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Effects of N2 in experimental endodontic therapy
Endodontics American
Association
of Endodontists
I. B. Btwder, Editor
Effects of NZ in experimental endodontic therapy David E. Snyder, D.D.X., Samuel Xeltzer, D.D.8., and l&hard illoodnik, D.D.X., Philadelphia, Pa. UNIVERSITY
OF PENNSYLVANIA
SCHOOL
OF DENTAT,
MEDICINE
R
oot canal filling material in the form of a paste (iodoform paste) was introduced in the practice of endodontics by Rose1 in 1894. Since then, the use of various kinds of absorbable and nonabsorbable pastes for the filling of root canals has been reported. Some pastes have enjoyed popularity for short periods of time but, in our opinion, none have had the impact or the popularity of the nonabsorbable paste known as N,, which was introduced by Sargenti and Richter.2 The term N, describes both the drug and the technique. In their book, Rationalized Root Canal Treatment, Sargenti and Richter2 have presented their view of pulp and periapical diseases and their method of treating them. The appeal in their approach is twofold : (1) The mechanical aspect of endodontic therapy is less demanding than conventional methods, with a consequent reduction in treatment time, and (2) the outcome of endodontic therapy becomes totally predictable. REVIEW
OF THE LITERATURE
Many reports relative to the efficacy of N, as a root canal treatment and filling agent are contradictory. Investigations of N, have been made on animals by Kuroiwa,3 Overdiek,7 Zerosi and colleagues,” Guttuso,s Rappaport and associates,G and the Council on Dental Therapeutics.4 Kuroiwa and Zerosi and co-workers were in general agreement that N, Medical and N, produced good results in root canal treatment. However, Kuroiwa limited his agreement only to uninfected teeth, stating that the material was not effective in the treatment of infected root canals. Guttuso, from
This investigation was supported by United States Public Health Service Grant DE 01930 the National Institute of Dental Research, National Institutes of Health, Betheda, Md.
635
636
Snyder, Seltzer, clml .VoodniX:
O.S.,O.M.8 0.1’. May,
1%x
Rappaport and associates, and the Council on I)entaI Tht~raprtuti~s agr~d that subcutaneous implant,s of N2 elicted a more se~‘erc inflammatory rc~sponsc~than other commonly used root canal mcdicaments and filling agents. On the othw hand, Overdiek found that N, was well tolerated by the periapical tissues and was walled off by a connective tissue ca.psule. Kuroiwa was unable to demonstrate such a connective tissue capsule around h’?. Both histologic and clinical inrest,igations on human teeth were c*onducted by Iten,‘” Overdiek,ll rC’icholls,” Kowc,~” Bermann and Ebersberg,” and Tschamer.‘” On the basis of histologic examination, t.here was no agreement as to the state of the remaining pulp &sue under an N2 filling. The reports raried; pulps were found to be necrotic, fixed, or caompletcly vital. Clinically, Nicholls, Rowe, and Bermann and Ebersberg all found fairly consistent pcriapical healing with the use of N2 filling material. Tschamer, howclver, reported a 71 per rclnt failure rate when N2 was used as a filling material. Bacteriologically, Rappaport, and colleagues” and Bertolini” found that N, was an effective antibacterial agent, against a wide range of microorganisms commonly found in infected root. canals. These findings are in direct contradiction to the report of the Council on Dental Therapeutics.4 Confronted on the one hand by the rat,hcr widespread interrst in the Tu’, method and its promise of total prrdi&ahility, a goal for which endodontists have been striving, and on the other hand by such vastly contradictory findings, we decided that another study was justified. An>- endodontic technique which promises that a granuloma (2;1nnot form after treatment, as Sargenti and Richter Thus, wc devised a study in ‘which hare claimed, invites an inrcstigation. comparisons could be made between the efficacy of the N2 method and t>hat of >I standard t,echnique simi1a.r to one used by most A4merican endodontists. METHODS
AND
MATERIALS
Three male collie dogs, of which two w’ere approximately 3 years old and the third about 5 years old, WWF used in this study. The animals were ancsthetized with intravenous Nembntal sodium at each operative session. Dog
1
The purpose of this experiment was to compare the results of root canal treatment with N, Medical dressing and N, filling wit.h the results of treatment with paramonochlorophenol dressing and silver cone filling in teeth with infected root canals and periapical areas of rarefaction. The maxillary and mandibular premolars were reduced from the occlusal surfa,ce to a plane below the functional occlusal lercl. The teeth were then opened through the occlusal surface with high-speed dry carbide burs until the pulps were exposed. The pulps were extirpated with reamers and files, and t,he teeth mere left open to t,he salivary fluids for approximately YI rnonths in order to induce periapical lesions. Roentgenograms were taken to determine the presence of periapical areas of radiolecency. During subsequent. treatments, each tooth was isolated under rubber dam and t,he field was wiped with tincture of Metaphen.
N2 in experime&l
Volume PI Number 5
endodontic therapy
637
The lnasillary and lnandibular right I)rernolars WCI-c rcamcd and filed with Sargenti’s root canal instruments, aceorhg to his inskuctions for the twatrntnt, of pnlpless teeth. The ranals w(‘r~3 twn.t,4 with N, i\lrdical, as a root r;lEl.l
dressing, and scaled temporarily with zinc osidc-cugc>nol. T\VO weeks latpr th(: canals were reinstrumcntcd and filled with N, according to the st,atcd instructions. The root canals of the maxillary teeth were filled close to the apical foramen, as determined radiographically, and amalgam restorat,ions were placed in the coronal cavities. The root canals of the mandibular t.eeth, although as well-dkbrided as those of the upper teeth, were filled considerably short of the apex, as determined radiographically. The maxillary and mandibu1a.r left premolars mere instrumented with standard reamers and files and irrigated with normal saline solution, after xvhich root ca.nal dressings of paramonochlorophenol were placed. Zinc oxidceugenol temporary fillings were inserted. Two weeks later the maxillary premolar car& were filled with silver cones and a silver-containing root canal cement.* The mandibu1a.r premolar canals were not filled. All of the treated t,ecth were sealed occlusally with ama,lgam restorations. The dog was killed 6 months later. Table 1 summarizes the significant data relating to trentmcnt, of the teeth of Dog 1. Dog
2
The purpose of the experiment on this animal was to compare the efficacy of the one-vist N, treatment with that of one-visit standard treatment in cases of chronic pulpitis. The pulps were exposed in all of the experimental teeth and these teet,h were left open to the salivary fluids for several weeks in order to induce a chronic pulpitis. The teeth were then isolated under a rubber dam a.nd the field was cleansed with tincture of Metaphen. The root canals of the mandibular left premolars were instrumented short of the apex and prefilling cultures were taken. The canals were flushed with normal saline solution, dried, and immediately filled wit,h N,. The culture results from these teeth were all positive. The root canals of the maxillary left premolars were similarly treated but were filled with silver cones and root canal cement. The maxillary second premolar was accidentally deleted from this study. The culture results were negative for the maxillary first premolar and positive for the maxillary third premolar. Ten weeks after pulp exposure, the root canals of the maxillary right prcmolars were instrumented short of the apex. Prefilling cultures were t,akcn. ‘Courtesy of S. Tancredi Pharmacy, Pl-‘hiladelplria, Pa. Powder
Silver, precipitated Stabelite resin Zinc oxide, chemically pure Magnesium oxide Fhgenol liquitl
30.0 .I5.0 “0.0 1.5
1
M
D
M D M D M
Upper left third premolar
Upper left third premolar
Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower
hi = Medial. D = Distal. PMCP = Paramonochlorophenol. - = Absent. + = Present.
right second premolar right second premolar right third premolar right third premolar right fourth premolar right fourth premolar left second premolar left second premolar left third premolar left third premolar left fourth premolar left fourth premolar
D
Upper left second premolar
,” D
M
Root
M
right first premolar right second premolar right second premolar right third premolar right third premolar left first premolar
Tooth
1. Dog
Upper left second premolar
Upper Upper Upper Upper Upper Upper
Table
Medical Medical Medical Medical Medical Medical PMCP PMCP PMCP PMCP PMCP PMCP
PMCP
PMCP
PMCP
PMCP
Medical Medical Medical Medical Medical PMCP
Interim dressing
180 180 180 180 180 180 180 180 180 180 180 180
180
180
180
180
210 210 210 210 210 180
Dwrattin of experiment (days)
Present Present Present Present Present Increase Increase Increase Increase Increase Same Increase Increase
f + + + + c + f
Increase
Increase
Increase
-
Change in status of periapical radiolucmoy after treatment
-
Presence of radiolucency following pulp removal
Silver and Silver and Silver and Silver and Silver and h-2 N? II-, x* II-2 N* Unfilled Unfilled Unfilled Unfilled Unfilled Unfilled
s; cone cement cone cement cone cement cone cement cone cement
filling
Type of root canal
7
6 4.5 6 3
2.5
1.5
3
Distance of canal filling from apex (mm.)
Mild Mild Moderate Mild Severe Moderate Mild Mild Mild Mild Milt1 Screw
Moderate
Mild
Moderate
Moderat,e
Mild Mild Mild Mild Mild Moderate
Degree of pe”riupical inflammation
2i0
270
270
Upper right second premolar
Upper right third premolar
Upper right third
330
180
180
D
11
D
11
D
M
Upper left third premolar
Lower right second premolar
Lower right second premolar
Lower right third premolar
Lower right third premolar
premolar
premolar
Lower right fourth
Lower right fourth
180
180
180
D
M
D
M
1)
Lower left second premolar
Lower left third premolar
Lower left third premolar
premolar
premolar
Lower left fourth
Lower left fourth
180
180
180
M
180
180
180
Lower left second premolar
D
330
Upper left third premolar
180
330
Upper left first premolar
premolar
270
to death
treatment
from
Upper right second premolar
Root
Days
330
Tooth
II. Dog 2
Upper right first premolar
Table
+ + + + + + + + + +
+ + + + + + + + + + + +
+
+
+
+
+
+
-
Culture 1-r~sults
-
Presence of apical radiolucency at time of death
Presence of apical radiolucency at time of treatment
Mild
s2
A?
s,
Srvrre
Moderate
Severe
Severe
Noderate x2 s,
Moderate
s, x\‘:!
