Composite restorations aren’t the problem, patients (and their genes) are


A new study shows that composite restorations are superior to amalgam restorations.

Despite advances in composite resins, dental amalgam still remains a popular option for posterior tooth restorations. Many assume that composite restorations are more likely to fail, especially in more challenging cases where there is a belief that amalgam will perform better. However, new research shows that it is not so much the filling that matters, but patient factors.

In a new study published this week in the journal “Frontiers in Medicine,” authors from the University of Pittsburgh School of Dental Medicine in Pennsylvania and the University of Pernambuco School of Dentistry in Brazil found that factors such as genetics and tobacco and alcohol use are the main reasons for restoration failures.

The study examined the University of Pittsburgh School of Dental Medicine Dental Registry and DNA Repository project, which keeps data on the population treated at the school. The authors examined all restorations of posterior teeth involving the occlusal and at least one proximal surface, and the status of those were examined at one, two and five years after placement. Overall, the study examined 6,266 amalgam and 2,010 composite restorations in 807 patients over a period of around 10 years. The authors also examined an additional 443 extensive direct composite resin restorations in anterior teeth.

Related article: 5 ways procedures are changing because of bulk fill technologies

The results showed that overall, failure rates between amalgam and composite restorations are very similar. For the first two years, amalgam performed slightly better (A 0.09 percent lower failure rate up to the first year of follow-up, 0.74 percent up to the second year of follow-up), but composites began to pull away from amalgams with a 2.05 percent lower rate of failure up to five years of follow-up. The authors noted that though these numbers seem small, over a large population group the cost savings could be substantial.

So if rates of failure are the same, why do restorations fail, and why are composite restorations seen as more prone to failure? To answer this, the authors looked at a variety of factors that could potentially affect composite restoration failure rates, such as age, sex, diabetes and periodontal health status.

Smoking was found to be a culprit in increasing failure rates, but interestingly, affected men more often than women. Alcohol was another factor, increasing the failure rate within two years.

Perhaps most interesting is the role genetics play in failure rates. The researchers looked at 92 patients with a failed composite resin in either the anterior or posterior teeth. They compared those patients with 92 other unrelated patients, who matched with the other group by type of restoration and other factors such as age, sex, ethnicity, and tobacco and alcohol use. The authors could then examine the role matrix metalloproteinases (MMPs) play in failure rates.

Related article: 5 ways your composite choice may be costing you money – and making your patients unhappy

MMPs are exposed and activated by acidic agents during the adhesive bonding process. The authors hypothesized that certain MMP alleles could increase the degradation of collagen fibrils at the resin–dentin-bonded interfaces, which could in turn lead to restoration failures.

The MMP2 rs9923304 TT genotype was one example of an MMP linked to composite restoration failure. Other research has shown that that specific genotype is found in 23 percent of Whites, 14 percent of Chinese and Japanese, and 1.8 percent of Yoruba Africans.

The authors conclude that composite restorations can fully substitute for amalgam restorations in ordinary dental practice, but to be wary of tobacco and alcohol use. They also suggest that more personalized care, such as genotyping rs9923304, may be useful in determining follow-ups to extensive composite resin restorations.


Vieira AR, Silva MB, Souza KKA, Filho AVA, Rosenblatt A and Modesto A (2017) A Pragmatic Study Shows Failure of Dental Composite Fillings Is Genetically Determined: A Contribution to the Discussion on Dental Amalgams. Front. Med. 4:186. doi: 10.3389/fmed.2017.00186

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