Coriander essential oil and chlorhexidine mouthwashes in adults with Stage III or Stage IV periodontitis: effects on saliva microbiome and inflammation
| ISRCTN | ISRCTN79156900 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN79156900 |
| Rīga Stradiņš University Research Ethics Committee Number | 2-PĒK-4/356/2024 |
| Sponsor | Riga Stradiņš University |
| Funder | Rīgas Stradiņa Universitāte |
- Submission date
- 16/03/2026
- Registration date
- 11/05/2026
- Last edited
- 05/10/2026
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Oral Health
Plain English summary of protocol
Background and study aims
Periodontitis is a serious gum disease that damages the tissues supporting the teeth. It is linked to changes in the bacteria living in the mouth and to inflammation. Chlorhexidine mouthwash is commonly used in dental care because it can reduce bacteria, but it may also affect beneficial bacteria and can cause side effects such as an unpleasant taste, changes in taste, dry mouth, mouth irritation, or tooth staining.
This study aims to compare three mouthwashes in adults with periodontitis: a mouthwash containing coriander essential oil, a standard chlorhexidine mouthwash, and water. The study looks at how these mouthwashes affect the bacteria found in saliva and saliva inflammatory markers over a 2-week period.
Who can participate?
Adults aged 18 to 60 years with Stage III or Stage IV periodontitis
What does the study involve?
Participants first provide an unstimulated saliva sample in the morning under fasting conditions. They are then randomly assigned to one of three mouthwash groups:
1. Coriandrum sativum essential oil mouthwash, 4 mg/ml
2. Chlorhexidine mouthwash, 0.12%
3. Water control
Participants use 20 ml of their assigned mouthwash twice daily for 2 weeks while maintaining their usual diet and lifestyle. After 2 weeks, participants provide a second unstimulated saliva sample in the morning under fasting conditions. The saliva samples are analysed in the laboratory to study the oral microbiome, meaning the bacteria and other microbes present in saliva, and inflammatory markers.
What are the possible benefits and risks of participating?
Participants may not receive a direct personal benefit from taking part. The study may help researchers better understand how different mouthwashes affect the oral microbiome and inflammation in people with periodontitis. This knowledge may support the development of oral hygiene products that are effective but less disruptive to beneficial oral bacteria.
Saliva collection is non-invasive and has minimal risk. Possible risks from using the mouthwashes include unpleasant taste, temporary changes in taste, dry mouth, burning or irritation in the mouth, tooth or tongue staining, and possible sensitivity or allergic reaction. Chlorhexidine is known to be associated with taste disturbance and staining in some users. Participants can stop taking part if they experience discomfort or no longer wish to continue.
Where is the study run from?
The study is run from Riga Stradiņš University, Riga, Latvia. Participants were recruited and sampled through the RSU Institute of Stomatology, Riga, Latvia.
When is the study starting and how long is it expected to run for?
August 2024 to August 2025
Who is funding the study?
The study is funded through the Postdoctoral Grant “Oral microbiome and inflammatory dynamics in Stage III periodontitis: comparative effects of mouthwash formulations containing Latvian-grown Coriandrum sativum essential oil versus standard chlorhexidine regimen” (Grant No. RSU-PG-2024/1-0010), as part of the project “RSU Internal and RSU with LASE External Consolidation” (Project No. 5.2.1.1.i.0/2/24/I/CFLA/005), funded by the European Union Recovery and Resilience Facility and the budget of the Republic of Latvia.
Who is the main contact?
