AIM; To investigate the effects of high altiude hypoxia on bacterial type, quantity and endotoxinlevel in subgingival plague in a rabbit periodontitis model . METHODS: Forty male rabbits were divided randomly into four groups ( normoxia control group, normoxia ligated group, hypoxia control group and hypoxia ligated group). Both mandibular central incisors of the ligated groups, which were raised using periodontitis diets, were ligated by steel ligature. The hypoxia groups were raised under hypoxia environment ( simulating an altitude of 5000 meters, 23 h per day), periodontal depth (PD) , attachement loss (AL) , plaque index (PLI) and gingival index (GI) were measured 8 weeks after ligation. The pH value of gingival crevicular fluid (GCF) was determined by pH test strips. Subgingival plagues were collected for subsequent isolation and anaerobic culture. RESULTS: Clinical indices (including AL, PLI and GI) , GCF pH value, viable bacterial count and endotoxin level in hypoxia ligated group were significantly higher than those in other groups ( P < 0. 05 ) . Correlation analysis showed that GCF pH value and viable hacterial count were positively correlated with AL, PLI and GI. Endotoxin was positively correlated with AL. CONCLUSION: Hypoxia environment is more conducive to the settlement of gram negative anaerobes, which leads to the increase of oxygen consumption and the decrease of redox potential, resulting in elevation of pH value in periodontal pockets .%目的:探讨高原低氧环境对兔龈下菌斑中定植的细菌种类、数量和内毒素水平的影响.方法:40只雄性大白兔随机分为平原对照组、平原实验组、高原对照组和高原实验组,每组10只,两实验组采用正畸丝结扎下颌中切牙并联合牙周炎食谱饲养的方法建立牙周炎模型,同时,两高原组送入低压氧舱(模拟海拔高度5 000m,23 h/d)内饲养.8周后检测牙周探诊深度(PD),附着丧失(AL)、菌斑指数(PLI)、牙龈指数(GI),pH试纸检测龈沟液pH值,采集龈下菌斑进行厌氧菌分离、培养、计数、镜检、内毒素检测.结果:高原实验组AL、PLI、GI等临床牙周指标以及龈沟液pH值、活菌数、内毒素水平等均明显高于其他各组(P＜0.05),且细菌种类更为丰富；相关分析显示,龈沟液pH值、活菌数与AL、PLI、GI呈正相关,内毒素水平与AL呈正相关.结论:高原低压低氧的特殊环境更利于G-厌氧菌的定居,使牙周袋内氧气消耗量增加,pH值升高.
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