healthmedicinet

Hypotheses tested and outcomes measured

Three null hypotheses were tested in this study. First, there would be no difference
between the success rate of single-visit and multiple-visit non-surgical endodontic
treatment. Second, there would be no difference between the prevalence of postoperative
pain for single-visit and multiple-visit non-surgical endodontic treatment. Third,
there would be no difference between the chairside time used for single-visit and
multiple-visit non-surgical endodontic treatment. The primary outcome measured was
the success of endodontic treatment which is no clinical sign and symptom and no radiographic
radiolucency in the follow-up examination. Another outcome measured was the total
chairside time spent on completion of endodontic treatment by a single visit and multiple
visits. The secondary outcome measured was the prevalence of postoperative pain after
7 days and at the final evaluation (18 to 45 months after treatment) for the single-visit
and multiple-visit treatment.

Patient recruitment

The study was approved by the Institutional Review Board of the University of Hong
Kong/Hospital Authority Hong Kong West Cluster (HKU UW 09–303). The clinical trial
was registered in the Chinese Clinical Trial Registry of the World Health Organization
(ChiCTR-IOR-15006117). The clinical trial was 4 years. Patient recruitment was implemented
for the first 30 months so that the participants would be followed up for at least
18 months. Patients after who were generally healthy, required primary non-surgical
endodontic treatment and agreed to return for follow-up via the Health Service Dental
Clinic of the University of Hong Kong were invited to participate in the study. Furthermore,
the participating patients had no history of periodontitis, and the tooth that required
primary endodontic treatment was periodontally healthy. Teeth with pulpotomy were
not accepted, and at least half of the coronal structure had to be remaining. The
protocol of the study was explained to participants and consent was obtained. Patients
who had severe acute pulpitis with facial swelling or systemic infection, severe systemic
disease, increased stress on the temporomandibular joint musculature or increased
psychological stress were excluded from this study (Fig. 1).

Fig. 1. Flow chart of the clinical trial

Group assignment

The participating patients were randomly assigned by the receptionist for endodontic
treatment. The treated teeth were randomly assigned to either single-visit or multiple-visit
treatments using the random-number generating function of a calculator. If the patient
needed more than one endodontic treatment, the randomised allocation was performed
on every tooth required treatment. A number unknown to the operators and the independent
assessor was given to each treated tooth for clinical and radiographic assessment,
data entry and analysis.

Sample size calculation

For sample size calculation, it has been estimated the success rate of primary non-surgical
endodontic treatment was 88 % 12]. A difference in the success rate by at least 10 % between single-visit and multiple-visit
endodontic treatments was considered clinically significant and statistically achievable.
The estimated sample size was 102 for each treatment group based on the power of the
study set at 80 % (??=?0.20) and with ??=?0.05 as the significance level. We estimated
the dropout rate would be 20 %, and thus, at least 256 teeth with at least 128 teeth
per group were required at the baseline for analysis.

Clinical procedure

The two general dentists (A and B) carried out the endodontic treatments. One of them
(A) was trained to use a magnifying loupe (2.5x). The two dentists received a calibration
workshop prior to this clinical trial to standardise the instrumentation and obturation
technique described below. Preoperative periapcal radiographs using a parallel technique
were taken. Local anaesthetic was given and rubber dam was used for isolation. The
root canals were cleaned and shaped using Ni-Ti rotary files (ProTaper NiTi, Dentsply
Maillefer, Ballaigues, Switzerland). A 5.25 % sodium hypochlorite was used for irrigation.
The prepared tooth was obturated after shaping and cleaning of the canals if it was
in the single-visit group. For those teeth assigned to multiple-visit group, non-setting
5 % calcium hydroxide paste (UltraCal XS, Ultradent, South Jordan, UT, USA) was used
as inter-appointment medication. The tooth was temporarily restored with resin-modified
zinc oxide and eugenol cement (IRM, LD Caulk Dentsply, Milford, CT, USA) until obturation.
The next appointment was scheduled in following week. It could be two to three visits
depending on the complexity of the treatment. All teeth were obturated using a core-carrier
technique (Thermafil, Dentsply Maillefer, Ballaigues, Switzerland). The total chairside
time was recorded by the dental assistant. The treated teeth were restored with silver
amalgam or composite resin. Patients were recommended to take a dose of paracetamol
500 to 1000 mg every 4 to 6 h if needed. All patients were reviewed 1 week after obturation,
and were advised to have indirect extra-coronal restoration (partial or full veneer)
to avoid failure due to extra-coronal leakage or tooth fracture.

