Key Takeaways
- A new study of 966 co-resident three-generation families in South Korea found that clinically measured periodontitis and caries experience clustered most clearly between grandparents and parents.
- When a grandparent had periodontitis, the adjusted predicted prevalence of periodontitis in the parent generation was 38.7%, compared with 22.9% when the grandparent did not have periodontitis.
- Readers should not interpret the reported adjusted odds ratio of 2.57 as meaning that the parent’s probability of disease was 2.57 times higher.
- The study found only a modest association in cumulative caries experience between the two adult generations, while the parent–offspring and direct grandparent–offspring findings were compatible with no association.
- “Running in families” does not mean that gum disease or tooth decay passes directly from one generation to another through genes.
- Shared diet, smoking, oral-hygiene practices, dental attendance, socioeconomic history, microbial exposures, and genetic susceptibility may all contribute to familial clustering.
- The study included only co-resident South Korean families that researchers could link across three generations, so the results are not nationally representative and may not generalize to other family structures or populations.
- A strong family history can justify earlier assessment and closer prevention, but it does not make periodontitis or caries inevitable.
Introduction
Oral health can show similarities across generations because families may share genetic susceptibility, behaviors, environments, and oral-health routines.
When several relatives lose teeth, develop extensive decay, or require treatment for advanced gum disease, families often reach a simple conclusion: “We just have bad teeth.” A new study published in BMC Oral Health offers evidence that oral disease can indeed cluster within families. It also shows why that familiar explanation can be misleading.
Kim and Cho linked dental examination data from 966 South Korean families in which grandparents, parents, and offspring lived in the same household. The strongest result involved the two adult generations. Parents had greater odds of periodontitis when a biologically linked grandparent also had periodontitis. Caries experience also showed a smaller association between these generations (Kim & Cho, 2026).
These findings matter because the researchers measured oral health clinically rather than relying only on family members’ recollections. However, the study did not identify a gene for “bad teeth,” prove that grandparents transmit disease to their children, or show that oral disease follows an unbroken path through three generations.
In clinical dentistry, I have heard patients describe severe periodontal disease or early tooth loss as unavoidable because the same problems affected their parents. Family history deserves attention, but fatalism can become harmful. The useful question is not whether oral disease runs in a family in some broad sense. It is whether family history can help identify risk early enough to change the outcome.
What Did the Researchers Study?
The researchers used data collected from 2007 through 2018 by the Korea National Health and Nutrition Examination Survey. They linked biologically related family members living in the same household to create grandparent–parent and parent–offspring pairs. The final sample included 966 families and 2,255 linked three-generation chains (Kim & Cho, 2026).
The study examined two different outcomes:
- Periodontitis: The researchers defined disease using a Community Periodontal Index score of 3 or higher, indicating a probing depth of at least 4 mm. Because very few younger participants met this definition, the periodontal analysis included only grandparent–parent pairs.
- Caries experience: The researchers used the DMFT index, which counts permanent teeth that are decayed, missing because of disease, or filled. They analyzed this cumulative measure in both grandparent–parent and parent–offspring pairs.
The models accounted for several measured differences, including age, sex, current smoking, diagnosed diabetes and hypertension, household income, education, household size, urban or rural residence, and survey period. This adjustment makes a simple age or income explanation less likely, but it cannot remove every difference between families or reconstruct decades of earlier exposure.
How Strong Was the Periodontitis Finding?
Among 929 grandparent–parent pairs with complete data, the model linked periodontitis in the grandparent generation to higher odds of periodontitis in the parent generation. The adjusted odds ratio was 2.57, with a 95% confidence interval from 1.85 to 3.57 (Kim & Cho, 2026).
That is a statistically strong association, but the odds ratio needs context. Periodontitis was common in this sample, and odds ratios can make an association appear larger than the corresponding difference in probability. The study’s adjusted estimates provide a more intuitive comparison:
- When the grandparent did not have periodontitis, the predicted prevalence in the parent generation was 22.9%.
- When the grandparent had periodontitis, the predicted prevalence in the parent generation was 38.7%.
This represents a difference of 15.8 percentage points. The authors also calculated an adjusted prevalence ratio of 1.62. Therefore, saying that parents were “2.57 times as likely” to have periodontitis would overstate the result. The accurate wording is that they had 2.57 times the adjusted odds, while the predicted prevalence rose from 22.9% to 38.7%.
