Recently, we developed glass fiber-reinforced plastic(GFRP)orthodontic wire made from polycarbonate and glass fiber. The purpose of this study was to compare GFRP wire with nickel-titanium(NiTi)wire as assessed by the amount of tooth movement, the early tissue reaction of the periodontal ligament (PDL), and tartrate-resistant acid phosphatase (TRAP)expression in an experimental dog model of tooth movement in vivo. GFRP round wire, with a diameter of 0.45 mm(0.018-in), was prepared using 7µm glass fibers. As a control, wires made of NiTi were also evaluated. The maxillary second and third premolars were moved buccally for 5 weeks in five beagles. The change in second and third premolar widths in NiTi and GFRP wires(P2WN, P2WG, P3WN and P3WG)were investigated. Furthermore, histological findings in the PDL and TRAP expression levels in the alveolar bone(AB)surface were measured. The amount of tooth movement in the GFRP group was roughly equal to that in the NiTi group. The numbers of TRAP-positive cells were not significantly increased in either group at 5 weeks. No significant differences in any parameters before and after treatment were noted between the two groups. GFRP wire showed equivalent efficiency to commercial NiTi wire in the amount of tooth movement and histological findings of periodontal tissues during experimental tooth movement. Therefore, GFRP wire can be used in place of NiTi wire at the initial leveling stage.
Secretory granules (SGs) of salivary glands are considered to be generated as an immature granule and to mature by condensing their contents. Syntaxin 6 and vesicle associated membrane protein 4 (VAMP4) are detected in the membrane fractions of immature but not mature SGs, suggesting that syntaxin 6 and VAMP4 are transported from SGs to other organelles during the process of granule maturation. To study the role of syntaxin 6 in the biogenesis of granules, we transfected syntaxin 6 fused with enhanced green fluorescent protein(EGFP)into primary cultured parotid acinar cells. The EGFPsyntaxin 6 signal overlapped with that of an early endosome marker, early endosome antigen 1(EEA1), which was detected using immunofluorescence. The localization of EGFP-fused VAMP4 was also similar to that of EEA1, suggesting that syntaxin 6 and VAMP4 are transported from immature SGs to early endosomes. Transfection of a syntaxin 6 mutant that lacks a SNARE-binding domain caused a decrease in the number of SGs although the localization of the mutant was unchanged from that of the wild type syntaxin 6. These results suggest that syntaxin 6 has an important role in the maintenance of SGs in parotid acinar cells.
IL-1β and TNF-α are proinflammatory cytokines that affect inflammatory responses and matrix degradation. Although interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF-α) have been detected in the synovial fluids from patients such as temporomandibular joint disorders(TMD), there is little known about the molecular mechanisms of inflammatory conditions of TMD. To identify putative factors associated with temporomandibular joint(TMJ) inflammation, we investigated IL-1β and/or TNF-α-responsive genes of synovial fibroblasts from patients with TMD using microarray analysis. Granulocyte macrophage colony stimulating factor(GM-CSF)was one of the genes whose expression was strongly up-regulated in synovial fibroblasts by IL-1β and/or TNF-α. The gene expressions of macrophage colony stimulating factor(M-CSF)and Granulocyte colony stimulating factor(G-CSF) were also up-regulated by IL-1β and/or TNF-α. Gene expression and protein production of GM-CSF and G-CSF, but not of M-CSF, were synergistically increased in synovial fibroblasts stimulated with IL-1β and TNF-α. M-CSF protein was only detected in the conditioned medium of the non-stimulated control in which GM-CSF and G-CSF were not detected. In addition, MAPK and NFκB inhibitors inhibited IL-1β and TNF-α stimulated production of GM-CSF and M-CSF. CSFs act on hemopoietic cells as growth factors and activation/differentiation factors. These results suggest that expression of CSFs in synovial fibroblasts stimulated by IL-1β and/or TNF-α is one factor associated with inflammatory progression of the intracapsular pathological conditions of the TMJ.
It has been reported that bisphosphonate treatment induces medication-related osteonecrosis of the jaw(MRONJ). Although dental extraction, periodontal disease and systemic disease are noted as risk factors for MRONJ, there are few reports examining the relationship between oral hygiene and MRONJ. The purpose of this retrospective study was to determine risk factors for MRONJ occurrence, and to assess whether MRONJ occurrence is suppressed by professional oral hygiene management or not.
