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JOURNALOF ENDODONTICS
Copyright 9 1985 by The American Association of Endodontists
Printed in U.S.A.
VOL. 11, NO. 1,JANUARY1988
Biological Evaluation of the Apical Dentin Chip Plug
Evaluacion Biologica del Tapon de Virutas en la Zona
Apical
Kamran Safavi, DMD,MEd, Preben Hc~rsted, DDS, Elizeu A. Pascon, DDS, MSD, and Kaare Langeland, DDS, PhD
accion del tejido periapical al tapon de virutas de
dentina, e investigar si ese tapon puede actuar
como una barrera biocompatible entre el tejido periapical y el material de obturacion del conducto.
Autologous dentin chips were packed in the apical
part of root canals of baboon teeth. Root canals
were then filled with Hydron using a pressure syringe technique. Histological periapical response
was evaluated up to 114 wk. Complete apical closure did not occur and material particles were observed in periapical tissues.
MATERIALS AND MEq'HODS
Four 14-kg baboons were used for this study. The
baboons were anesthetized with an intramuscular injection of an initial dose of 5 ml of solution combining 2
ml of 100 mg of ketamine HCI/ml (Ketaset; Bristol
Laboratories), 1.5 ml of 10 mg of acepromacine/ml, and
1.5 ml of 0.4 mg of atropine/ml. Additional one-half
doses were injected when required. A full-mouth series
of radiographs were taken of each baboon and 24
teeth, with complete root formation, were selected for
the study. Teeth were scaled and individually isolated
with a rubber dam. The crowns of the teeth were
scrubbed with a 30% hydrogen peroxide solution using
a cotton applicator and then dried by air syringe. With
the use of a fresh cotton applicator, a 5% solution of
tincture of iodine was applied over the crown, the
clamp, and the surrounding rubber dam. The access
cavity was prepared with a sterile, round high-speed
bur and no water spray. The coronal pulp tissue was
removed with sterile spoon excavators and/or lowspeed round burs, and the canal orifices were located
with an endodontic explorer. A 1% sodium hypochlorite
solution and suction was used for irrigation. The
method described by Baume et al. (12) was used to
establish the dentin chip plug. By using the periapical
radiograph and the root canal diameter, the tentative
working length was estimated and a flat-ended reamer
slightly larger than the root canal diameter was selected
and inserted into the canal 2 to 5 mm short of the
radiographic apex. If the tip of the reamer did not come
into contact with the canal walls at this level, the reamer
was removed and a larger size was inserted into the
root canal until it bound to the dentin walls 2 to 5 mm
short of the radiographic apex. A working length radiograph was taken at this time (Fig. 1). If the tip of the
reamer was more than 5 mm short of the radiographic
All root canal sealers studied until now are known to
be toxic (1,2). Extrusion of root filling materials into the
periapical tissue causes an inflammation, including foreign body reaction, and contributes to poor prognosis
and failures in root canal treatment (3). Apical dentin
chip plugs are suggested to prevent overfilling during
root canal obturation (4, 5) and, at least in noninfected
root canals, appear to be compatible to periapical tissues (6-11).
A technique for pulpectomy and the simultaneous
creation of an autologous dentin plug is described by
Baume et al. (12).
The purpose of the present study was to examine
periapical tissue reaction to a dentin chip plug and to
investigate if such a plug can act as a biocompatible
barrier between periapical tissue and root canal filling
material.
Se sabe que todos los selladores o cementos de
obturacion estudiados hasta ahora son toxicos. La
extrusi6n de materiales de obturacion de conductos
en el tejido periapical causa inflamaci6n incluyendo
reacci6n a los cuerpos extra~os y contribuye a un
peor pronostico y fracasos en los tratamientos de
conductos. El tap6n de virutas dentinarias en la zona
apical se sugiere para impedir la sobreobturacion
del conducto, y al menos, en conductos no infectados, parece ser compatible con los tejidos periapicales. Una tecnica para la pulpectomia y la creaci6n
simultanea de un tapon dentinario autologico es
descripta por Baume (1971).
El proposito de este estudio fue examinar la re18
Vol. 11, No. 1, January 1985
Apical Dentin Chip Plug
19
TABLE 1. Observation periods
Tooth
b:m.,,
~z, ~il
FiG 1. Baboon C, tooth #1.1. Observation period was 1 wk. A,
Working length. B, Postobturation. C, Specimen radi~:jraphs.
apex, a reamer with a smaller diameter was selected
and a new working length radiograph was taken. The
reamer was then removed and the working length was
recorded. At no time was any instrument allowed to
pass beyond the planned apical extension. Once the
working length was established, the reamer was reinserted into the canal and repeatedly rotated 180 ~ clockwise and then counterclockwise, removing the pulp
tissue and bringing dentin chips into contact with the
apical pulp stump simultaneously. Canals were irrigated
periodically with a 1% solution of sodium hypochlorite
and dried with paper cones. With the use of flat-ended
Hedstrom files and an axial movement, the canals were
cleaned and shaped, gradually increasing the size of
the files while additional dentin chips were carried apically and packed into the apical part of the canal until
a definite "stop" was established 2 mm short of working
length and no hemorrhage and/or exudate could be
detected by bringing paper cones into contact with the
dentin chip plug. The presence of the dentin chip plug
was also checked with a small file.
