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update on •

An Evaluation of Cracked Teeth withReversible Pulpitis

• Endodontic Treatment of Teeth with Periapical Lesions

• Persistence of Bacte rial DNA After Cell Death

• Identifying Root-canal Systems with Cone-beamComputed Tomography

The pur pose of th is in vestigat ion by Krell from theUniversity of Iowa and Rivera from the University ofNorth Caro lina at Cha pel Hill was to report on the

clinical outcomes of cracked teeth diagnosed with reversiblepulpitis (RP). During a 6-year period, 8175 patients referredfor evaluation and treatment had medical and dental histo­ries, radiographs, pulpal and periapical diagnosis, periodon­tal probings, direct identification of crack(s) with transillu­m ination and bit ing responses on various cusps recorded.

Treatment was planned acco rding ro the pulpal and peri­apical diagnosis, excep r for cases of RP, wh ich were treat-

Inside this issue: Summer200B

merit -planned for crow ns on ly, regardless of periapicaldiagnosis. All pati ents were recalled at 1 year, unless root ­canal trea tment was needed before the anniversary.

Of the 8175 patients seen during the 6-year study period,796 were diagnosed with cracked teeth (9.7%) . The largestinc idence was with mandibular seco nd molars (30%) , fol­lowed by mandibular first molars (29 %) and maxillaryfirst molars (21%).

Among the cases of RP, 32 % were mandibular firstmolars, 25% were maxillary first molars and 23% weremandibular second molars. Of the 127 patients specificallydiagnosed with RP, 27 converted to irreversible pulpit is(n = 21) in 58 days or to necrotic pulp (n = 6) in 149 days.

A ll teeth had ini tial in terproximal probings <3 mm in thespace associated with the crack. Of the 27 teeth requiringroot-canal treatment, on ly 5 had increased interproximalprob ings associated with the fractured margina l ridge. Thegreat est increase in probing depth was 2 mm, for 2 of the5 teeth.

Table 1. Distribution of teeth according to outcome classificationin the experimental groups *

*Mantel-Haenszels x2 test was used to test trends in the contingency table.

Antibacterial dress ings such as ca l­cium hydroxide (CA[OH]z) arewidely used to combat microbiota,though inclusion of CA(OH) z in atreatment strategy has d isadvantages.It does not kill all of the intracanalbacteria, and it needs :<:2 v isits to beoptimally potent. Effectiveness of acl ini ca l strategy must take into ac­count other factors including totalcos ts, pat ient comfort and effort putinto the treatment.

It is beneficial to search for a I -visittreatment regi men as biologicallyeffect ive as a CA(OH) z-based 2-visitprocedure. The search for an effectiveI -v isit procedure h as used 2 ap­pro aches: the exclusion of an antibac­terial intracanal dressing and the in­clusion of a shor t- t ime dressing.

A fte r a review of the literature,Sarhorn et al (Int Endod J, 200 5)included 3 stud ies in their final meta­analysis. Each study used the first ap­proach for the I -visit treatment, andth e meta-an alysis could not show an ystatistically sign ificant difference inth e healing rate to the 2-visit alt erna­tive. However, conclusions must bemad e with ca re because the studiesare few, th e sample size is sma ll (on ly146 cases total) and the methods ofCA(OH)2 placement in 2 of thestudies have been questioned.

Kvist et al (J Endod, 2004 ) comparedthe microbiologic outcome of a l-visit

Total

62189

89

3055

40

2 visits

treatment regimen, incl ud ing a10-minute intra-appointment dressingwith 5% iodine-po tassium-iodide,with a standard CA(OH)2 2-v isitprocedure . In the postmedic ationmicrobial samp les, residual microor­ganisms were recovered from 29% ofthe l -visit treated tee th and in 36%of the 2-visit treated teeth. N o statis­t ically sign ifican t difference betweenthe groups was found .

The present invest igation byMolander et al from the Public DentalH ealth Serv ice , Sweden , aimed torecord the 2-year cli nical and radio­graphic outcome of the material fromKvist et al and to study the sign ifi­cance of the microbiologic samplingresu lts on the outc ome of treatment .A rando mization proced ure allocated53 teeth to I-vi sit treatment and48 teeth to 2-visit tre atment.

At the end of the study period,32 teeth (65 %) in the I -v isit treat­ment group and 30 teeth (75 %) inthe 2~visit treatment group were cla s­sified as hea led (Table I). A ltho ughthe 2-visit treatment group ha d a 10%high er success rate, stat ist ical ana ly­sis did not sho w any sign ifican t d if­ference between the groups (p = .75).However, 80% of teeth that wereob turated after a negative mi crobic­logic sample were classified as healed.Teeth obturated after posit ive sampleshealed in 44 %.

