaction carrier ,eated compaction Presoftened core

1o single techniue has proven to have statistically significant superiority whenconsidering both in vitro and in vivo studies, as the success of all techniues ishighly dependent on the cleaning and shaping of the canals and the clinicianAse!pertise in the use of a particular techniue.*hile many have advocated the use ofthe lateral compaction techniue or a single cone fill 6monocone7 to achieve a ualityapical seal, the techniue in itself does not necessarily favor the filling of canalirregularities.@5 Recogni3ing this, use of a softened gutta-percha techniue with heator chemical softening is reuired to achieve a thorough obturation.
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/n addition, while filling the entire root canal system is the ma)or goal of canalobturation, a ma)or controversy e!ists as to what constitutes the apical termination ofthe root canal filling material. *orking length determination guidelines often cite thecemento-dentinal )unction or apical constriction as the ideal position for terminatingcanal cleaning and shaping procedures and placing the filling material. 'owever, the

cemento-dentinal )unction is a histologic and not a clinical position in the root canalsystem and, in addition, the cemento-dentinal )unction is not always the mostconstricted portion of the canal 6yellow arrows7 in the apical portion of the root

8ontemporary practices of obturation favor material softening even this does notguarantee that an impervious seal of the root canal system will be established. (lso,with softened gutta-percha obturation techniues there has been a greater incidenceof material e!trusion beyond the confines of the canal. *hile softening of gutta-percha may be viewed as routinely desirable, the selective use of this techniuesolely or in combination with a solid core of gutta-percha must be at the discretion ofthe competent clinician when anatomy dictates this approach.

pical constriction of root canal

Recent research conducted at 1ova %outheast Bniversity using micro 8T scanningtechnology has shown the effectiveness of scanning for imagery and the greater

precision observed compared to standard radiographs. /n one e!ample, amesiobuccal canal was filled using 9TC %eries DE obturator and the mesiolingualcanal was filled using a single cone techniue 6(ctiF 9P7. /t appeared from oneangle that all canals were eually filled.

Radiograph of filled canals
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'owever, closer e!amination subseuent to filling showed voids using the singlecone techniue throughout the length of the root filled using this techniue. Thesingle cone techniue did not produce a monoblock obturation. The gutta-perchafrom the 9T obturator flowed into the canal isthmus and filled it.

.oids using single cone techni/ue
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Cross-section ith cti. &P and &T "eries 0 obturation

cti! . &P &T "eries 0 obturator

Canal isthmus filled ith &T obturator gutta-percha
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Gifferences in obturation techniues and results are also more observable using 8Tscanning than using traditional radiographs.8ontemporary techniues include theuse of bonded root canal filling materials. Recent developments in resin-bonding

have led to the availability of resin cones and pellets similar in shape and si3e togutta-percha materials.Resin-based cones containing methacrylate resin, fillers, bioactive glass, andpolymers are available that can be handled similarly to gutta-percha and can beused with a lateral or vertical compaction techniue. Resin-based materials can alsobe delivered via a heated syringe 6#btura gun, %partan #btura7. %ince resin-basedmaterials reuire a slightly moist environment, it is important to avoid using anydessicating solutions, such as alcohol, during root canal preparation. "urther, ifsodium hypochlorite or pero!ide was used during root canal preparation, this mustbe thoroughly removed prior to using a resin-based material as it would reduce theability of the resin material to bond. %imilarly, the smear layer must also bethoroughly removed.

Prefabricated Obturators

9utta-percha can also be formed on a plastic carrier or corecarrier. Prefabricatedobturators were first described in +>? by *illiam =en Hohnson.> The prototype forthe obturator had been prenotched I-files wrapped in gutta-percha 6hand formed7that were then heated over a flame until the surface glistened and e!panded. Theseprenotched JobturatorsK were inserted into the canal and apical pressure appliedwhile the handle was twisted off.

Prototype obturator
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Prefabricated obturators were introduced in +?? 6Thermafil7 using first a stainlesssteel and subseuently a titanium core, coated with gutta-percha. Plastic obturatorswere first offered in +


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8urrent plastic obturators are available in a nonvented shape with a taper of around.4 6Gensfil7 and a vented shape with the same taper 6Thermafil Plus7. =oth arebiologically inert. The carrier is thick with a thinner outer coating of gutta-percha,which helps to reduce material shrinkage as the gutta-percha cools in the canal. (vented prefabricated obturator helps the flow of gutta-percha during placement andalso aids in retrieval of the obturator should retreatment be necessary."or si3es 4 and below in the Thermafil series, an insoluble liuid crystal plastic isused. "or si3e 4 and above soluble polysulfone polymer is used. (ll of these use asi3e verifier to help select the correct si3e obturator, as do ProTaper Bniversalcarriers, which start at a .4 taper. %ystems that do not use a si3e verifier include thePro%ystem 9T carriers and 9T %eries D carriers, which are made in a variety oftapers between .4 and .+

Purpose of Root Canal Obturation and method of root canal obturation.doc

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