Introduction
Management of infected primary teeth in pediatric patients presents a unique challenge due to anatomical, behavioral, and physiological considerations. Conventional endodontic procedures such as pulpectomy require mechanical instrumentation, which may be difficult in uncooperative children and in teeth with complex root canal morphology. In this context, Lesion Sterilization and Tissue Repair (LSTR) therapy has emerged as a minimally invasive, biologically based treatment modality.
LSTR is grounded in the principle that elimination of pathogenic microorganisms from the lesion can promote natural healing and tissue regeneration without extensive mechanical debridement. Introduced by the Cariology Research Unit at Niigata University School of Dentistry, Japan, LSTR has gained popularity in pediatric dentistry due to its simplicity, effectiveness, and reduced chairside time.
Concept and Biological Basis of LSTR
The fundamental concept of LSTR revolves around sterilizing infected dentinal, pulpal, and periapical tissues using a combination of antibacterial agents, thereby enabling the host’s natural defense mechanisms to repair damaged tissues. Unlike traditional root canal therapy, which focuses on mechanical removal of infected pulp tissue, LSTR emphasizes chemical disinfection.
The rationale behind this technique lies in the understanding that bacteria is the primary etiological factor in pulpal and periapical diseases. By eliminating bacterial load, inflammation subsides, and healing processes such as bone regeneration and revascularization can occur.
Indications of LSTR in Pediatric Dentistry
LSTR is particularly indicated in cases where conventional endodontic procedures are impractical or contraindicated. These include:
Primary teeth with necrotic pulp
Teeth with periradicular or interradicular radiolucencies
Uncooperative pediatric patients
Teeth with extensive root resorption where instrumentation is difficult
Medically compromised children where shorter treatment duration is preferred
Non-vital primary molars with sinus tract formation
Contraindications
Despite its advantages, LSTR is not universally applicable. Contraindications include:
Teeth with advanced root resorption nearing exfoliation
Presence of systemic infection requiring systemic antibiotics
Allergy to any of the antibiotic components
Teeth with non-restorable crowns
Cases where adequate isolation cannot be achieved
Composition of Triple Antibiotic Paste (TAP)
The cornerstone of LSTR therapy is the use of Triple Antibiotic Paste (TAP), typically consisting of
Metronidazole – effective against obligate anaerobes.
Ciprofloxacin – broad-spectrum antibiotic targeting gram-negative bacteria,
Minocycline – effective against gram-positive and gram-negative organisms.
These antibiotics are mixed in equal proportions and combined with a suitable vehicle such as propylene glycol or macrogol to form a paste that can be easily delivered into the cavity.
Mechanism of Action-
Mechanism of LSTR
The success of LSTR lies in the synergistic antibacterial effect of the antibiotic combination. Metronidazole targets anaerobic bacteria, which are predominant in necrotic pulps, while ciprofloxacin and minocycline broaden the antimicrobial spectrum.Once bacterial elimination is achieved, the inflammatory process subsides, allowing host immune responses to initiate tissue repair, including regeneration of periapical bone and resolution of radiolucency. In some cases, evidence of revascularization and continued root development has been reported.
Preparation of TAP
To prepare the paste, commercially available antibiotics are placed in separate dappen dishes. The enteric coating of tablets is removed by scraping with a blade, while the outer capsular material is taken off capsules. Each component is then ground separately using a clean mortar and pestle, ensuring that the powder remains dry. If the powder needs to be stored at this stage, it should be placed in tightly sealed porcelain containers, kept in a dark place or a refrigerator to avoid exposure to light and moisture.
After proper pulverization, the powdered components are combined on a clean glass slab or mixing pad. A part of the solvent is then added. For optimal effectiveness, the triple antibiotic mixture is typically prepared with a ratio of seven parts of the powdered antibiotics to one part of the solvent.
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