Management of non-vital primary molars is challenging due to the natural anatomy of primary teeth, patients' young age, and their behavior toward dental treatment. A simple and effective technique such as Lesion Sterilization and Tissue Repair offers a solution to cases with poor prognosis; however, the medicaments used in this technique have some limitations. This study will evaluate three different medicaments regarding the clinical success, radiographic success, and antibacterial activity.

This randomized controlled trial will include 108 non-vital mandibular primary molars in children aged 4-8. Patients will be randomly allocated into three groups according to the studied medicaments as one positive control group and two experimental groups. The groups are as follows:

Group I (conventional double antibiotic paste) positive control group Group II (double antibiotic paste-loaded chitosan-coated silver nanoparticles) experimental group Group III (chitosan-coated silver nanoparticles) experimental group

The antibacterial activity of studied medicaments will be tested against Enterococcus Faecalis bacteria in planktonic and biofilm forms. Teeth will be evaluated clinically and radiographically to obtain baseline data. After local anesthesia administration and isolation of teeth, an access cavity will be performed, then the medicament will be placed over the floor of the pulp chamber according to the corresponding group. Afterwards, teeth will be filled with resin-modified zinc oxide and eugenol followed by stainless steel crowns. Blinded clinical evaluation will be done at baseline, 1, 6, and 12 months and blinded radiographic evaluation will be done at baseline, 6, and 12 months.

Inclusion Criteria:

• Healthy cooperative children of both sexes in the age range of 4-8 years old.
• Children with consenting parents who accept to participate in the study and sign the consent forms.
• Children with mandibular primary molars with clinical and radiographic signs of pulpal necrosis.

Exclusion Criteria:

• Children with hypersensitivity to any of the used medicaments.
• Non-restorable teeth without sufficient coronal structure for placement of rubber dam isolation and restoration with stainless steel crowns
• Non-restorable teeth with perforated pulpal floor

The current study will be a triple-blind study. The participants will be blind to the study groups they will be assigned to. The evaluators will also be blind to the study groups during clinical and radiographic examination. The operator will not be blind to the study groups because of the difference between the used medicaments. The statistician will be unaware of the study group's allocation during statistical analysis of the data collected.