State of the Art and Science of Endodontics

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2005;136;41-52J Am Dent Assoc

SCIENTIFIC AFFAIRS COMMITTEEENDODONTICS RESEARCH ANDAMERICAN ASSOCIATION OFOF AND CONSULTANTS TO THESHAHROKH SHABAHANG and MEMBERSState of the art and science of endodontics

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State of the art andscience of endodontics

SHAHROKH SHABAHANG, D.D.S., M.S., Ph.D.;AND MEMBERS OF AND CONSULTANTS TO THEAMERICAN ASSOCIATION OF ENDODONTICSRESEARCH AND SCIENTIFIC AFFAIRS COMMITTEE

The past 10 years have witnessed significantchanges in the art and science of endodontics.The advances in the science of this specialtyhave allowed for better understanding ofendodontic disease processes and have led to

development of treatment modalities aimed at restoringhealth to the pulp and periradicular tissues. Technolog-ical discoveries in instruments and materials have madeit possible to achieve treatment objectives that once

were considered unattainable. Thisarticle reviews the advances in endodon-tics during the past decade, focusing on

both basic and clinical research.

BASIC RESEARCH

The microbial nature of endodonticdisease. While the mechanical andmanual challenges of root canal dbride-ment and obturation remain, it hasbecome increasingly clear that thelargest proportion of endodontic disease,both pulpal and periradicular, is due tothe presence of microorganisms. There-fore, treatment success is related very

closely to the ability to remove theseirritants and to prevent reinfection.The polymicrobial nature of endo-

dontic infections contributes to the increased overallbacterial irritation that is associated with the develop-ment of certain virulent bacterial combinations.1-3 Thepresence of certain microorganisms, such as members ofthe black-pigmented gram-negative bacteria, in rootcanals of teeth with necrotic pulp has been associatedwith increased clinical symptoms.4-6

Development of DNA- and RNA-based microbiologicaltechniques has allowed researchers in endodontics to

ABSTRACT

JADA, Vol. 136, January 2005 41

A better

understandingof the

pathogenesis

of pulp and

periradicular

diseases will

improve

patient care

and result in

preservation of

natural tissues.

JA D A

C

O

NT

INU

ING E DU

CAT

IO

N

R E S E A R C H

Background.Advances in the art and

science of endodontics have

facilitated better under-

standing of disease pro-

cesses and have led todevelopment of treat-

ment modalities aimed to

restore health to the pulp

and periradicular tissues.

This article presents a summary

of both basic and clinical breakthroughs

in endodontics.

Results. The author indicates that, on

the basis of the reviewed literature, pulp

and periradicular diseases are primarily

microbial. Basic research has led to devel-

opment of methodologies that have allowedfor specific and accurate identification of

pathogens that are likely to cause persis-

tent infections. Close examination of clin-

ical data shows that meticulous dbride-

ment of the infected root canal system will

result in a high probability of successful

treatment outcome. Progress in visualiza-

tion, mechanical and chemical disinfection,

and biological seal of portals of entry will

improve quality of care further.

Conclusions and Clinical

Implications.A better understanding of

the pathogenesis of pulp and periradicular

diseases, inflammation and healing, as well

as of pain pathways, will improve patient

care and result in preservation of natural

tissues.

Key Words. Endodontics; endodontic

technology; basic endodontic research.

ARTICLE

1

JA D A

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identify new species of bacteria7,8 andto develop a more elaborate descrip-

tion of the microbial diversity in rootcanal infections.9,10 Owing toincreased sensitivity and the abilityto detect uncultivable microorgan-isms, researchers identified severalfastidious or uncultivable microor-ganisms in root canal infections,using techniques based on the poly-merase chain reaction to amplify thebacterial 16S rRNA gene.8

Researchers cultured gram-positive bacteria, particularlyEntero-

COVER STORY

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coccus faecalis, from the root canals of teeth withpersistent periradicular lesions.11-13 Furthermore,other researchers cultured fungimostlybelonging to the genus Candidafrom nearly7 percent of retreatment cases that have cul-

tivable microorganisms.14 It is not yet clearwhether these microorganisms cause the treat-ment failure or are favored by the environment ofpreviously treated root canals.

