According to Gram Research analysis, two probiotic strains—L. rhamnosus LR-04 and L. acidophilus LA-14—significantly boosted immune markers in infected tooth tissues in a 24-rat study, with L. acidophilus showing the strongest effect on natural infection-fighting proteins. The probiotics increased hBD-2 and hBD-3 expression by activating TLR4, the body’s infection-detection system, without causing liver damage. However, this is early animal research; human studies are needed before probiotics can be recommended as a dental infection treatment.
Researchers tested whether two types of probiotics could help the body’s immune system fight apical periodontitis, a serious tooth root infection. In a study with 24 rats, they gave some animals probiotics while others received only water. After 30 days, the rats receiving probiotics showed stronger immune responses in their infected tooth tissues, with increased production of natural infection-fighting proteins. The good news: the probiotics didn’t damage the liver or cause other harmful side effects. This suggests that probiotics taken by mouth might help your body’s natural defenses against dental infections.
Key Statistics
A 2026 animal study of 24 rats found that systemic probiotic supplementation with L. acidophilus LA-14 significantly increased hBD-3 immune protein expression in infected tooth tissues compared to control groups (P<0.05), suggesting enhanced local immune response to apical periodontitis.
According to research reviewed by Gram, both L. rhamnosus LR-04 and L. acidophilus LA-14 probiotics increased TLR4 expression—the body’s infection-detection protein—in periapical lesions compared to untreated controls in a 24-rat model, with no detectable liver damage in any group.
A 2026 rat study demonstrated that oral probiotic supplementation enhanced hBD-2 immunoreactivity in periapical tissues significantly more than water controls (P<0.05), indicating probiotics may support natural antimicrobial defenses in tooth root infections.
In a 24-rat experimental model, systemic probiotics increased multiple immune markers (TLR4, hBD-2, and hBD-3) in infected tooth tissues without causing hepatic histopathological alterations, suggesting probiotics may modulate immune response safely in apical periodontitis.
The Quick Take
- What they studied: Whether taking probiotics by mouth could boost the body’s immune response to apical periodontitis, a serious infection at the tip of a tooth root.
- Who participated: 24 male laboratory rats divided into three equal groups. One group had the infection and received water, while the other two groups had the infection and received different types of probiotics daily for 30 days.
- Key finding: Rats that received probiotics showed significantly stronger immune responses in their infected tooth tissues compared to the control group, with higher levels of natural infection-fighting proteins called hBD-2 and hBD-3, plus increased TLR4 immune markers (P<0.05).
- What it means for you: This early research suggests probiotics might help your body fight serious tooth infections naturally, but human studies are needed before doctors can recommend this treatment. Don’t replace professional dental care with probiotics—always see a dentist for tooth infections.
The Research Details
This was an animal study using 24 laboratory rats to test how probiotics affect the immune system’s response to tooth root infections. The researchers created an infection by leaving the inside of a tooth exposed for 30 days, mimicking what happens with untreated cavities. They divided the rats into three groups: one received only water (control), one received L. rhamnosus LR-04 probiotics, and one received L. acidophilus LA-14 probiotics. All groups received their assigned treatment daily by mouth for the full 30 days.
After the study ended, researchers examined the infected tooth tissues under a microscope to measure three specific immune markers: TLR4 (a protein that detects infections), hBD-2 (a natural antibiotic protein), and hBD-3 (another natural antibiotic protein). They also examined liver tissue to make sure the probiotics didn’t cause damage. The researchers used statistical tests to determine if differences between groups were real or just due to chance.
This research approach matters because it tests whether probiotics work at the local level—directly in infected tissues—rather than just in the gut. By measuring specific immune proteins, the study shows exactly how probiotics might help the body fight infections. Testing liver safety is important because any supplement that enters the bloodstream could potentially affect the liver, so this study confirms probiotics don’t cause that problem.
This is a controlled animal study, which is a solid first step in research but has limitations. The study used proper randomization (random assignment to groups) and measured specific immune markers objectively. However, animal studies don’t always translate to humans—rats’ immune systems work differently than ours. The sample size of 24 is reasonable for an animal study but relatively small. The study was published in a peer-reviewed journal, meaning other scientists reviewed it before publication.
What the Results Show
The main finding was that both probiotic strains significantly boosted the body’s local immune response to tooth infections. Rats receiving L. rhamnosus LR-04 showed higher levels of hBD-2, a natural antibiotic protein, compared to the control group. Even more impressive, rats receiving L. acidophilus LA-14 showed the highest hBD-3 levels—another infection-fighting protein—compared to both other groups.
Both probiotic groups also showed increased TLR4 expression, which is like turning up the volume on the body’s infection alarm system. TLR4 is a protein that detects harmful bacteria and triggers immune responses. This suggests the probiotics helped the body recognize and respond to the infection more effectively.
Crucially, the liver tissue from all groups looked completely normal under the microscope. Researchers found no inflammation, cell death, scarring, or other damage in any group, meaning the probiotics didn’t cause harmful side effects in this important organ.
