At baseline (T0), participants undergo clinical and photographic assessments, receive oral hygiene instruction, and begin a 14-day home regimen with 0.2% chlorhexidine digluconate mouthwash, used twice daily (10 mL for 30 seconds) after toothbrushing. The solution is not rinsed away, and participants avoid food or drink for 1 hour. All participants use a standardized sodium lauryl sulfate (SLS)-free toothpaste (Biorepair®).

At 1 month (T1), participants receive professional supragingival prophylaxis following the Guided Biofilm Therapy (GBT) protocol, which includes plaque disclosure, piezoelectric ultrasonic scaling with an EMS Piezon device, and air-polishing with glycine powder.

At 3 months (T2) and 6 months (T3), additional GBT sessions and repetition of the 14-day home regimen are performed only if the Full-Mouth Bleeding Score (FMBS) remains greater than 10%.

The Full-Mouth Bleeding Score (FMBS) measures the percentage of bleeding sites after gentle probing at four sites per tooth (mesial, buccal, distal, lingual). FMBS reflects the presence and severity of gingival inflammation. Scores range from 0% (no bleeding) to 100% (bleeding at all sites). A higher FMBS indicates more severe gingival inflammation. For each participant, a mean FMBS is calculated at each time point (T0, T1, T2, T3, T4).

Salivary activated Matrix Metalloproteinase-8 (aMMP-8) is a biomarker of periodontal inflammation and collagen breakdown. At baseline (T0) and 2 weeks (T1), unstimulated whole saliva samples are collected using a standardized sterile protocol. Participants refrain from eating, drinking, or brushing their teeth for at least 1 hour before collection. Saliva is collected passively into sterile tubes over 5 minutes, immediately frozen at -20°C, and later analyzed via immunoassay (enzyme-linked immunosorbent assay, ELISA).

Results are expressed in nanograms per milliliter (ng/mL) and interpreted as: <8 ng/mL = no inflammation; 9-19 ng/mL = mild inflammation; >20 ng/mL = severe inflammation. For each participant, mean aMMP-8 levels will be calculated at T0 and T1.

Gingival Recession (REC) is defined as the distance in millimeters from the cemento-enamel junction (CEJ) to the gingival margin, measured at six sites per tooth (mesiobuccal, midbuccal, distobuccal, mesiolingual, midlingual, distolingual) using a calibrated periodontal probe (Hu-Friedy PCP UNC 15). Measurements are performed at baseline (T0), after completion of the 14-day mouthwash protocol (T1, 2 weeks), following professional supragingival prophylaxis (T2, 1 month), and during the subsequent follow-up visits (T3, 3 months, and T4, 6 months). Scores range from 0 mm (no recession) to values exceeding 5 mm in cases of severe gingival recession. For each patient, a mean REC score is calculated at every time point (T0-T4) to monitor potential soft tissue loss over the study period. Mean REC values will be compared between the MicroRepair® ABX mouthwash regimen and the chlorhexidine digluconate 0.2% mouthwash regimen.

Clinical Attachment Level (CAL) is defined as the distance in millimeters from the cemento-enamel junction (CEJ) to the base of the periodontal pocket, recorded at six sites per tooth (mesiobuccal, midbuccal, distobuccal, mesiolingual, midlingual, distolingual) using a calibrated periodontal probe (Hu-Friedy PCP UNC 15). Measurements are performed at baseline (T0), after completion of the 14-day mouthwash regimen (T1, 2 weeks), following professional supragingival prophylaxis (T2, 1 month), and at subsequent follow-up visits (T3, 3 months, and T4, 6 months). CAL values typically range from 0 mm (healthy periodontium) to ≥7 mm (advanced attachment loss). For each patient, a mean CAL score is calculated at every time point (T0-T4). Mean CAL values will be compared between the MicroRepair® ABX mouthwash regimen and the chlorhexidine digluconate 0.2% mouthwash regimen to assess differences in periodontal tissue attachment loss.

The Modified Lobene Stain Index is used to evaluate extrinsic dental staining on vestibular and lingual/palatal tooth surfaces by assessing both stain intensity and extent. Intensity is scored as 0 = no stain, 1 = light stain, 2 = moderate stain, and 3 = heavy stain. Extent is scored as 0 = no stain, 1 = stain covering up to one-third of the surface, 2 = stain covering between one-third and two-thirds of the surface, and 3 = stain covering more than two-thirds of the surface. The final score for each surface is obtained by multiplying intensity by extent, with higher scores indicating more pronounced staining. Assessments are conducted at baseline (T0), after completion of the 14-day mouthwash regimen (T1, 2 weeks), following professional supragingival prophylaxis (T2, 1 month), and during subsequent follow-up visits (T3, 3 months, and T4, 6 months). The index is used to compare the staining potential of the MicroRepair® ABX mouthwash regimen versus the chlorhexidine digluconate 0.2%

The Schiff Air Index is employed to assess dentin hypersensitivity in response to a standardized air stimulus directed onto the vestibular surface of each tooth. Responses are scored as 0 = no response, 1 = response without request to discontinue the stimulus, 2 = response with a request to discontinue the stimulus, and 3 = painful response with immediate withdrawal or visible discomfort. For each patient, a mean Schiff score is calculated at every evaluation. Measurements are performed at baseline (T0), after completion of the 14-day mouthwash regimen (T1, 2 weeks), following professional supragingival prophylaxis (T2, 1 month), and during the follow-up visits (T3, 3 months, and T4, 6 months). Scores will be compared between the MicroRepair® ABX mouthwash regimen and the chlorhexidine digluconate 0.2% regimen to determine the impact of treatments on dentin hypersensitivity over time.

Taste perception will be assessed using a validated patient-reported questionnaire designed to capture the presence and severity of taste alterations, including bitter, metallic, or unpleasant sensations. Each item is scored on a 5-point Likert scale, where 0 = no alteration, 1 = mild alteration, 2 = moderate alteration, 3 = severe alteration, and 4 = very severe alteration. For each patient, a total score is calculated, with higher values indicating more pronounced dysgeusia. Evaluations are performed at baseline (T0), after completion of the 14-day mouthwash regimen (T1, 2 weeks), following the first professional supragingival prophylaxis (T2, 1 month), and during follow-up visits (T3, 3 months, and T4, 6 months). Mean scores will be compared between the MicroRepair® ABX mouthwash regimen and the chlorhexidine 0.2% regimen to assess and compare the tolerability of the interventions over time.