Pulpotomy reconsidered: Application of anadhesive system to pulpotomized permanentprimate pulps

Abeer A. Hafez, DDS, MSVHugh M, Kopel, DDS, MSVCharles F, Cox, DMD, FADI=

Objective; This sfudy was underfaken to compare thG healing response of permanent primate puips topulpofomy procedures following hemorrhage control and adhesive hybridization to their response afterconvenfional treafments. Method and materials; Forty-two cavities were placed throughout the denfitionsof 4 adult monkeys. In 24 feefh, following mechanical bur exposure and pulpotomy, hemorrhage wasconfrolled wifh application of 3% sodium hypochlorife. The cavity was rinsed and tfie enamel-denlin-pulpsurface was restored with an adhesive system for 6 and 7 months, Caicium hydroxide, lormocresol, andresin-modified glass-ionomer cement were placed as convenfional Ireatmenfs in 18 feeth lor 70 days andcavities were sealed wifh resin-modified glass-ionomer cement. Following perfusion fixation, tissues weredemineraiized, sectioned, stained, and hisfologically graded using detined criteria. Results: Of 24adhesive system pulps, 10 showed no or minimal pulpal response, 1 showed an acute response, 6showed a chronic response, 2 showed a severe response, and 5 showed comparfmentalized 2ones oflocalized necrosis. Only 8 adhesive system pulps showed stained bacteria associafed wifh inflamedfissues. Thirteen adhesive system pulps showed dentin bridging directly at the adhesive sysfem inlerface,Oalcium hydroxide-freafed specimens showed healing and dentin formation, while resin-modified glass-ionomer cement and formocresoi treatments failed to result in any bridging. Apical tissues in all adhesive-treated specimens showed normal pulps and primary odontoblasts along their entire wails. Conclusion:Permanent pulps withouf periapical radiolucenoies may survive pulpotomy, provided that hemorrhage isproperly controlled and fhe pulp-restorafion interface is hybridized to exclude all microieakage,(Quintessence int 2000:31:579-589)

Key words: adhesive sysfem, compartmentalizafion, hemorrhage control, hybridizafion, pulpofomy,strangulation

CLINICAL RELEVANCE: Hemorrhage oonfrol is criticalfo developing an infegrai hybridized seal fo eliminatebacterial microleakage. The fested sodium hypochloriteand adhesive system is nonirrifating to pulpotomized tis-sues for extended time periods, producing new denfinbridges.

'Research Associafe, Department of Resforative Dentistry, University olAlabarra, School of Dentisfry, Birmingham, Alabama,

^Lecturer, Pédiatrie Denlistry Section, Universify ct Calilornia, Los Angeles,Scliocl cl Dentistry, Centei lor Heaifh Science, Los Angeles, Calilornia

^Prnfessor oi Denfistry, Departmenfs ot Restorative Denfistry, Biomateriais,and Endodcntics, universily cf Alabama, School cf Denfistry, Birmingham.Alaba rna.

Reprinl requesfs: Dr Abeer A, Hafez, Department of Resforative Denfisfry,Universify of Alabama, Schcol oi Denfistry. 609-A, 1530 3rd Avenue South,Birmingham, Alabama 35294. E-mail' ahafez® uab.edu

In clinical practice, a tn echan i call y exposed sympto-matic pulp with possible irreversible pulpitis may be

treated successfully if the infected tissue is removed tovisibly healthy underlying pulp and the hemorrhage iscontrolled effectively,' Since the early 1980s, the use ofadhesive systems (AS) for direct pulp capping hasgained much attention among dentists and has stimu-lated a number of histologie and clinical investiga-tions,^-" In vivo usage studies show that exposed pulpsare capable of healing and dentin bridge formation,regardless of the capping fiiaterial used, provided thatbacterial microleakage is prevented from causing recur-ring inflammation and necrosis,-"' "-'

Prior to the use of dentin bonding systems for pul-pal therapy, the practitioner would treat exposed pulpsby placement of certain agents to promote healing anddentin bridge formation. The most frequently usedmaterial was some formulation of calcium hydroxide[Ca(0H)2], placed over the exposure site. This wasusually done only when clinical and radiographie eval-uation suggested the possibility of healing,'^

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Depending on the patient's clinical history, cariousteeth presenting with symptomatic pulpitis may betreated by pulpotomy with medication and provision-alization for relief of pain, or else by complete removalof the pulp and subsequent obturation.'^

Pulpotomy has been practiced since the early 1900sbut is generally contraindicated in teeth beyond thestage of active hyperemia, or in teeth with radio-graphic evidence of periapicai infection." Sommer etaP^ advocated coronal pulpotomy fo preserve the vital-ity of the remaining tissue. "Therapeutic pulpotomy"was described by McGehee et aP'' as an intentionalclinical procedure in permanent teeth to remove theinfected coronal pulpal tissue, to preserve the vitalityof the radicular pulp.

