目的: 分析Ⅲ期或Ⅳ期牙周炎患者龈沟液(gingival crevicular fluid，GCF)中甲酸、丙酸和丁酸的浓度及其与牙周炎的关系。方法: 选择2008年2月至2011年5月于北京大学口腔医院牙周科就诊的37例全身健康的牙周炎患者作为病例组，选择同期19例全身及牙周健康志愿者作为对照组。每位研究对象每象限选一颗磨牙或切牙的颊侧近中位点采集龈沟液，并记录菌斑指数(plaque index，PLI)、探诊深度(probing depth，PD)、出血指数(bleeding index，BI)和附着丧失(attachment loss，AL)。分离上清液采用高效毛细管电泳技术检测甲酸、丙酸和丁酸的浓度，分析其对牙周炎患病风险的预测能力，以及与牙周炎分级的相关性。结果: 病例组37例牙周炎患者按分期32例为Ⅲ期和5例为Ⅳ期，按分级9名为B级和28名为C级。病例组患者的临床指标均显著高于对照组(P＜0.001)，龈沟液中甲酸含量明显低于对照组[5.37(3.39，8.49) mmol/L vs. 12.29(8.35，16.57) mmol/L，P＜0.001]，而丙酸和丁酸浓度均显著高于对照组[10.23(4.28，14.90) mmol/L vs. 2.71(0.00，4.25) mmol/L，P＜0.001；2.63(0.47，3.81) mmol/L vs. 0.00(0.00，0.24) mmol/L，P＜0.001]。B级和C级牙周炎龈沟液中甲酸、丙酸和丁酸的浓度差异无统计学意义(P＞0.05)。而深袋内丙酸和丁酸的浓度明显高于浅袋，甲酸浓度随袋深的增加反而减少。丙酸(OR=1.51，95%CI：1.29~1.75)和丁酸(OR=3.72，95%CI：1.93~7.17)是牙周炎的危险因素，而甲酸(OR=0.87，95%CI：0.81~0.93)则可能是牙周炎的保护因素。丙酸(AUC=0.852，95%CI：0.805~0.900)、丁酸(AUC=0.889，95%CI：0.841~0.937)、甲酸浓度的倒数(AUC=0.844，95%CI：0.793~0.895)对牙周炎的患病风险具有良好的预测能力。结论: 牙周炎患者龈沟液中甲酸浓度低于对照组，是牙周炎的保护因素，甲酸浓度的倒数对牙周炎患病风险具有良好预测效能；而丙酸和丁酸浓度则升高，是疾病的危险因素，对牙周炎患病风险均具有良好预测价值；三种有机酸浓度随探诊深度而变化，但与牙周炎的分级无明显相关性。

Objective: To analyze the concentration of formic acid, propionic acid and butyric acid in gingival crevicular fluid (GCF) of patients with stages Ⅲ and Ⅳ periodontitis, and their relationship with periodontitis. Methods: The study enrolled 37 systemically healthy patients with periodontitis and 19 healthy controls who visited Department of Periodontology, Peking University School and Hospital of Stomatology from February 2008 to May 2011. Their GCFs were collected from the mesial-buccal site of one molar or incisor in each quadrant. Periodontal clinical parameters, including plaque index(PLI), probing depth(PD), bleeding index(BI), and attachment loss(AL). Concentrations of formic acid, propionic acid and butyric acid in the supernatant of the GCFs were analyzed by high-performance capillary electrophoresis (HPCE). The prediction ability of formic acid, propionic acid and butyric acid with the risk of periodontitis and the differences between grade B and grade C periodontitis were analyzed. Results: In this study, 32 patients with stage Ⅲ and 5 patients with stage Ⅳ were enrolled, including 9 patients with grade B and 28 patients with grade C. Clinical periodontal variables in the patients with periodontitis were significantly higher than those in the control group (P<0.001). Formic acid was significantly lower in periodontitis than that in the control group [5.37 (3.39, 8.49) mmol/L vs. 12.29 (8.35, 16.57) mmol/L, P<0.001]. Propionic acid and butyric acid in periodontitis were significantly higher than those in the control group: Propionic acid, 10.23 (4.28, 14.90) mmol/L vs. 2.71 (0.00, 4.25) mmol/L, P < 0.001; butyric acid, 2.63 (0.47, 3.81) mmol/L vs. 0.00 (0.00, 0.24) mmol/L, P<0.001. There was no significant difference in formic acid, propionic acid and butyric acid concentrations between grade B and grade C periodontitis (P>0.05). Propionic acid and butyric acid in the deep pocket were significantly higher than in the shallow pocket, while the concentration of formic acid decreased with the increase of PD. Propionic acid (OR=1.51, 95%CI: 1.29-1.75) and butyric acid (OR=3.72, 95%CI: 1.93-7.17) were risk factors for periodontitis, while formic acid (OR=0.87, 95%CI: 0.81-0.93) might be a protective factor for periodontitis. Propionic acid (AUC=0.852, 95%CI: 0.805－0.900), butyric acid (AUC=0.889, 95%CI: 0.841－0.937), f (formic acid, AUC=0.844, 95%CI: 0.793－0.895) demonstrated a good predictive capacity for the risk of periodontitis. Conclusion: The concentration of formic acid decrease in the GCF of periodontitis patients, which is a protective factor for periodontitis, its reciprocal have good predictive capacity. However, propionic acid and butyric acid increase, which are risk factors for periodontitis and have good predictive capacity. The concentration of formic acid, propionic acid, and butyric acid vary with probing depth, but there is no significant difference between grade B and grade C periodontitis.