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Rat Molars (rat + molar)
Selected AbstractsExpression of c-Fos protein in the trigeminal nuclear complex resulting from quantified force application to the rat molarJOURNAL OF ORAL REHABILITATION, Issue 11 2003M. Watanabe summary, This study was conducted to investigate the expression and distribution of c-Fos-like immunoreactive neurones (Fos-neurones), in the rat trigeminal sensory nuclear complex, produced by mechanical forces with various magnitudes and durations applied to the left upper first molar. The magnitudes of forces applied to the tooth were 25, 50 and 100 g and the duration was 2 h. A quantified force of 100 g was also applied to the upper molar for varying durations [short-time (1,2 min)], 2, 4, 8 and 12 h. Fos-neurones distributed in the bilateral superficial laminae of the subnucleus caudalis, and the ipsilateral dorsomedial part of subnucleus oralis (Sp5Odm). The number of Fos-neurones increased in the subnucleus caudalis (Sp5C) according to the force magnitude. In the Sp5C, the number of Fos-neurones exhibited maximum level, 2 or 4 h after the application. In the Sp5Odm, however, the number of Fos-neurones reached the maximum level at 8 h. These data suggest that the change in the number of nociceptive neurones in Sp5C reflect changes in encoding the magnitude of force to tooth, and that the nature of pain response to orthodontic forces might have some relation to the delayed expression of c-Fos protein in the Sp5Odm. [source] Effects and distribution of the enamel matrix derivative EmdogainŽ in the periodontal tissues of rat molars transplanted to the abdominal wallDENTAL TRAUMATOLOGY, Issue 1 2002Yoshioki Hamamoto Abstract , The enamel matrix derivative EmdogainŽ (EMD) has been found to promote regeneration of lost periodontal tissues. We have studied the effects and distribution of EMD in the periodontal tissues of maxillary rat molars transplanted to a subcutaneous position in the abdominal wall. The molars were transplanted with or without EMD either immediately after extraction or after drying for 30 min. After 2 days, 1, 2 or 4 weeks the rats were killed and the teeth were examined by means of light microscopy and immunohistochemistry with anti-amelogenin antibodies. Teeth transplanted immediately after extraction showed formation of alveolar bone separated from the dental roots by a periodontal space, regardless of the use of EMD. Among the teeth that were transplanted with EMD after drying for 30 min, new alveolar bone was formed in five out of eight teeth after 2 and 4 weeks. None of the teeth that were dried for 30 min and transplanted without EMD showed alveolar bone formation. Only one tooth transplanted with EMD showed root resorption after drying, while resorption was noted in all teeth transplanted without EMD. All teeth that were transplanted with EMD and none of the teeth that were transplanted without EMD showed an immunohistochemical reaction for amelogenin. After 2 days, amelogenin was precipitated on all surfaces exposed at the transplantation procedure. Later, the immunoreactive material was redistributed to cells at the root surface, where it was still demonstrable after 4 weeks. In conclusion, EMD is accumulated in cells at the root surface and promotes regeneration of the periodontal tissues of the transplanted teeth. It also seems to promote healing of root resorption. [source] Hypothermic insult to the periodontium: a model for the study of aseptic tooth resorptionDENTAL TRAUMATOLOGY, Issue 1 2000C. W. Dreyer Abstract , The aim of the current investigation was to define an animal model for the study of hard tissue resorption by examining the responses of the periodontal ligament (PDL) to both single and multiple episodes of hypothermic injury to the crowns of rat teeth. A group of 12 male rats weighing 200,250 g were anesthetized, and pellets of dry ice (CO2) were applied once to the crowns of the right first maxillary molars for continuous periods of 10 or 20 min. Animals were sacrificed at 2, 7, 14 and 28 days and tissues were processed for routine histological examination. A second group of eight animals and a third group of 12 animals were subjected to three applications of dry ice over a period of 1 week and sacrificed at 2 and 14 days respectively after the final application. In addition to thermal insult, the periodontium of teeth from a fourth group of six rats was subjected to mechanical trauma. Examination of the sections from the group undergoing a single freezing episode revealed that, by 1 week, shallow resorption lacunae had appeared on the root surface. These became more extensive after 14 days. At the same time hyaline degeneration was evident in the PDL. Within this group, teeth subjected to the longer 20-min application times generally showed more extensive injuries. By 28 days, evidence of repair was observed with reparative cementum beginning to line the resorption lacunae in the root dentin. Sections from animals subjected to multiple episodes of thermal trauma and those subjected to additional mechanical insult showed more extensive external root resorption than those from single-injury animals. It was concluded that low temperature stimuli applied to the crowns of rat molars were capable