Mild
Moderate
Mild
JIild
Moderate
Mild
Mild
Severe
Mild
Mild
Mild
Xoderate
Moderate
8 8
6
1
4
2
3
4
4
s,
cone cement cone cement cone cement cone cement cone cement cone cement cone cement cone cement
s,
SC
x2
Silver and Silver and Silver and Silver and Silver and Silver and Silver and Silver and s,
Type of fillin,/
The canals were then flushed nith norm;~l salillr s(jIrItiol-1 ;d drjd, aftc,r wtiicli silver cones were cemented into the canals with root canal W~~WI ‘I’hr cllltur~ results from these teeth were all positive. Twelve weeks after p~ilp cxposurc, the root (*anals of all the manditmlai premolars were instrumented short of the apex. Prcfilling cultures were taken, the canals were flushed with normal saline solution, dried, and then filled wit,h S!. Culture results from these teeth were all positive. The coronal cavities in all 01 the treated teeth were filled with amalgam. Table II summarizes trea.tment procedures and findings in the t,ecth of I jog Y!. Dog
3
The purpose of this experiment was t.o compare the state of the remaining apical pulp tissue in teeth with uninflamed pulps which had undergone standard endodontic treatment and root filling with that of the remaining pulp tissues after N, treatment. As a further control, t,he remaining pulp timue following partial pulp extirpation in unfilled canals was compared with the remaining pulp tissue in teeth with filled root canals. All of the premolars treated in this animal, as well as in the other two dogs, were free of caries and detecta,ble periodontal involvement. The teeth were isolated under the rubber dam, and the field was cleansed and wiped with tincture of Metaphen. The pulps tha,t were extirpated were all intact, and presumably uninflamed. The maxillary right and left prernolars were opened through the occlusal surface with high-speed burs and adequate coolant. The pulps were removed deliberately short of the apex. The canals were instrumented short of the apex, flushed with normal saline solution, dried, and filled with N,, also short of t,he apex. The pulps of the mandibular premolars were removed deliberately short of the apex and instrumentation was completed short of the apex. The canals were irrigated with normal saline solution and the mesial canals were filled with silver cones and root canal cement, short of the apex. The distal canals wern left unfilled. The coronal cavities in all the experimental teeth were filled with amalgam. Table III presents a summary of treatment procedures and findings in the teeth of Dog 3. Preoperative, treatment, and postoperative roentgenograms were taken of the teeth of all the animals. Roentgenograms of all the animals at the time of death are shown in Fig. 12, A, B, and C. The animals were killed by perfusion with fixatives between 6 and 11 months following the treatment procedures. Jaw blocks containing the treated teeth were then decalcified, embedded, and sectioned. Sections were cut at 6 microns and stained with hematoxylin and eosin. Serial sections were then examined microscopically. FINDINGS Dog 1
Upper right quadrant. The periapical which had been treated with N, Medical
tissues of the teeth in this quadrant, dressing and N, filling, were affected
Volume 21 Number 5
Table
N, in experimental
edodontic
therapy
641
III. Dog 3
Tooth Upper right molar Upper right premolar Upper right premolar Upper right premolar Upper right oremolar UI;per left molar Upper left premolar Upper left premolar Upper left molar Upper left molar Lower right premolar
Root
first pre-
Days from treatment to death
Presence of periapicul radiolzlcenoy at
Distance
of root Type of filling
death
filling from apex (mm.)
Degree of p&pica1 ~mflammation
300
-
N*
5
Mild
second
M
300
-
N2
9
Mild
second
D
300
-
N,
4
Mild
third
M
300
+
8
Mild
third
D
300
+
4
Mild
240
-
N,
4
Mild
first presecond
M
240
-
N2
0
Mild
second
D
240
-
N2
1
Mild
third pre-
M
240
-
1
Mild
third
D
240
-
N2
6
Mild
second
M
270
+
3.5
Mild
Lower right second premolar Lower right third premolar
D
2io
+
Silver cone and cement UnfiIled
IIf
270
+
2.5
Lower right third premolar Lower right fourth premolar
D
270
-
Silver cone and cement TJnfilled
Rf
270
+
6
Lower right fourth premolar Idower left second premolar
D
270
+
Silver cone and cement Unfilled
M
210
f
3.5
Lower left premolar I,ower left molar
second
n
2 10
+
Silver cone and cement Unfilled
third
nr
210
+
4
I,ower left third premolar I,oww left fourth premolar
1)
310
i-
Silver cone and cement Unfilled
hl
210
+
6
Lower left premolar
D
210
+
Silver cone and CRment Unfilled
fourth
pre-
pre-
Moderate Mild Moderate Moderat,e Severe Mild Moderate Section ruined Severe Rr3wre Severe
than those of any quadrant of the animals in this study. Periapical inflammation was of low intensity. In the distal root of the upper right second premolar, N, was observed to have been extruded through the apical foramen, and yet a minor degree of periapical inflammation was noted. Around the periphery of the extruded N,, cementum-like tissue was deposited (Fig. 1). There was evidence of new bone formation on the pre-existing bone trabeculae. less
Fig. 1. A, Photomicrograph of section through distal I‘OOL of upper right second premolar of Dog 1. N, has been extruded through an apical foramvn. Multiplicity of apical foramina (AP) is common to teeth of dogs. Periodontal ligament iPLJ manifests little inflammation. B, Bone; C, cementurn. (Magnification, x96; rcduc~d IL.) B, Higher magnification of region around cxtrudeil X2. 0mentoid substance (C) has been deposited on periphery of N,. PT,, Periodontal ligament. (,MagniScation, x540; reduced %.,I FIQ. 8. Photomicrograph of section through upper right first premolar of Dog 1 showing periaplcal response to X2 as dressing and filling in root canal. Small amount of granulation t.issue (G) is present in apical foramrn as well as in apical ramification (AR). &IKE;Multiple foramina; I), dentin; C, cemcntum. (Magnification, 254; reduced !/I.)
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N, in experimental
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643
A typical example of a mild inflammatory response in the periapical tissue is shown in Fig. 2, where there is a minimal amount of granulation tissue in the periodontal ligament space and in the main apical foramen. Many of the apical ramifications also contain granulation tissue. Lower right quadrant. The root canals of teeth in this quadrant had received an N, Medical dressing and were filled with N,. In general, the inflammatory lesions observed periapically were of mild to moderate intensity, with the exception of the lesion around the mesial root of the lower fourth premolar. Sections of the periapical regions of these teeth all showed a more marked inflammatory response than was observed around the roots of the maxillary teeth. The inflammatory cell concentration in the granulomatous tissue was denser and the lesions were larger. All of the lesions were similar in certain respects. There wa,s a heavy lacing of calcification throughout the collagen fibers of the granulomatous Gssue, prominent especially in the connective tissue capsule surrounding the granuloma. The walls of many of the capillaries were calcified. Ii’ig. 3 is characteristic of a severe lesion. Bone repair was evident on the periphery of all the lesions. lesions were found Upper left quadrant. Moderate-sized granulomatous around the apices of the roots of all experimental teeth in this quadrant. Similar features were observed in all the periapical lesions. There was calcification of the fibers of the granulomas, and new bone had been elaborated on the periphery of the lesions; evidence of repa,ir could be seen. Fig. 4 shows the typical appearance of a moderate single granulomatous lesion periapically. Compared to reactions observed in the upper right quadrant (N,-filled canals), the periapical inflammation generally was more severe. Thrt most extensive lesion occurred around the distal root of the upper left third premolar (Fig. 5). A large granuloma was present, but on its periphery there were calcified fibers and new bone formation. Considerable osteoblastic activity was evident around the existing bone trabeculae. The roentgenogram revealed only a thickening of the periodontal ligament space. This lack of correlation between the apparent size of a lesion on the roentgenogram and its actual size, histologically, was a consistent finding in this study. Lower left quadrant. DQbridement of the root canals of the teeth of t,his quadrant was similar to that of the root canals of the teeth in the other quadrants. However, in order to determine the effect of debridement alone, root fillings purposely were not inserted. Periapical lesions were present in all cases, but they were not severe. They were of approximately the same magnitude as those around the root canals that were poorly filled with N, (lower right quadrant). Calcification of the connective tissue around the lesions and the blood vessel walls, similar to that observed in the lesions of the other teeth, was seen. The most severe lesion of this qua.drant was observed around the distal root of the lower left fourth premolar. Either an instrument had been broken or amalgam had been forced into this canal, suggesting a possible explanation for the severity of the lesion. Gcncrally, some repair was evident in all the lesions of this animal, regardless of thr technique used. The inflammatory response ranged from very mild (where N, WAS packed into well-dbbridcd canals), to moderate (whcrc the canals cithcr
Fig. 5. Photomicrograph of s&ion through apical region of uppw left third prcrnrh, distal root! of Dog 1. This root, canal was filled with a silver cone. Rxtensivc granuloma (G) is prrscnt, wthin rrhich t,hcre is an area of liquefaction necrosis (7X). C, Cemcntum: .‘IR, api~*:tl r;tmifieation; B, bone. (Magnification, x54; rcduc~d %.)
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N2 in experimedal
e,lclodontic therapy
645
were underfilled with N, or not filled at all), to severe (where silver cones and cement were used to fill the canals). Thorough dkbridement and obturation seemed to be as important as the materials used in determination of the end result. Dog 2 U212~~ right quadrmtt. The root canals of all the experimental teeth t,lrat contained vital, inflamed pulps were instrumented and filled deliberately short of the apex. Although at completion of trea,tment &al pulp tissue had been left in thr canals deliberately, histologic sections of the teeth of both maxillary quadrants revealed necrotic pulps in t,he apical portions of the canals. There was considerable variability in the inflammatory responses around the teeth in this quadrant. The mildest reaction occurred around the distal root of the upper right second premolar (Fig. 6). The lesion was small, although heavily infiltrated with inflamma.torp cells. Illustrative of an extensive lesion in this quadrant was the one surrounding the distal root of the upper right third premo1a.r (Fig. 7). The granuloma extended for a considerable distance around the root on both sides and contained a central area of liquefaction necrosis. On the periphery, there was new bone formation and collagen deposition. Despite the ext,ensireness of this lesion, t,he roentgenogram revealed only an apical thickening.
