This study aims to increase the width and thickness of peri-implant keratinized mucosa (KM) by transferring a properly dimensioned free gingival graft (FGG) from the palatal donor site and to evaluate its effect as an adjunctive approach to non-surgical peri-implantitis therapy. The procedure is indicated for patients diagnosed with peri-implantitis who present with an inadequate KM (midbuccal KM height < 2 mm). One month after non-surgical therapy, patients in the test group will undergo keratinized mucosa augmentation using an FGG, while patients in the control group will continue with supportive periodontal therapy and regular follow-up visits. The primary outcome measure of the study is the change in probing depth (PD) at 12 months following peri-implantitis treatment.

Background and Case Definition

Peri-implantitis is a disease that typically develops from peri-implant mucositis, an inflammatory condition affecting the soft tissues surrounding dental implants. If left untreated, peri-implant mucositis may progress to peri-implantitis, leading to loss of supporting hard and soft tissues. Clinical signs of peri-implantitis include bleeding on probing (BoP), erythema of the peri-implant mucosa, suppuration, and increased probing depths (PD ≥ 5 mm). The presence of peri-implant bone loss on radiographic examination is a key diagnostic criterion for peri-implantitis.

Although increased width and thickness of keratinized mucosa have been suggested to support peri-implant tissue stability, their role in maintaining peri-implant health and improving the response to peri-implantitis therapy remains controversial. Given the ongoing debate regarding the role of keratinized mucosa dimensions in modulating the response to non-surgical peri-implantitis therapy, further clinical evidence is warranted.

The hypothesis of this study is that adjunctive keratinized mucosa augmentation following non-surgical peri-implantitis therapy results in improved clinical outcomes compared to non-surgical treatment alone. Therefore, the aim of this study was to investigate whether adjunctive keratinized mucosa augmentation improves clinical and radiographic outcomes compared to non-surgical peri-implantitis therapy alone.

Study Population Inclusion Criteria

Systemically healthy adults (≥18 years of age)

Implant-supported restorations in function for at least one year prior to enrollment

Exclusion Criteria

Systemic conditions potentially affecting wound healing or treatment outcomes (e.g., uncontrolled diabetes, active cancer therapy)

Use of medications within the previous three months that could influence healing or inflammation (e.g., anticoagulants, antiplatelet agents, antibiotics, corticosteroids)

Pregnancy or lactation

Smoking ≥10 cigarettes/day

Untreated periodontitis

Malpositioned implants

Previous soft tissue grafting procedures at the implant site

Treatment Protocol

All patients will receive initial non-surgical peri-implantitis therapy, including mechanical debridement of the implant surface using titanium curettes and resin ultrasonic tips, along with saline irrigation for surface decontamination. Oral hygiene instructions will be reinforced in all patients.

In the test group, a free gingival graft procedure will be performed 4-6 weeks after completion of non-surgical therapy to increase the width and thickness of keratinized mucosa.

In the control group, no surgical intervention will be performed following non-surgical therapy, and patients will continue with supportive peri-implant care.

Clinical Parameters

All clinical parameters will be recorded by a calibrated examiner at predefined evaluation time points.

1. Plaque Index (PI)

   Plaque accumulation will be assessed using the Plaque Index described by O'Leary et al. (1972). The presence or absence of plaque will be recorded at six sites per implant (mesio-buccal, mid-buccal, disto-buccal, mesio-lingual, mid-lingual, disto-lingual). The plaque index will be expressed as a percentage of sites with visible plaque relative to the total number of assessed sites.

2. Probing Depth (PD)

   Probing pocket depth will be measured using a William's periodontal probe, positioned parallel to the long axis of the implant. Measurements will be obtained at six sites per implant (mesio-buccal, mid-buccal, disto-buccal, mesio-lingual, mid-lingual, disto-lingual). The mean value of the six measurements will be calculated and used as the representative PPD value for each implant.

3. Bleeding on Probing (BoP)

   Bleeding on probing will be assessed according to the criteria proposed by Ainamo and Bay (1975). Following gentle probing of the peri-implant sulcus, bleeding will be recorded as present (+) or absent (-) at six sites per implant. BoP will be expressed as the percentage of bleeding-positive sites.

4. Width of Keratinized Mucosa (Mid-Buccal)

   The width of keratinized mucosa will be measured in millimeters at the mid-buccal aspect of each implant. Measurements will be taken from the peri-implant soft tissue margin to the mucogingival junction, encompassing both the free and attached keratinized mucosa.

5. Thickness of Keratinized Mucosa (Mid-Buccal)

   Keratinized mucosa thickness will be assessed using a K-type endodontic file with a silicone stopper. The file will be gently inserted perpendicular to the mucosal surface at the mid-buccal aspect until bone contact is reached. The penetration depth will then be measured using a digital caliper.

6. Vestibular Depth (Mid-Buccal)

   Vestibular depth will be measured at the mid-buccal aspect of the implant site as the vertical distance from the mucogingival junction to the deepest point of the vestibule. This measurement aims to assess changes in vestibular morphology potentially associated with soft tissue augmentation procedures.

7. Mucosal Recession (MR)

Peri-implant mucosal recession will be measured as the linear distance (in millimeters) from a fixed reference point on the implant-supported restoration (e.g., the crown margin or implant shoulder) to the most coronal level of the peri-implant soft tissue margin at the mid-buccal aspect. Positive values will indicate apical displacement of the mucosal margin.

Inclusion Criteria:

• Non-smoker
• Systemically healthy
• Keratinized mucosa witdh < 2 mm

Exclusion Criteria:

• İntake of medications that impede periodontal tissue health and healing
• Pregnancy or lactation