The finding remained similar across several sensitivity analyses. That consistency makes the association harder to dismiss as a statistical accident. It still does not establish what caused the similarity.
What Did the Study Find About Tooth Decay?
The caries finding was more modest. In the grandparent–parent pairs, every 10 additional affected teeth in the grandparent’s DMFT score corresponded to a count ratio of 1.18 for the parent’s score. To illustrate the size of the difference, the model predicted that parent DMFT would rise from approximately 5.1 teeth when grandparent DMFT was zero to 7.1 teeth when grandparent DMFT was 20 (Kim & Cho, 2026).
This result suggests some familial resemblance in cumulative caries experience between the adult generations. Yet DMFT combines several different events across a lifetime. A filled tooth can reflect access to restorative care. A missing tooth may have resulted from decay, periodontal disease, trauma, or a treatment decision. Older adults have also had more years in which disease and treatment could accumulate.
The parent–offspring association was weaker, and its confidence interval included the null. A direct grandparent–offspring analysis likewise found no clear association. The researchers could not reliably analyze periodontitis in the offspring generation because too few younger participants met the study’s periodontal definition.
The study therefore does not demonstrate a continuous oral-disease chain running from grandparents through parents to the youngest generation. Its strongest evidence concerns similarity between the two adult generations living together.
Does “Running in Families” Mean Genetic Inheritance?
No. Family clustering can reflect genetic susceptibility, shared environments, learned behavior, or interactions among all three.
Genetic susceptibility appears to contribute to periodontitis, but the size of that contribution depends on how it is studied. A systematic review covering more than 50,000 participants estimated periodontitis heritability at 38% in twin studies, 15% in other family studies, and 29% when the two types were combined. Estimates from genome-wide association studies were considerably lower. In other words, genetics appears to contribute to population differences in periodontitis, but it does not determine an individual patient’s outcome (Nibali et al., 2019).
There is also substantial evidence for genetic susceptibility to dental caries. A study using dental records from up to 41,678 Swedish twins estimated that additive genetic factors accounted for approximately 49% to 63% of variation in caries scores and 50% to 61% of variation in caries trajectories. The researchers also found that genetic contributions differed among patterns of caries affecting different tooth surfaces (Haworth et al., 2020).
These estimates do not mean that 29% of one person’s periodontitis or 60% of another person’s cavities were caused by genes. Heritability describes how much variation in a characteristic within a particular population can statistically be attributed to genetic differences.
Families also share exposures. They may eat similar foods, develop similar oral-hygiene practices, follow similar patterns of dental attendance, and share attitudes toward bleeding gums, tooth loss, and preventive care. Earlier research on intergenerational oral health has emphasized that similarities between generations can reflect interacting genetic, behavioral, environmental, and social influences rather than a single inherited cause (Shearer & Thomson, 2010). Smoking, diabetes, socioeconomic circumstances, fluoride exposure, and access to dentistry can also cluster within families.
Microbial sharing among people living together is another plausible contributor. However, the new South Korean study did not collect microbial samples, so it cannot determine whether relatives shared disease-associated organisms or whether microbial transmission contributed to the observed familial clustering.
Why Did Income and Education Not Explain the Association?
The associations between adult generations changed little after the researchers adjusted for current household income and educational attainment. At first glance, this might suggest that socioeconomic circumstances do not explain familial clustering. That conclusion would go too far.
Current income and education capture only part of a family’s socioeconomic history. They do not fully measure childhood deprivation, accumulated wealth, occupation, insurance coverage, fluoride exposure, neighborhood conditions, previous access to dental treatment, or the cost of maintaining teeth over decades. The authors explicitly acknowledged these limitations (Kim & Cho, 2026).
Educational mobility also provided little clarity. Approximately 79% of the relevant pairs showed upward educational mobility, leaving a small and mixed comparison group. The study therefore lacked enough variation to determine whether upward mobility weakened familial oral-health similarity.
The correct interpretation is narrow: the association persisted after adjustment for the socioeconomic indicators available in this dataset. The study did not eliminate social and economic explanations more broadly.
What Are the Study’s Most Important Limitations?
