Clear aligners vs fixed appliances: what a 2025 meta-analysis tells us about case selection

A patient sits down for their consultation and asks the question every general dentist hears: can you treat me with aligners, or do I need braces? Most clinicians answer with a feel for the case. Some send everything except the most complex to aligners. Others reserve aligners for mild crowding. Personal preference drives many of these decisions because the evidence on direct comparison has been thin for years.

That changed in 2025... or at least tried. A systematic review and meta-analysis published in Cureus in November 2025 (Owayed et al., DOI 10.7759/cureus.96986) pooled seven randomised controlled trials covering 402 patients. Its primary outcome was patient quality of life, measured with the OHIP-14 survey. The finished case comparison we focus on here comes from the study's secondary analysis using the Objective Grading System (OGS). The conclusion sits between the two camps in the aligner debate. Aligners match fixed appliances on several outcomes and outperform them on others, but the headline does not give every case a free pass to aligners.

Clinical risk management starts here. The first step is knowing what the comparison data shows and where it stops. The choice between modalities comes after.

What the 2025 meta-analysis found

The review measured finished cases using OGS scores across alignment, occlusal contacts, occlusal relationships, overjet, interproximal contacts and root angulation. Clear aligners produced better OGS scores on four of these measures: occlusal contacts, occlusal relationships, overjet and the overall composite score. On three measures the two modalities performed comparably: alignment, interproximal contacts and root angulation.

The pattern is worth reading carefully. The advantages cluster around occlusal finishing. The equivalences cluster around basic tooth position. Aligners now hold their own on the outcomes that used to be cited as fixed-appliance territory. The gap clinicians used to feel intuitively has closed on basic tooth position, and on occlusal finishing it has inverted. Universal aligner superiority is not what the review claims, but the burden of proof has shifted.

What the data does not answer

The meta-analysis pooled OGS outcomes across the seven trials. It did not break results down by malocclusion type, severity or specific tooth movements. A clinician planning a Class II subdivision case, a deep-bite correction or a premolar-extraction space closure cannot apply this review directly to that case. The OGS measures finished alignment quality. It does not measure the predictability of difficult movements during treatment.

The literature on individual movement predictability tells a different story. Rotation of canines, intrusion of posterior teeth and root control during space closure remain less predictable with aligners than with fixed mechanics in many studies. The 2025 review does not contradict this. It documents that when aligner cases reach completion, finished quality is comparable to or better than fixed appliance results on the OGS axes measured.

Both pieces of evidence belong in case selection. One tells us aligners can finish to a high standard. The other tells us not every case will get there without explicit auxiliary mechanics, planned anchorage strategies and refinements built into the protocol from day one.

Who treated these cases, and with what aligner experience?

The trials do not say, and that silence matters. The seven RCTs report patient numbers and OGS scores. They do not report how much clear aligner experience the treating clinicians had.

For years, randomised aligner trials have mostly come out of orthodontic departments. Orthodontists are experts in diagnostics, biomechanics and treatment planning. That skill was built on fixed appliances over decades. Their hands-on experience with clear aligners, an appliance that delivers force in a different way, is often far more limited.

A modality performs only as well as the planning behind it. When an operator brings fixed-appliance instincts to a system that rewards different ones, the results reflect the operator as much as the appliance.

There is also a bias in how aligner outcomes get judged. With aligners you see the planned final position on screen before treatment begins. When the case does not reach that exact position without refinements, it reads as a shortfall against the plan. With fixed appliances there is no on-screen prediction to miss, so corrections along the way are simply part of treatment. The same clinical event, an adjustment during treatment, counts as failure in one modality and as routine in the other.

None of this makes the meta-analysis less useful. It sets the frame for reading it. Aligners can finish to a high standard in capable hands, and the hands in these trials were trained mainly on another appliance. The real ceiling for aligner outcomes is set by aligner-specific planning, which is the one variable these trials did not control for.

Where this leaves case selection

Risk-based case selection treats the aligner versus fixed decision as a forecast about predictability rather than a preference about appearance. Three questions structure that forecast.

First, does the case require movements with documented low predictability in aligner studies? Rotation of canines and premolars, intrusion of posterior teeth, true bodily translation in extraction cases. A "yes" does not rule out aligners. It raises the auxiliary mechanics and a potential refinement budget the treating dentist needs to commit to.

Second, are the planned occlusal outcomes the documented strength of aligners on the 2025 OGS data: occlusal contacts and relationships, overjet correction? If yes, the meta-analysis supports the choice.

Third, what is the dentist's experience and the practice's protocol depth for this case type? Patient compliance, attachment strategy and refinement planning sit inside that question. They are the variables that turn a documented modality strength into a clinical result.

The AlignerService Risk Management System™ is built around those questions. Plans are created by dentists and orthodontists only, never technicians, and case selection happens before treatment planning. The order matters. A plan optimised for the wrong modality wastes chair time and produces refinements. A plan grounded in risk-based case selection produces predictable outcomes.

Starting with risk, not guesswork

The 2025 Cureus review is one of the few direct randomised comparisons we have for dentists making the aligner versus fixed appliance decision. It will not answer every case-specific question. No single study can. What it does is shift the conversation. Aligners are no longer the modality that has to defend itself on finishing quality. They have to defend themselves on movement predictability, and that is a case-by-case judgement.

If you have a case where the answer is not obvious, start with a Free Aligner Risk Check. No obligation. No subscription. Just clear clinical feedback from dentists and orthodontists who have delivered 50,000+ treatment plans across 19 countries.

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Kind regards

Jesper Hatt DDS

TPS@AlignerService.com

P: +41 78 268 00 78

AlignerService

AlignerService is a clinical risk management and decision-support partner for dentists working with clear aligner therapy.

We help dentists build realistic, safe and predictable aligner treatments by focusing on what happens before problems arise: diagnostics, case selection, biomechanics and treatment planning. Our work is structured around the AlignerService Risk Management System™, designed to reduce revisions, chair time and late-stage complications.

More than 2,000 dental practices across 20 countries use AlignerService as an ongoing clinical partner. All support is provided asynchronously and in writing by experienced dentists and orthodontists, ensuring continuity, documentation and clinical accountability.

We support dentists working with multiple clear aligner systems, including Invisalign, SureSmile, ClearCorrect, TrioClear, Angel Aligners, Clarity and Spark. AlignerService operates independently of aligner manufacturers, allowing us to focus solely on clinical decision-making and risk reduction.