Fig. 6. Photomicrograph of section through apical region of upper right second premolar, distal root, of Dog 2. This root canal had been filled with silver cones in contact with vital apical pulp tissue. A small periapical granuloma (G) is present. RA, Root apex; PL, periodontal ligament; B, bone. (Magnification, x54; reduced IL.)
646
Snyder,
Seltzer,
and
Moochik
Fig. 7. Composite photomicrograpll of se&on t,hough apical region of upper right thirtl p1 l>IUOhr, distal root, of Dog 2. This canal was filled was a. silver cone. Sole vx-lr nsiw gr. %nuloIna (G) containing arca of liquefaction nwrosis (1,X). AR, Apical rwnifica tion : x54; reduced I/.! R, resorption of cementurn (C); Ii, hone. (2Iagnification,
Upper left quadrant. Thv cwltnrc from Ihe canal of the upper left first w~~olar was negative; all other canal cultures were positive. Howtvr, t here PI Wi YS no apparent relationship between the absence or presence of infection and th c severity of the inflammatory responw. Granulomas ranging from small to moderate in size ww-e noted. There u a.round the upper Sill(la11 granuloma Icft first premolar; within ii, tht>rcL
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N, in experimental
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liquefaction necrosis. The inflammatory cell density was small. Osteoblastic activity and new bone formation were evident around the lesion. Around the canals of the upper left third premolar, which yielded positive cultures, the lesions were similar to each other in character. A moderate-sized lesion was seen around the distal root. Although larger than the lesion around the first premolar, the inflammatory cell density was small in both, and there was evidence of new bone formation around the periphery. Some epithelial proliferation was evident. The lesion extended in a coronal direction about one third the length of the roots. The upper left second premolar was treated similarly to the other teeth of t,his quadrant, except that the root canal filling was omitted inadvertently. An area of rarefaction was present around both roots. Some root resorption was evident, but the inflammatory cell density was small. The lesions were smaller than those around the filled roots of the upper left third premolar. Lower right quadrant. The fate of the remaining inflamed vital pulp tissue when in contact with N, was studied in the teeth of this quadrant. In no instance was any vitality maintained; nor was a “sclerotic” zone evident at the place of pulp amputation. Periapical lesions varied from mild to moderate in severity. A typical lesion of this quadrant was the one around the distal root of the lower right third premolar. The remaining pulp tissue had become necrotic. In thr root canal, N, was dispersed throughout the necrotic pulp tissue. A moderatesized granuloma was present periapically. Chronic inflammatory cells were present in all the apical foramina. There were areas of liquefaction necrosis within some lesions in this quadrant. Lower left quadrant. The extent of the lesions in this quadrant varied greatl,v. There was a minute amount of granulation tissue at the apex of the distal root of the lower left second premolar. A more extensive lesion was observed around the mesial root of the lower left second premolar. Some of the other lesions observed were the largest of any seen in this animal. In the largest lesion around the mcsial root of the lower left third premolar (Fig. 8)) resorptions of the root had occurred on both the mesial and the distal aspects. The lesion did not extend periapically into the bone, as the other granulomatous lesions did; instead, the granulomatous tissue extended for a considerable distance around the sides of the root, extending almost halfway up the root in a coronal direction. There was considerable bone resorption on the periphery of the lesion. Liquefaction necrosis was evident around t,he sides of the roots. Small granulations were observed in the bone and periodontal ligament crownward to the main lesion. There was abundant collagen and/or osteoid deposition ?n the periphery of all the lesions, regardless of their extensiveness. Radiographically, the lesions on the mcsial root of the lower left third premolar, the most extensive in this quadrant, appeared smaller than that of the distal root of the lower left third premolar (Fig. 12, B). Histologically, the latter lesion was much less extensive, emphasizing that the size of a roentgenographic area of rarefaction neither coincides with nor is diagnostically indicative of the actual histologic extent of the lesion. In general, it was observed that wherever inflamed pulp tissue ~7rasleft in
648
Snyder, Seltze,r, curd Moodnik
0.8.. O.M. $0.1’. Mav*> 1966
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N, in experinre&d
edodontic
therapy
649
the root canal greater periapical inflammatory lesions resulted. This occurred regardless of whether N, or silver cones with cement were used for partial ohturation of the root canal. Dog 3 Upper right quadrant. Following extirpation of uninflamed pulps, N,-treated canals were compared with those treated by conventional methods. Another observation was also made; within the sa.me t,ooth, the prriapical reactions around a filled root canal were compared with those around an unfilled canal. Thus, previous pathologic involvements of the pulp and periapical tissues, being a,bsent, could have no influence on the findings. All lesions observed in this quadrant were small and mild in inflammatory cell density. The distal root of the upper right second premolar and the me&al root of the third premolar had histologically similar lesions. They were typical of the lesions in this quadrant. A slightly denser magnitude of inflammatory cells was present around the distal root of the upper right second premolar than around the mesial root of the upper right third premolar. In the former, there was more N, in contact with the remaining pulp. In all cases, the pulps adjacent to the N, were necrotic and chronic inflammation resulted periapically. Upper Zeft qua&ad. There were lesions around all the teeth, but. thry were generally smaller than those in the quadra.nts where silver cones were used to obturate the canals. Proliferated epithelium was found in all the lesions; microcysts had formed in most of them. The lesion around the distal root of the upper left third premolar was typical of those present in the entire quadrant (Fig. 9). The granuloma was small, and sheets of epithclium wrre present. A small lumen was developing in a region of degenerating epithelial cells, forming a microcyst. Lower right quadrant. The same type of lesion was found around all of the root apices in this quadrant, differing only in size. In general, fairly large cysts or granulomas containing epithelium were found around the apices of both filled and unfilled canals. Typical of the lesions in this quadrant were the ones around the distal root of the lower right third premolar and the mesial root. of the lower right fourt.h premolar. Proliferated epithelium extended from one side of the root to the other, Lumina were observed, around which degenerating epithelial cells were evident (Fig. 10). NW bone formation was also found on the periphery of all the lesions. Lower left quadrant. The lesions around the teeth in this quadrant were similar to those observed on the lower right side. Large periapical lesions containing epithelium, with evidence of new bone format,ion on the periphery, were found in every case. Around the unfilled canals, the lesions were larger. Typical of the lesions of this quadra.nt was the one around the distal root of the lo~+r left third premolar (Fig. 11). This lesion was the largest in size, and it was present around a root with an unfilled canal. Proliferated cpithelium with three distinct lumina was observed. New bone formation was seen on the periphery of the lesion. In general, where N, was used, the least inflammation was noted around the canals that were more thoroughly obturated. In the lower quadrants, where
Pig. 9
Fig. 9. Section through apical region of upper left third prenmlar, distal root, of Dog 3. Nz ~vas used to fill root canal, in contact, with previously uninflamed pulp tissue. Multiple foramina (MP) opening through dentin In) all contain necrotic pulp tissue (X). Surround ing root apex (RA) is proliferating cpithelium (IC) which has degenerated in seme regions, forming a microcyst (XC). C, Cemcntum; H, bone. (Magnification, x54 ; retlm~c~~lIL.) Pig. 10. Photomicrograph of srction of apical lesion from mesial root of lolver right fourth premolar of Dog 3. Granuloma contains degenerating epithclial cells (E-DE), polymorphonuclear leukocytes (I’), and dilated blood vessels (BP). (Magnification, x%0; rrduced r/cl.)
silver cones were used, thcrc were similar findings; the more complete the obturation, the less the periapical inflammation. On the other hand, tissue reactions around the roots with unfilled canals were the most severe. All of the re maining pulp tissue was invaria.bly necrotic, regardless of whether silver cones or N, had been used for canal fillings. DISCUSSION In the entire study, the least amount of periapical destruction was observed around the teeth whose root canals had been treated with N, Medical and filled with N,; there was slightly more periapical destruction around the canals that were obturated with silver cones and root canal cement. These results are in contradiction to those reported by Kuroiwa.3 Since the canals of some teeth were treated with N, Medical, and some with camphorated paramonochlorophenol, it is possible that N, Medical is a more effective germicide than camphorated paramonochlorophenol. Rappaport and associates”found this to be so in their study. However, the antibacterial effectiveness of N, may vary as the formula varies. When the formula was presented to the Council on Dental Therapeutics of the American Dental Association in 1963, the paraformaldehyde content was given as 4.7 per cent. Successive analyses,
Volume 21 Number 5
N, in experimehd
edodontic
therapy
651
Pig. 11. Photomicrograph of section through apical region of lower left third premolar, distal root, of Dog 3. Extensive granuloma (G) is present around root apex (RA). Lesion extends along both sides of root. Dentin (D) and cementum (6’) have been resorbed (R). Three lumina (L) have formed in proliferating epithelium (EP), indicating that a cyst has developed. B, Bone. (Magnification, x54; reduced $4.)
by public analysts, showed variations in the paraformaldehyde content from 0.22 to 6.0 per cent.17 Obviously, the bactericidal effect would be influenced by the content of formaldehyde. The remaining constituents of the formula also \-aried widely. For example, in all the samples studied privately, lead oxide was a major ingredient, varying from 19.5 to 26.9 per cent. Yet, lead oxide is not mentioned at all as an ingredient on the package circular or in the formula given to the American Dental Association.l’ One of the indictments against N, as a root filling agent is that it is impossible (or, at best, difficult) to control precisely, its placement in the canal. An attempt to pack N, tightly into a canal will likely result in overfilling. The
652
Snyder, Seltzer, aid .lfoodwil:
Fig. Id. A, Bt and C, Roerhgenograms of four quadrants of Dogs 1, 8, n11dB after ilt%tli. 1, Upper right quadrant; 8, upper left quadrant; 3, lower left quadrant; 4, lamer right quadrant.
