الفهرس 
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Abstract
This work aimed to evaluate the structural and immunohistochemical alteration in the distribution of fibronectin(FN) (ECM component) in the alveolar bone, dentogingival junction (DGJ) and alveolar mucosa of albino rats’ molar area induced by ovariectomy (ovx). The possibility of prevention of these alterations, by administration of estrogen replacement therapy (ERT) was also investigated.
Sixty adult female albino rats weighing around 200 gms each were used in this study.
The animals were divided into 3 groups:-
• group I (Control): consisted of 20 rats subjected to a sham ovx surgery and subdivided into:
- Ten rats, killed after 8 weeks and serve as control group for group II (ovx) rats.
- Ten rats, killed after 9weeks and serve as control group for groupIII (ovx+ERT) rats .
• group II (ovx): consisted of 20 rats subjected to a bilateral ovariectomy surgery and killed after 8 weeks from the ovariectomy.
• group III (ovx+ERT): consisted of 20 rats subjected to a bilateral ovx surgery. After 8 days from the ovx procedure, the rats began to receive the hormone replacement therapy with a daily dose of 1.5gm/kg body wt daily of 17--estradiol (E2) by intraperitoneal injection. The animals were killed after 8 weeks from the beginning of ERT. At the end of the experimental period of each group, the rats were killed by cervical dislocation. The molar area of both the mandible and maxilla was excised, fixed, decalcified and processed for paraffin embedding. Five micrometer thick sections were sectioned for the subsequent histological and immunohistochemical staining procedures:-
- The histological examination was done by staining with H &E.
- The immunohistochemical staining was done using the primary antibody anti-human fibronectin (FN) and DAKO LSAB+ universal kit.
- Examination of sections was done using the light microscope.
• Histomorphometric study using the image analyzer was run to examine :
- The cortical thickness.
- The surface area percentage of spongy bone trabeculae.
- The number of osteocytes per unit area in the cortical bone.
- The number of megakaryocytes (MKs) per unit area in the bone marrow.
* H & E stained sections in both the mandibular and maxillary molar area after 8 weeks from ovx showed marked resorptive changes in the alveolar bone.
The socket wall was scalloped and irregular. Zucker Kandl and Hirshfeld canals showed widening.
The compact bone forming the buccal and lingual cortical plates showed widening of Haversian canals as well as widening of the marrow spaces.
The spongy bone which fills the area between the cortical plates and the alveolar bone proper showed thinning of the trabeculae and widening of the marrow spaces.
Most of the osteoblasts in the ovx rats alveolar bone were flattenend (inactive). Occasionally many active osteoblasts were entrapped in wide areas of their secretion of osteoid tissue in the area of spongy bone.
A proportion of osteocytes in the ovx rats appeared to be shrunken and showed chromatin condensation. There was a wide empty space in the lacunae around most of the osteocytes. Some lacunae contained remnants of osteocytes and few lacunae were empty.
In the ovx rats, osteoclasts showed an apparent increase in number .
There was an increase in the number of resting as well as reversal lines in ovx animals
The mandible and maxilla of ovx rats were different in their statistical results.
The mean thickness of the mandibular buccal and lingual cortical plates was significantly less (by about 50%) than the control group.
Meanwhile maxillary buccal and lingual cortical plates showed a highly significant decrease (by about 33%) compared with the control group.
The mean surface area percentage of both maxillary and mandibular spongy bone trabeculae was significantly less (by about 28%) than that of the control group.
The mean number of osteocytes per unit area in the mandibular cortical bone showed a highly significant decrease (by about 50%) compared with the control group.
On the contrary, the mean number of osteocytes in the maxillary cortical bone showed a non significant decrease (by about 20%) compared with the control group.
There was a non significant decrease in the number of megakaryocytes in the marrow of both the maxillary and mandibular alveolar bone compared with the control group.
Examination of sections from both the mandibular and maxillary molar area of ovx rats stained with indirect immunoperoxidase staining for fibronectin (FN) revealed the following results:-
- A decrease in the staining intensity of the periosteum covering the cortical bone.
- Overall decrease in the staining intensity of the endosteum lining the spongy bone trabeculae and the Haversian canals. Few areas in the endosteum showed the same staining intensity as that of the control group.
- Most of the osteoblasts were negatively stained.
- The ruffled border and the nearby cytoplasm of osteoclasts showed an increase in the staining intensity compared with the control group.
- The lamina limitans of osteocytes lacunae were negatively stained.