Dr Alisa Kazarina, alisa.kazarina@rsu.lv
Contact information
Principal investigator, Scientific, Public
Riga Stradiņš University
Dzirciema Street 16
Riga
LV-1007
Latvia
 ORCID ID |
0000-0003-3602-5261 |
|---|---|
| Phone | +371 (0)29832898 |
| alisa.kazarina@rsu.lv |
Study information
| Primary study design | Interventional |
|---|---|
| Allocation | Randomized controlled trial |
| Masking | Open (masking not used) |
| Control | Placebo |
| Assignment | Parallel |
| Purpose | Basic science, Prevention |
| Scientific title | A randomized, three-arm, parallel clinical study in adults with Stage III or Stage IV periodontitis comparing Coriandrum sativum essential oil mouthwash, 0.12% chlorhexidine mouthwash, and water control for changes in salivary microbiome composition and salivary inflammatory markers |
| Study acronym | EOsPerio |
| Study objectives | Current study objectives as of 20/07/2026: 1. To determine the effect of a Coriandrum sativum essential oil mouthwash on the salivary microbiome of adults with Stage III or Stage IV periodontitis and to compare this effect with chlorhexidine and water control 2. To compare changes in salivary inflammatory markers between the three study groups during the 2-week pre-treatment intervention period Previous study objectives: 1. To determine the effect of a Coriandrum sativum essential oil mouthwash on the salivary microbiome of adults with Stage III periodontitis and to compare this effect with chlorhexidine and water control 2. To compare changes in salivary inflammatory markers between the three study groups during the 2-week pre-treatment intervention period |
| Ethics approval(s) |
Approved 15/04/2024, Riga Stradiņš University Research Ethics Committee (16 Dzirciema iela, Riga, LV-1007, Latvia; +371 (0)67409219; pek@rsu.lv), ref: 2-PĒK-4/356/2024 |
| Health condition(s) or problem(s) studied | Stage III or Stage IV periodontitis |
| Intervention | This is a single-centre, randomized, three-arm, parallel, placebo- and active-controlled interventional study conducted in Latvia. Adults with Stage III or Stage IV periodontitis were recruited at the Rīga Stradiņš University Institute of Stomatology. Participants were randomised to one of three parallel study groups using a simple computer-generated random allocation sequence prepared before enrolment. No stratification or blocking was used. Study intervention bottles were prepared in advance according to the allocation sequence. After eligibility assessment, informed consent, and baseline saliva collection, each participant was assigned sequentially to the next pre-prepared bottle in the sequence. The study was open-label, and no masking was used. Participants were assigned to one of three study arms: 1. Coriandrum sativum essential oil (CSEO) mouthwash, 4 mg/ml 2. Chlorhexidine (CHX) mouthwash, 0.12% 3. Water control Participants used 20 ml of their assigned mouthwash twice daily for 2 weeks while maintaining their usual diet and lifestyle. At baseline and after the 2-week intervention, unstimulated whole saliva (minimum 2 ml) was collected in the morning in a fasting state. Saliva aliquots were used for inflammatory marker profiling and microbiome analysis. The microbial endpoint was assessed using shotgun metagenomic sequencing of saliva, with human reads removed before downstream microbial analyses. |
| Intervention type | Other |
| Primary outcome measure(s) |
|
| Key secondary outcome measure(s) | |
| Completion date | 16/08/2025 |
Eligibility
| Participant type(s) | |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Upper age limit | 60 Years |
| Sex | All |
| Target sample size at registration | 60 |
| Total final enrolment | 38 |
| Key inclusion criteria | Current inclusion criteria as of 07/07/2026: 1. Adults aged 18 to 60 years 2. Diagnosis of Stage III or Stage IV periodontitis 3. Systemically healthy with no known systemic disease likely to materially affect study results 4. Able to understand and communicate in Latvian Previous inclusion criteria: 1. Adults aged 18 to 60 years 2. Diagnosis of Stage III periodontitis 3. Systemically healthy with no known systemic disease likely to materially affect study results 4. Able to understand and communicate in Latvian |
| Key exclusion criteria | Current exclusion criteria as of 20/07/2026: 1. Acute illness within the previous 3 months 2. Current or previous chronic systemic disease likely to affect study outcomes, including but not limited to cardiovascular disease or diabetes 3. Malignancy within the previous 3 years or ongoing cancer treatment 4. Use of antibiotics, probiotic tablets/capsules, immunosuppressive drugs, anti-cytokine therapy, or corticosteroids within the previous 1 month 5. Pregnancy or breastfeeding 6. Major dietary changes during the previous month, especially changes in major food groups 7. Recent dental procedures or periodontal therapy likely to affect periodontal health or the oral microbiome, including major dental surgery or periodontitis therapy within the previous 1 month 8. Current participation in another clinical study or research study that could affect the results Previous exclusion criteria: 1. Acute illness within the previous 3 months 2. Current or previous chronic systemic disease likely to affect study outcomes, including but not limited to cardiovascular disease or diabetes 3. Malignancy within the previous 3 years or ongoing cancer treatment 4. Use of antibiotics, probiotic tablets/capsules, immunosuppressive drugs, anti-cytokine therapy, or corticosteroids within the previous 3 months 5. Pregnancy or breastfeeding 6. Major dietary changes during the previous month, especially changes in major food groups 7. Recent dental procedures or periodontal therapy likely to affect periodontal health or the oral microbiome, including major dental surgery or periodontitis therapy within the previous 6 months 8. Current participation in another clinical study or research study that could affect the results |
| Date of first enrolment | 01/08/2024 |
| Date of final enrolment | 01/08/2025 |
Locations
Countries of recruitment
- Latvia
Study participating centres
Results and Publications
| Individual participant data (IPD) Intention to share | No |
|---|
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Results article | 03/10/2026 | 05/10/2026 | Yes | No |
Editorial Notes
05/10/2026: Publication reference added.
20/07/2026: The following changes were made to the study record:
1. The final enrolment number was corrected from 27 to 38.
2. The exclusion criteria and study objectives were updated.
07/07/2026: The inclusion criteria, public/scientific title and health condition were updated to change 'Stage III periodontitis' to 'Stage III or Stage IV periodontitis'.
16/03/2026: Study's existence confirmed by the Riga Stradiņš University Research Ethics Committee.
