diffractometer is a most useful method for measuring the spacing or orientation of these dispersed silicate platelet layer spacing of montmorillonite treated with octadecyl trimethyl amine increases 36 from a natural state of 25 26 u00e5 to 41 u00e5 after polymerization also polyoxyethylene decyloxypropylamine increases spacing of smectite by 22 from 28 29 u00e5 to that of 37 u00e5 the larger the spacing range the more optimum the result in a more preferred embodiment fig2 also depicts the accessibility of the surface treatment to the resin after intercalation or exfoliation this positioning allows optimal surface treatment thereby fully incorporating the resin for bonding during polymerization binding of the resin to the surface modifier allows for a more flexible resin to transfer stress to the stiffer layers in another more preferred embodiment bifunctional coupling agents or silanes are used in combination with the surface modifier to improve physical and mechanical properties and to provide hydrolytic stability by preventing water from penetrating along the silicate resin interface in some composites if the silicate platelets are not bonded to the resin they can actually weaken the material examples of bifunctional coupling agents include but are not limited to organo functional silanes the bifunctional coupling agent used in dental composites is preferably a methacryloxy silane which co polymerizes with methacrylate based resin the bifunctional compound contains a silicon functional group that hydrolyses and reacts with active sites on the inorganic surface and an organo functional group that co polymerizes with free radical cured resin specifically the silane coupling agent bonds to the edges of the platelets where the necessary hydroxyl groups are present the platelet edges.