A history of periodontitis was associated with higher odds of peri-implantitis in a retrospective matched study. The model estimated an adjusted odds ratio of 1.93, a comparison of case and control odds after accounting for other retained indicators. Its 95% confidence interval, the range reported around that estimate, ran from 1.25 to 2.99. That is an association, not evidence that periodontitis caused peri-implantitis. The study's cultures were case-only, so they could describe recovered organisms but not show which ones distinguish disease from health.
The records behind the finding
The researchers reviewed clinical, treatment, radiographic, maintenance and laboratory records from consecutive adults who received implant placement or restoration at one institution between June 2021 and June 2025. Screening identified 1,120 adults. After 56 were excluded, 1,064 remained eligible. The final matched cohort included 384 patients: 128 cases and 256 controls without peri-implantitis.
Controls were selected at a 1:2 ratio and matched on index year and observation time. Clinical variables were intentionally not balanced, so residual confounding, meaning other clinical differences affecting the comparison, remained possible.
Cultures found a mixed picture
Among the 128 case episodes, bacterial growth was recovered from 112, or 87.5%. Sixteen episodes, or 12.5%, were culture-negative. Submucosal plaque was the most common primary specimen, present in 54 cases (42.2%), followed by peri-implant crevicular exudate in 46 (35.9%) and purulent discharge in 28 (21.9%). Mixed infections appeared in 40 cases (31.3%).
No single organism predominated. The four most frequent recovered bacterial groups each occurred in 19.6% to 28.6% of culture-positive episodes. Among named findings, Porphyromonas gingivalis was recovered in 28.6% of culture-positive episodes, Fusobacterium nucleatum in 25.0%, Staphylococcus aureus in 21.4% and Escherichia coli in 8.9%.
But these results are a case-only description of organisms that could grow under the study's sampling and incubation conditions. Because the controls were not microbiologically sampled, the frequencies cannot establish which organisms are associated with peri-implantitis relative to health. Conventional culture also did not represent the complete peri-implant microbiota.
The susceptibility results added a separate resistance finding. MRSA was identified in 6 of 24 S. aureus isolates (25.0%), while 20 of 160 isolates (12.5%) met the study's definition of multidrug resistance. These figures are descriptive findings from the case cultures, not a comparison with healthy implant sites.
The clinical signals need caution
The model estimated higher odds with immune-related disorders (adjusted OR 5.84, 95% CI 1.67 to 20.47), higher plaque index (2.78, 1.82 to 4.24), an anodized surface (2.16, 1.41 to 3.32), pre-index occlusal overload (2.08, 1.14 to 3.78) and each additional 20 minutes of surgery (1.14, 1.05 to 1.24). Each additional annual maintenance visit was associated with lower odds (0.80, 0.70 to 0.92).
The immune-related estimate was imprecise because the exposed subgroup was small and heterogeneous. The regression was post hoc, with seven retained indicators and 128 case events; no covariate set or sample-size calculation had been specified in advance, and the model had no internal or external validation.
Missingness ranged from 0% to 6.8%. The researchers used multiple imputation by chained equations to create 20 datasets, and the direction of the effects was similar in complete-case, missing-indicator and culture-positive sensitivity analyses. Those checks were not model validation.
The study's central caution is straightforward: the periodontitis result is an association, while the other clinical estimates are exploratory. Post hoc selection, residual confounding, sparse exposures and the lack of validation limit how confidently the model can be used. The microbiology results likewise cannot support organism-disease associations without samples from healthy implant sites.
Paper data and sources
Original title: Clinical factors associated with peri-implantitis and the culture-based microbiological profile of peri-implantitis cases: a retrospective matched case-control study
Authors: Chai Y, Sun J
Journal/Repository: Frontiers in cellular and infection microbiology
Status: Peer-reviewed
First online: 2026-10-09
DOI: Not available
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