Is Flossing Actually Necessary? What the Evidence Says

Introduction

Few topics in everyday dental care generate as much debate as flossing. You may have seen headlines questioning its value, or perhaps you have quietly wondered whether the effort is genuinely worthwhile. It is a question that many adults ask — is flossing actually necessary, or is brushing alone enough to keep teeth and gums healthy?

The discussion was brought into sharper focus in 2016 when an Associated Press investigation highlighted the limited strength of the clinical evidence supporting flossing, prompting widespread media coverage and considerable public confusion. Since then, the question has remained one of the most commonly searched dental topics online.

Understanding what the evidence actually says — rather than relying on headlines — is important. The answer is more nuanced than a simple yes or no, and it has real implications for how you approach your daily oral care routine.

This article examines the clinical evidence for and against flossing, explains the dental science behind interdental cleaning, explores the alternatives, and offers balanced, practical guidance. As always, individual needs vary, and your dental professional is best placed to advise on the most effective cleaning routine for your specific oral health.

Is Flossing Actually Necessary?

The clinical evidence for flossing is more limited than many people assume, but dental professionals continue to recommend interdental cleaning as part of a thorough oral care routine. Whilst large-scale, long-term randomised trials on flossing are lacking, the underlying principle is well-supported: a toothbrush cannot clean the tight contact points between teeth where plaque accumulates and gum disease often begins. Interdental cleaning — whether with floss, interdental brushes, or other tools — addresses these areas. The most suitable method depends on the size of your interdental spaces and individual dexterity.

Why Interdental Cleaning Matters: The Dental Science

To understand why cleaning between teeth is important, it helps to understand where dental disease most commonly starts.

Tooth Surfaces a Toothbrush Cannot Reach

Each tooth has five surfaces: the front (labial or buccal), the back (lingual or palatal), the biting surface (occlusal), and two interproximal surfaces — the sides of each tooth that face adjacent teeth. These interproximal surfaces account for a significant proportion of total tooth surface area, yet they are the areas a toothbrush — whether manual or electric — cannot effectively access.

How Plaque Causes Problems Between Teeth

Dental plaque — the soft bacterial biofilm that continuously forms on all tooth surfaces — accumulates between teeth just as readily as it does on accessible surfaces. When plaque remains undisturbed in these interproximal spaces, it triggers two key processes:

• Tooth decay (caries) — bacteria in plaque metabolise dietary sugars and produce acids that demineralise enamel. Interproximal decay is one of the most common types of cavity, often detected on dental X-rays before it becomes visible or symptomatic.
• Gum disease (periodontal disease) — plaque that accumulates at and below the gum line between teeth triggers an inflammatory response. This begins as gingivitis (reversible gum inflammation) and, if left unchecked, can progress to periodontitis — involving irreversible loss of the bone supporting the teeth.

The biological rationale for interdental cleaning is therefore clear: removing plaque from between teeth reduces the risk of both decay and gum disease in areas that brushing alone cannot address.

What the Research Evidence Actually Shows

The debate around flossing centres on the quality and strength of the clinical evidence, rather than the underlying biological principle.

What the Studies Found

The 2016 AP investigation highlighted that many studies on flossing had significant limitations — small sample sizes, short durations, and methodological weaknesses. A Cochrane systematic review of flossing studies found:

• Weak to very weak evidence that flossing plus brushing reduces plaque more than brushing alone
• Some evidence that flossing reduces gingivitis (gum inflammation) compared with brushing alone, but the quality of the studies was rated as low
• Insufficient long-term evidence to draw definitive conclusions about the impact of flossing on tooth decay or periodontitis progression

Why the Evidence Is Limited

It is important to understand why this evidence is weak. Conducting rigorous, long-term studies on flossing is inherently challenging:

• Tooth decay and gum disease develop over years, but most flossing studies last only weeks or months
• Participant compliance is difficult to verify — it is hard to confirm whether study participants actually flossed correctly and consistently
• Flossing technique varies enormously — ineffective flossing provides little benefit, which can dilute the apparent effect in study populations
• Ethical concerns — it is difficult to ethically instruct a control group to avoid all interdental cleaning for extended periods

What This Means in Practice

Limited evidence is not the same as evidence of no benefit. The absence of large-scale, long-term trials does not mean flossing is ineffective — it means the specific level of benefit has not been conclusively quantified. The biological plausibility of removing plaque from between teeth remains strong, and clinical experience consistently supports its value.

