⚡Key Takeaways

10 min read

Fluoride toothpaste is the best-proven thing you do for your teeth: brush twice a day with at least 1,350 ppm fluoride, then spit and don’t rinse
Cleaning between teeth probably reduces gum inflammation, but the evidence is low certainty and short-term; interdental brushes may beat floss where they fit
Powered toothbrushes remove somewhat more plaque and reduce gum inflammation more than manual brushing
Antiseptic mouthwash is not a substitute for brushing, stains teeth (chlorhexidine), and in small studies nudged blood pressure up by wiping out nitrate-reducing mouth bacteria
Treating gum disease lowers blood sugar in people with diabetes; the link with heart disease is an association, not proven cause and effect

Oral hygiene advice is a stack of habits handed down with equal confidence: brush, floss, rinse, see the dentist. The evidence behind them is not equal. One of them has some of the strongest prevention data in dentistry. Another made headlines when people noticed how thin its trial record was. A third has a side effect most people have never heard of.

This guide sorts them out: fluoride and how to use it, what the research really says about flossing and interdental brushes, electric versus manual toothbrushes, mouthwash (including the blood-pressure finding), how gum health connects to diabetes and heart disease, and when to see a dentist.

Fluoride: the foundation

Tooth decay happens when mouth bacteria turn sugars into acid that dissolves enamel. Fluoride makes enamel more resistant to acid and helps repair early damage. A Cochrane review of 74 trials involving more than 42,000 children found that fluoride toothpaste reduced new decay by about a quarter compared with non-fluoride toothpaste, with bigger effects at higher concentrations, with more frequent brushing, and with supervised brushing.

A later Cochrane review confirmed that toothpaste of 1,000 ppm fluoride or more prevents decay in children and adults, and that 1,450–1,500 ppm does slightly better than 1,000–1,250 ppm.

How much fluoride, and how

The NHS guidance is a practical summary of this evidence:

Adults and children 7+: toothpaste with at least 1,350 ppm fluoride (1,350–1,500 ppm).
Children 3–6: a pea-sized amount of toothpaste with 1,000–1,500 ppm.
Children under 3: a smear of toothpaste with no less than 1,000 ppm.
Brush twice a day for about two minutes, last thing at night and on one other occasion.
Spit, don’t rinse. Rinsing with water straight after brushing washes away the concentrated fluoride left on the teeth.

That last point has direct support. In a crossover study, fluoride in saliva and in the plaque between teeth — where decay often starts — was highest when people did not rinse after brushing. Rinsing with water after a high-fluoride paste cut saliva fluoride about 2.4-fold, down to roughly the level of an ordinary paste used without rinsing. Look for the fluoride content on the label (often given as sodium fluoride, sodium monofluorophosphate or stannous fluoride with a ppm or percentage). If you are prone to decay, dentists can prescribe higher-strength toothpastes (2,800 or 5,000 ppm).

Young children should be supervised, use only the recommended amount, and spit rather than swallow, because swallowing too much fluoride while adult teeth are forming can cause fluorosis (white marks on the enamel). Fluoride-free toothpastes, including hydroxyapatite formulas, have far less trial evidence behind them than fluoride, and several of their trials were funded by manufacturers.

Flossing and interdental cleaning: the honest evidence

In 2016 news reports pointed out that flossing, recommended for decades, had surprisingly weak trial evidence. The most recent Cochrane review is the best summary of what is known. It pooled 35 trials with nearly 4,000 adults comparing toothbrushing alone with toothbrushing plus floss, interdental brushes, wooden sticks, rubber picks or water irrigators.

Floss plus brushing may reduce gum inflammation (gingivitis) at one, three and six months compared with brushing alone. Effects on plaque were inconsistent.
Interdental brushes may reduce gum inflammation more than floss.
Water flossers and wooden or rubber sticks had limited and inconsistent evidence.
No trial measured decay between the teeth, and most did not measure periodontitis (the destructive stage of gum disease). Most trials were short and in people with little gum disease to begin with, and the overall evidence was rated low to very low certainty.

So the honest position is not “flossing doesn’t work”. It is that cleaning between teeth probably reduces gum inflammation, the long-term benefits have not been tested well, and the device matters less than doing it properly. Short, clean trials of a daily habit over decades are hard to run, and absence of good long-term trials is not evidence of no benefit.

Choosing between floss, brushes and water flossers

Interdental brushes are the first choice where the gaps are big enough. Use the largest size that fits without forcing; many people need two or three sizes.
Floss or tape suits tight contacts where brushes will not go. Curve it around each tooth and slide gently under the gum line, rather than snapping it straight down.
Water flossers are a reasonable option with braces, bridges or implants, or for people with limited hand dexterity, even though the trial evidence is thinner.
Once a day is enough, and the NHS suggests before brushing.

Gums often bleed for the first week or two after you start cleaning between teeth. That is usually inflammation settling, not damage. Bleeding that continues beyond about two weeks of consistent cleaning is a reason to see a dentist or hygienist. The floss reference covers the product types in more detail.

Electric vs manual toothbrushes

A Cochrane review of 56 trials found that powered toothbrushes reduced plaque by about 11% in the short term and 21% after three months, and gum inflammation by 6% and 11%, compared with manual brushing. The largest body of evidence was for rotating-oscillating brush heads. The authors described the clinical importance as unclear, and some of them had previously worked on trials funded by a toothbrush maker.

A good manual technique — soft bristles, angled at the gum line, two minutes, every surface — is fine. A powered brush makes good technique easier, especially with a two-minute timer and a pressure warning, and helps people with arthritis, braces or limited dexterity. Brushing too hard causes gum recession and wear whichever you use.

