Effects of Attachment of Plastic Aligner in Closing of Diastema of Maxillary Dentition by Finite Element Method.

The aim of this study was to clarify the effect of attachment on tooth movement produced by a plastic aligner. Closing of a diastema, in which the maxillary right and left central incisors moved bodily, was simulated using a finite element method. Long-term orthodontic movements of the maxillary dentition were simulated by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. The incisor tipped and rotated just after placement of the aligner irrespective of the attachment. After a sufficiently long time, the incisor was upright and moved bodily in the aligner with attachment, but the incisor remained tipped in the aligner without attachment. It was demonstrated that the attachment was effective for achieving bodily movement.

Migration and Differentiation of GFP-transplanted Bone Marrow-derived Cells into Experimentally Induced Periodontal Polyp in Mice.

Perforation of floor of the dental pulp is often encountered during root canal treatment in routine clinical practice of dental caries. If perforation were large, granulation tissue would grow to form periodontal polyp. Granulation tissue consists of proliferating cells however their origin is not clear. It was shown that the cells in granulation tissue are mainly from migration of undifferentiated mesenchymal cells of the bone marrow. Hence, this study utilized GFP bone marrow transplantation mouse model. The floor of the pulp chamber in maxillary first molar was perforated using ½ dental round bur. Morphological assessment was carried out by micro CT and microscopy and GFP cell mechanism was further assessed by immunohistochemistry using double fluorescent staining with GFP-S100A4; GFP-Runx2 and GFP-CD31. Results of micro CT revealed alveolar bone resorption and widening of periodontal ligament. Histopathological examination showed proliferation of fibroblasts with some round cells and blood vessels in the granulation tissue. At 2 weeks, the outermost layer of the granulation tissue was lined by squamous cells with distinct intercellular bridges. At 4 weeks, the granulation tissue became larger than the perforation and the outermost layer was lined by relatively typical stratified squamous epithelium. Double immunofluorescent staining of GFP and Runx2 revealed that both proteins were expressed in spindle-shaped cells. Double immunofluorescent staining of GFP and CD31 revealed that both proteins were expressed in vascular endothelial cells in morphologically distinct vessels. The results suggest that fibroblasts, periodontal ligament fibroblasts and blood vessels in granulation tissue were derived from transplanted-bone marrow cells. Thus, essential growth of granulation tissue in periodontal polyp was caused by the migration of undifferentiated mesenchymal cells derived from bone marrow, which differentiated into fibroblasts and later on differentiated into other cells in response to injury.

Functional Role of HSP47 in the Periodontal Ligament Subjected to Occlusal Overload in Mice.

We carried out an experiment to induce traumatic occlusion in mice periodontal tissue and analyzed the expression of HSP47. Continuous traumatic occlusion resulted to damage and remodeling of periodontal ligament as well as increase in osteoclasts and bone resorption. Four days after traumatic occlusion, osteoclasts did not increase but Howship's lacunae became enlarged. That is, the persistent occlusal overload can destroy collagen fibers in the periodontal ligament. This was evident by the increased in HSP47 expression with the occlusal overload. HSP47 is maintained in fibroblasts for repair of damaged collagen fibers. On the other hand, osteoclasts continue to increase although the load was released. The osteoclasts that appeared on the alveolar bone surface were likely due to sustained activity. The increase in osteoclasts was estimated to occur after load application at day 4. HSP47 continued to increase until day 6 in experiment 2 but then reduced at day 10. Therefore, HSP47 appears after a period of certain activities to repair damaged collagen fibers, and the activity was returned to a state of equilibrium at day 30 with significantly diminished expression. Thus, the results suggest that HSP47 is actively involved in homeostasis of periodontal tissue subjected to occlusal overload.

Cytological Kinetics of Periodontal Ligament in an Experimental Occlusal Trauma Model.

Using a model of experimental occlusal trauma in mice, we investigated cytological kinetics of periodontal ligament by means of histopathological, immunohistochemical, and photographical analysis methods. Periodontal ligament cells at furcation areas of molar teeth in the experimental group on day 4 showed a proliferation tendency of periodontal ligament cells. The cells with a round-shaped nucleus deeply stained the hematoxylin and increased within the day 4 specimens. Ki67 positive nuclei showed a prominent increase in the group on days 4 and 7. Green Fluorescent Protein (GFP) positivity also revealed cell movement but was slightly slow compared to Ki67. It indicated that restoration of mechanism seemed conspicuous by osteoclasts and macrophages from bone-marrow-derived cells for the periodontal ligament at the furcation area. It was suggested that the remodeling of periodontal ligament with cell acceleration was evoked from the experiment for the group on day 4 and after day 7. Periodontal ligament at the furcation area of the molar teeth in this experimental model recovered using the cells in situ and the bone-marrow-derived cells.

Wnt signaling as a possible promoting factor of cell differentiation in pleomorphic adenomas.

