الفهرس 
abstractOnly 14 pages are availabe for public view
 |  | from | 135 |  |  |
| | | from | 135 | | |
Abstract
Antiplaque treatments have’ included the use of enzymatic
preparations, antibiotics and antibacterial agents, fluorides and
vaccination procedures. The present study has been directed toward
the inves,tigation of a new approach for dental plaque prevention. It
is believed that lowering the surface energy of human enamel by
applying a hydrophobic film-forming agent might interfere with the
bacterial adhesion to the tooth surfaces.
The adsorption of a group of polydimethylsiloxane polymers from
different solvent systems on hydroxyapatite has been studied. The contact
angle measurements on compressed apatite discs were used to determine the
wettability of the formed films. In the course of these studies some
effects of pretreating the apatite discs with metal salts before polymer
treatment have been demonstrated. Generally, when stannous chloride or
zinc chloride were the pretreating agents, polymer films having high
contact angles and good permanence were obtained.
Equilibrium adsorption data were analyzed and possible adsorption
mechanisms were considered, taking into account the molecular configu-
rations of the polymers and the effects of the solvent. In order to
obtain a clear understanding of the adsorption behavior of these
compounds, detailed systematic studies w:E,;~fied out of two linear polydimethylsiloxane polymers on calcium fluoride. A physical model that explains the adsorption behavior of the two polymers was proposed. Experiments with hexane, acetone and ethanol solvents showed a large dependence of the adsorption upon the solvent. These data were interpreted on the basis of either the solvation of the polymer and/or solvent competition for adsorption sites.
Competitive adsorption on calcium fluoride was investigated using the polymer and ethanol or acetone as competitive adsorbates. The
polar solvents were found to compete with the polymers for about one-half of the calcium fluoride surface sites.
In general, the studies on the adsorption of the two linear
polymers have indicated that the molecular configuration of the polymer
adsorbed onto a solid surface is essentially a function of (a) the
strength of the polymer adsorption onto the solid surface; (b) the
degree of polymer solvation by the solvent and (c) the extent to which the solvent is able to compete with the polar anchoring segments of the polymer molecules for the surface sites.
A statistical treatment of the adsorption of linear polymers on solid surfaces has been carried out. Calculations based upon a previously developed model were made to evaluate the energetic dependence of the extent of adsorption of each polymer configuration. The high adsorption energy of the polymer to the solid surface has been found to overwhelm both the bulk concentration and the solution solvation effect on the adsorbed polymer molecules. These calculations have defined the necessary energetic conditions for converting a hydrophilic solid surface into a highly hydrophobic one when a linear hydrophobic agent with terminal polar groups is employed.