Astaxanthin inhibits inflammation of human periodontal ligament cells induced by lipopolysaccharide. / è™¾é’ç´ æŠ‘åˆ¶è„‚å¤šç³–è¯±å¯¼äººç‰™å‘¨è†œç»†èƒžç‚Žç—‡ååº”.

OBJECTIVES: Human periodontal ligament cells (hPDLCs) are important source of periodontal tissue reconstruction. Under chronic inflammation, the multi-directional differentiation potential and chemotaxis in hPDLCs are decreased. Therefore, inhibiting inflammatory microenvironment and improving the functional characteristics of stem cells can better promote periodontal tissue reconstruction. This study was to investigate the effect of astaxanthin (AST) on lipopolysaccharide (LPS)-induced inflammation in hPDLCs and the underlying mechanisms. METHODS: hPDLCs were isolated and cultured in vitro, and vimentin and keratin immunocytochemical staining were used to identify hPDLCs. CCK-8 assay was used to measure the effects of AST (1, 5, 10, 20, 50, 100, and 200 µmol/L) on proliferation of hPDLCs. Quantitative RT-PCR (RT-qPCR) and ELISA were used to measure the mRNA and protein expression of inflammatory factors (IL-6, IL-1ß, and TNF-α) in the control (Con) group, the LPS group, and the LPS+AST (5, 10, 20, and 50 µmol/L) group. Western blotting was used to detect the protein expression of IKBα, phosphorylated IKBα (p-IKBα), and p65 in the Con group, the LPS group, the AST (20 µmol/L) group, and the LPS+AST (20 µmol/L) group. After 10 µmol/L PDTC treatment, the mRNA and protein expressions of IL-6, IL-1ß, and TNF-α were detected by RT-qPCR and ELISA. RESULTS: Cell morphology and immunocytochemical staining showed that the cells were in line with the characteristics of hPDLCs. Treatment with AST could promote the proliferation of hPDLCs, which reached the peak at 20 µmol/L. The mRNA and protein expressions of IL-6, IL-1ß, and TNF-α in the LPS group were higher than those in the Con group (all P<0.05). Compared with the LPS group, the mRNA and protein expressions of IL-6, IL-1ß, and TNF-α in the LPS+AST (5, 10, 20, and 50 µmol/L) group were down-regulated (all P<0.05). Compared with the Con group, the levels of IKBα and p65 in cytoplasm of the LPS group were significantly downregulated (both P<0.05), and the levels of p-IKBα in cytoplasm and p65 in nucleus of the LPS group were significantly up-regulated (both P<0.05). Compared with the LPS group, the levels of IKBα and p65 in cytoplasm of the LPS+AST (20 µmol/L) group were significantly upregulated (both P<0.05), and the levels of p-IKBα in cytoplasm and p65 in nucleus of the LPS+AST (20 µmol/L) group were significantly downregulated (both P<0.05). The mRNA and protein expressions of IL-6, IL-1ß, and TNF-α in the LPS+PDTC (10 µmol/L) group were lower than those in the LPS group (all P<0.05). CONCLUSIONS: AST promotes the proliferation of hPDLCs, which is related to suppression of LPS-induced the secretion of inflammatory factors via inhibiting the activation of NF-κB signaling pathway.

Effectiveness of orthodontic temporary anchorage devices in canine retraction and anchorage preservation during the two-step technique: a systematic review and meta-analysis.

BACKGROUND: Temporary anchorage devices have been used for decades in orthodontic practice for many applications. The aim of this systematic review was to assess the effectiveness of orthodontic temporary anchorage devices in canine retraction during the two-step technique. METHODS: A search was systematically performed for articles published prior to June 30, 2019 in five electronic databases (PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Scopus). The risk of bias was assessed using the Cochrane risk of bias tool for randomized controlled trials (RCTs) and the risk of bias in nonrandomized studies of interventions (ROBINS-I) tool for controlled clinical trials (CCTs). The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) approach was used for the quality assessment. Data concerning the mean difference in mesial molar movement and extent of canine retraction were extracted for statistical analysis. The mean differences and 95% confidence intervals were analyzed for continuous data. A meta-analysis with a random-effects model for comparable outcomes was carried out. RESULTS: Three RCTs and five CCTs were finally included. Meta-analysis showed a significant increase not only in anchorage preservation in the implant anchorage group in both the maxilla (1.56 mm, 95% CI: 1.14 to 1.98, P < 0.00001) and the mandible (1.62 mm, 95% CI: 1.24 to 2.01, P < 0.00001) but also in canine retraction in the implant anchorage group in both the maxilla (0.43 mm, 95% CI: 0.16 to 0.69, P = 0.001) and the mandible (0.26 mm, 95% CI: 0.02 to 0.49, P = 0.03). CONCLUSIONS: There is very low-quality evidence showing that implant anchorage is more efficient than conventional anchorage during canine retraction. Additional high-quality studies are needed.

