Prosthetic Management of Peri-Implant Mucositis via CRD Optimization: A Split-Mouth Case Report

Background: Subcrestally placed implants (SPIs) present advantages for bone preservation and soft tissue support but pose challenges in maintaining peri-implant soft tissue health. This case explores the role of Crest to Restoration Distance (CRD) in the development and resolution of peri-implant mucositis. Case Presentation: A 57-year-old woman received two SPIs—one in the upper left and one in the lower right first molar region. Despite similar implant systems and prosthetic protocols, the upper left implant developed mucositis, characterized by bleeding on probing and discomfort, while the lower right implant remained stable. Three-dimensional analysis using cone-beam computed tomography (CBCT) revealed excessive CRD at the affected site. Results: After prosthodontic revision to reduce the CRD, clinical signs of mucositis resolved, with probing depths reduced to less than 1 mm and no bleeding on probing. The control site remained healthy throughout the observation period. Practical Implications: This case highlights CRD as a modifiable prosthetic factor influencing soft tissue stability. A three-zone model—comprising the sulcus, transitional zone (TZ), and subcrestal zone (SZ)—is introduced to provide a biologically grounded framework for understanding soft tissue adaptation around SPIs.