Effects of GLP-1 Receptor Agonists on Saliva and Oral Health

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• Diabetes Mellitus, Type 2 10,371
• Obesity 11,522
• Overweight 3,599
• Xerostomia 286
• Dental Caries 1,171

Diabetes Mellitus, Type 2

10,371 studies on the registry are indexed under Diabetes Mellitus, Type 2; 1,406 are open to participants now.

This study's planned enrollment of 50 is below the median of 300 across 1,741 observational studies indexed under Diabetes Mellitus, Type 2.

Lead sponsor

Kırıkkale University is the lead sponsor of 114 studies on the registry; 24 are open to participants now.

Study population

Groups and cohorts

• GLP-1 RA Group

  Patients diagnosed with Type 2 diabetes and/or obesity who are newly prescribed GLP-1 receptor agonists.

  Drug: GLP-1 Receptor Agonists

Interventions

• DrugGLP-1 Receptor Agonists

  Patients diagnosed with Type 2 diabetes and/or obesity who are newly prescribed GLP-1 receptor agonists as part of their routine medical treatment. Baseline assessments are performed prior to the first dose, and no drug administration or dosage modification is performed by the researcher.

Primary outcomes

1. Change in Unstimulated Salivary Flow Rate

   According to the GC Saliva-Check Buffer kit (GC Corporation) instructions, following a visual inspection, unstimulated whole saliva will be collected via the passive drooling/spitting method for 5 minutes with the participant seated upright and head tilted slightly forward. The resting salivary flow rate will be calculated and reported in milliliters per minute (mL/min).

   Time frame: Baseline (Month 0), Month 3, and Month 6

Secondary outcomes

1. Change in Stimulated Salivary Flow Rate

   Stimulated saliva will be collected using the paraffin wax chewing method provided in the GC Saliva-Check Buffer kit (GC Corporation). Participants will chew the paraffin piece for 5 minutes, saliva will be collected into a graduated tube, and the flow rate will be calculated in milliliters per minute (mL/min).

   Time frame: Baseline (Month 0), Month 3, and Month 6

2. Change in Salivary pH

   Resting saliva pH will be determined using the GC Saliva-Check Buffer test kit (GC Corporation). A pH test strip will be immersed in the collected unstimulated saliva sample for 10 seconds and compared against the manufacturer's standardized color chart (ranges: 5.0 to 5.8 \[highly acidic\], 6.0 to 6.6 \[moderately acidic\], and 6.8 to 7.8 \[healthy/neutral\]). Higher pH values indicate a more neutral/healthy oral environment.

   Time frame: Baseline (Month 0), Month 3, and Month 6

3. Change in Salivary Buffering Capacity

   Evaluated using the GC Saliva-Check Buffer test kit (GC Corporation). One drop of stimulated saliva will be dispensed onto each of the three test pads on the strip. After 2 minutes, the color change on each pad will be scored from 0 to 4 (Green=4, Green/Blue=3, Blue=2, Red/Blue=1, Red=0). Scores are summed to give a total buffering capacity score ranging from 0 to 12 (0-5: very low; 6-9: low; 10-12: normal/high). Higher scores indicate better buffering capacity.

   Time frame: Baseline (Month 0), Month 3, and Month 6

4. Change in Dental Plaque Accumulation

   Assessed using the Silness and Löe Plaque Index (PI) on designated index teeth across buccal, lingual, mesial, and distal surfaces. Plaque presence is scored from 0 to 3 (0 = No plaque; 1 = A film of plaque adhering to the free gingival margin; 2 = Moderate accumulation of soft deposits; 3 = Abundance of soft matter within the gingival pocket and/or on the tooth margin). The individual mean score ranges from 0 to 3, where higher scores represent greater plaque accumulation and poorer oral hygiene.

   Time frame: Baseline (Month 0), Month 3, and Month 6

5. Change in Dental Caries Status

   Cumulative caries experience will be evaluated using the World Health Organization (WHO) Decayed, Missing, and Filled Teeth (DMFT) index (ranging from 0 to 28, where higher scores indicate greater cumulative caries experience). Early coronal caries lesions will be detected using the International Caries Detection and Assessment System (ICDAS-II), scoring tooth surfaces from 0 (sound) to 6 (extensive distinct cavity with visible dentin), and the highest ICDAS score per tooth will be recorded for tooth-level analysis. Higher DMFT and ICDAS-II scores represent worse caries experience and active decay.