The endodontic literature has devoted muchattention to the question of whether microorgan-isms are present within periradicular lesions.Techniques using in situ staining methods haverevealed the presence of bacteria, mainlybelonging to the genusActinomyces, in sometherapy-resistant cases.15 Usingcareful sampling techniques,

researchers have detected bacteria16or bacterial DNA17,18 in periradicularlesions. More recently, researchershave linked symptomatic periradic-ular lesions to an increased preva-lence of human cytomegalovirus andEpstein-Barr virus.19

Inflammation of the pulp.Inflammation of the dental pulp is abasic biological response that takesplace in a unique low-compliance environmentand is the result, at least initially, of bacterial

toxins acting well in advance of any direct micro-bial invasion. The initial innate component of theresponse is largely vascular and due to therelease, initiated by cytokines and mediators, ofneuropeptides20,21 from the multitude of pulpalnerves via axon reflexes.22A three-dimensionalstudy has revealed widespread anastomoses andloops23 that help limit the potentially damagingsequelae of inflammation. In this regard, exami-nation of a microvascular study24 showed clearlythat mechanisms in the capillary bed limit thedangers of increasing tissue fluid pressure such

that capillary collapse occurs only at a late stagein untreated inflammation. Researchers also havemapped out the immunological component of thetissue response in detail,25 starting with antigen-presenting cells that greet the penetrating irri-tants as they reach the odontoblastic layer andculminating in nonspecific and specific responsesby phagocytes and lymphocytes, respectively.

Inflammation and infection of the periradiculartissues are an extension of the processes in thepulp but are not identical to them. What practi-tioners detect most often clinically is bone resorp-

tion. Hard-tissue dissolution is not a character-istic of pulpal inflammation. The periradicularlesion has proven to be a productive model for thestudy of inflammatory resorption.26,27 Cliniciansnow have detailed descriptions of the inflamma-

tory cascade of cytokines released by bacterialtoxins from macrophages and neutrophils, andthe recognition of a group of these cytokines(interleukin-1 alpha, interleukin-2 beta, trans-forming growth factor-1 alpha, transforminggrowth factor-2 beta) as the osteoclast-activatingfactor is an important advance.

For most patients, pain is the most obvious andimportant characteristic of inflammatory disease,and especially so when it is within the tooth.

During inflammation, intrapulpalnerves sprout and gather increased

amounts of neuropeptides20 andrelease transmitters in response tostimulation by cytokines.21A- fiberterminals, in dentin responding tohydrodynamic stimuli, and C fibers,in pulp responding to inflammatorymediators, appear to have differen-tial roles in pulpitis.28A relation-ship between symptoms and inflam-matory molecules has been

demonstrated in all studies reporting the signifi-cance of substance P.29-31 Inflammation and regen-

eration are closely related. The repair potential ofthe dental pulp is well-known, and recent workusing growth factors suggests that modulation ofthese proteins will be of great value in extendingthe range of pulpal repair procedures.32,33

CLINICAL RESEARCH

Treatment outcomes. The most recent dataindicate that about 15.8 million primary endo-dontic procedures were performed in the UnitedStates in 1999.34 Maintenance of the natural den-tition, aided by endodontic, periodontal and

restorative procedures, is the preferred choice ofpatients and remains a predictable treatmentplan. From the patients perspective, retention ofa tooth in a functional and esthetic condition maybe considered a favorable treatment outcome. Onthe other hand, endodontists use more rigorousstandards to assess treatment outcomes. Suc-cessful treatment to the specialist generally issignified by clinical and radiographic absence ofdisease. Researchers have reported outcome datain the endodontic literature as complete healing,incomplete healing or an absence of healing. Com-

42 JADA, Vol. 136, January 2005

R E S E A R C H

Inflammation andinfection of the

periradicular tissues

are an extension of

the processes in

the pulp but are not

identical to them.


