Because every implant received both irrigation and L8020, the study cannot determine whether either component produced the disappearance of suppuration. Peri-implantitis is an inflammatory disease affecting the tissues around a dental implant and is associated with progressive bone loss. Suppuration, meaning visible purulent exudate after gentle probing, is a sign of active inflammation.

The single-center study in Japan enrolled adults with an implant affected by peri-implantitis for at least one year and persistent suppuration for at least three months, confirmed within the week before enrollment. All 10 target implants had both bleeding on probing and visible suppuration at baseline. The participants had a mean age of 80.0 ± 7.8 years; seven were women and three were men, and none were current smokers.

One participant had a history of cerebral infarction. When more than one implant met the eligibility criteria, the investigators selected the implant with the longest documented duration of suppuration. The design was prospective, single-arm and open-label, and the sole examiner was not blinded to the intervention.

No formal sample-size calculation was performed because no previous clinical study had examined topical L8020 in peri-implantitis. The target of 10 implants was therefore chosen pragmatically for feasibility and exploratory analysis, and all enrolled patients completed the Day 7 assessment without missing clinical or microbiological data. For treatment, the clinicians first gently irrigated the peri-implant sulcus with 2.5 mL of sterile saline for approximately 10 seconds to remove visible suppuration.

They then applied about 0.3 mL of the L8020 gel circumferentially with a syringe designed for subgingival delivery until slight overflow could be seen. In addition to L8020, the formulation contained dipotassium glycyrrhizinate, potassium nitrate, sodium fluoride and sodium polyphosphate. Participants were instructed not to eat, drink, gargle or use antimicrobial mouthwash for 30 minutes after application.

They continued routine toothbrushing, received no additional nonsurgical or surgical treatment at the target implant, and were prohibited from using systemic or topical antimicrobial agents during the seven-day observation period. The prespecified primary outcome was disappearance of suppuration at Day 7. A single experienced examiner measured probing pocket depth, bleeding on probing and suppuration at six sites around each implant, using the deepest pocket measurement for statistical analysis.

Gentle probing was performed at approximately 0.25 N with a plastic Williams Colorvue periodontal probe. Suppuration was recorded when visible purulent exudate appeared at one or more sites. The investigators explicitly treated disappearance of suppuration as a preliminary short-term observation, not as proof that peri-implantitis had resolved or entered sustained remission.

Mean probing pocket depth was 7.1 ± 1.9 mm at baseline and 7.1 ± 1.9 mm at Day 7, with no change in any individual participant. For microbiome analysis, submucosal plaque was collected before clinical probing by placing sterile paper points in the deepest peri-implant sulcus for approximately 30 seconds. Samples were obtained at baseline and Day 7.

The investigators amplified the V3–V4 region of the bacterial 16S rRNA gene and used paired-end sequencing on an Illumina NextSeq 1000. Within-sample diversity was evaluated with Chao1, Faith’s phylogenetic diversity, observed features, Pielou evenness and Shannon diversity. Overall community structure was assessed through Bray–Curtis principal coordinate analysis and an exact paired PERMANOVA that exchanged baseline and Day 7 labels only within participants, covering all 1,024 possible within-participant permutations.

Genus- and species-level abundance was also examined with paired Wilcoxon signed-rank tests and Benjamini–Hochberg false-discovery-rate correction. None of the five alpha-diversity indices showed a significant paired change: the p values were 0.557 for Chao1, Faith’s phylogenetic diversity and observed features, 0.695 for Pielou evenness, and 0.770 for Shannon diversity. Bray–Curtis principal coordinate analysis showed no distinct separation between baseline and Day 7, and the exact paired PERMANOVA detected no difference in overall community structure (pseudo-F = 0.158; exact p = 0.883).

Genus- and species-level profiles varied substantially between individuals but showed no consistent community-wide shift. Fusobacterium and Porphyromonas were the most abundant genera across the samples, while Porphyromonas gingivalis and Fusobacterium nucleatum subsp. vincentii were among the most abundant taxa at both assessments. No genus or species remained significant after correction across 120 genera and 290 species; the minimum adjusted q value was 1.000.

A complementary LEfSe analysis also found no differential abundance from phylum through species level. These convergent microbiome results mean that the disappearance of suppuration was not accompanied by a detectable major restructuring of bacterial composition, but they do not prove that no microbiological or host-mediated effect occurred. The sequencing method characterized relative bacterial composition rather than bacterial viability, metabolic activity, host inflammatory responses or strain-specific persistence.

The investigators did not use a strain-specific molecular assay to determine whether L8020 remained at the treatment site. Functional activity or immune effects could therefore have occurred without appearing in the taxonomic analysis, yet the available data also do not demonstrate that L8020 altered the microbiota or mediated the clinical observation. The unchanged probing depths further show that the measured change was confined to visible suppuration and was not accompanied by improvement in that structural clinical measure during the short observation period.

Several alternative explanations remain compatible with the results. Saline irrigation could have diluted or removed inflammatory exudate, while direct manipulation of the sulcus could have disturbed biofilm or changed the local wound environment. Spontaneous short-term fluctuation in disease activity is also possible.

Accordingly, the authors describe the seven-day finding as a possible transient remission of suppuration after the combined procedure, not as evidence of an L8020-specific effect. The study’s single-center sample, single-arm open-label design, lack of an irrigation-only or placebo comparator, seven-day follow-up and absence of strain-specific testing limit causal inference and generalizability. An administrative non-compliance also occurred while the principal-investigator position was temporarily vacant; it was formally reviewed, corrective and preventive measures were implemented, and institutional procedures permitted the three affected participants’ data to remain in the analysis.

Within these limits, the procedure was feasible and well tolerated over seven days. The trial selected its short follow-up to examine early clinical and microbiological changes rather than sustained efficacy, and the practical contribution is preliminary information on topical application and short-term safety in a defined group of patients with persistent peri-implant suppuration. Incremental benefit over irrigation alone and cost-effectiveness were not evaluated, so the results do not establish that adding L8020 provides clinical benefit or support routine implementation.

The investigators state that controlled studies with appropriate comparators, larger samples and longer follow-up are required to determine whether any benefit is attributable to L8020, whether disappearance of suppuration persists, and whether clinical or microbiological outcomes improve beyond those produced by irrigation and local manipulation alone.

Subject of Research: Seven-day pilot of topical L8020 after saline irrigation for peri-implantitis with suppuration

Article Title: Short-term clinical observations following local L8020 application in peri-implantitis with suppuration: a pilot study

Article References: Hashimoto, Y., Yasuda, K., Okada, S., Ogino, T., & Tsuga, K. (2026). Short-term clinical observations following local L8020 application in peri-implantitis with suppuration: a pilot study. Frontiers in Oral Health, 7, Article 1967259. https://doi.org/10.3389/froh.2026.1967259

Image Credits: AI Generated

DOI: 10.3389/froh.2026.1967259

Keywords: peri-implantitis, dental implants, L8020, Lactobacillus rhamnosus KO3, suppuration, oral microbiome, 16S rRNA sequencing, pilot study, probiotics, Short-term, clinical, observations