In the presence of infecfion and inflammation, coro-nal pulpotomy is an accepted endoduntic procedure forchildren and young adults, in teeth with deep lesions orcarious exposures as weU as in fractured permanentteeth whose root apices have not yet closed.' Generally,the añecfed coronal pulp is removed to the level of theradicular canals, leaving the root tissue intact

In primary teeth, pulpotomy is completed to main-tain the tooth in a physiologically healthy restorablestate, until natural exfoliation occurs. The top of theresidual pulp surface is sealed with one of severalmedicaments, Ca(OH); being the most common; if theapex is already closed, conventional endodontic pro-cedures are indicated.'*

In the permanent dentition, pulpotomy is generallyused in teeth following carious exposure, trauma, orabscess formation and is intended to permit apcxiflca-tion or apexogenesis, and eventual root canal treat-ment, if needed. Other clinical studies have encouragedthe use of pulpotomy ¡n permanent teeth presentingwith carious exposures, hyperplastic pulpitis, ornecrotic inflammation.' --' Many reports on the use ofpulpotomy suggest that formation of a dentin bridgeover the amputated pulp is regarded as a desirable cri-terion of suecess. -" '* However, bridging is regarded ascontroversial and not necessarily an indicator of suc-cess by some researchers.^''^ Several reports haveshown multiple tunnel defects in most dentin bridges;these tunnels permit bacterial microleakage, recurringinfection, and eventual necrosis.''"^'

PULP COMPARTMENTALIZATIONVERSUS STRANGULATION

Localized pressure as a result of inflammatory reac-tions within an affected pulp has been described ascausing compartmentalization, In which the pulpresponds with regional zones of inflammation andnecrosis.'"- ' Data support abandonment of the stran-

gulation theory, which suggests that the entire pulpsimply dies en masse.'"''' Eidelman and Ulmansky"and Reeves and Stanley '' reported localized inflamma-tion, dilation of blood vessels, edema, and the pres-ence of polymorphonuclear leukocytes in pulps withiess than 0.5 mm of overlying remaining dentin. Whenthe remaining pulpal elements are intact, it is atiexample of compartmentalization.

Current endodontic literature tends not to supportthe use of pulpotomy procedures in permanent teetbwith deep caries or a mechanical exposure; researchgenerally favors standard endodontic treatment withprecision instrumentation and canal obturation. Onlyin the treatment of fractured anterior teeth with pulpalexposures, does the literature discuss puipotomy ordirect pulp capping (Cvek technique) with CaiOH) ''' 'or certain adhesive systems."'•- Regardless of the ma-terial used for direct pulp capping, successful pulpo-tomy requires absolute control of hemorrhage. Thismay be achieved with mechanical pressure (eg, cottonpellet), with hemostafic agents (eg, hydrogen peroxide,calcium hydroxide, sodium hypochiorite (NaOCl), fer-ric sulfate, or epinephrine), or with devices such aselectrocautery and laser energy.

In the classic pulpotomy technique, once hemor-rhage is controlled, a medicament such as Ca(0H)2 orformocresol (FC) is applied for a limited time, followedby a base material. The tooth may then be restored witiia core material such as resin composite and a crown foprovide long-term control of bacteriai microleakage atall margins. Although tissues in the canals under these 2agents show fairiy predictable clinical results, the histo-logie data are nol always favo rabie.='•2-'

Although it has been recognized for many yearsthat various formulations of Ca(OH)T may promotedenfin bridging, their use has also been associatedwitb both internal and external résorption.'''" This isgenerally not a severe probiem in primary teeth,because they eventually exfoliate. For young perma-nent teeth with open apices, Ca(0H)2 seems to pro-vide an environment that promotes root development.

Formocresol has been used in primary teeth since1918 and currently is the most commonly used agentin primary teeth with significant levels of clinical suc-cess.''^ However, because of its in vitro mutageniceffect, the use of FC remains controversial.'^ In addi-tion, some in vivo studies report systemic absorptionof FC, causing concern within the guidelines of theAmerican Academy of Pédiatrie Dentistry"-^s

Wong "* studied the effect of a paraformaldehydepaste on amputated pulpal and periapicai tissues of pri-mary and permanent rhesus monkey teeth. Treatmenttime was from 9 fo 84 days in primary teeth and 37 fo48 days in permanent teeth. Wong'^ found similarinflammatory and degenerative changes in subjacent

580 Voiume 31, Numbers, 2000

iHafez et al

periapicai tissues in both dentitions. There was also evi-dence of cbronic lymphocyte infiltration in the underly-ing dental sac of the permanent teeth.