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plete restoration to health may be expected in 80percent35,36 to more than 95 percent37 of cases,depending on the observation period. It is impor-tant to note that while signs of initiated, butincomplete, healing may be visible in early follow-

up periods, complete resolution of preoperativeradiolucent lesions may require up to four yearsof healing time.38 Overall, the criteria used forreporting endodontic treatment outcomes are dif-ferent from and more rigorous than those used toreport the survival rates of implants.

Evidence-based endodontics. Clinical deci-sion making is becoming more complex today andrequires information from many sources: primarydata and patient preferences, the clinicians ownclinical and personal experiences, external rulesand constraints, and scientific evidence. There

also has been an explosive increase in the amountand quality of laboratory and clinical evidence.Fortunately, mechanisms such as systematicreviews are emerging that will help us acquirethe best, most compelling and most current evi-dence that addresses defined clinical questions.

In 1999, the American Association of Endodon-tists (AAE) Board of Directors elected to use anevidence-based approach to its decision makingand embrace lifelong learning as an essential ele-ment in the practice of the highest standards ofendodontics. Trained AAE members, active in

education and research, conducted systematicreviews in selected topics that were reported atthe 2002 AAE Annual Session in Chicago. Theorganization established an Evidence-basedEndodontics Standing Committee to consideraction on the following recommendations:dconstruction of a critically approved databaseof identified articles;ddevelopment of an electronic journal from thedatabase;dcontribution to other databases such as theCochrane Collaboration;d

continued training of reviewers to conduct sys-tematic reviews on additional clinical questions;dcreation of a standardized report-writingformat;drevision of the standards of the AmericanDental Association Commission on Dental

Accreditation to include instruction in conductingsystematic reviews.

CLINICAL PRACTICE

Diagnosis.Accurate and efficient diagnosis isthe cornerstone of endodontic therapy. Experi-

enced clinicians long have recognized that thepatients chief complaint and history of illness arethe first, and arguably the most, important piecesof the diagnostic puzzle. Some investigators viewhistory of moderate-to-severe pain as a good indi-

cator of irreversible pulpal pathosis.39 Nonethe-less, clinical signs and symptoms alone are unreli-able predictors of pulp and periradiculardiseases.40,41 Thermal (cold and heat) and elec-trical pulp testing (EPT) are simple tests but arenot completely reliable. Heat as a pulp test has arelatively high sensitivity but is the least accu-rate overall of the three common pulp tests owingto low specificity.42 Cold testing withtetraflouroethane, ethyl chloride or carbon dioxide(CO2) snow is relatively reliable and generallymore accurate than heat. Cold testing is pre-

sumed to be more reliable than EPT in teeth withincomplete root formation. Since thermal testsare not 100 percent accurate, EPT is especiallyuseful for confirming a questionable pulpaldiagnosis.

A major limitation of thermal testing and EPTis that these tests measure only pulpal nerveresponse, not pulpal blood flow. Since the truemeasure of pulp vitality is blood flow, laserDoppler flowmetry (LDF) and pulse oximetrydevices have been adapted for experimental usein assessing pulp vitality.43-46 These devices seem

particularly well-suited for evaluating the vitalityof traumatized teeth and for evaluating teeth inareas that may require orthognathic surgery.47

Some investigators have attempted to identifybiological factors that may determine the healthstatus of the pulp tissue more accurately.48,49 Iden-tification of the 20,000 to 25,000 genes of thehuman genome has paved the way for associationof specific genes with known pathological find-ings. Microarray technology has enabledresearchers to identify and study a large array ofgenes and proteins that are affected during dis-

ease formation and healing.

50,51

Canal instrumentation. The goals of dbride-ment are to remove irritants from the root canalsystem and to create a three-dimensional shapethat can be obturated.52 Nickel titanium (NiTi)files have become a mainstay in most endodonticprocedures. Thanks to this metal, practitionerscan use rotary instruments effectively in curvedcanals. Many file designs and shapes can be usedfor dbridement. Varying the taper of the instru-ment leads to a more efficient preparation of theroot canal space. Many of these types of files fea-


R E S E A R C H


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ture a U-shaped groove and a radial land thathelps prevent perforations and instrumentlocking and separation. They also usually have anoncutting tip that helps to decrease transporta-tion of the canal space.

