2014Journal of Dental Research
Moynihan & Kelly
55 studies
Cavities were lower when free sugars made up less than 10% of daily calories (moderate-quality evidence). This review informed the WHO sugar guideline.
Read the source ↗Research library · Everyday body care
Teeth and gums: more than a nice smile
Gum disease is common and often painless, and people who have it get more heart disease, stroke and diabetes problems. Whether treating gums prevents those is mostly unproven. What is clear: treating gum disease modestly lowers blood sugar in diabetes, and fluoride, less sugar and good brushing protect your teeth.
Good evidenceUpdated Oct 2026 · 3 new studies−0.43 ptsdrop in HbA1c (long-term blood sugar) 3–4 months after gum treatment in people with diabetesSimpson 2022, Cochrane, 35 trials
−21%less plaque with an electric toothbrush than a manual one after 3+ monthsYaacob 2014, Cochrane, 51 trials
10%of daily calories: keeping free sugars below this means fewer cavitiesMoynihan 2014, J Dent Res, 55 studies
01
The basics
Cavities, gum disease and the rest of the body
Plaque is a sticky film of bacteria that builds up on teeth every day. Sugar feeds bacteria that make acid, which dissolves enamel and causes cavities. Fluoride helps enamel resist acid and repair early damage.
Plaque left at the gum line inflames the gums (gingivitis): red, swollen gums that bleed when you brush. It's reversible. Left alone it can become periodontitis, where the gum pulls away, pockets form and the bone holding the teeth is lost. Smoking and diabetes make it much worse.
Gum disease keeps a low-level inflammation going and lets mouth bacteria into the blood. People with it have more heart disease, stroke and brain changes, but most of that evidence is observational: smoking, diet and access to care drive both. The clearest two-way link is with diabetes: high blood sugar worsens gums, and treating gums modestly improves blood sugar.
Healthy gums versus gum disease
Plaque at the gum line inflames the gum (gingivitis), which is reversible. Left alone, the gap between tooth and gum deepens into a pocket and the bone holding the tooth is lost (periodontitis). Dentists measure pocket depth in millimetres.
02
How it works
From plaque to body-wide inflammation
1
Plaque builds
Bacteria collect at the gum line when cleaning is missed.
2
Gums inflame
Red, puffy gums that bleed: gingivitis, still reversible.
3
Bone is lost
Deep pockets form and the bone that holds teeth wears away.
4
Body-wide effects
Inflammation and bacteria reach the blood, linked to heart disease and poorer blood sugar control.
03
Measure it
Checking your teeth and gums
- Bleeding gums when you brush or floss are the earliest sign of gum disease. They're a reason to clean more carefully, not less.
- Dental check-ups: a dentist can measure gum pockets with a small probe. How often you need a check depends on your risk, from every few months to every 2 years.
- Warning signs: receding gums, bad breath that won't go away, and loose or shifting teeth.
- Higher risk: smokers and people with diabetes should have their gums checked regularly, and tell the dentist about their diabetes.
Try your number
HealthyEarly pocketingGum disease
010
Dentists probe the gap between tooth and gum. 1–3 mm is healthy; pockets of 5 mm or more usually mean periodontitis.
04
What the research says
The key studies
2019Cochrane Database Syst Rev
Worthington et al. (Cochrane)
35 trials, 3,929 adults
Flossing on top of brushing may reduce gum inflammation slightly at one month, and interdental brushes may reduce plaque. Evidence was low certainty, short term, and no trial measured cavities.
Read the source ↗2014Cochrane Database Syst Rev
Yaacob et al. (Cochrane)
51 trials, 4,624 people
Electric toothbrushes removed 21% more plaque and cut gum inflammation by 11% compared with manual brushes after 3 months. Long-term effects on teeth are unclear.
Read the source ↗2022Cochrane Database Syst Rev
Simpson et al. (Cochrane)
35 trials, 3,249 people with diabetes
Treating gum disease lowered HbA1c by 0.43 percentage points at 3–4 months and 0.30 at 6 months (moderate certainty).
