Evaluation of the Effect of Periimplant Soft Tissue Phenotype on Marginal Bone Loss

Early marginal bone loss around the implant can be caused by various reasons. Keratinized mucosal thickness (KMT) and keratinized gingival width (KGW) are components of periimplant soft tissue. Recently, KGW and KMT in the peri-implant region have been investigated as possible factors influencing this phenomenon.

The hypothesis of this study: Periimplant soft tissue phenotype is associated with marginal bone loss and peri implant health through Receptor Activator Of Nuclear Factor-Kappa B Ligand (RANKL), Osteoprotegerin (OPG), Tumor Necrosis Factor Alpha (TNF-α), MicroRNA-223 (MiRNA-223) and Microrna-27a 80 implants, at least 1 year after their loading, in patients who continued their routine controls will be included in the study. The participants in this study were selected from patients who underwent implant placement by the same periodontologist (E.Ö.) in the Department of Periodontology of Necmettin Erbakan University in 2020 and still have 6-month radiographic and clinical follow-up. Selected patients, those who signed the written informed consent form were included in the study. In the study, the first radiographs of all patients, the clinical and radiographic conditions obtained at the 6-month routine control examination will be evaluated. During the same routine controls, a sample of peri-implant groove fluid was taken with paper strips.

Diagnoses of the implants included in the study will be made using the criteria of the 2017 World Workshop on Periodontal and Peri-implant Diseases and Conditions. 2 mm marginal bone loss (MBL) which may occur during the bone remodeling process after implant placement and loading, is accepted as the threshold. The absence of signs of inflammation (redness, swelling, bleeding on probing) in the peri-implant soft tissue, probing depth (PD) ≤5 mm with mild force (approximately 0.25 N), and no further bone loss following initial healing are defined as "periimplant health". "Peri-implant mucositis" is defined as clinically observable signs of inflammation (swelling, redness and soft consistency of tissue), bleeding on probing (BOP) (lines or drops) and/or signs of suppuration in the absence of bone loss greater than 2 mm, the threshold for initial bone remodulation defined. The definition of "peri-implantitis" is clinically observable signs of inflammation, probing bleeding and/or suppuration, increased probing depth, progressive bone loss after implant restoration, or MBL ≥3 mm with profuse bleeding in the absence of initial radiographs and PD was ≥6 mm. Implants with periimplantitis will be excluded. Implants will be divided into 2 groups according to their peri-implant health: Peri-implant health and peri-implant mucositis.

In addition to routine clinical and radiographic examination of the implants, KMT and KGW measurements will be made. they will be divided into 2 groups in 2 ways. According to KMT on their buccal surfaces: KMT ≥2 mm are included in the adequate KMT, and those with KMT <2 mm are in the inadequate KMT group (60). According to KGW on their buccal surfaces: KGW≥2 mm are adequate KGW, those with KGW<2 mm are inadequate KGW.

Radiographic evaluation will be made using intraoral periapical radiographs obtained using the parallel technique with the plastic film holder. Calibration of digital images will be performed using the length of the implant as a well-defined fixed reference point. The bone level measurement will be made by measuring between the bone-implant first contact point and the reference point in the coronal part of the implant body selected for different implant systems in both the mesial and distal directions of the implants. In order to evaluate the marginal bone loss (MBL), the measurements obtained will be compared with the measurements on the radiographs taken after the delivery of the prosthesis.

Peri-implant crevicular fluid (PIGF) will be collected from the participants for the biochemical evaluation to be made. PIGF specimens will be collected from the mesiobuccal of each implant, prior to any periodontal probing, and after removal of the supra mucosal plate. The area to be sampled will be insulated with cotton rolls and air-dried. The paper will be advanced with the strip until it shows slight resistance and held in the sample area for 30 seconds. Samples will be stored at -70˚C.

TNF-α, RANKL, OPG and MiRNA 223 and MiRNA 27a evaluations of the peri-implant crevicular fluid (PIGF) collected from the patients will be performed. TNF-α, RANKL and OPG will be evaluated by the Enzyme-Linked ImmunoSorbent Assay (ELISA) method. MiRNA 223 and MiRNA 27a evaluations will be performed using Real-Time Polymerase Chain Reaction (RT-PCR).

Marginal bone loss and biomarker levels will be compared between the groups.

Inclusion criteria

• Have at least one fixed restoration on a titanium dental implant in the mouth
• Over-implant restoration, functioning for at least 12 months
• Attending our preventive care regularly (≥1/year)
• Non-smokers

Exclusion criteria

• Receiving head or neck radiation in the last 6 months
• Bisphosphonate users
• Those who have received antibiotic treatment in the last 3 months
• Patients with diabetes mellitus (hemoglobin A1c ≥7.0) that may affect the outcome of implant therapy
• implants with peri-implantitis
• Pregnant or breastfeeding mothers
• Those with metabolic bone disorders
• Those who have a history of periodontitis and have undergone any periodontal treatment in the last year
• Those whose implant positions are not suitable
• Implants using soft or hard tissue grafts before, during, or after implant placement
• Those with a restoration that did not allow accurate probing depth recording were excluded from the study.