Why Did the Hospital Keep Making My Dad Brush His Teeth?

Dear Dr. Kaur,

I'm in my late 40s and live in Ahwatukee with my husband, our two teenagers and my dad, who's 76. Flu went through our whole house in late October. Dad's turned into pneumonia, and he spent four days in the hospital. He's home now and recovering, but I've been thinking alot about something the nurses did. They kept making sure he brushed his teeth twice a day and asked whether he sleeps in his partial denture. He does. Was that just about keeping him tidy, or does his mouth really matter for pneumonia? Did his teeth cause this? Should I throw out every toothbrush in the house now that we've all been sick? And what should I be doing for him now, besides worrying?

Gina

Dear Gina,

I'm so glad your dad is home. After those four days, I imagine even an ordinary evening together feels different. The nurses had a reason to pay attention to his mouth. But please don't turn that into a verdict against his teeth, or against yourself.

Gina, daily toothbrushing was associated with less pneumonia in hospital studies, but that does not show that brushing at home prevents flu or pneumonia. Flu itself can lead to bacterial pneumonia; I cannot say his teeth caused it. I would keep brushing for his teeth and gums, without blaming yourself.

How can bacteria from the mouth reach the lungs?

Not just tidiness. Bacteria from the mouth can be aspirated, meaning breathed or slipped down into the lungs, and cause aspiration pneumonia. A review of oral bacteria and respiratory infection described this pathway back in 1999. Dental plaque can provide a place for respiratory germs to settle, something observed in intensive-care and nursing-home patients.

That is a long-proposed, plausible route from mouth to lungs. It doesn't mean every mouth infection travels there, or that we can reconstruct your dad's illness from his brushing habits. A possible pathway and a diagnosis are different things.

The practical question for a hospital is whether helping patients care for their mouths reduces pneumonia acquired there. We now have encouraging trial evidence. It gives the nurses' persistence a purpose beyond having everyone look presentable.

Does brushing teeth help prevent pneumonia in the hospital?

The 2026 HAPPEN trial, published in Lancet Infectious Diseases, involved 8,870 patients at three Australian hospitals. These patients were not on ventilators. The program was introduced in stages, in a randomly assigned order.

It was a package: better delivery of oral care, oral-care products, education for patients and staff, and checks with feedback, delivered by dedicated research nurses. The proportion completing the oral-care routine rose from about 16% to about 62%.

Hospital-acquired pneumonia was uncommon either way: 1.0% with usual care versus 0.7% with the program. The trial's analysis found the program was linked to about a 60% lower rate (a hazard ratio of 0.40). That is a relative reduction in an outcome that was uncommon in both groups.

The authors concluded that improving oral care reduced pneumonia acquired in hospital among patients not on ventilators. Encouraging. But the program had several pieces; it cannot tell us how much benefit came from the toothbrush alone.

A 2024 systematic review and meta-analysis pooled 15 randomized trials involving 10,742 hospitalized adults. Daily toothbrushing was associated with about a third lower rate of hospital-acquired pneumonia. The clearest benefit was among patients on ventilators. For those not on ventilators, the review's result was not statistically significant, with few trials available.

Both reports concern hospitalized patients. Neither establishes that brushing at home prevents flu or pneumonia in healthy people. Nobody has proven that claim.

And the Cochrane nursing-home review found insufficient evidence that professional oral care changed how often pneumonia occurred compared with usual care. The evidence was low certainty, and all included studies had a high risk of bias. We shouldn't quietly carry a hospital result into every other setting.

My view is still to brush. It's cheap, safe and good for teeth and gums. We can value that without promising protection the research hasn't established.

Should your dad sleep with his partial denture in?

This is the home habit I would change, Gina: have him take the partial out at night, clean it, and let his mouth rest. I would also suggest gently brushing his tongue and gums.

A study of denture wearing during sleep followed 524 community-living adults in Japan, all age 85 or older, for up to three years. Sleeping in dentures was associated with about twice the risk of pneumonia. People who slept in them also had more plaque on their tongues and dentures, more gum inflammation and more Candida, a yeast.

This was an observational study. It shows an association, not proof that sleeping in dentures caused pneumonia. Your dad is younger than the people studied, so I would not hand him their risk estimate as his own.

Still, taking the partial out is a simple, inexpensive change I would recommend. It is something useful to do now, without claiming it explains what happened in October. You can read about our denture and partial care; at his visit, I'd want to check how his partial fits.

Should you replace toothbrushes after the flu?

You do not need a household toothbrush purge. The brushes don't all need to be marched to the trash together.

The ADA's toothbrush guidance says to replace brushes about every three to four months, or sooner when bristles are matted or frayed. Rinse thoroughly after each use, and don't share. Brushes can carry bacteria, but ADA says there is no evidence that those bacteria cause adverse health effects.

