Microbiological and Clinical Effects of Pre- and Probiotics in Non-Surgical Periodontal Therapy (PROPARO)

February 24, 2026 updated by: Diana Wolff, University Hospital Heidelberg

Periodontitis is a prevalent chronic inflammatory disease driven by a dysbiotic oral biofilm and a dysregulated host immune response. Standard non-surgical periodontal therapy (NSPT) is primarily mechanical and, in selected cases, may be accompanied by antiseptics or systemic antibiotics. Targeted modulation of the oral microbiome ("microbiome engineering") is currently not part of routine periodontal care due to limited high-quality evidence.

PROPARO is a single-center, randomized, controlled pilot study designed to assess whether adjunctive oral supplementation with a probiotic containing Limosilactobacillus reuteri (commercial dietary supplement lozenge) alone or combined with vitamin B12 (commercial dietary supplement drops) is associated with changes in supragingival and subgingival oral microbiome composition during guideline-concordant NSPT compared with standard care alone. Participants with Stage III or IV periodontitis will be randomized 1:1:1 to: (1) NSPT/SPT without supplementation (control), (2) NSPT/SPT plus probiotic lozenges for 3 months, or (3) NSPT/SPT plus probiotic lozenges and vitamin B12 drops for 3 months.

The primary outcome is change in oral microbiome composition and structure (supragingival and subgingival), assessed using 16S rDNA-based profiling and metagenomic sequencing approaches. Secondary outcomes include clinical periodontal parameters (e.g., probing depth, clinical attachment level, bleeding on probing), oral hygiene/gingival indices, dental status, and participant-level ecological covariates (diet quality, perceived stress, physical activity). Sampling and assessments are aligned with routine care time points from baseline through supportive periodontal therapy follow-up (up to 12 months). This pilot trial aims to generate feasibility and effect-size estimates to inform future confirmatory studies and potential translation into guideline-based periodontal care.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Background and rationale:

Periodontitis is a chronic inflammatory disease characterized by periodontal pocketing, bleeding on probing, and progressive loss of periodontal supporting tissues, potentially resulting in tooth loss and impaired oral function. The disease is initiated and sustained by a dysbiotic biofilm in combination with an exaggerated or dysregulated host response. Current guideline-concordant non-surgical periodontal therapy (NSPT) targets biofilm removal by mechanical debridement and risk-factor control. Although antiseptics or systemic antibiotics may be used in selected indications, routine, targeted manipulation of the oral microbiome is not established because available evidence is heterogeneous and mechanistic data on whole-community changes remain limited.

Probiotics are live microorganisms that may confer health benefits when administered in adequate amounts. In periodontitis, adjunctive probiotic approaches-especially involving Limosilactobacillus reuteri-have been associated in some studies with improved clinical outcomes and/or reductions in selected periodontal pathogens. Prebiotics are substrates selectively utilized by microorganisms that may provide a growth or functional advantage. Vitamin B12 has been discussed as a potentially supportive factor for specific bacterial metabolic functions. However, the combined adjunctive use of a probiotic and a prebiotic-acting supplement within NSPT has not been comprehensively evaluated using community-level oral microbiome endpoints (supragingival and subgingival) in a controlled clinical setting.

Study objective:

The main objective of PROPARO is to assess whether adjunctive oral supplementation with a probiotic containing L. reuteri-alone or combined with vitamin B12-modifies the composition and structure of the oral microbiome (supragingival and subgingival) during NSPT and follow-up supportive periodontal therapy (SPT), compared with NSPT/SPT alone.

Study design:

PROPARO is a single-center, randomized, controlled pilot study with three parallel arms (allocation 1:1:1). The trial is designed as a feasibility and hypothesis-generating study. Clinical outcome assessment is intended to be single-blinded (outcome assessor) where operationally feasible; participant blinding is not possible due to distinguishable dosage forms and the absence of placebo.

Setting:

Recruitment and study procedures are conducted at Heidelberg University Hospital, Department of Conservative Dentistry (Poliklinik für Zahnerhaltungskunde), within routine periodontal care workflows.

Participants:

Adults (≥18 years) with diagnosed localized or generalized periodontitis, Stage III or IV, scheduled for NSPT are eligible. Key exclusions include pregnancy or breastfeeding; recent antibiotic use; recent use of pre-/probiotic supplements; recent subgingival instrumentation; conditions or medications expected to substantially confound oral microbiome composition or periodontal healing (e.g., relevant systemic immunosuppression); and other protocol-defined factors that may impair safety, consent validity, or interpretability of microbiome outcomes.

Interventions:

All participants receive guideline-concordant NSPT and follow-up supportive periodontal therapy (SPT/UPT), including oral hygiene instruction and professional care as per standard practice.

