How do fixed braces and clear aligners differ? Three considerations: force delivery, removability and cleaning

How do fixed braces and clear aligners differ? Three considerations: force delivery, removability and cleaning

Direct answer: Both appliances can effectively achieve orthodontic treatment goals; what differs is the type of case and compliance — in non-extraction cases no significant difference was found in treatment quality or duration, while in extraction cases fixed appliances provided superior treatment quality, attributed to enhanced control of tooth movements [F1]; the advantages of clear aligners for oral hygiene and periodontal health are highly compliance dependent [F2]. That review states the basis for choosing plainly: case complexity and patient compliance [F1]. The final judgement has to be made by a dentist after clinical examination and diagnostic imaging.

Geographic scope: This is general health education based on international literature. It does not cover any particular country's insurance scheme or regulations; for how care and fees are organised, follow the rules where you are. Every source cited in this card is international peer-reviewed literature; no national legislation or insurance-benefit rule is cited.

TL;DR｜The question is not ‘which is better?’, but ‘what is different?’

Comparisons between conventional fixed braces and clear aligners are often framed as a contest. A closer look at the literature, however, shows that both can achieve orthodontic goals in most circumstances, and that the real differences lie in three specific considerations—each of which matters to different people.

First, differences in force delivery become apparent in complex cases. A systematic review and meta-analysis of 15 trials and 1084 patients reported that, in non-extraction cases, there was no significant difference between clear aligners and fixed appliances in treatment quality or duration. In extraction cases, however, fixed appliances provided better treatment quality, attributed to their greater control of tooth movement [F1].

Second, removability is both the greatest advantage of clear aligners and their greatest source of variability. A systematic review that used GRADE to assess certainty of evidence stated its conclusion directly: the oral-hygiene and periodontal-health advantages of clear aligners are highly dependent on adherence to wear [F2]. They can be removed, provided that you put them back in.

Third, findings on cleaning point in a consistent direction, but certainty of evidence differs markedly. A meta-analysis of 11 studies reported significantly better plaque index, gingival index and several other measures in the clear-aligner group [F3]. Yet another systematic review of the same issue using GRADE recorded ‘very low’ certainty of evidence for oral hygiene and ‘low’ certainty for periodontal health [F2]. That gap is itself important information.

The three considerations are examined separately below.

One: force delivery—what differs is the ‘degree of control over movement’

The mechanical basis of the two systems differs

Fixed appliances use brackets bonded to the teeth and connected by an archwire. Deformation of the wire delivers a continuous force, with the point of force application located at the bracket bonded to the tooth surface.

Clear aligners use a series of removable transparent aligners. Deformation of the aligner itself, together with attachments bonded to the teeth, moves the teeth step by step.

A systematic review of the Invisalign system searched MEDLINE, Embase, the Cochrane Oral Health Group's Trials Register and CENTRAL, and also searched ClinicalTrials.gov, the National Research Register and Pro-Quest for unpublished studies. It included 24 studies (15 retrospective, 5 prospective, 2 pilot and 2 case–control studies) [F4]. The review reported that:

• The Invisalign system was considered an effective alternative to conventional orthodontic treatment in non-extraction cases [F4]
• Findings were affected by the methods used to evaluate the effectiveness of the technology, as well as by comparison bias between conventional and innovative digital systems [F4]
• Treatment effectiveness has improved since the introduction of SmartForce and SmartTrack materials [F4]
• High-quality evidence regarding treatment modalities remains lacking [F4]
• More efficient clear-aligner treatment requires appropriate management of ClinCheck software and appropriate application of biomechanics; digital planning should take the aligner's force-delivery system into account [F4]

The final sentence is the technical core of this question: the forces used in clear-aligner treatment are ‘designed’. Their effectiveness depends heavily on the quality of digital planning in advance and on the application of biomechanics, not merely on producing and wearing the aligners.

Where the difference becomes apparent: extraction and non-extraction cases

This is the most important piece of evidence in this discussion and the one that can most directly inform a decision.