effects of overfilling with N, were studied in one case. N, was well tolerated and walled off with a cementum-like tissue when it was inadvertently forced beyond the apex. Although the lesions in all of the animals varied widely, N, appeared t.o stimulate the deposition of collagen and/or osteoid in large amounts. This deposition was observed at a distance from the destruction that resulted when N, contacted pulp tissue. These findings contradict many reports which claimed that N, is severely irritating to the periapical tissues. They would seem to support Sa,rgenti and Richter’s claim that N, may enhance hard tissue apposition. Calcification of the collagen fibers and blood vessel walls of the lesions in the first dog was observed. However, t.his calcification was not due to the action of the N,, since such calcification was present in all the lesions, including those around root canals which were dressed with camphorat,ed pa.ramonoc,hlorophenol but unfilled. Whether this calcification was a result of the deposition of calcium in tissue which was injured, degenerating, or necrotic is unknown. Where inflamed pulp tissue was deliberately left in the canal, the pattern of inflammatory response was erratic, varying from mild to severe. Why there should be such a variance in reaction in the same quadrant of the same animal is not known. The cultures of these teeth were all positive, tending to cancel out the presence of bacteria as a factor. Furthermore, in two dogs results were similar, regardless of culture findings. One difference between the reactions around some teeth was the proliferation of epithelium. That such proliferation was not caused by microorganisms was borne out in the lesions of the third a.nimal. In these teeth there was no ba.cterial contamination ; yet there was frequent evidence of epithelial proliferation. This cpithelial proliferation was noted in almost all of t.hc lesions, regardless of the management of the canals. The range of reaction varied from sheets of epit,helium dispersed through the fibrous tissue of the granuloma to large, frank cysts with more than one lumen. Around all of these cystic lesions, there was new bone deposition and repair. Similar findings of periapical cyst formation in dogs, unrelated to the presence or absence of microorganisms, were noted by Seltzer and colleagues.18 Our studies show that there was no evidence of any vitality; nor was a “sclerotic zone” (Sargenti and Richter) observed at t,he region of pnlp amputation. However, there a.ppeared to be a correlation between the degree of repair and the distance of the N, from the apex, confirming the findings of Iten and of Nieholls.12 It would appear, therefore, that the inflammatory response may vary, depending on the level of pulp amputation and the amount of N, in the canal. However, our findings differ in other respects from those of Iten and Nicholls. Although they found some vital pulp tissue in the apical area, we found only necrotic tissue. Iten found fixation of the pulp closest to the N,; we found total architectural destruction. There appears to be a direct correlation between maximal debridement and obturation and apical healing. Since there was some attempt at repair in every yuadrant of Dog 1, it, is our
R~‘~ittYllWS 01’ lll(l ittv;tt~i;rI~ly
twlttii~Itt~~
tl~~~~~tl~~l~ilt~~~tl iltl(l
c~ttll)l0J’cVl, c~tYYltcY1
ittflittrtc~tl
[Wt’iitI)i(*;tI
j)ttl~~
itlflilI~ltllilti~~tl.
lisslrct l
iti
1 llv
(‘iltl;ll
;I11 f)ltysiib
tltc t1q.p~~ or ittjitry itiflucwcw 111~ittflatrttnator~~ twpottw. ‘I’ltc~t~~ appcarcd to b(b il. dirM rcli~tiol~ship h:twcv:n tllcl c~llillltity Of tllcl irt*it;rnt,, inflamed pulp tissue, and the subsequent response, an arca of rarefaction. N, apparently did not cure inflamed palp tissue, as claimed by Sargenti and Richter. tissue became necrotic following partial pulp X~en previously uninflamed pulp extirpation, and chronic periapical in8ammation resulted. Hower~, the lesions were smdler and had less inflammatory ccl1 density in the Y,-filled canals than those of the roots filled with silver cones. The ralidity of the concept of par&l pulp removal, particularly where inflamed pulp tissue is present, is open to question. In cases of pulpitis, where is the optirnum plane of pulp scvcraiic( ‘“z Should the wound be made in the apical third, close to the apical foramen, in the pulp tissue tl1a.t is less cellular and more fibrotic? Or is it better to amputate the pulp in the middle t,hird of the root canal and leave a more cellular pulp tissue 3 This question cannot 1)~ I’Csolved definitely, since it is dificult, if not impossible, to detcrrnine at, what level the inflammator,v process can be reversed. Also, it is doubtful, from a technical standpoint, that a pulp can be amputated at a specific level. It is oul impression that when canals arc treated with camphorated paramonoclllorophenol or NZ, repair is encouraged when no pulp tissue is left in the main c>anal and t,he canal is obturated as thoroughly as possible. logic+ I’nnctiotts,
SUMMARY
In an effort to simula.tc clinical conditions in human teeth, dental p~Jps in dogs were injured and exposed to the oral fluids for varying periods of time to prodncc inflamed and/or necrotic pulps. In one of the dogs, the pulps were not, injured prior to the experimental procedures. Root canal treatment procednrcs employing N, Medical and N, and n more sta.ndardized treatment using silret cones and root ca.nal cement wrrc performed on three dogs. In addition, some canals were instrumented hut not fillrd. Because bot!h the technique and the effects of the drugs were to 1~ compared, the standard technique was modified so that the completeness of root fillings could bc comparable to that, of the N, tc~chniqnc. The animals WW(L killed 6 to 1 llh months aft,er t,hc c)p(Lr;ltivc pt’oc~cdr~rcs. Compilrativc ltistoloaic stutlics of the pcJl*iapical tissue 1’6~itctiOrls \vt’t’(’ 1 1lPll
Klilil(~.
CONCLUSIONS Specific
1. In the teeth of dogs, thorough debridemcnt and obturation of the root canal seemed to be more important for repair of the periapical tissues than t,he material used as a root canal dressing or as a filling agent. 2. The periapical tissues of the teeth treated with N, were less inflamed than the tissues of the teeth fillctl with silrrr cones. These results wcrc obssrrrrcl in
Volume 21 Number 5
N, in experimedal
edodontic
therapy
655
teeth in which the mechanical instrumentation and the root. canal fillings wcr(’ performed as thoroughly as possible. 3. N, was a less irritating root canal ccmcnt than a silver-containing root canal cement (modified zinc-oxide-eugenol). Where N, was forced beyond the apex, it was well tolerated by the periapical tissues. 4. Ir;, as a filling agent is difficult to manipulate precisely. 5. The apical pulp tissue in contact with N, became necrotic in every cask. 6. N, is not a panacea. It is not a substitute for complete ddbridement, enlargemcnt, and filling of root canals. General
1. Thorc was IIO correlation bctwcen the apparent size of a lesion, rocntgenographically, and the actual extent of the lesion, histologically. The absence of :I roentgenolucent area on the roentgenogram did not preclude the prcsencc ol’ a pa.thologic area histologically. 2. There did not appear to bc a reliable pattern of healing following endodontic therapy. R’esults varied widely in the same animal, in the same quadrant,, and under the same conditions. 3. In some instances, endodontic procedures induced the proliferation of epithclial rests and subsequent cyst formation. 4. Fibrous encapsulation and peripheral osteogenic a&ivit,y occurred in cvcry case of cyst formation. 5. It should be apparent t,hat this st,udy does not answer all of the questions concerning healing in relakion to X2. It does bring into sha,rp focus the unpredictability of periapical repair in dogs’ teeth, regal *dlcss of thr technique cmployed. REFERENCES
of Teeth With Diseased 1. Rose, C.: Treatment A., and Richter, S. L.: Rationalized 2. Sargenti,
1961, AGSA Scientific Publications. K. : Experimental Study on Root Canal Filling Using Sew Filling Material N? and AN,, Bull. Oral Path. 4: 45, 1960. Council on Dental Therapeutics : Hazards of Formaldehyde Preparations for Single Treatment Procedures in Endodontics-N, and the R-Method, J. Am. Dent. A. 64: 689, 1962. Bertolini, A. G.: Recherches bacteriologiques sur le X3, substance pour l’obturation radiculaire, Schweiz. Monatschr. Zahnh. 68: 221, 1958. Rappaport, H. M., Lilly, G. E., and Kapsimalis, P.: Toxicity of Endodontic Filling Materials, ORAL SURG., ORAL MED. & ORAL PATH. 18: 785, 1964. Overdiek, H. F. : Zur Gewebsreaktion auf implantierte Wurzelfullmaterialien im Vergleich zum N?, Zahnarztl. Rundschau 11: 402, 1960. Guttuso, J. : Histopathologic Study of Rat Connective Tissue Responses to Endodontic Materials, ORAL SURG., ORAL MED. & ORAL PATH. 16: 713, 1963. Zerosi,, C., Barat,ieri, A., and Amici, G.: Osservazioni istologiche sul comportamento dei tessutl periapicali dopo otturzione canalare con cement0 K,, Rx%. t,rimrst. odont. 15: 555, 1959. 1ten, J. : Klinische untl Histologische TTntoruucllungell mit, 11t.r \Vur~.c,lfu~.llrrl;ll csricnl Sz, Inaugural dissertation, Arand Druek, Bern, Basil, 1958. Overdiek, II. I?. : Pulpenreaktion auf NI im .Jurz~~!it-\‘er~uc,ll, 1hwtsvllr%:~l~tr. %t,scllr. 10: 7X6, 1960. Nicholls, E. : A Study of N-2 ,in <:rossnlall, L. I. (editor): Trttnsactions of t,llt: ThiI~cl Internat. Conference on Endodontics, Philadelphia, 1963, University of Pennsylvania, 1,. 52. Rowe, A. H.: A Histologic Study of the Healing of Pulp Remnants Under N-2 Root Canal Scaler, Brit. D. J. 117: 27, 1964.
