Soft Tissue Management in Subcrestal Dental Implants

The goal of this randomized clinical trial is to investigate the influence of supracrestal soft tissue on abutments of different heights (2-mm vs. 3-mm) and shapes (cylindrical abutment vs. concave abutment) on changes in the marginal bone level (bone loss and bone remodeling) in healthy, partially edentulous volunteer patients undergoing implant-supported rehabilitation. The main questions it aims to answer are: * Is there any difference in marginal bone loss for different abutment shapes and heights? * Do the shape and height of the abutment affect implant success? All participants will receive bone-level dental implants placed approximately 2-mm below the bone crest, each receiving a different type of abutment and researchers will see whether the shape and height of the abutment influence the success of the implant, periodontal probing depth (PPD), and bleeding on probing (BoP) comparing four groups of patients: 1. 2-mm high abutments with cylindrical shape. 2. 2-mm high abutments with concave shape. 3. 3-mm high abutments with cylindrical shape. 4. 3-mm high abutments with concave shape. Clinical and radiographic assessments will be performed at abutment placement, at definitive prosthesis placement, and at 1, 3, 6, and 12 months after loading to measure marginal bone loss and peri-implant parameters.

The primary aim of this randomized clinical trial is to evaluate the influence of subcrestal implant placement depth (-2 mm vs -4 mm) on peri-implant marginal bone level changes, including marginal bone loss and bone remodeling. Secondary outcomes include implant success, peri-implant probing depth (PPD), and bleeding on probing (BoP). Partially edentulous patients requiring fixed implant-supported prosthetic rehabilitation with two implants in posterior maxillary or mandibular regions will be included. Implants will be placed subcrestally at either -2 mm or -4 mm from the bone crest, following a submerged healing protocol. Allocation to insertion depth will be randomized. Marginal bone level changes will be assessed using standardized periapical radiographs at second-stage surgery, prosthesis placement, and at 1, 3, 6, and 12 months after functional loading. PPD and BoP will be recorded at the same time points.

This clinical trial investigates the biological and clinical outcomes of immediate implant placement in aesthetic areas presenting with buccal bone dehiscence. Traditionally, these defects are treated with a bone graft and covered using a collagen membrane; however, there is ongoing debate about whether the membrane is necessary for optimal regeneration. This study proposes the use of a connective tissue graft instead of a collagen membrane, aiming to improve soft tissue volume and aesthetics without compromising bone healing. The objective of the study is to evaluate whether the use of an autogenous connective tissue graft in combination with a deproteinized bovine bone mineral with collagen (DBBM-C) achieves results that are not inferior to the conventional protocol that uses DBBM-C and a collagen membrane. The main outcome variable is the vertical buccal bone gain measured after twelve months of healing. The study design is a randomized controlled clinical trial including twenty-four patients divided equally into two groups. Each participant will attend eight follow-up visits over twelve months. After atraumatic tooth extraction, immediate implants (BLC, Straumann) will be placed using a prosthetically guided protocol. Buccal dehiscence will be measured intraoperatively, and a partial-thickness tunnel flap will be prepared to allow soft tissue adaptation and graft placement. In the control group, the defect will be filled with DBBM-C and covered with a collagen membrane stabilized with horizontal mattress sutures. In the test group, the defect will receive DBBM-C covered by a connective tissue graft harvested from the palate and fixed in a similar manner. When primary stability is equal to or greater than 35 N/cm, an immediate screw-retained provisional crown will be delivered; if stability is lower, a customized healing abutment or Maryland-type provisional will be used instead. After three months, digital impressions will be taken to fabricate the definitive zirconia restoration. All restorative steps will be performed by experienced clinicians using a standardized digital workflow. Patients will follow routine postoperative care instructions, including soft diet and restricted brushing in the surgical area for one week. The main benefits of this study include advancing the understanding of regeneration strategies for buccal bone dehiscence and improving clinical decision-making in immediate implant protocols. Participants are also expected to benefit from implant-supported rehabilitation, functional restoration, and aesthetic improvement. The potential risks are minimal and limited to typical surgical complications such as discomfort, swelling, or minor infection, which will be managed following established clinical protocols. If a patient declines participation, conventional implant treatment will be offered, or alternative prosthetic options such as fixed or removable restorations will be provided. Any intra- or postoperative complications during the study will be treated promptly and documented according to institutional standards. The biomaterials used include BLC Straumann implants, Bio-Oss Collagen (DBBM-C), Bio-Gide collagen membranes, and appropriate suture materials. Procedures will employ standard periodontal and tunneling instruments, as well as a digital intraoral scanner for accurate prosthetic fabrication. Statistical analysis will involve descriptive and inferential methods. The Kolmogorov-Smirnov test will assess normality, and mixed ANOVA models will evaluate differences between groups and across time points. Covariate adjustment will be performed using ANCOVA when necessary, and intra- and inter-examiner reliability will be tested with the intraclass correlation coefficient. The level of statistical significance will be set at 0.05. The expected outcome is that the use of an autogenous connective tissue graft will demonstrate bone regeneration results equivalent to those obtained with a collagen membrane, while potentially improving soft tissue thickness and aesthetic integration. This finding would support the clinical use of soft tissue grafts as an alternative to collagen membranes in immediate implant placement within aesthetic regions showing buccal dehiscence. All study procedures follow the principles of the Declaration of Helsinki and ethical standards for human clinical research. Participants will receive detailed information about the study protocol and will sign informed consent before inclusion. In summary, this study aims to determine whether a connective tissue graft can safely replace a collagen membrane in the management of buccal dehiscence during immediate implant placement, offering comparable regenerative outcomes with possible superior soft tissue aesthetics.