A systematic review and meta-analysis comparing the quality and stability of outcomes from clear aligners and fixed appliances searched seven databases (PubMed, Google Scholar, Embase, Scopus, Web of Science, Cochrane CENTRAL and ProQuest) up to February 2025. It included randomised and non-randomised clinical trials, assessed risk of bias using RoB2 and ROBINS-I, and assessed certainty of evidence using GRADE. A total of 15 trials and 1084 patients were included [F1]:

• In non-extraction cases, there was no significant difference between clear aligners and fixed appliances in treatment quality or treatment duration; a sensitivity analysis nevertheless suggested that treatment with clear aligners might be shorter [F1]
• In extraction cases, fixed appliances provided better treatment quality, attributed to their greater control of tooth movement [F1]
• Limited evidence suggested similar post-treatment stability with the two approaches [F1]
• The review concluded that both can effectively achieve orthodontic treatment goals, and that case complexity and patient adherence should inform appliance selection [F1]

In practical terms, if your situation is straightforward and does not require extraction, outcomes are similar and the choice can return to lifestyle considerations. If your situation requires extraction and extensive tooth movement, the literature supports an advantage for fixed appliances in control.

How to interpret this safely: the review recorded varying risks of bias across the studies, while between-study heterogeneity and short follow-up periods limited the strength of the conclusions [F1]. ‘Limited’ in ‘limited evidence suggested similar stability’ is the wording used in the source paper and means that the evidence base for this outcome is weak. In addition, the 24 studies included in 38281057 were predominantly retrospective (15 studies), and that review itself noted that high-quality evidence remained lacking and identified comparison bias between conventional and digital systems [F4]. Existing comparative research is therefore inherently difficult to design as a fair comparison.

Two: removability—the advantage and the source of variability are the same thing

Being removable makes three practical differences: aligners can be removed while eating, while brushing and briefly for an important occasion.

The literature's assessment of this feature, however, comes with one consistent caveat.

‘Highly dependent on adherence’

A systematic review evaluating the effects of clear aligners and fixed appliances on oral hygiene and periodontal health searched four databases—Scopus, PubMed, Web of Science and Google Scholar—for randomised controlled trials published from 2015 to April 2025. Quality was assessed using RoB 2 and certainty of evidence using GRADE. The initial search identified 1098 records, and 6 randomised controlled trials were ultimately included [F2].

The review's dual quality assessment led to the conclusion that the advantages of clear aligners over fixed appliances for oral hygiene and periodontal health were highly compliance dependent [F2].

It is worth pausing over that sentence. The cleaning advantage of clear aligners is not provided automatically by the appliance. It rests on the condition that ‘you wear them as instructed and clean as instructed’. Removability transfers part of the responsibility for treatment to the patient: there is no option to remove fixed appliances, so they cannot be forgotten, whereas both wear and cleaning have to be maintained with clear aligners.

This also echoes the conclusion of the previous section: patient adherence should inform appliance selection [F1]. That is not simply advice; it is one of the selection criteria explicitly identified in the literature.

Differences in how treatment feels

A systematic review and meta-analysis comparing the impact of clear aligners and fixed appliances on oral-health-related quality of life (OHRQoL) followed PRISMA guidance and was registered with PROSPERO. It searched PubMed, Scopus, Web of Science, Embase and Cochrane CENTRAL and included only randomised controlled trials that compared the two treatments and reported OHRQoL outcomes using OHIP-14. Trial sequential analysis (TSA) was used to assess whether the cumulative evidence was sufficient [F5]:

• Only 2 randomised controlled trials (n = 74) were included in the quantitative synthesis [F5]
• Both treatments were associated with a temporary deterioration in OHRQoL after appliance placement [F5]
• For psychological discomfort (p = 0.007) and psychological disability (p < 0.001), the results significantly favoured clear aligners; but no significant difference was found in the other domains or overall OHRQoL [F5]
• The review concluded that clear aligners may provide a modest short-term advantage in the psychological domains of OHRQoL, while no consistent difference was observed in physical or overall domains, and that this conclusion was based on very limited evidence [F5]

How to interpret this safely (the limitations are crucial here): only 2 trials with a total of 74 participants were included in the quantitative synthesis [F5]. The authors explicitly stated in their conclusion that, given the very small number of included trials, the findings should be regarded as preliminary and hypothesis-generating rather than confirmatory [F5]. Trial sequential analysis showed that the required information size had not been reached for most other outcomes, which therefore remained uncertain. For the ‘disability’ domain, the TSA suggested that a clinically meaningful difference was unlikely to exist [F5].

