Adaptation of rat jaw muscle fibers in postnatal development with a different food consistency: an immunohistochemical and electromyographic study.

The development of the craniofacial system occurs, among other reasons, as a response to functional needs. In particular, the deficiency of the proper masticatory stimulus affects the growth. The purpose of this study was to relate alterations of muscle activity during postnatal development to adaptational changes in the muscle fibers. Fourteen 21-day-old Wistar strain male rats were randomly divided into two groups and fed on either a solid (hard-diet group) or a powder (soft-diet group) diet for 63 days. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time), the total burst number and their average length exceeding specified levels of the peak activity (5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of fibers by means of immunohistochemical staining and their cross-sectional area was measured. All muscle fibers were identified as slow type I and fast type IIA, IIX or IIB (respectively, with increasing twitch contraction speed and fatigability). At lower activity levels (exceeding 5% of the peak activity), the duty time of the anterior belly of the digastric muscle was significantly higher in the soft-diet group than in the hard-diet group (P < 0.05). At higher activity levels (exceeding 20 and 50% of the peak activity), the duty time of the superficial masseter muscle in the soft-diet group was significantly lower than that in the hard-diet group (P < 0.05). There was no difference in the duty time of the anterior temporalis muscle at any muscle activity level. The percentage of type IIA fibers of the superficial masseter muscle in the soft-diet group was significantly lower than that in the hard-diet group (P < 0.01) and the opposite was true with regard to type IIB fibers (P < 0.05). The cross-sectional area of type IIX and type IIB fibers of the superficial masseter muscle was significantly smaller in the soft-diet group than in the hard-diet group (P < 0.05). There was no difference in the muscle fiber composition and the cross-sectional area of the anterior belly of the digastric and anterior temporalis muscles. In conclusion, for the jaw muscles of male rats reared on a soft diet, the slow-to-fast transition of muscle fiber was shown in only the superficial masseter muscle. Therefore, the reduction in the amount of powerful muscle contractions could be important for the slow-to-fast transition of the myosin heavy chain isoform in muscle fibers.


Ultrasound stimulation induces PGE(2) synthesis promoting cementoblastic differentiation through EP2/EP4 receptor pathway.

The present study aims to provide insights into how ultrasound treatment (US) can affect the regenerative response of cementum by evaluating the role of prostaglandin E(2) induced by ultrasound stimulation on cementoblastic differentiation. The mouse cementoblast cell line OCCM-30 was exposed to low-intensity ultrasound and the cyclooxygenase-2 (COX-2) mRNA expression and prostaglandin E(2) (PGE(2)) production were quantified. The role of the US-induced PGE(2) in mineralization was examined using COX-2 inhibitor and prostaglandin receptors (EP-receptors) agonists and antagonists. In addition, gene expression of differentiation markers related to mineral metabolism was evaluated. Ultrasound significantly enhanced COX-2 mRNA expression and PGE(2) production. PGE(2) induced by US mediated mineral nodule formation, whereas COX-2 inhibitor treatment eliminated the enhancement of mineralization induced by US stimulation. Mineral deposition was also inhibited by treatment with EP2 or EP4 antagonist. Moreover, up-regulation of differentiation markers induced by US was suppressed by treatment with COX-2 inhibitor. The present findings provide evidence that US stimulation has a positive effect on mineralization ability of cementoblasts through the activation of EP2/EP4 pathway, suggesting that US can be a promising therapeutic tool for cementum repair.


Modulation of hyaluronan fragmentation by interleukin-1β in synovial membrane cells

Hyaluronan (HA) plays a crucial role in the lubricating and buffering properties of synovial fluid. The purpose of this study was to examine the effects of interleukin (IL)-1beta on HA degradation in cultured synovial membrane cells. The rabbit synovial membrane cell line HIG-82 was cultured with and without IL-1beta. The amounts of HA of varying molecular weights in the medium were analyzed using high-performance liquid chromatography, the mRNA levels of HA synthase (HAS) and hyaluronidase (HYAL) were analyzed by means of real-time PCR, and HYAL activity was analyzed by HA zymography. The amounts of HA with a molecular weight lower than 300 kDa, and between 300 and 1900 kDa, in the culture medium of HIG-82 cells were significantly higher in the presence of IL-1beta. However, the amount of HA with a molecular weight greater than 1900 kDa was significantly lower in the presence of IL-1beta. Both HAS2 and HAS3 mRNA levels were upregulated by treatment with IL-1beta. So, too, were the levels of HYAL1 and HYAL2 mRNA, which resulted in enhanced HYAL activity. However, HYAL activity was inhibited by transfection of HYAL2-siRNA. Our results suggest that IL-1beta is a crucial factor in the fragmentation of HA in inflammatory joints.


Applying an excessive mechanical stress alters the effect of subchondral osteoblasts on chondrocytes in a co-culture system.

Osteoarthritis (OA) sometimes occurs as a consequence of repeated microtrauma involved in parafunction, which may lead to microfracture in the subchondral bone. The aim of this in vitro study was to evaluate the effects of subchondral osteoblasts in loading with repeated excessive mechanical stress on the metabolism of overlying chondrocytes. A high-magnitude cyclic tensile stress of 15 kPa (30 cycles min(-1)) was applied to the cultured osteoblasts obtained from porcine mandibular condyles. The chondrocytes in alginate beads were then co-cultured with mechanically stressed or unstressed osteoblasts. Chondrocytes co-cultured with unstressed osteoblasts showed a phenotypic shift to hypertrophic chondrocytes, characterized by decreased expression of type II collagen, aggrecan, Sry-related HMG box (SOX-9), and cartilage oligomeric matrix protein (COMP) genes and increased expression of type X collagen and bone sialoprotein (BSP) genes, suggesting that the co-culture may change the chondrocyte differentiation to some extent. These changes were more distinct in chondrocytes co-cultured with excessively mechanically stressed osteoblasts. After co-culture with stressed osteoblasts, the expressions of matrix metalloproteinase (MMP)1, MMP3 and MMP13 genes were also enhanced and the synthesis of DNA, proteoglycan and collagen were significantly decreased in chondrocytes. These results demonstrate that alterations in cartilage metabolism can be induced by stressed osteoblasts, indicating a possible explanation for the onset and progression of OA.


