Dentist fillings?

In lieu of metallic amalgam fillings which contain mercury, dentists can fill cavaties with a dental composite which is a mixture of organic molecules,silicon and barium oxides, ytterbium trifluoride and a number of minor components. this mixture is applied to the tooth as paste but it quickly hardens as the desntist shines a bright light upon it. Is the hardening of the composite an example of a physical or chemical change? explain

Dentist fillings?
The reaction takes places via free radical polymerization:


Monomers+initiator+accelerator=polymer molecules.


There are also fluoride-releasing restorative materials. One of these is called resin-modified glass ionomers---aluminosilicate glass powder and liquid with water soloution of coploymers and water soluble monomers.


A type of restoration that is gaining popularity in the dental office is actually compomers--a hybrid of resin-modified glass ionomer and composite.


This is an example of a chemical change:


it involves an acid-base reaction of polyacid and ions released from aluminosilicate glass particles.


1-Calcium, aluminum, fluoride, and other ions released by outside of powder particle dissolving in acidic liquid


2-Calcium ions initially cross-link acid-functional coploymer molecules


3Calcium cross-links are replaced by aluminum ion cross-links





Hope this helps
Reply:chemical... light works as a catalyst