1. science
2. medicine
3. surgery

Postoperative pain after 1- and 2-visit root canal therapy
Anthony DiRenzo, DDS,a Tim Gresla, DDS,b Bradford R. Johnson, DDS,c Martin Rogers, DDS,d
Dennis Tucker, DDS,e and Ellen A. BeGole, PhD,f Chicago, Ill
UNIVERSITY OF ILLINOIS AT CHICAGO
Objectives. The factors that influence postoperative pain after root canal treatment are not completely understood. The
purpose of this prospective clinical study was to evaluate postoperative pain after root canal therapy performed in 1 appointment versus 2 appointments.
Study design. Seventy-two patients requiring root canal therapy on permanent molars were included in this study. Patients
were randomly assigned to either the 1-appointment or the 2-appointment group. Both vital and nonvital teeth were included.
The standardized protocol for all teeth involved local anesthesia, isolation and access, engine-driven rotary nickel-titanium
canal instrumentation to a minimum size #5 (.028 mm) .04 taper Profile with step-back flaring, and irrigation with 2.5%
NaOCl. Teeth in group 1 (n = 39) were obturated at the first appointment by using laterally condensed gutta-percha and Roth
811 sealer. Teeth in group 2 (n = 33) were closed with a sterile dry cotton pellet and Cavit restoration and were obturated at a
second appointment 7 to 14 days later. A modified Visual Analogue Scale was used to measure preoperative pain and pain at
6, 12, 24, and 48 hours after the first appointment. Statistical analysis was performed to compare groups at each interval by
using an independent-samples t test with Bonferroni adjustment.
Results. There was no statistically significant difference between groups at preoperative intervals or at any of the 4 postoperative intervals (P < .01).
Conclusions. There was no difference in postoperative pain between patients treated in 1 appointment and patients treated in 2
appointments. The majority of patients in both groups reported no pain or only minimal pain within 24 to 48 hours of treatment.
(Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:605-10)
Postoperative pain after nonsurgical root canal treatment has been reported to range from approximately
3% to more than 50%.1-5 Pain associated with root
canal therapy is a poor indicator of pathosis and an
even more unreliable predictor of long-term success.6
One-appointment root canal treatment is generally
considered to be efficient, but the more important questions concerning the incidence of postoperative pain
and prognosis for long-term healing remain unanswered. The preponderance of the research to date has
shown either no significant difference in postoperative
pain when 1-visit root canal treatment is compared
with multiple-visit treatment1,3,7 or less pain with 1-visit
treatment.4,8,9 However, many of these studies were
retrospective studies or prospective studies without
adequate controls or randomization. Prospective,
randomized studies are generally believed to provide
aPrivate
endodontic practice, Youngstown, Ohio.
endodontic practice, Winchester, Minn.
cClinical Associate Professor and Director of Postdoctoral Endodontics, Department of Endodontics.
dClinical Assistant Professor, Department of Endodontics.
ePrivate endodontic practice, Plymouth, Mass.
fAssociate Professor, Department of Orthodontics.
Received for publication Jul 16, 2001; returned for revision Sep 20,
2001; accepted for publication Nov 4, 2001.
© 2002 Mosby, Inc. All rights reserved.
1079-2104/2002/$35.00 + 0 7/15/121900
doi:10.1067/moe.2002.121900
bPrivate
the highest level of support for evidence-based clinical
practice.
The purpose of the first phase of this clinical study
was to evaluate the incidence and severity of postoperative pain after root canal therapy performed in 1
appointment and 2 appointments. The relationship of
preoperative pulpal diagnosis to postoperative pain was
also analyzed.
MATERIAL AND METHODS
Eighty patients requiring root canal therapy on
mature permanent maxillary and mandibular molars
agreed to participate in the study. Patients were
recruited from the regular pool of patients presenting to
the postgraduate endodontics clinic of the University
of Illinois at Chicago for routine and emergency treatment. Treatment was provided by 2 postgraduate
students in the Department of Endodontics (A.D. and
T.G.). When it was determined that a patient met the
inclusion criteria for this study, 1 of the 2 clinicians
discussed the study with the patient and solicited their
participation. Oral and written informed consent was
obtained from all study participants. The protocol and
informed consent forms were approved by the
University of Illinois at Chicago Institutional Review
Board. Patients who were pregnant, taking antibiotics
or corticosteroids at the time of treatment, immunocompromised, or under 18 years old were excluded
from this study. Preoperative diagnostic information
605
606 DiRenzo et al
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
May 2002
Fig 1. Visual analogue scale instrument (reduced in size for publication). Each horizontal line on actual scale
is 170 mm in length.
was obtained. Both vital and nonvital teeth were
included in the study.