Some histoiogic studies have reported an adversepulpal reaction to hotb FC and Ca(0H)2, ranging fromslight fibrosis, intracanal calcification, and internalrésorption to complete mummification and even cal-cific ohturation.-"* To eliminate these sequelae, investi-gators have studied agents such as glutaraldehyde,'"-'^iodoform," ferric sulfate,-'-' freeze-dried bone,-'= honemorphogenetic protein^* osteogenic protein-1," theanti-inflammatory agent Tetrandrine,''" and collagen,-"as well as devices such as electrosurgery,^" electroful-guration,'' and laser technologies, -- ^ to promote bio-logic pulpal healing and to obtain predictable clinicalsuccess rates with minima! insuit to tbe tissues.

Acceptable pulpal responses have been reported fordirect pulp capping with photocured glass-ionomercements.'•'•' Otbers^ '*' have reported less favorablepulpal responses in gnotobiotic rat pulps directcapped with a traditional acid-base glass-ionomercement such as ASPA {DeTrey). A recent histologiestudy^* reported tbat resin-modified glass-ionomercement (RMGIC) presents an acceptable biologicresponse wben placed on exposed pulps. However, todate, no bistologic study bas reported on the use ofRMGIC systems for pulpotomies.

With all of the untoward sequelae in pulpal tberapytbat are associated witb deep carious lesions ortrauma, the clinician may now iook fonvard to morebioiogic heaiing with dentin adhesive systems.Studies^-''-"-"'^-""" have reported successful histoiogicand clinical results following placement of dentinadbesive systems directly on vital pulpal tissues. Theprime tenet of this tecbnique recognizes the "inherentcapacity" of tbe puip to heal in tbe absence of bacterialinfection through prevention of microleakage.''''''""These investigations have sbown that exposed puipsare capable of healing and dentin bridge formation,regardless of the applications of any specific material,as long as hemorrhage is controlled, clot formation isprevented, and a cavity seal is obtained to prevent fur-ther microleakage that promotes pulp inflammation.

The purpose of this investigation was to histologi-cally investigate pulpal soft and hard tissue responsein fhe permanent dentitions of primates at extendedtitne periods following pulpotomy and adhesive seal-ing with resin systems. The response was compared tothe responses to conventional treatment materiais.

METHOD AND MATERIALS

Four adult Rhesus macaque monkeys, approximately4 to 5 years old, provided 42 vital teeth to evaluate

pulpotomy procedures. The monkeys were housed inthe University of Alabama at Birmingham Anima!Resource facility for a 90-day quarantine period. Eachmonkey was initially sedated with intramuscular injec-tions of fO mg/kg of iictamine bydrochloride, fOOmg/mL, (Fort Dodge, Iowa] and Ace Promazine(Vedco). Isoflurane {Halo Carbon Laboratories) wasused for general inbalation sedation. No local dentalanestbesia was used, so as to reduce the potentialeffect of ischemia on local periodontal and puipai vas-culature. Ali teeth were scaled and polished with arubber cup and prophylaxis paste prior to the place-ment of the various restorative materiais.

Quadrants of teeth were isolated witb steriie cottonrolls, and tbe saliva was controlied with bigb-speedevacuation. Occlusal access was made on premolarsand molar teeth, and facial access was made on canineand incisor teeth, with a No. 330 carhide bur used atultrabigh speed with water spray. A new bur wasemployed on every fourth cavity. Pulpal access wasenlarged, and pulpotomy was performed with the samebur until several millimeters of the underiying puipwere reinoved. For tbe AS-sea!ed puip group, a cottonpeilet was dampened with 3 /0 NaOCl and placed onthe tissues for approximately 80 seconds to providehemorrhage control, to provide cbemical amputationof the subjacent tissue, and to promote elimination oftbe subjacent dentin chips. Tbe area was gently rinsedand hemorrbage was treated again, if necessary. Forthe conventional treatment groups, hemorrhage wascontroiled by placement of a steriie cotton pellet on tbepulpotomized site to provide mechanical bemostasis.