Modulation of hyaluronan catabolism in chondrocytes by mechanical stimuli

Hyaluronan (HA) is a component of the extracellular matrices of cartilage contributing to the structural and functional integrity. HA metabolism is regulated by both anabolic and catabolic processes; however, a great deal more of the detail has been unknown yet. The purpose of this study was to clarify the effect of excessive mechanical load on the expression and activity of hyaluronidase (HYAL) in chondrocytes with a special reference to the expressions of IL-1beta and tumor necrosis factor (TNF)-alpha. A cyclic tensile load of 22.8% cell elongation, regarded as an excessive mechanical stimulus, was applied to cultured rabbit knee articular chondrocytes. HYAL1, HYAL2, IL-1beta, and TNF-alpha mRNA levels were examined by quantitative real-time PCR analysis. The HYAL activity in culture medium was examined by HA zymography. Both HYAL1 and HYAL2 mRNA levels were upregulated significantly by the loading in cultured chondrocytes. HYAL activity was also enhanced as compared with unloaded controls. The IL-1beta mRNA level was upregulated significantly by the loading, and TNF-alpha mRNA level was slightly upregulated. HYAL1 and HYAL2 mRNA levels were upregulated significantly by IL-1beta treatment, resulting in a slight increase in HYAL activity. These results show that the expression of HYAL1 and HYAL2 in articular chondrocytes is enhanced by excessive mechanical stimuli and affected in part by induction of IL-1beta, leading to HA catabolism in articular cartilage. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 2009.

Journal of Biomedical Materials Research. Part A


Inhibitory effects of orally administrated liposomal bovine lactoferrin on the LPS-induced osteoclastogenesis.

Bovine lactoferrin (bLF) modulates the production of proinflammatory cytokines including tumor necrosis factor (TNF)-alpha, and may thus control alveolar bone destruction associated with periodontitis. In this study, the effects of bLF on mRNA expression in lipopolysaccharide (LPS)-stimulated osteoblasts (OBs) and on LPS-induced osteoclastogenesis were examined. The inhibitory effects of oral administration of liposomal-bLF (L-bLF), which improved the robustness of bLF to digestive enzymes, on alveolar bone resorption using LPS-induced periodontitis rat model are also reported. Three groups of 7-week-old male Wistar rats were treated with L-bLF (L-bLF group), bLF (bLF group), or the vehicle (control group) in drinking water (n=6 in each group). On day 7, LPS was topically applied into the gingival sulcus. Number of osteoclasts and immunoexpression of TNF-alpha were analyzed. The bLF inhibited the upregulation of TNF-alpha-mRNA- and upregulation of receptor activator of NFkappaB (RANKL)-mRNA expression and eliminated downregulation of osteoprotegerin (OPG)-mRNA expression in LPS-stimulated OBs and reduced LPS-induced osteoclastogenesis in co-culture with primary OBs and bone marrow cells. In the control group, the number of osteoclasts increased after LPS treatment. The number of osteoclasts that appeared along the alveolar bone margin was significantly reduced (P<0.01) in the L-bLF but not in the bLF group. Furthermore, L-bLF suppressed upregulation of TNF-alpha immunoexpression in periodontal tissue and TNF-alpha and interleukin (IL)-1beta-mRNA level in gingival tissue. The results of this study indicate that oral administration of L-bLF significantly reduces alveolar bone resorption induced by LPS stimulation through inhibition of TNF-alpha production and modulation of RANKL/OPG balance in OBs. It is suggested that L-bLF could be a potent therapeutic and preventive agent for attenuating alveolar bone destruction in periodontitis patients.Laboratory Investigation advance online publication, 26 April 2010; doi:10.1038/labinvest.2010.80.

Laboratory Investigation; a Journal of Technical Methods and Pathology


Antibacterial activity of composite resin with glass-ionomer filler particles

The purpose of this study was to examine the antibacterial activity of composite resin with glass-ionomer filler particles versus that of contemporary commercial composite resins. Three composite resins were used: Beautifil II (containing S-PRG filler), Clearfil AP-X, and Filtek Z250. Resin blocks were bonded to maxillary first molars, and plaque accumulation on the resin block surface was examined after 8 hours. For the antibacterial test, the number of Streptococcus mutans in contact with the composite resin blocks after incubation for 12 hours was determined, and adherence of radiolabeled bacteria was evaluated. Less dental plaque was formed on Beautifil II resin block as compared to the other two materials. Antibacterial test revealed that there were no significant differences in the number of Streptococcus mutans among the three composite resins. However, the adherence of radiolabeled bacteria to the saliva-treated resin surface was significantly (p>0.01) lower in Beautifil II than in the other two materials. These results suggested that Beautifil II could reduce dental plaque formation and bacterial adherence, leading to prevention of secondary caries


Adult Class lll Treatment Using a J-Hook Headgear to the Mandibular Arch.

ABSTRACT Objective: To evaluate the treatment effects of high-pull J-hook headgear on the lower dental arch in nongrowing Class III patients. Materials and Methods: Fourteen nongrowing Class III patients having an Angle Class III malocclusion and ANB angle of less than 1.0 degree, were treated with high-pull J-hook headgear to the lower arch. Using lateral cephalograms and plaster models obtained before treatment (T1), after active treatment (T2), and after the retention period (T3), the treatment outcome was analyzed. Results: The incisal edge of the lower central incisor moved a mean of 1.2 mm to the lingual and 1.7 mm to the occlusal between T1 and T2. The axis of the lower incisor inclined 4.0 degrees to the lingual. The lower first molar cusp moved 1.5 mm to the distal and the root apex moved 2.0 mm to the mesial. Molar angulations were tipped 9.8 degrees to the distal. The occlusal plane showed 4.5 degrees counterclockwise rotation. The mean intermolar width increased 1.5 mm on average. Comparison of the records between T2 and T3 showed minimal changes. Conclusions: Distal movement of the lower dental arch using J-hook headgear was clearly demonstrated, confirming that the application of high-pull J-hook headgear to the lower arch was effective for improvement of the Class III occlusion.


Effects of mechanical stimuli on the synthesis of superficial zone protein in chondrocytes

Superficial zone protein (SZP) has been demonstrated to contribute to the boundary lubrication in synovial joints. This study was designed to clarify the modulation of SZP expression by mechanical stress in articular chondrocytes. Cyclic tensile strains of 7 and 21% cell elongation were applied to cultured chondrocytes obtained from porcine mandibular condylar cartilage. The mRNA levels of SZP, IL-1 beta, and TGF-beta1 were examined by a quantitative real-time PCR analysis. Protein level of SZP was examined by Western blotting. The SZP mRNA level was significantly upregulated after 12, 24, and 48 h by 7% elongation. Although SZP mRNA level was upregulated by 21% elongation after 12 h, it decreased to a lower level than the control after 48 h. The TGF-beta1 mRNA level exhibited an almost similar change to SZP. The IL-1 beta mRNA level was not changed markedly by 7% elongation. However, the IL-1 beta mRNA level was significantly increased by a 12-h application of 21% elongation. Western blot analysis revealed that the SZP expression was increased by 7% elongation, but decreased remarkably by 21% elongation. It is suggested from these findings that the SZP expression level in the chondrocytes is enhanced by optimal mechanical stimuli, but inhibited by excessive loading partly affected by TGF-beta1 and IL-1 beta, leading to the deterioration of joint lubrication. (c) 2009 Wiley Periodicals, Inc.


