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Root canal fillings with zinc oxide-eugenol cement in the rat molar
Root canal fillings with zinc oxide-eugenol cement in the rat molar
E
xpcrimental root canal treatments in the rat. molar have provided an opportunity to st.udp the reaction of periapical tissurs to different root canal filling materials. Tn ortlcr that this might bc accomplished? a rea.so~~abl~high number of animals and a standardized operative proccdnre were used to limit t.he variables involved. Experiments were conducted with various root ca.nal materials, and reports have previously been published regarding this matter. ‘-a In further studies t.hst arc now under way with an additional. series of animals, Grossman’s sealer? Bickcrt’s cement, Kloropcrka N-6, N2, diverse resorbablc pastes, and some rpoxy resins are to bc used as root canal fillings. For this report, WChave selected the reactions encountered with zinc oxidecugenol ccmcnt ilS a st.anda.rd of comparison with other root, canal materials menConed above. MATERIALS
AND
METHODS
A total of 141 male and female 2-month-old Wistar rats were used in the csperimmt. For this study, a.Cmals were divided into eight series and killed at different observation periods after completion of root canal t,reatment,. The number of animals varied from IO to 35, and the observation periods ranged from one to 90 days. The technique employed h&qbeen described previonsly.‘-S RESULTS
Tissue reactions caused by root canal filling with zinc oxide-eugenol cement (1) the root., (2) t.he periodontal ligament, (3) the alveolar fundus, and (1) thcl adjacent. bone tissue will be described. in
This study was supported Research, United States Puhlie *Proftwwr of Histology.
by a grant (02290-01) Health Service.
from
t.hc! Sstional
lnstitute
of I)eut.al
547
Changes
in
the
root
In twenty animals thcrcl WYlS invagination of periodont.al t.issuc within t.ht! root canal. The cxtcnsion of t-his tissue increased acbcording to the Icngtt1 of t.ho postopcrativc period. I lowt33~r. in no case did t,his ingrowth reach far hcyond the apex. In six spccimcns p(?riodontal tissue ingr0wt.h following 4 and 7 days of observation averaging 150 microns in length was found. In two specimens, aft.cr postoperative observation pcriotls of 60 and 90 days, rcspect.ivcly, thth ingrowth of periodontal tissue reached 600 microns. The invagina.t.4 gcriodon t a 1 t issu(l showed an abundanrct ol’ small and
1
Kg. 1. Large overfilling (o), necrosis of cementum (on) and bone (bn) at fundus of alveolus, resorption of alveolar fundus and osteowlerosis (OS) in underlying bone marrow in and eosin stain. Ma,gnification, 60-day-old rat. Postoperat iva period : i days. (Hematoxylin x60 ; reduced s.) Fig. 3. Overfilling of zinc oxide-eugenol cement (0) mixed with dentinr chips partially occupying alveolar fundus. Note necrosis of apical periodontal ligament (NFL) and alveolar bone (HiV). Sixty-day-old rat. Postoperative period: 2 days. (Hematoxylin and eosin stain. Magnification, x80 ; reduced !&J
C]OIL$I~~C~ fihrob1ast.s. Polya7orphonuclear Ienkocytrs ~1’1’1’frequently ~~77 in 1:lose eont.act, with t.hc root, canal material. &ncath this zone, n~7m~ro77~71~crophagw with pol.ymorphonuclear lcnkorytcs irlgcsted in their cytoplasm WN oft1171 pwscnt. Nwrosis of the ccmcntum (E’i g. 1) in roots ohtmattd with ni77c ositlt? ougwiol wmcnt was extensive and fwyuent. Thcsc nccrot.ic al’crls wclv fou11cl in the inner layxs of ce7ncntu777 after 2-l ho77r.9and contin7wd spreading out towirtl t,Iic oubcr layers up to the fourth day. Scvcn days postoperatively tlicsc nccrot ii* areas did not extend any f77rther. They were found in val’ying dqyws, hnt with high frqnency. Of 103 specimens sttndicd microscopi1~al1~-, 96 shomcd necrosis 01 rcnientum. Ci~Il1cI1tL7l17 wsorpt.ion orcLlm?d frequently and took place following niwosis. The first appeared 7 days following thr root canal tw~ttncnt, and fo17r oat of thirt.v-fiw animals showed ccment77m rrsorption at this time. After longw postoperative periods ccmentum resorption incriwsed in frrquenry. Of fifty-foul* animals killed after 30, 60, and 90 days, thirty+ight sl~owc~l wmentnnl rcsorpt&m, and in thirty of thrm the 7*esorptivc process was so screw that it Icft th1k zinc oxidc-cugenol ccIneI1t. esposccl and in tlirwt contact with the pl?ViOdoIltill ligament.
was rclatiwly raw alit1 orcnrred later. It was ~coforll7atioI7 of cenii~ntL7ln observed after 15 days, and it occnrrcd in right. of thcl nnimnls studird iu this cntiw cspcriment. Somctimrs newly formcxl w7771wtnm was found dcpositotl owr ncrrotic cementum. Changes
in the apical
periodontal
ligament
t%:erfi/led nmtericrl. More than one half of the 141 specimens studi sl~~w’~d 1nwfilli1igs with zinc* oxide-rngiw)l ri~iw77t. In sixty-sewn of them tlic overfilling did not reach the fwidus of the R~~COIUS, wlicrcas in s1wn it. was in contact with it. In thrco spccinicns 1’rii~mciits of zinc osidc--c~li~ciiol iwiic7lt. wre found l&c!d in the lx)iic marrow, and in 07ie it was detcctcd iii the ln;lndil~L7lar canal, conlpressing the infri%)r a I ~rolai* ni’rw. 171 the lll;ljorit~ Al’ PIHPS (fifty-tW0 017t of scwnty-two j, tlic o\-wfillcd mass of zinc osidc--rn~1~7iol wnii~nt was fonnd niisrcl with d1~7iti7ir tilings lwotluwd duriilg Illl~~tlil.tli~~ll inst1~uirli~iltation (Fig. 2). As a 1’~7111, the 1nwfillings wew dcnsc in appraixnrc. a1tlio77gl7 in som11spccim1w Yoot l’illlill 1)) they appva red t.0 IJC scparatd Rain tlw fillin, II milt(~i+il inside tllr il. crack whirl1 llwanlc~ wider in suhscqucnt postoIwrati\c Iwriods. In WVIW 01 the fifty-two cils1ls i77 whi1*17tl7c zinc osidc-cwgcnol ccnlcwt was m&cl with clcntine chips, tlw ovcrtilled inatrrial was fo771111swttcwd throughout the Iwiapic~al tissnes (Fig. 3). Ke.~po~tw of th.e apiwl lJf&don tul tiss Me. NVln7cw~r the tilling was we11 short of the tipes, the tissue ad.jacc77t. to tlw apical f0ra1i71~n was practically noinial. ~~071v1~sc1~. mhcn zinc’ osi1l1~-i~ngr7iol iwi(~iit and Clinti47is 1*;iusctl by the mrchaaiCal instr77lneIltatioIl c5tcIlClcd I~eymd th apes, ail illflilllllll;ltlJ~~ lYVl~~tiOl1 ii1 th pcriapical a rc8 was friryurntl,v 1~bscrv1~d( Fig. -I) . Dnring the first. da>-, il pOl~l1lOrpllOIlL7~ltW~ lculroc~tic~ infiltrate was priaeiit in the iIlWL ad.joiaing tllc OWrfillCd Illilt(?Yiill. AI’ter ‘i tlil)%, I~lllpllOc~t.eS 2tIld niacrophages appearetl in the nior’c CliStilIlt ill’(lils ( Fig. 4). This hctc~i~ogclious in-
Fig.
