More writing: mTORC1 promotes m6A mRNA methylation.

Cho et al. (2021) and Villa et al. (2021) demonstrate that mTORC1 stimulates m6A mRNA methylation via WTAP expression and SAM synthesis. Increased mRNA methylation in turn promotes cell growth by enhancing mRNA degradation or translation.

TORC1 phosphorylates and inhibits the ribosome preservation factor Stm1 to activate dormant ribosomes.

Target of rapamycin complex 1 (TORC1) promotes biogenesis and inhibits the degradation of ribosomes in response to nutrient availability. To ensure a basal supply of ribosomes, cells are known to preserve a small pool of dormant ribosomes under nutrient-limited conditions. However, the regulation of these dormant ribosomes is poorly characterized. Here, we show that upon inhibition of yeast TORC1 by rapamycin or nitrogen starvation, the ribosome preservation factor Stm1 mediates the formation of nontranslating, dormant 80S ribosomes. Furthermore, Stm1-bound 80S ribosomes are protected from proteasomal degradation. Upon nutrient replenishment, TORC1 directly phosphorylates and inhibits Stm1 to reactivate translation. Finally, we find that SERBP1, a mammalian ortholog of Stm1, is likewise required for the formation of dormant 80S ribosomes upon mTORC1 inhibition in mammalian cells. These data suggest that TORC1 regulates ribosomal dormancy in an evolutionarily conserved manner by directly targeting a ribosome preservation factor.

Ribosomal dormancy at the nexus of ribosome homeostasis and protein synthesis.

Dormancy or hibernation is a non-proliferative state of cells with low metabolic activity and gene expression. Dormant cells sequester ribosomes in a translationally inactive state, called dormant/hibernating ribosomes. These dormant ribosomes are important for the preservation of ribosomes and translation shut-off. While recent studies attempted to elucidate their modes of formation, the regulation and roles of the diverse dormant ribosomal populations are still largely understudied. The mechanistic details of the formation of dormant ribosomes in stress and especially their disassembly during recovery remain elusive. In this review, we discuss the roles of dormant ribosomes and their potential regulatory mechanisms. Furthermore, we highlight the paradigms that need to be answered in the field of ribosomal dormancy.

Physiological significance of the two isoforms of initiator tRNAs in Escherichia coli.

Escherichia coli possesses four initiator tRNA (i-tRNA) genes, three of which are present together as metZWV and the fourth one as metY. In E. coli B, all four genes (metZWV and metY) encode i-tRNAfMet1, in which the G at position 46 is modified to m7G46 by TrmB (m7G methyltransferase). However, in E. coli K, because of a single-nucleotide polymorphism, metY encodes a variant, i-tRNAfMet2, having an A in place of m7G46. We generated E. coli strains to explore the importance of this polymorphism in i-tRNAs. The strains were sustained either on metYA46 (metY of E. coli K origin encoding i-tRNAfMet2) or its derivative metYG46 (encoding i-tRNAfMet1) in single (chromosomal) or plasmid-borne copies. We show that the strains sustained on i-tRNAfMet1 have a growth fitness advantage over those sustained on i-tRNAfMet2. The growth fitness advantages are more pronounced for the strains sustained on i-tRNAfMet1 in nutrient-rich media than in nutrient-poor media. The growth fitness of the strains correlates well with the relative stabilities of the i-tRNAs in vivo. Furthermore, the atomistic molecular dynamics simulations support the higher stability of i-tRNAfMet1 than that of i-tRNAfMet2. The stability of i-tRNAfMet1 remains unaffected upon the deletion of TrmB. These studies highlight how metYG46 and metYA46 alleles might influence the growth fitness of E. coli under certain nutrient-limiting conditions. IMPORTANCE: Escherichia coli harbors four initiator tRNA (i-tRNA) genes: three of these at metZWV and the fourth one at metY loci. In E. coli B, all four genes encode i-tRNAfMet1. In E. coli K, because of a single-nucleotide polymorphism, metY encodes a variant, i-tRNAfMet2, having an A in place of G at position 46 of i-tRNA sequence in metY. We show that G46 confers stability to i-tRNAfMet1. The strains sustained on i-tRNAfMet1 have a growth fitness advantage over those sustained on i-tRNAfMet2. Strains harboring metYG46 (B mimic) or metYA46 (K mimic) show that while in the nutrient-rich media, the K mimic is outcompeted rapidly; in the nutrient-poor medium, the K mimic is outcompeted less rapidly.