The participants were patients undergoing zoledronate treatment. Dental examination was undertaken by dentists or dental hygienists every six months during the consultation period. The participants were divided into intervention and non-intervention groups. The former underwent professional oral hygiene management by a dental hygienist every three or four weeks, whereas the latter group did not desire professional oral hygiene management.
Two participants in the intervention group(n=40)and four participants in the nonintervention group(n=11)developed MRONJ. The incidence of MRONJ was significantly reduced in the intervention group when compared with the non-intervention group(p=0.015). The onset of MRONJ in the intervention group was significantly prolonged(p=0.003). In addition, proportional hazards analysis indicated that the only significant factor in the development of MRONJ was the delivery of oral hygiene management(p<0.05), and the hazard ratio was 0.109.
It is suggested that oral hygiene management suppressed the development of MRONJ.There is a possibility that MRONJ could be suppressed by regular oral hygiene management performed by a dental hygienist.
Since saliva is essential for maintenance of a healthy oral environment, the secretory function of the salivary gland is important in clinical dentistry. Although tissue injuries result in a decrease in acinar cells and consequent dysfunction of saliva secretion, the number of acinar cells recovers if the damage is not too severe. The origin of the regenerated acinar cells is unclear. One hypothesis is that acinar cells that are atrophied in response to tissue injuries can re-differentiate. We have previously established a primary culture of parotid acinar cells to study the mechanism of dysfunction and regeneration of salivary glands. During the culture, the expression levels of acinar markers decreased,whereas immature ductal markers increased, suggesting that the cells changed to immature duct-like cells. In this study, to clarify the properties of the cultured cells, the expression of nestin, a stem cell marker of the pancreas, was examined. It was found that nestin began to be expressed and increased during the culture. On immunofluorescence microscopy, nestin-expressing cells had secretory granules, indicating that the cells were derived from acinar cells. Src family kinase inhibitor PP1 suppressed the expression of nestin. It is possible that nestin expression is a programmed response to survive cellular stresses and to acquire re-differentiation potential.
The information handling processes for character and tooth recognition tasks were compared between the dental students who had acquired different knowledge levels. The subjects included 20 second-year students who had acquired textbook-based knowledge and 20 fifth-year students who had acquired both textbook-based and experience knowledge though ongoing clinical exercise. The task was to differentiate diagrams depicting a “katakana character” or a “tooth”. The diagrams were randomly presented at a ratio of 2: 8 according to the oddball paradigm. The subjects were instructed to push a button only when a target stimulus was presented. Average waveforms were determined by averaging ERP waveforms derived at Pz for a principal component analysis(PCA).
The results showed the same trends in information for character diagrams in both year students; the contribution rates of the PCA component representing pattern matching or attention-orientation as well as working memory update was higher. Similar trends were observed in information for tooth diagrams in terms of a greater percentage of the PCA components represented cognition and decision and behavior performance, but in the fifthyear students P3a that represented attention-orientation was extracted independently.
These results indicate similar information in both-year students for the character task,whereas fifth-year students who had acquired experience knowledge appeared to make their decisions based on more effective thinking for the tooth task.
The synovial membrane is composed of fibroblast-like cells(synovial fibroblasts)and macrophage-like cells. Synovial fibroblasts and monocytes/macrophages are believed to interact and to play a critical role in the development of synovial inflammation. In this study, we investigated the protein production of pro-inflammatory cytokines in co-culture of synovial fibroblasts isolated from the temporomandibular joint(TMJ)and monocytes isolated from peripheral blood. Monocytes that had attached to the plastic surface after culture for 3 days in RPMI containing 10% FBS, exhibited two types of morphologies: “fried egg” and “spindle-like”. Both types of monocytes stained positive for the macrophagespecific markers CD14 and CD68. Synovial fibroblasts were co-cultured with these monocytes for 12 days. Synovial fibroblasts or monocytes were also cultured alone for 12days. The conditioned media were collected every 3 days, following which fresh medium was added to each culture. The protein concentrations of IL-1β, IL-6, and IL-8 in the conditioned media were measured using ELISA. The protein production of IL-1β, IL-6 and IL-8 was greatly increased in the co-culture of synovial fibroblasts and monocytes compared to each monoculture. These data suggest that interaction between monocytes/macrophages and synovial fibroblasts is likely to contribute to the promotion of, and to increase the inflammatory condition in the TMJ.