Antibiotic tigecycline inhibits cell proliferation, migration and invasion via down-regulating CCNE2 in pancreatic ductal adenocarcinoma.

Recently, many researches have reported that antibiotic tigecycline has significant effect on cancer treatment. However, biomedical functions and molecular mechanisms of tigecycline in human pancreatic ductal adenocarcinoma (PDAC) remain unclear. In the current study, we tried to assess the effect of tigecycline in PDAC cells. AsPC-1 and HPAC cells were treated with indicated concentrations of tigecycline for indicated time, and then, MTT, BrdU and soft agar assay were used to test cell proliferation. The effect of tigecycline on cell cycle and cellular apoptosis was tested by cytometry. Migration and invasion were detected by wound healing assay and transwell migration/invasion assay. Expressions of cell cycle-related and migration/invasion-related protein were determined by using Western blot. The results revealed that tigecycline observably suppressed cell proliferation by inducing cell cycle arrest at G0/G1 phase and blocked cell migration/invasion via holding back the epithelial-mesenchymal transition (EMT) process in PDAC. In addition, tigecycline also remarkably blocked tumorigenecity in vivo. Furthermore, the effects of tigecycline alone or combined with gemcitabine in vitro or on PDAC xenografts were also performed. The results showed that tigecycline enhanced the chemosensitivity of PDAC cells to gemcitabine. Interestingly, we found CCNE2 expression was declined distinctly after tigecycline treatment. Then, CCNE2 was overexpressed to rescue tigecycline-induced effect. The results showed that CCNE2 overexpression significantly rescued tigecycline-inhibited cell proliferation and migration/invasion. Collectively, we showed that tigecycline inhibits cell proliferation, migration and invasion via down-regulating CCNE2, and tigecycline might be used as a potential drug for PDAC treatment alone or combined with gemcitabine.

Prevalence of malocclusion in Chinese schoolchildren from 1991 to 2018: A systematic review and meta-analysis.

BACKGROUND: Malocclusion is a common oral health problem in schoolchildren. Literature describing the prevalence of malocclusion varies substantially across China. AIM: This study identified the epidemiological characteristics of malocclusion among Chinese schoolchildren from 1991 to 2018. DESIGN: Six English and Chinese electronic databases were searched through November 2018. The search was supplemented by hand searching to identify relevant surveys. The overall prevalence of malocclusion was estimated by a random-effects meta-analysis model, and variations in different groups were assessed by subgroup meta-analysis. RESULTS: Thirty-seven eligible articles describing 117 682 samples were investigated. The pooled national prevalence for malocclusion was 47.92% (95% CI: 58.6%-71.9%). For the Angle classification, the overall prevalence rates were 30.07% (95% CI: 25.37%-35.48%), 9.91% (95% CI: 7.41%-13.79%), and 4.76% (95% CI: 3.85%-6.54%) for Class I, Class II, and Class III malocclusion, respectively. A deep overbite (16.67%, 95% CI: 11.50%-23.08%) was shown to be the most common trait of malocclusion. When stratified by sex, males had a slightly higher prevalence than females (RR = 1.04, 95% CI: 1.01-1.06). More importantly, an ascending trend and substantial variations across the country were observed. CONCLUSIONS: Our results confirmed that malocclusion has become a serious oral health problem in Chinese schoolchildren, highlighting the need for proactive interventions at an early age. Moreover, high-quality epidemiological studies on malocclusion are still required.

Nano-hydroxyapatite mineralized silk fibroin porous scaffold for tooth extraction site preservation.

