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The Amalgam Controversy: Where Do We Go From Here?
Q: What does the future hold for amalgam as a restorative material?
A: I have been involved with the questions surrounding amalgam for several decades on the national and international levels. The subject keeps emerging from the dust.
As is commonly known, the World Health Organization, the FDI World Dental Federation, and the American Dental Association continue to support the use of amalgam. These organizations have spent enormous amounts of time, effort, energy, and money to substantiate their positions. The scientific information on the subject is well known, and it does not condemn dental amalgam. However, the alleged problems with amalgam are expressed on the Internet by many anti-amalgam groups. Patients have complete access to these websites, and the result is continuing uncertainty on the part of the lay public about the safety of dental amalgam. Similarly, resin-based composite has alleged health challenges related to its reported potential estrogenic influence and the ingestion of glass particles as it wears during service.
In recent discussions with Tom Limoli of Limoli and Associates, an expert on third-party payment programs, I was informed that US third-party payment data for 2010 show that 65% of direct posterior tooth restorations last year were resin-based composite, while 35% were amalgam. These data show that the use of amalgam is not dominant and decreases each year. It has been my observation from delivering many continuing education programs that most US dentists place resin in posterior teeth whenever it seems feasible. However, there are times when some dentists feel amalgam is a better restorative material than resin, such as with deep proximal box forms, the distal surfaces of second molars, bifurcation and trifurcation restorations, and other similar difficult access areas.
Numerous meta-analyses show amalgam to have approximately twice the longevity of resin-based composite in posterior teeth. Our research conducted in Clinicians Report (previously known as CRA) shows that current resin-based composite materials are excellent, and that reported clinical challenges with resin are primarily technique problems, not material problems. Placed with proper technique, composite can serve much better than has been reported.
There is no question that most patients want tooth-colored restorations. In my opinion, amalgam is suffering an “esthetic death,” not a physiologic death. I have personally placed only a few amalgams in the past 15 years, and these situations would have been better served with crowns or onlays if adequate financial resources had been available.
To summarize, the major organizations in dentistry support amalgam use. As reported in many research projects, on the average, composite is statistically inferior to amalgam when used in posterior teeth. While amalgam is primarily used in the United States when resin seems inappropriate, its use in the US is declining each year and is non-existent in numerous developed countries. The age-old argument about the viability of amalgam and its alleged health challenges will not be solved until amalgam dies a natural death in the United States. This is happening slowly, and the eventuality of it is predictable.
A: For decades, amalgam was considered the primary restorative material for posterior teeth because of its long-term success, relative ease of placement, and tolerance for success in difficult working conditions. Now, it is demonized by the public and some in the profession as a horrible, unhealthy material; however, most dental schools continue to teach its use. Why do the schools continue to persist in using this material if it is so bad?
As students begin their careers in dental school, they need to learn some hand skills to allow them to be successful dentists. Plus, they also like to get a good grade for their efforts. How can this be done with a composite preparation, which really has no standard from which a grade can be determined? An amalgam preparation has specific criteria from which deviations can be determined and skills can be evaluated.
A dental school is working with beginners who need a material that does not require the same skills of use as those of a more experienced operator. It is the duty of the dental school to try to teach the proper placement of composite resin, and most dental schools have dramatically increased the time spent in this area. However, some fall-back material, such as amalgam, is needed for beginners who need more experience before working with a more difficult material without harming their patients.
Every dentist needs an alternate material to use when either the area cannot be isolated sufficiently, the lesion is subgingival, or the patient has financial issues. Amalgam has been that material for decades, but it may not be in the future.
A: Whenever I hear dentists today talking about the amalgam controversy, I wonder why we are still looking back over our shoulders at what has been. With the current evidence available there is no doubt that amalgam has demonstrated safety and effectiveness as a restorative material. What we should be doing is looking ahead.
The trends are toward less use of amalgam and a greater use of composite resin for direct placement of posterior restorations. Dentists’ focus should be on understanding how to make posterior composite resin restorations as durable or more durable than amalgam restorations. Product manufacturers have provided us with adhesive systems and improved wear-resistant composite resins. For routine-sized posterior restorations, composites perform as well as amalgam, but for larger restorations amalgam has done better. The greatest challenge dentists face regarding the amalgam controversy is improved clinician techniques for longer-lasting composite resin restorations. Amalgam is a very forgiving restorative material with easily manageable placement techniques, and it is tolerant of moisture and other contaminants during placement. Composite resin requires greater attention to detail in placement to include the need for excellent isolation that is free of contamination during placement.
More research is pointing to a better understanding of light-curing techniques and devices, as well as the energy required to fully polymerize composites to obtain optimal adhesion and marginal sealing. Better matrix systems are available to address the challenges of proximal contact in the posterior.
We still don’t fully understand why posterior composites have higher rates of postoperative sensitivity. There are many theories, but this issue seems to be more clinician controlled in the techniques and materials used. Amalgam is an excellent restorative material, but the majority of the restorations clinicians place in the future, both anterior and posterior, will be composite resins. We just need to be placing them better.
About the Authors
Gordon J. Christensen DDS, MSD, PhD
Director, Practical Clinical Courses
Cofounder and Senior Consultant
Brigham Young University
University of Utah
Salt Lake City, Utah
James F. Simon, DDS, MEd
Director, Division of Esthetic Dentistry
Professor, Department of Restorative Dentistry
University of Tennessee College of Dentistry
Howard E. Strassler, DMD
Professor, Division of Operative Dentistry
University of Maryland Dental School