Volumetric Analysis of Peri-Implant Soft Tissue Changes Between Polyethereketone(PEEK) Anatomic Healing Abutments and Standard Healing Abutments in Posterior Single Implant Restorations

In recent decades, implant supported restorations have evolved into a well-established therapeutic option for restoring a single missing tooth. One of the key factors contributing to their success is the presence of a well-contoured prosthesis that closely mimics the morphology of adjacent teeth. In addition, the restoration must support the health of hard and soft tissues surrounding the peri-implant mucosa. To replicate the peri-implant soft-tissue contour, the conventional workflow employs an analog impression protocol, which may prone to deformation caused by dimensional changes in impression materials or dental stone. This process also requires longer chairside time and may cause patient discomfort. Considering these limitations, digital impressions obtained using intraoral scanners have been introduced to address these challenges .

With advances in computer-aided design and manufacturing (CAD/CAM), the workflow to fabricate implant restorations is commonly carried out using scan body. Once the implant has osseointegrated, the routine clinical protocol involves disconnection of the titanium standard healing abutment,followed by scanning the scan body , peri-implant mucosa contour, the antagonist arch, and occlusal registration. This workflow, however, requires repeated component disconnections, which may lead to peri-implant mucosal collapse and inaccuracies in soft tissue profile replication. Furthermore, the use of standard healing abutment size often creates a circular soft tissue contour, resulting in an unfavourable emergence profile that may require additional surgery or recontouring. Therefore, reproducing the anatomy of the contralateral tooth with a well-contoured implant restorative emergence profile (IREP) is commonly recommended through the use of a custom healing abutment. Several methods have been introduced to fabricate customized healing abutments, including the chairside addition of flowable composite to temporary abutments. In addition, the computer-aided design and computer-aided manufacturing (CAD/CAM) socket seal abutment (SSA) has been proposed to preserve soft and hard-tissue dimensions following implant placement. This workflow includes an additional step of milling the SSA and cementing it to a temporary abutment during the same surgical appointment. However, this approach carries a risk of contamination and requires additional time and cost. Despite these developments, challenges remain with the current use of standard scan bodies. Most standard scan bodies have a conical or cylindrical shape that fails to replicate the natural morphology of a tooth, especially in posterior molar regions. Furthermore, regardless of the patient's gingival phenotype, peri-implant mucosal collapse occurs rapidly often within 20 seconds after losing the physical support following the removal of the customized healing abutment and insertion of the scan body.This soft tissue deviation may cause unstable mucosal margin and exert excessive pressure when delivering final implant restoration, often leading to additional chairside adjustments. To overcome the peri-implant soft tissue deviation and accurate replication, a novel anatomic healing abutment fabricated from polyetheretherketone (PEEK) has been introduced to capture digital impression without removing the healing abutment. This allows one-step formation of an emergence profile that mimics natural tooth anatomy and may reduce the chairside time. Utilizing a predefined emergence profile in the software library, the AHA eliminates the need for additional soft tissue modification, expedites the prosthetic workflow, and includes an identification code for accurate scanning. Despite these advantages, there is currently no clinical evidence validating the use of AHA for preserving peri-implant soft tissue, improving workflow efficiency, crown-fitting accuracy, or evaluating its impact on patientrelated outcomes. This warrants further investigation through controlled clinical evaluation. Therefore, this study aims to evaluate the dimensional changes of peri-implant soft tissue following implant placement in healed sites before and after crown delivery, to assess the immediate and time-dependent soft-tissue stability after standard healing abutment and AHA removal. Additionally, this study will compare the pink white esthetic score (PESWES) , keratinized mucosa width (KMW) , mesiodistal papilla height variation and patient-related outcomes of digital impression workflows using either a standard scan body or AHA for posterior single-implant restorations.