We analyzed the masticatory movement patterns of patients with skeletal Class I or III malocclusion who had lateral deviations of the jaw and were treated using orthognathic surgery. The aims of this study were (1) to compare the chewing patterns at initial examination(T1), after removal of each participantʼs orthodontic appliance(T2), and after ≥1 year of maintenance(T3), and(2)to analyze the effects of different chewing patterns on changes in the axial inclination of the first molars. A Gnatho-Hexagraph III was used to measure the chewing patterns(with six degrees of freedom)of 21 participants(mean age: 23.2±5.4 years)with a menton deviation≥4 mm from the midline. A three-dimensional digital scanner was used to measure the axial inclination of the maxillary and mandibular first molars. Participants with normal chewing patterns on both the affected and unaffected sides at T1 had the same pattern at T2 and T3. In addition, 50% of the participants with reversed chewing patterns on the affected side at T1 exhibited normal patterns at T2, while 33.3% retained their original reversed pattern. Compared to the participants with normal chewing patterns, those with reversed patterns showed a significantly greater change in the inclination of maxillary and mandibular first molars on the affected side between T2 and T3. Palatal, maxillary first molar, and mandibular first molar widths showed similar results. Moreover, participants with normal chewing patterns had few changes in the buccolingual molar inclination; hence, the orientation of the molars remained unchanged.
The results showed that the axial inclination of the molars was associated with the masticatory movement pattern after orthognathic surgery, which affected molar occlusion.
This study was approved by the Ethics Committee of Nihon Universityʼs School of Dentistry at Matsudo(approval no. EC16-15-004-2)
Hypophosphatasia(HPP)is caused by mutations in the gene encoding tissue-nonspecific alkaline phosphatase(ALPL). HPP patients develop deficient calcification of bones and teeth including defects in cementum, dentin, and enamel and the characteristic premature loss of primary teeth. Here, we investigated the enamel defects of knockout(Alpl-/-)mice compared with that of control wild type(Alpl+/+)mice.
No alkaline phosphatase(ALP)activity was detected by specific staining in the first molar germ of Alpl-/- mice on postnatal day 5. Hematoxylin and eosin staining revealed that the enamel layer in Alpl-/- mice was thin, undulated, and rugged. Furthermore, Alpl-/mice had abnormal ameloblasts and the dentin-predentin layer blur and the abuttal not well defined. Some enamel defects matched non-homogeneous distribution of the enamel matrix proteins(EMPs); amelogenin(AMELX), ameloblastin(AMBN), and enamelin(ENAM), as shown by immunohistochemistry. Microarray analysis revealed that several expressions of genes related to enamel development were reduced in Alpl-/- mice. Furthermore, gene expressions of both Ambn and Enam were significantly lower in Alpl-/- mice than in Alpl+/+ mice, as determined by quantitative real time PCR analysis.(p<0.05).
Our study suggests that ALP may have involvement in EMPs and enamel defects in Alpl-/- mice is caused by ameloblasts disorder. Furthermore, our study advances elucidation of the mechanisms that underlie enamel development, and will support establish the causes of enamel defects of HPP patients.
Sagittal split ramus osteotomy(SSRO)is widely used for skeletal mandibular prognathism, but various changes are seen after SSRO. Changes in the position of the mandible immediately after surgery can lead to unstable occlusion and prolonged orthodontic treatment. The aims of this study were to examine the changes in the positions of the proximal fragment and the condylar head of the mandible and to investigate the morphological changes in the condylar head of the mandible using CT images acquired before SSRO(BO)and 1 month(AO1)and 6 months(AO6)after SSRO.
1. Significant changes in the axial condylar angle were found at BO-AO1 and at BO-AO6.
However, significant changes in measurements on the coronal plane were not found at BO, AO1, or AO6. Significant changes in the distance between the mandibular fossa and the condylar head of the mandible on the axial plane were also not found at BO, AO1, or AO6.
2. There were significant differences in the proximal fragment along the X-axis and Z-axis from BO to AO1. There was no significant difference in the proximal fragment from AO1 to AO6.
3. The height(SH and CH)of the condyle was significantly decreased from AO1 to AO6.
4. Changes of the proximal fragment along the X-axis were correlated with the width of the condyle, and changes along the Y-axis were inversely correlated with height, sagittal width, and axial width of the condyle. Changes of the proximal fragment along the Z-axis were inversely correlated with the axial width of the condyle.
5. Reductional bony change was found in areas B, C, E, and F, while additional bony change was found in areas B and G.
In conclusion, external and superior displacement of the proximal fragment and positional changes of the condylar head of the mandible due to external, superior, and internal rotation often occurred immediately after SSRO. It was suggested that bone remodeling was found from the external surface of the condylar head of the mandible to its antero-superior aspect.
