{"id":581,"date":"2026-09-02T07:17:22","date_gmt":"2026-09-02T07:17:22","guid":{"rendered":"https:\/\/texttoolz.com\/blog\/?p=581"},"modified":"2026-09-02T07:17:22","modified_gmt":"2026-09-02T07:17:22","slug":"composite-vs-amalgam-fillings","status":"publish","type":"post","link":"https:\/\/texttoolz.com\/blog\/composite-vs-amalgam-fillings\/","title":{"rendered":"Composite or amalgam: what does the evidence actually say?"},"content":{"rendered":"<p><strong>The best synthesis of the randomised evidence on this exact comparison ranks eighth of eight on the search that asks it, and not one of the seven pages above it mentions the review.<\/strong> That review, by Worthington and colleagues in the Cochrane Database of Systematic Reviews, found low-certainty evidence that composite restorations had almost double the risk of failure compared with amalgam, in a primary meta-analysis drawn from trials conducted mostly in children, all of which the review itself judged to be at high risk of bias. Five of the eight results are dental practice blogs, three of which publish a lifespan range for each material and none of which attaches a source to it. This page reports what the evidence says and what the other pages say. <strong>It gives no clinical advice and recommends no material<\/strong>, because the choice depends on a tooth nobody writing an article can see.<\/p>\n<h2>What are the two materials?<\/h2>\n<p>Amalgam is a mix of metals, including silver, tin, copper and mercury, with the distinct silver colour everyone recognises. Composite is an acrylic resin carrying a glass or quartz filler, made in shades that match the tooth. Those descriptions are Google&#8217;s AI Overview&#8217;s own wording for this query, and every page on the search agrees with them.<\/p>\n<p>The difference that matters is not the colour. <strong>Composite is bonded to the tooth; amalgam is held mechanically in a cavity shaped to retain it.<\/strong> That single mechanical fact is the reason the tooth-preservation claim exists at all: a bonded material does not need the cavity cut to a retentive shape, so less sound tooth has to be removed to place it. Every other difference the sources discuss follows from the material, and this one follows from how it is held.<\/p>\n<figure class=\"ttz-fig\">\n<img src=\"https:\/\/texttoolz.com\/blog\/wp-content\/uploads\/2026\/08\/ttz-fig-dental-1-materials.png\" alt=\"Three cards describing amalgam as a metal mix held mechanically, composite as a resin bonded to the tooth, and why that difference decides how much tooth is removed\" width=\"1600\" height=\"857\" loading=\"lazy\" decoding=\"async\" style=\"max-width:100%;height:auto;border-radius:12px\"><figcaption>Material descriptions as Google&#8217;s AI Overview gave them on both captures, 25 August 2026.<\/figcaption><\/figure>\n<h2>What does the randomised evidence actually say?<\/h2>\n<p><strong>There is low-certainty evidence that composite restorations had almost double the risk of failure compared with amalgam.<\/strong> The certainty rating belongs in the same sentence as the finding, because the review that produced the finding put it there.<\/p>\n<p>The source is Worthington, Khangura, Seal, Mierzwinski-Urban, Veitz-Keenan, Sahrmann, Schmidlin, Davis, Iheozor-Ejiofor and Rasines Alcaraz, &#8220;Direct composite resin fillings versus amalgam fillings for permanent posterior teeth&#8221;, Cochrane Database of Systematic Reviews, version published 13 August 2021. It includes eight randomised trials. Its primary meta-analysis combines the two parallel-group trials, covering <strong>1,645 composite restorations and 1,365 amalgam restorations in 921 children<\/strong>.<\/p>\n<ul>\n<li><strong>Failure: risk ratio 1.89<\/strong>, 95% confidence interval 1.52 to 2.35, P less than 0.001. Composite restorations failed almost twice as often.<\/li>\n<li><strong>Secondary caries: risk ratio 2.14<\/strong>, 95% confidence interval 1.67 to 2.74, P less than 0.001. New decay at the margin of the filling was substantially more common with composite.<\/li>\n<li><strong>Fracture of the restoration: risk ratio 0.87<\/strong>, 95% confidence interval 0.46 to 1.64, P equals 0.66. The interval crosses 1, so this is no evidence of a difference in either direction.<\/li>\n<\/ul>\n<p>One more line from the review travels with all three: <strong>it judged all eight included trials to be at high risk of bias<\/strong>, because of a lack of blinding and issues with the unit of analysis.<\/p>\n<h3>How much weight do those numbers carry?<\/h3>\n<p>Less than a bare risk ratio suggests, and the review is the source of that caution rather than this page. Low certainty, in the language systematic reviews use, means further research is likely to change the estimate. It is not a reason to ignore the number; it is a reason not to treat it as final.<\/p>\n<p>High risk of bias has a concrete cause here, and it is close to unavoidable. <strong>Nobody can blind a participant, or a dentist, to the difference between a silver filling and a tooth-coloured one.<\/strong> A trial comparing these two materials cannot hide which arm anyone is in, so a source of bias that most drug trials design out is built into this question.<\/p>\n<p>What that adds up to is worth saying plainly. This is the strongest synthesis available on the comparison, and being the strongest available is not the same as being settled.<\/p>\n<h3>Why were the trials mostly in children?