Random assignment by coin toss occurred after
informed consent and agreement to participate in the
study, but before initiation of treatment. Each patient
recorded the preoperative pain level by using a HeftParker visual analogue scale (VAS), as well as a
reporting form modified by Rogers et al2 and previously tested at this institution (Fig 1). The clinicians
were trained in the use of the VAS instrument by one of
the investigators (B.R.J.), and standardized scripts
were rehearsed. Patients were told they could place a
mark anywhere on the horizontal VAS scale; furthermore, they were told to use the verbal descriptors as a
guide. Each patient mark was assigned a value between
0 and 170 on the VAS. Patients recorded their preoperative pain level in the presence of the clinician to
ensure that they understood the instructions. The clinician then recorded the dates and times for the
remaining 4 times, which corresponded to postoperative periods of 6, 12, 24, and 48 hours. The patient was
given the VAS form, along with a stamped, addressed
envelope for return of the form after 48 hours. Patients
were contacted by telephone at 24 hours and again at
48 hours to remind them to return the VAS form.
Responses were anonymous except for coding to identify group 1 and group 2 participants. All participants
completed the VAS form for the first appointment only.
The standard procedure for both groups at the first
appointment included local anesthesia, rubber dam
isolation, caries excavation, and standard access preparation. The pulp chamber and canals were irrigated
with 2.5% NaOCl throughout treatment. The ideal
working length for each canal was considered to be the
apical constriction as determined by an electronic apex
locator and 2 or more angled radiographs. Canals were
prepared with a combination of hand files and 0.04taper engine-driven rotary nickel-titanium files (Profile
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Volume 93, Number 5
DiRenzo et al 607
Fig 2. Visual analogue scale (VAS) values at each interval. A score of 70 is between mild and moderate on the
VAS, and a score of 20 is equivalent to faint. There was no significant difference (P < .01) between groups at
the preoperative interval or at any of the postoperative intervals.
Series 29; Dentsply Tulsa Dental, Okla) by using RC
Prep (Stone Pharmaceuticals, Philadelphia, Pa) canal
lubricant and sodium hypochlorite irrigation. Apical
enlargement was accomplished by using a minimum
size #5 Profile (0.28 mm) to the working length or to 2
file sizes larger than the first file to bind at the working
length, whichever was larger. Canals were step-back
flare-filed and dried with paper points. All teeth were
prepared to the same end point at the first appointment,
regardless of group assignment. Teeth in group 2 were
then closed with a sterile dry cotton pellet and a
minimum of 3.0 to 4.0 mm of Cavit temporary restorative (ESPE Dental AG, Seefeld, Germany). Teeth in
group 1 were obturated at the initial appointment by
using gutta-percha, Roth 811 sealer (Roth Co,
Chicago, Ill), and lateral condensation. Patients in
group 2 were seen for the second appointment 1 to 2
weeks later. Teeth in this group were isolated with a
rubber dam, the temporary restoration was removed,
canals were irrigated with 2.5% NaOCl and dried with
paper points. Minimal instrumentation was performed
with the master apical file, and working length was
verified by means of a radiograph. Canals were then
obturated and teeth temporarily restored by using the
same technique and materials as in group 1.
Each patient was given a prescription for 600 mg of
ibuprofen, with instructions to take only if needed for
pain. Patients were also reminded to fill out and return
the VAS form and were instructed to call the clinic if
adequate pain relief was not obtained with the
prescription. Any patient calling to report pain was
seen the same day for evaluation and treatment, if
necessary.
RESULTS
Seventy-two of the original group of 80 patients
returned the VAS form. Five patients initially assigned
to group 1 were dropped from the study because of the
inability to complete the treatment in 1 appointment.
