A STUDY OF PERIODONTIUM DURING AND AFTER EXPERIMENTAL TRAUMATIC OCCLUSION IN RATS

rts of mastication system caused by abnormal occlusion or abnormal occlusion ftmnction is called traumatic occlusion Traumatic occlusion provides a trauma that affects the penodontium and the calcitonin gene-related peptide (CGRP)- immunoreactive nerve fibres in the penodontium~[1,2]. In recent years, Traumatic occlusion in the penodontium was focused by the clinician and some clinical imformation was obtained But there is little clinical information about the recover process after traumatic occlusion In the past pathological changes and CGRP- immunoreactive nerves in the periodontium were paid attention separately during experimental traumatic occlusion in animals~[1-3]. However, little attention was put in the recover process of periodontium and the change of CGRP- immunoreactive nerves after trauma, needless to say the relationship of those two aspects. As the moiphology and number of the CGRP- immunoreactive nerve fibres change during the traumatic occlusion~[2], whether the CGRP- immunoreactive nerve fibres take part in the impamnent and recovery process? In this expenment, we use the model of experimental traumatic occlusion and the immunochemist method to study the change of penodontium and the CGRP- lmmunoreactive nerve fibres dunng and after the traumatic occlusion, in order to cast some lights in the pathological process, pathogenesis and recover processPurpose:To study the changes in histopathology and nerves in the penodontium in trauma and the recover process of them after trauma by observing the changes of periodontium and nerves during and after experimental traumatic occlusion in ratsMatenal and methods sixty-six SD rats are separated as eight groups-5- one-day group (n~6), three-day group (n~6), seven days group (wz6), fifteendays group (n12), one month group (n~l2), three month group (n~12), fifteeii days after traumatic occlusion for one month group (n6) and one month after traumatic occlusion for one month group (n6) Comparison groups are bred together and each group for two rats The occlusion surface of the first maxillary molar is raised 0.3-0 8mm with a nail, then, traumatic occlusion is produced in the first molar of the mandible In the after traumatic occlusion groups, the nails are pull out in anaesthesia after operation for one month. The sections are treated with HE and mimunohistochemisUy methods Then, they are observed with the aid of an optical microscopeResults:1 A histologic examination of the penodontium The injury including the disarrangement of periodontal ligaments, bone resotpUon and vascular dilation is first observed in the 3-day group animals. Changes in the periodontal ligament are marked after one week of trauma. The heavy trauma is observed in the one-month group animals where hyalimzation, osteoclasts, the resorption of bone and cementum could be observed The resorption of dentin emerges in one section of the one-month group The trauma begins to decrease in the 3-month group compared with that it is in the one-month group. In the 3-month penod, the formation of bone and cementum is manifested. At the one-month after traumatic occlusion for one-month group, there is litter difference in penodontium compared with the control animals where vascular dilation and the formation of bone and cementum could be observed and the resorption of bone could still be observed in some sections There are differences among rats2 A mimunohistochemisiry examination of the penodontium Changes of CGRP- immunoreactive nerve fibres in morphology, distribution and density in penodontium are first observed in the 3-day animals During the one-month group, most of the penodontiums show nerve changes After the period, the changes begin to decrease There is little difference between the one-month after traumatic occlusion for one-month group and the control group, however, swelled nerve fibers are still observedConclusion:1 The pathological changes including the disarrangement of periodontal ligaments, vascular dilation and the resorption of bone and cementum in penodontium