Effects of bite force lost on the expression of iNOS mRNA in the rat periodontium
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Objective To establish iNOS for the study of molecular mechanism of the effect of bite force loss on periodontium remodeling. Methods Eighty-one male Wistar rats(weigh 250±20g)were chosed to establish rat models of different bite force for the study, and left maxillary molars of rats were extracted and left mandibular molar area was used as the model with bite force lost. The animals were sacrificed after 6 hours, 1,2,3 days and 1,2,3,4 weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of iNOSmRNA in PDLC and osteoblasts with HE staining and RT-PCR techniques. Results In the group of lost biting force, the derangement of periodontal ligament and resorption of alveolar bone were observed in histologic study: the structure of periodontal ligament deranged .fibers and cells arrayed disorderly, there were many holes in the alveolar bone, occasionally occurred osteoclasts; the expression of iNOSmRNA was observed dramatically changed: the expression of iNOSmRNA in periodontal ligament fibroblasts and osteoblasts was higher than normal, especially at 2d and 3w. Conclusion Bite force lost induce the expression of iNOSmRNA enhanced apparently in PDLC and osteoblasts, it suggestes that iNOS may play important roles in the process of periodontium remodeling.Keywords:
Periodontal fiber
Periodontium
Bite force quotient
Alveolar process
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The aim of this study was to observe the effect of decreased bite force on type I collagen mRNA in periodontal ligament (PDL) and probe into the molecular mechanism of the change in type I collagen mRNA.Animal models were established by extracting left maxillary molars of rats. In situ hybridization was applied.The results showed that under decreased bite force, the expression level of type I collagen mRNA decreased at the sixth hour (49.7 +/- 11.1) (P < 0.05), reached the nadir on the second day (23.7 +/- 8.6), began to get over on the third day (43.1 +/- 10.3), and reached a relatively high level at the second week(56.3 +/- 9.8), but it was still lower than that of the normal bite force group (91.4 +/- 16.0)(P < 0.05); the expression of type I collagen mRNA near the cementum was higher than that near the alveolar bone.These results indicate that the expression level of type I collagen mRNA is closely related to bite force.
Periodontal fiber
Type I collagen
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Objective To study the expression of TNF-α in the rat periodontal cells under normal and increased bite force,in order to explain the molecular mechanism of periodontium remodeling.Methods HE staining and immunohistochemistry techniques were applied to study the change in the histologic morphology and the expression of TNF-α protein.Results Under the increased bite force,periodontal ligament width was enlarged and alveolar bone was formed;the expression level of TNF-α increased apparently in periodontal cells.Conclusion Increased bite force induce the expression of TNF-α increased apparently in periodontium.It approached initially the molecular mechanism of periodontium remodeling,suggested that the histologic morphology is closely related to the mechanical condition.
Periodontium
Periodontal fiber
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Objective: To observe the expression change of inducible nitric oxide synthase(iNOS) in orthodontic periodontal tissue remodeling,learn the role of NO/iNOS during experimental tooth movement in rats.Methods: 56 male SD rats were randomly divided into 8 groups.Orthodontic appliance was placed between the maxillary right first molar and maxillary central incisors of rat.Immunohistochemistry and image analyses were performed at 0,1,3,5,7,14,21,28 days after orthodontic force application.Results: The expression of iNOS was weak immunoreactivities in normal periodotium.3 days after tooth movement,the immunoreactivities of iNOS were increased,and reached the maximum after 7days.Conclusion: NO/iNOS participate in orthodontic periodontal tissue remodeling during tooth movement.