While it can reduce the bacterial count signifi-cantly, mechanical dbridement does not disinfectthe root canal system completely.53 Thus, a rootcanal irrigant is needed to aid in the dbridementof the canals. Sodium hypochlorite (NaOCl) is themost commonly used root canal irrigant. How-ever, NaOCl has some major short-comings, including its inability toremove the smear layer54,55 and tokill all bacteria present in infectedroot canals.12,56,57 Recently, a mix-ture of a tetracycline isomer, an

acid and a detergent known asMTAD has been introduced as afinal rinse for disinfection of theroot canal system. This irrigant isable to remove the smear layersafely,55 and it is a more effectivedisinfectant than NaOCl evenagainst resistant bacteria such asE. faecalis.58,59

Obturation: new delivery systems andimportance of coronal restoration.Researchers have attributed failure of root canal

therapy largely to incomplete obturation of theroot canal system.60After proper cleaning,shaping and disinfection of the root canal system,proper filling of the canal is necessary to preventreinfection. There are two basic methods of rootcanal obturation, with a number of permutationsto these techniques. The lateral condensationtechnique requires lateral compaction of coldgutta-percha points to fill the space. Warm gutta-percha techniques, also called vertical com-paction techniques, use warm gutta-percha thatis made plastic and compacted apically. Both

techniques require addition of a cementlike sealerthat adheres to the dentin walls and fills anyspace not obliterated by the gutta-percha. Prop-erly prepared canalscleaned, disinfected andtapered in shapealso should be cleared of thesmear layer. This can be achieved by using a com-bination of ethylene diamine tetra-acetic acid andNaOCl or MTAD.

Variations of the techniques described previ-ously use newer devices, which are equippedwith a heated spreader/plugger that warms thegutta-percha and acts as a plugger to compact

the plasticized mass. Use of solid-core carrierssuch as Thermafil (Dentsply Tulsa Dental,Tulsa, Okla.) is another accepted method ofobturating root canals. By this method, a centralcarrier coated with alpha-phase gutta-percha is

warmed and plasticized in a special oven andinserted to the appropriate depth in theprepared canal.

An apical third obturator acts as a terminalplug at the apical portal of exit. The plug can bemade up of dentin chips formed from the cleaned,

shaped and disinfected canal walls.Not only does the plug preventoverfilling, but also dentin chipscan stimulate the formation of acementumlike cap over the apex.61

Calcium hydroxide62 and mineral

trioxide aggregate (MTA)63 also canbe packed as an apical plug. Theremainder of the canal space can befilled using sealer and a gutta-percha gun such as Obtura II(Obtura Spartan, Fenton, Mo.).

The lack of a coronal seal is animportant factor in the develop-ment of periradicular lesions fol-lowing root canal therapy.64 There-

fore, it is important to prevent coronal leakageafter completion of root canal therapy.

A number of studies have investigated the lossof the provisional restoration to determine howlong it takes for coronal leakage to adverselyaffect the root canal seal.65-68 In one study, leakageoccurred in as little as three days time.65 By day19 in another study, more than 50 percent of theroot canals were completely contaminated,66 andby day 30 in a third study, all canals without acoronal seal were contaminated.68 While the pres-ence of a temporary restoration may retard thisprocess, this protection is short-lasting and a sub-stantial change occurs between 28 and 90 days

after placement of a temporary restoration.

67

The loss of a provisional coronal access restora-tion most likely results in a compromised rootcanal seal sometime during the first month ofexposure to oral contaminants. Should there bean extended period between the completion ofendodontic therapy and definitive restorative orprosthodontic care, then a definitive restorationshould be placed in the most coronal portion ofthe access opening.

Adjuncts. Operating microscopes. Perhaps noarea of endodontic practice has met with more


R E S E A R C H

The loss of a

provisional coronal

access restoration

most likely results ina compromised root

canal seal sometime

during the first month

of exposure to oral

contaminants.


