This clinical study was approved by the ethics committee of XXXXXX University (2015-KAEK-43-19-04). All patients read and signed an informed consent form with details about the study along with the benefits and risks of the therapy.
Sample size calculation
The sample size was calculated on the basis of the data obtained from a pilot study using G*Power 3.1 (Heinrich Heine University, Dusseldorf, Germany) software. The randomization method is mentioned later. The main research protocol was the same as that of the pilot study. The power calculation showed the least sample size for each group as 25 patients (power: 80%, significance level: 0.05). Because of the probability of dropouts during treatment or follow-up stage, 30 patients were involved for each group resulting 60 patients in total for the present study.
Patient selection and randomization
We examined 395 patients aged 18-65 years who were referred to the Endodontics Department. A total of 60 healthy patients who met inclusion criteria of this study were selected. Patients that had asymptomatic, single-rooted teeth with PAI score 3 or 4 were included in the present study. For diagnosis, both clinical and radiographic examinations were performed. Periapical status determined by examining panoramic radiographs (Sirona, Bensheim, Germany) first, following periapical radiographs (Dürr Dental, Bietigheim-Bissingen, Germany) taken by parallel technique by experienced radiology technicians. The exclusion criteria were antibiotic use with in the last month, anti-inflammatory analgesic use within the last five days, systemic disorder, pregnancy or lactation, traumatic occlusion, presence of other teeth requiring RCT, teeth with root canal fillings, calcified canals, root resorption, periodontal diseases, sinus tracts and severe crown destruction preventing rubber-dam application. A single operator performed all the endodontic treatment procedures over a period of 5 months. 60 patients divided into 2 separate groups according to the root canal disinfection procedure as control (no Laser) group and laser disinfection (LD) group (Fig. 1). To ensure randomization before starting the RCT, a dental student blinded to the research process allocated the patients by asking each one to select one of the envelopes with the group codes that were sealed before.
After local anesthetic (4% articaine with 1:100,000 epinephrine) application and rubber-dam placement, the operator removed all the former coronal restorations and present caries. After access cavity preparation, working lengths (WL) were determined electronically by Propex Pixi device (Dentsply Maillefer, Ballaigues, Switzerland) and confirmed by periapical radiographs. Root canals were prepared using ProTaper Next nickel-titanium (Ni-Ti) files with an X-Smart Plus Endo Motor (Dentsply Maillefer, Ballaigues, Switzerland) at a speed of 300 rpm and 2 N/cm according to manufacturer instructions up to the size of X4 (size 40, 0.06 taper). The root canals were irrigated during preparation with 2 ml 2.5% NaOCl using a 30-gauge, side-opening needle (Canal Clean, Biodent, South Korea) positioned 3 mm short of WL.
Control (no laser) group
The final irrigation was performed using 5ml 2.5% NaOCI, followed by 5 ml 17% EDTA for 3 min and 5 ml distilled water. Afterwards, canals were dried with paper points, and calcium hydroxide (Ca(OH)2) paste (Calsin, Karabağlar, İzmir, Turkey) was applied as intracanal medicament. Subsequently, a temporary restorative material (Cavit-G; 3M ESPE, St Paul, MN) was used to seal the access cavity. The second appointment was scheduled for 1 week later.
At the second appointment, Ca(OH)2 was removed from root canals with final irrigation and using X4 file. Afterwards, root canals were obturated by lateral condensation method with gutta-percha cones and AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). Coronal restoration was finished using a resin composite (3M ESPE). Patients were called at scheduled times by the operator and asked about PP levels and analgesic intake.
Laser disinfection (LD) group
The final irrigation was performed as in the control group and canals were dried with paper-points. Subsequently, laser irradiation was applied using Medency Primo diode laser device (Medency, Vicenza, Italy). Root canals were irradiated with 980 nm diode laser coupled with optical fiber 200 µm with setting at the average power 1.2-W in pulsed mode. 10 seconds irradiation followed by 10 seconds pause, which comprised one lasting cycle. This cycle was applied 4 times for each root canal. The optical fiber (Medency) was inserted 1 mm short of the apex and the root canals were slowly (at a speed of 2mm/s) irradiated from apical to coronal in continuous circling movements to treat all dentinal tubules in one cycle for each power. Following disinfection procedure, Ca(OH)2 paste was applied as intracanal medicament and the access cavity was sealed with a temporary restorative material, as in the control group. VAS scale form was given to patients and the second appointment was scheduled.
In the second appointment, root canals were dried after Ca(OH)2 removal as in the control group. Afterwards, laser irradiation was performed as in the first appointment. The dentist and patients wore protective glass during laser applications. Subsequently, root canals were filled and resin composite was used as permanent restoration as in the control group. At scheduled times, patients were called for obtaining information about PP and it was recorded on the VAS scale form by the operator.
A home questionnaire form was given to patients for assessment of pain perception (VAS scale) and dedication of frequency of analgesic use after the first visit. None of the patients were prescribed with medications immediately after the RCT. The questionnaire was filled by patients at 8 h, 24 h and 48 h and 7 days post-operatively. The pain level was categorized as none (0), mild (1-3), moderate (4-7), and severe (8-10). Patients were also advised to take 600 mg ibuprofen every 6 h for pain alleviation, if they felt severe pain at any point of the follow-up time and the time intervals to take medications were registered by patients. In addition, age and gender were documented.
All statistical analyses were performed using SPSS version of 22 software (IBM SPSS, Turkey) and statistical differences were set at p<0.05. The Mann-Whitney U test was used for comparison of values at the different time points between the groups, while the Wilcoxon sign test was used for within-group comparisons among the different time points. Student t test was used to evaluate the age and gender distribution in the groups. For statistical analysis of differences in analgesic use, Fischer’s exact chi-square test was applied.