Dynamic changes of peri-implant soft tissue after interim restoration removal during a digital intraoral scan

During a digital intraoral scan for an esthetic implant restoration, the peri-implant soft tissue will collapse rapidly after the interim restoration (IR) is removed, making it difficult to replicate the established emergence profile. The rate of this collapse is unclear.

The purpose of this clinical study was to determine whether significant dimension differences could be found between peri-implant soft tissue supported by an IR and that immediately after removal of the restoration and to assess the changes over time.

Optical scans were made of 12 single implant sites in the esthetic zone of 10 participants. The scans in the first group replicated the peri-implant soft tissue contour with the support of the IR; in the second group, scans were made at different times from 0 seconds to 20 minutes after removal of the restoration. The changes in the soft tissue contour, including the height of the mesial papilla, distal papilla, and gingival margin, the facial and palatal soft tissue thickness, and emergence profile discrepancies (EPDs), were assessed. A linear mixed model was built to estimate the EPD.

After the removal of IR, the palatal soft tissue thickness increased over time, and only minimal changes were found in the height of the mesial papilla, distal papilla, and gingival margin (up to -0.27 mm at 20 minutes). A significant EPD was immediately present at all the measurement sites after the removal of the IR. The linear mixed model showed a significant positive correlation between the natural logarithm of time and EPD. Significant positive correlations between gingiva thickness/implant depth and EPD were only seen at some of the sites.

A small reduction in the papilla level occurred, but no clinical influence on the proximal contact design of the restoration was detected. For the emergence profile, a significant but small discrepancy occurred immediately and continued to increase over time.