Sabrina Farch, Zohra Bengharez and Jesse Greener
Department of Chemistry, Djillali Liabes University of Sidi Bel-Abbes, Sidi Bel Abbes, Algeria
Research in the field of biology and chemistry is a key issue in dentistry. In aquatic conditions, the bacterial cells form biofilms as a mechanism for enhancing the survival and dispersion. Biofilms develop through a series of steps in the oral environment as a structurally complex and dynamic biological system where bacteria interact with their environments. The expression of genes and environmental conditions, including the surface properties, the hydrodynamic conditions and the characteristics of the medium, may have positive or negative influences on formation of bacterial biofilm on the tooth enamel surface composed of hydroxyapatite CaHA. The variation of pH and the oral bacteria play a fundamental role in the dissolution of the CaHA and consequently on the development of tooth decay . These parameters are not the important factors, fluoride and some co-existing ions in the oral environment affect considerably the dissolution process . In this context, our study aimed to evaluate in vitro the effect of pH variation (4.32 to 7.00) on the dissolution of hydroxyapatite in a microfluidic device (PDMS) containing glucose and in presence of selected bacteria: Streptococcus salivarius. The kinetic study of dissolution hydroxyapatite dental was carried out using a white light optical microscope '' OLYMPUS IX73’’ . Preliminary results showed that all kinetics are highly sensible to pH, the intensity of light increased gradually. The pH 4.32 which is below the critical pH of tooth enamel (5.5) represents significantly the dissolution phenomenon of CaHA. In this conditions, maximal inhibition of 61.3% was observed for a concentration of 1.5 mg/L of fluoride. However, 0.5 mg/L of Fluoride and chloride concentrations ranging from 50 to 250 mg/L allowed us to evaluate an inhibiting rate of 60.5% for the mixture of: 0.5 mg/L [F-] and 50 mg/L [Cl-]. This result explains the effect of interference and competition of Cl- which outweigh the fluoride effect . The microfluidic approach developed in this work allowed us to create the in vivo conditions to study the dissolution mechanism of Hydroxyapatite and to evaluate the effects of various determinants of its inhibition.
Keywords: Microfluidic, hydroxyapatite, pH, bacteria, biofilm, Chloride, fluoride, dissolution.
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