<\/h3>\n<p>Because the two parallel-group trials carrying the primary meta-analysis were conducted in children, 921 of them. That is a fact about the evidence base rather than a choice the review made.<\/p>\n<p>What follows from it is narrow. The risk ratios describe permanent posterior teeth in that population, over the follow-up those trials ran. What does not follow is a prediction about an adult molar, and this page does not make one.<\/p>\n<figure class=\"ttz-fig\">\n<img src=\"https:\/\/texttoolz.com\/blog\/wp-content\/uploads\/2026\/08\/ttz-fig-dental-2-riskratios.png\" alt=\"Forest plot of risk ratios for composite compared with amalgam showing secondary caries at 2.14, failure at 1.89 and restoration fracture at 0.87 with its interval crossing the no-difference line\" width=\"1600\" height=\"890\" loading=\"lazy\" decoding=\"async\" style=\"max-width:100%;height:auto;border-radius:12px\"><figcaption>Risk ratios for composite compared with amalgam, with 95% confidence intervals, from the review&#8217;s primary meta-analysis.<\/figcaption><\/figure>\n<h2>Where do the durability numbers come from?<\/h2>\n<p><strong>Three of the five dental practice pages on this search publish a lifespan range, and not one of the three attaches a source to it.<\/strong> Counted from the extracted pages: dentistryofwestbend.com gives amalgam &#8220;10 to 15 years or even longer&#8221;; flagsmiledental.com.au gives &#8220;10 to 15 years or longer&#8221;; califamilydental.com gives &#8220;often lasting 15 years or more&#8221;. All three give composite around five to ten years.<\/p>\n<p>The distinction nothing on this search draws is the one that matters. <strong>A range of years and a relative risk are not the same kind of claim and neither converts into the other.<\/strong> A lifespan range says how long a filling is expected to last. A risk ratio says how much more often one material failed than the other inside a particular set of trials, over their particular follow-up, in their particular population. A reader can hold both and still not have a number for their own tooth.<\/p>\n<p>One figure on the search is easy to misread. drghayoumi.com notes that amalgam has been in use for more than 150 years. That is a history of the material, not a durability claim about a filling, and it sits close enough to the durability discussion to be taken as one.<\/p>\n<figure class=\"ttz-fig\">\n<img src=\"https:\/\/texttoolz.com\/blog\/wp-content\/uploads\/2026\/08\/ttz-fig-dental-3-lifespans.png\" alt=\"Four figures showing three practice pages publishing a lifespan range, none citing a source, no page above the review citing it, and the review ranking eighth of eight\" width=\"1600\" height=\"800\" loading=\"lazy\" decoding=\"async\" style=\"max-width:100%;height:auto;border-radius:12px\"><figcaption>Counted across the eight pages ranking for this query.<\/figcaption><\/figure>\n<h2>Who cites the evidence on this search?<\/h2>\n<p>Nobody above position eight. The Cochrane review is the eighth of eight results, and every result above it, including the StatPearls chapter that ranks first and uses the language of clinical evidence throughout, mentions it nowhere.<\/p>\n<p>That supports one observation and not another. It supports the claim that a reader working down the top results will not meet the randomised evidence on the question they asked. <strong>It does not support any claim about why<\/strong>, and this page makes none: ranking is not a judgement about honesty, practice blogs are written for patients rather than for clinicians, and a systematic review is a hard document to summarise well.<\/p>\n<h3>What the sources say about mercury<\/h3>\n<p>Amalgam contains mercury bound into an alloy with silver, tin and copper, which is the description Google&#8217;s AI Overview and several of the ranking pages give. The National Institutes of Health is named as a source in the AI Overview for the material description.<\/p>\n<p>Beyond that description this page reports rather than concludes. Several pages on the search note that regulators in various jurisdictions have restricted amalgam use for particular groups, and the pages differ in how they characterise the reasoning. <strong>No safety claim is made here in either direction<\/strong>, because nothing in this research would support one, and because the question is settled by regulators and clinicians rather than by an article.<\/p>\n<h3>What the sources say about replacing fillings you already have<\/h3>\n<p>The pages on this search that address it do not recommend replacing sound amalgam fillings for appearance alone, and they give a mechanical reason: removing an existing filling takes tooth structure with it, and the replacement is larger than the original.<\/p>\n<p>That is their position, reported as theirs rather than endorsed here. The mechanical point behind it is checkable and worth keeping: a replacement cavity is necessarily at least as large as the one it replaces, because the old material has to come out before the new one goes in, and any sound tooth removed in the process does not grow back. Whether a specific filling should be replaced depends on that filling, that tooth and that patient. The person who can examine it decides, and nothing in the evidence above changes that.<\/p>\n<h2>So which one should you have?<\/h2>\n<p><strong>This page will not answer that, and the reason is more useful than the refusal.