In silico exploration of enzymes involved in sialic acid biosynthesis and their possible role in SARS-CoV-2 infection.

Salivary glands are considered important targets of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Recent evidence suggests that along with angiotensin converting enzyme 2, certain cell surface sialic acids (Sia) may function as receptors for binding SARS-CoV-2 spike protein. Over 50 forms of Sia have been identified in nature, with N-acetylneuraminic acid (Neu5Ac) being the most abundant. We explored the Human Protein Atlas repository to analyze important enzymes in Neu5Ac biosynthesis and propose a hypothesis that further highlights the significance of salivary glands in coronavirus disease 19 (COVID-19). This work may facilitate research into targeted drug therapies for COVID-19.

Influence of Lignocaine Hydrochloride with Adrenaline on Free Active Chlorine Content of Sodium Hypochlorite Solution Admixed in Various Proportions.

OBJECTIVE: Local anaesthetic solution that is commonly employed for supplemental intrapulpal injection (IPI) may routinely come in contact with subsequently used sodium hypochlorite (NaOCl) during endodontic treatment of symptomatic irreversible pulpitis cases. This in vitro study investigated the available free active chlorine (FAC) content of 3% NaOCl after mixing with 2% lignocaine hydrochloride with adrenaline (LA) solution in three different proportions using iodometric titration analysis. METHODS: Aliquots of 3% NaOCl (control) in different measures (30 mL, 27 mL, 21 mL and 15 mL) served as the effective concentrate of various proportions of NaOCl admixed with the test solutions, i.e., demineralised water (DM) and LA. The mixed aliquots containing NaOCl-DM and NaOCl-LA combination solutions admixed in various proportions (9: 1, 7: 3 and 1: 1 w/v) respectively served as the experimental groups. Iodometric titration was performed to determine the FAC of each independent solution.The results were then evaluated using one-way ANOVA and Tukey's post hoc analysis to determine the differences between various groups and amongst the individual admixtures. The level of significance was set at P<0.05. RESULTS: Inter-group comparisons revealed statistically significant differences (P<0.05) between all the test groups. An intra-group analysis revealed significant differences (P<0.05) in group 2, whereas no differences (P>0.05) were observed in group 3. Further, there was a dose dependent reduction in FAC content in both the experimental groups with lowest FAC values were observed in 1: 1 solution admixtures followed by 7: 3 and 9: 1 proportions. CONCLUSION: There was a significant reduction in NaOCl FAC content when admixed with lignocaine HCl even in small proportions. Hence, adequate measures should be taken to remove the residual LA from the pulpal space, before the use of NaOCl after IPI administration.

In vitro assessment of interaction between lidocaine hydrochloride and sodium hypochlorite on root canal dentin before and after chemomechanical instrumentation procedures.

INTRODUCTION: To investigate the effect of resultant precipitate formed on interaction between 2% lidocaine hydrochloride with adrenaline (LA) and 2.5% sodium hypochlorite (NaOCl) on root canal dentin before and after chemomechanical preparation, using scanning electron microscopy (SEM). METHODS: Sixty mandibular premolars were decoronated, and the root length was standardized. All specimens were randomly distributed into the following three groups: Group I (control): 2% LA mixed with sterile water without root canal instrumentation, Group II: 2% LA with 2.5% NaOCl and no instrumentation, and Group III: 2% LA with 2.5% NaOCl, followed by mechanical instrumentation with rotary files. Teeth samples were sectioned into three parts, split and SEM analysis of the root canal wall was done at cervical, middle, and apical root thirds. RESULTS: SEM images revealed patent dentinal tubules with no precipitate occlusion in the control group, whereas there was occlusion of dentinal tubules with a precipitate in all the specimens in Group II and Group III at all the three root levels studied. CONCLUSIONS: The precipitate formed on the interaction between 2% LA solution and 2.5% NaOCl tends to occlude the dentinal tubules at the coronal, middle, and apical root thirds. The chemomechanical rotary instrumentation procedure did not effectively remove the precipitate from all the three levels of the root specimens studied. LA/sterile water group did not result in any precipitate formation on root canal dentin.

Cyclic fatigue resistance of RaCe and Mtwo rotary files in continuous rotation and reciprocating motion.

INTRODUCTION: The purpose of this study was to evaluate and compare the cyclic fatigue resistance of RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) and Mtwo (VDW, Munich, Germany) rotary files in continuous rotation and reciprocating motion. METHODS: A total of 60 new rotary Mtwo and RaCe files (ISO size = 25, taper = 0.06, length = 25 mm) were selected and randomly divided into 4 groups (n = 15 each): Mtc (Mtwo NiTi files in continuous rotation), Rc (RaCe NiTi files in continuous rotation), Mtr (Mtwo NiTi files in reciprocating motion), and Rr (RaCe NiTi files in reciprocating motion). A cyclic fatigue testing device was fabricated with a 60° angle of curvature and a 5-mm radius. All instruments were rotated or reciprocated until fracture occurred. The time taken for each instrument to fracture and the length of the broken fragments were recorded. All the fractured files were analyzed under a scanning electron microscope to detect the mode of fracture. The Kolmogorov-Smirnov test was used to assess the normality of samples distribution, and statistical analysis was performed using the independent sample t test. RESULTS: The time taken for the instruments of the Mtr and Rr groups to fail under cyclic loading was significantly longer compared with the Mtc and Rc groups (P < .001). Scanning electron microscopic observations showed that the instruments of all groups had undergone a ductile mode of fracture. The length of the fractured segments was between 5 and 6 mm, which was not statistically significant among the experimental groups. CONCLUSIONS: Mtwo and RaCe rotary instruments showed a significantly higher cyclic fatigue resistance in reciprocating motion compared with continuous rotation motion.