Arm 1 (Control): NSPT/SPT without supplementation. Arm 2 (Test A - Probiotic): NSPT/SPT plus a commercially available probiotic lozenge containing L. reuteri (dietary supplement; GUM® PerioBalance®, Sunstar Deutschland GmbH, Schönau, Germany), taken according to manufacturer instructions for 3 months starting with NSPT.

Arm 3 (Test B - Probiotic + Vitamin B12): NSPT/SPT plus the same probiotic regimen and commercially available vitamin B12 drops (dietary supplement; natural elements GmbH, Düsseldorf, Germany), administered according to manufacturer instructions for 3 months.

Concomitant care is standardized as far as feasible within routine practice (e.g., standardized toothpaste provided for home use). Participants are asked to avoid additional antimicrobial adjuncts (e.g., antiseptic mouthrinses) unless clinically required; any such use is documented.

Outcome measures:

Primary outcome: Oral microbiome composition and structure (supragingival and subgingival), including community-level measures (e.g., diversity metrics and community dissimilarity) and relative abundance profiles of microbial taxa/features. Microbiome profiling will be performed using 16S rDNA-based methods, with metagenomic sequencing approaches used to provide higher-resolution taxonomic and functional information where applicable.

Secondary outcomes: Periodontal clinical parameters (e.g., probing depth, clinical attachment level, bleeding on probing), additional oral indices (e.g., plaque control and gingival bleeding indices), dental status (DMFT), and participant-level ecological covariates that may influence microbiome composition (diet quality, perceived stress, physical activity). Demographic and socioeconomic information is collected to contextualize analyses and feasibility.

Timing of assessments and sampling:

Clinical assessments, questionnaires, and biospecimen collection (supragingival plaque, subgingival plaque, and unstimulated saliva) are obtained at standardized time points aligned with routine care: baseline and NSPT-related visits, re-evaluation/first SPT visit (~3 months), and subsequent SPT follow-up visits (up to ~12 months). The study is designed to minimize burden and avoid procedures beyond standard clinical practice, focusing on documentation and analysis of microbiological and clinical parameters during standard care.

Sample size:

This is a pilot study; robust effect-size estimates for the primary microbiome endpoints under the specific combined supplementation strategy are not available. Therefore, formal power calculation is not feasible. A total of 60 participants (20 per arm) is planned to assess feasibility (recruitment, adherence, completeness of sampling) and to generate preliminary effect-size estimates to inform a future confirmatory trial.

Randomization and allocation concealment:

Participants are randomized using stratified block randomization to support balanced group allocation (e.g., by sex, age category, and periodontitis diagnosis category). Allocation procedures are implemented to maintain concealment from outcome assessors where feasible.

Statistical considerations (high-level):

Primary analyses will compare microbiome changes over time between study arms using community-level metrics (alpha diversity, beta diversity) and appropriate multivariable models to estimate group and time effects while accounting for relevant covariates (e.g., smoking status, diet quality, perceived stress, physical activity). Differential abundance approaches may be used to identify taxa/features associated with intervention arms, with attention to multiple testing control where appropriate. Secondary outcomes will be summarized descriptively and explored longitudinally using suitable models for repeated measures. As a pilot study, analyses are intended to be exploratory and to inform future hypothesis testing.

Safety monitoring:

The supplements used are marketed as dietary supplements in Germany. Participants are monitored for adverse events and serious adverse events throughout participation. Any suspected supplement-related intolerance or clinically relevant events are documented and managed according to clinical judgment and institutional procedures.

Ethics and dissemination:

The study is conducted in accordance with the Declaration of Helsinki and applicable data protection requirements. Ethics approval is obtained from the Ethics Committee of the Heidelberg Medical Faculty prior to recruitment. All participants provide written informed consent. Data are pseudonymized and stored securely according to institutional policy. Results will be disseminated through peer-reviewed publication and scientific presentations, with prospective trial registration and prespecified primary outcomes to support transparency.