Activation of the hypoxia-inducible factor-1 in overloaded temporomandibular joint, and induction of osteoclastogenesis.

Vascular endothelial growth factor (Vegf) was previously shown to be expressed specifically in the condylar cartilage of temporomandibular joint-osteoarthritis (TMJ-OA) model rats. Here we demonstrate for the first time that hypoxia-inducible factor-1alpha (Hif-1alpha) is activated in mature chondrocytes of temporomandibular joint-osteoarthritis (TMJ-OA) model rat by mechanical overload, and that activated Hif-1 in chondrocytes can induce osteoclastogenesis via repression of osteoprotegerin (Opg) expression. In rat TMJs, degeneration of the condylar cartilage became prominent in proportion to the duration of overloading. Hif-1alpha expression was observed specifically in mature and hypertrophic chondrocytes, and Hif-1alpha-positivity, level of Vegf expression, and tartrate-resistant acid phosphatase (TRAP)-positive cell numbers all increased in the same manner. When ATDC5 cells induced differentiation by insulin were cultured under hypoxia, Hif-1alpha induction was observed in mature stage, but not in immature stage. Inductions of Hif-1-target genes showed a similar expression pattern. In addition, expression of Opg decreased in hypoxia, and Hif-1alpha played a role, in part, in its regulation.

Biochemical and Biophysical Research Communications


Effects of mechanical load on the expression and activity of hyaluronidase in cultured synovial membrane cells

Hyaluronan (HA) has lubricating and buffering functions in joints. Mechanical load is a regulatory factor of HA metabolism in joints, and HA synthesis by synovial membrane cells is modulated by mechanical load. However, the effects of mechanical load on HA catabolism by hyaluronidase (HYAL) in synovial membrane cells remain unclear. The purpose of this study was to evaluate the effects of cyclic tensile load on the expression and activity of HYAL in synovial membrane cells. A cyclic tensile load of 22.8% cell elongation was applied to cultured rabbit synovial membrane cells for 3 to 48 h with or without cycloheximide. HYAL1 and HYAL2 mRNA levels were evaluated by means of real-time polymerase chain reaction (PCR) analysis. HYAL activity in the cell culture was analyzed by means of HA zymography with or without HYAL2-small interfering (si) RNA. Levels of both HYAL1 and HYAL2 mRNA were up-regulated significantly (p < 0.01) by the cyclic tensile load with or without cycloheximide. HYAL activity was detected in the loaded cell cultures and was suppressed substantially by HYAL2-siRNA. HYAL activity was undetectable in unloaded cell cultures. These results show that a cyclic tensile load induces the expression and activity of HYAL in synovial membrane cells, suggesting that increased HYAL by mechanical load affects HA catabolism in synovial fluid.


GM-CSF and IL-4 induce dendritic cell differentiation and disrupt osteoclastogenesis through M-CSF receptor shedding by up-regulation of TNF-{alpha} converting enzyme (TACE)

Monocytes give rise to macrophages, osteoclasts (OCs), and dendritic cells (DCs). M-CSF and RANK ligand induce OC differentiation from monocytes, while GM-CSF and IL-4 trigger monocytic differentiation into DCs. These two differentiation pathways occur in a mutually exclusive manner. However, regulatory mechanisms for the polarization of monocytic differentiation are still unclear. The present study was undertaken to clarify the mechanism of triggering the deflection of OC and DC differentiation from monocytes. GM-CSF and IL-4 abolished monocytic differentiation into OCs while inducing DC differentiation even in the presence of M-CSF and RANK ligand. GM-CSF and IL-4 in combination potently up-regulate TNF-alpha converting enzyme (TACE) expression and activity in monocytes, causing ectodomain shedding of the membrane-bound M-CSF receptor, resulting in the disruption of its phosphorylation by M-CSF as well as the induction of osteoclastogenesis from monocytes by M-CSF and RANK ligand. Interestingly, TACE inhibition robustly causes the resumption of the surface expression of M-CSF receptors on monocytes, which facilitates M-CSF-mediated phosphorylation of M-CSF receptors and macrophage/OC differentiation while impairing GM-CSF and IL-4-mediated DC differentiation from monocytes. These results reveal a novel proteolytic regulation of M-CSF receptor expression in monocytes to control M-CSF signaling and monocytic differentiation into macrophage/OC-lineage cells or DCs.


Blood flow distribution of repaired lip in cleft lip patients.

Abstract Objective: To investigate the blood flow distribution in the repaired lip of cleft patients using a laser Doppler imager and to evaluate the difference in blood flow of the scar tissue between unilateral cleft lip patients with and without cleft palate. Materials and Methods: Twenty patients with either unilateral cleft lip only (CL group, n = 8) or cleft lip and palate (CLP group, n = 12) were used as subjects. The blood flow of the upper lip was two-dimensionally visualized by a color scale alongside the corresponding photo image of the tissue surface with laser Doppler imaging. The upper lip photo image was divided into five regions: scar, white lip on the cleft side, white lip on the noncleft side, red lip on the cleft side, and red lip on the noncleft side. The average flux score (AFS), which is proportional to blood flow, was analyzed in each region. Results: The AFS for the scar region was significantly (P < .05) lower than in the other four regions. The AFS for the red lip on the cleft side was not significantly different from that for the noncleft side. The white lip revealed a significantly (P < .05) higher score on the cleft side than on the noncleft side. The AFS ratio (AFS in the scar region/AFS in the white lip region) was significantly (P < .01) lower in the CLP group than in the CL group. Conclusions: These results suggest that blood flow distribution in the repaired lip might be affected by the anatomic features of the cleft.


Tensile stress patterns predicted in the articular disc of the human temporomandibular joint

The direction of the first principal stress in the articular disc of the temporomandibular joint was predicted with a biomechanical model of the human masticatory system. The results were compared with the orientation of its collagen fibers. Furthermore, the effect of an active pull of the superior lateral pterygoid muscle, which is directly attached to the articular disc, was studied. It was hypothesized that the markedly antero-posterior direction of the collagen fibers would be reflected in the direction of the tensile stresses in the disc and that active pull of the superior lateral pterygoid muscle would augment these tensions. It was found that the tensile patterns were extremely dependent on the stage of movement and on the mandibular position. They differed between the superior and inferior layers of the disc. The hypothesis could only be confirmed for the anterior and middle portions of the disc. The predicted tensile principal stresses in the posterior part of the disc alternated between antero-posterior and medio-lateral directions.


Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition

Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410-450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly involved in low-amplitude activities and that the amount of type IIX fibers is positively related to the generation of large muscle forces, validating our hypothesis.


過去10年間に徳島大学病院矯正歯科を受診した顎顔面骨骨折患者の実態調査

過去10年間に徳島大学病院矯正歯科を受診した顎顔面骨骨折患者の実態調査

The Journal of Chu-Shikoku Orthodontic Society

中·四国矯正歯科学会雑誌


ミニスクリュー固定を用いて上顎歯列の遠心移動を行ったアングルⅡ級2類過蓋咬合症例

中·四国矯正歯科学会雑誌


PLLAスクリュー固定による下顎枝矢状分割術を施行した骨格性下顎前突症の一症例-長期観察例-

中·四国矯正歯科学会雑誌


Effects of hyaluronan oligosaccharide on the expression of MMP-1 in periodontal ligament cells

It is well known that low-molecular weight hyaluronan (HA) is detected in human periodontal tissue under inflammatory conditions. HA oligosaccharide (HAoligo) has been demonstrated to induce matrix metalloproteinase (MMP)-1 expression in dendritic cells and chondrocytes, however, the bioactivities of HAoligo in periodontal ligament (PDL) cells remain unclear. In this study, we investigated the effect of HAoligo on MMP-1 expression in human PDL (HPDL) cells and the mechanisms in terms of the signal transmission. HAoligo was generated and purified from commercial human umbilical cord HA. HPDL cells were isolated from healthy ligaments, and cultured with HAoligo for 0-24h. The expression of MMP-1, tissue inhibitor of MMPs (TIMP)-1 and TIMP-2 was analyzed by real-time PCR and Western blot analyses. Effects of specific inhibitors of p38 mitogen-activated protein kinase (MAPK) activity, MAPK kinase activity and NFkB activity on HAoligo-induced MMP-1 expression in HPDL cells were also investigated by real-time PCR and Western blot analyses. HAoligo remarkably enhanced MMP-1 expression in both mRNA and protein levels, but no effect was shown on the expression of TIMP-1 and TIMP-2 mRNAs. Inhibition of p38MAPK activity decreased the MMP-1 expression. Neither inhibition of NFkB nor MAPKK activity affected the MMP-1 expression. It was suggested that HAoligo induces MMP-1 expression in HPDL cells, and p38MAPK plays a crucial role in signal transduction for MMP-1 inducted by HAoligo


Effects of increased occlusal vertical dimension on daily activity and myosin heavy chain composition in rat jaw muscle

Mammalian skeletal muscles change their contractile-protein phenotype in response to mechanical loading and/or chronic electrical stimulation, implying that the phenotypic changes in masticatory muscles might result from new masticatory-loading conditions. To analyze the effects of increased occlusal vertical dimension (OVD) on daily activities and fibre-type compositions in jaw muscles, we measured the total duration of daily activity (duty time) and the myosin heavy chain (MyHC) compositions in the masseter and digastric muscles of freely moving control and bite-opened rats. In the control state, the duty time of the digastric muscle was higher than that of the masseter muscle at activity levels exceeding 5 and 20% of the day's peak activity. The opposite was true at activity levels exceeding 50 and 80% of the day's peak activity. The MyHCs consisted of a mixture of fast and slow types in the digastric muscle. The masseter consisted of mostly fast-type MyHC. The increment of OVD increased not only the duty time at activity levels exceeding 5, 20, 50 and 80% of the day' peak activity in both muscles but also the proportion of MyHC IIa in the masseter muscle and MyHC I in the digastric muscle at the expense of that of MyHC IIb. These results suggest that the increment of OVD changes masseter and digastric muscles towards slower phenotypes by an increase in their daily activities.


Acceleration of palatal wound healing in Smad3-deficient mice

Wound healing is a well-orchestrated complex process leading to the repair of injured tissues. It is suggested that transforming growth factor (TGF)-beta/Smad3 signaling is involved in wound healing. The purpose of this study was to investigate the role of TGF-beta/Smad3 signaling in palatal wound healing in Smad3-deficient (Smad3(-/-)) mice. Histological examination showed that wound closure was accelerated by the proliferation of epithelium and dermal cells in Smad3(-/-) mice compared with wild-type (WT) mice. Macrophage/monocyte infiltration at wounded regions in Smad3(-/-) mice was decreased in parallel with the diminished production of TGF-beta1, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1alpha compared with WT mice. Fibrocytes, expressing hematopoietic surface marker and fibroblast products, were recruited and produced alpha-smooth-muscle actin in WT mice, but were not observed in Smad3(-/-) mice. These results suggest that TGF-beta/Smad3 signaling may play an important role in the regulation of palatal wound healing.


Stress analysis in the mandibular condyle during prolonged clenching: a theoretical approach with the finite element method.

Parafunctional habits, such as bruxism and prolonged clenching, have been associated with functional overloading in the temporomandibular joint (TMJ), which may result in internal derangement and osteoarthrosis of the TMJ. In this study, the distributions of stress on the mandibular condylar surface during prolonged clenching were examined with TMJ mathematical models. Finite element models were developed on the basis of magnetic resonance images from two subjects with or without anterior disc displacement of the TMJ. Masticatory muscle forces were used as a loading condition for stress analysis during a 10 min clenching. In the asymptomatic model, the stress values in the anterior area (0.100 MPa) and lateral area (0.074 MPa) were relatively high among the five areas at 10 min. In the middle and posterior areas, stress relaxation occurred during the first 2 min. In contrast, the stress value in the lateral area was markedly lower (0.020 MPa) than in other areas in the symptomatic model at 10 min. The largest stress (0.050 MPa) was located in the posterior area. All except the anterior area revealed an increase in stress during the first 2 min. The present result indicates that the displacement of the disc could affect the stress distribution on the condylar articular surface during prolonged clenching, especially in the posterior area, probably leading to the cartilage breakdown on the condylar articular surface.

Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine


Enamel bonding of self-etching and phosphoric acid-etching orthodontic adhesives in simulated clinical conditions: Debonding force and enamel surface

This study aimed to evaluate the effectiveness of self-etching and phosphoric acid-etching orthodontic adhesives for enamel bonding in simulated clinical conditions. By using two self-etching (Transbond Plus, TP; Beauty Ortho Bond, BB) and two acid-etching (Transbond XT, TX; Superbond Orthomite, SB) adhesives, orthodontic brackets were bonded on human premolars (n=10 for each adhesive). Ten teeth without bracket bonding, i.e., intact enamel surfaces, were used as control for SEM observation. After 7-day storage in lactic acid solution, bracket debonding force by means of debonding pliers, adhesive remnant index (ARI), and enamel surface morphology were examined. All the tested adhesives exhibited sufficient bond strength for clinical use. The ARI scores were almost the same among the four adhesives. In terms of SEM observation, the enamel surfaces in the control and TP groups showed a slight change after immersion in lactic acid solution, while the BB group showed less change on the enamel surface compared with the TP group. Meanwhile, the two acid-etching adhesives caused considerable demineralization. Taken together, these findings indicated that the action of self-etching systems was evidently more conservative.


The mandibular cartilage metabolism is altered by damaged subchondral bone from traumatic impact loading

Osteoarthritis (OA) in the temporomandibular joint (TMJ) is a degenerative disease caused by excessive external loading. Recently, it was reported that the damage in the mineralized subchondral bone caused by traumatic impact-loading is responsible for the initiation and progression of cartilage degeneration. Thus far, we have hypothesized that cytokines released from damaged subchondral bone from impact-loading affect the cartilage catabolism under pathological conditions. An impactor of 200 gw was dropped onto the top of a porcine mandibular condyle. After organ culture for 2 days, we investigated the association between the subchondral bone and cartilage using histological and biochemical experiments. The impact-loading induced the expression of IL-1beta immunohistochemically and prominently up-regulated IL-1alpha and IL-1beta mRNA levels in subchondral bone. We confirmed a significant decrease in type II collagen and aggrecan mRNA expressions in chondrocytes by co-culture with osteoblasts after impact-loading, and significant increase in mRNA and protein expressions of IL-1beta in subchondral osteoblasts from impact-loaded subchondral bone. The mRNA expressions of type II collagen, aggrecan, and type X collagen in chondrocytes were decreased significantly by the co-culture with osteoblasts pre-treated by IL-1beta, -6, and TNF-alpha. Among them, osteoblasts pre-treated by IL-1beta affected chondrocytes most strongly. It was also shown that IL-1beta-treated osteoblasts enhanced the MMP-1 mRNA level most markedly in chondrocytes among the four cytokines. These results suggest that the TMJ subjected to impact-loading can increase directly IL-1beta synthesis in the subchondral region, subsequently altering the metabolism of adjacent cartilage and may eventually resulting in the onset and progression of TMJ-OA.


Development of a novel cement by conversion of hopeite in set zinc phosphate cement into biocompatible apatite

Synthetic bone cement that has zinc oxide core particles covered with hydroxyapatite (HAP) was developed; that is, the conversion of hopeite, the traditional zinc phosphate cement, into HAP was attempted. Here, hopeite is the final product of the reaction between powders and trituration liquid of the traditional zinc phosphate cement. This cement may have many advantages not only in terms of biological functions but also the setting process of the traditional cement and the mechanical properties of the developed compact if the hopeite can be converted into calcium phosphate (CP). In this study, calcium nitrate solutions of various concentrations were used for the conversion of hopeite crystals into CP. The products after the solution treatment were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR), and scanning electron microscope (SEM) observation. These results indicated that the converted scholzite crystals could be partially detected. Several types of set zinc phosphate cement with different P/L ratios were arranged. The surface products of the set cement after the solution treatment were analyzed by XRD. However, the crystal phase such as hopeite was not detected except for zinc oxide. The set cement, which was treated with the calcium nitrate solution, was immersed in simulated body fluid (SBF). HAP-like crystals on the set cement could be detected for the specimens immersed for 4 weeks. These findings suggested that the binding phase in the set cement could be converted into HAP by immersion in SBF.


口内法LeFort Ⅱ型骨切り術により中顔面の陥凹を改善させた骨格性下顎前突症例


Biomechanical and biochemical characteristics of the mandibular condylar cartilage.

The human masticatory system consists of a mandible which is able to move with respect to the skull at its bilateral temporomandibular joint (TMJ) through contractions of the masticatory muscles. Like other synovial joints, the TMJ is loaded mechanically during function. The articular surface of the mandibular condyle is covered with cartilage that is composed mainly of collagen fibers and proteoglycans. This construction results in a viscoelastic response to loading and enables the cartilage to play an important role as a stress absorber during function. To understand its mechanical functions properly, and to assess its limitations, detailed information about the viscoelastic behavior of the mandibular condylar cartilage is required. The purpose of this paper is to review the fundamental concepts of the biomechanical behavior of the mandibular condylar cartilage. This review consists of four parts. Part 1 is a brief introduction of the structure and function of the mandibular condylar cartilage. In Part 2, the biochemical composition of the mandibular condylar cartilage is summarized. Part 3 explores the biomechanical properties of the mandibular condylar cartilage. Finally, Part 4 relates this behavior to the breakdown mechanism of the mandibular condylar cartilage which is associated with the progression of osteoarthritis in the TMJ.


Analysis of gene expression profiles in human periodontal ligament cells under hypoxia: the protective effect of CC chemokine ligand 2 to oxygen shortage.

Periodontal ligament (PDL) cells appear to play important functional roles in response to mechanical stress. We hypothesized that hypoxia caused by a deformation of blood vessels and the following ischaemia may play a crucial role in differential gene expression in PDL cells affected by mechanical stress. Gene induction in cultured human PDL cells by hypoxia was analyzed using cDNA array, followed by RT-PCR analysis. Eleven hypoxia-responsive genes were found differentially expressed under low-oxygen conditions in PDL cells. Among them, CCR2, CC chemokine ligand 2 (CCL2) receptor was studied in more detail since little information is available on the role of chemokines in adaptive responses of PDL cells under hypoxia. Here we investigate whether CCR2 mediates the signalling to maintain the homeostasis of PDL cells. We found that cell death of PDL cells was induced under hypoxia with down-regulation of CCL2 mRNA expression. However, the exogenous CCL2 prevented PDL cell death under oxygen shortage with the increment of cellular inhibitor of apoptosis (cIAP) mRNA expression. The present study demonstrated substantial effects of hypoxia on gene expression of CCL2 and CCR2 in PDL cells, indicating that mechanical loading accompanied with mild hypoxia allows PDL cells to elicit adaptive responses with up-regulation of CCR2.