Maintenance and improvement of masticatory function in nursing care elderly persons (NC) is an important issue, and it is speculated that sarcopenia is related to declining masticatory function. The decrease in skeletal muscle index(SMI), a major diagnostic criterion for sarcopenia, has been reported to be associated with swallowing function in NC.However, the relationship between SMI and masticatory function is unknown. Therefore,we investigated the relationship between masseter muscle thickness(MMT)and SMI, with the aim of examining the specific relationship between decreased masticatory function and sarcopenia in NC. MMT and SMI were measured by ultrasonography and bioelectrical impedance analysis in 275 NC participants in Omori Town, Yokote City, Akita Prefecture in the Tohoku region in Japan. Cognitive functions measured from all participants using questionnaire. Participants were classified into low-MMT or high-MMT group based on the median of each of MMT, and SMI and related items in each gender. In addition, to examine the factors related to MMT, logistic regression analysis was conducted by entering age,sex, SMI, nutrition status, severity of dementia, and other items as explanatory variables and MMT as objective variable. SMI in high-MMT group were significantly higher than low-MMT group(high-MMT: 4.8±1.4 kg/m2, low-MMT: 4.4±1.4 kg/m2, P=0.010).
Furthermore, logistic regression analysis indicated that SMI were significantly associated with a MMT(Odds Ratio=0.83, 95% Confidence Interval=0.69-0.99, P=0.049). Our result suggested that the mass of the masseter muscles decreased with NC due to sarcopenia, possibly contributing to a decrease in masticatory function.
The initial stages of dental biofilm formation involved the adherence of early colonizing organisms such as Streptococcus gordonii on the saliva-coated tooth surface. The surface protein SspB of S. gordonii is known to play a role in adherence to salivary protein and mediates coaggregation with other bacteria. We previously demonstrated that the analogous SspB peptide, SspB(390-T400K-402), effectively bound to salivary agglutinin peptide SRCRP2 (scavenger receptor cysteine-rich domain peptide 2). To investigate molecular interaction of supra- and sub-gingival dental plaque biofilm formation among streptococci, periodontal bacteria, and salivary agglutinin as a unit, we examined the binding activity of the SspB(390-T400K-402)peptide to periodontal bacteria. The binding activity of SspB(390-T400K-402)was detected by ELISA. The SspB(390-T400K-402) peptide bound to P. gingivalis ATCC 33277, F. nucleatum ATCC 23726, and F. nucleatum #20. This binding was reduced by the presence of whole saliva; however, the presence of SRCRP2 enhanced the binding of the SspB peptide to these bacteria. These findings suggest that the binding ability of S. gordonii to these periodontal bacteria may provide,either directly(by attachment to P. gingivalis Mfa1)or indirectly(by attachment to F. nucleatum), a support system for the colonization and the biofilm formation of periodontal bacteria.
Neurotrauma and neurodegenerative diseases are associated with the loss of functioning neural cells in the nervous system. Many studies reported that function can be restored by replacing lost cells with stem cells that can mature into neural cells. From this perspective,mesenchymal stem cells represent a valuable tool for regenerative therapy because of their ability to differentiate along several lineages, such as adipocytes, osteoblasts, chondrocytes and neural cells. The dental follicle is an ectomesenchymal tissue surrounding the developing tooth germ. Human dental follicle cells(hDFCs)have the capacity to commit to differentiation into multiple cell types. In this study, we investigated the capacity of hDFCs to differentiate into neural cells, and the efficiency of the neural differentiation process.
There was a gene relevant to a neural cell in hDFC. We expanded these findings to address the gene expression of neural markers in hDFCs during neuronal differentiation. The expression levels of Musashi(MSI)-1 and -2, which are neural progenitor cell markers,microtubule-associated protein 2 (MAP2) which is a neuronal cell marker, and glial fibrillary acidic protein (GFAP)and myelin basic protein (MBP), which are glial cell markers, were up-regulated in hDFCs undergoing neural differentiation during culture in neuronal differentiation medium. The expression of tubulin-β-III(TUBB3), which is an early neuronal cell marker, was peaked on day 3. Furthermore, expression of Nestin(NES) did not change. In conclusion, these in vitro data suggest that hDFCs have the capacity to differentiate along neural lineages, raising the possibility that hDFCs may represent a practical and convenient source of adult stem cells for cell-based therapies to treat neurological diseases or trauma.
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