What is the difference between a composite restoration and an amalgam restoration?
by Dr. William
Amalgam restorations have been used to restore decayed and damaged teeth for over 150 years. Most people refer to amalgam fillings as ‘silver’ fillings because of their color when first place. But, in actuality, amalgam fillings consist of silver, 50% mercury, tin and copper with small amounts of zinc, indium and palladium. Amalgams are considered by many as the restoration of choice for posterior teeth because of its strength, durability, pliability and low cost. However, concerns have been raised with the use of amalgam fillings due to its content of mercury. Mercury is the key element in the mixture of the amalgam powder which allows for the pliability of the material which can be easily placed in any tooth followed by quick hardening. At one time it was believed that no mercury was released from amalgam restorations. However, with advancements in technology and more sensitive testing methods, it has been shown that as the amalgam ages, mercury is released in a vapor form. This vapor mercury is released every time a patient eats, drinks or brushes their teeth. But, exactly how much mercury is release continues to be debated. In fact controversy continues to exist as to how much mercury is bad for the human body. As a result of the debate over the use of amalgams in American dental offices, the FDA was asked to review the available research on amalgam fillings and in a 2009 decision, concluded that amalgam is a safe and affordable restoration to use in adults and children over the age of 6.
On the other side of the controversy concerning the use of amalgams is the fact that mercury is a known neurotoxin that rapidly depletes the immune system and in low doses has a toxic effect on the human nervous system, and has been linked to possible harmful effects on the cardiovascular, immune and reproductive systems. In response to the findings that conclude that mercury is toxic when introduced into the human body, countries like Denmark, Norway and Sweden have completely banned the use of amalgam while 28 countries in the European Union will be banning the use of amalgam restorations in children under 15 and in pregnant and nursing mothers as of July 1, 2018. By July 1, 2019 each of the 28 countries must submit a plan as to how they will reduce the use of amalgams in the remainder of the population while countries like the United States and Canada continue to promote the use amalgam restorations.
Resin composite restorations are made up of ceramic and plastic compounds which are utilized in tandem with a dental bonding system. Dental bonding systems are designed to improve durability, strength and longevity, while reducing post treatment sensitivity. With technological advances, dentistry is now utilizing 7th generation bonding systems that are an ‘all-in-one’ system. These types of bonding systems (I-Bond, Xeno, G-Bond, Optibond) combine etch, prime and bond into one solution. This not only enables easier handling, but reduces time and possible contamination with moisture.
Advantage of Composite Restorations
There are several advantages of utilizing composite restorations over amalgam.
Better adhesion – Unlike amalgam restorations that depend on mechanical retention, composites in combination with an adhesive system chemically bonds to natural tooth structure. This allows for minimum preparation of tooth structure.
Restorative strength – Teeth that are restored with composite restorations can be restored removing a minimum amount of tooth structure. As a result, with more natural tooth structure remaining the stronger a tooth can be. In addition, unlike amalgam restorations that expand and contract when exposed to thermal changes in the mouth which result in fractures in tooth structure, composites do not undergo thermal changes.
Improved texture – Unlike amalgam restorations, composite fillings can be contoured to a more natural anatomy, then polished to a smooth consistency that closer to that of enamel. In addition, the surface of composite restorations allow for repair unlike amalgams.
Natural Looking – Composite restorations are tooth colored and blend in with adjacent tooth structure. This makes composites look natural and difficult to detect when the shade of the composite is matched to the tooth being restored.
Safer Restoration – Composites do not contain any mercury. As a result, the controversy that surrounds amalgam restoration and their release of mercury vapor does not apply to composite restorations.
Affordable – In comparison to other tooth colored restorations such as porcelain crowns, porcelain inlays/onlays, composites offer a more affordable option as well as an improved alternative to a metal restoration.
Whether you agree with the use of amalgam or not, what is true is that amalgam restorations release mercury into the human body, that aging amalgam restorations cause fractures in the teeth they are placed and extensive amounts of tooth structure whether decayed or not must be removed in order to guarantee the retention and strength of the amalgam. This was acceptable 20 years ago as that was where technology had taken us. But, with the advances made in dental materials, affordable alternatives like composite restorations must be considered when restoring teeth. Finally, it is each dentist’s obligation as a health care provider to inform her/his patients of the advantages and disadvantages of having composite verses amalgam restorations placed in their mouth as a definitive restoration.