Biologic Response to Crest to Restoration Distance in Subcrestally Placed Implants: A Case Report

Subcrestally placed implants (SPI) offer biological and mechanical advantages; however, their deeper positioning necessitates careful management of the peri-implant soft tissue interface, particularly the Crest to Restoration Distance (CRD). This vertical dimension, extending from the crestal bone to the implant restoration, plays a critical role in peri-implant health. Excessive CRD may result in void formation, bacterial colonization, and peri-implant mucositis, whereas optimizing CRD, including adequate soft tissue thickness (STT), may contribute to peri-implant stability. This study examines the impact of CRD on peri-implant health through a split-mouth case report involving two subcrestally placed implants in a 57-year-old female patient. Three-dimensional analysis using Cone Beam Computed Tomography (CBCT) was performed to measure CRD, Depth of Placement (DP), and Crest Restoration Length (CRL). Clinical assessments included Implant Paper Point Probing (IPPP), Bleeding on Probing (BOP), and other peri-implant health indicators. The test site, corresponding to the upper left first molar implant, initially exhibited excessive CRD, deep probing depths exceeding 3 mm, and clinical signs of mucositis, including BOP, redness, and swelling. Following prosthodontic modification to optimize CRD, mucositis resolved, probing depths stabilized at less than 1 mm, and peri-implant soft tissue health was restored, as confirmed by CBCT. The control site, corresponding to the lower right first molar implant, maintained an optimal CRD from the outset and remained free of peri-implant disease throughout the observation period. These findings suggest that peri-implant mucositis can be managed by modifying implant restoration to optimize CRD, highlighting the potential role of CRD in peri-implant soft tissue stability. Furthermore, the study proposes a new model emphasizing the transitional zone in SPIs; however, additional research is necessary to validate these findings and refine peri-implant soft tissue management strategies.