Composite resin and amalgam are the most commonly used filling materials in dentistry. Throughout the years, the content of both materials have been modified to improve the quality of the fillings.
Dental composite resins are types of synthetic resins. A composite material is a product which consists of two distinct phases normally formed by blending together components having different structures and properties.The purpose of this is to produce a material having properties which could not be achieved from any of the individual components alone. The two main components of composite filling materials are resin phase and the reinforcing filler. The resin gives the material the ability to be moulded at ambient temperature and polymerization achieved in a short time.Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, and insensitive to dehydration and were inexpensive. It is easy to manipulate them as well. Composite resins are most commonly composed of Bis-GMA monomers, a filler material such as silica and in most current applications, a photoinitiator. Dimethacrylates are also commonly added to achieve certain physical properties such as flowability. Further modification of its physical properties is achieved by changing the concentrations of each constituent.Unlike amalgam which essentially just fills a hole, composite cavity restorations when used with dentine and enamel bonding techniques restore the tooth back to near its original physical integrity.
The main advantage of dental composite over amalgam is improved aesthetics. Composite is a tooth coloured material and it comes in a wide range of tooth colours allowing near invisible restoration of teeth. Composite is bonded to the tooth with the use of dentine bonding agent. This strengthens the tooth structure. Unlike amalgam, there is no need to create retentive features which destroys healthy tooth structure because composite bonds to tooth chemically. Therefore, using composite material as filling is proven more conservative and less tooth preparation is needed.
Composite resin restorations have several disadvantages. The material is technique sensitive. If it is not placed properly the restoration may fail prematurely. It is moisture sensitive, thus needing the application of rubber dam which will be otherwise impossible in teeth which is partially erupted or unfavourably positioned. Composite take longer time to place than amalgam fillings. The material is also significantly more expensive than amalgam. The strength is also lower compared to amalgam, especially when placed in the posterior teeth. Composite resin undergoes shrinkage after polymerisation process takes place but it can be reduced by altering the molecular and bulk composition of the resin.
to be continued….