There are well known that Wnt signaling was some roles of cell differentiation at the development tissues, especially the oral and maxillofacial regions of some developmental stages. Therefore, to determine Wnt signaling in the pleomorphic adenoma tissues, we examined. The expression of Wnt1 and ß-catenin as well as the distribution of various cytoskeletal proteins CK7 and CK13 was examined in 30 cases of pleomorphic adenoma by immunohistochemistry. Wnt1 was detected in almost all tumor cells. The peripheral columnar cells in squamous metaplasia and small cuboidal cells in duct-like structures were strongly positive to Wnt1. Although ß-catenin was clearly localized on the cell membrane of tumor cells, nuclear translocation was observed in small cuboidal cells and in some basaloid cells. The immunofluorescent staining pattern of Wnt1 and CK7 as well as Wnt1 and CK13 was consistent with IHC results. Thus, in pleomorphic adenoma, Wnt is involved in tumor cell differentiation of peripheral columnar cells forming solid nests and small peripheral columnar cells forming duct-like structures. Moreover, among the three currently known Wnt pathways, ß-catenin is the suggested pathway working during cell differentiation. Furthermore, peripheral columnar cells in solid tumor nests and in squamous metaplasia are governed by another Wnt pathway other than ß-catenin. Therefore, Wnt signaling through ß-catenin pathway may be involved in the 'mixed' differentiation characteristic of pleomorphic adenoma although another pathway may also be possibly working in other parts of the tumor tissue.

Heat shock protein27 expression and cell differentiation in ameloblastomas.

The expression of HSP27 and some CKs were examined the 40 cases of typical solid/multicystic ameloblastoma using immunohistochemical techniques. In order to examine the relevance of HSP in cell differentiation, we focused on the cytoskeletal expression of CK. CK19 is a marker of typical odontogenic epithelium widely observed in follicular and plexiform types of ameloblastomas. Since staining with CK14 is one of the measures of the differentiation potential of squamous cells and is extensively expressed in both follicular and plexiform types, it implies that squamous differentiation of each type can occur. CK8 was strongly detected in tumor nests in plexiform type but weakly detected in follicular type. It was considered that the expression of HSP27 in plexiform type correlated with the expression of CK8 suggesting that HSP27 might have regulated the expression of CK8.

Promotion of transplanted bone marrow-derived cell migration into the periodontal tissues due to orthodontic mechanical stress.

BACKGROUND: Bone marrow-derived cells (BMCs) have abilities of cell migration and differentiation into tissues/organs in the body and related with the differentiation of teeth or periodontal tissue including fibroblasts. Then, we examined the effect of orthodontic mechanical stress to the transplanted BMC migration into periodontal tissues using BMC transplantation model. MATERIAL AND METHOD: BMC from green fluorescence protein (GFP) transgenic mice were transplanted into 8-week-old female C57BL/6 immunocompromised recipient mice, which had undergone 10 Gy of lethal whole-body-irradiation. Five mice as experimental group were received orthodontic mechanical stress using separator between first molar (M1) and second molar (M2) 1 time per week for 5 weeks and 5 mice as control group were not received mechanical stress. The maxilla with M1 and M2 was removed and was immunohistochemically analyzed using a Dako Envision + Kit-K4006 and a primary anti-GFP-polyclonal rabbit antibody. Immunohistochemically stained was defined as positive area and the pixel number of positive area in the periodontal tissue was compared with the previously calculated total pixel number of the periodontal tissue. RESULTS: The immunohistochemistry revealed that GFP positive cells were detected in the periodontal tissues, both in the experimental and control specimens. The ratio of pixel number in the examination group showed 5.77 ± 3.24 % (mean ± SD); and that in the control group, 0.71 ± 0.45 % (mean ± SD). The examination group was significantly greater than that of control group (Mann-Whitney U test: p<0.001). CONCLUSION: These results suggest that orthodontic mechanical stress accelerates transplanted BMC migration into periodontal tissues.

Jagged1 peptide appearing in mandibular condylar cartilage development.

We investigated the expression pattern of Jagged1 peptide in mandibular condylar cartilage, as a type of secondary cartilage. Mandibular condyle of ddY mice were fixed from embryonic day 15 (E15) through just after birth (equivalent to E19). Serial sections were examined using histological immunohistochemical (IHC) techniques. At E15, the proliferating cells had positive products of Jagged1 in their cytoplasms and cell membrane of almost all coagulating cells. At E17, cytoplasmic and membranuous reactions of Jagged1 factors appeared strongly in the cells just inside the condylar cartilage sheath. At E18, Jagged1 positive products were observed in almost all cells of the layers, and they were mostly distinct in the sheath of the condyle. At just after birth, Jagged1 was observed in a portion of almost all layer cells in their cytoplasm and membrane. These results suggest that Jagged1 plays an essential role for mandibular condylar cartilage morphogenesis and development.

