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The transcriptional factor nuclear factor κB(NF-κB)regulates the expression of a wide variety of genes that are involved in immune and inflammatory responses, proliferation, and tumorigenesis. NF-κB consists of five members, such as p65(RelA), RelB, c-Rel, p50/p105(NF-κB1), and p52/p100(NF-κB2). There are two distinct NF-κB activation pathways, termed the classical and alternative NF-κB signaling pathways. Since mice lacking both p50 and p52 subunits developed typical osteopetrosis, due to total lack of osteoclasts, NF-κB is also important osteoclast differentiation. A selective NF-κB inhibitor blocked receptor activator of NF-κB ligand(RANKL)-induced osteoclastogenesis both in vitro and in vivo. Recent findings have shown that inactivation of NF-κB enhances osteoblast differentiation in vitro and bone formation in vivo. NF-κB is constitutively activated in many cancers including oral squamous cell carcinoma(OSCC), and is involved in the invasive characteristics of OSCC. A selective NF-κB inhibitor also prevented jaw bone destruction by OSCC by reduced osteoclast numbers in animal model. Thus the inhibition of NF-κB might useful for the treatment of bone diseases, such as arthritis, osteoporosis, periodontitis, and bone invasion by OSCC by inhibiting bone resorption and by stimulating bone formation.

The jaw bone is put in a special environmental condition because it receives not only external force through a masticatory muscle, but occlusal force directly from the teeth. Therefore, the morphology and internal structure of the jaw bone is strongly reflected by the erupted condition of the teeth. In the edentulous jaw bone, the number and thickness of the trabecular bones is reduced as well as decrease of its size. This tendency is quite resemble to the morphological change of osteoporosis. Based on the facts mentioned above, it is suggested that the loss of the teeth induces the fragility of the jaw bone. Therefore, maintenance of a healthy tooth is very important to keep the normal morphology of the jaw bone.

Unlabelled: Normal saline solution flushing of the inner mandible was done on twelve dogs, to confirm the effect of hemorrhagic infiltration that occurs in the fatty marrow. Histological examinations were performed at 1 hour, 5 days, 10 days, 2 weeks, 1 month and 3 months., Results: 1. Marrow extrusion occurred at approximately 1 atm (injection pressure). 2. At 1 hour, marrow cavities located between the 2 injection holes with the exception of the extraction sites were filled with infiltrated blood cells. Fatty marrow was moderately replaced by the infiltrated blood cells in the extraction cavities and outer distal areas of the injection holes. 3. A sequence of histogenetic events occurred. The area of bone formation gradually expanded in the fibrous tissue area. 4. Expansion of the bone formation area was almost completed at 2 weeks. Most of the original marrow was transformed into thin trabeculae-forming areas, and hematopoiesis and sinusoidal capillaries formed in the new marrow. These conditions at 2 weeks were similarly maintained at 1 month. 5. At 3 months, the number of trabeculae, sinusoidal capillaries and hematopoietic area decreased, with the increase of adipose cells. 6. These results indicate that the area of fatty marrow where the hemorrhagic infiltration occurred was transformed into the bone formation area, and the marrow activates particularly high between the period of 2 weeks and 1 month.

Unlabelled: The purpose of this study was to investigate the possibility of applying the hydroxyapatite dental implant to the jaw-bone with atrophic structure. The lower P3, P4 and the mesial root of M1 of 6 mongrel dogs were extracted. At 4 months, the trabeculae were taken out and porous hydroxyapatite granules were filled in the vacant spongiosa. At 8 months, hydroxyapatite dental implants were placed into this area. After 1 week and after 2 months, specimens were taken out and fixed by 10% formalin alcohol. They were embedded in polyester resin and undecalcified thin sections were prepared. The sections were stained with toluidine blue and observed under light microscopy., Results: 1) A larger amount of bone compared with that of the peripheral spongiosa was observed among the granules. 2) One week after implantation, differentiation around the implant was rather slow in the area of the granules. But in the area of the granules next to the spongiosa, differentiation was normal. 3) Two months after implantation, a new bone was observed, which filled the implantation space and united the implant to the bone among the granules. But on some implant surface, a fibrous connective tissue was seen. These results suggest that this method is able to improve the jaw-bone structure sufficiently to apply the hydroxyapatite dental implant.