JSJD

JOS

Japanese Academy of Sports Dentistry

The Stomatological Society, Japan

TOS

JSJD

Japanese Academy of Sports Dentistry

The elucidation of Bone Remodeling Change of EPH/ephrin signal with the Aging, 2008 - 2010

Summary： The changes in periodontal tissue with growth and aging were analyzed. The expression of CGRP-ir nerve fibers in the PDL is most active in the growth period and decreases gradually with aging. Moreover, age-related decreases in the expression of bFGF may delay the regeneration of the periodontal ligament. Such an effect may act unfavorably in the case of tooth movement.

Regulation of cytokine growth factor inhibits anakylosis and root resorption in transplanted teeth, 2005 - 2006

Summary： While many studies reported the structural changes in the periodontal ligament (PDL) under hypofunctional conditions, the associations of cytokine growth factors are still unclear. They are known to take part in inflammation, and may affect the biological properties of hypofunctional tooth. To investigate the hypofunctional PDL and the recovery from this condition, we focused on interleukin-1 beta (IL-1) and basic fibroblast growth factor (FGF-2). The lack of occlusal stimuli caused atrophic changes in the PDL with the upregulation of IL-1 and decreased expression of FGF-2, while decreased IL-1 and enhanced FGF-2 expression were observed in the recovery process. These results suggest that occlusal stimuli regulate IL-1 and FGF-2 expression, and the nature of this regulation may differ from that in the healing process of an inflammatory reaction.
Our study also revealed that the occlusal stimuli promote the proliferation and differentiation of PDL cells with enhanced nitric oxide (NO) synthesis, while the lack of occlusal stimuli reduced the NO synthesis and induced atrophic changes in PDL which resulted in the dentoalveolar ankylosis.
Those results clarified that the mechanical stimulus, such as occlusal force, is an important factor for the regeneration of PDL, which could be regulated by NO and cytokine growth factors.

Studies on the biological responses to mechanical stress on jaw bone and periodontium, and their clinical applications., 2005 - 2006

Summary： In order to investigate the biological responses to mechanical stress on jaw bone and periodontium, we aimed to apply the orthodontic force to the teeth in order to enlarge the space of periodontal ligaments (PDL), which may ease extraction and minimize the damage of PDL before transplantation. The orthodontic force was applied to the right upper molars for the experimental group, and after 7days, upper second molars were replanted or extracted, where replanted animals were then sacrificed after 14 days and those extracted teeth were examined for the attached PDL and exposed root surface. The application of orthodontic force for 7 days increased the PDL space and also the width of the alveolar socket, which resulted in the rich attached PDL to the root surface of the extracted teeth. And enhanced root resorption that may have been coincided with the disruption of the PDL was detected in the root of the control group without pre-application of orthodontic force at the 14 days after replantation. These results suggested that the pre-application of orthodontic force to the donor teeth increased the PDL width and ease the extraction, which may inhibit the root resorption after replantation. The influences of occlusal loading on the alveolar bone remodeling and the distribution of vasoactive intestinal peptide (VIP)- and calcitonin generelated peptide (CGRP)-immunoreactive (IR) fibers were investigated after tooth replantation in rats. At day 5, occlusal loading induced a significant increase in osteoclast number and osteoblast surface compared to those in the non-occluded group. VIP-IR fibers were observed beside osteoblastic layers and their distribution was significantly enhanced at day 5 in the occluded group, compared to the non-occluded group. Although there was immunoreactivity for CGRP in the periodontal ligament and alveolar bone apically, CGRP-IR fibers were not detected above the furcation. These results suggest that, after tooth replantation in rats, occlusal loading induced an increase in osteoclast and osteoblast formation, and that VIP might play a functional role in osteoblasts.

Regeneration of bone and periodontium using thermodynamics and mechanical stress, 2004 - 2005

Summary： In order to clarify the regenerative response of bone and periodontium against mechanical stress, molecular biological and histological examinations were performed. Mechanical tensional stress of low magnitude induced the increase of both type I collagen and decorin mRNA expression without changing ALP activity in periodontal ligament cells. Mechanical tensional stress of high magnitude induced the increase of type I collagen and decorin mRNA expression while decreasing ALP activity. mRNA level of Cbfa1/Runx2 increased at lower magnitudes of strain (0.8% and 5% elongation) but decreased at higher magnitude of strain (15% elongation). At 24 and 48 h, Cbfa1/Runx2 and osteocalcin mRNAs decreased at 5%, 10%, and 15% elongation, whereas cell proliferation and expression of type I collagen mRNA increased at the same elongation.
the replanted teeth were given a one-week healing period and then occlusion recovery was assessed, which resulted in decreased ankylosis and root resorption. The proliferative activity of PDL cells in the occluded group was generally higher than in the nonoccluded group. The activity of PDL cells in the recovery group was also higher than that of the nonoccluded group. the replanted teeth were given a one-week healing period and then occlusion recovery was assessed, which resulted in decreased ankylosis and root resorption. The proliferative activity of PDL cells in the occluded group was generally higher than in the nonoccluded group. The activity of PDL cells in the recovery group was also higher than that of the nonoccluded group.
In the hypofunctional condition of occlusal stimuli, marrow spaces had widened and elongated vertically : the activity of bone formation had decreased. On the other hand, in the recovery of occlusal function, the elongation of teeth was decreased and the activity of bone formation and regeneration had promoted.