Maxillary first molar
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In order to explain the molecular mechanism of periodontium remodeling the expression of IL-6 in the rat periodontal ligament fibroblasts (PDLC) and the alveolar bone osteoblasts under normal and bite force lost was studied.To establish a rat model of different bite force for the study, left maxillary molars of rats were extracted and the left mandibular molar area was used as the bite force lost. The animals were sacrificed after 6 hours, 1, 2, 3 days and 1, 2, 3, 4 weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of IL-6 protein in PDLC and osteoblasts with HE staining and immunohistochemistry techniques.In the group of bite force lost, the loosely arrangement of periodontal ligaments and the resorption of alveolar bone were observed in histological study, the expression of IL-6 in PDLC and osteoblasts was enhanced apparently than that in the group of normal bite force by using immunohistochemistry techniques. In the group of lost bite force, the expression of IL-6 in PDLC enhanced with time regularly: The expression of IL-6 was strengthened after 3 days, and reached the peak after 2 weeks, then, decreased after that and restored to normality in 4 weeks. While in osteoblasts of the group of bite force lost, the expression of IL-6 was strengthened just after 2 weeks.Bite force lost induce the expression of IL-6 enhanced apparently in PDLC and osteoblasts, it suggests that IL-6 may play important roles in the effect of bite force on periodontium remodeling. It approaches initially the molecular mechanism of periodontium remodeling, demonstrates that the histologic morphology is closely related to the mechanical condition.
Periodontal fiber
Periodontium
Bite force quotient
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This study aims to observe the expression of Sclerostin during movement of orthodontic teeth and determine the effect of this protein on remodeling of periodontal tissues.Twenty-four Wistar rats were chosen. Orthodontic forces were applied between the bilateral incisor and first molar to achieve mesial movement. Rats in each group were executed at different time points (0, 1, 3, 5, 7, 14 d). Morphology of periodontal tissue was observed by hematoxylin-eosin (HE) staining. The number of osteoclasts were observed by tartrate-resistant acid phosphatase (TRAP) staining. Sclerostin expression were observed by immunohistochemical staining.HE staining revealed that the resorption of alveolar bone intensified with prolonged movement. Results of immunohistochemical and TRAP staining revealed that Sclerostin expression and number of osteoclasts were related to duration of movement of orthodontic tooth. After staining for 5 days, the number of osteoclasts and Sclerostin expression reached their peak and then began to decline. The numbers of osteoclasts and the expression level of Sclerostin were higher at the compressive side than those at the tensive side.Sclerostin affected orthodontic tooth movement by inhibiting the Wnt signaling pathway and by indirectly or directly controlling bone morphogenetic protein.
Sclerostin
Periodontal fiber
Bone remodeling
Osteocyte
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Objective:To observe the change of matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1(TIMP-1) expression during experimental tooth movement in rats,and to learn about the relationship between MMP-3, TIMP-1 and orthodontic periodontal tissue remodeling.Methods:Orthodontic appliance was placed between the maxillary right first molar and maxillary central incisors of adult SD rat.Established rat molar movement model. Immunohistochemistry and image analyses were performed at 1?3?5?7?14 days after orthodontic force application.Results:The expression of MMP-3 and TIMP-1 were weak immunopostive in normal periodotium.At 1d after tooth movement, the immunoreactivities of MMP-3 were increased, at 5d , reached the maximum.Osteoclasts were also observed strong positive.The expression of TIMP-1 was increased at 3 days.At 7 days,a marked increase in TIMP-1-positive firblasts and osteoblasts was found not only on the pressure side but also on the tension side of the periodontium.Conclusions:MMP-3 and TIMP-1 participate in orthodontic periodontal tissue remodeling during tooth movement. MMP-3 may play an important role in osteoclastic bone resorption.
Periodontium
Bone remodeling
Bone matrix
Matrix (chemical analysis)
Periodontal fiber
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We carried out an experiment to induce traumatic occlusion in mice periodontal tissue and analyzed the expression of HSP47.Continuous traumatic occlusion resulted to damage and remodeling of periodontal ligament as well as increase in osteoclasts and bone resorption.Four days after traumatic occlusion, osteoclasts did not increase but Howship's lacunae became enlarged.That is, the persistent occlusal overload can destroy collagen fibers in the periodontal ligament.This was evident by the increased in HSP47 expression with the occlusal overload.HSP47 is maintained in fibroblasts for repair of damaged collagen fibers.On the other hand, osteoclasts continue to increase although the load was released.The osteoclasts that appeared on the alveolar bone surface were likely due to sustained activity.The increase in osteoclasts was estimated to occur after load application at day 4. HSP47 continued to increase until day 6 in experiment 2 but then reduced at day 10.Therefore, HSP47 appears after a period of certain activities to repair damaged collagen fibers, and the activity was returned to a state of equilibrium at day 30 with significantly diminished expression.Thus, the results suggest that HSP47 is actively involved in homeostasis of periodontal tissue subjected to occlusal overload.