<3 . Kuroiwa, 4. 0. 6. 7. 8. 9.
10. 11. 12. 13.
Pulps, Dental Cosmos 36: 358, 1894. Root Canal Treatment, ed. 3, Yew York,
cm 2000 l’ceth Filled \Vith N-2 During it I’vrio
ORAL MED. & ORAL PATH. 17: 507. 1961.
Association
of Endodontists
I. B. Btwder, Editor
Effects of NZ in experimental endodontic therapy David E. Snyder, D.D.X., Samuel Xeltzer, D.D.8., and l&hard illoodnik, D.D.X., Philadelphia, Pa. UNIVERSITY
OF PENNSYLVANIA
SCHOOL
OF DENTAT,
MEDICINE
R
oot canal filling material in the form of a paste (iodoform paste) was introduced in the practice of endodontics by Rose1 in 1894. Since then, the use of various kinds of absorbable and nonabsorbable pastes for the filling of root canals has been reported. Some pastes have enjoyed popularity for short periods of time but, in our opinion, none have had the impact or the popularity of the nonabsorbable paste known as N,, which was introduced by Sargenti and Richter.2 The term N, describes both the drug and the technique. In their book, Rationalized Root Canal Treatment, Sargenti and Richter2 have presented their view of pulp and periapical diseases and their method of treating them. The appeal in their approach is twofold : (1) The mechanical aspect of endodontic therapy is less demanding than conventional methods, with a consequent reduction in treatment time, and (2) the outcome of endodontic therapy becomes totally predictable. REVIEW
OF THE LITERATURE
Many reports relative to the efficacy of N, as a root canal treatment and filling agent are contradictory. Investigations of N, have been made on animals by Kuroiwa,3 Overdiek,7 Zerosi and colleagues,” Guttuso,s Rappaport and associates,G and the Council on Dental Therapeutics.4 Kuroiwa and Zerosi and co-workers were in general agreement that N, Medical and N, produced good results in root canal treatment. However, Kuroiwa limited his agreement only to uninfected teeth, stating that the material was not effective in the treatment of infected root canals. Guttuso, from
This investigation was supported by United States Public Health Service Grant DE 01930 the National Institute of Dental Research, National Institutes of Health, Betheda, Md.
635
636
Snyder, Seltzer, clml .VoodniX:
O.S.,O.M.8 0.1’. May,
1%x
Rappaport and associates, and the Council on I)entaI Tht~raprtuti~s agr~d that subcutaneous implant,s of N2 elicted a more se~‘erc inflammatory rc~sponsc~than other commonly used root canal mcdicaments and filling agents. On the othw hand, Overdiek found that N, was well tolerated by the periapical tissues and was walled off by a connective tissue ca.psule. Kuroiwa was unable to demonstrate such a connective tissue capsule around h’?. Both histologic and clinical inrest,igations on human teeth were c*onducted by Iten,‘” Overdiek,ll rC’icholls,” Kowc,~” Bermann and Ebersberg,” and Tschamer.‘” On the basis of histologic examination, t.here was no agreement as to the state of the remaining pulp &sue under an N2 filling. The reports raried; pulps were found to be necrotic, fixed, or caompletcly vital. Clinically, Nicholls, Rowe, and Bermann and Ebersberg all found fairly consistent pcriapical healing with the use of N2 filling material. Tschamer, howclver, reported a 71 per rclnt failure rate when N2 was used as a filling material. Bacteriologically, Rappaport, and colleagues” and Bertolini” found that N, was an effective antibacterial agent, against a wide range of microorganisms commonly found in infected root. canals. These findings are in direct contradiction to the report of the Council on Dental Therapeutics.4 Confronted on the one hand by the rat,hcr widespread interrst in the Tu’, method and its promise of total prrdi&ahility, a goal for which endodontists have been striving, and on the other hand by such vastly contradictory findings, we decided that another study was justified. An>- endodontic technique which promises that a granuloma (2;1nnot form after treatment, as Sargenti and Richter Thus, wc devised a study in ‘which hare claimed, invites an inrcstigation. comparisons could be made between the efficacy of the N2 method and t>hat of >I standard t,echnique simi1a.r to one used by most A4merican endodontists. METHODS
AND
MATERIALS
Three male collie dogs, of which two w’ere approximately 3 years old and the third about 5 years old, WWF used in this study. The animals were ancsthetized with intravenous Nembntal sodium at each operative session. Dog
1
The purpose of this experiment was to compare the results of root canal treatment with N, Medical dressing and N, filling wit.h the results of treatment with paramonochlorophenol dressing and silver cone filling in teeth with infected root canals and periapical areas of rarefaction. The maxillary and mandibular premolars were reduced from the occlusal surfa,ce to a plane below the functional occlusal lercl. The teeth were then opened through the occlusal surface with high-speed dry carbide burs until the pulps were exposed. The pulps were extirpated with reamers and files, and t,he teeth mere left open to t,he salivary fluids for approximately YI rnonths in order to induce periapical lesions. Roentgenograms were taken to determine the presence of periapical areas of radiolecency. During subsequent. treatments, each tooth was isolated under rubber dam and t,he field was wiped with tincture of Metaphen.
N2 in experime&l
Volume PI Number 5
endodontic therapy
637
The lnasillary and lnandibular right I)rernolars WCI-c rcamcd and filed with Sargenti’s root canal instruments, aceorhg to his inskuctions for the twatrntnt, of pnlpless teeth. The ranals w(‘r~3 twn.t,4 with N, i\lrdical, as a root r;lEl.l
dressing, and scaled temporarily with zinc osidc-cugc>nol. T\VO weeks latpr th(: canals were reinstrumcntcd and filled with N, according to the st,atcd instructions. The root canals of the maxillary teeth were filled close to the apical foramen, as determined radiographically, and amalgam restorat,ions were placed in the coronal cavities. The root canals of the mandibular t.eeth, although as well-dkbrided as those of the upper teeth, were filled considerably short of the apex, as determined radiographically. The maxillary and mandibu1a.r left premolars mere instrumented with standard reamers and files and irrigated with normal saline solution, after xvhich root ca.nal dressings of paramonochlorophenol were placed. Zinc oxidceugenol temporary fillings were inserted. Two weeks later the maxillary premolar car& were filled with silver cones and a silver-containing root canal cement.* The mandibu1a.r premolar canals were not filled. All of the treated t,ecth were sealed occlusally with ama,lgam restorations. The dog was killed 6 months later. Table 1 summarizes the significant data relating to trentmcnt, of the teeth of Dog 1. Dog
2
The purpose of the experiment on this animal was to compare the efficacy of the one-vist N, treatment with that of one-visit standard treatment in cases of chronic pulpitis. The pulps were exposed in all of the experimental teeth and these teet,h were left open to the salivary fluids for several weeks in order to induce a chronic pulpitis. The teeth were then isolated under a rubber dam a.nd the field was cleansed with tincture of Metaphen. The root canals of the mandibular left premolars were instrumented short of the apex and prefilling cultures were taken. The canals were flushed with normal saline solution, dried, and immediately filled wit,h N,. The culture results from these teeth were all positive. The root canals of the maxillary left premolars were similarly treated but were filled with silver cones and root canal cement. The maxillary second premolar was accidentally deleted from this study. The culture results were negative for the maxillary first premolar and positive for the maxillary third premolar. Ten weeks after pulp exposure, the root canals of the maxillary right prcmolars were instrumented short of the apex. Prefilling cultures were t,akcn. ‘Courtesy of S. Tancredi Pharmacy, Pl-‘hiladelplria, Pa. Powder
Silver, precipitated Stabelite resin Zinc oxide, chemically pure Magnesium oxide Fhgenol liquitl
30.0 .I5.0 “0.0 1.5
1
M
D
M D M D M
Upper left third premolar
Upper left third premolar
Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower Lower
hi = Medial. D = Distal. PMCP = Paramonochlorophenol. - = Absent. + = Present.
right second premolar right second premolar right third premolar right third premolar right fourth premolar right fourth premolar left second premolar left second premolar left third premolar left third premolar left fourth premolar left fourth premolar
D
Upper left second premolar
,” D
M
Root
M
right first premolar right second premolar right second premolar right third premolar right third premolar left first premolar
Tooth
1. Dog
Upper left second premolar
Upper Upper Upper Upper Upper Upper
Table
Medical Medical Medical Medical Medical Medical PMCP PMCP PMCP PMCP PMCP PMCP
PMCP
PMCP
PMCP
PMCP
Medical Medical Medical Medical Medical PMCP
Interim dressing
180 180 180 180 180 180 180 180 180 180 180 180
180
180
180
180
210 210 210 210 210 180
Dwrattin of experiment (days)
Present Present Present Present Present Increase Increase Increase Increase Increase Same Increase Increase
f + + + + c + f
Increase
Increase
Increase
-
Change in status of periapical radiolucmoy after treatment
-
Presence of radiolucency following pulp removal
Silver and Silver and Silver and Silver and Silver and h-2 N? II-, x* II-2 N* Unfilled Unfilled Unfilled Unfilled Unfilled Unfilled
s; cone cement cone cement cone cement cone cement cone cement
filling
Type of root canal
7
6 4.5 6 3
2.5
1.5
3
Distance of canal filling from apex (mm.)
Mild Mild Moderate Mild Severe Moderate Mild Mild Mild Mild Milt1 Screw
Moderate
Mild
Moderate
Moderat,e
Mild Mild Mild Mild Mild Moderate
Degree of pe”riupical inflammation
2i0
270
270
Upper right second premolar
Upper right third premolar
Upper right third
330
180
180
D
11
D
11
D
M
Upper left third premolar
Lower right second premolar
Lower right second premolar
Lower right third premolar
Lower right third premolar
premolar
premolar
Lower right fourth
Lower right fourth
180
180
180
D
M
D
M
1)
Lower left second premolar
Lower left third premolar
Lower left third premolar
premolar
premolar
Lower left fourth
Lower left fourth
180
180
180
M
180
180
180
Lower left second premolar
D
330
Upper left third premolar
180
330
Upper left first premolar
premolar
270
to death
treatment
from
Upper right second premolar
Root
Days
330
Tooth
II. Dog 2
Upper right first premolar
Table
+ + + + + + + + + +
+ + + + + + + + + + + +
+
+
+
+
+
+
-
Culture 1-r~sults
-
Presence of apical radiolucency at time of death
Presence of apical radiolucency at time of treatment
Mild
s2
A?
s,
Srvrre
Moderate
Severe
Severe
Noderate x2 s,
Moderate
s, x\‘:!
