statement of problem: tooth-coloured restorative materials are brittle with the major shortcomings of sensitivity to flaws and defects. although various mechanical properties of resin composites have been studied, no fracture toughness test data for nano-hybrid composites under acidic condition for a long period of time has been published. objectives: to compare the fracture toughness (k ic ) o...

morphological, cultural, physiological and biochemical characteristics were employed to identify lactic acid bacteria (lab), isolated from drinking yoghurt in different areas in fars province, iran. from 18 drinking yoghurt samples a total of 673 lab positives were determined, in which 117 (17.38%) and 556 (82.62%) were identified as lactic acid cocci and lactic acid bacilli, respectively. addi...

  Objective: This study aimed to assess the destructive effects of citric acid, lactic acid and acetic acid produced from the fermentation of foods on primary teeth enamel.   Methods: This in vitro, experimental study was conducted on 24 sound primary teeth. The teeth were polished with a fine abrasive paper under running water. Tooth pieces measuring 3 × 4 × 3mm were cut out of the teeth and s...

The degradation of lactic acid under anoxic conditions was studied in several strains of Lactobacillus buchneri and in close relatives such as Lactobacillus parabuchneri, Lactobacillus kefir, and Lactobacillus hilgardii. Of these lactobacilli, L. buchneri and L. parabuchneri were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of l...

The effect of fermentation on the production of lactic acid, pH-development an on the growth of Escherichia coli strain NG7C in gruels made of whole grain wheat and whole grain tef under different conditions was studied. The results show that the number of E. coli decreased rapidly in both 1% and 10% back-slopping quicker than in control that was fermented without back-slopping. The growth of E...

Listeria monocytogenes, a food-borne pathogen, has the capacity to maintain intracellular pH (pHi) homeostasis in acidic environments, but the underlying mechanisms remain elusive. Here, we report a simple microplate-based fluorescent method to determine pHi of listerial cells that were prelabeled with the fluorescent dye carboxyfluorescein diacetate N-succinimidyl ester and subjected to acid s...

Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface...

the silica boron sulfuric acid nanoparticles (sbsans) as an efficient heterogeneous solid acid catalyst with both brønsted and lewis acidic sites catalyzed the preparation of bis-4-hydroxycoumarin derivatives using reaction of aldehydes and 4-hydroxycoumarin under mild and solvent-free condition at room temperature. this new and efficient methodology has advantages in comparison with currently ...