Has Resin-Based Composite Replaced Amalgam?

The question posed in the title of this article has been debated for more than 40 years. In 1968, the product Adaptic, then sold by J&J, was promoted as a replacement for amalgam. During the following 40 years, the polarized debate has constantly raged, and, in spite of leadership organizations supporting amalgam use, the controversy continues.

BACKGROUND: IS AMALGAM SAFE?
World health organizations have consistently supported the use of amalgam. In an official publication, the FDI World Dental Federation stated: “While much research has been devoted to the development of restorative materials, there is currently no direct filling material that has the wide indications, ease of handling and good physical properties of dental amalgam. The restorative materials currently available as alternatives to dental amalgam significantly increase the cost of dental care.”1

The Council of European Dentists stated: “Research over many decades has failed to show any significant health risk posed by dental amalgam,” and “Restrictions on the use of amalgam would damage the financial stability of health systems as well as impact on individual patients’ ability to afford dental care.”2

The ADA has stated: “Dental amalgam (silver filling) is considered a safe, affordable and durable material that has been used to restore the teeth of more than 100 million Americans. It contains a mixture of metals such as silver, copper and tin, in addition to mercury, which binds these components into a hard, stable and safe substance. Dental amalgam has been studied and reviewed extensively, and has established a record of safety and effectiveness.” The ADA’s Council on Scientific Affairs’ 1998 report3 on its review of the scientific literature on amalgam states: “The Council concludes that, based on available scientific information, amalgam continues to be a safe and effective restorative material.” The Council’s report3 also states, “There currently appears to be no justification for discontinuing the use of dental amalgam.” The ADA further states, “While questions have arisen about the safety of dental amalgam relating to its mercury content, the major US and international scientific and health bodies, including the National Institutes of Health, the US Public Health Service, the Centers for Disease Control and Prevention, the Food and Drug Administration, and the World Health Organization, among others have been satisfied that dental amalgam is a safe, reliable, and effective restorative material.”4

Is amalgam still in use by the majority of practitioners? In our various speaking events around the world, we have found that amalgam use in some countries is minimal, while in other countries, it is used routinely. In a survey a few years ago conducted by Clinical Research Associates, 73% of mainly North American respondents stated that they used amalgam.5 Undoubtedly, it is lower today. The differences in amalgam use among countries appear to be related to economics, dental education, and aesthetic orientation of the residents.

In this article, we will discuss the locations and situations in which amalgam is still used in many practices, express our opinions on why amalgam is still used, and discuss our conclusions on when and where resin-based composite use is appropriate.

WHERE AND WHEN PRACTITIONERS STILL FAVOR AMALGAM
Some practitioners strongly favor amalgam use in specific situations, and some find they cannot treat certain situations without amalgam. In our many encounters with practicing dentists, the following sentiments have been shared with us when we have expressed positive comments about resin-based composite use in posterior teeth.

•Areas in which moisture control is difficult. Deep box forms on any posterior teeth pose a clinical challenge for placement of resin-based composite, because of the frequent risk of moisture contamination. This condition is especially critical on the distal surfaces of the most posterior molars. Often, moisture seepage is unavoidable in or around the best placed matrix strips used by highly competent clinicians. Amalgam is the choice of many dentists in these situations.

An alternative treatment for those areas for dentists not using amalgam is placing resin-modified glass ionomer as the first ~2 mm of restorative material in the depth of the box form (Fuji Filling LC [GC America], or Ketac Nano [3M ESPE]), and curing it. The matrix strip is then moved occlusally, and resin-based composite is placed in the remainder of the restoration. This concept provides adequate aesthetic appearance, radiopacity for future diagnosis, fluoride release, and greater patient acceptance than amalgam.

•Need to place large restorations involving most of the occlusal surfaces of the affected teeth. We see at least 2 major reasons why many dentists still choose to use amalgam in these situations. The time involvement to place large resin-based composite restorations in posterior teeth is well-known by most dentists to be excessive when compared to amalgam. However, experienced resin users may disagree with the preceding statement. Additionally, more than 4 decades of clinical observations show the wear of most resin-based composite materials to be greater than the wear of amalgam.6 This wear challenge is being overcome by improvements in resin-based composite materials.7 A rebuttal to the above use for amalgam is that the most appropriate treatment for such broken down teeth is placement of crowns at greater expense.

•Desire to keep fees low for financially compromised patients. The organization statements mentioned previously1,2 note that amalgam provides economically acceptable restorations. In our opinion, their conclusions are correct only if amalgam restorations remain at the low fee level of the past. However, when analyzing the time involvement of amalgam placement in relation the average fees for amalgam, the amalgam procedure is far below an acceptable fee for the time involved. In other words, typical amalgam fees have been historically low, but the time involvement required to place amalgam restorations is worth more than current amalgam fees when compared to other procedures of similar time involvement and difficulty.8
COMPOSITE RESIN USE IN POSTERIOR TEETH: CURRENT AND FUTURE
The following are our personal observations related to the current use of resin-based composite and amalgam as posterior tooth restorative materials in North America and the future of their use.
• There are many practitioners who do not use any amalgam in their practices, and the trend is growing. As prosthodontists, dealing primarily with complicated and difficult cases, we see almost no cases where amalgam is highly indicated over other materials, assuming practitioners have competency in placing resin-based composite and/or the patient can afford onlays or crowns.
• Amalgam has served the profession and the people we treat with admirable functional acceptability, but clearly with lack of aesthetic acceptability. We predict that amalgam will continue to be used for several decades in the situations we have discussed, but that it will die an aesthetic death over the coming years.
• Patients do not want “black/ grey” teeth! When offered a choice, few patients choose amalgam over tooth-colored restorations. I have long suggested that the fees for amalgam and resin-based composite should be equal to eliminate patients choosing one restorative type over another on the basis of fees.
•l Every patient should be provided with information about all of the treatment types available. The necessity for so-called “informed consent” before starting treatment is evident. Placing unaesthetic amalgam restorations without informing the patient of the available tooth-colored materials is not appropriate, and could lead to legal activity on the basis of “lack of informed consent.”9
• Although controversial and undoubtedly related to clinician skill and experience, resin-based composite has served well in posterior teeth with small to moderate sized lesions, with isthmus cuts up to one third to one half of the cusp-tip to cusp-tip distance.10-19 When tooth structure removal is in excess of that described, other types of restorations are indicated, assuming finances allow the more expensive restorations.
• Dentists primarily educated/ trained in school to place amalgams find placement of resin-based composite to be difficult, while dentists trained/educated primarily to do resin-based composite find amalgam difficult to place.

SUMMARY
The major health organizations in the world continue to accept amalgam use, but the “amalgam war” of the 1800s is still going on. The end is not in sight. There is little disagreement that amalgam serves well and, although controversial, it appears to have minimal to no health hazards.

There is a wide variation in the relative amount of amalgam placed in developed countries, and many dentists in North America do not use it. However, amalgam is still being used at least some of the time by the majority of practitioners in North America, and most of those practitioners also place resin-based composite in Class II locations.

The evolution from amalgam to tooth-colored restorations has been a slow and tumultuous journey. The acceptability of resin-based composite in Class II locations continues to be a question for some dentists, while others have concluded that amalgam is “dead.” It would be highly desirable if some of dentists using the alleged poisonous properties of amalgam as a “practice building” ploy would find more legitimate methods to increase their practice activity.