Root canal treatment was completed at a subsequent
appointment, but VAS data from this subgroup were
not included in the study. Three additional patients did
not return the VAS form (2 from group 1 and 1 from
group 2). Thirty-nine patients had root canal treatment
performed in 1 appointment (group 1) and 33 had treatment completed in 2 appointments (group 2). The 2
groups were compared at each interval by using an
independent-samples t test (Fig 2; Table I). Because
there were 5 comparisons, the Bonferroni adjustment
was used to control for type I error, so that the level of
significance used was P < .01. There was no statistically significant difference between the groups at the
preoperative interval or any of the 4 intervals.
The groups were then subdivided by preoperative
diagnosis into vital (n = 55) and nonvital (n = 17)
groups (Tables II and III) and maxillary (n = 34) and
mandibular (n = 38) molar groups (Table IV). The
same statistical tests were performed. There was no
significant difference between any of the groups at any
of the intervals.
One of the 80 patients (1.3%) experienced a flare-up
that required a visit to the clinic on the day after the
initial appointment. The tooth was opened and irrigated, but no drainage was obtained. The patient was
placed on antibiotics and a narcotic analgesic. This
patient was in the 2-appointment group and presented
with a preoperative diagnosis of necrotic pulp and
608 DiRenzo et al
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
May 2002
Table I. VAS pain measurements for all cases (n = 72)
Interval
Preoperatively
6 h postoperatively
12 h postoperatively
24 h postoperatively
48 h postoperatively
No. of appointments
n
Mean VAS
SD
Maximum possible VAS mark
t
P
Mean difference
1
2
1
2
1
2
1
2
1
2
39
33
39
33
39
33
39
33
39
33
66.46
74.33
37.36
54.58
24.26
40.24
23.62
32.39
15.51
23.12
±50.14
±49.88
±32.61
±37.78
±28.48
±35.90
±24.36
±35.30
±24.58
±30.25
170
170
170
170
170
170
170
170
170
170
0.67
.51
7.87
2.08
.04
17.22
2.11
.04
15.99
1.24
.22
8.78
1.18
.24
7.61
There was no statistically significant difference at P < .01 between groups 1 and 2 at any of the intervals. The range of the VAS was 0 (none) to 170 (maximum).
VAS, Visual analogue scale.
Table II. VAS pain measurements for vital cases only (n = 55)
Interval
Preoperatively
6 h postoperatively
12 h postoperatively
24 h postoperatively
48 h postoperatively
No. of appointments
n
Mean VAS
SD
Maximum possible VAS mark
t
P
1
2
1
2
1
2
1
2
1
2
30
25
30
25
30
25
30
25
30
25
71.30
73.92
35.57
50.64
20.87
42.16
21.50
35.28
14.73
26.00
±49.17
±53.47
±30.27
±38.99
±25.48
±38.92
±23.32
±37.45
±26.55
±33.18
170
170
170
170
170
170
170
170
170
170
0.16
.88
Mean difference
2.19
1.61
.11
15.07
2.35
.02
21.29
1.60
.12
13.78
1.40
.17
11.27
There was no statistically significant difference at P < .01 between groups 1 and 2 at any of the intervals. The range of the VAS was 0 (none) to 170 (maximum).
Table III. VAS pain measurements for nonvital cases only (n = 17)
Interval
Preoperatively
6 h postoperatively
12 h postoperatively
24 h postoperatively
48 h postoperatively
No. of appointments
n
Mean VAS
SD
Maximum possible VAS mark
t
P
Mean difference
1
2
1
2
1
2
1
2
1
2
9
8
9
8
9
8
9
8
9
8
48.89
75.63
43.33
66.88
35.56
34.25
30.67
23.38
18.11
14.13
±52.22
±39.61
±40.94
±32.93
±36.23
±25.38
±27.81
±27.71
±17.45
±16.96
170
170
170
170
170
170
170
170
170
170
1.18
.26
26.74
1.30
.22
23.54
0.09
.93
1.31
0.54
.60
7.29
0.48
.64
3.99
There was no statistically significant difference at P < .01 between groups 1 and 2 at any of the intervals. The range of the VAS was 0 (none) to 170 (maximum).
acute apical periodontitis. The patient did not return for
subsequent treatment and did not return the VAS forms.