4
filt.rate was present 15 days postoperatively in many spec+nms. After 30 cl;~ys. howe\‘Pr, it was found to 1~ luarkedlv reduced. In several instances small periapical granulomas wcw seen. These ncoforrnations sometimes showed fibrous encapsulation surrounding the ovefill~d matt?C;ll. In postoperative periods of up to 15 days, the capsul(a was composed of loonr connective tissue containing cellular infiltrate and the ovezf?lled mat.erial ( Fig. 5). After postoperat.ive periods of more than 30 days, the rap&e appeared, in some areas, to he in direct rontart with the orcrfilled zinc oxide-cugenol rcmcwt (Fig. 6).
Fiq. 5. Poorly organized fibrous capsule around root apex fC). Between capsule a.nd ziuc: oxide-eugcnol root canal filling, mild inflammatory cell infiltration is dill present. (arrow I. Sixty-day-old rat.. Postoperative prriod: 30 days. (FIcmat.ox~l~n and (losin stain. YRgnific:ttion. xi0 ; refluwd W.) Fig. fT. Fibrous conneetivct tissue capsule IC) surrounding overfilling with zinc> oxide,wgenol. Not.e cementum resorption. New hone traheculae arc seen at, alveolar fundus (XI{). Xixt.yday-old rat. Podoperat.ivr pwiod: 60 days. (Hematoxylin and rosin stain. Magnifk~at.iou. xi0 ; rraucwl I,&.,1
Atnottg animals killed after postoperative periods of 1, 2, and 4 days, necrotic connective tissue was found in the periodontal ligament of seventeen specimmx. This tissue rca.ction was not observed after the seventh post.operatirc day. Necrosis,
resorption,
and
neoformation
at the alveolar
fundus
Xecroais. A very common finding 1, 2, 4, atttl 7 days postopcrativcly was the presence of necrotic bone at t.hc fundus of the alveolus. Thirty-ttine of screnty-three animals showed this necrosis (Fig. 2). Tn almost every (‘asp the necrotic proccas was observctl when the ovcrfillctl mass of zinc oxide-cu~(~ttol was in contact with or very near t.he alveolar fundus. Resorption. The removal of the alveolar fundus, p;l.rticularly when the boric was ttclrrotic (Figs. 1 and 4), was mat*kcd and was found very frryucttt.ly after a 7 day postopc~rati\c pcGod. This phcttomc?ttott was obscrvt~l in twrttt.y-four of thirty-tivc animals. Most, oft.ctt we wllrc dcalittg with an ostcoclustic rcsorptiott originating in the iIpir>tl periodontal ligament. In those specimens in which the ovet$lling of zinc c,sitlc-cngcattol wits in direct cottt.actt. wit.h the alvt~lar ftttttltts. bottc~ t*esorption
Volume 24 Number 4
il), After 60 and 90 days, it brran~c difficult to distinguish newly fomrd 1w1w from the old, but it was noted that the fnndns of thr alveolus was thicker and that the underlying mrdullar spnccs wwc smaller. DISCUSSION
The rcquiremcntn for a root canal tilling material arc well known, and have been rcport.rd by many authors. SOIW of thaw Irquiuwwnts (case of prepapation. insertion, and removal, radiopacity, etc.) i\r(’ of interest. from the cliniral point of view. The discussion hcrc will bc limited to thosr p’ropcrties of root canal tilling materials related to tissue XTilctiOIl. (:cnerally speaking, the requirements in t.his rcspcvt are hermct.ic svaling of the ranal and good tolerance of the adjacent tissues to the. material used. ITarmetic sealing depends on several factors, such as: (1) plasticitp of the matcvial at. the tirnc of its insertion into the canal, (2) dimensional stability during and after setting, (3) adhesiveness to the canal walls, (4) i~llpermcahilit~ md insolnhility in tissue fluids, and (5) resistance to resorption. (:ood tolerance of the periapical tissues requires that the root canal filling n1atcria.l br antimicrobial in action and that the inflammatory or dystrophic tissue reaction induced by the pa&c br slight, so as t.0 pclrmit the rapid diffcrent.iation of an enduring tissue (1)~ it fibrous or calcified) al>out the matclrial. Plasticity
of the zinc oxide-eugenol
cement
Apparently, this rcquircmalt \vas covc~*tttl satisf;Ictorily. Tbr zinc* osi& cugenol cement employed was casil~~introduced within thr root canal by means of a spiral (lentulo) or with t.he Ilcdstriim file, Gthout losing its plasticity.
Wiwoswpir
stutly
~‘allill WillIS.
ol’ s~~c~ciir~ms
CV(‘11 WllClI
Dimensional
stability
tll(‘?
\V(‘I’(’
of zinc
~1Jow~~~l
tht
Ihis
Jllistul~v
idaptcd
to
tlw
Iwi
\V(>t 01’ Ill1(3\‘(‘11.
oxide-eugenol
cement
during
and
after
setting
Zinc ositlc--cuacaol fillings IlSllilll~ sho\vcvl vlupty spaivs and fissul*Cs whit+ separatrd them from the dcntinc WIIIS of the (*anal. &lost. of the spaces noted in this stndy wctv art.it’;Ws c~nscv~ hg thv histologic tcrhniqnc and induccv~ hy thr Ila Vdncss Of tllc CilllUl \\aIlS ivlat ivc> to thr bl*ittlcncss of t,llC zinc oxit&c~ngenol iltld src~lioJlin~ of the spwinirns. after histologic~ ~Wpill’kIti~Jl Tluwfo~~c~, it, is quite ymsible that SOI~(~ of thwc fiSSIlJW4 al’o th l*twlts of shrinkage ol’ the matctG1. 111 somcLWSCH,howrvrr, ~vn in those ot’ long postopeixti\-cl dnration, tliv rnatvrial iI~)~~C'illYYl as il dcbnsr mass filling thr vr211HI. Adhesiveness
of the zinc oxide-eugenol
to the walls
of the root canal
it is diRicult lo vvaluatc thta dc?grc~~of adh~~xivcnvss to ihv root c*nllaI cWn(Wt wil Ils f~)l’ il givcvl material, 0111’findings Ivvvit Icd that zinc osid(~---(~~i~(~~~ol 1121s H ])OO” dcgl*Pt! of ;Idhvsivc~nr,ss. Most Of tlltb fiSSllI~C~S ilJl1lt’il I’d hPt WXW tllV i!ltllOl~gh
zinc:
osii~c-?ugcnol
to indivatc
cTwc~llt
illld
that thr niatc~ri;ll’s
th
root
wnal
WJIh
stivngth
ildhWiVV
( b’ip.