OBJECTIVE: To fabricate a novel nano-hydroxyapatite mineralized silk fibroin (MSF) scaffold in order to diminish the resorption of alveolar ridge and accelerate new bone formation within tooth sockets. Also, to investigate the biocompatibility and osteogenic ability of the MSF in vitro, and the effect of site preservation of the MSF graft in post-extractive sockets in vivo. METHODS: SEM, EDX, FTIR and XRD were used to analyze the mineral crystals deposited on the silk fibroin (SF) surface. Pre-osteoblasts (MC3T3-E1) were seeded on SF and MSF scaffolds. Cell viability, distribution and differentiation were examined using a live-dead assay, histological analysis and Alizarin Red S staining. Furthermore, prepared grafts (SF or MSF scaffold) were implanted into the maxillary right first molar sockets of Sprague Dawley rats for 6 weeks and newly formed bone tissue was analyzed by micro-CT and histological examination. RESULTS: The SEM, EDX, FTIR and XRD analysis demonstrated that granulate nano-hydroxyapatite (nHA) crystals were uniformly distributed on the SF scaffold. In addition, the MSF hydrophilicity measured by water contact angle and swelling ratio was superior to plain SF scaffold. The effect of nHA inorganic crystals on osteogenic differentiation of MC3T3-E1 cells indicated the MSF scaffolds improved osteogenesis. Furthermore, MSF grafts induced more bone formation and reduced the height of alveolar bone resorption after tooth extraction. SIGNIFICANCE: The MSF scaffold partially simulated the structure and composition of natural bone matrix. It induced osteogenic differentiation of MC3T3-E1 cells in vitro, and also promoted new bone regeneration in tooth extraction sockets in vivo, indicating it is a biomaterial with great potential for tooth extraction site preservation.

[Comparative study of alveolar bone remodeling around the upper incisor area after Twin-block and high-pull headgear-activator functional orthopedic therapy].

PURPOSE: The aim of this clinical study was to evaluate the changes of alveolar bone morphology around the upper incisors before and after functional treatment in adolescents using cone-beam CT(CBCT). METHODS: Thirty patients with skeletal Class II mandibular retrusion who were successfully treated with high-pull headgear-activator(HGAC) and Twin-block were selected and divided into 2 groups (HGAC and Twin-block groups), 15 in each group. CBCT was performed before and after treatment, to observe upper incisor movement in the alveolar bone and alveolar bone remodeling. Statistical analysis was performed using SPSS 20.0 software package to analyze the changes of alveolar bone thickness, angle of central incisor and alveolar bone before and after treatment. RESULTS: Horizontally, the edge of the maxillary incisor appeared lingual movement in both groups, while the root apex appeared lingual movement in HGAC group and labial movement in Twin-block group. Vertically, the edge of the maxillary incisor was moved down and the root apex was moved up in all patients, whereas the moving distance was less in the edge and larger in the root apex in HGAC group. The thicknesses of major areas in the alveolar bone significantly increased in HGAC group, while in Twin-block group the labial thickness of the alveolar bone showed significant decrease and the palatal thickness showed significant increase. Moreover, the total thickness of the alveolar bone showed significant increase in both groups, yet Twin-block group showed more increase, and the angle of the alveolar bone showed more decrease in HGAC group. CONCLUSIONS: Both functional appliances can cause positive alveolar bone remodeling in maxillary incisor area. HGAC can achieve a controlled tilt inward movement of the maxillary incisors, intrude the incisors to a certain extent, and allow certain change in the bending angle of the incisor alveolar bone at the same time, which is conducive to improving ClassⅡcraniofacial pattern. Twin-block can tilt the maxillary incisor inward, suggesting that more attention needs to be paid to the control of the torque of the incisor when retracting anterior teeth in fixed orthodontic treatment after Twin-block functional treatment.

Prevalence of temporomandibular disorders and its clinical signs in Chinese students, 1979-2017: A systematic review and meta-analysis.

