The study was approved by the College of Dentistry Research Centre (CDRC), King Saud University, Riyadh, Saudi Arabia. Fifty extracted human single-rooted teeth were used in this study. The inclusion criteria were single-rooted mandibular premolar teeth with one root canal and one apical foramen. Teeth were then x-rayed buccolingually and mesiodistally to assess the patency of the root canal. The following were criteria for inclusion: non-carious teeth, completely formed apices, non-calcified canals, and canal curvature less than 20 degrees, which were determined according to Schneider’s method
. The root end was inspected under magnification (X 20) to verify closed apices and the absence of root resorption or visible cracks.
The root surfaces were cleaned of debris using a sharp scalpel. The teeth were radiographed from bucco-lingual and mesio-distal views to ensure they had single canals and orifices. The teeth were then stored in saline. A standard endodontic access cavity preparation was made into a pulp chamber using a carbide bur. The occlusal surfaces of the crowns were then flattened to achieve a standardized reference point to determine the working length. The working length (WL) was determined by inserting a K-file size #15, which was observed to extend beyond the apical foramen and then subtracting 1 mm from the length of the file.
The teeth were then randomly divided into three experimental groups according to the irrigation technique used and one control group for the cleanliness evaluation. Random allocation was done using lottery method.
Group 1 (n = 15), irrigation was performed using the Endovac irrigation system (Discus Dental, Culver City, CA).
Group 2 (n = 15), irrigation was performed using a 30-gauge, tip-vented irrigation needle (NaviTips, Ultradent, South Jordan, UT).
Group 3 (n = 15), irrigation was performed using a 30-gauge, side-vented irrigation needle (Maxi-i-probe, Dentsply, Rinn, Elgin, IL).
The control group (n = 5) received instrumentation, with no irrigation serving as a control for cleaning efficiency.
The outer surface of the roots was then coated with two layers of nail polish (except the apical 2 mm of the root) to control the transport of the irrigation solution via any lateral canals. The teeth were then mounted in a cylinder-shaped stone with a 10-mm diameter. The top end of the stone was levelled with the cemento-dentinal junction (CDJ), while the bottom end fell 2 mm short of the apical tip of the root. The whole assembly was then seated on a copper mould with the same diameter as the stone, where the exposed apical part of the root was contained within a 3-mm hole to collect the extruded irrigation solution. The interface between the stone and the copper mould was sealed with wax at the sides and with cellophane at the base, exposing only the hole that collected the extruded irrigation solution. All of the procedures were performed by one operator.
Instrumentation in all of the experimental and control groups was initiated using size 4, 3 and 2 Gates Glidden drills (Dentsply Maillefer, Ballaigues, Switzerland) for coronal enlargement. Hand instrumentation using a size #15 K-file was performed to the full WL. ProFile® rotary NiTi files (Maillefer Dentsply, Ballaigues, Switzerland) were used with a crown-down instrumentation technique. A controlled slow-speed, high-torque motor with a continuous speed of 300 rpm was used for the rotary files. ProFile® rotary files with a 0.06 taper were used starting with size 40, 35, 30, and 25, reaching an apical preparation of size #40. Lastly, hand instrumentation with size a #40 K-file was performed. The canal patency maintained using a size #10 K-file that was longer than 1 mm beyond the WL, was used after a profile size 25/0.06.
Irrigation in group 1 was performed using the EndoVac irrigation system, and the technique used was according to the manufacturer’s instructions. Irrigation was started using the Master Delivery Tip (MDT) at the access site and dispensing 1 ml of NaOCl each time after using a size 4, 3, and 2 Gates Glidden. The macrocannula was then used and placed inside the canal to approximately 3–4 mm from the WL to dispense the same amount (1 ml) of NaOCl after each endodontic file. At the same time, the master delivery tip was placed at the access site to continue irrigating. Again, 1 ml of NaOCl was delivered after each endodontic file. Each canal was cleaned and irrigated simultaneously for 30 seconds. Then, the master delivery tip was removed quickly approximately 1 second after removing the macrocannula to leave the canals charged with fresh irrigant. Lastly, the MDT was returned to continue irrigating at the access site, while placing the microcannula inside the canal 2 mm from the WL for 6 seconds. The microcannula was then moved down to the WL and held in position for 6 seconds. This process was repeated for a total of 3 cycles per canal, delivering 1 ml of NaOCl each time.
Irrigation in groups 2 and 3 was performed using tip-vented and side-vented irrigation needles, respectively. Both types of needles were first adapted for a disposable plastic syringe. Irrigation was started after using the Gates Glidden and then after all of the endodontic files by dispensing 1 ml of NaOCl solution each time. The needle was inserted as far as possible into the root canal with an up and down movement, up to 2 mm from the WL, without binding to the canal walls. The time of irrigation was constant for all of the canals, 30 seconds for each 1 ml dispensed.
All the experimental teeth received the same amount of 5.25% NaOCl irrigation with a total amount of 12 ml of NaOCl.
Apical extrusion evaluation
The copper moulds were weighed before seating the moulded teeth on them using an electronic balance (Precisa 180A - Swiss made) to the fourth decimal. This value was then compared to the post-instrumentation weight of the moulds after removing the moulded teeth. The amount of extruded irrigating solution was then measured by subtracting the post-instrumentation weight from the pre-instrumentation weight.
The method for the cleanliness evaluation was a modified version of Al-Hadlaq et al.
. The teeth were removed from the stones and sectioned into two halves using a carborundum disk to create the longitudinal grooves on the buccal and lingual surfaces without entering the canals. The teeth were then split using a chisel and mallet. The most visible part of the canal was taken and divided into three main parts (coronal, middle, and apical) by creating three horizontal grooves and using a tapered carbide bur perpendicular to the canal. The samples were air-dried, sputter-coated with gold using a fine-coat ion sputter JFC-1100 (Fine coat ion sputter JFC-1100, JEOL Ltd., Tokyo, Japan), and then evaluated using Scanning Electron Microscope (SEM) (Jeol JSM-6360 LV, JEOL Ltd.). These three main parts were magnified up to X 20 magnification using SEM. Four random areas of each third were selected and magnified up to X 200 and then averaged to observe the debris layer removal from the canal walls. The captured images were analysed using ImageJ software (ImageJ 1.47 V, National Institute of Health, USA). The percentage of debris on the entire surface area was measured using the software to analyze the particles.
Statistical analysis was performed using the SPSS software package (Version 16, SPSS Inc., Chicago, Illinois, USA). The descriptive analysis for the sample, mean values, range and standard deviation were calculated. An apical extrusion evaluation of the three different irrigating techniques was performed using the t-test and a one-way ANOVA. A cleanliness evaluation of the three different irrigating techniques was compared using a one-way ANOVA. A post-hoc Tukey analysis and repeated measure test were used for multiple comparisons. The level of statistical significance was set at P < 0.05.