Mild
Moderate
Mild
JIild
Moderate
Mild
Mild
Severe
Mild
Mild
Mild
Xoderate
Moderate
8 8
6
1
4
2
3
4
4
s,
cone cement cone cement cone cement cone cement cone cement cone cement cone cement cone cement
s,
SC
x2
Silver and Silver and Silver and Silver and Silver and Silver and Silver and Silver and s,
Type of fillin,/
The canals were then flushed nith norm;~l salillr s(jIrItiol-1 ;d drjd, aftc,r wtiicli silver cones were cemented into the canals with root canal W~~WI ‘I’hr cllltur~ results from these teeth were all positive. Twelve weeks after p~ilp cxposurc, the root (*anals of all the manditmlai premolars were instrumented short of the apex. Prcfilling cultures were taken, the canals were flushed with normal saline solution, dried, and then filled wit,h S!. Culture results from these teeth were all positive. The coronal cavities in all 01 the treated teeth were filled with amalgam. Table II summarizes trea.tment procedures and findings in the t,ecth of I jog Y!. Dog
3
The purpose of this experiment was t.o compare the state of the remaining apical pulp tissue in teeth with uninflamed pulps which had undergone standard endodontic treatment and root filling with that of the remaining pulp tissues after N, treatment. As a further control, t,he remaining pulp timue following partial pulp extirpation in unfilled canals was compared with the remaining pulp tissue in teeth with filled root canals. All of the premolars treated in this animal, as well as in the other two dogs, were free of caries and detecta,ble periodontal involvement. The teeth were isolated under the rubber dam, and the field was cleansed and wiped with tincture of Metaphen. The pulps tha,t were extirpated were all intact, and presumably uninflamed. The maxillary right and left prernolars were opened through the occlusal surface with high-speed burs and adequate coolant. The pulps were removed deliberately short of the apex. The canals were instrumented short of the apex, flushed with normal saline solution, dried, and filled with N,, also short of t,he apex. The pulps of the mandibular premolars were removed deliberately short of the apex and instrumentation was completed short of the apex. The canals were irrigated with normal saline solution and the mesial canals were filled with silver cones and root canal cement, short of the apex. The distal canals wern left unfilled. The coronal cavities in all the experimental teeth were filled with amalgam. Table III presents a summary of treatment procedures and findings in the teeth of Dog 3. Preoperative, treatment, and postoperative roentgenograms were taken of the teeth of all the animals. Roentgenograms of all the animals at the time of death are shown in Fig. 12, A, B, and C. The animals were killed by perfusion with fixatives between 6 and 11 months following the treatment procedures. Jaw blocks containing the treated teeth were then decalcified, embedded, and sectioned. Sections were cut at 6 microns and stained with hematoxylin and eosin. Serial sections were then examined microscopically. FINDINGS Dog 1
Upper right quadrant. The periapical which had been treated with N, Medical
tissues of the teeth in this quadrant, dressing and N, filling, were affected
Volume 21 Number 5
Table
N, in experimental
edodontic
therapy
641
III. Dog 3
Tooth Upper right molar Upper right premolar Upper right premolar Upper right premolar Upper right oremolar UI;per left molar Upper left premolar Upper left premolar Upper left molar Upper left molar Lower right premolar
Root
first pre-
Days from treatment to death
Presence of periapicul radiolzlcenoy at
Distance
of root Type of filling
death
filling from apex (mm.)
Degree of p&pica1 ~mflammation
300
-
N*
5
Mild
second
M
300
-
N2
9
Mild
second
D
300
-
N,
4
Mild
third
M
300
+
8
Mild
third
D
300
+
4
Mild
240
-
N,
4
Mild
first presecond
M
240
-
N2
0
Mild
second
D
240
-
N2
1
Mild
third pre-
M
240
-
1
Mild
third
D
240
-
N2
6
Mild
second
M
270
+
3.5
Mild
Lower right second premolar Lower right third premolar
D
2io
+
Silver cone and cement UnfiIled
IIf
270
+
2.5
Lower right third premolar Lower right fourth premolar
D
270
-
Silver cone and cement TJnfilled
Rf
270
+
6
Lower right fourth premolar Idower left second premolar
D
270
+
Silver cone and cement Unfilled
M
210
f
3.5
Lower left premolar I,ower left molar
second
n
2 10
+
Silver cone and cement Unfilled
third
nr
210
+
4
I,ower left third premolar I,oww left fourth premolar
1)
310
i-
Silver cone and cement Unfilled
hl
210
+
6
Lower left premolar
D
210
+
Silver cone and CRment Unfilled
fourth
pre-
pre-
Moderate Mild Moderate Moderat,e Severe Mild Moderate Section ruined Severe Rr3wre Severe
than those of any quadrant of the animals in this study. Periapical inflammation was of low intensity. In the distal root of the upper right second premolar, N, was observed to have been extruded through the apical foramen, and yet a minor degree of periapical inflammation was noted. Around the periphery of the extruded N,, cementum-like tissue was deposited (Fig. 1). There was evidence of new bone formation on the pre-existing bone trabeculae. less
Fig. 1. A, Photomicrograph of section through distal I‘OOL of upper right second premolar of Dog 1. N, has been extruded through an apical foramvn. Multiplicity of apical foramina (AP) is common to teeth of dogs. Periodontal ligament iPLJ manifests little inflammation. B, Bone; C, cementurn. (Magnification, x96; rcduc~d IL.) B, Higher magnification of region around cxtrudeil X2. 0mentoid substance (C) has been deposited on periphery of N,. PT,, Periodontal ligament. (,MagniScation, x540; reduced %.,I FIQ. 8. Photomicrograph of section through upper right first premolar of Dog 1 showing periaplcal response to X2 as dressing and filling in root canal. Small amount of granulation t.issue (G) is present in apical foramrn as well as in apical ramification (AR). &IKE;Multiple foramina; I), dentin; C, cemcntum. (Magnification, 254; reduced !/I.)
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A typical example of a mild inflammatory response in the periapical tissue is shown in Fig. 2, where there is a minimal amount of granulation tissue in the periodontal ligament space and in the main apical foramen. Many of the apical ramifications also contain granulation tissue. Lower right quadrant. The root canals of teeth in this quadrant had received an N, Medical dressing and were filled with N,. In general, the inflammatory lesions observed periapically were of mild to moderate intensity, with the exception of the lesion around the mesial root of the lower fourth premolar. Sections of the periapical regions of these teeth all showed a more marked inflammatory response than was observed around the roots of the maxillary teeth. The inflammatory cell concentration in the granulomatous tissue was denser and the lesions were larger. All of the lesions were similar in certain respects. There wa,s a heavy lacing of calcification throughout the collagen fibers of the granulomatous Gssue, prominent especially in the connective tissue capsule surrounding the granuloma. The walls of many of the capillaries were calcified. Ii’ig. 3 is characteristic of a severe lesion. Bone repair was evident on the periphery of all the lesions. lesions were found Upper left quadrant. Moderate-sized granulomatous around the apices of the roots of all experimental teeth in this quadrant. Similar features were observed in all the periapical lesions. There was calcification of the fibers of the granulomas, and new bone had been elaborated on the periphery of the lesions; evidence of repa,ir could be seen. Fig. 4 shows the typical appearance of a moderate single granulomatous lesion periapically. Compared to reactions observed in the upper right quadrant (N,-filled canals), the periapical inflammation generally was more severe. Thrt most extensive lesion occurred around the distal root of the upper left third premolar (Fig. 5). A large granuloma was present, but on its periphery there were calcified fibers and new bone formation. Considerable osteoblastic activity was evident around the existing bone trabeculae. The roentgenogram revealed only a thickening of the periodontal ligament space. This lack of correlation between the apparent size of a lesion on the roentgenogram and its actual size, histologically, was a consistent finding in this study. Lower left quadrant. DQbridement of the root canals of the teeth of t,his quadrant was similar to that of the root canals of the teeth in the other quadrants. However, in order to determine the effect of debridement alone, root fillings purposely were not inserted. Periapical lesions were present in all cases, but they were not severe. They were of approximately the same magnitude as those around the root canals that were poorly filled with N, (lower right quadrant). Calcification of the connective tissue around the lesions and the blood vessel walls, similar to that observed in the lesions of the other teeth, was seen. The most severe lesion of this qua.drant was observed around the distal root of the lower left fourth premolar. Either an instrument had been broken or amalgam had been forced into this canal, suggesting a possible explanation for the severity of the lesion. Gcncrally, some repair was evident in all the lesions of this animal, regardless of thr technique used. The inflammatory response ranged from very mild (where N, WAS packed into well-dbbridcd canals), to moderate (whcrc the canals cithcr
Fig. 5. Photomicrograph of s&ion through apical region of uppw left third prcrnrh, distal root! of Dog 1. This root, canal was filled with a silver cone. Rxtensivc granuloma (G) is prrscnt, wthin rrhich t,hcre is an area of liquefaction necrosis (7X). C, Cemcntum: .‘IR, api~*:tl r;tmifieation; B, bone. (Magnification, x54; rcduc~d %.)