Why Dental Professionals Still Recommend Interdental Cleaning

Despite the headlines questioning flossing, virtually all major dental professional bodies — including the British Dental Association, the British Society of Periodontology, and the American Dental Association — continue to recommend daily interdental cleaning. There are good reasons for this position.

Clinical Experience

Dental professionals observe the consequences of inadequate interdental cleaning on a daily basis. Patients who do not clean between their teeth consistently tend to present with more interproximal plaque accumulation, higher rates of gum disease, and more frequent interproximal decay compared with those who do. Whilst clinical observation is not the same as controlled trial evidence, it represents decades of professional experience across millions of patient interactions.

The Precautionary Principle

Given the strong biological rationale and the low risk associated with interdental cleaning, dental professionals generally take the view that recommending it is prudent. The potential benefits — reduced plaque between teeth, healthier gums, and lower decay risk — outweigh the minimal time and effort involved. Waiting for definitive trial data before recommending something that is biologically sound and carries virtually no risk would not serve patients' best interests.

The Broader Evidence for Interdental Cleaning

Importantly, the evidence debate is not limited to traditional string floss. Interdental brushes — small, bottle-shaped brushes designed to fit between teeth — have a stronger evidence base than string floss for plaque removal and gingivitis reduction. This has led many dental professionals, particularly in the UK, to recommend interdental brushes as the primary interdental cleaning tool for most patients.

Floss vs Interdental Brushes: Which Is More Effective?

The question of whether to floss or use interdental brushes is an important one, as the evidence suggests they are not equally effective for all patients.

Interdental Brushes

Research consistently shows that interdental brushes remove more plaque from between teeth than string floss, particularly where there is sufficient space for the brush to fit comfortably. A systematic review published in the Journal of Clinical Periodontology concluded that interdental brushes were superior to floss for plaque removal and at least as effective for reducing gingivitis.

Interdental brushes are particularly effective because:

• They conform to the shape of the interproximal space, contacting a larger surface area than a thin strand of floss
• They are easier for most people to use correctly
• They come in multiple sizes to suit different gap widths

String Floss

String floss remains useful in situations where interdental spaces are very tight — typically between teeth that are closely aligned with minimal gaps. In these areas, an interdental brush may not fit, and floss is the most practical option for disrupting plaque at the contact point.

Comparison

The Practical Recommendation

Many dental professionals now suggest using interdental brushes as the primary tool for cleaning between teeth, supplemented by floss for any areas where the brushes do not fit. Your dental hygienist can recommend the correct sizes and demonstrate the most effective technique during a hygiene appointment.

Other Interdental Cleaning Options

Beyond traditional floss and interdental brushes, several other tools can help clean between teeth.

Water Flossers

Water flossers (oral irrigators) use a pressurised stream of water to dislodge food debris and plaque from between teeth and along the gum line. They can be particularly useful for:

• Patients with orthodontic appliances (braces) that make traditional flossing difficult
• Those with dental bridges or implants
• Patients with dexterity limitations who find manual interdental cleaning challenging

The evidence for water flossers suggests they can reduce gingivitis and bleeding, though they may not remove established plaque biofilm as effectively as mechanical tools like interdental brushes. They are best considered as a supplement to, rather than a replacement for, mechanical interdental cleaning.

Floss Picks and Holders

Pre-threaded floss picks can make flossing easier for those who find manipulating string floss difficult. However, they offer less control than standard floss and cannot curve around the tooth surface as effectively. They may be a useful option for occasional use or for patients who would otherwise not clean between their teeth at all.