Regulation of translation by one-carbon metabolism in bacteria and eukaryotic organelles.

Protein synthesis is an energetically costly cellular activity. It is therefore important that the process of mRNA translation remains in excellent synchrony with cellular metabolism and its energy reserves. Unregulated translation could lead to the production of incomplete, mistranslated, or misfolded proteins, squandering the energy needed for cellular sustenance and causing cytotoxicity. One-carbon metabolism (OCM), an integral part of cellular intermediary metabolism, produces a number of one-carbon unit intermediates (formyl, methylene, methenyl, methyl). These OCM intermediates are required for the production of amino acids such as methionine and other biomolecules such as purines, thymidylate, and redox regulators. In this review, we discuss how OCM impacts the translation apparatus (composed of ribosome, tRNA, mRNA, and translation factors) and regulates crucial steps in protein synthesis. More specifically, we address how the OCM metabolites regulate the fidelity and rate of translation initiation in bacteria and eukaryotic organelles such as mitochondria. Modulation of the fidelity of translation initiation by OCM opens new avenues to understand alternative translation mechanisms involved in stress tolerance and drug resistance.

Rapid formylation of the cellular initiator tRNA population makes a crucial contribution to its exclusive participation at the step of initiation.

Initiator tRNAs (i-tRNAs) possess highly conserved three consecutive GC base pairs (GC/GC/GC, 3GC pairs) in their anticodon stems. Additionally, in bacteria and eukaryotic organelles, the amino acid attached to i-tRNA is formylated by Fmt to facilitate its targeting to 30S ribosomes. Mutations in GC/GC/GC to UA/CG/AU in i-tRNACUA/3GC do not affect its formylation. However, the i-tRNACUA/3GC is non-functional in initiation. Here, we characterised an Escherichia coli strain possessing an amber mutation in its fmt gene (fmtam274), which affords initiation with i-tRNACUA/3GC. Replacement of fmt with fmtam274 in the parent strain results in production of truncated Fmt, accumulation of unformylated i-tRNA, and a slow growth phenotype. Introduction of i-tRNACUA/3GC into the fmtam274 strain restores accumulation of formylated i-tRNAs and rescues the growth defect of the strain. We show that i-tRNACUA/3GC causes a low level suppression of am274 in fmtam274. Low levels of cellular Fmt lead to compromised efficiency of formylation of i-tRNAs, which in turn results in distribution of the charged i-tRNAs between IF2 and EF-Tu allowing the plasmid borne i-tRNACUA/3GC to function at both the initiation and elongation steps. We show that a speedy formylation of i-tRNA population is crucial for its preferential binding (and preventing other tRNAs) into the P-site.

Two highly conserved features of bacterial initiator tRNAs license them to pass through distinct checkpoints in translation initiation.

Eubacterial translation initiation involves assembly of tRNAfMet, mRNA, initiation factors (IFs) and 30S ribosome in a 30S pre-initiation complex (30S pre-IC), which rearranges and joins 50S ribosome to form 70S IC. Upon releasing IFs, 70S IC becomes elongation-competent 70S. The direct recruitment of initiator tRNA (tRNAfMet) into the ribosomal P-site, crucial in accurate initiation of translation, is attributed to two conserved features of tRNAfMet: (i) formylation of amino acid attached to it and, (ii) the presence of three consecutive G-C base pairs (3GC base pairs) in the anticodon stem. However, the precise roles of these two conserved features of tRNAfMet during the various steps of initiation remain unclear. Using natural and engineered tRNAs, we show that the 3GC pairs license tRNAfMet transitions from 30S to 70S IC and then to elongation-competent 70S by release of IF3. Of the 3GC pairs, the middle GC pair (G30-C40), or merely G30 (in a specific context) suffices in this role and is essential for the sustenance of Escherichia coli. Furthermore, rescue of formylase deficient E. coli by overproduced tRNAfMet reveals that the feature of formylation licenses initial targeting of tRNAfMet to 30S ribosome

An evolutionarily conserved element in initiator tRNAs prompts ultimate steps in ribosome maturation.

