If your tooth is having decay (cavity), your dentist removes the decay & the resultant cavity is filled by specialized material. It is used to restore the function, integrity & morphology of missing tooth structure. There have been lots of advances in modern dentistry that make this process much more comfortable and materials that are used are safer and more esthetically pleasing
Mainly there are two types
1. Silver Amalgam (Silver + Mercury)
2. Composite Resin (tooth colored)
Many other types of filling materials are also being used by the dentists depending on specific requirements like Glass Ionomer, certain dental cements etc.
In Modern dentistry Composite Resin is preferred as it is having sufficient strength, is of tooth color & easy to handle. It has got excellent finishing & polishing & various shades are available making it look very natural. Disadvantages are its technique sensitivity, tendency to discolor over long period of time. If not done properly, can result in post filling sensitivity.
Amalgam has been widely used for direct fillings, mainly for posterior teeth, but because of certain disadvantages like its metallic color, taste, leaching out of mercury, tendency to shrink & corrode, the tooth has unaesthetic appearance hence, it is less preferred by the patients & dentists.
This material has a specialized use especially in milk teeth cavities & non stress bearing areas. Advantage is that it is white colored & release fluorides which help in controlling secondary caries but it doesn't have sufficient strength. Material is difficult to handle & requires absolute dry field. It cannot be immediately finished & polished hence, requires another sitting.