<\/strong> No source in this research supports naming a healthiest filling. The strongest evidence available is rated low certainty by the people who assembled it, comes from trials in children, and covers permanent posterior teeth rather than every restoration a dentist places. The choice depends on where the cavity is, how much tooth is left, what the patient can tolerate and what the local regulations allow, and none of those is visible from here.<\/p>\n<p>What a reader can take from the evidence is a set of questions rather than an answer. What is the failure mode this material is being chosen against, decay at the margin or fracture. How much sound tooth has to be removed for each option in this specific cavity. What follow-up would show the filling is failing, and when. Those are answerable by someone looking at the tooth.<\/p>\n<p>This article was commissioned by <a href=\"https:\/\/newgisbornedentalhouse.com.au\/services\/fillings\/\" target=\"_blank\" rel=\"noopener nofollow\">New Gisborne Dental House<\/a>, whose fillings page is linked here. Nothing in this article evaluates their practice, describes their work or claims a result for them, and none of the evidence above involves them.<\/p>\n<h3>Why there is no price in this article<\/h3>\n<p>No page on this search publishes a price that survives being checked, and dental fees vary by jurisdiction, by practice and by how much of the tooth is involved. A figure invented to fill that gap would be worth less than the gap.<\/p>\n<p>The number that answers the question is a quote for the specific tooth, and it comes from the practice that would place the filling. Two things move it that an article cannot see: how much of the tooth is left, which decides whether a filling is even the right restoration rather than an onlay or a crown, and which surfaces are involved, since a filling touching two or three surfaces is not priced like one touching a single surface. A published average would obscure both.<\/p>\n<h2>Questions people ask about this<\/h2>\n<p>These are the four questions Google served in its People Also Ask box for this query, identically on both captures taken on 25 August 2026. Each answer below reports evidence or reports a source.<\/p>\n<h3>What is the healthiest type of filling?<\/h3>\n<p>No source in this research names one, and this page does not either. The Cochrane review compares failure and secondary caries between two materials and rates its own evidence low certainty; it does not rank materials by health. Several pages on the search discuss mercury content and regulatory restrictions, and they differ in how they characterise the reasoning. A question about health rather than durability belongs to a clinician and a regulator.<\/p>\n<h3>What are the disadvantages of composite fillings?<\/h3>\n<p>The measured one, from the Cochrane review, is a higher rate of failure and of new decay at the margin: risk ratio 1.89 for failure and 2.14 for secondary caries, both low certainty and both from trials mostly in children. The review found no evidence of a higher fracture risk. The practice pages add a shorter published lifespan range, around five to ten years against ten to fifteen, without citing a source for either figure.<\/p>\n<h3>Can I replace my amalgam fillings with composite?<\/h3>\n<p>The pages on this search that address it do not recommend replacing sound amalgam fillings for appearance alone, because removing an existing filling takes sound tooth with it and the replacement ends up larger. That is their position rather than a recommendation from this page. Whether a particular filling should be replaced is a decision for the dentist who can examine it.<\/p>\n<h3>Does amalgam last longer than composite?<\/h3>\n<p>Two different kinds of answer exist and they are often confused. The practice pages publish longer lifespan ranges for amalgam, ten to fifteen years or more against five to ten, with no source attached. The Cochrane review measured something else: composite restorations failed almost twice as often as amalgam in its primary meta-analysis, risk ratio 1.89 with a 95% confidence interval of 1.52 to 2.35, low certainty, in children. The first is an expectation; the second is a comparison inside a set of trials. Neither is a figure for one particular tooth.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The best synthesis of the randomised evidence on this exact comparison ranks eighth of eight on the search that asks it, and not one of the seven pages above it mentions the review. That review, by Worthington and colleagues in the Cochrane Database of Systematic Reviews, found low-certainty evidence that composite restorations had almost double [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":577,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-581","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/posts\/581","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/comments?post=581"}],"version-history":[{"count":1,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/posts\/581\/revisions"}],"predecessor-version":[{"id":582,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/posts\/581\/revisions\/582"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/media\/577"}],"wp:attachment":[{"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/media?parent=581"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/categories?post=581"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/texttoolz.com\/blog\/wp-json\/wp\/v2\/tags?post=581"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}