It is also important to note that both treatments produce a temporary deterioration in quality of life shortly after the appliance is fitted [F5]. In the overall and physical domains, this meta-analysis did not support the claim that ‘clear aligners are less painful’.

Three: differences in cleaning—the direction is consistent, but certainty differs greatly

This is the consideration with the most evidence, and also the one that most needs careful interpretation. Two systematic reviews of the same question provide messages of very different strength.

What did the meta-analysis find?

A systematic review and meta-analysis comparing the effects of clear aligners and conventional fixed appliances on periodontal health collected studies from Web of Science, ScienceDirect, PubMed, the Cochrane Library and Google Scholar. Eligibility was determined using PICO criteria, with ROBINS-I used to assess non-randomised controlled trials and ROB used for randomised controlled trials. The meta-analysis included 11 studies [F3]:

• Plaque index: SMD −1.25 (95% CI −1.94 to −0.57; p = 0.0003) [F3]
• Gingival index: SMD −0.68 (95% CI −1.13 to −0.22; p = 0.004) [F3]
• Probing depth: SMD −1.30 (95% CI −2.22 to −0.38; p = 0.006) [F3]
• Sulcus bleeding index: SMD −2.47 (95% CI −4.97 to −0.04; p = 0.05) [F3]
• Papillary bleeding index: SMD −2.47 (95% CI −4.97 to −0.04; p = 0.05) [F3]

The analysis concluded that patients treated with clear aligners had better periodontal health than those treated with conventional fixed appliances, with improvements across several periodontal measures [F3].

How to interpret this safely (each outcome should be considered separately, as they are not all equally robust):

For the first three outcomes—plaque index, gingival index and probing depth—the confidence intervals do not cross 0 and the p values range from 0.001 to 0.006, so the signals are relatively clear.

The final two outcomes, however, need to be highlighted. For the sulcus bleeding index and papillary bleeding index, the 95% confidence interval was −4.97 to −0.04—the −0.04 limit lies very close to 0—and p = 0.05 sits exactly at the conventional threshold for significance. These are therefore highly fragile findings: an extremely wide interval (spanning nearly 5 standardised units) indicates a very imprecise estimate, while the limit close to 0 means that an effect approaching no difference cannot be excluded. These two outcomes should not be treated as robust conclusions.

The analysis also included non-randomised controlled trials (hence the need for ROBINS-I) [F3], exposing the pooled results to the inherent biases of observational research.

What did the GRADE assessment find?

Now consider the review of the same question that used a different assessment framework.

The GRADE systematic review discussed above included only 6 randomised controlled trials from 1098 records, because it was restricted to randomised controlled trials [F2]:

• Qualitative analysis showed significantly better periodontal measures in patients using clear aligners than in patients with fixed appliances [F2]
• However, 5 of the 6 studies had a high risk of bias, and there were widespread inconsistencies in oral-hygiene instruction, age, follow-up duration, diagnosis and measurement methods [F2]
• Certainty of evidence was ‘very low’ for the level of oral hygiene and ‘low’ for periodontal health [F2]
• The review concluded from its dual quality assessment that the advantages of clear aligners were highly dependent on adherence. Yet heterogeneity, high risk of bias and low to very low certainty in the available randomised controlled trials made it difficult to draw a firm conclusion [F2]

How should the two reviews be read together?

The direction is consistent: both point towards better periodontal measures in the clear-aligner group. That direction is plausible and has a physiological rationale—removing the aligners to brush makes cleaning easier.