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were underfilled with N, or not filled at all), to severe (where silver cones and cement were used to fill the canals). Thorough dkbridement and obturation seemed to be as important as the materials used in determination of the end result. Dog 2 U212~~ right quadrmtt. The root canals of all the experimental teeth t,lrat contained vital, inflamed pulps were instrumented and filled deliberately short of the apex. Although at completion of trea,tment &al pulp tissue had been left in thr canals deliberately, histologic sections of the teeth of both maxillary quadrants revealed necrotic pulps in t,he apical portions of the canals. There was considerable variability in the inflammatory responses around the teeth in this quadrant. The mildest reaction occurred around the distal root of the upper right second premolar (Fig. 6). The lesion was small, although heavily infiltrated with inflamma.torp cells. Illustrative of an extensive lesion in this quadrant was the one surrounding the distal root of the upper right third premo1a.r (Fig. 7). The granuloma extended for a considerable distance around the root on both sides and contained a central area of liquefaction necrosis. On the periphery, there was new bone formation and collagen deposition. Despite the ext,ensireness of this lesion, t,he roentgenogram revealed only an apical thickening.
Fig. 6. Photomicrograph of section through apical region of upper right second premolar, distal root, of Dog 2. This root canal had been filled with silver cones in contact with vital apical pulp tissue. A small periapical granuloma (G) is present. RA, Root apex; PL, periodontal ligament; B, bone. (Magnification, x54; reduced IL.)
646
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Moochik
Fig. 7. Composite photomicrograpll of se&on t,hough apical region of upper right thirtl p1 l>IUOhr, distal root, of Dog 2. This canal was filled was a. silver cone. Sole vx-lr nsiw gr. %nuloIna (G) containing arca of liquefaction nwrosis (1,X). AR, Apical rwnifica tion : x54; reduced I/.! R, resorption of cementurn (C); Ii, hone. (2Iagnification,
Upper left quadrant. Thv cwltnrc from Ihe canal of the upper left first w~~olar was negative; all other canal cultures were positive. Howtvr, t here PI Wi YS no apparent relationship between the absence or presence of infection and th c severity of the inflammatory responw. Granulomas ranging from small to moderate in size ww-e noted. There u a.round the upper Sill(la11 granuloma Icft first premolar; within ii, tht>rcL
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liquefaction necrosis. The inflammatory cell density was small. Osteoblastic activity and new bone formation were evident around the lesion. Around the canals of the upper left third premolar, which yielded positive cultures, the lesions were similar to each other in character. A moderate-sized lesion was seen around the distal root. Although larger than the lesion around the first premolar, the inflammatory cell density was small in both, and there was evidence of new bone formation around the periphery. Some epithelial proliferation was evident. The lesion extended in a coronal direction about one third the length of the roots. The upper left second premolar was treated similarly to the other teeth of t,his quadrant, except that the root canal filling was omitted inadvertently. An area of rarefaction was present around both roots. Some root resorption was evident, but the inflammatory cell density was small. The lesions were smaller than those around the filled roots of the upper left third premolar. Lower right quadrant. The fate of the remaining inflamed vital pulp tissue when in contact with N, was studied in the teeth of this quadrant. In no instance was any vitality maintained; nor was a “sclerotic” zone evident at the place of pulp amputation. Periapical lesions varied from mild to moderate in severity. A typical lesion of this quadrant was the one around the distal root of the lower right third premolar. The remaining pulp tissue had become necrotic. In thr root canal, N, was dispersed throughout the necrotic pulp tissue. A moderatesized granuloma was present periapically. Chronic inflammatory cells were present in all the apical foramina. There were areas of liquefaction necrosis within some lesions in this quadrant. Lower left quadrant. The extent of the lesions in this quadrant varied greatl,v. There was a minute amount of granulation tissue at the apex of the distal root of the lower left second premolar. A more extensive lesion was observed around the mesial root of the lower left second premolar. Some of the other lesions observed were the largest of any seen in this animal. In the largest lesion around the mcsial root of the lower left third premolar (Fig. 8)) resorptions of the root had occurred on both the mesial and the distal aspects. The lesion did not extend periapically into the bone, as the other granulomatous lesions did; instead, the granulomatous tissue extended for a considerable distance around the sides of the root, extending almost halfway up the root in a coronal direction. There was considerable bone resorption on the periphery of the lesion. Liquefaction necrosis was evident around t,he sides of the roots. Small granulations were observed in the bone and periodontal ligament crownward to the main lesion. There was abundant collagen and/or osteoid deposition ?n the periphery of all the lesions, regardless of their extensiveness. Radiographically, the lesions on the mcsial root of the lower left third premolar, the most extensive in this quadrant, appeared smaller than that of the distal root of the lower left third premolar (Fig. 12, B). Histologically, the latter lesion was much less extensive, emphasizing that the size of a roentgenographic area of rarefaction neither coincides with nor is diagnostically indicative of the actual histologic extent of the lesion. In general, it was observed that wherever inflamed pulp tissue ~7rasleft in
648
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0.8.. O.M. $0.1’. Mav*> 1966
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the root canal greater periapical inflammatory lesions resulted. This occurred regardless of whether N, or silver cones with cement were used for partial ohturation of the root canal. Dog 3 Upper right quadrant. Following extirpation of uninflamed pulps, N,-treated canals were compared with those treated by conventional methods. Another observation was also made; within the sa.me t,ooth, the prriapical reactions around a filled root canal were compared with those around an unfilled canal. Thus, previous pathologic involvements of the pulp and periapical tissues, being a,bsent, could have no influence on the findings. All lesions observed in this quadrant were small and mild in inflammatory cell density. The distal root of the upper right second premolar and the me&al root of the third premolar had histologically similar lesions. They were typical of the lesions in this quadrant. A slightly denser magnitude of inflammatory cells was present around the distal root of the upper right second premolar than around the mesial root of the upper right third premolar. In the former, there was more N, in contact with the remaining pulp. In all cases, the pulps adjacent to the N, were necrotic and chronic inflammation resulted periapically. Upper Zeft qua&ad. There were lesions around all the teeth, but. thry were generally smaller than those in the quadra.nts where silver cones were used to obturate the canals. Proliferated epithelium was found in all the lesions; microcysts had formed in most of them. The lesion around the distal root of the upper left third premolar was typical of those present in the entire quadrant (Fig. 9). The granuloma was small, and sheets of epithclium wrre present. A small lumen was developing in a region of degenerating epithelial cells, forming a microcyst. Lower right quadrant. The same type of lesion was found around all of the root apices in this quadrant, differing only in size. In general, fairly large cysts or granulomas containing epithelium were found around the apices of both filled and unfilled canals. Typical of the lesions in this quadrant were the ones around the distal root of the lower right third premolar and the mesial root. of the lower right fourt.h premolar. Proliferated epithelium extended from one side of the root to the other, Lumina were observed, around which degenerating epithelial cells were evident (Fig. 10). NW bone formation was also found on the periphery of all the lesions. Lower left quadrant. The lesions around the teeth in this quadrant were similar to those observed on the lower right side. Large periapical lesions containing epithelium, with evidence of new bone format,ion on the periphery, were found in every case. Around the unfilled canals, the lesions were larger. Typical of the lesions of this quadra.nt was the one around the distal root of the lo~+r left third premolar (Fig. 11). This lesion was the largest in size, and it was present around a root with an unfilled canal. Proliferated cpithelium with three distinct lumina was observed. New bone formation was seen on the periphery of the lesion. In general, where N, was used, the least inflammation was noted around the canals that were more thoroughly obturated. In the lower quadrants, where
Pig. 9
Fig. 9. Section through apical region of upper left third prenmlar, distal root, of Dog 3. Nz ~vas used to fill root canal, in contact, with previously uninflamed pulp tissue. Multiple foramina (MP) opening through dentin In) all contain necrotic pulp tissue (X). Surround ing root apex (RA) is proliferating cpithelium (IC) which has degenerated in seme regions, forming a microcyst (XC). C, Cemcntum; H, bone. (Magnification, x54 ; retlm~c~~lIL.) Pig. 10. Photomicrograph of srction of apical lesion from mesial root of lolver right fourth premolar of Dog 3. Granuloma contains degenerating epithclial cells (E-DE), polymorphonuclear leukocytes (I’), and dilated blood vessels (BP). (Magnification, x%0; rrduced r/cl.)
silver cones were used, thcrc were similar findings; the more complete the obturation, the less the periapical inflammation. On the other hand, tissue reactions around the roots with unfilled canals were the most severe. All of the re maining pulp tissue was invaria.bly necrotic, regardless of whether silver cones or N, had been used for canal fillings. DISCUSSION In the entire study, the least amount of periapical destruction was observed around the teeth whose root canals had been treated with N, Medical and filled with N,; there was slightly more periapical destruction around the canals that were obturated with silver cones and root canal cement. These results are in contradiction to those reported by Kuroiwa.3 Since the canals of some teeth were treated with N, Medical, and some with camphorated paramonochlorophenol, it is possible that N, Medical is a more effective germicide than camphorated paramonochlorophenol. Rappaport and associates”found this to be so in their study. However, the antibacterial effectiveness of N, may vary as the formula varies. When the formula was presented to the Council on Dental Therapeutics of the American Dental Association in 1963, the paraformaldehyde content was given as 4.7 per cent. Successive analyses,
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Pig. 11. Photomicrograph of section through apical region of lower left third premolar, distal root, of Dog 3. Extensive granuloma (G) is present around root apex (RA). Lesion extends along both sides of root. Dentin (D) and cementum (6’) have been resorbed (R). Three lumina (L) have formed in proliferating epithelium (EP), indicating that a cyst has developed. B, Bone. (Magnification, x54; reduced $4.)
by public analysts, showed variations in the paraformaldehyde content from 0.22 to 6.0 per cent.17 Obviously, the bactericidal effect would be influenced by the content of formaldehyde. The remaining constituents of the formula also \-aried widely. For example, in all the samples studied privately, lead oxide was a major ingredient, varying from 19.5 to 26.9 per cent. Yet, lead oxide is not mentioned at all as an ingredient on the package circular or in the formula given to the American Dental Association.l’ One of the indictments against N, as a root filling agent is that it is impossible (or, at best, difficult) to control precisely, its placement in the canal. An attempt to pack N, tightly into a canal will likely result in overfilling. The
652
Snyder, Seltzer, aid .lfoodwil:
Fig. Id. A, Bt and C, Roerhgenograms of four quadrants of Dogs 1, 8, n11dB after ilt%tli. 1, Upper right quadrant; 8, upper left quadrant; 3, lower left quadrant; 4, lamer right quadrant.
