A Study Of Pulp During Traumatic Occlusion And After Removal In Molar Of Rats

Traumatic occlusion may cause the lesion of periodontium, the hard structures of the teeth, the pulp, the temporomandibular joints, and the neuromuscular system. While there were many clinical reports concerning the pulpitis caused by traumatic occlusion, there had been surprisingly few studies of the response of pulpal tissues under these conditions. While there had been many experiments of traumatic occlusion which mainly observed the pathologic changes of molar pulp by traumatic occlusion, there was no literature concerning the pathologic changes of molar pulp after removal of traumatic occlusion. In this study, we observed the changes of pathology and CGRP-immunoreactive nerve fibres in rat molar pulp during traumatic occlusion and after removal by histopathology and immunohistochemistry. The results provide experimental evidences for etiological factor, pathology and pathogenesis of pulpitis caused by traumatic occlusion.This study was composed of two parts:Part I A histologic study of pulp during traumatic occlusion and after removal in molar of ratsObjective:To study the effect of traumatic occlusion on the cell, blood vessel and connective tissue in rat molar pulp and observe the recovery of pulp after removal of traumatic occlusion. Method: Sixty six male rats of the SD strain were utilized in experimental group. The occlusion surface of the upper right first molar is raised 0. 3-0. 8mm with a pin. Experimental animals were sacrified after experiment at various intervals traumatic occlusion-one day(6),three days (6), seven days (6), fifteen days (12),one month(12), three months (12) and after removal of traumatic occlusion- fifteen days(6), one rnonth(6). The lower right first molars were examined histologically, the lower right first molar of twenty six normal male rats were used as control. The method of removal of traumatic occlusion was to pull out the pin. The molar pulp of rats during traumatic occlusion and after removal of traumatic occlusion at different intervals was observed by histological examination respectively. Results: (1)Traumatic occlusion group. Disturbance of the odontoblastic layer(7-day, 15-day, 1-month), hyperemia (15-day, 1-month), vacuolizat ion (3-month) and decrease of cell number of unit area(1-month,3- month) were observed in pulp. Pulp necrosis was only found in one molar (3-month) (2)Removal of traumatic occlusion group: The pin was removed during 1-month traumatic occlusion. Disturbance of the odontoblastic layer was seen in one molar pulp during 1-month traumatic occlusion 15-day removal or 1- month traumatic occlusion 1-month removal respectively. The cell number of unit area informer groupwas less than in control group, however, the cell number of unit area in latter group was no less than in control group Conclusion: The pathologic changes of cell, blood vessel and connective tissue in pulpweIe caused by traumatic occlusion and cel l, b1ood vesselrecovered gradually after removal of the pin. Therefore, Weshould remove traumat ic occ1us ion as soon as early, Which i svery important for us to prevent and cure the pulpit is causedby trauma t 1c occ lus 1on.Part ll A study of CGRPiareoreactive nerve fibers of ratmo1ar pulp during traumat ic occlus ion and after removal0bjective: To study the effect of traumat ic occlus ion onCGRP--lfnmunoreact1ve (CGRP--IR) nerve fibres in rat molar pulpand observe the recovery of CGRPIR nerve fibres after removalof traumat ic occ1us 1on. Method: The same animals were used inPart 0ne and changes of CGRP--IR nerve fibres in pulp wereobserved dur 1ng traumat ic occlus ion and after remova1lfnmunohi stochemica l ly. Results: (1)Traumat 1c occlus 1on group:The 1ncrease of number, dens 1ty and morphology of CGRP--IR nerveflbres were found in rat mo1ar pulp. The changes of CGRP--IR nervefibres were clea11y during the period of 1conth. (2)Remova1of traumatic occlusion group: CGRP--IR nerve fibres in pulprecovered to normal gradua11y. Conc1usion: The changes ofCGRP--IR nerve f1...