The strength, however, is not consistent: the meta-analysis presents apparently large effect sizes, such as SMD −1.25, whereas the GRADE assessment rates certainty as low to very low and explicitly states that it is ‘difficult to draw a firm conclusion’ [F2].

Why is this? The inclusion criteria differed. One review included 11 studies, among them non-randomised trials [F3], whereas the other included only 6 randomised controlled trials and found that 5 of them had a high risk of bias [F2]. Broader inclusion produces more impressive pooled figures; stricter inclusion lowers certainty.

The candid account is this: clear aligners may have a cleaning advantage, and the direction of the findings is consistent, but the current evidence is insufficient to quantify how large that advantage is. Moreover, adherence is a precondition for that advantage [F2].

Four: treatment duration and outcome quality—the difference is smaller than many people imagine in most situations

Treatment duration

A systematic review specifically assessed differences in treatment duration between clear aligners and fixed appliances in dental-crowding cases. Without restrictions, it searched nine databases from inception to June 2023 (CENTRAL, PubMed, Scopus, Web of Science, Google Scholar, Trip, CINAHL via EBSCO, EMBASE via OVID and ProQuest). It included randomised controlled trials and matched non-randomised studies, assessed risk of bias with RoB 2 and ROBINS-I, and assessed the overall quality of evidence with GRADE. From 3537 articles initially identified, 10 studies were included, 6 of which were randomised controlled trials [F6]:

• Only 1 study involved extraction treatment; the other 9 involved non-extraction treatment [F6]
• GRADE indicated low-certainty evidence that treatment duration with clear aligners was similar to that with fixed appliances in mild to moderate crowding [F6]
• No meta-analysis was performed because inconsistency was too high [F6]
• The review concluded that, on the available information, there was no significant difference in treatment duration between the groups in mild to moderate crowding, and that well-conducted randomised controlled trials are still needed for severe cases [F6]
• It also cautioned that, although appliance type is an important determinant of treatment duration, orthodontists should consider other factors that can significantly affect treatment duration, including patient-related and treatment-related factors [F6]

How to interpret this safely: this review has a narrow scope—mild to moderate crowding, with almost all cases treated without extraction (only 1 of 10 studies involved extraction) [F6]. Certainty of evidence was low, and inconsistency was too high to permit a meta-analysis [F6]. The review does not answer the question of differences in treatment duration for severe crowding or extraction cases.

The earlier meta-analysis of 15 trials reported no significant difference in treatment duration in non-extraction cases, although a sensitivity analysis suggested that treatment with clear aligners might be shorter [F1]. ‘Suggested by a sensitivity analysis’ means that this was not the primary-analysis result. It is an exploratory finding and carries less weight than the principal conclusion.

Stability of the result

Limited evidence suggests similar post-treatment stability with the two approaches [F1]. ‘Limited’ is the wording used in the source paper, and the review also recorded that short follow-up periods limited the conclusions [F1]. Current comparative studies therefore provide only a thin answer to the question of whether teeth will move back after orthodontic treatment—which also means that the importance of retainers does not change according to the appliance selected.

Five: so how should you choose? The criteria provided by the literature

The literature does not say ‘which is better’, but it does provide criteria for choosing. The meta-analysis of 15 trials gives the clearest conclusion: case complexity and patient adherence should inform appliance selection [F1].

These criteria can be broken down into questions to ask yourself:

Question one: does my case require extraction? If it does, the literature reports that fixed appliances provided better treatment quality in extraction cases because they offer greater control of tooth movement [F1]. This is the clearest current dividing line. If it does not, there is no significant difference in treatment quality or duration [F1], so lifestyle considerations can carry more weight in the choice.

Question two: can I maintain consistent wear? The advantages of clear aligners are highly dependent on adherence [F2]. If you think you are likely to forget to put them back in, removability represents a risk rather than an advantage. Fixed appliances do not have this source of variability.