Ribosome biogenesis, a complex multistep process, results in correct folding of rRNAs, incorporation of >50 ribosomal proteins, and their maturation. Deficiencies in ribosome biogenesis may result in varied faults in translation of mRNAs causing cellular toxicities and ribosomopathies in higher organisms. How cells ensure quality control in ribosome biogenesis for the fidelity of its complex function remains unclear. Using Escherichia coli, we show that initiator tRNA (i-tRNA), specifically the evolutionarily conserved three consecutive GC base pairs in its anticodon stem, play a crucial role in ribosome maturation. Deficiencies in cellular contents of i-tRNA confer cold sensitivity and result in accumulation of ribosomes with immature 3' and 5' ends of the 16S rRNA. Overexpression of i-tRNA in various strains rescues biogenesis defects. Participation of i-tRNA in the first round of initiation complex formation licenses the final steps of ribosome maturation by signaling RNases to trim the terminal extensions of immature 16S rRNA.

Platelet-Rich Plasma Has Better Long-Term Results Than Corticosteroids or Placebo for Chronic Plantar Fasciitis: Randomized Control Trial.

Plantar fasciitis is the most common cause of heel pain. Platelet-rich plasma (PRP) is a supersaturated concentration of autologous platelets that augments the natural healing response of fascia. Previous studies have shown the superiority of PRP over corticosteroids (CS) for chronic plantar fasciitis. The aim of this study was to compare the pain and functional outcomes of PRP with CS and placebo injections for the treatment of chronic plantar fasciitis. We conducted a 3-arm randomized controlled trial of 90 patients: PRP (n = 30 patients), CS (n = 30 patients), and placebo (n = 30 patients). The patients were followed at regular intervals until 18 months postinjection using validated instruments. The mean visual analog scale score showed significant improvement in all groups between baseline and 18-month follow-up (PRP: 8.2 vs 2.1; CS: 8.8 vs 3.6; placebo: 8.1 vs 5.4), with CS showing significantly better improvement than PRP in the short term, whereas longer-term PRP was significantly better than CS. The mean Roles and Maudley score showed significant improvement in all groups between baseline and 18-month follow-up (PRP: 1.7 vs 3.7; CS: 1.2 vs 3.1; placebo: 1.2 vs 2.0), with CS showing significantly better improvement than PRP in the short term, whereas longer-term PRP was significantly better than CS. The mean Short Form 12 score showed significant improvement in all groups between baseline and 18-month follow-up (PRP: 55.4 vs 80.2; CS: 56.2 vs 76.2; placebo: 54.1 vs 62.4). We found that all 3 groups showed significant improvement between baseline and end of the follow-up period with regard to pain, function, and general health. The CS arm showed better improvement in the short term, whereas the PRP arm showed better results in the long term. In contrast to previous studies, we found no significant drop-off effect of CS in the long term, which may be owing to background natural healing process of the disease. In summary, both PRP and CS are safe and effective treatment options for chronic plantar fasciitis, showing superior results to placebo treatment. The longer-term results and less reinjection and/or surgery rate of PRP makes it more attractive as an injection treatment option versus CS injection.

An extended Shine-Dalgarno sequence in mRNA functionally bypasses a vital defect in initiator tRNA.

Initiator tRNAs are special in their direct binding to the ribosomal P-site due to the hallmark occurrence of the three consecutive G-C base pairs (3GC pairs) in their anticodon stems. How the 3GC pairs function in this role, has remained unsolved. We show that mutations in either the mRNA or 16S rRNA leading to extended interaction between the Shine-Dalgarno (SD) and anti-SD sequences compensate for the vital need of the 3GC pairs in tRNA(fMet) for its function in Escherichia coli. In vivo, the 3GC mutant tRNA(fMet) occurred less abundantly in 70S ribosomes but normally on 30S subunits. However, the extended SD:anti-SD interaction increased its occurrence in 70S ribosomes. We propose that the 3GC pairs play a critical role in tRNA(fMet) retention in ribosome during the conformational changes that mark the transition of 30S preinitiation complex into elongation competent 70S complex. Furthermore, treating cells with kasugamycin, decreasing ribosome recycling factor (RRF) activity or increasing initiation factor 2 (IF2) levels enhanced initiation with the 3GC mutant tRNA(fMet), suggesting that the 70S mode of initiation is less dependent on the 3GC pairs in tRNA(fMet).

Is the cellular initiation of translation an exclusive property of the initiator tRNAs?