That page doesn't specifically tell people to replace a brush after illness. My view: if a fresh brush makes you feel better, it's a cheap choice. It isn't something the evidence requires. Please skip the microwave and dishwasher; ADA advises against both.

Dry mouth deserves attention while he's recovering, too. Dehydration can cause it; antihistamines and decongestants can contribute, and mouth breathing can worsen nighttime dryness. ADA suggests sugar-free gum or sugar-free candy and avoiding sticky, sugary foods. I would keep water handy and ask him how his mouth feels.

Here's the small routine I'd suggest:

• •Brush twice a day with fluoride toothpaste and clean between teeth daily.
• •Take the partial out at night, clean it, and gently brush the tongue and gums.
• •Replace a frayed brush or one that's three to four months old, and don't share brushes.
• •Sip water and consider ADA's sugar-free gum or candy advice for dryness.
• •Arrange a dental visit once he's feeling better.

You have enough to manage, I would keep this ordinary and repeatable. The goal is care he can continue, not another reason for you to worry that you missed something.

Which vaccines should you ask his doctor about?

This matters close to home. Maricopa County's 2026-2027 respiratory virus season began October 4, 2026; its dashboards track flu, RSV and COVID-19 with weekly updates. In late October, county health officials speaking to local news reported about five times the average flu cases for that time of year, more like November or December levels. Ahwatukee and Chandler are both in the county.

Ask his physician about his seasonal flu vaccine and the household's vaccination questions. CDC recommends a flu vaccine every season for everyone six months and older, with rare exceptions; antibodies take about two weeks to develop. Also ask whether he is up to date on pneumococcal vaccination. CDC recommends it for all adults 50 and older and some younger adults with certain risk conditions. I don't give vaccines, his doctor can discuss those decisions with him.

For your family, Maricopa County immunization clinics offer seasonal flu and COVID-19 vaccines at all locations free of charge, whether insured, uninsured or under-insured. Appointments are available online or at 602-506-6767.

Once your dad feels up to it, bring him in for a cleaning and exam and a check of his partial's fit. Call Kokopelli Family and Cosmetic Dentistry in Ahwatukee at (480) 283-0733 or Kokopelli Dentistry of Chandler at (480) 895-3252, or request an appointment. Bring his medication list, Gina. We'll start with what his mouth needs now.

Sources

• •1. White NM, Russo PL, Matterson G, et al. Effectiveness of oral care for the prevention of non-ventilator hospital-acquired pneumonia (HAPPEN): a multicentre, stepped-wedge, cluster-randomised trial in Australia. Lancet Infectious Diseases. 2026;26(10):1022-1030. PubMed
• •2. Ehrenzeller S, Klompas M. Association Between Daily Toothbrushing and Hospital-Acquired Pneumonia: A Systematic Review and Meta-Analysis. JAMA Internal Medicine. 2024;184(2):131-142. PubMed
• •3. Cao Y, Liu C, Lin J, et al. Oral care measures for preventing nursing home-acquired pneumonia. Cochrane Database of Systematic Reviews. 2022;11(11):CD012416. PubMed
• •4. Iinuma T, Arai Y, Abe Y, et al. Denture wearing during sleep doubles the risk of pneumonia in the very elderly. Journal of Dental Research. 2015;94(3 Suppl):28S-36S. PMC
• •5. Scannapieco FA. Role of oral bacteria in respiratory infection. Journal of Periodontology. 1999;70(7):793-802. PubMed
• •6. Centers for Disease Control and Prevention. About Influenza. 2026. Link
• •7. Centers for Disease Control and Prevention. Key Facts About Seasonal Flu Vaccine. 2026. Link
• •8. Centers for Disease Control and Prevention. Pneumococcal Vaccination. 2026. Link
• •9. American Dental Association. Toothbrushes. 2026. Link
• •10. American Dental Association. Xerostomia (Dry Mouth). 2026. Link
• •11. American Dental Association. Official ADA Dental Health Recommendations. MouthHealthy. 2026. Link
• •12. Maricopa County Department of Public Health. Respiratory Virus Surveillance. 2026. Link
• •13. Maricopa County Department of Public Health. Immunization Clinics. 2026. Link

Disclaimer: This blog post is for informational purposes only and is not a substitute for professional medical or dental advice, diagnosis, or treatment. Always consult your dentist and physician about flu, pneumonia, vaccines, and treatment options for you or a loved one.

Dr. Harveer Kaur, DDS, BDS

Dr. Kaur is the founder of Kokopelli Dentistry, serving patients in Ahwatukee and Chandler, Arizona. She focuses on family and cosmetic dentistry.

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