Choosing the Most Appropriate Restorative Material

Dental amalgam has historically been the gold standard of restorative care. Recently, however, the use of composites as a restorative option has grown in popularity.¹ In one survey 50% of dentist respondents reported a decrease in amalgam use over the previous 5 years.² Composite may seem like the obvious replacement for dental amalgam, but some research shows that it is not as durable or long-lasting as amalgam.^1,3–7

Amalgam has been used in dentistry for more than 165 years.³ Almost since its inception, the use of dental amalgam has been controversial. This is because it is composed of mercury, which has significant side effects with high levels of exposure.⁸ According to the United States Environmental Protection Agency (EPA), mercury can cause loss of peripheral vision; impaired speech, hearing, and gait; and muscle weakness.⁸ However, past studies have consistently proven that the levels of mercury in amalgam do not cause negative health effects and that it is a safe restorative material.^9,10 Results of studies with large patient samples showed no correlation between a patient’s health risk and how many dental amalgam restorations were present.¹⁰

The environmental hazards related to amalgam disposal have also led to a decrease in its popularity. In some countries, environmental protections limit the use of dental amalgam. If these same restrictions are implemented in the United States, the use of less durable materials will continue to increase, possibly leading to future complications for many patients.^1,3–7

EFFECTS ON ORAL HEALTH PROFESSIONALS

Recently, research has investigated whether the presence of mercury in amalgam has negative health consequences for oral health professionals.^10–12 Dental professionals are repeatedly exposed to amalgam restorations during both placement and removal. One study surveyed dental assistants who had been practicing since 1970 and were exposed to amalgam restorations. The study reported that, in comparison to a control group, the dental assistants experienced a higher occurrence of neurological symptoms, including memory problems, difficulty concentrating, fatigue, and sleep disturbances.¹¹ While the majority of the control group did not report these signs, high-quality research is still needed to demonstrate causality.

Results of a study of dentists found that the occupational exposure to mercury through amalgam restorations increased the risk of tremors.¹⁰ On the other hand, another study of dentists did not find any significant side effects from similar occupational exposure.¹² With these conflicting reports, it may be that memory bias led to inconsistent results. Further research is needed on the subject of occupational exposure.

ENVIRONMENTAL IMPACT

In large quantities, mercury is harmful not only to humans, but also to the environment.¹⁰ The toxic environmental effects of dental amalgam, which contains mercury, must be considered. According to the EPA, dentists are releasing approximately 5.1 tons of mercury waste each year and serve as the main source of discharge into the environment through publicly owned treatment works, which are essentially government-owned sewage facilities.¹³

Besides dental practices, cremation is another culprit in mercury emissions. A 2010 study found the cremation of bodies with amalgam restorations led to the emission of approximately 8,000 lbs of mercury over 1 year.¹⁴ While this is minimal compared to the larger amounts released by other means, it may be a factor when determining whether dental amalgam is the right choice for a patient.

RESTRICTING AMALGAM USE

Today, the EPA requires all dental practices that use amalgam restorative materials to implement amalgam separators. These devices remove particles of amalgam from dental office water that is released in the area’s sewage system via methods such as sedimentation, filtrations, and centrifugation with the ultimate goal of reducing the amount of amalgam entering the sewage system.¹⁵ The rule must be followed by newly established offices but a grace period has been granted to existing offices that ends on July 14, 2020.¹⁶ Compliance with this rule is expected to almost completely eliminate the discharge of mercury into publicly owned treatment works.^14,16

The European Union (EU) has also released guidelines for the use of amalgam restorations. These include the mandatory use of amalgam separators, restrictions for the use of amalgam placements on children and pregnant women, and requirements that amalgam waste is handled by a waste management company.¹⁴ The goal of these restrictions in the EU is to phase out amalgam restorations completely.¹⁴

AMALGAM ALTERNATIVES

Esthetically pleasing composites, resin ionomers, glass ionomers, ceramic inlays, onlays, and gold alloys serve as alternatives to dental amalgam. For the clinician, the decision is typically based on longevity, while a patient may prioritize cost-effectiveness. Studies have shown that gold restorations have excellent longevity—even more so than dental amalgams—but amalgams are still 3.8 times more cost-effective than a gold crown.¹⁷ Ceramic inlays have a 98% probability of survival over a 7-year period.¹⁷ Glass ionomer restorations also release fluoride, which may be beneficial to particular patient populations. However, the leading cause of glass ionomer restoration failure is secondary caries.¹⁷

COMPARISON STUDIES

With the future of dental amalgam restorations in question and the increasing popularity of more esthetically pleasing materials, the use of composite materials will likely increase, while the use of amalgam restorations will continue to decline. However, numerous studies have concluded that dental amalgam is still the more reliable choice.^1,3–7,18 In a randomized study of children ages 6 to 10, composites were seven times as likely to need a repair than their amalgam counterparts.⁴ Various studies of adults have shown that composites’ failure rate is anywhere from 2 times to 3.5 times higher than amalgams.^5,6 Additional research demonstrates that amalgam restorations provide greater longevity than resin composites for numerous reasons, and tend to perform better over longer periods, especially in load-bearing situations.^3,7,18 Another factor to consider is that removing amalgam restorations results in a loss of healthy tooth structure, weakening the respective tooth.⁵

FUTURE NEEDS

With the growing popularity of composite restorations, it is clear they are here to stay. However, their increased risk of failure presents a conundrum. Some studies note the location of the bonding agent as a point of weakness and suggest that a more durable anticariogenic dentin adhesive needs to be developed in order to increase composite’s longevity.^4,17 Other researchers state that additional training for dentists is necessary so they can repair imperfect restorations.¹⁹ Not all dentists are adequately trained in conducting procedures without the use of dental amalgams, or they are skeptical of their effectiveness.¹⁰

Modified silver amalgam compound may be used to help eliminate the free mercury in amalgam restorations. According to the US Food and Drug Administration (FDA), current dental amalgams contain 50% mercury.²⁰ By creating a compound containing a smaller percentage of mercury, the presence of unbound mercury may be eliminated. More research is needed on the subject.

In order to prevent the need for restorative care to begin with, the American Dental Association (ADA) recommends that clinicians use sealants more frequently on adults. The standard of care, according to the ADA, should be sealant placement with the application of 5% sodium fluoride (NaF) varnish every 3 months to 6 months to help arrest any occlusal noncavitated carious lesions within permanent dentition.²¹

AMALGAMS AND THE DENTAL HYGIENIST

Dental hygienists should understand the benefits of each type of restorative material so they can best advise their patients. Patients also need instruction on proper self-care in order to support longevity of their restoration. In 2005, more than half of the restorations placed in the US were replacements for failed restorations.¹⁸ Using proper in-office fluoride treatments, such as 5% sodium fluoride varnish, 1.23% acidulated phosphate fluoride, stannous fluoride, and others, can also help to prevent decay. Dental hygienists need to ensure their patients have all of the facts necessary to make informed decisions on their current and future dental needs.

CONCLUSION

While research demonstrates the cost-effectiveness and longevity of dental amalgams, their use continues to decline.^1,2–7,17 However, composite restoration material is a reliable alternative.¹⁹ Oral health professionals need to consider these factors when determining the best material for each individual patient. An open line of communication must be maintained so patients understand the risks and benefits and alternatives in regards to restorative materials so they can make informed decisions. Patients must also be reminded that prevention—which includes the placement of sealants in adults—is the best way to safeguard against the breakdown of healthy tooth structure.¹⁰

REFERENCES

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From Dimensions of Dental Hygiene. May 2019;17(5):14–16,19.