- Megakaryocytes in the bone marrow showed a variation in the staining intensity.
- The PDL showed a decrease in the staining intensity especially in the area of transseptal ligament.
Examination of H & E stained sections in both the mandibular and maxillary molar area of ovx+ERT rats showed few histological changes compared with the control group.
The osteoblasts lining most surfaces of the alveolar bone were apparantly increased in number and appeared to be active and secreting osteoid tissue.
Osteocytes were present in lacunae filled with homogenous pale stained material delimited by lamina limitans.
Osteoclasts showed an apparent decrease in number.
Both the resting and reversal lines showed some apparent increase in number.
The bone marrow showed hypercellularity.
In this group also, the mandible and maxilla showed different statistical results.
The mandibular cortical plates showed a non significant decrease in thickness compared with that of the control group.
Meanwhile the maxillary cortical plates showed a significant decrease (by about 20%) in thickness compared with that of the control group.
The surface area percentage of mandibular spongy bone trabeculae demonstrated a non significant decrease compared with the control group.
Meanwhile in the maxilla, the surface area percentage of spongy bone trabeculae was significantly less than that of the control group
(by about 18%).
The mean number of osteocytes per unit area in the mandibular cortical plates was significantly less (by about 27%) than that of the control group.
On the other hand, the mean number of osteocytes per unit area in the maxillary cortical plates showed a non significant decrease compared with that of the control group. This is in contrast with the other three statistical parameters in which the maxilla was more affected than the mandible.
In this group also, the megakaryocytes showed a non significant decrease in number in the marrow of both the maxillary and mandibular alveolar bone.
Examination of sections from both the mandibular and maxillary molar area of ovx+ERT rats stained with indirect immunoperoxidase staining for FN revealed the following results:
- Most areas in the bone matrix showed an increase in the staining intensity. Some area showed granular staining especially at the periphery.
- Most of the osteoblasts were intensely stained.
- Few osteocytes were positively stained.
- Most of the megakaryocytes were negatively stained.
- Most PDL areas were intensely stained.
* H&E stained sections in the DGJ of mandibular as well as maxillary molars of ovx rats demonstrated some decrease in the number of nuclei in the epithelium, mostly in the basal and parabasal layers. Some nuclei in the flattened cell layer showed karyolysis.
Examination of sections from DGJ of mandibular molars of the ovx rats stained with indirect immunoperoxidase staining for FN demonstrated:
- Intense staining in some epithelial cells mostly in the basal cells and in the ECM of epithelial cells. The cells showing positive reaction for FN were less than that present in the control group.
Examination of the DGJ of maxillary molar stained with indirect imunoperoxidase staining for FN showed a marked decrease in the staining intensity in the epithelial cells. Most of them were negatively stained.
* H&E stained sections in the DGJ of mandibular as well as maxillary molars of ovx+ERT rats demonstrated the presence of some extravasated RBCs in both the epithelium and the C.T.
Examination of sections in the DGJ of both the mandibular and maxillary molars in ovx+ERT rats stained with indirect immunoperoxidase staining for FN demonstrated:
- A diffuse faint staining in most areas of the epithelium. Some other areas were negatively stained.
* H & E stained sections in both the maxillary and mandibular alveolar mucosa of ovx rats showed elongation of the C.T papillae. The prickle and the granular cell layers showed lightly stained nuclei. Basophilic granules with different sizes, were seen in the granular cell layer and in the upper rows of the prickle cell layer.
Examination of the same tissue stained with indirect immunoperoxidase staining for FN demonstrated a decrease in the staining intensity compared with the control but with the same distribution pattern i.e. the granular cell layer showed the highest intensity of staining. The basal and parabasal cell layers were negatively stained.
* H & E stained sections in both the maxillary and mandibular alveolar mucosa of ovx+ERT rats showed an increase in the thickness of the keratin layer and a decrease in the number of nuclei in both the prickle and the granular cell layers. Some lightly stained nuclei were observed in both the prickle and the granular cell layers. Many basophilic granules with variable sizes appeared in the granular cell layer and in the upper rows of the prickle cell layer.
Examination of sections from both the maxillary and mandibular alveolar mucosa of ovx+ERT rats, stained with indirect immunoperoxidase staining for FN demonstrated:
- Faint staining in the keratin layer.
- Intense staining in the granular cell layer.
- Moderate staining in the intercellular spaces in the prickle and the basal cell layers.