For the experimental AS group, Ciearfii Liner Bondtl [Kuraray) was used on 24 pulps, Following hemor-rhage control, tbe cavity and exposure were gently airdispei*sed, and LB primer was piaced onto fhe dentinwith a brusb just peripheral to the dentin-puip interfaceand allowed to flow over the exposed puipal tissues.The AS resin was then placed and photocured with anOptilux 400 light-curing unit {Demetron Research).The remainder of the cavity was restored to the cavo-surface margin with AP-X (Kuraray) resin composite.

In the conventional treatment groups, pulpalresponses were evaluated after 70 days. In 6 teetb, aCa{0H)2 agent {Life, Kerr) was placed directly on tbepulp, and tbe cavity was restored to the cavosurfacemargin with a RMGIC (Vitremer, 3M Dental). Inanother 6 teeth, a cotton pellet was moistened with a1:5 dilution of FC (1 part Buckiey's formocresol[Sultan Chemists], 3 parts glycerin, and 1 part distilledwater) and placed into direct contact with the pulpfor 5 minutes. The cavity was then restored to thecavosurface margin with a RMGIC, For the remaining6 teeth, RMGIC was placed directly over the ampu-tated pulp and to the cavosurface margin. All materials

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TABLE 1 Evaluation criteria

Seore Description

infiammatory celi response1 No, or a few, scattered inflammatory cells are present in the

tissue beneath ttie pulpotomized area.3a Aoute intlammatory eell lesion is predominated by poly-

morphonuciear leukooytes.2c Chronic inflammatory cell lesion is predominated by

mononuelear lymphocytes.3 Severe inflammatory cell lesion appears as an abscess or

dense infiltrate ot polymorphonuciear leukocytes involvingone third or more ot the pulp system.

4 A compartmentalized zone of necrotic pulp is present.

Soft tissue organization1 Tissue morphology is normal or almost normal beiow the

pulpotomized area or throughout the pulp2 There is a iack ot complete tissue morphology below the

pulpotomized area: the deeper pulpal tissue is normal.3 Tbere is iess ot general puip morphology and cellular orga-

nization below the pulpotomized area.4 Necrosis is present in the coronal third or more ol tbe puip-

otomized area.

Reparative dentin deposition1 Mo reparative dentin is present below the cut tubules of the

cavity preparation.2 A small thin rim of reparative dentin is present beiow the cut

tubules ol tbe cavity preparation.3 A laige buik of new reparative dentin is present below Ihe

cut tubuies of the cavity preparation.

Denffn bridge formation1 New bridge tissue is present directiy adjacent to some por-

tion of the restorative materiai.2 New dentin bridge is present at some distance from tlie

material intertace.3 There is no evidence of any dentin bndge tissue in any

section.

Bacteriai staining1 There is no bacterial staining in any section,2 A positive bacterial staining reaction is present along the

dentin-pjip-material interface.3 A positive bacterial staining reaction is present within the

cut dentinal tubuies of the cavity preparation,4 A positive bacterial staining reaction is present within the

dental puip.

were applied in accordance with the manufacturers'instructions.

The animals were killed at 70 days or 6 or 7 monthspostrestoration, hy ieft ventricular flushing with 0,9%sodium chloride followed hy perfusion with a fast-penetrating glutaraldehyde-phosphate-buffered para-formaldehyde (GTA-PBF) fixative. Teeth were cutfrom the alveolus, the root tip was removed with a No.

557 carhide bur, and each teoth immediately postfixedin GTA-PBF for 24 hours at 4°C, Following postfixa-tion, teeth were demineralized through multiplechanges of 0,5 M of ethylenediaminetetraacetic acid[pH 7,2) over 4 months. After radiographie confirma-tion of end-point demineralization, each tooth wasrinsed through distilled water for 2 hours, dehydratedin ascending grades of ethyl alcohol to N-butyl alco-hol, and etirbedded in Paraplast-Plus (Oxford Lab},

Uninterrupted 7-|jm serial sections were cut ort arotary microtome and placed on gelatin-coated slides.Glass microslides were stained with hemotoxylin-eosin, Masson's trichrome or McKay's stain for identi-fication of bacteria. Inflammatory pulpal responsesand the presence or absence of bacteria were gradedby light microscopy according to modified criteriadescribed by Cox et al (Tahle l),^

RESULTS

All 42 teeth remained symptomless for the duratioti ofthe experiment, as judged by observations of the atii-mal's behavior, mohility tests, and visual evidence ofpossible son tissue changes. The pulpal responses andgraded histopathologic results of the material systemsare sumtitarized in Table 2,