The study found that L. acidophilus LA-14 appeared slightly more effective than L. rhamnosus LR-04 at boosting hBD-3 production, though both probiotics improved the immune response. This suggests different probiotic strains may have different strengths. The fact that the immune response was local—concentrated in the infected tooth tissues—rather than causing widespread inflammation is also important and suggests a targeted, beneficial effect.
This research builds on earlier studies showing that probiotics can influence immune function. Previous research has shown probiotics can affect immune markers in the gut and mouth, but this study is among the first to specifically measure how systemic probiotics (taken by mouth, entering the bloodstream) affect immune response in deep tooth infections. The findings align with growing evidence that probiotics can modulate—or adjust—how the immune system responds to infections, rather than simply killing bacteria directly.
This study has several important limitations. First, it was conducted in rats, not humans, so results may not directly apply to people—our immune systems are more complex. Second, the study only lasted 30 days, so we don’t know if benefits continue longer or if problems develop over time. Third, the study didn’t measure whether the infection actually improved or if teeth were saved—only that immune markers increased. Fourth, the study didn’t test different probiotic doses or compare probiotics to standard dental treatments. Finally, with only 24 animals total, the study is relatively small, though appropriate for initial research.
The Bottom Line
Based on this animal research, probiotics show promise as a potential support for the immune system in fighting tooth infections, but human studies are needed before clinical recommendations can be made. Current evidence is moderate—this is early-stage research. If you have a tooth infection, professional dental treatment (root canal, antibiotics, or extraction) remains the standard of care. Probiotics might potentially be used alongside professional treatment, but only under dental supervision. Do not delay or avoid dental care based on this research.
This research is most relevant to dentists and dental researchers exploring new ways to support immune function in tooth infections. People with recurrent tooth infections or those interested in natural immune support might find this interesting, but should not change their dental care based on this single animal study. People with liver disease or compromised immune systems should consult their doctor before taking probiotics, though this study found no liver damage.
In this rat study, immune changes were measurable after 30 days. If similar effects occur in humans, you might expect to see changes over weeks to months, but this is speculative. Professional dental treatment typically shows improvement within days to weeks. Any benefits from probiotics would likely be gradual and supportive rather than a quick fix.
Frequently Asked Questions
Can probiotics help treat a tooth infection or root canal problem?
This rat study suggests probiotics may support immune response to tooth infections, but human evidence is lacking. Probiotics should not replace professional dental treatment like root canals or antibiotics. Always see a dentist for tooth infections—probiotics might be a supportive addition only under professional guidance.
Which probiotic strains are best for dental health?
This study tested L. rhamnosus LR-04 and L. acidophilus LA-14 specifically, with L. acidophilus showing slightly stronger immune effects. However, this is one animal study. Different strains may work differently in humans. Talk to your dentist about which probiotic strains have the most research support for oral health.
Are probiotics safe for your liver and overall health?
This study found no liver damage from the probiotics tested, which is reassuring. However, this was a 30-day animal study. Long-term human safety data is limited. Most people tolerate probiotics well, but those with compromised immune systems or liver disease should consult their doctor before starting probiotics.
How long do you need to take probiotics to see benefits for tooth infections?
In this rat study, immune changes were measurable after 30 days of daily probiotics. Human timelines are unknown. If probiotics help at all, benefits would likely develop over weeks to months, not days. Professional dental treatment works much faster and should remain your primary approach.
Can probiotics prevent tooth infections from happening?
This study only tested probiotics in rats that already had infections—it didn’t examine prevention. Whether probiotics prevent infections in humans is unknown. Good oral hygiene, regular dental checkups, and avoiding cavity-causing behaviors remain the proven prevention methods.
Want to Apply This Research?
- If using probiotics as part of dental health support, track daily probiotic intake (type, strain, CFU count) and any changes in tooth sensitivity, swelling, or infection symptoms. Note any dental visits or professional treatments. Rate overall oral health weekly on a 1-10 scale.
- Users could set a daily reminder to take probiotics at the same time each day, log which probiotic strain they’re using, and note any changes in gum health or tooth symptoms. Connect this to dental appointment reminders to ensure professional care isn’t neglected.
- Track probiotic consistency over 8-12 weeks while monitoring for any changes in oral health symptoms. Create a simple log noting probiotic type, daily adherence, and any dental issues. Share this data with your dentist at regular checkups. Don’t rely solely on app tracking—professional dental evaluation is essential.
This research was conducted in laboratory rats and has not been tested in humans. Apical periodontitis is a serious dental condition requiring professional evaluation and treatment by a dentist or endodontist. Probiotics should not be used as a substitute for professional dental care, root canal therapy, antibiotics, or other standard treatments. While this study found no liver damage from the probiotics tested, long-term safety in humans is not established. Consult your dentist before using probiotics for any dental condition, especially if you have a compromised immune system, liver disease, or are taking medications. This article is for educational purposes only and does not constitute medical or dental advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.