Modulation of Periapical Inflammation Following Nano-sized Intracanal Medication. A Randomized Controlled Clinical Trial

Sixty-three patients will be divided randomly into three groups (21 patients in each group) using simple randomization procedure using random number generator. https://www.random.org/ based on intracanal medicament used. Sequentially numbered opaque sealed envelopes prepared in advance by an independent researcher will be used to prevent prediction of group assignment.

After application of local anesthesia (4% articaine with 1:100,000 epinephrine) and rubber dam isolation, the crown surfaces will be swabbed using 3% hydrogen peroxide, 5.25% sodium hypochlorite and 5% sodium thiosulphate before and after endodontic access. Gutta percha removal will be performed, the working length will be determined using an electronic apex locator (EAL) and will be confirmed using periapical radiograph, then the pre-instrumentation periapical samples (S1) will be gathered with a sterile #15 paper point. Root canal preparation will be performed using ProTaper Next nickel-titanium rotary system (Dentsply, Maillfer, Switzerland) driven by EndoEst motor mini (Geosoft Dent., Russia) endomotor till size X5 (50.05) file in continuous rotation at 300 rpm and 2 Ncm. After each file use, the root canal will be irrigated with 5ml of freshly prepared 2.5% sodium hypochlorite (NaOCl) solution (Alex. Deteregents and Chemical Co., Egypt) for 1 minute using a 31-gauge Navi-Tip flexible irrigating needle (Navi-Tip, Ultradent product, South Jourdan, UT). 5 ml of 17% EDTA (Colgate Oral Care Company, Waverly, Australia) for 1 min will be used for smear layer removal following saline separation. 5 ml of saline solution will be used for final irrigation of the root canal to neutralize all the previously used irrigants and post-instrumentation samples (S2) will be taken using #40 paper points.

Subsequently, three groups will be formed according to the predetermined group numbers based on intracanal medicament used. Group I: Nanochitosan paste (Nanogate company, Cairo, Egypt), Group II: Nano-calcium hydroxide paste (Nanogate company, Cairo, Egypt), Group III: Calcium hydroxide paste (MetaBiomed, Chungcheongbuk-do, Korea) in its regular form. Intracanal medicament will be placed in the canal, 1 mm shorter than the working length using the applicator tip and left for 1 week. The access cavity will be temporarily sealed with light cure glass ionomer resin cement. After 1 week, the temporary filling will be removed following local anaesthesia and isolation, the root canal will be irrigated with 20 ml saline and gently filed using H file corresponding to the master apical file size. The last sample (S3) will be collected using #40 paper points. During sampling, each paper point will be introduced into the canal 2 mm beyond the working length for 1 min. The root canals will be flushed with phosphate buffered saline (PBS) solution when blood or purulent discharge is detected or if the canal is dry and sampling will be repeated. The samples will be transferred in a sterile tube and stored at -80°C until processing(24).

The operator will be informed of the assigned group only immediately prior to medicament application. It will follow triple-blind design, in which the patient, outcome assessor and statistician are blinded to group allocation.

Finally, the root canal system will be obturated using ADSEAL resin-based sealer (Meta Biomed Co, Cheongju, Korea) and gutta-percha (Protaper next; Dentsply Maillefer, Switzerland) with cold lateral condensation method after being completely dried using paper points of comparable size to the master cone. A final coronal restoration with direct composite filling (Filtek Bulk Fill,3M ESPE, USA) will be performed in the same visit.

Potential harms include:

• Mild postoperative pain or discomfort
• Irritant reaction to irrigants or medicaments
• Temporary inflammation flare-up

Risk minimizing measures:

• Strict rubber dam isolation
• Standardized irrigation protocols
• Analgesic and antibiotic prescription if needed

An interim analysis will be conducted after 50% recruitment. The trial will be stopped early if:

• Severe adverse events exceed 10% in any group Statistically significant superiority or harm is detected

A data safety monitoring committee composed of an independent endodontist, pathologist, will oversee safety.

Adverse events will be documented at each visit and reported to the ethics committee within 48 hours for serious events.

Participants will be withdrawn in case of development of acute infection requiring antibiotics, severe pain requiring analgesics, failure to attend follow up appointment and protocol violation affecting outcome validity.