Conventional treatments

Calcium hydroxide group. Two of 6 pulps showedno evidence of pulpal inflamrnation (Fig 1), 2 pulpsshowed severe inflammation, and 2 showed compart-mentalized necrosis associated with stained bacteria(Fig 2), Two pulps showed normal unaffected primaryodontohlasts, while the other 4 pulps showed defini-tive degeneration. Teeth in this group showed a thickrim of reparative dentin below the tubules of the cav-ity floor,

Formocresol group. Two of 6 pulps showed severeinflamrnation (grade 3) associated with stained hacte-ria in their pulp spaces. The remaining 4 pulps showedcomplete necrosis (Fig 3). In all pulps of this group,the soft tissue showed definitive degeneration. Nopulps showed any dentin bridging or evidence ofreparative dentin deposition below the cut tuhulesalong the canal wall.

Resin-modified giass-ionomer cement group.Three of 6 pulps showed complete necrosis associatedwith stained bacterial profiles along the dentin-pulp-material interface, while 3 showed no puipal inflam-mation (grade 1), No dentin bridge formation wasseen adjacent to the RMGIC interface (Fig 4), All 6pulps showed a thick rim of reparative dentin belowthe eut tubules along the canal wall.

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i-ialez et ai

TABLE 2

Material

AdhesivesystemCa(OH);RMG1CFC

Histologie findings and bacterial presence in pulpotomized pulps

teeth

24

6

6

6

1

10

2

3

0

"eliuiarinflammation'

2a

1

0

0

0

"See Table 1 loran expianatioCa(OH), . alcium liydroxide;

2c

6

0

0

0

of the e^MGlC -

3

22

0

2

4

5

23

4

valuationres

0

1

12

2

3

0

cnleria.

soft tissueganization'

2

2

0

0

0

3

5

4

0

0

n-modified glass-ionomer ce

4

5

0

3

6

m

Reparativedentin formation'

1

3

0

0

6

ent; FC = fo

2 3

7 140 60 60 0

mocresol

Dentintiridginç

1

13

6

0

0

2

0

0

0

0

3

I t

0

6

6

1

16

434

Stainedbacleria'

2 3

1 00 03 00 0

4

7

2

0

2

Fig 1 Histologie puipai response ot a 70-day puipotomy witii cai-cium hydroxide, which is visible as a biack-stained material (arrow-heads) adjacent to the dentin bridge (DB). Tiie subjacent odonto-blastjc layer is disorganized as attitact. Some caloium hydroxidemateriai (arrow) is visible in the subjacent puip tissue below theDB. (Hematoxyiin-eosin stain, original magnification x46 )

Fig 2 Section from a 70-day caicium hydroxide-pulpctomizedpuip that presented with compiele necrcsis. Ye i low-stained pulpaldebris is visibie adjacent tc ttie caicium hydroxide materiai(arrowheads). Blue-stained bacteria (arrows) lie adjacent to thecalcium iiydroxide and in the underiying space. (McKay's bacter-iai stain; original magnification x160.]

Fig 3 Hiatoiogic section of a 70-day formocresoi puipotomy,which stiows severe infiammation [grade 3] tfircughout the entirepuip canal system. Tiiere is no dentin bridge or reparative dentindeposition along ttie canal waiis, because tixation of ttie entirepuip resuited frcm application ot formocresoi. (Masson's trichromeStain; originai magnilication x15.)

Fig 4 Histologie pulpal response to a 70-day puipotomy withresin-moditied giass-ionomer cement. The clear space in theupper right was previously occupied by resin-mcdified glass-ionomer cement. Below the pur pie-stained caiciotraumatic line isa zone ci reparative dentin (RD) resulting from the preparationtrauma Nc bridge is seen along the resin-modified giass-ionomercement-pulp interface. The pulp below the interface is denselyfiiled with infiammatory ceils (arrows). (Masscn's tnohrcme stain;criginal magnitication x20 )

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Hafez et al

Fig 5 Section írom an adhesive sysLem-puipolomized lootii, 7months posttreatmenf. A new denlin bridge (DB) is visibie direcfiyadjacenf to the ciear interface of the adhesive system in theabsence of caicium iiydroKide. A continuous iayer of new odonto-blastoid cells is present aicng fhe DB wifhouf any infiammation inIhe deeper pulp. Note the thin zone of reparative dentin (asterisk)on ttie bifurcation dentin area. (iHematoxyiin-eosin stain, originalmagnification xS4 ]

Fig 6 Section fhrough an adhesive sysfem-pulpotomized puio, 6monihs posftrealment. Some portions of a new dentin bndge (DB)are seen fo ftie righf ol ttie tieid, direcfly adjaoent fo the cleai areapreviousiy containing the resin composite. Note the thici* areas olreparative dentin (RD) beiow the cut tubules. Several areas olchronic intiammatory ceils (arrows) are presenf. (Hematoxylin-eosin stain; originai magnitication x64.)