Identification of disease-susceptibility genes related to congenital missing or supernumerary tooth., 2003 - 2004

Summary： For affected sib-pair analysis and SNPs related analysis, we selected and diagnosed patients with anomaly in tooth number such as supernumerary tooth or congenital missing, especially affected sib-pair, their consanguinities and normal control people. Affected sib-pair analysis was performed by gene typing concerned with chromosomes using samples of patients bloods and a fluorescence-labeled gene marker kit. But we could not identify the disease-susceptibility genes related to congenital missing or supernumerary tooth.
Then we adopted the mechanical stress one of which environmental factors contrasted to hereditary factors. In order to clarify the biological response to the mechanical stimuli, we investigated using the molecular biological analysis in vivo and in vitro. When the occlusal stimuli were reduced in rats, the expression of IL-1 mRNA was increased in their hypofunctional periodontium using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the expression of IL-1 mRNA was increased after the mechanical stimuli were adopted to their molars. Mechanical tensional stress of low magnitude to the bovine periodontal ligament cells on the flexible bottomed culture plate induced the increase of both type I collagen and decorin mRNA expression without changing alkaline phosphatase (ALP) activity in periodontal ligament cells. Mechanical tensional stress of low magnitude to the stromal cell line (ST2) induced the increase of Cbfa1/Runx2 mRNA expression and ALP activity without changing type I collagen mRNA expression.
These results suggest the possibility that environmental factors such as mechanical stimuli might induce anomaly in tooth number.

Analysis of the defensive mechanism against oxidative stress in periodontal ligament with aging, 2002 - 2003

Summary： It is urgently necessary to investigate the effect of aging on the periodontal ligament (PDL) because the number of elder patients in orthodontic practice is increasing. Recently, many reports in the medical field have revealed that the activities of various organs change and oxidative stress increases with aging. From this knowledge, we supposed that oxidative stress in PDL might increase with aging. Nitric oxide (NO), which is one of the bearers of oxidative stress, is erased by antioxidant agents. On the other hand, various animal experiments have clarified that external forces such as occiusal and orthodontic forces recover and improve the function of the PDL. In other words, the signals transmitted by some mechanical stresses will recover and activate the stress induced changes of PDL in cellular level.
Using some rat experiment models, the responses of the PDL to occlusal and orthodontic forces were investigated with enzyme-and immunohistochemistry.
The results were as follows: when hypofunctional PDL recovered with occlusal force, monocyte-macrophages played an important role, and eNOS and iNOS were expressed. Light and continuous orthodontic force changed the NOS activity in the PDL at shorter duration than that in some former reports. Furthermore, we examined the effect. of aging on the blood vessels in rat gingiva and revealed the change, pf geometry. This result got a foothold in analyzing the relationship between aging and mechanical stress. Finally, the signal transduction of optimum mechanical stress for activation of PDL cells and osteoblasts was partially elucidated in some in vitro studies

Damping capacity of the hollow super-elastic wire and mechanotransduction in bone metabolism activity, 2002 - 2003

Summary： During orthodontic treatment, excessive occiusal force may be contributed.to one or more teeth, moreover.unstable occiusal conditions are commonly induced. Hollow super-elastic Ti-Ni alloy wire possesses lighter continuous force and low load hysteresis, which it also has possibility to possess superior damping capacity. The purpose of this investigation has been to clarify the influence of the vibrating stimuli that are subsequently transmitted through various orthodontic arch wires upon periodontal tissues.
In experimental rat model; we examined influences upon periodontal tissues after transmitted a vibrating stimulus through orthodontic wire. We observed degeneration, inflammation, extravasations of red blood corpuscles from the blood vessels in the apical dental pulp, and other signs of damage in specimens of stimulated teeth. In sharp contrast, we observed far less damage on the periodontal tissues of teeth to which super-elastic Ti-Ni alloy wire had been attached. Furthermore periodontal tissues change was not observed in the teeth which ISW (Improved super-elastic Ti-Ni alloy wire) had been attached, So, we hypothesized that these superior damping capacity possessed in super-elastic Ti-Ni alloy wires is responsible for reducing damage during orthodontic treatment. Moreover, by using the hollow super-elastic Ti-Ni alloy wire in orthodontic treatment, its superior damping capacity will absorb excess shock transmission and induce remodeling of periodontal tissues during tooth movement (62th Annual Meeting of the Japanese Orthodontic Society, Niigata)..

