Fluoride and the oral environment Sample Clauses

Fluoride and the oral environment. Effects on enamel When topical fluoride is present in the oral environment surrounding teeth (i.e. in saliva, plaque, crevicular fluid, oral soft tissues and directly on the enamel/dentine surface itself), there are two distinct post-eruptive effects on enamel. Low concentrations of ionic fluoride interact with enamel during the process of demineralisation to either modify the chemical and biologic characteristics of enamel apatite by forming fluorhydroxyapatite or calcium fluoride. The former is more likely to occur when the fluoride concentration is less than around 50 ppm and the environment is acidic. Formation of fluorhydroxyapatite occurs only in the outermost layers of enamel and forms an integral part of the tissue that will be lost if the tissue is worn away. Equation 1 Formation of fluorhydroxyapatite from hydroxyapatite in the presence of ionic fluoride Ca10(PO4)6(OH)2 + F− + H+ → Ca10(PO4)6(OH)F + H2O Under neutral conditions this is a slow process, however in a low pH solution the solubility of enamel increases considerably and fluorhydroxyapatite formation increases under such conditions. Ionic fluoride promotes conversion of brushite and octacalcium phosphate to apatite and promoting formation of fluorhydroxyapatite, in preference to brushite or β- tricalcium phosphate in acidic conditions (Ten Cate et al., 2008). At higher fluoride concentrations (>100 ppm) calcium fluoride is formed thus: Equation 2 Formation of calcium fluoride from hydroxyapatite in the presence of ionic fluoride Ca10(PO4)6(OH)2 + 20 F− + 8 H+ = 10 CaF2 + 6HPO42− + 2H2O Therefore the higher the concentration of fluoride and the more acidic the solution the more calcium fluoride is formed on the tooth surface. In the oral environment, calcium fluoride is also precipitated in plaque, in pellicle, in porosities and other plaque retention factors. Calcium fluoride is formed in the shape of spherical globules scattered across the tooth surface which can be seen using scanning electron microscopy as a round globule with a nodular surface around 0.6 µm in diameter (Xxxxxxx, 2000). Formation of calcium fluoride globules is the only surface event that is detectable using chemical means after application of high fluoride concentrations. Subsequently, after the calcium fluoride is worn away and all chemical traces have disappeared, a reduced caries incidence in the following months is noted (ten Cate and Xxxxxxxxxxxx, 1996).
Sample 1
AutoNDA by SimpleDocs

Related to Fluoride and the oral environment

  • Child safe environment 5.1 Catholic school communities have a moral, legal and mission-driven responsibility to create nurturing school environments where children are respected, their voices are heard, and where they are safe and feel safe.

  • Safe Environment The School shall maintain a safe learning environment at all times. The School shall develop and adhere to a safety plan, which shall be provided to the Commission.

  • Smoke Free Environment The Lessor shall make all parts of the leased premise smoke-free. "

  • Operating Environment Subscriber is solely responsible for acquiring, installing, operating and maintaining the hardware, software and Internet Browser environment necessary to access the Site and use the Services. Information on operating environment requirements can be located on the Site.

  • NON-SEXIST ENVIRONMENT 1. A non-sexist environment is defined as that in which there is no discrimination against females or males by portraying them in gender stereotyped roles or by omitting their contributions.

  • Environment Health and Safety 24.4.1. The Supplier and its staff (and/or any sub-supplier and/or subcontractor) shall comply with the laws and regulations in force related to protection of the environment, the health and safety instructions applicable to the Goods and Services performed pursuant to the Contract and especially, if appropriate, to the Goodsand Services performedon any Site by a third company.

  • Working Environment The Parties agree that a safe and clean working environment is essential in order to carry out work assignments in a satisfactory manner. It will be the Employer's responsibility to ensure that all working areas and Employer-owned vehicles are maintained in a safe and clean condition.

  • Work Environment It is mutually agreed that the prevention of accidents and injuries to state employees will result in greater efficiency of operations of state government. Toward this end, the Employer shall make every reasonable effort to provide and maintain safe and healthy working conditions and the Union shall fully cooperate by encouraging all employees to perform their assigned tasks in a safe manner.

  • FLOODPLAIN MANAGEMENT AND WETLAND PROTECTION Executive Order 11988, Floodplain Management, May 24, 1977 (42 FR 26951), 3 C.F.R., 1977 Comp., p. 117, as interpreted in HUD regulations at 24 C.F.R. Part 55, particularly Section 2(a) of the Order (For an explanation of the relationship between the decision- making process in 24 C.F.R. Part 55 and this part, see § 55.10.); and Executive Order 11990, Protection of Wetlands, May 24, 1977 (42 FR 26961), 3 C.F.R., 1977 Comp., p. 121 particularly Sections 2 and 5. COASTAL ZONE MANAGEMENT The Coastal Zone Management Act of 1972 (16 U.S.C. § 1451, et seq.), as amended, particularly sections 307(c) and (d) (16 U.S.C. § 1456(c) and (d)).

  • Safe Working Environment ACM does everything reasonably possible to provide a safe working environment for all of its stakeholders including Suppliers and its own employees and agents. ACM does not tolerate offensive, abusive, bullying, discriminatory or otherwise unlawful behaviour or any form of harassment (“Offending Behaviour”). If a Supplier engages in Offending Behaviour, ACM may suspend or terminate this Milk Supply Agreement.

Time is Money Join Law Insider Premium to draft better contracts faster.