Fig 7 Section Ihrough a 6-month posttreatment pulp of the adhe-sive system-pulpoiomized group Reparative denfin (RD) is pre-senf below the cut tubules of the exposure site, demonstratinghealing. No dentin bridge is present below the adhesivesysfem-pulp interface. Pulp subjacent lo the adhesivesystem-pulp interlace is lilled wilh chronic infiammatory cells(arrows). The deeper pulp is normal, wifh some areas of smaliempty vessels below the primary and new odonfoblasfoid cells.(Hemafoxylin-eosin stain; original magnitication x80,)

Fig B Section through a chronically inflamed, adtiesivesystem-pulpotomized toolh at 6 months. Dari( blue-slained bacfe-ria are present on the cavity wall, ad|aoent fo the ciear space,which was previously resfored wilh a resin composite reslorafion.(McKay's bacterial slain, original magnification x200.)

Adhesive system treatment

At 6 and 7 months, 10 of the 24 pulps showed normal,vital, noninflamed tissues. In the coronal regions of 12pulps, there was loss of primary odontoblasts belowthe cut tubules. However, in the deeper portions ofthese same pulps, normal unaffected primary odonto-biasts were present along the apical canal walls (Fig5). Neither fibrosis nor résorption was observed inthese teeth. One pulp showed localized {grade 2a)acute inflammation, 6 pulps showed localized (grade2c) areas with chronic inflammatory cells (Fig 6), 2

showed severe inflammation (Fig 7), and 5 showedcompartmentalized zones of necrosis. Chronic inflam-fnation was localized, and necrosis hmited to the coro-nal pulpal tissue compartment. Thirteen of 24 pulpsshowed new dentin bridge formation directly adjacentto the adhesive resin-pulp interface. Of 24 pulps, 16showed no stained bacteria, 7 sbowed stained bacteriawithin the dental pulp, and 1 showed stained bacteriaalong the dentin-material interface (Fig 8), All 8 pulpsthat stained positive for bacteria showed varyingdegrees of inflammation. As an indicator of pulpalhealing and new odoritoblastoid cell differentiation 14

584 Voiume 31, Number 8, 2000

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Fig 9 Section through an adhesive system-puipoton-i^oci too'.liafter 7 montiis. A new dentin bridge (DB) has formed adjacent iothe adhesive system—merging along witn the reparalive dentin[RD¡ below the cut tubuies. A oontinugus zone of new odontobias-toiü cells is present aiong the puipai surface of the DB and RD.[iHematoxyiin-eosin stain, originai magnitication x50.)

Fig 10 Section tinrough a tûotn direct capped with an adiiesivesystem for 21 days foilowing hemorrhage controi with sodiumhypochiorite Note the protrusion of pulpal (issue (arrows), whichhas proiiterated inio Ihe space between the cavity wali and theadhesive system interface. This is a function oí a rernaining biotiimthai prevented infiltration of primer and bonding systems, inhibit-ing hybrid layer formation (Hematoxylin-eosin stain; originai mag-nification x50.)

pulps showed new reparative dentin formation athe pulp wall below the exposure interface (Fig 9).

DISCUSSION

Perhaps the topic of pulpal biocompatibility has toolong focused only on such issues as acid etching ofvital dentin and material toxicity. Considering thispoint, how can the important issue of hemorrhagecontrol in International Standardization Organization(ISO) pulp usage studies be reconciled to daily clinicalpractice? For ISO usage studies, most regulatoryagencies (eg, US Department of Agriculture) requirethat material placement be cotnpleted under generalanesthesia with assistance of a certified anesthesia lab-oratory technician. A study by Heyeraas" reportedthat general anesthesia has little effect on controllingpulpal blood flow. Consequently, previous ISO usagestudies "-' • - "-™ that employed pulpal exposures orpulpotomies presented excessive hemorrhaging com-pared to that experienced during routine human clini-cal dental practice. Traditional anesthesia in humansroutinely involves the use of local anesthetics, whichgeneraiiy contain vasoconstrictors.

