Could the clinical and radiographic success of Nano Silver Particles and Calcium Hydroxide be comparable to that of Triple Antibiotic Paste as antibacterial agents for Lesion Sterilization and Tissue Repair (LSTR) in necrotic second primary molars?

The major aim of pediatric dentistry is to maintain the integrity of the primary dentition until physiologic exfoliation. Premature loss of primary teeth may lead to several complications, like disturbance in eruption sequence, ectopic eruption and space loss. Hence, the conservation of primary tooth structure is essential, provided that it can be restored to function and remain free from disease.Pulp therapy in primary teeth at times become contraindicated or compromised due to excessive root resorption, inadequate bone and periodontal support, a child with pre-cooperative age group, etc.

In the current era, a new perspective which is less invasive and less time consuming procedure could be a spark of hope for pedodontists. The Lesion Sterilization and Tissue Repair (LSTR) claims its significance in such clinical situation. The concept of LSTR was developed at the Cariology Research Unit of Niigata University School of Dentistry. The LSTR is an endodontic treatment procedure that involves non instrumentation or minimal instrumentation followed by placement of antibiotic mixture to disinfect root canal systems, and periapical lesions. The basic concept of LSTR is "do not remove or touch and leave it.". The principle behind LSTR is repair by natural defense mechanisms of host; Sterilizing the root canals and pulp chamber by medicaments can decrease the bacterial load. If the procedure is successful tissue repair can be expected.

However, because it is impossible to eradicate all microorganisms from the root canal system throughout the treatment, endodontic materials must contain specific components that release antibacterial substances. The most likely cause for this is the complex anatomy of the root canal system, which allows bacteria to colonize in inaccessible places to antimicrobial agents. Despite cleaning, and administration of highly effective antimicrobial agents, clinical trials have shown that bacteria remain within the root canal system because bacteria can form biofilms, infiltrate dentinal tubules, and cause monoinfection.

Among the intra canal medicaments, calcium hydroxide is most frequently used because of its wide antimicrobial spectrum. Calcium hydroxide Ca(OH)2 is commonly employed as an intra canal medicament. It releases hydroxyl ions which causes high alkalinity. Nevertheless, the ability of calcium hydroxide in elimination of bacteria from the root canal has been questioned. Antibacterial ability of calcium hydroxide in aqueous environment is linked to the discharge of hydroxyl ions. It can cause damage to the cytoplasmic membrane, bacterial DNA as well as can cause protein denaturation.

However, calcium hydroxide is not as much effective when used for canal disinfection having established Enterococcus faecalis (E.faecalis) biofilm. Recently, numerous studies have introduced silver nanoparticles as an antimicrobial agent. Silver nanoparticles have antimicrobial activity and are biocompatible, silver ions can cause damage to the bacterial cell wall. These are productive against many microorganisms including E.faecalis. Nanoparticles have /polyanionic polycationic properties with a high surface area and positive charge density, which increases their antibacterial activity. The particle size was also related to antimicrobial activity; the smaller particles give more bactericidal effects compared to larger particles. Calcium hydroxide do not always eradicate E.faecalis biofilm from root canals. Hence, it is essential to introduce advanced endodontic intra-canal medicament approaches that are successful in eradicating biofilm bacteria inside the root canals.

Inclusion Criteria:

• Children aged between 4 years and 7 years.
• Restorable necrotic mandibular second primary molars
• Mandibular lower second primary molar with signs of radiolucency in periapical or furcation area.
• Mandibular lower second primary molar with widening of PDL space or loss of lamina dura continuity.
• Mandibular lower second primary molar with evidence of internal/external pathologic root resorption.

Signs of radiolucency in periapical or furcation area.

• Widening of PDL space or loss of lamina dura continuity.
• Evidence of internal/external pathologic root resorption.
• External root resorption from 1% to 50%.

Exclusion Criteria:

• Children that are not apparently healthy.
• Lack of informed consent by the child patient's parent.
• Patients allergic to any antibiotic used in the preparation of the TAP.
• Unable to attend follow-up visits.
• Refusal of participation.
• External root resorption above 50%.