Soft Rubber Interdental Picks

Flexible rubber picks with soft bristles are a relatively recent addition to interdental cleaning options. Early evidence suggests they may be effective for plaque removal in wider interdental spaces, and many patients find them comfortable and convenient. However, the evidence base is less established than for interdental brushes.

When Professional Dental Assessment May Be Appropriate

If you are uncertain about the most effective interdental cleaning method for your teeth, or if you have noticed changes in your gum health, a professional assessment can provide personalised guidance.

Consider arranging a dental check-up if you experience:

• Bleeding gums during or after brushing or interdental cleaning — whilst some initial bleeding when starting a new interdental cleaning routine is common, persistent bleeding may indicate gum inflammation that warrants assessment
• Bad breath that does not improve despite thorough brushing and interdental cleaning
• Visible plaque or tartar build-up between teeth, despite regular cleaning
• Pain or sensitivity between teeth, which could indicate interproximal decay
• Food regularly trapping between specific teeth — this may suggest a gap or dental issue that needs investigation
• Difficulty cleaning between certain teeth due to tight contacts, crowding, or dental restorations

Your dental hygienist can assess your interdental spaces, recommend the most appropriate tools and sizes, and demonstrate the correct technique. This personalised guidance is far more valuable than any general recommendation, as everyone's teeth and gums are different.

Building an Effective Daily Oral Care Routine

Whether you choose floss, interdental brushes, or a combination, the key is consistency. Here is a practical framework for an effective daily routine.

Morning

• Brush for two minutes with a fluoride toothpaste containing at least 1,350 ppm fluoride
• Clean between your teeth using interdental brushes or floss — doing this before brushing can be helpful, as it loosens plaque that brushing can then remove

Evening

• Clean between your teeth — if you only clean interdentally once daily, doing so before your evening brush is ideal, as it removes the day's accumulated plaque before sleep
• Brush for two minutes with fluoride toothpaste
• Spit, do not rinse — after brushing, spit out excess toothpaste but avoid rinsing with water, to allow the fluoride to remain in contact with your teeth for longer

Additional Tips

• Use a fluoride mouthwash at a different time to brushing — for example, after lunch — to provide extra fluoride exposure without diluting the concentrated fluoride from your toothpaste
• Choose the right interdental brush size — a brush that fits snugly without forcing is ideal. You may need different sizes for different gaps. Your dental hygienist can advise.
• Replace interdental brushes when the bristles become worn — typically every few days to a week, depending on the brand
• Be gentle — whether using floss or interdental brushes, a careful technique avoids traumatising the gum tissue. If you are unsure, ask your dental professional to demonstrate

Key Points to Remember

• Interdental cleaning is an important part of a thorough oral care routine, as a toothbrush cannot reach the surfaces between teeth where plaque accumulates.
• The clinical trial evidence for flossing is limited in quality, but this reflects the difficulty of studying flossing rigorously — not evidence that it has no benefit.
• Interdental brushes have a stronger evidence base than string floss for plaque removal and are recommended as the primary interdental tool by many UK dental professionals.
• String floss remains useful for very tight contact points where interdental brushes do not fit.
• The most effective interdental tool is the one you use correctly and consistently — technique and regularity matter more than the specific tool.
• Your dental hygienist can recommend the best tools and sizes for your individual teeth and demonstrate correct technique.

Frequently Asked Questions

Is it too late to start flossing if I have never done it?

It is never too late to begin interdental cleaning. When you first start, you may experience some bleeding from the gums — this is a common sign of existing gum inflammation responding to the disturbance of plaque that has been sitting undisturbed. In most cases, bleeding reduces significantly within one to two weeks of consistent daily cleaning as the gums become healthier. If bleeding persists beyond two weeks, it is worth mentioning this to your dental professional, as it may indicate gum inflammation that requires further assessment. Start gently and gradually build the habit into your daily routine.