Evaluation of esthetic brackets' resistance to torsional forces from the archwire

The aim of this study was to evaluate the resistance to deformation or fracture of esthetic brackets produced by archwire torsion. Six types of maxillary right central incisor brackets were analyzed: traditional ceramic brackets (cer); ceramic brackets reinforced with a stainless steel slot (cer/ss); ceramic brackets reinforced with a gold slot (cer/gold); traditional polycarbonate brackets (poly); polycarbonate brackets reinforced with a stainless steel slot (poly/ss); and polycarbonate brackets reinforced with ceramic fillers and a stainless steel slot (poly/cer/ss). Stainless steel wire segments were used, and the testing instrument (Emic DL 10000, São José do Rio Preto, PR, Brazil) was moved at a rate of 1 inch per minute to generate the wire torsion. The brackets showed deformation or fracture resistance values (gf x mm) in decreasing order as follows: cer/ss (3528.1 +/- 516.6), cer/gold (2858.7 +/- 611.6), cer (2424.0 +/- 352.1), poly/cer/ss (2279.5 +/- 174.5), poly/ss (2142.0 +/- 275.7), and poly (1463.6 +/- 193.3). The cer/ss ceramic brackets showed the greatest statistically significant (P <0.01) values of resistance to fracture, and the poly brackets had the lowest statistically significant (P <0.01) values of resistance to deformation. The cer brackets showed no significant differences (P >0.01) from the cer/gold, the poly/cer/ss, and the poly/ss brackets. This suggested that the stainless steel slot might enhance resistance to deformation or fracture, although gold slots and ceramic fillers are ineffective for reinforcing esthetic brackets.

American Journal of Orthodontics and Dentofacial Orthopedics (AJO-DO)


Regional differences in fiber characteristics in the rat temporalis muscle

The behavioral differences in muscle use are related to the fiber type composition of the muscles among other variables. The aim of this study was to examine the degree of heterogeneity in the fiber type composition in the rat temporalis muscle. The temporalis muscle was taken from 10-week-old Wistar strain male rats (n = 5). Fiber types were classified by immunohistochemical staining according to their myosin heavy chain content. The anterior temporalis revealed an obvious regional difference of the fiber type distribution, whereas the posterior temporalis was homogeneous. The deep anterior temporalis showed a predominant proportion of type IIA fibers and was the only muscle portion displaying slow type fibers (< 10%). The other two muscle portions, the superficial anterior and posterior temporalis, did not differ significantly from each other and contained mainly type IIB fibers. Moreover, the deep anterior temporalis was the only muscle portion showing slow type fibers (< 10%). In the deep portion, type IIX fibers revealed the largest cross-sectional area (1943.1 +/- 613.7 microm(2)), which was significantly (P < 0.01) larger than those of type IIA and I + IIA fibers. The cross-sectional area of type IIB fibers was the largest in the remaining two muscle portions and was significantly (P < 0.01) larger than that of type IIX fibers. In conclusion, temporalis muscle in rats showed an obvious heterogeneity of fiber type composition and fiber cross-sectional area, which suggests multiple functions of this muscle.


An adolescent patient with multiple impacted teeth

Multiple impacted permanent teeth is uncommon and rarely reported in the literature. This article reports the treatment of an adolescent patient with multiple impacted teeth without systemic disease. A 9-year 2-month-old boy complained of a delay of eruption of the first molars. All first molars were unerupted, and the left deciduous second molar was a submerged tooth. The panoramic radiograph showed all permanent teeth except the incisors were unerupted and, especially for the first molars, spontaneous eruption was not expected. His medical history was uneventful. A lingual arch appliance and a segmental arch were placed on the mandibular and maxillary dentitions, respectively, to guide eruption of the impacted first molars. After traction of the first molars, eruption of the impacted lower premolars was induced. Furthermore, at 15 years the impacted mandibular second molars were also positioned properly by use of the lingual arch with auxiliary wires. After achieving traction of the impacted teeth, tooth alignment was initiated using multibracket appliances after the bilateral extraction of the second premolars. After 22 months of treatment with multibracket appliances, an acceptable occlusion was achieved with a Class I molar relationship. After 2 years of retention an acceptable occlusion was maintained without any relapse in the occlusion. Since a delay in the treatment of impacted teeth may induce secondary problems such as root dilacerations and ankylosis, it is highly recommended to perform early treatment of multiple impacted teeth during adolescence.


Biomechanics of the temporomandibular joint


Effects of Ultrasound on the Proliferation and Differentiation of Cementoblast Lineage Cells

Background: The purpose of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on the proliferation and differentiation of cementoblast lineage cells. Methods: An immortalized human periodontal ligament cell line (HPL) showing immature cementoblastic differentiation was used. Cultured HPL cells were subjected to LIPUS exposure (frequency = 1 MHz; pulsed 1:4; intensity = 30 mW/cm(2)) or sham exposure for 15 minutes per day. Expression levels of alkaline phosphatase (ALP), type I collagen (Col-I), runt-related gene 2 (Runx2), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) mRNA were analyzed with real-time polymerase chain reaction analysis. Furthermore, ALP activity, collagen synthesis, and protein level of Runx2 were examined after 6 days of LIPUS exposure. Results: mRNA and protein levels of ALP, Col-I, and Runx2 were significantly increased by LIPUS exposure compared to controls, whereas BSP, OCN, and OPN mRNA expression could not be detected in HPL cells, irrespective of LIPUS exposure. Conclusion: LIPUS enhanced ALP activity, collagen synthesis, and Runx2 expression of HPL cells, which provides important insight into the promotion of early cementoblastic differentiation of immature cementoblasts.


鎖骨頭蓋異骨症を伴う一卵性双生児における口腔顎顔面形態

鎖骨頭蓋異骨症を伴う一卵性双生児における口腔顎顔面形態

The Journal of Chu-Shikoku Orthodontic Society

中·四国矯正歯科学会雑誌


エナメル質形成不全を伴う空隙歯列症例の一治験例

エナメル質形成不全を伴う空隙歯列症例の一治験例

中·四国矯正歯科学会雑誌


A case report of condylar remodeling after orthognathic surgery with a combination of intraoral vertical ramus osteotomy and sagittal split ramus osteotomy

下顎枝垂直骨切り術と下顎枝矢状分割術を併用した外科的矯正治療後に下顎頭のリモデリングを認めた一症例

Journal of the Japanese Society for the Temporomandibular Joint


Modeling of the effect of friction in the temporomandibular joint on displacement of its disc during prolonged clenching

The effect of the frictional coefficient in the temporomandibular joint on the disc during prolonged clenching was examined. For this purpose, a finite element model of the temporomandibular joint based on magnetic resonance images from a volunteer subject was used. Muscle forces applied for clenching were used as a loading condition for stress analysis during 10 minutes. With respect to the frictional coefficient between articular surfaces, 3 different values ranging from micro = 0.001 to micro = 0.1 were established. At the onset of clenching, large stresses were found in the central and lateral part of the intermediate zone in the disc, and its stress distribution was not markedly changed during 10 minutes of clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 minutes of clenching. When the frictional coefficient between articular surfaces increased, the anterior, lateral, and central points in the disc moved further forward. At the end of 10 minutes of clenching, the disc showed a more anterior position as the frictional coefficient increased. This result indicates that increase of the frictional coefficient between the articular surfaces may be a major cause for the onset of the disc displacement.