Tissue reaction to poly (lactic-co-glycolic acid) copolymer membrane in rhBMP used rabbit experimental mandibular reconstruction.

A rabbit experimental mandibular defect was reconstructed with 1% atelocollagen gel including rhBMP-2 10microg and a covering a poly (lactic-co-glycolic acid) copolymer (PLGA) membrane. For this experiment, eight male rabbits were used and a histological study was conducted. Our study purpose was to examine the effects and fate of PLGA membrane during bone reconstruction. PLGA membrane was phagocytized by foreign body giant cells and macrophages in the healing course of reconstruction osteogenesis. These histological data suggest that the PLGA membrane was gradually absorbed and replaced by fibrous connective tissue or bone tissue. In the osteogenesis course, the outer periphery of the new bone was maintained by PLGA membrane without expansion.

Assessment of cell proliferation during mandibular distraction osteogenesis in the maturing rat.

INTRODUCTION: The cellular mechanisms controlling distraction osteogenesis are not well understood. The purpose of this study was to examine the role of cell proliferation in the regulation of mandibular distraction osteogenesis. METHODS: Unilateral mandibular ramus osteotomies were performed on 125 3-month-old Sprague-Dawley rats. The rats were randomized into 4 distraction rate groups and distracted for 5 days after 3-day latency. Rats (7 or 8 from each rate group) were killed at 4 time points. The rats received 5-bromo-2-deoxyuridine (BrdU) injections (40 mg per kilogram, i.p.) at day 3 (end of latency). RESULTS: Both intramembranous and endochondral ossification was seen in the osteogenesis area. BrdU+ mesenchymal progenitor cells were significantly higher at day 10 (P <.05) and were found most numerously around the sagittal middle portion of the gap (P <.01). The greatest numbers of BrdU+ osteocytes were seen at day 38 (P <.05). Both BrdU+ osteoclasts and chondrocytes peaked at day 24. CONCLUSIONS: Mesenchymal progenitor cells are mostly recruited in the early consolidation period, but they decrease in the middle and late consolidation periods during mandibular distraction osteogenesis. The rapid rate might suppress or sustain the proliferation and differentiation of mesenchymal progenitor cells during mandibular distraction osteogenesis. BrdU+ cells can survive throughout the entire experimental period of 5 weeks.

Prostaglandin E2 strongly inhibits human osteoclast formation.

Prostaglandin E(2) (PGE(2)) enhances osteoclast formation in mouse macrophage cultures treated with receptor activator of nuclear factor-kappaB ligand (RANKL). The effects of PGE(2) on human osteoclast formation were examined in cultures of CD14(+) cells prepared from human peripheral blood mononuclear cells. CD14(+) cells differentiated into osteoclasts in the presence of RANKL and macrophage colony-stimulating factor. CD14(+) cells expressed EP2 and EP4, but not EP1 or EP3, whereas CD14(+) cell-derived osteoclasts expressed none of the PGE(2) receptors. PGE(2) and PGE(1) alcohol (an EP2/4 agonist) stimulated cAMP production in CD14(+) cells. In contrast to mouse macrophage cultures, PGE(2) and PGE(1) alcohol inhibited RANKL-induced human osteoclast formation in CD14(+) cell cultures. H-89 blocked the inhibitory effect of PGE(2) on human osteoclast formation. These results suggest that the inhibitory effect of PGE(2) on human osteoclast formation is mediated by EP2/EP4 signals. SaOS4/3 cells have been shown to support human osteoclast formation in cocultures with human peripheral blood mononuclear cells in response to PTH. PGE(2) inhibited PTH-induced osteoclast formation in cocultures of SaOS4/3 cells and CD14(+) cells. Conversely, NS398 (a cyclooxygenase 2 inhibitor) enhanced osteoclast formation induced by PTH in the cocultures. The conditioned medium of CD14(+) cells pretreated with PGE(2) inhibited RANKL-induced osteoclast formation not only in human CD14(+) cell cultures, but also in mouse macrophage cultures. These results suggest that PGE(2) inhibits human osteoclast formation through the production of an inhibitory factor(s) for osteoclastogenesis of osteoclast precursors.

Expression of Notch1 and Math1 in mandibular condyle cartilage in neonatal mice.

On the basis of the cellular morphological changes in the cartilaginous area, the mandibular condylar cartilage is histopathologically composed of four different cell layers--fibrous, proliferative, maturative, and hypertrophic. Reaction for Notch1 was present in the hypertrophic cells only. However, Math1 was locally distributed in the hypertrophic layer and partially in the proliferative layer. The expression patterns of Notch1 and Math1 were slightly different. These results suggest that the morphogenesis regulation factors of Notch1 and Math1 may play some role in mandibular condylar cartilage. Positive reactions to osteopontin, as a control, were detected in the cytoplasm of all layers, although they varied from published data.