Should I floss before or after brushing?

There is some evidence to suggest that cleaning between teeth before brushing may be slightly more beneficial. This sequence loosens plaque and debris from between teeth, allowing the subsequent brushing to remove it more effectively and enabling fluoride from toothpaste to reach the interproximal surfaces more readily. However, the most important factor is that you clean between your teeth consistently — whether you do so before or after brushing is less critical than doing it at all. Choose the sequence that feels most natural and sustainable for your daily routine.

How do I know which size interdental brush to use?

Interdental brushes come in a range of sizes, typically colour-coded from very small (often pink or orange) to larger (often blue, purple, or grey). The correct size is one that fits snugly between your teeth with gentle insertion — you should feel slight resistance from the bristles but not need to force the brush through. Most people need two or three different sizes because the gaps between their teeth vary. Your dental hygienist can measure your interdental spaces and recommend the appropriate sizes during your next appointment. Using a brush that is too small will not clean effectively; one that is too large may cause discomfort.

Can flossing damage your gums?

When performed correctly with a gentle technique, flossing should not damage healthy gum tissue. However, aggressive flossing — snapping the floss down forcefully between teeth or sawing back and forth against the gums — can cause cuts, soreness, and gum recession over time. The recommended technique involves gently guiding the floss between teeth, curving it around the side of each tooth in a C-shape, and sliding it up and down along the tooth surface. If you find flossing consistently causes pain or bleeding despite a gentle technique, discuss this with your dental professional, as there may be an underlying issue requiring assessment.

Do children need to floss?

Interdental cleaning becomes relevant for children once their teeth are in contact — meaning adjacent teeth are touching and a toothbrush cannot reach between them. This typically begins to occur from around the age of two to three years, though it varies. For younger children, parents or carers should assist with interdental cleaning, as children generally lack the dexterity for effective flossing until around the age of ten or older. Interdental cleaning helps prevent interproximal decay in primary (baby) teeth, which can affect the health and positioning of permanent teeth. Your child's dental professional can advise on when and how to begin.

Are water flossers a good replacement for traditional flossing?

Water flossers can be a useful addition to an oral care routine, particularly for patients with orthodontic appliances, dental bridges, implants, or dexterity limitations. They are effective at dislodging food debris and can help reduce gum inflammation. However, most dental professionals consider them a supplement to mechanical interdental cleaning rather than a direct replacement, as they may not remove established plaque biofilm as thoroughly as interdental brushes or floss. For patients who find traditional interdental cleaning difficult or unpleasant, a water flosser may be better than no interdental cleaning at all. Discuss with your dental professional whether a water flosser is appropriate for your needs.

Conclusion

Is flossing actually necessary? The honest answer is nuanced. The clinical trial evidence for traditional string flossing is weaker than many people assume — but this reflects the inherent difficulty of studying a daily hygiene habit over the long timescales needed to measure outcomes like decay and bone loss. It does not mean that cleaning between teeth has no value.

The biological rationale for interdental cleaning is robust: plaque accumulates between teeth just as it does on accessible surfaces, and a toothbrush cannot remove it. Leaving this plaque undisturbed increases the risk of interproximal decay and gum disease. Whether you use floss, interdental brushes, or a combination, the principle remains the same — disrupting plaque between teeth supports better oral health.

For most adults, interdental brushes are now considered the most effective tool for interproximal cleaning, with floss reserved for very tight contacts. Your dental hygienist is the best person to recommend the right tools and technique for your individual needs.

The most important takeaway is this: consistency matters more than perfection. Cleaning between your teeth daily — even imperfectly — is significantly better than not cleaning between them at all.

Dental symptoms and treatment options should always be assessed individually during a clinical examination.

Disclaimer:

This article is intended for general educational purposes only and does not constitute personalised dental advice. Individual diagnosis and treatment recommendations require a clinical examination by a qualified dental professional.

Next Review Due: 13 March 2027