Distribution Of Subgingival Microbial Category In Periodontitis Rabbits Under Simulated High Altitude Hypoxia Condition

OBJECTIVEChronic periodontitis is a chronic infectious disease which caused by microorganismsin dental plaque. It is the main reason of teeth lose in adults. the prevalence ofperiodontitis is up to70.2percent in altitude environment, which was significantly higherthan that of plain environment.Periodontal bacterium is the initiating factor of periodontitis. It is confirmed that morethan ten kinds of suspicious pathogens are connected with the occurrence of periodontitis.The main periodontal pathogen are different with the different etiological factors andspecies of periodontitis. In high altitude environment, the periodontitis patients underhypoxic conditions and their immune function、cytokine levels in gingival crevicular fluid、pH and O2partial pressure are not the same as the patients living in plain environment.Periodontal plaque microbial species、composition and even their virulence factors havebeen affected under the changes in systemic factors and the regulation ofmicro-environment. It is unclear about the difference of the main pathogenic bacteria ofperiodontits in the normal oxygen and in the high altitude hypoxia conditions.From this reason, this research investigated the difference of the main pathogenicbacteria of periodontits of subgingival plaque in the normal oxygen and high altitudehypoxia conditions with model of rabbit. the relationship between periodontitis and thealtitude hypoxia environment was explored.METHODSStudy subjects 1. A total of forty clean level rabbit were divided randomly into four groups:normaloxygen periodontitis group,normal control group,hypoxia periodontitis group,hypoxiacontrol group.The periodontitis groups were received ligation of augnathus anterior teeth bysteel ligature and high-carbonhydratediet; the hypoxia perodontitis group was raised in lowpressure oxygen tank simulated altitude of5000m,23hous per day, during8weeks.genomic DNA in subgingival plaque were extracted after eight weeks.2. Measurement of clinical periodontal conditionClinical periodontal parameters included probing depth(PD),clinical attachmentlevel(CAL),sulcus bleeding index(SBI) and mobility(M) were measured and recorded byexaminer.3. Samples collectionSampling sites across the wet, remove the supragingival plaque, scraping subgingivalplaque with a sterile curette from the very bottom of the periodontal pocket, placed insterile EP tube at-70℃to save.4. Detection of pathogensPathogens genomic DNA were extracted by bacteria DNA kit from plaque andstandard strains of bacteria, A16S rDNA-based polymerase chain reaction(PCR) detectionmethod was used to determine the prevalence of Pg、Aa、Td、Bf、Fn、Pi in the subgingivalplaque samples.2%Agarose gel electrophoresis was detectived.5. The groups of experimental animals were killed by air embolism after8weeks,andthe pathological changes of the periodontal tissues were observed by HE staining.6. Statistical analysisThe data were statistically analyzed using SPSS13.0software. Gingival index andplaque index of rank data used rank sum test，probing depth of measurement was expressedby X±s，groups of the comparison used analysis of variance.Significance level: P<0.05is considered statistically significance.RESULTS1. The weight of the rabbits in hypoxia perodontitis group is downtrend. After8weeks, swollen gums were red, texture were soft and there were periodontal pockets. There weresignificantly different in term of the sulcus bleeding index、dental plaque index andperiodontal pocket depth in hypoxia perodontitis group when compared with normaloxygen periodontitis group(P<0.05).HE staining showed that there were active osteoclasticbone resorption pits in alveolar bone, the destruction in alveolar crest and the intrinsicabsorption of alveolar bone in highland2. Putative periodontal pathogens,including Pg、Aa、Td、Bf、Fn、Pi can be detectedboth in hypoxia periodontitis group and normal oxygen periodontitis roup.Fn, Pi detectionrate were significantly different between the plateau experimental group the of and theplain(P<0.05).3. At a simulated altitude of5,000meters hypoxia environment in our model, theresults indicated that the relevance ratio of Fn in plateau experimental group is higher thanin normal oxygen periodontitis group(P<0.05), and the relevance ratio of Pi in normaloxygen periodontitis group is higher than in plateau experimental group(P<0.05).CONCLUSIONS1. The animal model of periodontitis in hypoxic conditions were successfullyestablished. The pathological changes of periodontal tissue showed typical pathologicalfeatures of active periodontitis, and inflammatory reponse were severe, progression ofinflammation were rapid.2. the plain experimental group compared to the plateau experimental group, the typesof putative periodontal pathogens has changed. High altitude hypoxic environment that mayaffect the colonization of some putative periodontal pathogens.3. High altitude hypoxic environment is main reason for periodontitis heavier, Fn wasrelated to plateau periodontitis disease severity.