32134

49

1 visitOutcome

HealedUncertain healingNot healedTotal

Among the 27 cases requiring root­canal treatment,

EndodonticTreatment ofTeeth withPeriapical Lesions

• 15 had the crack on th e distal mar­ginal ridge;

• 4 had the crack on th e mesial mar­ginal ridge; and

. 8 had bot h marginal tidges involved.

None of the teeth h ad fractures ex­tending in to the floor of the chamberor rende ring the m nonrcstorablc . O fth e origina l remaining 100 cases of RP,none required root-canal treatment.

ConclusionThe authors found that if a crack isidentified ea rly eno ugh in patientswith RP and a crown is placed, roo t­canal treatment will be needed abo ut20% of the t ime with in a 6-monthperiod. In only a very small percent­age of cases will there be progressionof interpro xim al per iodo ntal defec tsassociated with the crack.

Krell KV, Rivera EM. A six )'ear evaluationof cracked teeth diagnosed with reversiblepulpitis: treatment and prognosis. JEndod2007;33:1405-1407.

Th e goal of endo dontic treat­ment of teeth with apical perio­don ti ti s is comp le te elim ina­

tion of bacte ria with in the root-canalsystem. Previous stud ies showed thatwhile instrumentation and irrigationof the root-canal system substa ntiallyreduce the number of microorgan isms,th ey rarely lead to total eradicatio n ofthe microorganisms.

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ConclusionThe authors showed that similarhealing results might be obtainedthrough 1- and 2-v isit antimicrobialtreatment. Their most sign ificantfind ing was the clear association ofperiapica l bone healing in tee ththat are root-filled after effective dis­infection (negative culture).

Molander A , Walj'tinge] , Rei' C , Ktis'T.Clinical and radiographic evaluation of one­and two-visit endodontic treatment of as)'171P­romcnc necrotic teeth with apical periodonti­' is: a randomized clinical trial. J Endod2007;33: 1145-1148.

Persistence ofBacterial DNAAfter Cell Death

Wh ile all bacteria l species inth e oral cavity can enterthe root cana l, on ly a re­

stricted group can esta blish a viableinfecti on . This is because th e root­ca na l system selec ts for on ly a lim­ited assortment of the ora l flora .

While the use of advanced anaerobicculturing methods has characte rizedth e polvrnicrobialnarure of tbein­fected root canal, more diverse endo­donti c microflora have been describedby soph isticated molecular methods.Thro ugh use of polymerase chain reac­tion (PCR) tech niques, several cul­tur e-difficult spec ies have been re­ported as more prevalent in root-cana lsamples th an previ ously thought.

However, because PCR-based tech­niques can no t distinguish betweenDNA from viab le and dead cells, it isuncl ear whether the det ected organ­isms represent the living endodonticflora or a record of organ isms that

have entered the root canal but notsurv ived. Nonsurviv ing species pre­sumably disint egrate, but DNA frag­ments migh t be detec ted and ampli­fied by PC R techniques. How longamp lifiable DNA might persist is ofconsiderable relevance for the valid­ity of PCR-based methods.

This l -vear experimental in vitrostudy by Young at al from the Uni­versity of Melbourne, Australia, testedthe hypothesis that PCR-detectableDNA from dead bacteria might per­sist after cell death and investigatedthe efficiency of sodium hypochlorite(NaOCI) as a decontamination agent.Using heat-killed Enterococcus faecalis,the persistence of DNA encoding th e16S rRNA gene was monitored byPCR. After 60-second incubat ion atroom tempe rature, NaOel was inac­t ivated by sodium th iosulfate. Onemicroliter of solution was the n usedas PCR template.

Experiments were repeated with DNAex t rac ted from he at -killed cellsI month after inactivation. An addi­tion al positive control was included inNaOCl experiments to exclude PCRinhibition by thiosulfate-inacti vatedNaOCI. In thi s group, NaOCI was in­act ivated by sodium th iosulfate beforebeing added to DNA suspensions.

Treatment with 1% NaOCI for 60 sec­onds destroyed amplifiable DN A .Dead-cell DNA was more suscept ibleto NaO C I degradation , presumably,as a result of its more advanced stateof decay.

Although this finding is consistentwith other reports, previous studies didnot cont rol for inhibition of PCR byth iosulfate-inactivated NaOC I or wereunable to distinguish NaOCI-basedDNA destruct ion from inhibition of

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PCR by thiosulfate-inactivatedNaOCI. Inactivation of NaOCI bysodium th iosulfate produ ces sodiumsalts such as sodium chloride, wh ichinhib it DNA polymerase at eleva tedconcentrations, and these results dem­onstrate concentrat ion-dependentsalt-induced inhibition of the PCRreacti on.

ConclusionThe autho rs found th at wh ile DN Aca n persist and be detected by PCRfor z l year after the death of a cell,NaOCI efficiently destroys DNA.They also highlighted an overlookedprob lem of inhibition of the PCRreaction by thiosulfate-inactivatedNaOCI. This establi shes the authen­t icity of PCR-based isolates as act ivepart icipants in the endodont ic flora.