Effect of different magnitudes of shock and vibrationto bone metabolism -using shock absorbing Ti-Ni alloy wire in in-vino experiment, 2000 - 2001

Summary： AIM : Titanium-nickel alloy (Ti-Ni alloy) is known to possess super-elasticity and shape memory properties, and the recent focus has also produced a high damping alloy. This study investigated the damping capacity of the super-elastic Ti-Ni alloy wire in comparison with traditional stainless steel wire.
MATERIALS : Experiment was performed with both 0.016x0.022 and 0.018x0.025 inch orthodontic stainless steel wires and varied super-elastic Ti-Ni alloy wires.
METHODS: Predetermined impact was imposed on experimental orthodontic wire with aluminum rod and the damping capacity phases of the wire were recorded by laser strain sensor. In the meantime, loading of 500gf or 1000gf was added onto the wire.
RESULTS : The damping curve of the Ti-Ni alloy wire was found to decrease abruptly, while that of the stainless steel wire decreased gradually. It was especially shown from the specific damping capacity (SDC) that the super-elastic Ti-Ni alloy wire possessed elevated damping capacity compared with that of the stainless steel wire. SDC for stainless steel wire was 83-86%, while super-elastic Ti-Ni alloy wire was 90-98%.
CONCLUSION : It has been obvious that super-elastic Ti-Ni alloy wire owns high damping capacity according to its damping curve and SDC. It also suggested that damping capacity played a role in modulating the transmission of external forces, such as occlusal forces, to other teeth during orthodontic treatment.

General investigation of malocclusion in the aspect of age-related expression mechanism, 2000 - 2001

Summary： Extracellular matrix
Occlusal hypofunction of rat unilateral mandibular molars was induced by extraction of the opposing teeth, and immunohistochemical analyzes were performed to clarify the influence of occlusal hypofunction on the changes of proteoglycan content in the periodontal ligament.
proteoglycan decreased in the periodontal ligament due to loss of occlusal function, and these results suggest that proteoglycans are closely related to occlusal function and play important roles in tissue homeostasis or tissue remodeling.
Microvasculature
We examined the effect of occlusal stimuli on the microvasculature of the periodontal ligament using a model of occlusal hypofunction in rat molars. The occlusal hypofunction caused narrowing of the periodontal membrane and reduction in the vessel size with decrease in the number of blood vessles. In this study, a mechanism is revealed that hypofunction would result in increase of the expression of endothelin, a potent vasoconstrictive factor, furthermore it also suggested the relation to expression of nitric oxide synthase(NOS), a vasodilator factor.
Periodontal mechanoreceptors
The neurophysiological properties of the periodontal mechanoreceptors were studied using an in vitro jaw-nerve preparation. Results of this study have demonstrated the effects of experimental occlusal hypofunction on the periodontal mechanical signaling. Moreover, changes related to growth and development have also been investigated
Activity of bone formation
In order to clarify the mechanism of bone remodeling under mechanical stress, cultured osteoblastic-cells were subjected to shear stress, in which we have revealed that the enhancement of intracellular Ca^<2+> depended on the property of stretch-activated channel and were modulated by the cytoskeleton such as actin filament.
We also elucidated the hypofunctional condition of the root, remodeling of the alveolar bone and the physiological tooth movement in rats. And, the experimental tooth movements under hypofunctional condition have made it more obvious that light orthodontic forces contribute to the conservation of sound periodontal tissue.

Microvascular response in the view of redox control-Elucidation of a new signal transduction-, 2000 - 2001

Summary： Periodontal microvascular responses to some mechanical stresses were studied to elucidate a new signal transduction in the periodontal membrane. Some modified models of occlusal hypo function and its recovery were used to investigate the association with oxidative stress in the microvascular response. Furthermore some orthodontic tooth movement models were used to examine the relationship. The results from this study provided an initial step towards the understanding of the redox control in the periodontal microvascular responses to various mechanical stresses.
1. Analyzes with occlusal hypo function and its recovery models
Loss of occlusal contact caused narrowing of the periodontal membrane and vasoconstriction. Enzyme- and immonohistochemistry revealed that occlusal hypofunction increased the expression of endothelin and decreased the number of monocyte macrophages and the expression of nitric oxide synthase (NOS). In the recovery of occlusal contact, the width of the periodontal membrane recovered following increased expression of NOS, invasion of blood vessels from the bone marrow to the periodontal membrane, and increased number of monocyte macrophages.
2. Analyzes with orthodontic tooth movement models
In situ hybridization showed that type I collagen mRNA expressed first in bsteoblasts and fibroblasts in tension side, and bone sialoprotein mRNA second in osteoblasts, during experimental tooth movement with heavy orthodontic force. These findings suggested those proteins might be involved in the periodontal bone remodeling. Experimental tooth movements with light forces were constant or fluctuated in cycles of several days' duration with physiological condition of periodontal tissues, in contradiction to the tooth movement using heavy force. Furthermore, a mechanical stress model, in which continuous or intermittent orthodontic force with controlled magnitude and direction of forces for a. long period was applied to the rat periodontium, was developed to investigate the responses of microvasculature to various mechanical stresses.

Biological Response of Periodontal Tissue incident to Orthodontic Tooth Movement and Occlusion

Prevention of Root Resorption incident to Orthodontic Tooth Movement

Occlusion