Evaluation

The patients were reviewed 1 week after obturation. The treated teeth were clinically
examined and reason for clinical failure, if any, was recorded. Clinical signs and
symptoms including pain, tenderness on percussion, caries (primary or secondary),
defective margin of restoration, mobility, periodontal pocket and soft tissue pathology
such as abscess or sinus tract were recorded. If the patient experienced pain or discomfort
of treated tooth after obturation, they were asked to rate their pain or discomfort
using a pain scale score table (Fig. 2). The pain assessment was adopted from our previous study which measured pain on
a 10-point Likert scale, ranging from no pain (score 0) to extreme pain (score 10)
16]. The patients were asked to attend regular follow-ups every 6 months after the endodontic
treatment. Periapical radiographs were taken using a parallel technique. The method
of radiographic assessment was adopted from Chu and his co-workers (2005) 12]. Signs of any internal or external root resorption were recorded and the periapical
conditions were classified as 1) normal—normal appearance of the surrounding osseous
structure or 2) apical periodontitis—apical radiolucency observed. Multiple-rooted
teeth with different periapical statuses at different roots were classified according
to the most severe periapical condition. When doubt existed as to whether pathological
periapical conditions were present or not, the case was classified as normal. The
method of radiographic assessment for the length and density of the root canal filling
were recorded for analysis 16]. The length of the root canal filling were recorded as 1) adequate – filling within
2 mm from radiographic apex, 2) overfilling – filling over radiographic apex or 3)
underfilling – filling at least 2 mm short from apex. The density of root canal filling
were recorded as 1) adequate – filling uniformly packed without visible voids and
canal spaces or 2) inadequate – filling with visible voids or canal spaces. The outcome
of the endodontic treatment was classified as a success or a failure. Success was
graded when there were no clinical signs/symptoms and no radiographic radiolucency
found in the periapical radiograph. The reason for the extraction, in particular for
those reasons related to endodontic failure, was recorded. To estimate the reliability
of the radiographic assessment, duplicated assessment were performed on around 15 %
the patients. The intra-observer agreement and inter-observer agreement for radiographic
assessments (complete healing or failure) were then calculated by Kappa statistics.

Fig. 2. Pain scale score table

Data analysis

The collected data was analysed with the IBM® SPSS® Statistics 21.0 program (IBM SPSS
Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.) by a statistician (SKYL).
The intra-observer agreement and inter-observer agreement for radiographic assessments
(complete healing or failure) were calculated by Kappa statistics. For the primary
treatment outcome (success or failure), multiple logistic regressions were used to
assess the relationship between the primary treatment outcome (success or failure)
and the treatment (single-visit or multiple-visit) groups, adjusting for other independent
variables. The independent variables included: patients’ gender and age, operators
(A or B), use of magnifying loupe, arch (maxillary or mandibular), tooth location
(anterior or posterior), number of canals of the endodontically treated tooth (single
or multiple), presence of preoperative apical radiolucency, presence of C-shaped canal
before treatment, presence of periodontal pocket before treatment (?4 mm pocket),
vitality before treatment, mobility before treatment, tooth status of the main opposing
tooth, tenderness on percussion before treatment, presence of sinus tract before treatment,
presence of pain and pain intensity (0 to 10) before and after treatment, length of
root canal filling (adequate, overfilling or underfilling), density of root canal
filling (adequate or inadequate) and type of postoperative restoration. All of the
independent variables were entered into the model. Backward stepwise procedures were
then performed until only variables demonstrating a statistically significant association
remained in the final model.

The prevalence of postoperative pain after 1 week and at least 18 months was the secondary
outcome evaluated in this study. Chi-square test or Fisher’s exact test was used to
compare the proportions between single-visit and multiple-visit groups. The level
of statistical significance of all tests was set at 5 %.

The chairside time required for endodontic treatment was the secondary outcome evaluated
in this study. Multi-way analysis of covariance (ANCOVA) was used to study the relationship
between chairside time and treatment visit group, with the independent variables factored
in. The independent variables included: patients’ gender and age, use of magnifying
loupe, arch (maxillary or mandibular), tooth location (anterior or posterior), number
of canals of the endodontically treated tooth (single or multiple), presence of preoperative
apical radiolucency, presence of C-shaped canal before treatment, presence of periodontal
pocket before treatment (?4 mm pocket), vitality before treatment, mobility before
treatment, tooth status of the main opposing tooth, tenderness on percussion before
treatment, presence of sinus tract before treatment, presence of pain and pain intensity
(0 to 10) before treatment. Backward stepwise procedures were used.