8),
WhiPh
WOllld
is Icss than its ivsistanco
SW111
to
I’twtu1*c.
Impermeability
and insolubility
of the zinc oxide-eugenol
cement
in tissue fluids
I luring tha postoperat i\c periods sllAv1 in this c3pcbrin~rnt, ;I maximum 01’ 90 days, thr zinc osidc-cugc~nol cement fillin, (I thr root canal sl~o~c~tl no signs ol sohlbi1it.y and/or pcvmcahility to body fluids. Thr la~*gr wlpty spacw frrqwnt I!insertion of zinc osidv -vngcnol cvmrnt in thv ldt. b,v thr in,utrumcW following vanal did not provoke iin)- visihlv react ion in the surrounding t,issutx Resistance
of zinc oxide-eugenol
cement
to resorption
\\~honever this material ha~dcncd to a dense nlass, it showed great rclsistancv lo resorption. Clonvcrscly, if it, hccame niixcd wit.11 tissue fluids? blood! or detritus, it was more rapidly resorbed. The mass of overfilled material, when it. bcra.mc mixed with det.ritus, frquont1,~ projcctcd beyond the apt’s during the operatic procedure, provoking ~JI inhwsc lwwtion. The zinc osidcvugcnol was lnor’c rapidly resorbed in thcsc spccimans than in those in which it set lnorc densely within the canal (Fig. 1). The gJ*oatcr wsistancc of th Jnatcrial hardcncd wit.hin the root canal was corrohoratcd in numerous inst,anccs wlicrc~ ostcoelastic clcmcnts in pcriodonia I ligmncnt resorbed the comcntum and dentine throughout its total thickness, lcavinp cxtcnsive zones OS zinc* oxide -cugcnol cement in direct contact. with thv pc~riodontal ligament. No signs of jvsorpt,ion of the filling mat.rrial wcrc found in these specimens. InRammatory
reaction
of periapical
tissues
to zinc oxide-eugenol
cement
%inc osidc-cugcnol venivnt was found to hc highly tosic to thr piGlpicaI tissues. This cvynvnt (*ilrls(ld ncvrosis of’ 1IW hard tisqsut&swith which it. (*anl(l iI1
Wmtac*t.. ~\‘llcVl the mesial root. Callill in tile C1.t ~IlOl;l~ was fillctl with this WltlC~lt. its effcrts &ended hcpond the dcntine to the c.cmentnm, which bc?camclc>st.enxivch1.vncrrotic (Fig. 1 ). Also, tbc?hone at the fundus of the alvcol77s or thcl surrounBing rancc~llo77sbone trabecula was fo77nd to be nrcrotir. when the m:ltehl passcvl 1~y~ncl the apical foramen eit.her adjoining or near the bone tissue. %iHca vsidc~--c77gcnvl rcment brought about intense tissnr rc~aetions in th(b c~onnc~ct~ivrtissue of the apical periodontal Iigamrnt. The initial proc~s, particnlarly iIc!tivc? in eases of o\-erfillings, was nc~crosis of the apicaal pl~riOtlc~lltilI Iigamont. This ncAcrosis continued to be observed 1, 2, and 4, da,~s postopclrilt i\-(bly. .jftrr 7 days, 17owever, the necrosis was replaced by 77~ tissucl. Out of thirt,veight spchcimens in the experiment, comprising postopc+r;lti\rI pclriocls of 711)to 4 (lil)%, necrosis of the! apical periodorital ligament was found i77 srvc~ntcrri instanc*es, whcxreas riot a singln instance of nnerosis was found s7no77gthr .I():3 animals studied after postoperative pc+ods of more tlia77 4 days. Wl7er7 thcl periapical connective tissue did not bc~rvn7c!nc~rr’otic~,or wl~n thcl necrotic ~11s were fonnd to be replaced by regenc~ratcd tissucl, a polynorpho7177c~lc~il.l~ lc~ukocy-tc infiltrate appeared in direct contact with the zinc* osiclc~~~qqmd, which lstclr w;7s phagocytlxcd by the mi7crvphagcs. S,c~verala77thors fvuud ii similar rcactivn c*ovcring pulp c~sposurcs”~i and pulp all71)lltatio77s”-” with zinc osid+c~ugenol in t.he rat at different postoperative pclriocls. Rerman,* Mi>Tamoto,” and Koz~o\’ and NBSS~CI”” ol~si~rvc~da small inflamrnatory ~077~ ilfter pulp ;lmp77tation, wit17 polymor~~honu~leur leukoeytcw prcae77t that the nunlh~l~ 7 and 14 days post.operati\-c?l-. Hc~rman and Masslc~r” 1qmed of poI~u7or~~l~o77nclear lcukoeytes was greatly 7*cd77c~t~tl aI thr ~7ld of I4 tlilvs, il77tl il I’tl>l* 2 I lIii)X thesc~Cells wl!I’c 110 1077gcbr cvidcnt. Thcl inflammatory reaction of the periapical connective tissue was mvr~ SCvt~rcLwhen the zinc3 oxicle-ougcnvl Cc~ttii~ntllP~illlll~ misc~d with detritus PilLlSlVl by 7riec~lianic~al inst.rLlmc?nti~tivn (Fig. 4). I’ol~n7orpl~on77~lc~a~~Ic~ukocytc~s and ll7ilCW~~llil~l~S Wl’W Vcr- abnndant and Wl’1’0 pTYhill~l~ alA t0 disilltcglxtt? alltl rc?sorb thca material. In son7c spcG77ens, this procaess prorokecl the resorption of the v~i~ilillcd mass, while in others an ingrowth of periodontal tissiic within t.h(t root ranal was detected (Fig. !I). The zinc* osidc~c~ugenol ecxmc>77t. ~;177~cl 0111.~ii Il7vdtl7*iltcl atnv7177tof cli~ll7a~c~tl tissue. Although the caemcnturn underwent necrosis throughont. its total thickncss. it tl7ily 1~ worthy of mc~ntion that in n7any spccin7cns this tissutl in the lnolill* vt’ t 1711rat, is not. more than 200 microns in thickness. The infiltrated conncx+vc tissue of thcl pcriapiral aol7e became s77rroundcd by a rather thin granuloma tons layor which, after 30 days, showed a tendency to clifferentiatc~ ir7tv a fihrons c%])sule in ill1 attempt to lvcalixc~ the periilpiesll tissue reaction. Tosir ilcat.io71of zinc vxiclct-cugenol was pcrsistcnt, illld ]~Ol~~~OP]~1ll~~lL7~lt~il? i~lfiltl?lt~~, wllich genel*all,v did not decri~sc~ until 15 dayshad elapsed, WilS found in dirclct eontact. with the overfilled material. This inflanlmatoyv reaetiotl of the periodontal tissncs appeared to hr more severe than t hc WS~OI~Wto implants of zinc! oxid+tlngc~nvl iaemcbntin tt7tl snbcntaneo77s tissnc‘ Of thr rat clc~sc&~(~cl1)) SOlIll’
HLlthOI’S.”
