The histological changes of soft tissue reconstruction in palate and peri‐implant after free gingival graft

Background The existent of keratinized mucosa around dental implants has been deemed as one of the important factors of peri-implant health. Free gingival graft (FGG) has been assumed as an effective technique for increasing the keratinized mucosa width with palatal autograft harvesting. However, there is insufficient evidence about whether the new tissue in donor areas are identical to the normal tissue in histology, and how the autografts change after transplant in recipient areas in histology. Aim/Hypothesis This study is aimed to investigate the histological changes in donor and recipient areas of human after FGG at different postoperative time by visual observation and HE staining. To verify the FGG effects on increasing keratinized gingiva width and postoperative would healing of palatal mucosa. Material and Methods Of 24 patients with insufficient peri-implant keratinized mucosa width were selected. All the patients received FGG surgery at second stage operation. Postoperative instructions included wearing a pair of artificial plastic splints for the first 48 h (the maxillary one is used for protecting the palatal wound, and the mandibular one is to fix the grafts in the correct position with no pressure), avoiding mechanical or thermal stimulation in surgical areas for 2 weeks. During the follow-up visits, photographs of both donor and recipient areas were taken. Marginal bone level, soft tissue peri-implant parameters were assessed after the final crown placement and subsequent visits from then on. 2 patients agreed to take biopsies. HE staining was performed to observe and compare the growth of newly grown tissue in palate after skin removal and the status of soft tissue reconstruction in implant sites after skin grafting. All samples above were obtained by patient agreement with the knowledge. Ethic approval was obtained from the local committees. Results 1, After a month of healing, there was no significant difference in color and texture between the wounds and adjacent tissues. At the time of thread removal (14 days post-surgery), the autologous skin grafts in the recipient areas had formed a good connection with the surrounding tissues. 2, All the patients have completed the final restoration, and the longest one is up to 12 months. Until now, no implant has shown healthy problems in both soft tissue and bone. But the long-term effect still needs longer observation time. 3, HE staining showed (i) Compared with normal palatal epithelium, the whole epithelium of newly grown tissue in donor areas was thinner, which was manifested by the decrease of stratum spinosum and the disappearance of epithelial pegs. (ii) Comparing to the natural gingival tissue, the epithelial pegs are longer at peri-implant keratinized mucosa, which was formed by the grafts. (iii) No differences in lamina propria structure had been found. Conclusion and Clinical Implications 1, Mucosal tissue structure of donor site do change after operation, but it remains to be seen whether the donor site can restore normal palatal epithelium structure after a longer period of healing. 2, The keratinization of the soft tissue in the recipient area is slightly better than that of the natural gingiva, which means that the graft sites may have a stronger ability of anti-friction and anti-inflammatory. But whether this conclusion is of general application still needs more samples.