Influence of Vertical Implant Position on Marginal Bone Loss in Cases With Thin Phenotype

Preservation of crestal bone is crucial and must be prioritized from the onset of implant placement. Adequate amount of peri-implant bone contributes to esthetic success and implant stability. Crestal bone contributes to both esthetics and function. Resorption of crestal bone is seen as loss of interproximal papillary support and gingival recession, which gives way to peri-implantitis and compromises esthetics (Degidi et al., 2011).

With respect to the depth of insertion, implants can be placed at various levels in the bone, which affects the peri-implant tissues with the surrounding marginal bone. Therefore, placement of an implant in a deeper position with respect to the bone crest (subcrestal placement) has been suggested as a method that could contribute to maintain the peri-implant soft and hard tissues in comparison with crestal placement, though this affirmation is subject to controversy (Pellicer-Chover et al., 2019).

Study will be conducted in the Oral Medicine and Periodontology department, Faculty of Dentistry, Cairo University, Egypt.

Patients will be selected from the outpatient clinic of the department of Oral Medicine and Periodontology-Cairo University.

Each patient will be examined to confirm meeting the eligibility criteria. A full medical and dental history will be taken, and proper oral examination will be performed. Then a pre-operative cone beam computed tomography (CBCT) will be taken to examine both the bucco-lingual bone dimension and bone height and to ensure that the area of interest is free of any pathological lesions.

All the steps will be explained in detail to each patient and an informed consent will be taken from the patient to agree on their enrolment in the clinical trial. Then the patient will be treated first by phase I therapy for periodontal treatment through conventional supragingival scaling and subgingival debridement. Then strict oral hygiene instructions will be given and patients will be reassessed after a period of 4 weeks. Reassessment of the case is to ensure absence of any signs of inflammation and presence of normal tissues before the surgical procedure.

Clinical photographs will be taken at baseline, during surgery and at 3, 6 and 12 months postoperatively.

The patients will be randomly assigned into two groups:

Intervention group: Patients receiving delayed implant placed 2 mm subcrestal with immediate temporization

Control group: Patients receiving delayed implant placed equicrestal with immediate temporization

Surgical procedure:

1. Topical anesthesia will be administered using infiltration technique in the labial and palatal sides of the area of interest. 2. Full-thickness midcrestal incision to expose the bone. 3. Implant insertion will be performed according to the manufacturer's instructions; drills will be used sequentially until the required implant diameter is reached with insertion of the paralleling pin in the osteotomy site to evaluate the proper position in bucco-lingual and mesio-distal direction 4. Then the implant will be placed Intervention group: inserted 2 mm apical to the alveolar bone crest with adequate primary stability.

Control group: inserted at the same level of the alveolar bone crest with adequate primary stability. 5. After implant insertion, a healing collar will be placed over the implant. Then the flap will be repositioned and sutured. 6. After suturing, the healing collar will be removed and a scan body will be inserted for digital impression and immediate temporary PMMA crown will be delivered over a temporary abutment for both groups.

Postoperative Care:

Postoperative medication:

Administration of:

1. Antiseptic mouth rinse with Chlorhexidine (0.12%) two times a day for 1 week. 2. Anti-inflammatory drugs (NSAIDS; Ibuprofen 400 mg three times daily for 3 days). 3. Antibiotic (Hibiotic 1gm) will be prescribed for the patient twice daily for one week.

Patient self-care instructions:

Post-operative instructions:

1. Each patient will be instructed to apply cold fomentation for the first 6 hours. 2. Avoid tooth-brushing at the surgical site for the first 14 days and proper rinsing after every meal starting from the second day. 3. Hot beverages will not be permitted for the first 24 hours. 4. Each patient will be instructed to rinse with Chlorohexidine mouthwash every 12 hours for 14 days. 5. The patient will be asked to contact the operator for any unexpected complications. 6. The sutures will be removed 10 days post-operative.

Follow-up:

Each patient will be evaluated at 3, 6, 9 and 12 months post-operatively.

• Midfacial recession [Time frame: 0, 3, 6, 9, 12 months post-operative]
• Pink Esthetic Score (PES) [Time frame: baseline, 3, 6, 9, 12 months post-operative]
• Gingival thickness [Time frame: baseline, 3, 6, 9, 12 months post-operative]
• Implant survival [Time frame: 12 months post-operative]
• Post-operative patient satisfaction [Time frame: 12 months post-operative]
• Radiographic horizontal bucco-palatal bone changes [Time frame: baseline, 12 months post-operative]
• Radiographic vertical bone changes [Time frame: baseline, 12 months post-operative]
• Emergence angle [Time frame: baseline, 12 months]