Translation of mRNAs is the primary function of the ribosomal machinery. Although cells allow for a certain level of translational errors/mistranslation (which may well be a strategic need), maintenance of the fidelity of translation is vital for the cellular function and fitness. The P-site bound initiator tRNA selects the start codon in an mRNA and specifies the reading frame. A direct P-site binding of the initiator tRNA is a function of its special structural features, ribosomal elements, and the initiation factors. A highly conserved feature of the 3 consecutive G:C base pairs (3 GC pairs) in the anticodon stem of the initiator tRNAs is vital in directing it to the P-site. Mutations in the 3 GC pairs diminish/abolish initiation under normal physiological conditions. Using molecular genetics approaches, we have identified conditions that allow initiation with the mutant tRNAs in Escherichia coli. During our studies, we have uncovered a novel phenomenon of in vivo initiation by elongator tRNAs. Here, we recapitulate how the cellular abundance of the initiator tRNA, and nucleoside modifications in rRNA are connected with the tRNA selection in the P-site. We then discuss our recent finding of how a conserved feature in the mRNA, the Shine-Dalgarno sequence, influences tRNA selection in the P-site.

Unconventional initiator tRNAs sustain Escherichia coli.

Of all tRNAs, initiator tRNA is unique in its ability to start protein synthesis by directly binding the ribosomal P-site. This ability is believed to derive from the almost universal presence of three consecutive G-C base (3G-C) pairs in the anticodon stem of initiator tRNA. Consistent with the hypothesis, a plasmid-borne initiator tRNA with one, two, or all 3G-C pairs mutated displays negligible initiation activity when tested in a WT Escherichia coli cell. Given this, the occurrence of unconventional initiator tRNAs lacking the 3G-C pairs, as in some species of Mycoplasma and Rhizobium, is puzzling. We resolve the puzzle by showing that the poor activity of unconventional initiator tRNAs in E. coli is because of competition from a large pool of the endogenous WT initiator tRNA (possessing the 3G-C pairs). We show that E. coli can be sustained on an initiator tRNA lacking the first and third G-C pairs; thereby reducing the 3G-C rule to a mere middle G-C requirement. Two general inferences following from our findings, that the activity of a mutant gene product may depend on its abundance in the cell relative to that of the WT, and that promiscuous initiation with elongator tRNAs has the potential to enhance phenotypic diversity without affecting genomic integrity, have been discussed.

Advances in Dynamization of Plate Fixation to Promote Natural Bone Healing.

The controlled dynamization of fractures can promote natural fracture healing by callus formation, while overly rigid fixation can suppress healing. The advent of locked plating technology enabled new strategies for the controlled dynamization of fractures, such as far cortical locking (FCL) screws or active plates with elastically suspended screw holes. However, these strategies did not allow for the use of non-locking screws, which are typically used to reduce bone fragments to the plate. This study documents the first in vivo study on the healing of ovine tibia osteotomies stabilized with an advanced active plate (AAP). This AAP allowed plate application using any combination of locking and non-locking screws to support a wide range of plate application techniques. At week 9 post-surgery, tibiae were harvested and tested in torsion to failure to assess the healing strength. The five tibiae stabilized with an AAP regained 54% of their native strength and failed by spiral fracture through a screw hole, which did not involve the healed osteotomy. In comparison, tibiae stabilized with a standard locking plate recovered 17% of their strength and sustained failure through the osteotomy. These results further support the stimulatory effect of controlled motion on fracture healing. As such, the controlled dynamization of locked plating constructs may hold the potential to reduce healing complications and may shorten the time to return to function. Integrating controlled dynamization into fracture plates that support a standard fixation technique may facilitate the clinical adoption of dynamic plating.

A Case Report of Giant Aneurysmal Bone Cyst of Distal Tibia with a Non-healing Fungating Mass and its Management in a 30-year-old Male.

Introduction: Aneurysmal bone cyst (ABC) is a benign, expansible, non-neoplastic tumor of usually long bones and is identified by blood vessels and spaces that are most often differentiated by fibrous septae. It is challenging to treat these rare, giant ABCs as they have a damaging effect on the bones and compress the nearby structures, especially in load-bearing bones of the body. Case Report: We report a case of a giant ABC in the distal tibia one-third with soft tissue component of a 30-year-old male. The patient presented to our outpatient department with complaints of pain and swelling over left ankle for 1 year. The size of the swelling was 15 cm × 10 cm × 10 cm over medial aspect of ankle with 3 discharging sinuses which present over swelling. His blood parameters were suggestive of low hemoglobin count. X-rays showed cystic lesions over medial aspect of left ankle. Computed tomography scan and magnetic resonance imaging reports were suggestive of ABC. Conclusion: Our case report is unique as it reminds us that when presented with a case of ABC, excision of fungating soft tissue with curettage followed by cementing can be a preferable and better treatment option. ABC was extensively curetted out, the formed cavity was packed with bone cement, and fixation with 3 cortico cancellous screws was carried out. At 4-month follow-up, the lesion had receded, and the patient was walking without pain and any deformity. We suggest that this method of treatment is beneficial for ABC at this site and at this age.