To date, no commercial agents have shown properhemorrhage control when placed on the vital pulp inISO usage studies when the nonhuman primate issedated by general anesthesia. A recent usage studywith incomplete hemorrhage control revealed rem-nants of debris on the cavity walls and floor.^^ Thisdebris leaves an organic biofilm, made up of pulpal

blood constituents as well as smear layer debris, onfhe cavity walls (Fig 10). These factors may compro-mise the interdiffusion of primer into the underlyingdenfin, thereby interfering with the formation of a uni-form hybrid laycr." *-* However, agents with high pH,such as NaOCl and Ca(OH),, tend to provide betterhistologie results than do low-pH agents, probably dueto their capacity to reduce and stop normal bloodflow. Additional beneflts of NaOC! are disinfection,removai of dentin chips from the subjacent pulpal tis-sues, and fibrin and clot removal (chemical amputa-tion), all of which combine to promote healing.'^*""-"

The issue of excessive dentin chips left after mechan-ical bur exposure (ie, "chipitis") has been diseussed byStanley, * who suggested that the presence of dentinchips below the exposure site will complicate healingand bridging. Consequently, proper removal of subja-cent clot and all denfin cbips promotes pulpal healing.Katoh et aF^ reported that the primary cause of pulpalinflammation is incomplete control of homeostasis atthe exposed pulp-detitin interface, leading to an imme-diate poor biologic dentin-pulp seal along the restora-tion-tooth interface and resulting in failure of a long-term clinical seal and eventual bacterial microleakage.Organic debris remaining on the cavity floor peripheralto the pulpal exposure or pulpotomy interface causes anonseal and provides an avenue for eventual micro-leakage." ' In the absence of a complete seal, resultingmicroleakage allows recurrent formation of a biofilmthat contains bacteria and other debris, pertnitting con-tamination of the cavity walls, tubule complex, and pul-pal tissue.

Ouintessence internationai 585

• Hafez et al

This scenario of technique sensitivity is perhaps themost likely explanation for the hacterial stainingfound in 8 pulps. Of tbe 24 AS-capped pulpotomizedpulps, 5 sbowed compartmentalized zones of localisednecrosis (grade 4) in fhe subjacent tissues. The corre-lation of hacterial microleakage and regional inflam-mation is supported by tbe presence of stained bacter-ial profiles in 8 of 14 inflamed pulps.

To achieve a permanent, long lasting seal at thetooth-AS restoration interface, the abiiity to controlhemorrbage controi and the piacement of hydrophilicprimers on clean dentin are probably the most impor-tant aspects of the entire ciinical procedure. High-pHagents, such as NaOCl, solubilize hiofilms more selec-tively than do acidic agents, wbich tend to precipitateproteins rather tban to dissolve them. In nonexposedcavities, wbere the volume of pulpal serum leakageand gingivai fluid contamination is minimal, tbe cre-ation of" a proper hybridized layer is more easilyachieved. However, in exposed puips, where hemor-rhage is difflcult to control, the proper placement ofhydrophiiic primers on a clean dentin surface followedby the placement of hydrophobic systems is extremeiytechnique sensitive.

When a complete hybridized seai is present aroundthe periphery of a pulpa! exposure site, the ASappears to prevent bacterial infiltration through tbetooth-restoration interface. This impiies that the ASsimply provides a true hermetic seal to prevent hacter-ial penetration and to promote heaiing and dentinbridge formation.

Data from this study reaffirms previous stud-¡gs9.iLiî.5y.f.o (¡.,31 ti g yH^j primate pulp has an inherentcapacity for soft tissue bealing and bridge formationdirectly adjacent to an AS interface in tbe absence ofany Ca{OH)2 agent.

Before a dentin bridge forms at tbe AS-pulp inter-face, several bioiogic events must occur. Fibrobiastsfrom tbe deeper puip first migrate to the wound sitealong with macrophages and blood vessels. "-' Oncealigned to fhe AS-pulp interface, certain cells, throughmechanical or biologic contact guidance mechanisms,reorient themseives to become differentiated odonto-blastoid celis. At tbe same time, certain of tbese differ-entiating ceils align fbemselves along the predentininterface below the cut dentinal tuhules of the prepa-ration to take part in reparative dentin deposition. Itshouid be remembered that reparative dentin isdeposited before dentin bridge formation occurs at theAS-pulp interface.^"" Both Hess''' and Zander'^ sug-gested that dentin bridge formation is a primary indi-cator for success. Their various data complementsthese data, in which all but 3 AS-capped pulps showedreparative dentin along the predentin interface, in tbeabsence of any stained hacteria (see Tabie 2).