YoungG , Turner S, Davies]K, et al. Bac­terial DNA persists for extended periodsaftercelldeath. J Endod 2007 ;33: 14 17-1420.

IdentifyingRoot-canal SystemsWith Cone-beamComputedTomography

Compared with conve nt ionalradiograph y, digita l radiogra­phy offers the benefits of less

radiation exposure, faster imageacquisition , no requ irement fo rche micals and a number of imageprocessing tools such as magnifica­tion. Two types of currently availabledigital radiography systems are solid­state sensors with e ither a charge­coupled device (CCD) or comple­mentary metal oxide semiconductor(CMOS) chi p and photost imulable

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Table 2. Average number of root-canal systems (ReSs) identified with the 3 radiographic methods

Tooth type

Mandibular inci sorMandi bular first premolarMaxillary first molar

Average no. of RCSsidentified with CCO

1.01.03.1

Average no. of RCSsidentified with PSP

1.3l.l3.0

Average no. of RCSsidentified with CBCT

1.5J.23.6

phosphor plate (PSP) technology.CCD-based digital detectors includex- rav or [igh t-sen sit ive elements that,when stimulated by x-rays, generatean electrical charge proportiona l rothe intensity of the x-ray beam th atreached them.

Advantages incl ude faster image ac­quisition, digital image processing,lower radiatio n expos ure and moreeffect ive image arch iving. Disadvan­tages incl ude cost, bulkiness and a rel­atively small active area.

CMOS-based digital detectors acquirethe rad iographic image in a similarfash ion . A disadva ntage of CMOS­based digital detectors is a smalleract ive area. No differences ha ve beenfound between CMOS and CCDtechnology in diagnostic efficacy.

PSP technology uses a reusable detec­tor that captures the radiographicimage on an em ulsion (storage phos­phor) as a latent image ini t ially. Withproper stimulation, the energy storedon the emulsion is emitted and cap­tured as a charge.

Adva ntages of this system include ath inner de tector for better patientcomfort, lower cost and the ability tobe reused by simply expos ing to wh iteligh t, wh ich erases a prev ious image.Durability stands as the main disad­vantage of PSP detectors. However,Ang e t al (Oral Surg Oral Med OralPathal Oral Radiol Endod, 2006) re­por ted that PSP detectors demon-

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st rate similar diagnost ic qual ity toCCD/CMOS detectors.

Still anothe r tec hn ique is cone-beamcomputed tomography (CBCT). Thisuses a cone-shaped beam and multipleexpos ures around an object to revealthe object 's internal arch itec ture.T hus, the cl in ic ian can view morpho,logic features, as well as pathology,from different 3-dimens ional (3-D)perspectives.

A distinct advan tage of CBCT is thatit allows for 3-D reco nstr uction ofroot-canal systems. Three-D inform a­tion , along with tacti le feedback dur­ing instrumentation , gives th e clini­c ian a more thorough understandingof the true morphology of root-can alsystems.

Th is investigation by Matherne et alfrom the Univers ity of Missou ri­Kansas C ity compared the diagnosticefficacy of contemporary d igital imag­ing modali ties (CC D, PSP ) with thatof CBCT. Seventy-two extracted teethwere exposed to CCD (Gendex, DesPlai ne s, Il l. ), PSP (Gend ex) andCBCT(1S I-CAT Imaging SciencesIn tern at ional, Inc., Hatfield, Pa.)radiograph y. Specimens incl uded24 maxillary molars, 24 mandibularpremolars and 24 mandibular incisors.Tooth -type select ions were based onthe grea ter possibility of multipleroot-cana l systems .

T hree board-cert ified endo dont istseva luated CCD and PSP images to

determine th e numher of root-canalsystems . C BCT images esta blished"ground truth" for th e comparisonsand were ~valuated by a bo ard-ccrt i­fied oral and maxillofacial radiologistwho also determined the number ofroot-can al systems. The ave rage n um­ber of root-cana l systems iden tifiedwith CCD and PSP images comparedwith C BCT are listed in Table 2.

ConclusionT he authors of this study found thatevaluators of eithe r C CD or PSPmethods faile d to identify :0: 1 roo t­canal system in approximately 4 of10 teeth. T hey also found that evalu­ation of C BCT images always resultedin a greate r n umber of root-canal sys­tems identified than evaluat ions ofPSP or CCD images.

Matherne RI', Angelopoulos C, Kulild jC,Tim D. Use of cone-beam computed tomog,mph)' to identify root canal sysrerns in vitro.J Endod 2008;34:87-89 .

In the next issue:• Retreatment outcomes in

endodontics

• Anesthetic efficacy of a repeatedintraosseous injection

• Interaction between sodiumhypochlorite and chlorhexidine

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