Cross-linking dental formulations

The properties exhibited by polyelectrolytes make them nearly-ideal candidates for dental material formulations. Dental polyelectrolytes are generally considered to be nontoxic and are able to adsorb chemically to the hydrophilic surface of tooth material through ionic interactions. Ionic cross-linking of the polyelectrolyte with multivalent cations (Zn2+, Mg2+, Al3+, Ca2+) results in the formation of a rigid and insoluble cement matrix. The stability and strength of the cement is attributed to the fact that, if a bond is broken, it can be reformed as long as the other bonds are maintained. Even today, polyelectrolytes are the only materials which are known with certainty to form a bond, which is stable with time, to tooth material [120]. In addition to long-term stability, many polyelectrolytes are translucent and possess cariostatic properties [121]. 

All phenol polymers having free vinyl groups in the side chain (50, 56, and 57) could be furthermore subjected to thermal ciu ing due to cross-linking through the methacryhc groups [47,48]. A multi-methacrylate ohgomer was also prepared by polymer-analogous fimctionahzation of a poly(isopropylidenediphenol) (BPA) resin. Such materials could be of potential interest for the formulation of dental composites as direct esthetic restorative materials [15]. 

The resin matrix of dental materials has important influence on the chemical and physical properties of light cure resins. The organic formulations also include photoiniti-ating systems that absorb light. From there free radicals start the conversion of the oligomer blend to a polymeric cross-linked network. Camphorquinone (CQ) is widely used in dental resin mixed with an amine. However, CQ is a solid, yellow compound with an unbleachable chromophore. 

Purified c. is approved for ->food applications and used in ice cream formulations as crystallization inhibitor and in pet food. The pharmaceutical industry makes use of the property of c. to be insoluble in acidic media (stomach) and soluble in alkaline environments (intestine). Other uses are for dental impressions and in toothpaste. Cross-linked c. is used as a most powerful water absorbent in hygienic applications such as diapers and tampons. The sodium and calcium salts are used as suspending and viscosity-increasing agents in pharmaceutical applications. They act also as tablet binders as well as tablet disintegrating agents. CMMC is an effective film former in the manufacture of -> tobacco sheets. 

---