Journal of Oral and Maxillofacial Surgery


Jaw-muscle activity changes after the induction of osteoarthrosis in the temporomandibular joint by mechanical loading

AIMS: To examine the effect of mechanical loading on the induction of temporomandibular joint osteoarthrosis (TMJ OA). METHODS: Mechanical stress was applied to the rat TMJ by forced jaw opening of 3 hours a day for 5 days. The electromyographic (EMG) activity of the masseter and digastric muscles was continuously monitored by radio-telemetry. It was characterized by the total time each muscle was active (duty time), the number of bursts, and the average burst length. For histologic analysis, rats were sacrificed before, immediately after, and 3 weeks after the period of forced jaw opening. RESULTS: The condylar cartilage revealed OA-like lesions with a decrease in the number of chondrocytes immediately after forced jaw opening. Three weeks later, the OA-like lesions were repaired to some extent. After the forced jaw opening, the duty time of the masseter increased, whereas the duty time of the digastric decreased significantly (P < .01) at the 5% activity level. Three weeks later, the masseter duty time had decreased and the digastric duty time had slightly increased, returning to the levels observed before forced jaw opening. CONCLUSION: These results suggest that mechanical overloading of the TMJ induced OA-like lesions with a simultaneous influence on jaw muscle activity, especially at the low activity level. This might imply that muscle activity adapted to reduce the effects of (forced) joint overloading.


The effect of mechanical loading on the metabolism of growth plate chondrocytes

It is well known that mechanical loading influences the endochondral bone formation essential for the growth and development of longitudinal bones. The question was, however, asked whether the effect of mechanical loading on the chondrocyte metabolism is dependent on the loading frequency. This study was aimed at evaluating the effect of tensile loadings with various frequencies on the proliferation of growth plate chondrocytes and extracellular matrix synthesis. The chondrocytes obtained from rib growth plate cartilage of 4-week-old male Wistar strain rats were cultured by day 4 and day 11 and used as proliferating and matrix-forming chondrocytes, respectively. Intermittent tensile stresses with different frequencies were applied to each stage chondrocyte. DNA syntheses were examined by measuring the incorporation of [(3)H]thymidine into the cells. Furthermore, the rates of collagen and proteoglycan syntheses were determined by measuring the incorporation of [2,3-(3)H]proline and [(35)S]sulfate into the cells, respectively. At the proliferating stage, intermittent tensions with the frequencies of 30 cycles/min and 150 cycles/min significantly (p < 0.05) upregulated the syntheses of DNA, which indicates the promotion of chondrocyte proliferation. At the matrix-forming stage, collagen, and proteoglycan syntheses also enhanced with increase of the loading frequency. In particular, the intermittent tension with the frequencies of 30 cycles/min and 150 cycles/min increased significantly (p < 0.05 or p < 0.01) both the collagen and proteoglycan syntheses. These results suggest that the proliferation and differentiation of growth plate chondrocytes are regulated by the mechanical loading and that the chondrocyte metabolism enhanced with increase of loading frequency. These may give more insight into the possible mechanism leading to endochondral bone formation.


Expression and activity of Runx2 mediated by hyaluronan during chondrocyte differentiation

During endochondral ossification, the production of hyaluronan (HA) is strictly and selectively regulated by chondrocytes, with a temporal peak at the hypertrophic stage. This study was conducted to clarify the effects of HA on expression and activity of runt-related gene 2 (Runx2), a potent transcription factor for chondrocyte differentiation in hypertrophic chondrocytes. Immature chondrocytes from an ATDC5 cell line were cultured and differentiated in DMEM/Ham's F12 with pre-defined supplements. Using real-time PCR, the gene expressions of type II collagen, MMP-13, HAS2, and Runx2 in cultured chondrocytes were analysed from days 0 to 18 of cell differentiation. The activity and expression of Runx2 in hypertrophic chondrocytes were analysed after the treatment with HA oligosaccharide (HAoligo) using AML-3/Runx2 binding, real-time PCR and Western blot analysis. The effects of pre-incubation of anti-CD44 antibody on Runx2 expression were also examined. Expression of type X collagen and Runx2 mRNAs reached a maximum at the terminal differentiation of chondrocytes. The activity and expression of Runx2 was significantly inhibited in hypertrophic chondrocytes treated with HAoligo compared to the untreated controls. High molecular weight-HA did not affect the expression or activity of Runx2. The expression of Runx2 mRNA was significantly decreased in hypertrophic chondrocytes treated with anti-CD44 antibody. These results suggest that HAoligo may affect the terminal differentiation of chondrocytes during the endochondral ossification by inhibiting the expression and activity of Runx2.


Dynamic shear behavior of mandibular condylar cartilage is dependent on testing direction

Little information is available on the direction-dependency of shear behavior in mandibular condylar cartilage. Therefore, we tested the hypothesis that such a dependency of the dynamic shear properties is present in mandibular condylar cartilage. From each of 17 condyles, two cartilage-bone plugs were dissected and tested in a simple shear sandwich configuration under a compressive strain of 10%. Sinusoidal shear strain (frequency range: 0.01-10 Hz) was applied in the medio-lateral or antero-posterior direction with an amplitude of 1.0%, 2.0%, and 3.0%. The magnitudes of the dynamic shear moduli, as calculated from the resulting shear stress, were found to increase with applied frequency and the shear strain amplitude. The values |G*|, G' and G'' for a medio-laterally applied shear were about 20-33% of those in the antero-posterior shear, although the loss tangent (elasticity/viscosity ratio) was almost the same. In conclusion, the present results clearly show the direction-dependent characteristic of the mandibular condylar cartilage in dynamic shear.


Degenerative disorders of the temporomandibular joint: etiology, diagnosis, and treatment

Temporomandibular joint (TMJ) disorders have complex and sometimes controversial etiologies. Also, under similar circumstances, one person's TMJ may appear to deteriorate, while another's does not. However, once degenerative changes start in the TMJ, this pathology can be crippling, leading to a variety of morphological and functional deformities. Primarily, TMJ disorders have a non-inflammatory origin. The pathological process is characterized by deterioration and abrasion of articular cartilage and local thickening. These changes are accompanied by the superimposition of secondary inflammatory changes. Therefore, appreciating the pathophysiology of the TMJ degenerative disorders is important to an understanding of the etiology, diagnosis, and treatment of internal derangement and osteoarthrosis of the TMJ. The degenerative changes in the TMJ are believed to result from dysfunctional remodeling, due to a decreased host-adaptive capacity of the articulating surfaces and/or functional overloading of the joint that exceeds the normal adaptive capacity. This paper reviews etiologies that involve biomechanical and biochemical factors associated with functional overloading of the joint and the clinical, radiographic, and biochemical findings important in the diagnosis of TMJ-osteoarthrosis. In addition, non-invasive and invasive modalities utilized in TMJ-osteoarthrosis management, and the possibility of tissue engineering, are discussed.