Periodontal fiber
Periodontium
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The purpose of this research is to study the expression change of IL-1 beta induced by forces in the periodontium of osteoporosis rats.Eighteen SD rats were randomly divided into three groups: the normal controlled, the normal orthodontically controlled and the experimental group of osteoporosis. Six weeks after ovariectomy, the first molars were moved mesially by 50 g force created from elastic-thread for one week in the force loading groups. Then the rats were killed, and the 5 microns-thick mesiodistal sections of maxillary teeth, including the roots and periodontium were made. IL-1 beta were localized immunohistochemically in periodontium, and semiquantitative analysis of cellular-staining intensity was done by microphotometry.The IL-1 beta of periodontal ligament cells without loading force were mildly stained in the controlled group, but the staining intensity increased significantly in the periodontium of orthodontically moved teeth, and it showed more strengthened staining in the periodontium of force-loading teeth in osteoporosis rats.The results demonstrate that periodontal ligament cells respond to mechanical force by increased production of IL-1 beta, and this can be enhanced by osteoporosis. IL-1 beta is an important cytokine in the process of orthodontically periodontal remodeling.
Periodontium
Periodontal fiber
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Objective To study the influence of occlusal force change on apoptosis of periodontal ligament fibroblast (PDLF) and expression of Bcl-2 and Bax in the fibroblasts.Methods Animal model of occlusal force change was established by extracting the right first, second and third maxillary molars in male SD rats. The rats were sacrificed at 6,12 hours and 1, 2, 3, 5, 7, 14, and 28 days after extracting the teeth(n=6), and right mandibular tissues were harvested. Morphologic changes were examined by HE staining and transmission electron microscopy (TEM), apoptosis and its related gene Bcl-2 and Bax expression in PDLF were detected by immunohistochemistry. The rats of normal occlusal forces were used as the control (n=6). The results were assigned a mean score based on the percentage and the intensity of cell positively stained for Bcl-2 and Bax.Results Animal model of occlusal force change was successfully established. HE staining showed that the experiment group had more loose periodontal ligament, disorderly fibres and cells, and uneven alveolar bone than those of the control group. TEM showed that pycnosis and intranuclear chromatin decomposed and coacervated around the edge of nucleus in PDLF. Immunohistochemical staining showed that expression of Bax reached its peak at 12h after extracting the teeth(216.83±6.34), meanwhile, the Bcl-2 expression peaked on day 3 after extraction(219.33±10.25)and then gradually decreased to normal level (7.00±2.37,5.67±2.16,P0.01).Conclusion Apoptosis and its related gene Bcl-2 and Bax participate in periodontal ligament remodeling after extracting the teeth.
Periodontal fiber
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Expression of insulin-like growth factor-Iin periodontium during experimental tooth movement in rats
Objective: To observe the change of insulin-like growth factor-Ⅰ(IGF-Ⅰ) expression during the experimental tooth movement in rats,and investigate the relationship between IGF-1 and orthodontic periodontal tissue remodeling. Methods: Orthodontic appliance was placed between maxillary first molar and maxillary central incisor of adult Wistar rats.Immunohistochemistry was performed at 0,3,7,14,21,28 days. Results: The IGF-Ⅰ expression was increased at 3 day,and markedly increased at 7 and 14 days.Conclusion: IGF-Ⅰ participates in the orthodontic periodontal tissue remodeling during tooth movement.
Periodontium
Periodontal fiber
Tooth mobility
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