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excitement and controversy in the past decadethan the introduction of the operating microscope(OM) to clinical practice. In less than 10 years,the OM has progressed from a novelty item to arequired training standard for specialty education

in endodontics.The OM is used most commonly to assist in

retrieving separated instruments, locating andnegotiating calcified canals, and providing sur-gical root canal treatment.69 Proponents of OMsfeel strongly that they allow for more efficient andsafe treatment of teeth that otherwise might beuntreatable or treatable only with great difficulty.There is some evidence that the use of OMs incombination with operator skill, prudent caseselection, and other current technology andmaterials may lead to improved surgical treat-

ment outcomes70 and the location of additionalcanals.71,72 Endoscopes, orascopes and magnifyingloupes with or without a supplemental lightsource also can be employed to enhance visualiza-tion of the operative field.73,74

Ultrasonic devices. Ultrasonic devices havebecome essential tools for assisting in the removalof posts and separated instruments, as well asroot-end preparation during surgical treatment ofroot canals.75 Since heat is a byproduct of theenergy generated by ultrasonic instruments, it isimportant to use a water coolant spray and to

operate at the lowest setting possible consistentwith the task (root-end preparation, for example,is a delicate procedure and requires a lower set-ting than do post removal applications). Manyspecially designed ultrasonic tips are availableand suitable for specific situations such aspreparing root ends, removing posts, removinginstrument fragments and searching for calcifiedcanals. Ultrasonic tips specially designed for root-end preparation allow for conservative and pre-cise preparation of the root end during apicalsurgery.

Electronic apex locators. The task of deter-mining canal length has moved into a new andmore precise era with the rapid evolution of elec-tronic devices that measure the length of the rootcanal. The first- and second-generation apex loca-tors were more difficult to use and more prone toerroneous readings than are the third-generationdevices now available.

Research and clinical experience support theclaim that apex locators can assist accurately indetermining canal length in the majority ofcases.76-78Apex locators also can be used to detect

perforations and root fractures. The use of elec-tronic apex locators is contraindicated in patientswith cardiac pacemakers, although the actualrisk to these patients is uncertain.79

Lasers. Lasers have various applications in

endodontics such as measuring pulp vitality,80

treating dentinal hypersensitivity,81 preparingand disinfecting root canals,82,83 and performingapical surgery.84

Reports about these applications are con-flicting, owing to the use of different types oflasers, energy levels and specimens used. LDFhas the most promising application in endodon-tics. LDF was developed to assess blood flow inmicrovascular systems.85 The reliability of con-ventional pulp tests can vary in newly eruptedand traumatized teeth, owing to incomplete for-

mation or trauma to the neural pulpal compo-nent, respectively. LDF techniques are sensitiveand accurate for pulp vitality testing becausethey reflect vascular rather than nervous respon-siveness when compared with other methods.44

LDF is a useful research instrument, but a prac-tical clinical device still is lacking.

The neodymium:yttrium-aluminum-garnet(Nd:YAG) laser is the most popular system forcleaning and shaping the root canal system,because the device offers a thin fiber-opticdelivery system for entering narrow root canals.

Lasers can remove the smear layer and debris;however, it is difficult to clean all root canal wallswith these devices, because the linear emission ofthe laser beam makes it almost impossible to irra-diate the lateral canal walls and leaves themrough and uneven. Root canal spaces rarely arestraight; more often, they are curved in at leasttwo dimensions. For lasers to be useful inendodontics, it is necessary to improve the fibertip and the method so that the laser irradiates allareas of root canal walls. Several studies haveevaluated the sterilization of root canal systems

by means of CO286

and Nd:YAG lasers.

87

Althoughlasers used at high power have a bactericidaleffect, that effect is dependent on each laser. Fur-thermore, using lasers to disinfect root canals isproblematic, since it can inflict thermal injury onperiodontal tissues.

Despite lasers approval for dental proceduresby the U.S. Food and Drug Administration, moreresearch is required to develop lasers for use inendodontics and to compare their efficacy withthat of present treatment modalities.


