Soft Tissue Augmentation Around Dental Implants Using Connective Tissue Graft, Submerged Tenting Abutment, or Sub-crestal Implant Placement

Overview

Peri-implant soft tissue thickness is an important determinant of the long-term stability and success of dental implants. Patients with a thin peri-implant soft tissue phenotype are at increased risk of soft tissue recession, marginal bone loss, and compromised esthetic and functional outcomes. Subepithelial connective tissue graft (SCTG) is considered the gold standard for soft tissue augmentation; however, it requires harvesting tissue from the palate, increasing surgical complexity, operative time, and postoperative morbidity. Less invasive approaches, including submerged tenting abutments and subcrestal implant placement, have been proposed as alternatives to improve peri-implant soft tissue dimensions while reducing patient morbidity, but direct comparative clinical evidence remains limited. This investigator-initiated, single-center, randomized, parallel-group clinical trial will compare three approaches for peri-implant soft tissue augmentation in patients with a thin peri-implant soft tissue phenotype requiring a single dental implant in the posterior mandible. Eligible implant sites will be randomly assigned in a 1:1:1 allocation ratio to receive either subepithelial connective tissue grafting, submerged tenting abutment placement, or subcrestal implant placement during implant surgery. The primary objective is to compare changes in peri-implant soft tissue thickness using three-dimensional digital intraoral scanning over a 12-month follow-up period. Secondary objectives include evaluation of keratinized tissue width, clinical soft tissue thickness, histological characteristics of peri-implant soft tissue, peri-implant crestal bone level changes, postoperative pain, operative time, patient-reported satisfaction, and postoperative complications. The results of this study are expected to provide evidence regarding whether minimally invasive treatment approaches can achieve clinical outcomes comparable to connective tissue grafting while reducing surgical morbidity and improving patient-centered outcomes.

Peri-implant soft tissue thickness is a critical factor influencing the biological stability, function, and long-term success of dental implant therapy. A thin peri-implant soft tissue phenotype has been associated with increased marginal bone remodeling, soft tissue recession, and compromised peri-implant tissue stability. Consequently, augmentation of peri-implant soft tissues has become an important component of implant treatment planning, particularly in patients with thin soft tissue phenotypes. Subepithelial connective tissue grafting (SCTG) is widely regarded as the reference standard for peri-implant soft tissue augmentation because of its predictable ability to increase tissue volume and improve peri-implant tissue stability. Nevertheless, harvesting autogenous connective tissue from the palate increases operative time, donor-site morbidity, postoperative discomfort, and surgical complexity. These limitations have encouraged the development of less invasive techniques capable of enhancing peri-implant soft tissue dimensions while minimizing patient morbidity. Submerged tenting abutments have recently been introduced as a minimally invasive method for maintaining soft tissue space during submerged healing following implant placement. By supporting the overlying soft tissues throughout the healing phase, these abutments may promote increased soft tissue thickness without the need for connective tissue harvesting. Although preliminary clinical reports have shown encouraging outcomes, direct comparisons with connective tissue grafting remain limited. Subcrestal implant placement has also been proposed as an alternative method for improving peri-implant soft tissue dimensions. Positioning the implant platform approximately 2 mm below the alveolar crest may increase the vertical dimension of peri-implant soft tissues without requiring grafting procedures or additional prosthetic components. While this technique has demonstrated favorable biological behavior in previous studies, evidence directly comparing it with connective tissue grafting and submerged tenting abutments remains scarce. Advances in digital intraoral scanning have enabled accurate, reproducible, and non-invasive three-dimensional assessment of peri-implant soft tissue changes over time. Digital volumetric analysis provides objective measurements while reducing operator-dependent variability associated with conventional clinical measurements. Combining digital assessment with clinical, radiographic, histological, and patient-reported outcomes provides a comprehensive evaluation of treatment effectiveness. This investigator-initiated, single-center, randomized, parallel-group interventional clinical trial will enroll 33 implant sites in medically healthy adults requiring single implant placement in the posterior mandible and presenting with a thin peri-implant soft tissue phenotype (\<2 mm). Implant sites will be randomly allocated in a 1:1:1 ratio to one of three intervention groups: (1) equicrestal implant placement with subepithelial connective tissue grafting, (2) equicrestal implant placement with a submerged tenting abutment, or (3) subcrestal implant placement without grafting or tenting abutment. Randomization will be performed using a computer-generated sequence with allocation concealment through opaque sealed envelopes. Outcome assessors and the biostatistician will remain blinded throughout data collection and analysis, whereas blinding of participants and the operating surgeon is not feasible because of the nature of the surgical interventions. The primary outcome will be the change in peri-implant soft tissue thickness measured by standardized three-dimensional intraoral scanning and digital volumetric analysis. Secondary outcomes include histological characteristics of peri-implant soft tissues, clinical soft tissue thickness, width of keratinized mucosa, peri-implant crestal bone level changes assessed using standardized radiographs, postoperative pain measured using a visual analog scale (VAS), operative time, patient satisfaction measured using the Oral Health Impact Profile-14 (OHIP-14), and postoperative complications. Participants will be followed according to the predefined study schedule for 12 months after implant placement using standardized clinical, digital, radiographic, and patient-reported assessments. The results of this study will provide high-quality comparative evidence regarding three contemporary approaches for peri-implant soft tissue augmentation. By evaluating volumetric, clinical, histological, radiographic, and patient-centered outcomes within the same randomized clinical trial, the study aims to identify treatment strategies that maximize peri-implant soft tissue stability while minimizing surgical morbidity. The findings may contribute to evidence-based decision-making for clinicians managing patients with thin peri-implant soft tissue phenotypes and support the development of less invasive treatment protocols for implant therapy.