Morphology of Peri-Implant Tissues Around Permanent Prostheses With Various Emergence Angles Following Free Gingival Grafting

Abstract

Purpose: To analyze the tissue morphology around implant-supported prostheses by digital technology and to evaluate the effect of prosthetic contours on the changes in tissues following the free gingiva graft procedure.

Material and methods: A total of 53 implants in 32 patients receiving free gingiva grafts were selected. These had previously presented insufficient keratinized mucosa width (KMW). At the follow-up visits (mean: 16.66 ± 9.97 months), the implant position and tissue condition were documented with an oral scanner. Vertical soft tissue thickness (VT), measured from the implant-abutment connection to the marginal tissues, and horizontal soft tissue thickness (HT), at the level of the platform, were calculated. The VT, HT, and emergence angle (EA) of prostheses were assessed by 3Shape analyzing software. The final KMW was measured by clinical assessment. Marginal bone loss (MBL) was calculated in the follow-up bitewing radiographs.

Results: The mean VT in the study was 2.65 ± 0.75 mm at the mid-buccal sites, 3.74 ± 1.22 mm at the mesial, 3.16 ± 1.08 mm at the distal, and 2.53 ± 0.92 at the mid-lingual aspects. The mid-buccal HT was 1.45 ± 0.53 mm while the mid-lingual was 1.05 ± 0.43 mm (p = 0.008). Interestingly, prostheses with mid-buccal EA $>$ 30° exhibited slightly lower VT, but higher HT, than the ones with EA $\le$ 30°. Prostheses with proximal EA > 30° displayed slightly more MBL, compared to prostheses with EA $\le$ 30°. The mean KMW was 4.08 ± 1.10 mm.

Conclusions: Free gingival grafting is a predictable treatment approach to augmenting soft tissue 3-dimensionally. Prostheses with EA $\le$ 30° were preferable for preserving the maximal VT and maintaining crestal bone stability.

Keywords: Dental implants; dental prosthesis; emergence angle; peri-implant mucosa; tissue transplantation.