Effect of post-surgical flap position on soft tissue regrowth and keratinized tissue increase following fibre retention osseous resective surgery: a 6-month randomized study with multilevel analysis

BACKGROUND: The aim of this randomized split-mouth study was to assess the influence of primary flap position on the amount of coronal soft tissue regrowth and keratinized tissue (KT) 6 months after osseous resective surgery with fiber retention technique (FibReORS). MATERIALS AND METHODS: Two contralateral posterior sextants in 16 patients were treated with FibReORS and randomly assigned to flap positioning either 2 mm below the bone crest (apical group) or at the level of bone crest (crestal group). Clinical parameters were recorded at 1, 3 and 6 months and patient-related outcomes during the first two post-operative weeks. RESULTS: Healing period was uneventful. Patient’s discomfort was similar in both groups. The overall soft tissue rebound was higher in the apical than in the crestal group (2.0 ± 1.3 mm versus 1.3 ± 0.7 mm), but the difference was statistically significant only interproximally (2.2 ± 1.3 mm versus 1.6 ± 0.8 mm). Multilevel analyses showed higher soft tissue rebound in sites with normal compared to thin phenotype (1.5 mm, p < 0.0001) and treated with flap positioned 2 mm apically to the bone crest (0.7 mm, p < 0.001). An additional 0.5 mm KT increase was observed at interdental sites in the apical group. CONCLUSIONS: Apical flap positioning increases soft tissue rebound and KT width, mainly at the interdental sites, with reduced patient discomfort. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov (ID: NCT05140681, Registration date: 1/12/2021, retrospectively registered). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-023-03144-2.