This randomized clinical study aims to assess the clinical and radiographic success rate of the 3Mixtatin versus the 3Mix in LSTR in necrotic primary molars.

Research question:

In necrotic primary molars with peri-radicular lesions and/or external root, resorption does adding Simvastatin to the triple antibiotic mix have higher clinical and radiographic success than the triple antibiotic paste solely?

Statement of the problem:

Primary teeth with necrotic pulp and extensive root resorption and/or furcal radiolucency are not uncommon scenarios that pediatric dentists are exposed to. Such clinical and radiographic presentations contraindicate the application of conventional pulpectomy treatment. Lesion Sterilization and Tissue Repair (LSTR) is an approach that has shown promising results in maintaining such teeth for up to 12 months. Primary teeth serve as a natural space maintainer, enable normal and healthy functioning of the child, and eliminate the chances for malocclusion and growth pattern disruptions. LSTR offers practitioners a promising option to save those teeth when all other treatment options seem impossible.

The Rationale for Conducting the Research:

In accordance to the popularity that LSTR has recently been gaining in the field of Pediatric dentistry, an abundance of studies have been conducted in the recent years. Researchers are striving to explore the plethora of possibilities and variances in the LSTR technique that could help clinicians practice better and achieve more for their patients. Amongst the alternatives is the recent and common detour towards regenerative dentistry.

Simvastatin, one of the materials, remains of high interest to the field due to its healing powers. However, to our knowledge insufficient studies are available on the direct comparison of the clinical and radiographic success including bone regeneration using the 3Mixtatin versus 3Mix alone. Furthermore, studies conducted warrant the need for further studies directly comparing 3Mixtatin with 3mix. Therefore, this study aims to come to a conclusion on whether the 3mix with the host's body defense and repair mechanism are sufficient to save a necrotic primary tooth or is some help in bone regeneration and healing promotion needed.

The LSTR technique involves non-instrumentation or minimal instrumentation followed by sterilization of the infected pulpal space by the placement of a triple antibiotic mixture in a propylene glycol vehicle to disinfect the microbial flora inhabiting the infected root canal systems and peri-apical lesions. The latter step achieves disinfection while tissue repair is then allowed to take place by the host's natural body defense mechanisms

The triple antibiotic paste (TAP/3mix), is an intracanal medicament that has continuously proven its efficacy and superiority for years against the microflora inhabiting necrotic canals predominantly Enterococcus Faecalis, the most prevalent organism in infected root canals. Metronidazole, ciprofloxacin, and minocycline, the oldest and most common combination suggested by Takushige et al., has been subjected to many studies and changes due to the discoloration caused by minocycline. As a result of, modified triple antibiotic paste (Modified-3mix) was introduced to replace minocycline with clindamycin.

Statins are antihyperlipidemic drugs, with a bio inductive feature that includes inhibition of bone resorption and promotion of osteoblast proliferation and differentiation as well as stimulating angiogenesis all of which aid in the healing process. In a clinical trial mixing modified 3mix with statins in, namely, Simvastatin; resulted in excellent clinical and radiographic success rates. Hence, modifying the LSTR technique to include regenerative materials such as statin is an extremely promising area of research.

Inclusion Criteria:

• Pediatric patients aged 4-7 years.
• Positive parental informed consent.
• Restorable necrotic mandibular second primary molars with peri-radicular/furcal involvement and/or pathologic root resorption (external or internal).
• Presence of chronic apical abscess or sinus tract or furcation radiolucency. (Thakur et al., 2021)

Exclusion Criteria:

• Medically compromised children.
• Children with known allergy to any of the components being utilized.
• Molars near exfoliation.
• Molars with severely resorbed roots more than two thirds indicated for extraction
• Molars with insufficient coronal structure disabling proper coronal seal.
• Presence of periapical or interradicular radiolucent area which could compromise the permanent tooth bud. (Shetty et al., 2020)

This research will be a double-blinded study, where the patient (participant) and the outcome assessor will be blinded to the treatment group (to avoid detection, reporting and assessment bias).

When a patient agrees to participate in the trial, an envelope will be drawn by one of the residents present at the clinic and name, telephone number and patient's I.D. will be written on it. Those selected envelops will be opened at treatment visit after performing access cavity to choose which material should be used. Randomization and allocation concealment will be performed by the co-supervisor to avoid selection bias. The participant will not be aware of which treatment modality he will be receiving.

Principal investigator will not be blinded due to differences in preparation of the mix.