Mouthwash: what it does and doesn’t do

Antiseptic rinses

Chlorhexidine is the most powerful antiseptic mouthwash. A Cochrane review of 51 trials found it produced a large reduction in plaque, but a small reduction in gum inflammation that the authors did not consider clinically meaningful in people with mild gingivitis. It also caused a large increase in brown tooth staining, and commonly taste changes, mouth soreness and burning. It is useful for short periods when a dentist recommends it (after surgery, or when brushing is impossible), not as a daily habit.

Essential-oil rinses reduced gum inflammation by about 16% and plaque by about 28% over six months in a pooled analysis — but every trial in it was sponsored by industry. Fluoride mouthwashes add some protection against decay for people at high risk. Whatever you use, the NHS advises using mouthwash at a different time from brushing, such as after lunch, so it does not wash away the toothpaste fluoride.

The nitrate and blood-pressure finding

Some mouth bacteria convert nitrate (from leafy greens, beetroot and the body’s own metabolism) into nitrite, which the body turns into nitric oxide, a molecule that relaxes blood vessels. In a study of 19 healthy volunteers, a week of twice-daily antiseptic chlorhexidine mouthwash cut the mouth’s nitrite production by 90% and raised blood pressure by 2–3.5 mmHg. A crossover study of 15 people with treated high blood pressure found a similar rise in systolic pressure after just three days.

These were small, short studies using strong antiseptic rinses, and whether everyday mouthwash use changes long-term blood pressure or heart risk is not known. But they are a reason not to use a strong antiseptic mouthwash routinely without a dental reason, especially if you have high blood pressure. If you monitor your blood pressure, see our guide to measuring blood pressure at home.

Gum disease, diabetes and the heart

Gum disease runs from gingivitis (red, bleeding, reversible) to periodontitis, where the bone and tissue holding the teeth break down. It is linked with several whole-body conditions, but the strength of those links varies a great deal.

Diabetes: the link runs both ways, and here there is trial evidence that treating the mouth helps. A Cochrane review of 35 trials in people with diabetes and periodontitis found that professional deep cleaning below the gum line lowered HbA1c (long-term blood sugar) by about 0.4 percentage points at three to four months — a clinically meaningful amount, rated moderate certainty. If you have diabetes, regular gum checks are part of diabetes care.

Heart disease: people with gum disease have more heart and artery disease, but they also share risk factors such as smoking, diabetes and age. An American Heart Association scientific statement concluded that the association appears to be independent of known confounders, but that the evidence does not show gum disease causes heart disease, and there is no evidence that treating gum disease prevents heart attacks or strokes. Healthy gums are worth having for their own sake; be wary of products that promise heart benefits.

What’s marketing

Charcoal toothpastes and powders. A review found insufficient evidence for their safety or benefit claims, and many contain no fluoride; abrasive powders can wear enamel.
“Detox” and “natural” claims. The ingredient that matters most in a toothpaste is fluoride. Check the ppm.
Whitening. Whitening toothpastes mainly remove surface stains by abrasion or chemical action; they do not change the underlying tooth colour much. Avoid highly abrasive products if you have sensitive teeth or recession.
“Kills 99.9% of germs”. Your mouth is meant to have bacteria, including the nitrate-reducing ones above. Mechanical cleaning and fluoride, not sterilising the mouth, is the goal.

When to see a dentist

⚠️Book a dental visit if

Your gums bleed for more than about two weeks despite regular brushing and interdental cleaning; gums are swollen, receding or pulling away from teeth; a tooth feels loose; you have persistent bad breath or a bad taste; or you have toothache or new sensitivity. See a dentist or doctor about any mouth ulcer, or red or white patch, that has not healed within three weeks, as these need checking for mouth cancer.

⚠️Get urgent care for

Facial or jaw swelling with fever, swelling spreading to the eye or neck, or any difficulty breathing or swallowing. A dental infection can spread and become an emergency.

How often you need routine check-ups depends on your risk: UK NICE guidance ranges from every three months for people with active problems to up to two years for adults with healthy mouths. People with diabetes, who smoke, who have a dry mouth from medications, or who have had gum disease usually need more frequent visits.

Frequently Asked Questions

Is flossing actually necessary?

Cleaning between your teeth probably reduces gum inflammation, though the evidence is low certainty and mostly short-term. It remains standard advice from dental bodies. Interdental brushes are often more effective and easier where they fit; floss is for the tight gaps.

Should I rinse after brushing?

No. Spit out the excess toothpaste and leave the rest. Rinsing with water or mouthwash straight after brushing washes away the concentrated fluoride.

Are electric toothbrushes worth it?

On average they remove a bit more plaque and reduce gum inflammation a bit more than manual brushes. A careful manual brusher can do well; an electric brush with a timer makes it easier to be careful.

Is mouthwash bad for you?

Not in general, but it is not a substitute for brushing, and strong antiseptic rinses used routinely can stain teeth and, in small studies, raised blood pressure. Use a mouthwash for a specific reason, such as fluoride rinse for high decay risk or chlorhexidine short-term on dental advice.

Can gum disease affect my diabetes?

Yes. Treating periodontitis lowered HbA1c by about 0.4 percentage points in trials, a meaningful amount. Tell your dentist if you have diabetes, and your diabetes team if your gums bleed.

The Bottom Line

Fluoride is the backbone: brush twice a day with a 1,350–1,500 ppm toothpaste, spit and don’t rinse. Clean between your teeth once a day with interdental brushes where they fit and floss where they don’t, knowing the evidence is modest but consistent for gum inflammation. An electric brush is a small upgrade. Use mouthwash for a reason, not by habit. If you have diabetes, gum care is part of your blood sugar care. See the toothpaste reference and the personal care learning track for more.

Compare toothpastes, floss and mouthwash on the Formulate personal care shelf →

Flossing and Oral Health: What the Evidence Actually Supports