()77 the other
I:( lliln~l,
niyq~otic~ hart1 tissnc+
must.
1x1 l*wOh?tl.
ttntl this pr0c~c~ss
requires time. In some SpccimcWs uc~c*rotic (~(Ltn~~nfuniwas seen to br covered wit.h new cementum, although this was not. a .fwqucwt finding. h’ew bone t,rabeculac were found drpositctl on thr ncc*rotic* IM~P at the alveolar funduw with even less fmyucncy. Biologic
isolation
of the zinc oxide-eugenol
cement
The persistent inflammatory rcac+on (!a\lscd by zinc oxidc-cugenol rcment, in the periapical tissues and the indurcd necrosis of the hard tissues delayed t.he differentiation of structures tending to isolate the ovcfilled material pcrmanently from the adjacent living t&urn. When the zinc osidc+ugc~nol prot rutlrtl thwugh t.llcaapical foramen, a fibrous capsulr was found rathw fwqucwtl~ to surround tlw overfilled material. An analogous fibrotic tendency was clescriht~~l atljaccnt to zinc oxide-eugcnol cement following pulp a.mputations in the rat molar.” This encapsulation traction tended t.o calcify early.“‘. ” IIn the periapical tissue, thcl fibrous diffrrcntiation was not in direct. caontact with the material but surrounded the defensive tissue composed of a rather loosr structure with numerous yol?rmorphonuclnar leukocytes and macrophages. E’urthermore, this fibrous capsule was ncvcr found to he dense enough to be consiclered an effective defcnsi\-c formation (Fig. 10). Necrotic hard tissues, on the other li;~wl, most of the time wwc found to he
IWOI+W~. This ~MCC?SS~(~rr~ti lat(xr ant1 was SO SIOW that 011 ma11~ o(*eilsiotls it had not finished after 90 days. Also, as a rrsalt of’ this rcasorption the xine oside+ugenol ccmrnt. nit.hin the root caallai was CsposC~Ito the periodontal ligilment tissues, which rithcr resorhcd thr zinc osidc-cugrnol (a(m(W or, IIIOPC: often, c~nca.ps,ulated it. ( Fig. 11 ) . A deposition of hard tissiws onto th zinc. osi++ugouoI to ohtilitl il. l)iologic* (*hJSllIT
Of
thP
l’OOt
iI])f?X
WiIS
11PVPl’
fOUlId.
1 II (JIlly
OIlC
iIlStaIlPP
Was
ii
zinc oxide-eugrnol pIVJjPc*td to\V~ld tllcl Il~~llliltO~~~IlOllS I)OIICb Illil1’1’0\V, deposition of a boric trahccula dirc~ct1.v onto the filling 1lliltCl’itll. of
fl’SglllPIlt
showing
SUMMARY
The hist.ologic ~cspo~lsc of pcriapical tissues to mot (*aI~aI fillings with xincb oxi&-cugcnol cemrnt was studied in the lowclr ~m~lars of rats. Root canal fillings wwc placed in normal trc>th of 141 W&tar rats, and the animals were killed at different postoperative periods rsnging from 24 hours to 90 days. Semiserial sections of each specimen wcrc madr, and, on the basis of the reported findings, the following conclnsions may hc drawn : Zinc osidc-engenol cement showed satisfactory propert.ics of plasticity a11r1 dimensional stability, hut it did not prove it.s adhcsivcnchss to the root canal walls.
REFERENCES dc*l IVlola~ tlv la Iht:i 1. Maish, O., and ~Ehausquin, .I,: li~~awihn tic 10s Tcsjidos I’wiapieah Alemt. 53: 1”-“o, 1965. a IHX Pastas dc Olhwacidn K~wl~sorl~iblw. Hw. ASO~. Odont. &wfillinp 2. Ivhmm’~l~al, M., Erausquin, J., and I)cvot,o, F. C. H.: A Study if Pcriapiwl in Root Canal Treatment in t.lw Molar of thtx Rat, Awh. Oral Riol. 11: 373-3X3, 1966. 3. Murux8ba1, M., and IXrausquin, .I .: Hcsponw of Pt+apic*al Tissws in thr R.at. Molar to ORAL MMJ. L OKAl. PATll. 21: Root. Canal FillinLrs With l)i;tk(bt ant1 X1-126. ORAI. sI!R(:.. 7X6-804, 1966. ” 1’. (‘. II., and R.iklrx, A. : Swrosis of the> Pwiodon1al 4. F:rausquin, J., Muruzhbal, M., Ihwh, I,ipamcant in the Rat, Induwd Ilv Hoot Canal Ovwfillings. d. I). Hcs. 45: lOH1- I 0X. 1966. a., and Muruz:iljal, ‘M.: A Method for R&t Canal Twatnwnt in tlJ& MO~:IJ 5. I.h&xquin, of t.lJrl Rat, ORAL. PlrW., ORAL ~~IJ. k ORAI. PAlW. ( 111 prws. ) ti. Quiglc.v, M. H.: Thperinwntal DEW., Chl. NRIL 6 Kxposuw trf IlanlstcV I’UI~J, ORAl. (h<.Il,
I’AI’H.
9:
11%-1
131,
l%6.
II’. ‘I’.: Iuvest igation of the KiPWt of an ‘~:s}J~‘ritJlt~rlti~l (‘a7. lhrktx, G. W., and Knigllton, c*iurn I!.ydroxidn Mixture vs. Zinc Osidcl sntl lhgcwol in fhc Twatnwnt of Rat Molar Twt,ll ~‘ollow~~ig Pulp hposuw, Virginia I). 5. 41: 5-l 1, 19.5.&. A. HrJ%Jan, 1). H.: Fact.ors Inflwnch~ Pulpal i-I-Ilaling ~Vollowing Furgicel .\ntputatiotl itj t&t Molars, Masttsr of Scienw Thwis, I!niwrsity of Illinois, College of Ihtistry, 195;. 9. Mivamoto, 0 .: Pulpal Rtwtioll Following Hurgwal AmImtation in Rat Molar, Martw of ~~~~~a~~c~e Thwis. Univwsitv of Illinois. Collw(~ of hwtistrv. 1957. 10. 11. 1 2. IX
hrnia~~~ I). R;, and Masslw, M.: F:slwrinwntal t2A-212, 19%. Mitc*hrll, I). I”. : ‘1’11(~lrrital iow~l Qualitirs Rappapnrt, htc*rials.
H. M., CkAl.
sVR<:.,
IAlly, Ol
I’ulpton~iw elf Ihtal
(+. IL, ant1 Iiapsin~alis, ~~EI). % ()KAI. i'ATll. 18:
in kat. Molars, XIHf~nl.iillS,
l’.: i%-X02,
‘I’oxic*it.y 196l.