Diet-induced loss of adipose hexokinase 2 correlates with hyperglycemia.

Chronically high blood glucose (hyperglycemia) leads to diabetes and fatty liver disease. Obesity is a major risk factor for hyperglycemia, but the underlying mechanism is unknown. Here, we show that a high-fat diet (HFD) in mice causes early loss of expression of the glycolytic enzyme Hexokinase 2 (HK2) specifically in adipose tissue. Adipose-specific knockout of Hk2 reduced glucose disposal and lipogenesis and enhanced fatty acid release in adipose tissue. In a non-cell-autonomous manner, Hk2 knockout also promoted glucose production in liver. Furthermore, we observed reduced hexokinase activity in adipose tissue of obese and diabetic patients, and identified a loss-of-function mutation in the hk2 gene of naturally hyperglycemic Mexican cavefish. Mechanistically, HFD in mice led to loss of HK2 by inhibiting translation of Hk2 mRNA. Our findings identify adipose HK2 as a critical mediator of local and systemic glucose homeostasis, and suggest that obesity-induced loss of adipose HK2 is an evolutionarily conserved mechanism for the development of selective insulin resistance and thereby hyperglycemia.

Solid pseudopapillary epithelial neoplasm (SPEN) of the pancreas involving the distal body and proximal tail: A case report.

INTRODUCTION AND IMPORTANCE: Solid Pseudopapillary Epithelial Neoplasm (SPEN) of the pancreas is a rare cystic exocrine tumor of the pancreas most commonly occurring in women between 30 and 40 years of age. This case report aims to demonstrate the clinicopathological findings encountered and the management of a patient diagnosed with SPEN. CASE PRESENTATION: An 18-year-old woman with gradually progressive and intermittent abdominal pain in the epigastric region presented to our outpatient department. Physical examination elicited tenderness to palpation in the epigastric area, and imaging findings suggested SPEN of the pancreas involving distal body and proximal tail region of the pancreas. The tumor was resected, and the diagnosis was confirmed on histopathology examination. CLINICAL DISCUSSION: SPEN is a slow-growing tumor with a low-grade malignant potential, found incidentally in asymptomatic patients and symptomatic patients present with abdominal pain. The average tumor size is about 4 to 6 cm in diameter. Imaging is essential for diagnosis, and distal pancreatectomy with splenectomy was the most commonly reported procedure. CONCLUSION: It is crucial to consider a diagnosis of SPEN in women with abdominal pain in the epigastric region as early surgical resection of the tumor results in resolution and excellent prognosis.

A Novel technique of three-ring Ilizarov fixator frame in gap non-union of tibia.

INTRODUCTION: Gap non-union of tibia occurring mostly after trauma and many times complicated by infection, is a difficult problem to treat. The study aimed to assess the outcome of the three-ring construct of the Ilizarov fixator frame in the management of gap non-union of the tibia. METHODS: This retrospective study included 30 patients of gap non-union of tibia operated from April 2016 to March 2019 with a three-ring Ilizarov fixator frame and follow-up done till March 2021. The mean age was 39.27 (range 10-66) years. The results were assessed by the Association for the Study and Application of the Method of Ilizarov (ASAMI) criteria. MPTA, PPTA, and LDTA after removal of the frame were also measured. RESULTS: Out of the total 30 cases, all the patients showed complete union. The Ilizarov fixator was kept for an average period of 11.43 months and the mean defect size was 7.17 (range 2-12) cm. All patients were followed up for an average period of 39.36 (range 24-54) months. According to the ASAMI score bone/radiological results, 27 were classified as excellent, 2 as good, and 1 as poor. Functionally 28 were graded as excellent and the remainder as good. The normal ranges of MPTA, LDTA & PPTA were also achieved in a majority (80%) of patients. CONCLUSION: Our results after using only a three-ring Ilizarov fixator frame are almost equivalent to earlier studies and have advantages such as less weight, better patient compliance, superior radiographic visualization, easy mobilization, and reduced costs. Ilizarov ring fixator remains an excellent treatment modality for tibial non-union with a defect, regarding bone union, deformity correction, infection eradication, limb-length achievement, and limb function.