Study Type

Interventional

Enrollment (Estimated)

60

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • Germany
    • Baden-Wurttemberg
      • Heidelberg, Baden-Wurttemberg, Germany, 69120
        • Recruiting
        • Heidelberg University Hospital
        • Contact:
        • Sub-Investigator:
          • Joel Hettler
        • Sub-Investigator:
          • Valentin Bartha

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Age ≥ 18 years

    • Stage III or IV periodontitis (localized or generalized)
    • Ability to provide informed consent
    • Written informed consent including data protection consent

Exclusion Criteria:

  • • Pregnancy or breastfeeding

    • Conditions/medications likely to substantially confound the oral microbiome or periodontal healing (e.g., uncontrolled diabetes mellitus, systemic immunosuppression, chronic steroid use)
    • Antibiotic use within the last 3 months
    • Use of oral pre-/probiotic supplements within the last 3 months
    • Recent subgingival instrumentation within the last 6 months
    • Need for obligatory adjunctive systemic antibiotic prophylaxis/therapy for NSPT
    • Severe active systemic infection or other conditions judged by investigators to pose undue risk
    • Regular use of antiseptic mouthrinses during the study period (unless medically required)
    • Strict diets likely to substantially alter baseline microbiome trajectories (e.g., ketogenic, strict vegan) per protocol definition
    • Chronic bowel diseases (for systemic confounding considerations)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Control
Guideline-concordant non-surgical periodontal therapy including mechanical subgingival instrumentation and risk-factor-oriented oral hygiene instruction, followed by supportive periodontal therapy (maintenance) as part of routine care. No placebo is used.
Procedure: Non-surgical periodontal therapy (NSPT) and supportive periodontal therapy (SPT)
Guideline-concordant non-surgical periodontal therapy including mechanical subgingival instrumentation and risk-factor-oriented oral hygiene instruction, followed by supportive periodontal therapy (maintenance) as part of routine care. No placebo is used.
Experimental: Test A - Probiotic
Procedure: Non-surgical periodontal therapy (NSPT) and supportive periodontal therapy (SPT)
Guideline-concordant non-surgical periodontal therapy including mechanical subgingival instrumentation and risk-factor-oriented oral hygiene instruction, followed by supportive periodontal therapy (maintenance) as part of routine care. No placebo is used.
Dietary supplement: Probiotic lozenge (Limosilactobacillus reuteri; GUM® PerioBalance®)
Commercial dietary supplement lozenge containing Limosilactobacillus reuteri (GUM® PerioBalance®, Sunstar Deutschland GmbH, Schönau, Germany). Administered orally according to manufacturer instructions for 3 months starting with NSPT.
Experimental: Test B - Synbiotic-like: Probiotic + Vitamin B12
Procedure: Non-surgical periodontal therapy (NSPT) and supportive periodontal therapy (SPT)
Guideline-concordant non-surgical periodontal therapy including mechanical subgingival instrumentation and risk-factor-oriented oral hygiene instruction, followed by supportive periodontal therapy (maintenance) as part of routine care. No placebo is used.
Dietary supplement: Probiotic lozenge (Limosilactobacillus reuteri; GUM® PerioBalance®)
Commercial dietary supplement lozenge containing Limosilactobacillus reuteri (GUM® PerioBalance®, Sunstar Deutschland GmbH, Schönau, Germany). Administered orally according to manufacturer instructions for 3 months starting with NSPT.
Dietary supplement: Vitamin B12 drops (natural elements)
Commercial dietary supplement vitamin B12 drops (natural elements GmbH, Düsseldorf, Germany). Administered orally according to manufacturer instructions for 3 months, in addition to the probiotic regimen, starting with NSPT.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in oral microbiome composition (supragingival and subgingival)
Time Frame: Baseline through 12 months (assessed at baseline, NSPT instrumentation visit, ~3 months, ~6 months, and ~12 months).
Changes in supragingival and subgingival microbial community structure and taxonomic profiles, assessed by 16S rDNA-based profiling and metagenomic sequencing (as applicable), including diversity metrics and relative abundance of microbial taxa/features.
Baseline through 12 months (assessed at baseline, NSPT instrumentation visit, ~3 months, ~6 months, and ~12 months).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University Hospital Heidelberg

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 25, 2024

Primary Completion (Estimated)

October 1, 2026

Study Completion (Estimated)

October 1, 2026

Study Registration Dates

First Submitted

February 24, 2026

First Submitted That Met QC Criteria

February 24, 2026

First Posted (Actual)

March 2, 2026

Study Record Updates

Last Update Posted (Actual)

March 2, 2026

Last Update Submitted That Met QC Criteria

February 24, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • S-477/2024

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data underlying the results reported in the primary publication (including key clinical outcomes and processed microbiome feature tables) will be made available upon reasonable request, subject to approval by the study team, a data use agreement, and applicable ethics and data protection requirements. Raw sequencing files and linkage keys will not be shared.

IPD Sharing Time Frame

Beginning 6 months after publication of the primary results and ending 5 years thereafter.

IPD Sharing Access Criteria

Requests should include a brief proposal, analysis plan, and evidence of appropriate ethical approval (if required). Data will be provided to qualified researchers for non-commercial scientific purposes under a signed data use agreement. Contact: Diana.wolff@med.uni-heidelberg.de

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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