.I.
of
:\rh.
.I. I). 1tt.s. 37: lh11.
.I.
59:
b:rl~lotlonti~~ ‘Pilling
E
xpcrimental root canal treatments in the rat. molar have provided an opportunity to st.udp the reaction of periapical tissurs to different root canal filling materials. Tn ortlcr that this might bc accomplished? a rea.so~~abl~high number of animals and a standardized operative proccdnre were used to limit t.he variables involved. Experiments were conducted with various root ca.nal materials, and reports have previously been published regarding this matter. ‘-a In further studies t.hst arc now under way with an additional. series of animals, Grossman’s sealer? Bickcrt’s cement, Kloropcrka N-6, N2, diverse resorbablc pastes, and some rpoxy resins are to bc used as root canal fillings. For this report, WChave selected the reactions encountered with zinc oxidecugenol ccmcnt ilS a st.anda.rd of comparison with other root, canal materials menConed above. MATERIALS
AND
METHODS
A total of 141 male and female 2-month-old Wistar rats were used in the csperimmt. For this study, a.Cmals were divided into eight series and killed at different observation periods after completion of root canal t,reatment,. The number of animals varied from IO to 35, and the observation periods ranged from one to 90 days. The technique employed h&qbeen described previonsly.‘-S RESULTS
Tissue reactions caused by root canal filling with zinc oxide-eugenol cement (1) the root., (2) t.he periodontal ligament, (3) the alveolar fundus, and (1) thcl adjacent. bone tissue will be described. in
This study was supported Research, United States Puhlie *Proftwwr of Histology.
by a grant (02290-01) Health Service.
from
t.hc! Sstional
lnstitute
of I)eut.al
547
Changes
in
the
root
In twenty animals thcrcl WYlS invagination of periodont.al t.issuc within t.ht! root canal. The cxtcnsion of t-his tissue increased acbcording to the Icngtt1 of t.ho postopcrativc period. I lowt33~r. in no case did t,his ingrowth reach far hcyond the apex. In six spccimcns p(?riodontal tissue ingr0wt.h following 4 and 7 days of observation averaging 150 microns in length was found. In two specimens, aft.cr postoperative observation pcriotls of 60 and 90 days, rcspect.ivcly, thth ingrowth of periodontal tissue reached 600 microns. The invagina.t.4 gcriodon t a 1 t issu(l showed an abundanrct ol’ small and
1
Kg. 1. Large overfilling (o), necrosis of cementum (on) and bone (bn) at fundus of alveolus, resorption of alveolar fundus and osteowlerosis (OS) in underlying bone marrow in and eosin stain. Ma,gnification, 60-day-old rat. Postoperat iva period : i days. (Hematoxylin x60 ; reduced s.) Fig. 3. Overfilling of zinc oxide-eugenol cement (0) mixed with dentinr chips partially occupying alveolar fundus. Note necrosis of apical periodontal ligament (NFL) and alveolar bone (HiV). Sixty-day-old rat. Postoperative period: 2 days. (Hematoxylin and eosin stain. Magnification, x80 ; reduced !&J
C]OIL$I~~C~ fihrob1ast.s. Polya7orphonuclear Ienkocytrs ~1’1’1’frequently ~~77 in 1:lose eont.act, with t.hc root, canal material. &ncath this zone, n~7m~ro77~71~crophagw with pol.ymorphonuclear lcnkorytcs irlgcsted in their cytoplasm WN oft1171 pwscnt. Nwrosis of the ccmcntum (E’i g. 1) in roots ohtmattd with ni77c ositlt? ougwiol wmcnt was extensive and fwyuent. Thcsc nccrot.ic al’crls wclv fou11cl in the inner layxs of ce7ncntu777 after 2-l ho77r.9and contin7wd spreading out towirtl t,Iic oubcr layers up to the fourth day. Scvcn days postoperatively tlicsc nccrot ii* areas did not extend any f77rther. They were found in val’ying dqyws, hnt with high frqnency. Of 103 specimens sttndicd microscopi1~al1~-, 96 shomcd necrosis 01 rcnientum. Ci~Il1cI1tL7l17 wsorpt.ion orcLlm?d frequently and took place following niwosis. The first appeared 7 days following thr root canal tw~ttncnt, and fo17r oat of thirt.v-fiw animals showed ccment77m rrsorption at this time. After longw postoperative periods ccmentum resorption incriwsed in frrquenry. Of fifty-foul* animals killed after 30, 60, and 90 days, thirty+ight sl~owc~l wmentnnl rcsorpt&m, and in thirty of thrm the 7*esorptivc process was so screw that it Icft th1k zinc oxidc-cugenol ccIneI1t. esposccl and in tlirwt contact with the pl?ViOdoIltill ligament.
was rclatiwly raw alit1 orcnrred later. It was ~coforll7atioI7 of cenii~ntL7ln observed after 15 days, and it occnrrcd in right. of thcl nnimnls studird iu this cntiw cspcriment. Somctimrs newly formcxl w7771wtnm was found dcpositotl owr ncrrotic cementum. Changes
in the apical
periodontal
ligament
t%:erfi/led nmtericrl. More than one half of the 141 specimens studi sl~~w’~d 1nwfilli1igs with zinc* oxide-rngiw)l ri~iw77t. In sixty-sewn of them tlic overfilling did not reach the fwidus of the R~~COIUS, wlicrcas in s1wn it. was in contact with it. In thrco spccinicns 1’rii~mciits of zinc osidc--c~li~ciiol iwiic7lt. wre found l&c!d in the lx)iic marrow, and in 07ie it was detcctcd iii the ln;lndil~L7lar canal, conlpressing the infri%)r a I ~rolai* ni’rw. 171 the lll;ljorit~ Al’ PIHPS (fifty-tW0 017t of scwnty-two j, tlic o\-wfillcd mass of zinc osidc--rn~1~7iol wnii~nt was fonnd niisrcl with d1~7iti7ir tilings lwotluwd duriilg Illl~~tlil.tli~~ll inst1~uirli~iltation (Fig. 2). As a 1’~7111, the 1nwfillings wew dcnsc in appraixnrc. a1tlio77gl7 in som11spccim1w Yoot l’illlill 1)) they appva red t.0 IJC scparatd Rain tlw fillin, II milt(~i+il inside tllr il. crack whirl1 llwanlc~ wider in suhscqucnt postoIwrati\c Iwriods. In WVIW 01 the fifty-two cils1ls i77 whi1*17tl7c zinc osidc-cwgcnol ccnlcwt was m&cl with clcntine chips, tlw ovcrtilled inatrrial was fo771111swttcwd throughout the Iwiapic~al tissnes (Fig. 3). Ke.~po~tw of th.e apiwl lJf&don tul tiss Me. NVln7cw~r the tilling was we11 short of the tipes, the tissue ad.jacc77t. to tlw apical f0ra1i71~n was practically noinial. ~~071v1~sc1~. mhcn zinc’ osi1l1~-i~ngr7iol iwi(~iit and Clinti47is 1*;iusctl by the mrchaaiCal instr77lneIltatioIl c5tcIlClcd I~eymd th apes, ail illflilllllll;ltlJ~~ lYVl~~tiOl1 ii1 th pcriapical a rc8 was friryurntl,v 1~bscrv1~d( Fig. -I) . Dnring the first. da>-, il pOl~l1lOrpllOIlL7~ltW~ lculroc~tic~ infiltrate was priaeiit in the iIlWL ad.joiaing tllc OWrfillCd Illilt(?Yiill. AI’ter ‘i tlil)%, I~lllpllOc~t.eS 2tIld niacrophages appearetl in the nior’c CliStilIlt ill’(lils ( Fig. 4). This hctc~i~ogclious in-
Fig.
