One of the criteria used for long-term implant success is the evaluation of radiographic bone loss. It is known that the keratinized mucosa over the alveolar crest forms a protective barrier against inflammatory infiltration. In addition, it has been reported that the vertical mucosal thickness on the crest is important in the formation of the biological width around the implant. The aim of this study was to evaluate the effect of vertical mucosal thickness on the alveolar crest on peri-implant marginal bone loss around crestal and subcrestal placed platform-switching implants. In this study, patients will be divided into 2 main groups with vertical mucosal thickness of 2 mm and less and more than 2 mm, and both groups will consist of 2 subgroups as crestally and subcrestally according to the implant level placed. A total of 80 implants will be included, 20 implants in each group. Before starting the surgery, after anesthesia is given, the width of the patient's peri-implant keratinized mucosa and the vertical mucosal thickness over the alveolar crest will be measured. Clinical and radiological measurements will be made in all patients during the prosthetic loading session (T0), at 3rd month (T1), 6th month (T2) and 1 year after loading (T3). With standardized control periapical radiographs to be taken as a result of one-year follow-up, the marginal bone loss amount in the implants will be evaluated using soft-ware.

Dental implants have become one of the most common treatments used for the rehabilitation of lost teeth. The success rate of dental implant treatment is quite high. One of the criteria used for long-term implant success is the evaluation of radiographic bone loss. It is known that the keratinized mucosa over the alveolar crest forms a protective barrier against inflammatory infiltration. It has been reported that the vertical mucosal thickness over the alveolar crest in the operation area before dental implant treatment is important in the formation of the biological width around the implant. There are studies in the literature examining the effects of vertical mucosal thickness on peri-implant marginal bone loss. In a study presented by Linkevicius et al., in 2014, they divided 80 patients into 2 groups according to their mucosal thickness. It was reported that radiological bone loss was 1.17 mm in the group with low vertical mucosal thickness at the end of 1-year follow-up, and 0.21 mm in the group with high vertical thickness.

The aim of the study was to evaluate the effect of vertical mucosal thickness on the alveolar crest on peri-implant marginal bone loss around crestal and subcrestal placed platform-switching implants.

Before starting the surgery, after the patient is anesthetized, the width of the peri-implant keratinized mucosa and the vertical mucosal thickness over the alveolar crest will be measured. In this study, patients will be divided into 2 main groups with vertical mucosal thickness of 2 mm and less and more than 2 mm, and both groups will consist of 2 subgroups as crestal and subcrestal according to the implant level placed.

It is planned to use the same brand of implant and platform-switch abutment in patients. With standardized control periapical radiographs to be taken as a result of one-year follow-up, the marginal bone loss amount in the implants will be evaluated using software. Routine clinical and radiological measurements will be repeated in all patients at the prosthetic loading session (T0), at 3 months (T1), at 6 months (T2), and 1 year after loading (T3). Pre-surgical radiographs will be taken from the patients who participated in our study, as in all implant patients Clinical measurements.

1. Plaque index (Löe & Silness) and gingival index (Silness & Löe) are obtained by measuring 4 regions of a tooth (mesial, distal, buccal and lingual) with a Williams periodontal probe.

   Attachment loss: It is the value of the distance between a tooth and the free gingiva, based on the enamel-cementum junction, measured using a Williams periodontal probe.

2. Bleeding on probing index (Ainamo & Bay): In this index, probing is performed by gently walking around the pocket. As a result of probing, the evaluation is made by looking at the presence or absence of bleeding in the gingiva. A positive value is given if bleeding occurs within 10-15 seconds after probing in the mesial, distal, buccal and lingual gingival parts of all teeth. The ratio of the bleeding area to the examined area is expressed as %.

3. Keratinized gingival width: It is the distance from the free gingival margin to the mucogingival junction line.

4. Vertical mucosal thickness: It is the distance from the apex of the alveolar crest to the gingival margin. It will be measured with a standardized William type probe.

5. Pocket depth: The vertical distance between the base of the periodontal sulcus and the gingival margin with a standard periodontal probe.

6. Peri-implant pocket depth: It is the vertical distance between the base of the peri-implant sulcus and the gingival margin.

7. Marginal bone level: Radiographic evaluation of the distance between the restoration margin and the bone level.

Sample Selection: Taking the effect size of 0.08 for the significance value in the G Power analysis program as a reference to a previously presented study, 60 implants were planned to be taken for α= 0.05 and 80% power. However, since the study is a long-term control study, it is planned to take 20 implants each, due to the risk of patients not coming to the control sessions. A total of 80 implants will be included.

Statistical analysis method: All analyzes will be done with (Statistical Package for the Social Sciences) SPSS software. In-group temporal evaluations in test and control groups will be evaluated using Paired sample -T or Wilcoxon test according to normal distribution values. For comparisons between groups, the data will be analyzed by independent sample-T or Mann Whitney U test according to their normal distribution. The normal distribution of the data will be evaluated with the Kolmogorov-Smirnov test. The significance value will be taken as 0.05. Relationships between variables will be evaluated with Logistic Regression Analysis or Multivariate Regression Analysis.

Inclusion Criteria:

• >18 years old
• The patient does not have any systemic disease
• Implants are placed in the fully healed alveolar bone
• There is no need for horizontal and vertical augmentation in the area where the implant will be placed.
• Interocclusal distance higher than 7 mm
• Cooperative patients
• At least 9 mm of alveolar bone in the patient's mandible or maxilla in the area where the implant will be placed

Exclusion Criteria:

• Pregnant and lactation
• Mentally retarded patients
• Immediate loading
• Alveolar bone defects
• Smoking more than 10 cigarettes per a day
• Immunsupression or deficiency on bone metabolism

Individual participant data can be shared if the principal investigator is contacted.

Following acceptance of manuscript

Individual participant data can be shared if the principal investigator is contacted.

Participants are assigned a number by hiding their names. While the measurements are being made, the researcher does not know which group the participant belongs to. All radiographic and clinic measurements are collected in one file.