The first limitation is its cross-sectional design. Researchers measured the generations at one examination rather than following them prospectively. Although grandparents generally developed disease earlier in calendar time, these data cannot establish the sequence of the relevant behaviors, exposures, or clinical changes.
Second, the researchers analyzed a highly selected sample. Of 2,867 households carrying a three-generation composition code, only 960 had a complete linkage across all three generations; researchers added six other fully linked families. Linked households differed from unlinked households in income, size, residence, and survey period. The analysis included only relatives who lived together and participated sufficiently for linkage. These families do not represent all South Korean families, much less families in countries with different diets, dental systems, living arrangements, and social conditions.
Third, co-residence complicates interpretation. Living together makes shared environmental explanations more plausible, but the reasons families live together may also relate to health, caregiving needs, and finances. Selection into a three-generation household may itself influence the observed association.
Fourth, the periodontal measure was imperfect. The Community Periodontal Index uses partial-mouth, sextant-based measurements and does not directly capture full-mouth clinical attachment loss. It can underestimate disease and does not match contemporary epidemiologic case definitions. Extensive tooth loss also made some grandparents impossible to score.
Fifth, the same examination team may have assessed multiple household members during the same session. If an examiner measured pockets or tooth status consistently higher or lower, correlated measurement error could increase the appearance of family resemblance.
Finally, the models could not measure every relevant pathway. The main analysis did not treat toothbrushing and dental attendance simply as confounders because these behaviors may lie on the very familial pathways under investigation. Diet, lifetime fluoride exposure, detailed treatment history, wealth, childhood conditions, and microbiome composition remained incompletely measured or unavailable.
What Does the Study Actually Advance?
The study advances the literature in two important ways. It uses clinical dental measurements rather than relying solely on self-reported family history, and it links three generations within identified biological family relationships. Previous research has documented oral-health similarity between parents and children, including concordance in gingival health (Stormon et al., 2022). Evidence extending to grandparents has been much thinner.
At the same time, the headline should not become stronger than the data. The paper provides evidence of clustering between successive adult generations, not proof of direct inheritance and not confirmation of a single association spanning all three generations. The authors appropriately describe the findings as hypothesis-generating.
The most meaningful advance is therefore methodological and preventive: clinically measured oral-health similarities within families may help identify groups who could benefit from family-centered prevention. Researchers must still test whether acting on that information improves outcomes.
If Gum Disease Is Common in My Family, Am I Destined to Develop It?
No. Family history changes the conversation about risk; it does not determine the ending.
Someone whose parents or grandparents experienced early tooth loss, advanced periodontitis, or extensive decay should tell a dentist. That history may justify a more detailed baseline examination and closer attention to modifiable risks. Useful steps include:
- obtaining a comprehensive periodontal evaluation rather than relying only on whether the gums hurt;
- asking how often periodontal measurements and dental radiographs are appropriate for the individual risk profile;
- controlling plaque with effective daily brushing and interdental cleaning;
- avoiding tobacco;
- managing diabetes with the appropriate medical team;
- limiting the frequency of sugar exposure and using fluoride appropriately;
- treating active disease and maintaining regular professional follow-up; and
- encouraging relatives with signs of disease to obtain their own examinations.
These actions do not guarantee prevention, and the new study did not test any intervention. They are practical responses to potentially elevated risk. Family history should prompt surveillance and prevention, not blame or resignation.
Should Dentists Treat the Family Rather Than Only the Patient?
The study supports exploring family-centered prevention, but it does not prove that a particular family intervention works. A reasonable clinical approach may include asking patients about severe gum disease and early tooth loss in close relatives, discussing shared behaviors, and recommending evaluation for family members when appropriate.
The wording matters. Telling a patient that “your family has bad teeth” can reinforce fatalism and obscure treatable causes. A better explanation is that relatives may share susceptibility and exposures, while each person’s current risk can still change.
From my professional perspective, family history is most valuable when it leads to an earlier examination or a more precise prevention plan. It becomes less useful when clinicians present it as an explanation after disease has already progressed or as a reason to assume that treatment will fail.
What Research Should Come Next?
Researchers should follow diverse families prospectively and include relatives who do not live together. Repeated full-mouth periodontal examinations would better establish when disease develops and how rapidly it progresses. More specific caries measures should separate active untreated decay from past restorations and tooth loss.