4
filt.rate was present 15 days postoperatively in many spec+nms. After 30 cl;~ys. howe\‘Pr, it was found to 1~ luarkedlv reduced. In several instances small periapical granulomas wcw seen. These ncoforrnations sometimes showed fibrous encapsulation surrounding the ovefill~d matt?C;ll. In postoperative periods of up to 15 days, the capsul(a was composed of loonr connective tissue containing cellular infiltrate and the ovezf?lled mat.erial ( Fig. 5). After postoperat.ive periods of more than 30 days, the rap&e appeared, in some areas, to he in direct rontart with the orcrfilled zinc oxide-cugenol rcmcwt (Fig. 6).
Fiq. 5. Poorly organized fibrous capsule around root apex fC). Between capsule a.nd ziuc: oxide-eugcnol root canal filling, mild inflammatory cell infiltration is dill present. (arrow I. Sixty-day-old rat.. Postoperative prriod: 30 days. (FIcmat.ox~l~n and (losin stain. YRgnific:ttion. xi0 ; refluwd W.) Fig. fT. Fibrous conneetivct tissue capsule IC) surrounding overfilling with zinc> oxide,wgenol. Not.e cementum resorption. New hone traheculae arc seen at, alveolar fundus (XI{). Xixt.yday-old rat. Podoperat.ivr pwiod: 60 days. (Hematoxylin and rosin stain. Magnifk~at.iou. xi0 ; rraucwl I,&.,1
Atnottg animals killed after postoperative periods of 1, 2, and 4 days, necrotic connective tissue was found in the periodontal ligament of seventeen specimmx. This tissue rca.ction was not observed after the seventh post.operatirc day. Necrosis,
resorption,
and
neoformation
at the alveolar
fundus
Xecroais. A very common finding 1, 2, 4, atttl 7 days postopcrativcly was the presence of necrotic bone at t.hc fundus of the alveolus. Thirty-ttine of screnty-three animals showed this necrosis (Fig. 2). Tn almost every (‘asp the necrotic proccas was observctl when the ovcrfillctl mass of zinc oxide-cu~(~ttol was in contact with or very near t.he alveolar fundus. Resorption. The removal of the alveolar fundus, p;l.rticularly when the boric was ttclrrotic (Figs. 1 and 4), was mat*kcd and was found very frryucttt.ly after a 7 day postopc~rati\c pcGod. This phcttomc?ttott was obscrvt~l in twrttt.y-four of thirty-tivc animals. Most, oft.ctt we wllrc dcalittg with an ostcoclustic rcsorptiott originating in the iIpir>tl periodontal ligament. In those specimens in which the ovet$lling of zinc c,sitlc-cngcattol wits in direct cottt.actt. wit.h the alvt~lar ftttttltts. bottc~ t*esorption
Volume 24 Number 4
il), After 60 and 90 days, it brran~c difficult to distinguish newly fomrd 1w1w from the old, but it was noted that the fnndns of thr alveolus was thicker and that the underlying mrdullar spnccs wwc smaller. DISCUSSION
The rcquiremcntn for a root canal tilling material arc well known, and have been rcport.rd by many authors. SOIW of thaw Irquiuwwnts (case of prepapation. insertion, and removal, radiopacity, etc.) i\r(’ of interest. from the cliniral point of view. The discussion hcrc will bc limited to thosr p’ropcrties of root canal tilling materials related to tissue XTilctiOIl. (:cnerally speaking, the requirements in t.his rcspcvt are hermct.ic svaling of the ranal and good tolerance of the adjacent tissues to the. material used. ITarmetic sealing depends on several factors, such as: (1) plasticitp of the matcvial at. the tirnc of its insertion into the canal, (2) dimensional stability during and after setting, (3) adhesiveness to the canal walls, (4) i~llpermcahilit~ md insolnhility in tissue fluids, and (5) resistance to resorption. (:ood tolerance of the periapical tissues requires that the root canal filling n1atcria.l br antimicrobial in action and that the inflammatory or dystrophic tissue reaction induced by the pa&c br slight, so as t.0 pclrmit the rapid diffcrent.iation of an enduring tissue (1)~ it fibrous or calcified) al>out the matclrial. Plasticity
of the zinc oxide-eugenol
cement
Apparently, this rcquircmalt \vas covc~*tttl satisf;Ictorily. Tbr zinc* osi& cugenol cement employed was casil~~introduced within thr root canal by means of a spiral (lentulo) or with t.he Ilcdstriim file, Gthout losing its plasticity.
Wiwoswpir
stutly
~‘allill WillIS.
ol’ s~~c~ciir~ms
CV(‘11 WllClI
Dimensional
stability
tll(‘?
\V(‘I’(’
of zinc
~1Jow~~~l
tht
Ihis
Jllistul~v
idaptcd
to
tlw
Iwi
\V(>t 01’ Ill1(3\‘(‘11.
oxide-eugenol
cement
during
and
after
setting
Zinc ositlc--cuacaol fillings IlSllilll~ sho\vcvl vlupty spaivs and fissul*Cs whit+ separatrd them from the dcntinc WIIIS of the (*anal. &lost. of the spaces noted in this stndy wctv art.it’;Ws c~nscv~ hg thv histologic tcrhniqnc and induccv~ hy thr Ila Vdncss Of tllc CilllUl \\aIlS ivlat ivc> to thr bl*ittlcncss of t,llC zinc oxit&c~ngenol iltld src~lioJlin~ of the spwinirns. after histologic~ ~Wpill’kIti~Jl Tluwfo~~c~, it, is quite ymsible that SOI~(~ of thwc fiSSIlJW4 al’o th l*twlts of shrinkage ol’ the matctG1. 111 somcLWSCH,howrvrr, ~vn in those ot’ long postopeixti\-cl dnration, tliv rnatvrial iI~)~~C'illYYl as il dcbnsr mass filling thr vr211HI. Adhesiveness
of the zinc oxide-eugenol
to the walls
of the root canal
it is diRicult lo vvaluatc thta dc?grc~~of adh~~xivcnvss to ihv root c*nllaI cWn(Wt wil Ils f~)l’ il givcvl material, 0111’findings Ivvvit Icd that zinc osid(~---(~~i~(~~~ol 1121s H ])OO” dcgl*Pt! of ;Idhvsivc~nr,ss. Most Of tlltb fiSSllI~C~S ilJl1lt’il I’d hPt WXW tllV i!ltllOl~gh
zinc:
osii~c-?ugcnol
to indivatc
cTwc~llt
illld
that thr niatc~ri;ll’s
th
root
wnal
WJIh
stivngth
ildhWiVV
( b’ip.
