对不同时机的游离龈移植术（FGG）增加下颌后牙区种植体周颊侧角化龈的临床效果进行评价。

选择2018年10月至2020年10月就诊于东莞健力口腔医院修复种植科下颌后牙区单牙缺失角化牙龈不足的患者（宽度为2 ~ 4 mm）共40例，将纳入的40例患者进行编号，以随机数字表法抽取20例为实验组，其余20例为对照组。实验组种植Ⅰ期手术时放置愈合基台同期行FGG。对照组种植Ⅰ期手术潜入式愈合，3个月Ⅱ期手术时放置愈合基台同期行FGG。术后观察移植物的存活情况，测量术前牙槽嵴顶剩余角化龈宽度，测量颊侧FGG后即刻、移植术后2个月、戴牙后即刻和戴牙后6个月的颊侧角化龈宽度，使用SPSS 20.0软件对移植物存活率、颊侧不同时间点角化龈宽度等进行统计分析，采用配对t检验进行比较，以P<0.05认为差异有统计学意义。

两组手术均获得成功，伤口正常愈合，组织瓣均存活。术前实验组和对照组牙槽嵴顶余留角化龈宽度分别为（2.9 ± 0.3）和（3.0 ± 0.3）mm，差异无统计学意义。实验组和对照组术后即刻种植体颊侧龈缘中点角化龈宽度分别为（4.9 ± 0.5）和（4.9 ± 0.5）mm，差异无统计学意义（t = 0.2，P = 0.8）。实验组和对照组术后2个月颊侧龈缘中点角化龈宽度分别为（4.2 ± 0.4）和（4.5 ± 0.4）mm，差异有统计学意义（t = -2.9，P<0.05）。实验组和对照组戴牙当天种植体颊侧龈缘中点角化龈宽度为（3.2± 0.4）和（3.7± 0.5）mm，差异有统计学意义（t = -2.6，P<0.05）。实验组和对照组戴牙后6个月种植体颊侧龈缘中点角化龈宽度为（3.1 ± 0.4）和（3.5 ± 0.3）mm，差异有统计学意义（t = -3.7，P<0.05）。

当下颌后牙区剩余角化龈为2 ~ 4 mm时，FGG在种植Ⅰ期手术同期及Ⅱ期手术同期均能获得较好的增加角化龈的效果。相比于种植Ⅰ期手术同期进行FGG，Ⅱ期手术同期FGG能获得更好的颊侧角化龈的宽度，但会增加手术次数。

To evaluate the clinical effect of peri-implant free gingival grafting (FGG) at different timing in the posterior mandible.

A total of 40 patients with keratinized gingival insufficiency (with a width of 2 to 4 mm) of a single missing tooth in the posterior mandibular area were selected from the Department of Implant Restoration, Dongguan Jianli Stomatological Hospital, from October 2018 to October 2020. The patients were randomly divided into experimental and control group. In the experimental group, the healing abutment was placed during the first-stage surgery and FGG was performed at the same time. In the control group, submerged healing was performed in the first-stage surgery, and in the second-stage surgery in 3 months, FGG was performed and the healing abutment was placed at the same time. The survival of the graft was observed after surgery. The width of the remaining keratinized gingiva on the alveolar ridge was measured before operation. The width of the buccal FGG immediately after the operation, the width of the keratinized gingiva in 2 months after transplantation, the keratinized gingiva immediately after crown delivery, and the width of the buccal keratinized gingiva 6 months after crown delivery were measured.

The operations in both groups were successful. The wounds healed normally, and the tissue flaps survived. The width of the remaining keratinized gingiva on the alveolar crest of the experimental and control group before surgery were (2.9 ± 0.3) and (3.0 ± 0.3) mm, respectively, and there was no significant difference between the two groups. The width of the keratinized gingiva measured at the midpoint of the buccal gingival margin of the experimental and control group immediately after surgery was (4.9 ± 0.5) and (4.9 ± 0.5) mm, respectively, and the difference was not statistically significant (t = 0.2, P = 0.8) . Besides, the width of the keratinized gingiva measured at the midpoint of the buccal gingival margin in 2 months after operation was (4.2 ± 0.4) and (4.5 ± 0.4) mm, respectively, and the difference was statistically significant (t = -2.9, P<0.05) . In addition, the width of the keratinized gingiva at the midpoint of the buccal gingival margin of the implant measured on the day of crown delivery was (3.2 ± 0.4) and (3.7 ± 0.5) mm, and the difference was statistically significant (t = -2.6, P<0.05) . Moreover, the width of the keratinized gingiva at the midpoint of the buccal gingival margin of the implant measured in 6 months after teeth placement was (3.1 ± 0.4) and (3.5 ± 0.3) mm, and the difference was statistically significant (t = -3.7, P<0.05) .

When the width of the residual keratinized gingiva in the posterior mandibular area is 2 to 4 mm, FGG can achieve better effects of increasing keratinized gingiva at both the first- and second-stage surgery. Compared with the first-stage surgery, FGG performed at the second-stage surgery can achieve higher width of the buccal keratinized gingiva, the drawback of more operations.