Occasionally, a bacterial culture was taken from the
root canals after neutralization of sodium hypochlorite
with a 5% thiosulfate solution and using a preheated
oxygen reduced thioglycollate medium.
Canals were then dried and filled with Hydron (NPD
Dental Systems Inc.) using a pressure syringe, according to the manufacturer's directions (13). Hydron was
allowed to set before filling the access cavity with
amalgam and a postobturation periapical radiograph
was taken (Fig. 1). Cultures were incubated and read
periodically for up to 7 days.
The animals were sacrificed by intracardiac injection
of Somlethol (1 ml/10 Ib; Med-Tech, Inc). The observation period for each tooth is given in Table 1. The
jaws separated in the median line were removed in
blocks and radiographed (Fig. 1). By using a round bur
and a low speed, holes were drilled through the cortical
bone and specimens were placed in 10% neutral buffered formalin for 48 h. The jaws were sliced into separate blocks that contained a whole tooth using a
circular diamond saw, cooled with water. The specimens were decalcified in a solution of 22% formic acid/
sodium citrate buffer mixed in equal parts. Periodically,
TOtals:
1.1
1.3
1.4
1.5
1.6
2.1
2.2
2.2
2.3
2.4
2.4
2.4
2.6
3.1
3.3
3.3
3.4
3.4
3.5
3.6
4.1
4.2
4.3
4.5
24
Baboon
No. of
Canals
C
B
A
B
B
B
A
C
C
A
C
D
C
A
B
C
B
D
D
A
A
C
C
D
4
1
1
3
3
3
1
1
1
1
3
3
3
3
1
1
1
2
2
2
3
1
1
1
2
44
Observation
(wk)
1
84
54
91
68
85
52
5
5
50
1
104
5
51
90
5
95
112
114
48
52
5
5
113
1-114
decalcification was checked by taking radiographs. The
specimens were trimmed with a razor blade, reducing
the blocks to a smaller size, containing only the apical
half of the roots and surrounding bone. On completion
of decalcification, the specimens were rinsed overnight
to remove the decalcifying agent and processed for
histological examination. Paraffin-embedded specimens were mounted in a sliding microtome and 144
serial sections of 5-#m thickness were cut, aiming to
get the canal, foramen, and surrounding tissues of the
periapical region in the same slide. Every third slide
was stained with hematoxylin and eosin. Selected
slides were stained with Masson trichrome and Brown
and Brenn.
OBSERVATIONS
One tooth (#3.1, baboon A) was excluded from the
study because of uncontrollable bleeding during the
dentin chip packing procedure. No overfilling was observed in postobturation radiographs.
Follow-up radiographs taken from block sections on
the day of sacrifice were evaluated using Strindberg's
criteria (3). All the root fillings, except one (mesial root
of tooth #3.5, baboon D), were categorized as successful. All preobturation cultures were negative up to
7 days. Parts of apices of four roots (tooth #1.3 and
buccal roots of tooth #2.6 in baboon C and palatal root
of tooth #2.4 in baboon D) were lost during trimming
of the decalcified specimen. These roots were excluded
from the study. The remaining 39 roots were available
20
Safavi et al.
Journal of Endodontics
FIG 2. Baboon 8, tooth #3.3, Dentin chips and Hydron. Observation period was 90 wk. A, Root with adjacent bone (original magnification x20).
B, From area indicated by horizontal arrow in A. Dentin chips mixed with Hydron (original magnification x630). C, From area indicated by oblique
arrow in A. Hydron in apical pulp tissue (original magnification x630). D, From area indicated by vertical arrow in A. Hydron in foreign body cells
in apical foramen (original magnification x630). E, From area indicated with double arrows in A. Hydron in periapical tissue (original magnification
x630).
Vol. 11, No. 1, January 1985
for light microscope observation. Six roots, in which
sections did not contain apical root canal including the
foramen with direct connection into the periodontal
ligament, were also eliminated from the study. Thus,
33 roots in which root filling material, dentin chip plug,
apical foramen, and surrounding periapical tissue were
all present in serial sections were evaluated in this study
(Fig. 2).
The filling material was observed short of the dentin
chip plug in some sections and mixed with dentin chips
in others (Fig. 2).