8),
WhiPh
WOllld
is Icss than its ivsistanco
SW111
to
I’twtu1*c.
Impermeability
and insolubility
of the zinc oxide-eugenol
cement
in tissue fluids
I luring tha postoperat i\c periods sllAv1 in this c3pcbrin~rnt, ;I maximum 01’ 90 days, thr zinc osidc-cugc~nol cement fillin, (I thr root canal sl~o~c~tl no signs ol sohlbi1it.y and/or pcvmcahility to body fluids. Thr la~*gr wlpty spacw frrqwnt I!insertion of zinc osidv -vngcnol cvmrnt in thv ldt. b,v thr in,utrumcW following vanal did not provoke iin)- visihlv react ion in the surrounding t,issutx Resistance
of zinc oxide-eugenol
cement
to resorption
\\~honever this material ha~dcncd to a dense nlass, it showed great rclsistancv lo resorption. Clonvcrscly, if it, hccame niixcd wit.11 tissue fluids? blood! or detritus, it was more rapidly resorbed. The mass of overfilled material, when it. bcra.mc mixed with det.ritus, frquont1,~ projcctcd beyond the apt’s during the operatic procedure, provoking ~JI inhwsc lwwtion. The zinc osidcvugcnol was lnor’c rapidly resorbed in thcsc spccimans than in those in which it set lnorc densely within the canal (Fig. 1). The gJ*oatcr wsistancc of th Jnatcrial hardcncd wit.hin the root canal was corrohoratcd in numerous inst,anccs wlicrc~ ostcoelastic clcmcnts in pcriodonia I ligmncnt resorbed the comcntum and dentine throughout its total thickness, lcavinp cxtcnsive zones OS zinc* oxide -cugcnol cement in direct contact. with thv pc~riodontal ligament. No signs of jvsorpt,ion of the filling mat.rrial wcrc found in these specimens. InRammatory
reaction
of periapical
tissues
to zinc oxide-eugenol
cement
%inc osidc-cugcnol venivnt was found to hc highly tosic to thr piGlpicaI tissues. This cvynvnt (*ilrls(ld ncvrosis of’ 1IW hard tisqsut&swith which it. (*anl(l iI1
Wmtac*t.. ~\‘llcVl the mesial root. Callill in tile C1.t ~IlOl;l~ was fillctl with this WltlC~lt. its effcrts &ended hcpond the dcntine to the c.cmentnm, which bc?camclc>st.enxivch1.vncrrotic (Fig. 1 ). Also, tbc?hone at the fundus of the alvcol77s or thcl surrounBing rancc~llo77sbone trabecula was fo77nd to be nrcrotir. when the m:ltehl passcvl 1~y~ncl the apical foramen eit.her adjoining or near the bone tissue. %iHca vsidc~--c77gcnvl rcment brought about intense tissnr rc~aetions in th(b c~onnc~ct~ivrtissue of the apical periodontal Iigamrnt. The initial proc~s, particnlarly iIc!tivc? in eases of o\-erfillings, was nc~crosis of the apicaal pl~riOtlc~lltilI Iigamont. This ncAcrosis continued to be observed 1, 2, and 4, da,~s postopclrilt i\-(bly. .jftrr 7 days, 17owever, the necrosis was replaced by 77~ tissucl. Out of thirt,veight spchcimens in the experiment, comprising postopc+r;lti\rI pclriocls of 711)to 4 (lil)%, necrosis of the! apical periodorital ligament was found i77 srvc~ntcrri instanc*es, whcxreas riot a singln instance of nnerosis was found s7no77gthr .I():3 animals studied after postoperative pc+ods of more tlia77 4 days. Wl7er7 thcl periapical connective tissue did not bc~rvn7c!nc~rr’otic~,or wl~n thcl necrotic ~11s were fonnd to be replaced by regenc~ratcd tissucl, a polynorpho7177c~lc~il.l~ lc~ukocy-tc infiltrate appeared in direct contact with the zinc* osiclc~~~qqmd, which lstclr w;7s phagocytlxcd by the mi7crvphagcs. S,c~verala77thors fvuud ii similar rcactivn c*ovcring pulp c~sposurcs”~i and pulp all71)lltatio77s”-” with zinc osid+c~ugenol in t.he rat at different postoperative pclriocls. Rerman,* Mi>Tamoto,” and Koz~o\’ and NBSS~CI”” ol~si~rvc~da small inflamrnatory ~077~ ilfter pulp ;lmp77tation, wit17 polymor~~honu~leur leukoeytcw prcae77t that the nunlh~l~ 7 and 14 days post.operati\-c?l-. Hc~rman and Masslc~r” 1qmed of poI~u7or~~l~o77nclear lcukoeytes was greatly 7*cd77c~t~tl aI thr ~7ld of I4 tlilvs, il77tl il I’tl>l* 2 I lIii)X thesc~Cells wl!I’c 110 1077gcbr cvidcnt. Thcl inflammatory reaction of the periapical connective tissue was mvr~ SCvt~rcLwhen the zinc3 oxicle-ougcnvl Cc~ttii~ntllP~illlll~ misc~d with detritus PilLlSlVl by 7riec~lianic~al inst.rLlmc?nti~tivn (Fig. 4). I’ol~n7orpl~on77~lc~a~~Ic~ukocytc~s and ll7ilCW~~llil~l~S Wl’W Vcr- abnndant and Wl’1’0 pTYhill~l~ alA t0 disilltcglxtt? alltl rc?sorb thca material. In son7c spcG77ens, this procaess prorokecl the resorption of the v~i~ilillcd mass, while in others an ingrowth of periodontal tissiic within t.h(t root ranal was detected (Fig. !I). The zinc* osidc~c~ugenol ecxmc>77t. ~;177~cl 0111.~ii Il7vdtl7*iltcl atnv7177tof cli~ll7a~c~tl tissue. Although the caemcnturn underwent necrosis throughont. its total thickncss. it tl7ily 1~ worthy of mc~ntion that in n7any spccin7cns this tissutl in the lnolill* vt’ t 1711rat, is not. more than 200 microns in thickness. The infiltrated conncx+vc tissue of thcl pcriapiral aol7e became s77rroundcd by a rather thin granuloma tons layor which, after 30 days, showed a tendency to clifferentiatc~ ir7tv a fihrons c%])sule in ill1 attempt to lvcalixc~ the periilpiesll tissue reaction. Tosir ilcat.io71of zinc vxiclct-cugenol was pcrsistcnt, illld ]~Ol~~~OP]~1ll~~lL7~lt~il? i~lfiltl?lt~~, wllich genel*all,v did not decri~sc~ until 15 dayshad elapsed, WilS found in dirclct eontact. with the overfilled material. This inflanlmatoyv reaetiotl of the periodontal tissncs appeared to hr more severe than t hc WS~OI~Wto implants of zinc! oxid+tlngc~nvl iaemcbntin tt7tl snbcntaneo77s tissnc‘ Of thr rat clc~sc&~(~cl1)) SOlIll’
HLlthOI’S.”