All patients were permitted to take analgesics as
needed. If pain medicine was needed, the patients were
encouraged to take the prescribed 600 mg of ibuprofen.
Approximately 20% of all patients reported taking
some type of analgesic. The patients who reported
taking analgesics were evenly distributed between the
2 experimental groups. Five patients reported taking an
over-the-counter pain medicine other than the
prescribed ibuprofen. To the best of our knowledge,
none of the patients took a narcotic analgesic—with
the exception of the previously noted patient who experienced a painful flare-up.
DISCUSSION
Our results are consistent with those of the majority
of the published reports on this topic. That is, postop-
DiRenzo et al 609
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
Volume 93, Number 5
Table IV. VAS pain measurements comparing maxillary molars (n = 34) with mandibular molars (n = 38)
Interval
Preoperatively
6 h postoperatively
12 h postoperatively
24 h postoperatively
48 h postoperatively
Tooth location
n
Mean VAS
SD
Maximum possible VAS mark
t
P
Mean difference
Maxillary
Mandibular
Maxillary
Mandibular
Maxillary
Mandibular
Maxillary
Mandibular
Maxillary
Mandibular
34
38
34
38
34
38
34
38
34
38
76.18
64.61
44.50
45.92
28.59
34.26
27.97
27.34
19.76
18.32
±50.54
±49.21
±37.59
±34.76
±35.81
±30.20
±34.82
±25.36
±32.87
±21.81
170
170
170
170
170
170
170
170
170
170
0.98
.33
11.57
–0.17
.87
–1.42
–0.73
.47
–5.67
0.09
.93
0.63
0.22
.83
1.45
There was no statistically significant difference at P < .01 between groups 1 and 2 at any of the intervals. The range of the VAS was 0 (none) to 170 (maximum).
erative pain associated with 1-appointment root canal
treatment is generally the same as postoperative pain
associated with multiple-visit treatment. Our results
also agree with the consensus that pulp extirpation
alone is probably the most significant factor in reduction of postoperative pain, regardless of other variables.
The vast majority of our patients in both groups
reported no pain or only minimal pain within 24 to 48
hours of treatment.
We elected to drop 5 patients from the study who
were assigned to group 1 because of the inability to
complete the treatment in 1 appointment. We did not
want to compromise our random assignment by transferring these patients to group 2, because we felt it was
possible that factors related to our inability to complete
treatment in 1 appointment could invalidate the results
from this subset of patients.
It is well known that pain perception is a highly
subjective and variable experience modulated by
multiple physical and psychological factors. Pain
reporting is influenced by many factors other than the
experimental procedure. In addition, the measurement
of pain is fraught with hazards and opportunities for
error. We selected a modified Heft-Parker VAS and a
reporting form used in a previous study at our institution.2 This is a bounded scale with absolute values at
each end and word descriptors of pain levels placed in
ascending order along the horizontal axis. The patient
is instructed to place a mark on the scale corresponding
to the current level of pain and has a visual reminder of
previous reports for comparative purposes. The location of the mark is measured and assigned a value
between 0 and 170. Heft and Parker10 state that the
unequal spacing of words on the scale represents an
accurate reflection of how patients perceive spacings
between the different pain word descriptors. When
properly designed and administered, a VAS is considered to be a valid and reliable ratio scale instrument for
the measurement of human pain intensity and unpleasantness.11
It is often difficult to compare results from different
studies because instrumentation and obturation techniques vary widely, especially in studies that are more
than several years old. The number of visits taken to
complete root canal therapy is only one of many variables. For example, when we developed this protocol,
a sterile, dry cotton pellet was the standard intraappointment dressing for most teeth that were treated
in more than 1 appointment. Our current treatment of
choice for teeth done in more than 1 appointment is to
place calcium hydroxide paste in the canals and pulp
chamber.
The incidence of postoperative pain is one of the
major concerns when evaluating endodontic treatment
alternatives. Under the conditions of this prospective
study, we found no difference in postoperative pain
between patients treated in 1 appointment and patients
treated in 2 appointments, regardless of preoperative
diagnosis or tooth location.
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Reprint requests:
Bradford R. Johnson, DDS
Department of Endodontics (M/C 642)
College of Dentistry
University of Illinois at Chicago
801 S Paulina St
Chicago, IL 60612
[email protected]
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