Question three: how much do I prioritise cleaning? The direction of the evidence favours clear aligners [F3][F2], but the magnitude is uncertain and adherence remains a prerequisite. If your cleaning habits are already less than ideal, either option will require additional oral-hygiene instruction. Incidentally, inconsistency in oral-hygiene instruction was one of the sources of bias identified by the GRADE review [F2].

Each of these three questions ultimately requires a dentist to answer it through clinical and radiographic assessment. The literature above simply helps you know what to ask.

Conclusion｜First establish which type of case you have

The three considerations can be condensed into one sentence: in straightforward non-extraction cases, the difference in outcomes between the two orthodontic approaches is small and the choice can reflect lifestyle; in complex cases requiring extraction or extensive tooth movement, the literature supports an advantage for fixed appliances in movement control.

The strength of evidence differs across the three considerations, so it is worth remembering them separately:

• Force delivery: treatment quality was better with fixed appliances in extraction cases, attributed to their greater control of tooth movement [F1]. This is the clearest of the three distinctions.
• Removability: it provides convenience, but the advantage is highly dependent on adherence [F2]; for quality of life, only preliminary and very limited signals of advantage in psychological domains have been reported [F5].
• Cleaning: findings consistently point towards better outcomes with clear aligners [F3], but GRADE rates certainty as low to very low [F2], so the magnitude cannot yet be quantified.

No single appliance is the right choice for everyone. The decision should be driven not by advertising, but by whether your dental condition requires extraction and whether your lifestyle permits consistent wear.

The next step is simple: have a comprehensive orthodontic assessment, including clinical examination and the necessary imaging, and take these three questions with you. Book a consultation with your dentist or an orthodontic specialist. Establish which type of case you have first, and only then discuss which appliance to use. Reversing that order makes it easy to choose an option that does not suit you.

Risk factors (what to know before treatment)

• The difference in control shows up in complex cases: the systematic review and meta-analysis of 15 trials involving 1084 patients recorded that in extraction cases fixed appliances provided superior treatment quality, attributed to enhanced control of tooth movements; the same review recorded that the risk of bias varied across studies and that heterogeneity and short follow-up durations limited the strength of the conclusions [F1].
• Removability shifts part of the responsibility onto the patient: the GRADE-assessed review concluded that the advantages of clear aligners for oral hygiene and periodontal health are highly compliance dependent; 5 of the 6 randomised controlled trials it included were at high risk of bias, with overall inconsistencies in the oral hygiene instructions given, age, follow-up, diagnosis and measurements [F2].
• Both are uncomfortable when first fitted: the meta-analysis of oral health-related quality of life recorded that both treatments were associated with a transient deterioration in quality of life after appliance placement; the improvements significantly favouring clear aligners were in psychological discomfort and psychological disability, while no significant differences were observed for the other domains or for overall quality of life [F5].
• The direction of the cleaning advantage is consistent, its size is not yet quantifiable: the meta-analysis of periodontal parameters included 11 studies and used ROBINS-I for non-randomised trials, and points towards clear aligners [F3]; but the other review, assessed with GRADE, rated the certainty of evidence as very low for oral hygiene level and low for periodontal health, and stated plainly that outlining a firm conclusion was impeded [F2].
• Check the scope of every conclusion: the review of treatment duration included 10 studies, only 1 of which offered extraction-based treatment, did not perform a meta-analysis because of high inconsistency, and applies only to mild to moderate crowding cases [F6]; the quantitative synthesis on quality of life rested on 2 randomised controlled trials with 74 participants in total, and its authors say the findings should be regarded as preliminary and hypothesis-generating rather than confirmatory [F5]; the review of the Invisalign technique also recorded that its results are influenced by comparison bias between the traditional system and the innovative digital system, and that high-quality evidence is still lacking [F4]. This card did not run a separate literature search on contraindications to orthodontic treatment and therefore does not compile a list of them; which appliance suits you has to be assessed by a dentist after clinical examination and diagnostic imaging.

Every clinical statement in this article is mapped line by line to its cited source (see the sources and evidence chain below). It has not been clinically reviewed by a licensed practitioner. This is health information, not individual advice; assessment by a clinician is required.