()77 the other
I:( lliln~l,
niyq~otic~ hart1 tissnc+
must.
1x1 l*wOh?tl.
ttntl this pr0c~c~ss
requires time. In some SpccimcWs uc~c*rotic (~(Ltn~~nfuniwas seen to br covered wit.h new cementum, although this was not. a .fwqucwt finding. h’ew bone t,rabeculac were found drpositctl on thr ncc*rotic* IM~P at the alveolar funduw with even less fmyucncy. Biologic
isolation
of the zinc oxide-eugenol
cement
The persistent inflammatory rcac+on (!a\lscd by zinc oxidc-cugenol rcment, in the periapical tissues and the indurcd necrosis of the hard tissues delayed t.he differentiation of structures tending to isolate the ovcfilled material pcrmanently from the adjacent living t&urn. When the zinc osidc+ugc~nol prot rutlrtl thwugh t.llcaapical foramen, a fibrous capsulr was found rathw fwqucwtl~ to surround tlw overfilled material. An analogous fibrotic tendency was clescriht~~l atljaccnt to zinc oxide-eugcnol cement following pulp a.mputations in the rat molar.” This encapsulation traction tended t.o calcify early.“‘. ” IIn the periapical tissue, thcl fibrous diffrrcntiation was not in direct. caontact with the material but surrounded the defensive tissue composed of a rather loosr structure with numerous yol?rmorphonuclnar leukocytes and macrophages. E’urthermore, this fibrous capsule was ncvcr found to he dense enough to be consiclered an effective defcnsi\-c formation (Fig. 10). Necrotic hard tissues, on the other li;~wl, most of the time wwc found to he
IWOI+W~. This ~MCC?SS~(~rr~ti lat(xr ant1 was SO SIOW that 011 ma11~ o(*eilsiotls it had not finished after 90 days. Also, as a rrsalt of’ this rcasorption the xine oside+ugenol ccmrnt. nit.hin the root caallai was CsposC~Ito the periodontal ligilment tissues, which rithcr resorhcd thr zinc osidc-cugrnol (a(m(W or, IIIOPC: often, c~nca.ps,ulated it. ( Fig. 11 ) . A deposition of hard tissiws onto th zinc. osi++ugouoI to ohtilitl il. l)iologic* (*hJSllIT
Of
thP
l’OOt
iI])f?X
WiIS
11PVPl’
fOUlId.
1 II (JIlly
OIlC
iIlStaIlPP
Was
ii
zinc oxide-eugrnol pIVJjPc*td to\V~ld tllcl Il~~llliltO~~~IlOllS I)OIICb Illil1’1’0\V, deposition of a boric trahccula dirc~ct1.v onto the filling 1lliltCl’itll. of
fl’SglllPIlt
showing
SUMMARY
The hist.ologic ~cspo~lsc of pcriapical tissues to mot (*aI~aI fillings with xincb oxi&-cugcnol cemrnt was studied in the lowclr ~m~lars of rats. Root canal fillings wwc placed in normal trc>th of 141 W&tar rats, and the animals were killed at different postoperative periods rsnging from 24 hours to 90 days. Semiserial sections of each specimen wcrc madr, and, on the basis of the reported findings, the following conclnsions may hc drawn : Zinc osidc-engenol cement showed satisfactory propert.ics of plasticity a11r1 dimensional stability, hut it did not prove it.s adhcsivcnchss to the root canal walls.
REFERENCES dc*l IVlola~ tlv la Iht:i 1. Maish, O., and ~Ehausquin, .I,: li~~awihn tic 10s Tcsjidos I’wiapieah Alemt. 53: 1”-“o, 1965. a IHX Pastas dc Olhwacidn K~wl~sorl~iblw. Hw. ASO~. Odont. &wfillinp 2. Ivhmm’~l~al, M., Erausquin, J., and I)cvot,o, F. C. H.: A Study if Pcriapiwl in Root Canal Treatment in t.lw Molar of thtx Rat, Awh. Oral Riol. 11: 373-3X3, 1966. 3. Murux8ba1, M., and IXrausquin, .I .: Hcsponw of Pt+apic*al Tissws in thr R.at. Molar to ORAL MMJ. L OKAl. PATll. 21: Root. Canal FillinLrs With l)i;tk(bt ant1 X1-126. ORAI. sI!R(:.. 7X6-804, 1966. ” 1’. (‘. II., and R.iklrx, A. : Swrosis of the> Pwiodon1al 4. F:rausquin, J., Muruzhbal, M., Ihwh, I,ipamcant in the Rat, Induwd Ilv Hoot Canal Ovwfillings. d. I). Hcs. 45: lOH1- I 0X. 1966. a., and Muruz:iljal, ‘M.: A Method for R&t Canal Twatnwnt in tlJ& MO~:IJ 5. I.h&xquin, of t.lJrl Rat, ORAL. PlrW., ORAL ~~IJ. k ORAI. PAlW. ( 111 prws. ) ti. Quiglc.v, M. H.: Thperinwntal DEW., Chl. NRIL 6 Kxposuw trf IlanlstcV I’UI~J, ORAl. (h<.Il,
I’AI’H.
9:
11%-1
131,
l%6.
II’. ‘I’.: Iuvest igation of the KiPWt of an ‘~:s}J~‘ritJlt~rlti~l (‘a7. lhrktx, G. W., and Knigllton, c*iurn I!.ydroxidn Mixture vs. Zinc Osidcl sntl lhgcwol in fhc Twatnwnt of Rat Molar Twt,ll ~‘ollow~~ig Pulp hposuw, Virginia I). 5. 41: 5-l 1, 19.5.&. A. HrJ%Jan, 1). H.: Fact.ors Inflwnch~ Pulpal i-I-Ilaling ~Vollowing Furgicel .\ntputatiotl itj t&t Molars, Masttsr of Scienw Thwis, I!niwrsity of Illinois, College of Ihtistry, 195;. 9. Mivamoto, 0 .: Pulpal Rtwtioll Following Hurgwal AmImtation in Rat Molar, Martw of ~~~~~a~~c~e Thwis. Univwsitv of Illinois. Collw(~ of hwtistrv. 1957. 10. 11. 1 2. IX
hrnia~~~ I). R;, and Masslw, M.: F:slwrinwntal t2A-212, 19%. Mitc*hrll, I). I”. : ‘1’11(~lrrital iow~l Qualitirs Rappapnrt, htc*rials.
H. M., CkAl.
sVR<:.,
IAlly, Ol
I’ulpton~iw elf Ihtal
(+. IL, ant1 Iiapsin~alis, ~~EI). % ()KAI. i'ATll. 18:
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59:
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