▪ Sample preparation:
1. The external root surfaces of the teeth will be cleaned with a curette to remove calculus and periodontal tissues, and then will be placed in 5.25% NaOCl for 30 minutes to remove soft tissue debris. The teeth will be stored in sterile saline till use.
2. Pre-operative radiographs will be taken from bucco-lingual and mesio-distal aspects to assess the presence of a single patent canal and the absence of internal resorption and confirm fulfilling eligibility criteria without any complexities or defects.
3. The teeth will be decoronated using a low-speed diamond saw under copious irrigation to obtain 16 mm uniform root lengths.
4. K-file size #10 will be inserted in the canal to check patency then working length will be adjusted using K-file #15 until showing from the apex and subtracting 1mm, so a standardized working length of 15 mm will be obtained.
5. The apices will be sealed by flowable composite Filtek Supreme and impeded in epoxy resin blocks to prevent extrusion of the irrigation solution and simulate in-vivo conditions.
6. The root canals will be instrumented with FKG Race EVO rotary files up to RE4 (0.40 tip size and 4% taper) then increase flaring with ( 0.35 tip size and 6% taper) according to the manufacturer’s specifications.
7. In all groups, the canals will be irrigated with 3 ml of freshly prepared 5.25 % sodium hypochlorite solution as an irrigation solution after each file using a 30-gauge max-i-Probe needle tips placed 1mm shorter from the working length.
8. Apical patency will be retained by using#10 K-file between each rotary file.
9-Final irrigation 5ml of distilled water then drying with paper points
10-Obturation is done using Single cone technique #40 6% master cone to less than the full working length by 1 mm after injecting bioceramic sealer into the canal…the excess core is sheared off with a hot instrument.
11-All specimens are stored at 37 in 100% humidity for 2 weeks to enable a complete set of the sealer
12-After 2 weeks the root filling are removed with FKG Race EVO 40/0.4 (FKG Dentaire SA, Switzerland) at constant speed of 600 rpm , torque = 1-1.5 as suggested by the manufacturer
-After full removal of gutta percha, If full WL isn't reached, small hand files (C-files, C+files) are used.
13-The specimens will be randomly divided into 2 groups according to the type of solution used as follows:
-Group A: Formic acid 10% used for removing bioceramic sealer.
-Group B: HCL 20% used for removing bioceramic sealer.
14-Solutions are applied using plastic syringes in volume of 5 ml and left for 5 minutes.
15-Then investigate whether bioceramic sealer is removed or not and amount of removal.
16- A cotton pellet will be placed at the canal opening before cutting of the grooves
to prevent entrance of any debris formed during sectioning.
17- Two longitudinal grooves will be prepared on the buccal and lingual surfaces with
a diamond disk, to facilitate splitting of the roots.
18- The roots will be split longitudinally for SEM observation. The coronal, middle, and apical thirds of the root canal will be examined individually in each specimen