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SPECIAL CASES

Nonsurgical retreatment (indications versussurgery). Despite the availability of advancedtechnological tools and better understanding ofthe biology of pulp and periradicular diseases,clinicians often need to address posttreatmentendodontic disease.88 Before commencing withany treatment, clinicians must consider all inter-

disciplinary treatment options in terms of time,expense, prognosis and patient satisfaction. If thechoice is endodontics, then the goal of nonsurgicalretreatment is to remove materials from the rootcanal space and to address any deficiencies orrepair defects that are pathological or iatrogenicin origin.89 Many significant advantages resultwhen endodontically failing teeth are re-enterednonsurgically. Endodontic access provides theopportunity to evaluate teeth for coronal leakage,fractures and missed canalsand importantly,after disassembly procedures, these root canal

systems can be three-dimensionally cleaned,shaped and obturated (Figure 1).90Advancementsin the field of nonsurgical endodontic retreatmentare related directly to the introduction of thedental OM, ultrasonic technology and relatedinstruments, NiTi rotary shaping files and MTA.91

Nonsurgical retreatment of failed cases has asimilar success rate to that of initial conventionaltreatment if the cause of failure is identified andcorrected.92

Perforation repairs. Historically, the occur-rence of perforations during root canal treatment

has reduced the long-term prognosis of theaffected tooth significantly. The poor prognosis ofperforations is mostly due to bacterial leakage orthe lack of biocompatibility of the repair materi-als used.93 The important steps in the manage-

ment of a furcal perforation are immediate treat-ment, adequate isolation, dbridement andsealing of the defect.94 Discovery of new materialssuch as MTA95,96 has significantly improved theprognosis for what once were considered hopelessteeth.97

Trauma and management of open apexes.Traumatic injuries in young patients present aspecial challenge during endodontic treatment interms of diagnosis and treatment planning, aswell as of managing the open apex. Wheneverpossible, the goal should be preservation of pulp

vitality to allow continued development alongthe entire root length.98 MTA has the most desir-able properties for this purpose99 because it pro-vides a good seal,100 is biocompatible101 andinduces hard-tissue formation.102 If the pulp isnecrotic, the treatment of choice is root canaltherapy.103 However, in an immature tooth, com-pletion of root canal therapy must be delayeduntil root-end closure has been completed.104

Long-term calcium hydroxide therapy no longeris the treatment of choice because of the vari-ability of its treatment outcomes and its adverse

effects on dentin.105

Researchers have advocatedplacement of an artificial barrier as an alterna-tive to long-term apexification procedures.62,106,107

More recently, MTA has been shown to inducehard-tissue formation more predictably than cal-cium hydroxide (Figure 2), while bioactivematerials such as bone morphogenetic proteinshave demonstrated no added advantage over cal-cium hydroxide.63

Evaluation of healing of intra-alveolar rootfractures in patients between the ages of sevenand 17 years suggests that 77 percent of these

cases heal by means of development of a hard-tissue fragment, development of periodontal liga-ment or a combination of the two.108 Pulp vitality,degree of tooth development, presence or absenceof response of the pulp to stimuli, type of injury,amount of diastasis between the fragments andefforts to reposition the displaced fragments havean influence on healing.108 However, the efficacyof long-term splinting is questionable.108

To prioritize treatment of traumatic injuries,treatment delivery has been divided into threegroups109: acute (treatment rendered within a few


R E S E A R C H

Figure 1. Nonsurgical retreatment allows for three-

dimensional dbridement and obturation of the rootcanal system.


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hours), subacute (treatment rendered within thefirst 24 hours) and delayed (treatment renderedafter the first 24 hours). A survey of theavailable literature suggests the followingrecommendations:dcrown and crown/root fracturessubacute ordelayed treatment;droot fracturesacute or subacute treatment;dconcussion and subluxationsubacutetreatment;dextrusion and lateral luxationacute or suba-cute treatment;dintrusionsubacute treatment;davulsionacute treatment if the tooth is notreplanted at the time of injury, subacute treat-ment otherwise;dprimary tooth injurysubacute treatment,

unless the primary tooth is displaced into the fol-licle of the permanent tooth or occlusal problemsare present, in which cases acute treatment isnecessary.

