One hundred extracted single-rooted teeth were used in this study (National Research Centre project; Ethics Committee approval number 16/344).
Each tooth was radiographed to confirm the presence of a single canal. Teeth with previous root caries, cracks, curved canals, endodontic treatment, internal resorption, or calcification were excluded. After removal of calculus and soft-tissue debris, the teeth were placed in 2.5% sodium hypochlorite for 1 h to allow for surface disinfection and then stored in saline solution until instrumentation.
The teeth length was standardized to a length of 16 mm. Teeth decoration was done using a safe-sided diamond disk mounted in a low-speed handpiece under a water coolant. The working length was measured by subtracting 1 mm from the length recorded when the tip of a # 15 K file (Dentsply Maillefer, Switzerland) was visible at the apical foramen. Root canal preparation was done using Protaper (Dentsply, Maillefer) universal nickel titanium rotary system driven by x-smart endomotor (Dentsply, Maillefer) till size F5 file.
Teeth were divided into 5 groups (n = 20) according to the irrigant used, as follows: group 1, saline; group 2, M. oleifera (extracts were obtained from the Egyptian Scientific Society of the moringa trees, National Research Centre, Dokki, Giza, Egypt); group 3, M. oleifera in addition to chlorhexidine (CHX); group 4, chlorhexidine; and group 5, sodium hypochlorite.
Irrigation was done by 3 milliliters (ml) of irrigant solution according to each group after each file size. A final rinse was performed with 3 ml distilled water.
Fifty teeth were used for this part. Teeth were sectioned into two halves using a carborundum disk to create a longitudinal groove on the buccal and lingual surfaces. The teeth were then split using a chisel and mallet. Teeth from each group were rinsed thoroughly with saline and mounted on acrylic cylinders with self-cure acrylic resin with the root canal facing up. The specimens’ surfaces were finished using a silicon carbide paper in the following order: 400, 800, and 1200 grit. The microhardness measurements were done using a Vickers Diamond Microhardness Tester (Nexus 4000/60, INNOVATEST, Netherlands, Europe) in Vickers hardness units (VHN). At each root third, the microhardness measurements were taken at three different points at a depth of 500 μm from the lumen. Each measurement was carried out by using a 300 g load for 15 s dwell time.
Canal cleanliness and smear layer removal
Fifty teeth were used for this part of the study. Each tooth was divided into equal sections of coronal third, middle third, and apical third with a diamond disk. Each slice was marked as coronal, middle, and apical to identify its site. Images of each third of the canal were taken using a Canon digital camera with magnification × 25 connected to a Zeiss stereomicroscope (Technival 2). The captured images were analyzed using ImageJ software (ImageJ 1.47 V, National Institute of Health, USA). The percentage of debris on the entire surface area was analyzed in relation to the whole area of each one third of the canal (Fig. 3).
The samples were then 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.). Samples were examined with magnification × 50,000 and × 100,000.
The mean and standard deviation values were calculated for each group in each test. Data were explored for normality using Kolmogorov-Smirnov and Shapiro-Wilk tests; the data showed parametric (normal) distribution.
Repeated measures ANOVA was used to compare between more than two groups in related samples. Paired-wise sample t test was used to compare between two groups in related samples. One-way ANOVA followed by Tukey post hoc test was used to compare between more than two groups in non-related samples.
The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM® SPSS® Statistics Version 20 for Windows.