Read the source ↗2024Cochrane Database Syst Rev
Iheozor-Ejiofor et al. (Cochrane)
157 studies
Water fluoridation prevented a lot of decay before fluoride toothpaste was common. In studies since 1975 the benefit is much smaller, about a quarter of a decayed baby tooth per child, and uncertain.
Read the source ↗2025Neurology Open Access
Meyer et al. (ARIC)
1,143 adults, average age 77
People with gum disease had more white matter damage on brain scans (56% higher odds of the heaviest burden). A single snapshot, so it can't show cause.
Read the source ↗05
New in 2025–26
What the newest research adds
A large US trial showed a painted-on liquid, silver diamine fluoride, can halt decay in young children's teeth without drilling. Long-term studies keep linking gum disease to stroke, but can't prove cause, and the fluoride and IQ debate rests mainly on high exposures.
The new studies, in order
Every study added to this page since January 2025. Green rings are the strongest evidence: large trials or meta-analyses.
A painted-on liquid that stops cavities
Fontana et al., 2026 (JAMA Pediatrics), 830 children under 6. Share of decayed baby-tooth cavities that had stopped progressing 6 months after one coat.
NewJul 2026JAMA Pediatrics
Fontana et al.
830 children under 6 with severe decay
One coat of silver diamine fluoride stopped decay in 54% of treated baby-tooth cavities at 6 months versus 22.5% with a placebo liquid, with similar side effects. It permanently stains the decayed area dark.
Good evidenceRead the source ↗
NewOct 2025Neurology Open Access
Wood et al. (ARIC)
5,986 US adults, 20 years
Strokes occurred in 4% with healthy mouths, 7% with gum disease and 10% with gum disease plus cavities: 86% higher risk after adjustment. Regular dental visits went with healthier mouths. Observational, with one dental exam at the start.
Good evidenceRead the source ↗
NewJan 2025JAMA Pediatrics
Taylor et al.
74 studies, over 20,000 children
Higher fluoride exposure was linked to lower IQ in children, mainly at water levels above 1.5 mg/L, about twice the US target of 0.7 mg/L. At lower levels results were uncertain. Many studies had high risk of bias and none were from the US.
Good evidenceRead the source ↗
What this changes for you
Keep using fluoride toothpaste twice a day and spit, don't rinse. If your young child has cavities, ask whether silver diamine fluoride is an option. Bleeding gums deserve a dental check, especially if you have diabetes or heart risk.
06
Take action
Protecting your teeth and gums
A few minutes a day prevents most decay and gum disease.
- 1
Fluoride toothpaste twice a day
Brush for about 2 minutes, then spit but don't rinse, so the fluoride stays on your teeth.
- 2
Clean between teeth
Use interdental brushes where gaps allow, or floss, once a day.
- 3
Cut sugary drinks and snacks
Keep sugar to mealtimes and below 10% of calories. Water or milk between meals.
- 4
Consider an electric brush
Trials show a modest edge for plaque and gum inflammation.
- 5
Don't smoke
Smoking is one of the strongest risk factors for gum disease and tooth loss.
- 6
Regular dental checks
Especially if you have diabetes. Treating gum disease helps blood sugar too.
07
Myth or fact
Common myths, checked
✕ MythIf your gums bleed, brush them less.
✓ FactBleeding is a sign of inflammation from plaque. Gentle, thorough cleaning usually stops it.
✕ MythThere's no evidence for cleaning between your teeth.
✓ FactThe evidence is weak but points to less gum inflammation. Interdental brushes are a good choice where teeth have gaps.
✕ MythFluoride toothpaste is dangerous.
✓ FactThe IQ concerns come from high exposures, mainly drinking water above 1.5 mg/L. Toothpaste is spat out; children need only a smear or pea-sized amount.
✕ MythTreating gum disease prevents heart attacks.
✓ FactPeople with gum disease have more heart disease, but no trial has shown that gum treatment prevents heart attacks.
08
Questions
Frequently asked
Is water fluoridation safe?
At the levels used in the US and UK (0.7 to 1 mg/L), no harm to IQ has been clearly shown; a 2025 review found the link mainly above 1.5 mg/L. Mild white flecks on teeth (fluorosis) are common, and at 0.7 mg/L about 12% of people have marks noticeable enough to bother them. The benefit for teeth is smaller today than before fluoride toothpaste.