Cementoblast response to low- and high-intensity ultrasound

It has been shown that ultrasound stimulation accelerates repair of orthodontically induced root resorption. However, the mechanism of such adaptive change is still unclear. The purpose of this study was to evaluate pulsed ultrasound on the differentiation-potential and cementoblast-mediated osteoclastogenesis using a cementoblastic cell line. DESIGN: Cultured cementoblasts (murine cementoblastic cell line, OCCM-30) were subjected to ultrasound exposure (frequency = 1 MHz; pulsed 1:4; spatial average temporal average intensities=30 or 150 mW/cm(2)) or sham exposure for 15 min per day. Expression levels of alkaline phosphatase (ALP), type I collagen (COL-I), osteoprotegerin (OPG) and receptor activator of nuclear factor small ka, CyrillicB ligand (RANKL) mRNAs were analysed by a real-time PCR analysis. Furthermore, ALP activity, collagen synthesis, and protein levels of OPG and RANKL were examined after 6-day ultrasound exposure. RESULTS: Real-time PCR analysis indicated that, irrespective of the intensity, single ultrasound exposure increased the expression of transcripts for COL-I and ALP after 24h; the expression of OPG and RANKL also increased after 1 and 4h, respectively. Cultured cementoblasts receiving ultrasound stimulation for 6 days showed a significant (p<0.05 or 0.01) increase in cell number and collagen synthesis. ALP activity and OPG synthesis were also significantly (p<0.05) upregulated by ultrasound stimulation with 150 mW/cm(2). CONCLUSIONS: These results demonstrated that ultrasound stimulation especially with 150 mW/cm(2) might be a better candidate as a medical remedy to protect against root resorption and/or accelerate its repair.


Biomechanical response of condylar cartilage-on-bone to dynamic shear.

Shear stress can result in fatigue, damage, and irreversible deformation of the mandibular condylar cartilage. However, little information is available on its dynamic properties in shear. We tested the hypothesis that the dynamic shear properties of the condylar cartilage depend on the frequency and amplitude of shear strain. Ten porcine mandibular condyles were used for dynamic shear tests. Two cartilage-bone plugs were dissected from each condyle and tested in a simple shear sandwich configuration under a compressive strain of 10%. Sinusoidal shear strain was applied with an amplitude of 1.0, 2.0, and 3.0% and a frequency range between 0.01 and 10 Hz. The magnitudes of the shear dynamic moduli were found to be dependent on the frequency and the shear strain amplitude. They increased with shear strain. tan delta ranged from 0.2 to 0.4, which means that the cartilage is primarily elastic in nature and has a small but not negligible viscosity. In conclusion, the present results show that the shear behavior of the mandibular condylar cartilage is dependent on the frequency and amplitude of the applied shear strain. The observed shear characteristics suggest a significant role of shear strain on the interstitial fluid flow within the cartilage.

Journal of Biomedical Materials Research. Part A


A case of anterior open bite with severely narrowed maxillary dental arch and hypertrophic palatine tonsils

This case report describes an adolescent patient with an open bite and severely narrowed maxillary dentition and hypertrophic palatine tonsils, treated efficiently with rapid maxillary expansion (RME) and subsequent orthodontic tooth alignment using fixed appliances. The treatment demonstrates that RME can be effective for the correction of a severely narrowed maxillary arch, as well as, in this case, the correction of an anterior open bite in an adolescent patient where no substantial vertical skeletal discrepancy existed.


Skeletal anchorage for orthodontic correction of severe maxillary protrusion after previous orthodontic treatment

The correction of a severe maxillary protrusion in an adult by distal movement of the maxillary molars has been one of the most difficult biomechanical problems in orthodontics. This article reports on the treatment of an adult case of severe maxillary protrusion and a large overjet treated with a skeletal anchorage system. A female patient, age 22 years and 3 months, complained of the difficulty of lip closure due to severe maxillary protrusion with a gummy smile. Overjet and overbite were +7.6 mm and -0.9 mm, respectively. She had a history of orthodontic treatment in which her maxillary first premolars were extracted. In order to conduct distal movement of the maxillary molars, anchor plates were placed in the zygomatic process. After achieving a Class I molar relationship, retraction and intrusion of the maxillary incisors were performed. After a 2-year treatment, an acceptable occlusion was achieved with a Class I molar relationship. Her convex facial profile with upper lip protrusion was considerably improved, and the lips showed less tension in lip closure. After a 2-year retention period, an acceptable occlusion was maintained without recurrence of maxillary protrusion, indicating a stability of the occlusion. The result of this treatment indicated that skeletal anchorage is of great importance as a remedy for achieving intrusion and retraction of the maxillary incisors in cases of severe maxillary protrusion with a patient who had previous orthodontic treatment.


Lubrication of the temporomandibular joint

Although tissue engineering of the temporomandibular joint (TMJ) structures is in its infancy, tissue engineering provides the revolutionary possibility for treatment of temporomandibular disorders (TMDs). Recently, several reviews have provided a summary of knowledge of TMJ structure and function at the biochemical, cellular, or mechanical level for tissue engineering of mandibular cartilage, bone and the TMJ disc. As the TMJ enables large relative movements, joint lubrication can be considered of great importance for an understanding of the dynamics of the TMJ. The tribological characteristics of the TMJ are essential for reconstruction and tissue engineering of the joint. The purpose of this review is to provide a summary of advances relevant to the tribological characteristics of the TMJ and to serve as a reference for future research in this field. This review consists of four parts. Part 1 is a brief review of the anatomy and function of the TMJ articular components. In Part 2, the biomechanical and biochemical factors associated with joint lubrication are described: the articular surface topology with microscopic surface roughness and the biomechanical loading during jaw movements. Part 3 includes lubrication theories and possible mechanisms for breakdown of joint lubrication. Finally, in Part 4, the requirement and possibility of tissue engineering for treatment of TMDs with degenerative changes as a future treatment regimen will be discussed in a tribological context.


Identification of key determinant for predicting feasible mandibular molars distalization


顎関節症に対する矯正歯科医の役割

顎関節症に対する矯正歯科医の役割

Journal of the Japanese Society for the Temporomandibular Joint