Surgical root canal therapy. Endodonticsurgery is not oral surgery in the traditionalsense. Rather, it actually is endodontic therapyperformed through a surgical flap. The main pur-pose of performing periradicular surgery is toremove a portion of a root with undbrided canalspace or to seal the canal when a complete sealcannot be accomplished through a coronal

approach. With recent improvements in surgicalinstruments, materials and techniques,endodontic surgery can provide a second chanceto retain a tooth that otherwise would beextracted. Endodontic surgery may be necessaryto address anatomical complexities and pro-cedural complications associated with difficultnonsurgical cases.110-113 The OM is the latest addi-tion to this armamentarium, providing up to 32magnification of the surgical field.114,115 The quan-tity and quality of light in the working field is asimportant as magnification. The coaxial lighting

and improved optics of an OM provide better dis-tinction between tooth and bone. Identifyingminute canal openings, incipient fracture linesand other important anatomical findings becomesroutine with the OM. For example, an isthmusfrequently runs between two canals in themesiobuccal root of the maxillary first molar.116,117

These small communications contain pulp tissueremnants and should be included in root-endcavity preparations and fillings during endodonticsurgery.118 The magnification and illuminationafforded by the OM facilitates identification of

these ramifications, allowing them to be preparedand filled with the main canals (Figure 3).

Enhanced magnification necessitates miniatur-ization of endodontic surgical instruments.Microscalpels, piezoelectric ultrasonic handpieces,surgical micromirrors and microsurgical irriga-tors, together with miniature carriers, condensersand pluggers, have been developed to accommo-

date the high level of magnification used rou-tinely in endodontic surgical procedures.The miniaturized instruments allow more pre-

cise performance of surgical procedures. Forinstance, the root-end preparation is aligned par-allel to the long axis of the root using speciallydesigned ultrasonic tips to a depth of 3 mm.119Avariety of root-end filling materials can be used,which include Super EBA (Harry J. Bosworth,Skokie, Ill.), intermediate restorative material,dentin bonding agents and, most recently,MTA.118,120,121 The materials should be biocompat-


R E S E A R C H

Figure 2. A. Radiograph demonstrating a mandibular pre-molar with an incompletely developed root and an openapex. B. Radiograph demonstrating formation of a hard-tissue barrier at the root end of the premolar after treat-ment with mineral trioxide aggregate as an apical plug.

B

A


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ible, provide a hermetic seal and, ideally, stimu-

late hard-tissue growth. MTA provides a superiorapical seal compared with other root-end fillingmaterials and is not adversely affected by bloodcontamination. In several studies, histologicsections demonstrate the regeneration of newcementum over the MTA root-end filling (Figure4), a phenomenon that is not seen with other com-monly used root-end filling materials.

Clinical controversy: the smear layer.Studies have shown that current methods ofcleaning and shaping root canals produce a smearlayer that covers the instrumented walls.54,122-125

The smear layer contains inorganic and organicsubstances that include fragments of odonto-blastic processes, microorganisms and necroticmaterials.

Proponents of smear layer removal claim that

the presence of a smear layer can inhibit or signif-icantly delay penetration of antimicrobial agentssuch as intracanal irrigants and medications intothe dentinal tubules.126,127 Furthermore, removalof the smear layer may significantly improveadhesion of obturation materials to the canalwalls128-132 and reduce microleakage.132-137

While some investigators have reported thatthe removal of the smear layer does not have anysignificant effect on microleakage of rootcanals,138-140 the opponents of smear layer removalhave shown an increased level of leakage through

the obturated root canals141 with a 10- to 80-micrometer depth of penetration.142-146

Despite controversy regarding the effect of thesmear layer on the quality of instrumentationand obturation, it should be noted that the smearlayer itself may be infected and may protect thebacteria already present in the dentinaltubules.54,147,148 Because of these concerns, it maybe prudent to remove the initially created smearlayer from infected root canals and allow penetra-tion of intracanal medications into the dentinaltubules of these teeth. After disinfection of the

root canal system, the smear layer can be recre-ated. Chemical, mechanical and laser means canbe used to remove the smear layer.

