DentAI – Amalgam vs. Composite: The Latest 2025 Meta-Analysis and the Question of Replacing Healthy Amalgams

About This Study

This is a systematic review and meta-analysis published in 2025 in the International Dental Journal. Its aim was to compare the failure risk of amalgam and composite restorations in permanent posterior teeth. A total of 13 studies (randomized trials as well as prospective and retrospective cohort studies, spanning 1990 to 2023) were included in the analysis.

What Does RR = 0.96 Mean?

The meta-analysis's pooled estimate was an RR of 0.96 (95% CI: 0.68 to 1.34).

RR, or risk ratio, indicates how many times more likely failure is in one group compared with another. A value of 1 means the two materials fail at exactly the same rate; above 1 means the first material fails more, and below 1 means it fails less. Here the value came out to 0.96, meaning composite's failure risk was about 0.96 times that of amalgam — which, in practical terms, is equivalent.

The confidence interval matters too. Because this interval (0.68 to 1.34) contains the value 1, even this small difference is not statistically significant. In plain terms, no significant difference in failure was found between composite and amalgam.

Why This Result Matters

Until now, the 2021 Cochrane review had shown that composite failed more often than amalgam in posterior teeth and produced more secondary caries (in that review, composite's failure risk was roughly twice that of amalgam). This new meta-analysis changes that picture, arriving at parity rather than the superiority of either material.

And that's the key point. After all these years of advances in composite materials, and a global push to phase out amalgam, the strongest claim the new evidence can support is that composite is now "on par with" amalgam — not better than it. The authors themselves note that studies published after 2013 showed better outcomes for composite, likely reflecting improvements in the material itself. In other words, even this parity is a recent achievement of newer-generation composites.

Clinical Application: The Trend of Replacing Amalgam Over a Suspected Crack

These days it's common to see a healthy amalgam removed because "there was a crack underneath it," with composite placed in its stead. It looks scientific on the surface, but this very evidence calls it into question. Correctly determining whether an enamel crack is actually clinically significant is, by itself, a separate question worth its own discussion.

Here's a simple argument that looks at the whole body of data rather than a single tooth. In these same studies, fracture (of the tooth or the restoration) is itself part of the definition of failure, and interestingly, fracture is the most common cause of amalgam failure (whereas secondary caries is the main problem for composite). So if these cracks really mattered, they should have shown up in amalgam's failure rate, and amalgam should have failed visibly more often than composite. But that's not what happened — amalgam held up as well as composite, or even slightly better. In other words, when you look at the full body of restorations together, these cracks aren't common enough to drive a meaningful failure rate.

One more point supports this same reading. In the past, amalgam was typically placed in larger, more difficult cavities that are inherently more prone to failure. The fact that amalgam, under these tougher conditions, still didn't fall behind makes this argument stronger, not weaker.

Limitations and Caveats

This result shouldn't be read as saying more than it actually does.

First, the meta-analysis itself has weaknesses. The included studies varied widely (I² around 97%), the definition of failure was not consistent across them, and the data mixed trial results with registry statistics. So the more precise statement is that "composite has no proven superiority over amalgam" — not that "amalgam is definitely better."

Second, this doesn't mean "no amalgam restoration should ever be replaced." A symptomatic crack (cracked tooth syndrome, with pain on biting and on release) is real and should be treated. The point is that "there was a crack underneath it," without symptoms and without a demonstrable problem, is not on its own a strong reason to remove a healthy restoration — especially since this claim is typically raised only after the amalgam has already been removed, meaning it can no longer be verified. And when the basis for the decision is an ambiguous radiographic finding rather than a clinical symptom, there is also a real risk of mistaking a harmless pattern for actual caries or damage.

That said, this isn't meant to dismiss genuine caries found under an amalgam either. When real residual caries is discovered under an amalgam during an unrelated procedure (for example, while preparing for a crown), that is a demonstrable finding, not a hypothetical crack — and conservative management of just that carious area is a different matter from removing an entire healthy, asymptomatic amalgam restoration.

Practical Takeaway

Based on the latest evidence, removing a healthy, asymptomatic amalgam restoration and replacing it with composite is not automatically an upgrade. Composite is a good material with a legitimate place in practice, but in posterior teeth its longevity is, at best, on par with amalgam — not superior.

The reason for replacement should be a real, demonstrable problem: active caries, a clinical symptom, or restoration failure. Simply being old, its color, or a hypothetical crack is not sufficient reason to remove a healthy restoration.

Frequently Asked Questions

What does RR mean?
RR shows how many times more likely failure is in one group compared with another. A value of 1 means equal. In this study the value was 0.96, meaning there was practically no difference in failure between amalgam and composite.

So which is better — amalgam or composite?
In terms of failure risk in posterior teeth, the latest evidence shows no significant difference between the two. Material choice should depend on other factors — esthetics, cavity size, and patient circumstances — not on a proven superiority of one over the other.

Should I replace my healthy amalgam with composite?
If the amalgam is healthy and asymptomatic, current evidence does not support replacing it as an upgrade. The reason for replacement should be a real problem: active caries, failure, or a symptom.

How much does a crack under an amalgam matter?
A symptomatic crack matters and should be evaluated. But the mere presence of a small, asymptomatic crack is not, on its own, a strong reason to remove a healthy restoration.