| Stress is the condition that results when person–environment transactionslead the individual to perceive a discrepancy between the environmentaldemands and the person resources. With the quickening pace of modern sociallife and increasing pressures of competition, scholars at home and abroad arepaying more and more the attention on the role of psychological factors indisease development. A large number of studies have shown that psychologicalstress is a risk factor for a variety of systemic diseases and long-termwithstanding the psychological stress would cause adverse health effects. In oraldiseases, periodontitis has always been the hot point of research because of itscomplex etiology and multiple affecting factors. Periodontitis was defined as aninflammation of periodontal supporting tissue caused by special pathogenicmicroorganism, resulting in the advanced destruction of the periodontal ligament and alveolar bone, leading to the formation of gingival recession andperiodontal pocket. Periodontitis is one of the oral infectious diseases with thehighest incidence and the leading cause of adult tooth loss. Although thebacteria and plaque are the initiating factor of periodontitis, a simple bacterialinfection is not sufficient to explain the phenomenon that diverse severity ofperiodontitis usually accur in different individuals. The host’s own immuneresponse is an important factor for the development of periodontitis andperiodontal tissue damage. Some relevant epidemiological studies have shownthat stress, as an adverse factor for health, can affect the body’s immuneresponse and play an important role in the development of periodontitis.However, in the maintenance and healing process after the basic treatment ofperiodontitis, it is still not clear whether stress will also play a role, how theexpression of the related factors will change in the process of periodontal tissuehealing and repair, and whether psychological stress can affect the expression ofrelated factors. Therefore, our experiment is to study the effect of psychologicalstress on the healing process of periodontitis and the expression of bFGF inperiodontal tissue through the establishment of experimental periodontitis modeland psychological stress model in rats. We were aiming to further explore therelationship between psychological stress and periodontal disease, and provideexperimental evidence and theoretical basis for the research of psychologicalfactors-related-periodontitis and its intervention methods.The study was divided into three parts. The first part was the establishmentand evaluation of the experimental periodontitis and psychological stress modelin rats. Thirty-two out of a hundred and twenty-eight male SD rats wererandomly selected as control group (A) and the remaining96were operated byplacing a silk ligature around cervixs of the right second maxillary molar toinduce experimental periodontitis. The ligture were retained for four weeks to increase biofilm accumulation. The periodontitis model was verified by sulcusbleeding index and probing depth. Then the ligature were removed and the96rats were randomly divided into periodontitis control group (B), periodontitis+psychological stress group (C), periodontitis+psychological stress+stressagainst drug group (D), total4group with the normal control group (A).Psychological stress was given to group C and D, fluoxetine wasintraperitoneally injected to rats in group D5mg/Kg daily. Rats in each groupwere reared under the same conditions.The animals were sacrificed at initialtime point, week1,2, and4. At each time point the body weight gain, behaviortests and serum tests were used to testify stressed condition. The results showedthat after ligature placement, there was a significantly increase of periodontalprobing depth and gingival bleeding index and obvious periodontal tissuedamage was seen in histological detection. The rats in stress group showed aseries of changes including less body weight gain, affective-like behavioralchanges with a declined central and total distance moved in open field text andless time in and less entries into open arm in elevated plus maze, andtime-dependently increased serum CORT and ACTH. At the same time,anti-stress drugs could mitigate such adverse effects.After the establishment of effective animal models, we conducted thesecond experiment about the impact of psychological stress on periodontitishealing process by histological observation. The results showed that there was agood recovery of the damaged periodontal tissue in periodontitis control groupwhile psychological stress delayed the healing of periodontal tissue in stressgroup including decreased elimination of inflammation, slower alveolar bonerepair and reduced ability of junctional epithelium reattachment. At the sametime, anti-stress drugs can effectively antagonize the negative effects of stresson periodontal healing. In the third part of the experiment, we use the immunohistochemicalstaining to detect the expression of bFGF in the periodontal tissues. The resultsshow that there was a moderate number and staining intensity ofbFGF-immunoreactive cells at each time point in normal control group. Ligationsignificantly decreased the number of bFGF-immunoreactive cells and stainingintensity. After ligture removal, there was a significantly rebound inperiodontitis control group and slowing of recovery in stress group of thenumber and staining intensityof bFGF-immunoreactive cells. At the same time,the expression of bFGF in the drug group was stronger than that in stress group.Conclusions:1. Experimental periodontitis model can be effectively established in rats byligature placement, and chronic unpredictable mild stress can result inpsychologically stressed condition and cause a series of biological changes in rats.2. Psychological stress can affect the healing process of periodontal tissue,slowing down the elimination of the inflammation, reducing bone tissue repairand reconstruction.3. Psychological stress can reduce the expression of bFGF of periodontaltissue in periodontal healing process, suggesting that this may be one of themechanisms that psychological stress can delay periodontal healing.4. Anti-stress drug fluoxetine can effectively antagonize the adverse effectsof psychological stress and protecting the body from damage caused bypsychological stress. |
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