Familial Schwannomatosis: A Diagnostic Challenge.

Schwannomatosis is a disease characterized by the development of multiple benign tumours originating from Schwann cells. Schwannomatosis is a member of the family of diseases known as Neurofibromatosis (NF). Patients with Schwannomatosis develop multiple Schwannomas on cranial, spinal and peripheral nerves. We report a rare case of a 60-year-old female who presented with a painful swelling on the ulnar aspect of her distal forearm. She underwent an excisional biopsy for it; which was suggestive of a Schwannoma. Following ulnar swelling surgery, she developed acute low back pain, which was burning in nature with radiation along both lower limbs without any neurovascular deficit. She was treated conservatively, failing which an MRI was performed which suggested abnormal lesions in the intradural extra medullary compartment of the spinal canal. She had multiple swellings over the entire body with a positive family history of similar swellings in her sister and nephew. The painful lumbar swellings were excised which on histopathological examination revealed to be Schwannomas. No neurological deficit was observed postoperatively. There were no neurocutaneous markers, axillary freckling, visual or auditory disturbances seen in the patient or her relatives. Any patient with multiple painful progressive swellings in the body without the characteristic features of NF-1 and NF-2 should raise the suspicion of Schwannomatosis.

Optimal parameters to avoid thermal necrosis during bone drilling: A finite element analysis.

The drilling bone may potentially cause excessive frictional heat, which can lead to local bone necrosis. This heat generation and local necrosis has been suggested to contribute to the resorption of bone around the placed screws, ending in loss of screw purchase in the bone and inadvertent loosening and/or the bone-implant construct. In vivo studies on this subject have inherent obstacles not the least of which is controlling the variables and real time bone temperature data acquisition. Theoretical models can be generated using computer software and the inclusion of known constants for the mechanical properties of metal and bone. These known Data points for the variables (drill bit and bone) enables finite element analysis of various bone drilling scenarios. An elastic-plastic three-dimensional (3D) acetabular bone mode was developed and finite element model analysis (FEA) was applied to various simulated drilling procedures. The FEA results clearly indicate that the depth of drilling and the drill speed both have a significant effect on the temperature during drilling procedures. The reduction of the feeding speed leads to a reduction in bone temperature. Our data suggests that reducing the feeding speed regardless of RPMs and pressure applied could be a simple useful and effective way to reduce drilling temperatures. This study is the first step in helping any surgeon who drills bone and places screws to better understand the ideal pressure to apply and drill speed to employ and advance rate to avoid osteonecrosis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2386-2391, 2017.

An in vitro Comparative Evaluation of Three Remineralizing Agents using Confocal Microscopy.

INTRODUCTION: The caries process has been thought to be irreversible, resulting in the permanent loss of tooth substance and eventually the development of a cavity. Recent approaches focused on application of remineralizing agents to incipient carious lesions, aim at controlling demineralization and promoting remineralization. Remineralizing agents create a supersaturated environment around the lesion; thus, preventing mineral loss and forces calcium and phosphate ions in the vacant areas. AIM: To compare and evaluate the remineralization potential of Fluoride Varnish, CPP-ACP Paste (Casein Phosphopeptide-Amorphous Calcium Phosphate) and fTCP Paste (functionalized Tricalcium Phosphate) using confocal microscope. MATERIALS AND METHODS: Two windows of 3X3mm were created on the labial cervical and incisal thirds in 60 permanent maxillary central incisors. The teeth were demineralized to create artificial caries and divided into three groups of 20 each. Group I specimens were coated with Fluoride Varnish once whereas those in CPP-ACP paste group and fTCP group were brushed for 2 minutes, twice daily for 20 and 40 days. The specimens were stored in artificial saliva during the study period and were later sectioned and observed under confocal microscope. Data obtained was statistically analyzed using Fischer's exact test, ANOVA and post-hoc Bonferroni's test. RESULTS: Fluoride Varnish, CPP-ACP Paste and fTCP Paste showed remineralization of artificial carious lesions at both the time intervals. Fluoride varnish showed the highest remineralization followed by CPP-ACP Paste and fTCP Paste. A statistically significant increase in remineralization potential of CPP-ACP Paste and fTCP Paste was observed at the end of 40 days as compared to 20 days. CONCLUSION: Fluoride varnish showed the greatest remineralization potential of artificial carious lesions followed by CPP-ACP Paste and fTCP Paste respectively.