Cvek et aP^ treated pulpotomized monkey incisorswith either isobutyl cyanoacryiate or Ca(0H)2 for 10and 60 minutes. Both treatments resulted in hard tis-sue formation at the pulp-material interface, suggest-ing tbat some degree of low-grade irritation is neces-sary for hard tissue formation in exposed pulps andthat the pulp possesses an inherent capacity to bealagainst severai materials.'^

It is noteworthy that none of the 24 adbesive-capped teeth presented complete pulpal necrosis orstrangulation of the entire chamber. These observa-tions of regional celi alteration are in complete accor-dance with those of Van Hassel,'" wbo suggested thatthe strangulation theory is not scientiflcally supportedand that puipai inflammation tends to occur via "com-partmentalization" of the inflammatory process.

Tarim et aP« reported that 8 of 36 RMGIC direct-capped monkey pulps sbowed various grades ofinflammatory responses, aii associated witb stainedhacteria. In tbe RMGIC group of tbe present study, 3necrotic pulps were associated with stained bacteria,indicating the direct relationship of inflammation tobacterial microleakage.

Tbe 70-day data suggests that Ca(OH); dissolvesover some time, permitting bacteriai invasion. In addi-tion, because hemorrbage was controlled by applica-tion of a dry cotton pelict to the exposure site in fheconventionai treatment groups, it is probable there waspoor adherence of tbe RMGIC deflnitive restoration fothe dentin. This creates an avenue for bacteria to entervia microleakage, justifying the use of NaOCl to con-trol hemorrhage to provide a proper seal. In spite ofthe occurrence of dentin bridges in the Ca{0H)2group, tunnel defects were observed. It bas been specu-lated that the migration of dissolved Ca(0H)2 particlesinto the underiying pulp causes a continued cbrunicirritation of botb various defense cells and the fihro-blasts, resulting in eventual pulpal necrosis.™

As a definitive restorative agent, RMGIC was usedin ali conventional treatment groups to decreasemicroleakage, hecause of its antimicrobial effects andbonding capacity to the tooth structure. However,fewer stained bacteria were ohserved in the AS-treatedpuips tban in tbe conventional treatment groups, sug-gesting that dentin hybridization is the prime factor inpreventing microleakage and promoting healing.

There were 14 inflamed pulps in the AS group, hutoniy 8 of these pulps showed stained bacteria. A con-ceivable explanation for this difference is tbat somebacteria on the tissue section did not stain or werevisually undetected but released toxins tbat accountedfor tbe inflammation." Another possibility is thatinfiammation was the consequence of small resinglohules that were ingested by various of the underly-ing pulpal cells."*

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Clinical examination revealed no signs or symp-toms in any of the treated teeth, suggesting a cliniealsuccess rate of lOO 'o, However, light microscopy ofthe FC group showed complete histologie fixation ofthe pulp, confirming previous data that FC is a fixativethat does not promote healing,"

For mechanical support over the exposed andcapped pulpal tissue and to prevent pushing of thedefinitive restorative agent into the underlying pulp, itis strongly advised that the clinician place several thinlayers of a flowable resin composite, a compomer, or afilled adhesive and then photocure at a low energylevel before placement of the definitive restoration.

The data from the present study show that pulp-otomy appears to be a successful procedure when theAS system is used. This represents a paradigm shift forthe profession, from the routine use of toxic materialssuch as FC, which fixes the pulp and causes a muta-genic response, to the use of longlasting, biocompati-ble systems that employ cohesive hybridization tech-nology to achieve highly predictable success rates.

CONCLUSiON

1, On the hasis of this study, NaOCl appears to pro-vide proper hemorrhage control and to promote aclean dentin surface, free of organic biofilm,

2, On the basis of this study, the AS does not causeirritation or impair the normal healing of monkeypulps when placed as per ISO usage guidelines,providing for cellular and soft tissue reorganizationand dentin bridge formation,

3, A new dentin bridge may form adjaeent to the AS-pulp interfaee, vidthout the presence of a Ca(OH);medicament,

4, Long-term success is compromised by baeterialmicroleakage,

5, An alternative to FC is RMGIC, which can be usedas an immediate provisional medicament over theexposure, a definitive restoration over Ca(0H)2pulpotomy, or as an alternative to zine oxide-eugenol or a crown in primary teeth.

6, These data support the use of AS as a very promis-ing treatment option for the sealing of pulp-otomized pulps.

ACKNOWLEDGiUiENTS

ThLs study was supported in part by the University of Alabama atBImimgliam, Grant Nos. 638118 and

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