of eliciting a sterile degenerative response in the PDL which, in turn, resulted in external root resorption. Furthermore, the degree of this tissue injury was commensurate with the duration and number of exposures to the trauma. The results also indicated that progression of the resorptive process required periodic exposure to the injury, in the absence of which repair to the damaged root occurred. [source] Bone response to different strength orthodontic forces in animals with periodontitisJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2005J. A. Garat Background:, Occlusal alterations resulting from tooth movements caused by periodontitis-related bone loss are often corrected with orthodontic treatments. Although the outcome is usually satisfactory, a quantitative histomorphometric study of bone response would contribute to improving treatment planning and optimizing results. Methods and Results:, This study is a histomorphometric analysis of alveolar bone response to 51 and 75-g orthodontic forces applied to rat molars subjected to experimental periodontitis by placing a ligature around the neck of the molar during 48 h. The orthodontic device consisted of two bands with a tube welded to their palatine aspect, through which the arms of a helicoidal spring were threaded so as to exert force toward palatine. The device was placed immediately and 48 h after removing the ligatures. When applied 48 h post-removal of the ligature, both orthodontic forces caused an increase in bone volume in the periodontitis group. Conclusions:, Our study shows that application of orthodontic forces once periodontal infection has been controlled contributes to increasing alveolar bone volume, consequently improving bone quality. [source] Dental root resorption and repair: histology and histometry during physiological drift of rat molarsJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2003Ryusei Kimura Objective:, The process of dental root resorption and subsequent cementum regeneration has not been sufficiently elucidated. This study aimed to examine the process of the root resorption and cementum regeneration during physiological tooth drift using a rat model, and to evaluate this experimental model. Methods:, Distal roots in mandibular first molars and the surrounding periodontal tissues were investigated with light and electron microscopy. The light microscopic approach included histochemical and histometric analyses utilizing the tartrate-resistant acid phosphatase (TRAP) reaction. Results:, Root resorption was observed in the distal side of the roots and was most active in 5- to 6-week-old rats, and gradually decreased hereafter. An increase in the number of TRAP-positive mononuclear cells, which seemed to be odontoclast precursor cells, preceded the increase in the number of odontoclasts. Root resorption was transient, and was followed by the new formation of acellular extrinsic fiber cementum accompanied with only a slight inflammation, and therefore classified as external surface resorption. Preparation for new cementum started adjacent to the resorption areas when root resorption was most active. Conclusions:, The root resorption during drift in rats is transient and followed by acellular extrinsic fiber cementum regeneration. Cellular kinetics suggested that odontoclast precursor cells are supplied as mononuclear cells from vascular spaces. [source] Different distribution of immunocompetent cells in the dentogingival junction during root formation in rat molarsJOURNAL OF PERIODONTAL RESEARCH, Issue 1 2003Hiroshi Tamura The distribution of immunocompetent cells in the dentogingival junction of rat molars during root formation was investigated by immunocytochemistry using antibodies to class II major histocompatibility complex (MHC) molecules (OX6-antibody) and monocyte/macrophage lineage cells (ED1-antibody) as well as by histochemical reaction for periodic acid,Schiff (PAS). Two portions (the junctional epithelium in the mesial gingiva of the first molar, and the interdental gingiva between the first and second molars) were selected for observations. At the eruption stage of the first molar (16,18 days after birth), OX6-positive cells, dendritic or oval in shape, were abundantly distributed in the connective tissue between the oral epithelium and tooth germ. Positive cells with slender cell processes were also found beneath the ameloblast layer. At the commencement stage of the first molar occlusion (24,28 days after birth), numerous OX6-positive cells displaying a dendritic fashion existed preferentially in the mesial gingiva, but were fewer in the interdental gingiva. In contrast, the interdental gingiva showed a denser distribution of ED1-positive cells and PAS-reactive polymorphonuclear leukocytes (PMLs) than the mesial gingiva. At the completion stage of root formation (100,120 days after birth), the OX6-immunopositive cells invaded the deeper position of the mesial gingiva with the downgrowth of the epithelium; they had a considerably higher cell density compared with those in the interdental gingiva where PAS-reactive PMLs persisted. These findings indicated that the immunocompetent cells showed a region-specific distribution and cell density by their roles in immune response. [source] | ||||||||||