Abstract: Objective: To investigate the influence of keratinized mucosa width (KMW) on peri-implant hard- and soft-tissue conditions and to evaluate the clinical efficacy of the modified free gingival graft (MFGG) with buccal flap repositioning for graft stabilization, thereby ascertaining its effectiveness and advantages in enhancing peri-implant health. Methods: A total of 79 implants in 59 patients treated between 2017 and 2024 were retrospectively enrolled and stratified into three groups: (1) group A: adequate KMW, 24 implants in 20 patients; (2) group B: insufficient KMW, 33 implants in 22 patients; and (3) group C: insufficient KMW subsequently managed with MFGG, 22 implants in 17 patients. Group C was further divided into a prophylactic augmentation subgroup (C1: 14 implants in 10 patients) and a therapeutic augmentation subgroup (C2: 8 implants in 7 patients). Peri-implant tissue parameters were systematically recorded and compared across groups, including KMW, probing depth (PD), modified plaque index (mPLI), modified sulcus bleeding index (mSBI), marginal bone loss (MBL), graft contraction rate, postoperative pain, and mucosal scarring index (MSI). Results: (1) Peri-implant disease (PID)-related indices: ① Inter-group comparison between groups A and B revealed no statistically significant difference in PD (P>0.05). mPLI, mSBI, and MBL were all significantly higher in group B than in group A (P<0.05). ② The prevalence of peri-implant mucositis (PIM) and peri-implantitis (PI) in group B was markedly higher than in group A (P<0.05), whereas the incidence of PI in group B was only slightly elevated relative to group A, a difference that did not reach statistical significance (P>0.05). (2) Efficacy indices of the MFGG procedure: ① All grafts in group C achieved complete survival, yielding a surgical success rate of 100 %. Pain had largely resolved by post-operative day 7; discomfort was predominantly localized to the hard-palate donor site. ② At 3 months (T2) post-surgery, the graft contraction rate was 25.2 %, increasing to 30.1 % at 6 months (T3). ③ At 6 months, no significant difference in PD was observed between groups C and B (P>0.05). Both mPLI_T3 and mSBI_T3 were significantly lower in group C than in group B (P<0.05). Subgroup C1 exhibited significantly less MBLT3 than group B (P<0.05). The incidence of PID_T3 in group C differed significantly from that in group B (P<0.05). ④ In subgroup C2, comparison of data at 6 months (T3) with baseline (T0) showed no significant change in PD (PD_T3 vs PD_T0, P>0.05), whereas both mPLI_T3 and mSBI_T3 were significantly reduced relative to mPLI_T0 and mSBI_T0 (P<0.05). MBL_T3 did not differ significantly from MBL_T0 (P>0.05). ⑤ At 6 months, the modified sulcus bleeding index (MSI_T3: 2.12±0.60) was slightly lower than at 3 months (MSI_T2: 2.41±0.94); this change was not statistically significant (P>0.05). Conclusion: KMW is positively correlated with the health of peri-implant hard and soft tissues; implants with adequate KMW demonstrate a significantly lower incidence of peri-implant diseases. MFGG technique, employing buccal flap repositioning, enhances graft survival, is technically straightforward, and elicits minimal postoperative morbidity. Clinical application of this surgical modality for peri-implant keratinized mucosa augmentation demonstrates favorable efficacy, conferring effective prevention of peri-implant diseases, amelioration of soft-tissue inflammation, and reduction in marginal bone resorption risk.

Key words: dental implant, keratinized mucosa width, peri-implant disease, free gingival graft