effects of overfilling with N, were studied in one case. N, was well tolerated and walled off with a cementum-like tissue when it was inadvertently forced beyond the apex. Although the lesions in all of the animals varied widely, N, appeared t.o stimulate the deposition of collagen and/or osteoid in large amounts. This deposition was observed at a distance from the destruction that resulted when N, contacted pulp tissue. These findings contradict many reports which claimed that N, is severely irritating to the periapical tissues. They would seem to support Sa,rgenti and Richter’s claim that N, may enhance hard tissue apposition. Calcification of the collagen fibers and blood vessel walls of the lesions in the first dog was observed. However, t.his calcification was not due to the action of the N,, since such calcification was present in all the lesions, including those around root canals which were dressed with camphorat,ed pa.ramonoc,hlorophenol but unfilled. Whether this calcification was a result of the deposition of calcium in tissue which was injured, degenerating, or necrotic is unknown. Where inflamed pulp tissue was deliberately left in the canal, the pattern of inflammatory response was erratic, varying from mild to severe. Why there should be such a variance in reaction in the same quadrant of the same animal is not known. The cultures of these teeth were all positive, tending to cancel out the presence of bacteria as a factor. Furthermore, in two dogs results were similar, regardless of culture findings. One difference between the reactions around some teeth was the proliferation of epithelium. That such proliferation was not caused by microorganisms was borne out in the lesions of the third a.nimal. In these teeth there was no ba.cterial contamination ; yet there was frequent evidence of epithelial proliferation. This cpithelial proliferation was noted in almost all of t.hc lesions, regardless of the management of the canals. The range of reaction varied from sheets of epit,helium dispersed through the fibrous tissue of the granuloma to large, frank cysts with more than one lumen. Around all of these cystic lesions, there was new bone deposition and repair. Similar findings of periapical cyst formation in dogs, unrelated to the presence or absence of microorganisms, were noted by Seltzer and colleagues.18 Our studies show that there was no evidence of any vitality; nor was a “sclerotic zone” (Sargenti and Richter) observed at t,he region of pnlp amputation. However, there a.ppeared to be a correlation between the degree of repair and the distance of the N, from the apex, confirming the findings of Iten and of Nieholls.12 It would appear, therefore, that the inflammatory response may vary, depending on the level of pulp amputation and the amount of N, in the canal. However, our findings differ in other respects from those of Iten and Nicholls. Although they found some vital pulp tissue in the apical area, we found only necrotic tissue. Iten found fixation of the pulp closest to the N,; we found total architectural destruction. There appears to be a direct correlation between maximal debridement and obturation and apical healing. Since there was some attempt at repair in every yuadrant of Dog 1, it, is our
R~‘~ittYllWS 01’ lll(l ittv;tt~i;rI~ly
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tltc t1q.p~~ or ittjitry itiflucwcw 111~ittflatrttnator~~ twpottw. ‘I’ltc~t~~ appcarcd to b(b il. dirM rcli~tiol~ship h:twcv:n tllcl c~llillltity Of tllcl irt*it;rnt,, inflamed pulp tissue, and the subsequent response, an arca of rarefaction. N, apparently did not cure inflamed palp tissue, as claimed by Sargenti and Richter. tissue became necrotic following partial pulp X~en previously uninflamed pulp extirpation, and chronic periapical in8ammation resulted. Hower~, the lesions were smdler and had less inflammatory ccl1 density in the Y,-filled canals than those of the roots filled with silver cones. The ralidity of the concept of par&l pulp removal, particularly where inflamed pulp tissue is present, is open to question. In cases of pulpitis, where is the optirnum plane of pulp scvcraiic( ‘“z Should the wound be made in the apical third, close to the apical foramen, in the pulp tissue tl1a.t is less cellular and more fibrotic? Or is it better to amputate the pulp in the middle t,hird of the root canal and leave a more cellular pulp tissue 3 This question cannot 1)~ I’Csolved definitely, since it is dificult, if not impossible, to detcrrnine at, what level the inflammator,v process can be reversed. Also, it is doubtful, from a technical standpoint, that a pulp can be amputated at a specific level. It is oul impression that when canals arc treated with camphorated paramonoclllorophenol or NZ, repair is encouraged when no pulp tissue is left in the main c>anal and t,he canal is obturated as thoroughly as possible. logic+ I’nnctiotts,
SUMMARY
In an effort to simula.tc clinical conditions in human teeth, dental p~Jps in dogs were injured and exposed to the oral fluids for varying periods of time to prodncc inflamed and/or necrotic pulps. In one of the dogs, the pulps were not, injured prior to the experimental procedures. Root canal treatment procednrcs employing N, Medical and N, and n more sta.ndardized treatment using silret cones and root ca.nal cement wrrc performed on three dogs. In addition, some canals were instrumented hut not fillrd. Because bot!h the technique and the effects of the drugs were to 1~ compared, the standard technique was modified so that the completeness of root fillings could bc comparable to that, of the N, tc~chniqnc. The animals WW(L killed 6 to 1 llh months aft,er t,hc c)p(Lr;ltivc pt’oc~cdr~rcs. Compilrativc ltistoloaic stutlics of the pcJl*iapical tissue 1’6~itctiOrls \vt’t’(’ 1 1lPll
Klilil(~.
CONCLUSIONS Specific
1. In the teeth of dogs, thorough debridemcnt and obturation of the root canal seemed to be more important for repair of the periapical tissues than t,he material used as a root canal dressing or as a filling agent. 2. The periapical tissues of the teeth treated with N, were less inflamed than the tissues of the teeth fillctl with silrrr cones. These results wcrc obssrrrrcl in
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teeth in which the mechanical instrumentation and the root. canal fillings wcr(’ performed as thoroughly as possible. 3. N, was a less irritating root canal ccmcnt than a silver-containing root canal cement (modified zinc-oxide-eugenol). Where N, was forced beyond the apex, it was well tolerated by the periapical tissues. 4. Ir;, as a filling agent is difficult to manipulate precisely. 5. The apical pulp tissue in contact with N, became necrotic in every cask. 6. N, is not a panacea. It is not a substitute for complete ddbridement, enlargemcnt, and filling of root canals. General
1. Thorc was IIO correlation bctwcen the apparent size of a lesion, rocntgenographically, and the actual extent of the lesion, histologically. The absence of :I roentgenolucent area on the roentgenogram did not preclude the prcsencc ol’ a pa.thologic area histologically. 2. There did not appear to bc a reliable pattern of healing following endodontic therapy. R’esults varied widely in the same animal, in the same quadrant,, and under the same conditions. 3. In some instances, endodontic procedures induced the proliferation of epithclial rests and subsequent cyst formation. 4. Fibrous encapsulation and peripheral osteogenic a&ivit,y occurred in cvcry case of cyst formation. 5. It should be apparent t,hat this st,udy does not answer all of the questions concerning healing in relakion to X2. It does bring into sha,rp focus the unpredictability of periapical repair in dogs’ teeth, regal *dlcss of thr technique cmployed. REFERENCES
of Teeth With Diseased 1. Rose, C.: Treatment A., and Richter, S. L.: Rationalized 2. Sargenti,
1961, AGSA Scientific Publications. K. : Experimental Study on Root Canal Filling Using Sew Filling Material N? and AN,, Bull. Oral Path. 4: 45, 1960. Council on Dental Therapeutics : Hazards of Formaldehyde Preparations for Single Treatment Procedures in Endodontics-N, and the R-Method, J. Am. Dent. A. 64: 689, 1962. Bertolini, A. G.: Recherches bacteriologiques sur le X3, substance pour l’obturation radiculaire, Schweiz. Monatschr. Zahnh. 68: 221, 1958. Rappaport, H. M., Lilly, G. E., and Kapsimalis, P.: Toxicity of Endodontic Filling Materials, ORAL SURG., ORAL MED. & ORAL PATH. 18: 785, 1964. Overdiek, H. F. : Zur Gewebsreaktion auf implantierte Wurzelfullmaterialien im Vergleich zum N?, Zahnarztl. Rundschau 11: 402, 1960. Guttuso, J. : Histopathologic Study of Rat Connective Tissue Responses to Endodontic Materials, ORAL SURG., ORAL MED. & ORAL PATH. 16: 713, 1963. Zerosi,, C., Barat,ieri, A., and Amici, G.: Osservazioni istologiche sul comportamento dei tessutl periapicali dopo otturzione canalare con cement0 K,, Rx%. t,rimrst. odont. 15: 555, 1959. 1ten, J. : Klinische untl Histologische TTntoruucllungell mit, 11t.r \Vur~.c,lfu~.llrrl;ll csricnl Sz, Inaugural dissertation, Arand Druek, Bern, Basil, 1958. Overdiek, II. I?. : Pulpenreaktion auf NI im .Jurz~~!it-\‘er~uc,ll, 1hwtsvllr%:~l~tr. %t,scllr. 10: 7X6, 1960. Nicholls, E. : A Study of N-2 ,in <:rossnlall, L. I. (editor): Trttnsactions of t,llt: ThiI~cl Internat. Conference on Endodontics, Philadelphia, 1963, University of Pennsylvania, 1,. 52. Rowe, A. H.: A Histologic Study of the Healing of Pulp Remnants Under N-2 Root Canal Scaler, Brit. D. J. 117: 27, 1964.
<3 . Kuroiwa, 4. 0. 6. 7. 8. 9.
10. 11. 12. 13.
Pulps, Dental Cosmos 36: 358, 1894. Root Canal Treatment, ed. 3, Yew York,
cm 2000 l’ceth Filled \Vith N-2 During it I’vrio
ORAL MED. & ORAL PATH. 17: 507. 1961.