Anticaries potential of calcium, phosphate and fluoride reservoirs of dental biofilms

Author(s)

Marília Ferreira Correia

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2010-04-23

Examining board members

Jaime Aparecido Cury; Marisa Maltz Turkienicz; Josimeri Hebling Costa

• Advisor: Jaime Aparecido Cury

Abstract

Dental biofilm presents organic and inorganic reservoirs of calcium (Ca), phosphate (PI) and fluoride (F) that could act as a source of these ions to biofilm fluid during pH drops, reducing dental demineralization. It's still unknown the source responsible for the increase of such ions in biofilm fluid after pH drop, since they could be also derived from mineral dissolution of dental structure. In addiction, there's no clear evidence about the solubility of these reservoirs according to the pHs considered important to interfere with dental demineralization. Thus, this study aimed to evaluate the influence of mineral dissolution of dental structure and also of biofilm reservoirs in the inorganic composition of biofilm fluid, analyzing the kinetics of Ca, PI and F to fluid just after pH drop. Two crossover and blind in situ studies were performed, which the aim of the first one was to evaluate the hypothesis of the inorganic composition of biofilm fluid after pH drop would reflect the mineral solubility of substrate where biofilm was formed. Thus, dental biofilm was formed during 4 days on enamel (less soluble), dentine (more soluble) and acrylic (not soluble) slabs, which were exposed to 8 times/day to 20% glucose solution. In the end of each phase, the acidogenicity, microbiological composition and inorganic concentration of these biofilms were analyzed. The second in situ study evaluated the relation between the amount of Ca, Pi and F reservoirs with the inorganic composition of biofilm fluid and moreover, the potential of these reservoirs to release Ca, Pi and F was estimated according to decreasing pHs (6.5; 5.5; 4.5 and acid). Therefore during 14 days, dental biofilm was formed on enamel and acrylic slabs, which were exposed to different frequencies of 20% glucose (0, 2 and 8 times/day) to form biofilms with different amounts of Ca, Pi and F reservoirs. The biofilm fluid analyses were the same performed in the first study, however the concentration of Ca, Pi and F in biofilm solids were determined after extraction with buffers of 6.5, 5.5 and 4.5 and with acid. A significant increase in Ca concentration was observed after pH fell; nevertheless this increase was the same regardless of the substrate where biofilm was formed and regardless of the amount of Ca, Pi and F reservoirs. Furthermore, biofilm reservoirs showed potential to release Ca, Pi and F at those pHs analyzed, although their solubility were inversely related with the frequency of glucose exposure that biofilm was formed. These findings suggest that biofilm reservoirs are important source of Ca, Pi and F to biofilm fluid after pH drop, however the inorganic concentration of fluid does not reflect the mineral solubility of substrates, the amount and solubility potential of biofilm reservoirs. (AU)

• FAPESP's process: 07/05978-8 - Anticaries potential of calcium, phosphate and fluoride reservoirs of dental biofilm
• Grantee: Marília Ferreira Correia
• Support Opportunities: Scholarships in Brazil - Master