| Objective:To study electroencephalogram (EEG) changes, Pathological changes of periodontal tissues and the expression changes of bone morphogenetic protein-2(BMP-2) mRNA in spinal trigeminal nucleus caudalis (Vc) in occlusal trauma rats. To explore effects of occlusal trauma on brain electrical activity and the relationship between periodontium injury and the expression of BMP-2in Vc in occlusal trauma rats. To provide a new thinking for the study of repair mechanism of periodontium and periodontal nerve of central nervous system in occlusal trauma rats.Methods:Seventy eight-week wistar healthy male rats(weight:225-260g, supplied by Experimental Animal Center of Shandong University) were used. Animals were assigned to five experimental groups and five control groups randomly, seven per group. Occlusal surface of the right first molar in the experimental groups (1-day,3-day,7-day,14-day,28-day occlusal trauma group) was raised0.5mm by bonding stainless steel square wire with super-bond. We did the same operation in control groups, with no bonding the wire. The animal was anesthetized with10%chloral hydrate at the specified time, unipolar leads were used to record the left and the right hippocampus sleep EEG of the rat with BL-420F Bio-functional experiment system, rats was executed for the specified tissue, HE staining method was used to examine the damage level of periodontal tissues and the QPCR was used to examine the expression of BMP-2mRNA in Vc. Results:1. EEG changes in in hippocampus in occlusal trauma rats1.1Changes of brainwave index8wave index displayed as the increasing-decreasing-returning to normal trend from1d to28d,δ wave index met its minimum on the7th day, changes in7d\14d group were statistically compared to control group (p<0.05).θ wave index hit its peak on the14th day (p<0.05), decreased on the28th day (p<0.05). a wave index changed not statistically. β wave index decreased on the1st day, increased on the7th\14th day (p<0.05).2. Changes of frequency and amplitude1.2.1Frequency reduced obviously on the1st day (p<0.05) and increased gradually from1d to7d, the data hit its peak at the7th day (p<0.05) and decreased back to normal gradually from the14th day to the28th day.1.2.2Amplitude significantly reduced on the1st day and increased on the3rd day compared to control group (p<0.05).2. Pathological changes of periodontal tissues and the expression changes of BMP-2mRNA in Vc in occlusal trauma rats2.1Pathological changes of periodontal tissues in occlusal trauma rats2.1.1X-ray:Changes were not significant in ld\3d group; there was some absorption in apical alveolar bone and continuity of bone plate reduced, the absorption significantly increased in apical alveolar bone in14d and still exist in28d; low density shadow can be seen in furcation in28d.2.1.2HE staining:The apical periodontal membrane loose and edema. Periodontal space increased in1d\3d group, the space decrease, cementum and alveolar bone resorption can be found in7d\14d group. New alveolar bone and continuity of bone plate can be seen in28d group.2.2Changes of BMP-2mRNA in Vc in occlusal trauma rats The expression of BMP-2mRNA dcreased at1d group, increased at3d\7d\14d group and dcreased at28-day group, the expression hit a peak at14th day (p<0.05). Conclusion:1. Occlusal trauma affected the function of central nervous system. Results revealed that occlusal trauma changed hippocampal CA3EEG in sleep state, and mainly affected the deep sleep, reduced sleep quality.2. The expression of BMP-2mRNA changed regularly in occlusal trauma rats, and the changes of BMP-2mRNA was consistent with the damage level of periodontal tissues. We speculated that occlusal trauma activated astrocytes first and astrocytes released BMP-2to regulate neuronal activity and to repair periodontium and periodontal nerve injury. The result can provide new idea for repair mechanism of periodontium and periodontal nerve of central nervous system in occlusal trauma rats. |
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