Electric or manual toothbrush?
Either works if you brush well for 2 minutes. Electric brushes remove a bit more plaque in trials and can help people with poor technique or grip.
Does gum disease affect diabetes?
Yes, in both directions. Treating gum disease lowered HbA1c by about 0.4 percentage points in trials, so it's worth telling your dentist and doctor.
09
Test yourself
True, partly true or myth?
Read each claim and pick an answer: the card flips to show the verdict and why. Not sure? Use “Just reveal”.
Card № 01True or myth?
Treating gum disease can improve blood sugar in diabetes.
True
Treating gum disease can improve blood sugar in diabetes.
A 2022 Cochrane review of 35 trials found HbA1c fell by about 0.4 percentage points within 3–4 months.
Card № 02True or myth?
Gum disease causes heart disease.
Partly true
Gum disease causes heart disease.
People with gum disease have more heart disease and stroke, but the studies are observational and trials haven't shown that treatment prevents them.
Card № 03True or myth?
Flossing is essential for healthy gums.
Partly true
Flossing is essential for healthy gums.
Cleaning between teeth may reduce gum inflammation a little, but a Cochrane review rated the evidence low certainty and short term.
Card № 04True or myth?
Electric toothbrushes remove more plaque than manual ones.
True
Electric toothbrushes remove more plaque than manual ones.
Cochrane found 21% less plaque and 11% less gum inflammation after 3 months, though long-term benefits are unclear.
Card № 05True or myth?
You should rinse your mouth with water after brushing.
Myth
You should rinse your mouth with water after brushing.
Rinsing washes the fluoride away. Spit out the excess toothpaste and leave the rest on your teeth.
Card № 06True or myth?
Fluoride lowers children's IQ.
Partly true
Fluoride lowers children's IQ.
A 2025 review linked fluoride to lower IQ mainly at water levels above 1.5 mg/L, about twice the US target. At normal levels the evidence is uncertain.
Card № 07True or myth?
Keeping sugar below 10% of calories means fewer cavities.
True
Keeping sugar below 10% of calories means fewer cavities.
A review for the WHO found consistent links between free sugars and tooth decay.
Card № 08True or myth?
Bleeding gums are an early sign of gum disease.
True
Bleeding gums are an early sign of gum disease.
Bleeding when brushing usually means gingivitis, which is reversible with better cleaning.
Card № 09True or myth?
A painted-on liquid can stop cavities in children without drilling.
True
A painted-on liquid can stop cavities in children without drilling.
In a 2026 trial, silver diamine fluoride halted 54% of cavities versus 22.5% with placebo, though it stains them dark.
Card № 10True or myth?
Water fluoridation still makes a big difference to tooth decay.
Partly true
Water fluoridation still makes a big difference to tooth decay.
A 2024 Cochrane review found the benefit is much smaller since fluoride toothpaste became common, and uncertain.
Nothing here yet. Try another filter.
10
Sources
References and related topics
- Moynihan & Kelly (2014). Journal of Dental Research. 55 studies. Source ↗
- Worthington et al. (Cochrane) (2019). Cochrane Database Syst Rev. 35 trials, 3,929 adults. Source ↗
- Yaacob et al. (Cochrane) (2014). Cochrane Database Syst Rev. 51 trials, 4,624 people. Source ↗
- Simpson et al. (Cochrane) (2022). Cochrane Database Syst Rev. 35 trials, 3,249 people with diabetes. Source ↗
- Iheozor-Ejiofor et al. (Cochrane) (2024). Cochrane Database Syst Rev. 157 studies. Source ↗
- Meyer et al. (ARIC) (2025). Neurology Open Access. 1,143 adults, average age 77. Source ↗
- Fontana et al. (2026). JAMA Pediatrics. 830 children under 6 with severe decay. Source ↗
- Wood et al. (ARIC) (2025). Neurology Open Access. 5,986 US adults, 20 years. Source ↗
- Taylor et al. (2025). JAMA Pediatrics. 74 studies, over 20,000 children. Source ↗