   Time frame: Baseline (Month 0), Month 3, and Month 6

6. Change in Subjective Dry Mouth Symptoms

   Evaluated using the 5-item Summated Xerostomia Inventory (SXI-D) questionnaire. Participants rate xerostomia-related symptoms over the previous month using a 3-point Likert scale (1 = Never, 2 = Occasionally, 3 = Often). Total scores range from 5 to 15, where higher scores represent more severe subjective dry mouth symptoms.

   Time frame: Baseline (Month 0), Month 3, and Month 6

7. Change in Dietary and Nutritional Habits

   Assessed using a custom, investigator-developed food frequency questionnaire. The questionnaire evaluates daily meal frequency, fluid intake, food preferences, avoidance of dry foods, and consumption frequencies (daily, weekly, monthly) of cariogenic and protein-rich foods. No overall summary score is calculated; responses will be analyzed and reported as categorical consumption frequencies and percentages.

   Time frame: Baseline (Month 0), Month 3, and Month 6

8. Change in Salivary Secretory Immunoglobulin A (sIgA) Levels

   Concentrations of secretory immunoglobulin A (sIgA) will be quantified in saliva supernatants using commercially available enzyme-linked immunosorbent assay (ELISA) kits according to the manufacturer's protocol. Values will be expressed in micrograms per milliliter (µg/mL) and normalized to total protein concentration.

   Time frame: Baseline (Month 0), Month 3, and Month 6

9. Change in Salivary Beta-Defensin-3 Levels

   Concentrations of salivary beta-defensin-3 will be quantified in saliva supernatants using commercially available enzyme-linked immunosorbent assay (ELISA) kits according to the manufacturer's protocol. Values will be expressed in picograms per milliliter (pg/mL) and normalized to total protein concentration.

   Time frame: Baseline (Month 0), Month 3, and Month 6

10. Change in Salivary Total Protein Concentration

    Salivary total protein concentration will be determined using the Bradford protein assay with Coomassie Brilliant Blue G-250 dye and a standard bovine serum albumin calibration curve measured at 595 nm. Results will be expressed in milligrams per milliliter (mg/mL) and used to standardize salivary antimicrobial peptide levels.

    Time frame: Baseline (Month 0), Month 3, and Month 6

11. Change in Serum C-Reactive Protein Levels

    Serum C-reactive protein (CRP) concentrations will be determined from fasting venous blood samples using standard clinical laboratory immunoturbidimetric assays. Values will be reported in milligrams per liter (mg/L).

    Time frame: Baseline (Month 0), Month 3, and Month 6

12. Change in Homeostatic Model Assessment for Insulin Resistance

    Insulin resistance will be evaluated using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), calculated with the standard formula: \[fasting glucose (mg/dL) × fasting insulin (µIU/mL)\] / 405. The resulting dimensionless index reflects insulin resistance, where higher values indicate greater insulin resistance.

    Time frame: Baseline (Month 0), Month 3, and Month 6

13. Change in Glycated Hemoglobin (HbA1c) Levels

    Glycated hemoglobin (HbA1c) levels will be measured from venous blood samples using high-performance liquid chromatography (HPLC) or certified clinical laboratory immunoassays standardized to the National Glycohemoglobin Standardization Program (NGSP). Values will be reported as a percentage (%).

    Time frame: Baseline (Month 0), Month 3, and Month 6

14. Change in Body Mass Index

    Body mass index (BMI) will be calculated using standardized anthropometric measurements as body weight in kilograms divided by the square of height in meters (kg/m2). Changes over the 6-month follow-up period will be evaluated and reported in kg/m2.

    Time frame: Baseline (Month 0), Month 3, and Month 6

Individual participant data

Plan to share: No — Individual participant data (IPD) will not be shared with third parties or other researchers to protect patient privacy and confidentiality, in strict accordance with the commitments made in the Informed Consent Form approved by the Institutional Ethics Committee.