Management of pain, infection and anx-iety. Considerable advances have occurred in themanagement of pain, infection and anxiety in theendodontic patient.

Pain. Survey studies indicate that only about40 percent of patients report pain after nonsur-gical root canal therapy, with about 20 to 25 per-cent reporting moderate-to-severe pain.149 Thus,the clinician should tailor pain management

strategies to each patient. A survey of endodonticclinical trials indicated that the presence of preop-erative pain or a positive response to percussion isa consistent predictor of patients most likely toreport postendodontic pain.150A systematic reviewof nonsteroidal anti-inflammatory drugs used totreat pain in endodontic patients reported goodanalgesic responses in patients treated with either100 milligrams of flurbiprofen or the combinationof flurbiprofen with 100 mg of tramadol.151

In the classic case of the difficult-to-anesthetizemandibular molar, several studies have demon-


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Figure 4. Photomicrograph (original magnification 50,hemotoxylin and eosin stain) demonstrating a completecementum layer over a resected root end filled with min-eral trioxide aggregate.

Figure 3. Clinical photograph demonstrating an isthmusconnecting the two canals in the mesial root of amandibular first molar.


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strated that intraosseous anesthetics are effectivefor enhancing the incomplete anesthesia thatoccurs after inferior alveolar nerve blockinjection.152,153

Infection. Considerable progress has been made

with respect to the use of antibiotics in endo-dontic patients. Susceptibility testing studieshave indicated that 80 to 95 percent of cultivableendodontic microorganisms remain sensitive topenicillin, supporting the selection of penicillin asan antibiotic of first choice when indicated.154,155

Clindamycin is a good alternative for patientswho are unable to take penicillin, since approxi-mately 87 to 100 percent of cultivable endodonticmicroorganisms are sensitive to this antibi-otic.154,155Although antibiotics are effective fortreating endodontic infections, they appear to

have little effect on reducing pain.156 In addition,antibiotics have no effect when prescribed to treatpain due to irreversible pulpitis.157

Anxiety. Researchers have evaluated severalapproaches for treating anxiety associated withendodontic care. In general, both behavioral andpharmacological methods have proven to be effec-tive. Oral triazolam (0.25 mg) may be superior tooral diazepam (5 mg) for reducing anxiety asso-ciated with endodontic treatment.158

CONCLUSIONS AND FUTURE DIRECTIONS

The art and science of endodontics have under-gone significant advances in the past decade.These changes have resulted in improved treat-ment outcomes and an opportunity to preservethe natural dentition. These objectives can beachieved with less morbidity and more pre-dictability. The specialty of endodontics is dedi-cated to the preservation of healthy natural denti-tion. Compilation of more current clinical datathat are based on procedures performed withmore advanced techniques will provide a moreaccurate rate of healing after nonsurgical and

surgical endodontic therapy. The future holds thepromise of continued growth of the body ofresearch knowledge, and systematic reviews willprovide the most valuable thread of evidence con-necting the patient, the clinician, the educator,the researcher, the policy-maker, the editor, thebenefit purchaser and the benefit provider in thedecision-making process. s

Dr. Shabahang is the chair, Research and Scientific Affairs Com-mittee, Loma Linda University, Department of Endodontics, P.O. Box1057, Loma Linda, Calif. 92354-1057, e-mail [email protected]. Address reprint requests to Dr. Shabahang.

This work was made possible by the contributions of the members ofand consultants to the American Association of Endodontics Researchand Scientific Affairs Committee who contributed to this report: Drs.Leif K. Bakland, Mario DAddario, Mohamed F. Fayad, Ashraf Fouad,Charles J. Goodacre, Kenneth M. Hargreave, G.R. Holland, John I.Ingle, Bradford R. Johnson, Sergio Kuttler, Jeffrey Lilly, Robert J.Loushine, Andre Mickel, Carl W. Newton, Ilan Rotstein, Clifford J.

Ruddle, Charles L. Steffel and Mahmoud Torabinejad.

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