Future studies should also measure diet, tobacco exposure, diabetes, fluoride, oral-hygiene behavior, dental attendance, insurance and access, childhood socioeconomic circumstances, and microbial profiles. Genetic data could help distinguish inherited susceptibility from shared household exposure, but researchers would still need to examine gene–environment interaction rather than searching for a single deterministic explanation.
Most importantly, researchers should test whether family-informed screening or prevention actually reduces disease. An association becomes clinically valuable only when clinicians can use it to improve decisions and outcomes.
Final Thoughts
The new South Korean study supports a careful answer to the question of whether gum disease and tooth decay run in families: they can cluster within families, particularly between co-resident adult generations, but the reasons remain mixed and uncertain.
The strongest finding was not that disease inevitably passes from grandparents to parents. It was that parent periodontitis was more common when a linked grandparent also had periodontitis, even after adjustment for several measured characteristics. The study found a smaller adult-generation association for cumulative caries experience and no clear continuous pattern across all three generations.
For patients, family history should function as an early-warning signal rather than a prediction. For dentists, it offers a prompt to ask better questions, examine more carefully, and address modifiable risks before irreversible tissue and tooth loss accumulate.
Frequently Asked Questions
Is Periodontitis Hereditary?
Periodontitis has a heritable component, but genes do not determine the outcome by themselves. Smoking, diabetes, plaque control, access to care, age, and other environmental and behavioral factors interact with susceptibility (Nibali et al., 2019).
Can Parents or Grandparents Pass Gum Disease Directly to Children?
The study did not demonstrate direct transmission. It found associations between relatives living in the same household. Shared genes, behaviors, environments, health conditions, social circumstances, and possibly microbial exposures could all contribute.
What Does an Odds Ratio of 2.57 Mean?
It means that the adjusted odds of periodontitis in the parent generation were 2.57 times as high when a grandparent had periodontitis. It does not mean that the probability was 2.57 times higher. The adjusted predicted prevalence was 38.7% versus 22.9% (Kim & Cho, 2026).
Does a Family History Mean I Will Lose My Teeth?
No. Family history may indicate elevated susceptibility or shared risks, but it does not make tooth loss inevitable. Early periodontal assessment, prevention, risk-factor control, treatment, and maintenance can influence outcomes.
Should My Family Members See a Dentist If I Have Severe Gum Disease?
It is reasonable to encourage close relatives to obtain routine dental and periodontal evaluation, especially if they have bleeding gums, recession, persistent bad breath, loose teeth, or a history of limited dental care. The new study supports attention to family patterns but did not test a screening schedule or family-based intervention.
References
Haworth, S., Esberg, A., Lif Holgerson, P., Kuja-Halkola, R., Timpson, N. J., Magnusson, P. K. E., Franks, P. W., & Johansson, I. (2020). Heritability of caries scores, trajectories, and disease subtypes. Journal of Dental Research, 99(3), 264–270. https://doi.org/10.1177/0022034519897910
Kim, S.-J., & Cho, H.-J. (2026). Familial clustering of clinically measured oral health in co-resident three-generation families: A family-linkage study using KNHANES data. BMC Oral Health. Advance online publication. https://doi.org/10.1186/s12903-026-09825-y
Nibali, L., Bayliss-Chapman, J., Almofareh, S. A., Zhou, Y., Divaris, K., & Vieira, A. R. (2019). What is the heritability of periodontitis? A systematic review. Journal of Dental Research, 98(6), 632–641. https://doi.org/10.1177/0022034519842510
Shearer, D. M., & Thomson, W. M. (2010). Intergenerational continuity in oral health: A review. Community Dentistry and Oral Epidemiology, 38(6), 479–486. https://doi.org/10.1111/j.1600-0528.2010.00560.x
Stormon, N., Clifford, S., Lange, K., Mangoyana, C., Ford, P., Wake, M., & Lalloo, R. (2022). Oral health: Epidemiology and concordance in Australian children and parents. Community Dentistry and Oral Epidemiology, 50(4), 260–269. https://doi.org/10.1111/cdoe.12662
Conflict of Interest
The author declares no conflict of interest relevant to this article.
Funding
The author received no external funding for this article.