The length of the dentin chip plug varied in different
root canals and different sections of the same root
canal. The distance between the material/dentin chip
"interface" and the apical foramen ranged from 0.8 to
6.9 mm. Hydron particles were observed in the apical
Apical Dentin Chip Plug
21
pulp tissue of 12 canals extending to periapical ligament
in some sections (Fig. 2).
Extruded particles were observed among dentin
chips in macrophages, foreign body cells, in vessels in
the remaining apical pulp tissue, in the periapical tissue,
and in the periodontal ligament apical to the apex (Fig.
2).
Hard tissue appositions were frequently observed on
root canal walls in 48- to 118-wk observation periods
(Figs. 3 to 5). The hard tissue appositions appeared to
form a complete apical closure in some sections. However, serial sections of the same root canal showed
openings in the apparent obliteration. Vital pulp tissue
was also observed coronal to the "apical closure" in
some sections (Figs. 3 and 4).
The only failed root canal had vital residual pulp 6.9
FiG 3. Baboon D, tooth #3.5. Distal root. Dentin chips and Hydron. Observation period was 114 wk. A, Hard tissue apposition on canal walls
and remaining pulp tissue (original magnification x20). B, Another section a few microns apart from A (original magnification x20). C, From area
indicated by a r r o w in B. Remaining pulp tissue 3.5 mm from the apex. Vessels with agglutinated erythrocytes and visible nuclei.
22
Safavi et ai,
Journal of Endodontics
FIG 4. Baboon B, tooth #1.5. Palatal root. Dentin chips and Hydron. Observation period was 91 wk. A, Dentin chip plug indicated with horizontal
arrow (original magnification x28). B, Another section, a few microns apart from A. Apparent apical closure indicated with horizonta/arrow
(original magnification x28). C, From area indicated with vertical arrow in A. Erythrocytes 2 mm coronal to the =apical closure" (original
magnification x1250). D, From area indicated with vertical arrow in B. Soft tissue 2 mm coronal to the apex. The apparent closure is a section
of the root canal wall.
Vol. 11, No. 1, January 1985
Apical Dentin Chip Plug
23
a
FIG 5. Baboon B, tooth #1.5. Palatal root. Dentin chips and Hydron. Observation period was 91 wk. A, From area indicated with oblique arrow
in Fig. 4A. Apposition of hard tissue between dentin chips and instrumented canal wall (original magnification x1250). B, From area indicated
between horizontal arrows in Fig. 4A. Cell inclusions 1.8 mm coronal to the apical closure (original magnification •
mm short of the apical foramen. The severe pulpal
inflammation, including dense concentration of lymphocytes and neutrophilic leukocytes, extended beyond
the apical foramen into the periapical lesion which did
not contain any filling material. No bacteria were observed in Brown and Brenn-stained section.
DISCUSSION
Although the presence of dentin chip plugs was in all
but one case clinically verified, histological observation
of serial sections revealed many incomplete plugs and
great variations in plug length and the distance of the
plug from the apical foramen.
The risk of overfilling during obturation is the major
drawback of pressure syringe techniques. Although no
radiographically observable overfilling occurred, material particles were present in periapical tissue in many
cases, indicating that the dentin chip plug was not a
complete barrier in a pressure syringe technique. Apparent complete obliteration of the root canal with a
hard tissue apical to the dentin plug was a common
observation. However, observation of incomplete obliterations and presence of vital pulp tissue coronal to the
"bridge" calls for caution when reports of complete
biological sealing of the apical foramen with dentin chips
are evaluated.
Observation of only minor tissue reactions to the
dentin chips in our material is in agreement with studies
by Tronstad (4). Negative bacterial cultures and the
24
Journal of Endodontic8
Safavi et al.
absence of bacteria in Brown and Brenn-stained sections indicate that in our materials the dentin chips were
not contaminated. In the case of necrotic pulps, dentin
chips may contain bacteria (14, 15) and cause an
unfavorable periapical tissue response (16).
CONCLUSIONS
1. Complete dentin chip barrier to root filling materials
could not be achieved with the method used.
2. Hard tissue formation was common but no total
apical closure occurred,
3. Tissue response to dentin chips was generally
favorable.
This study was supported by United States Public Health Service Grant 5
RO1 DE04096-05.
Dr. Safavi is assistant professor and director of the Graduate Endodontic
Program, Department of Endodontics, School of Dental Medicine, University of
Connecticut Health Center, Farmington, CT. Dr. Horsted is associate professor,
Department of Dental Pathology and Operative Dentistry, Arhus Tandlaegeh~jskole, The Royal Dental College, Vennelyst Boulevard, DK-8000 Arhus C.,
Denmark. Dr. Pascon is assistant professor, Department of Endodontics,
School of Dental Medicine, University of Connecticut Health Center. Dr. Langeland is professor and chairman, Department of Endedontics, and chief, Endodontic Service, John Dempsey Hospital, University of Connecticut Health Center.
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