OBJECTIVE: This study intends to assess the prevalence of temporomandibular disorders and its clinical signs in Chinese students. MATERIALS AND METHODS: Search strategies were performed in seven electronic databases, and the reference lists from potentially relevant studies were searched manually. Only observational studies that met the eligibility criteria were selected. A validated instrument was used to evaluate the quality of the included studies. A random-effects model was used to calculate the pooled prevalence of temporomandibular disorders and its clinical signs. RESULTS: Twenty-three articles that met the eligibility criteria were included in this review and meta-analysis. The prevalence of temporomandibular disorders was 29.1% (95% confidence interval [CI], 23.7-35.1; n = 12,702), and a significant difference was observed between males and females. The most prevalent sign was temporomandibular joint sounds (17.4%; 95% CI, 13.8-20.6; n = 6,615) followed by abnormal jaw movement (12.3%; 95% CI, 9.1-16.7; n = 5,496) and pain (9.9%; 95% CI, 7.4-13; n = 4,552). CONCLUSIONS: The overall prevalence of temporomandibular disorders in Chinese students was approximately 29.1%, and a statistically significant difference was observed between males and females. The most prevalent sign was temporomandibular joint sounds (17.4%), followed by abnormal jaw movement (12.3%) and pain (9.9%).

Associations Between MTR A2756G, MTRR A66G, and TCN2 C776G Polymorphisms and Risk of Nonsyndromic Cleft Lip With or Without Cleft Palate: A Meta-Analysis.

OBJECTIVE: We conducted a meta-analysis to investigate the associations of methionine synthase (MTR) A2756G, methionine synthase reductase (MTRR) A66G, and transcobalamin 2 (TCN2) C776G gene polymorphisms with nonsyndromic cleft lip with or without cleft palate (NSCL/P). MATERIALS AND METHODS: The PubMed, Web of Science, Embase, and Wiley Online Library databases and the China Biomedical Literature Service System (SinoMed) were searched for relevant articles to explore the associations between the MTR A2756G, MTRR A66G, and TCN2 C776G polymorphisms and the risk of NSCL/P. We performed overall comparisons and stratified analyses according to the ethnicity, type of NSCL/P, and Hardy-Weinberg equilibrium (HWE) of the control group. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were applied to estimate the associations of these gene polymorphisms with NSCL/P risk using fixed-effects or random-effects models incorporating five genetic models. RESULTS: Ultimately, 12 articles were included in this study. The pooled results did not reveal a significant association of the MTR A2756G polymorphism with NSCL/P risk (G vs. A: OR = 0.95, 95% CI = 0.82-1.11, p = 0.55). Similar results were observed for the MTRR A66G polymorphism (G vs. A: OR = 0.99, 95% CI = 0.82-1.18, p = 0.72) and the TCN2 C776G polymorphism (G vs. C: OR = 0.95, 95% CI = 0.86-1.06, p = 0.37). CONCLUSION: In summary, the MTR A2756G, MTRR A66G, and TCN2 C776G polymorphisms might not be associated with NSCL/P risk.

The effect of tubeimoside-1 on the proliferation, metastasis and apoptosis of oral squamous cell carcinoma in vitro.

BACKGROUND: Tubeimoside-1 (TBMS1), a triterpenoid saponin extracted from traditional Chinese medicine tubeimoside, exerts a cytotoxic effect on several human cancer cell lines. However, no study has focused on whether TBMS1 works on oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: We treated OSCC cells with TBMS1 to detect the effect and relevant molecular basis of TBMS1 for the first time. We chose two oral cancer cell lines, CAL27 and SCC15, for this study. First, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide assay and cell proliferation 5'-bromo-2'-deoxyuridine assay were carried out to detect cell growth. Second, colony formation assay was performed to assess clonogenesis capacity. Next apoptosis was analyzed by flow cytometry. Subsequently, wound healing and transwell assays were applied to explore cell migration. Finally, Western blot was further performed to examine corresponding proteins' expression change. RESULTS: Our data showed that TBMS1 significantly suppressed proliferation of OSCC cells in a dose- and time-dependent manner and it inhibited migration of OSCC cells as well. After treatment with TBMS1, OSCC cells underwent cell apoptosis. Furthermore, Western blot demonstrated that TBMS1 downregulated apoptosis-associated proteins such as PARP, p-ERK1/2, Bcl-2, caspase-3, caspase-7 and caspase-8 and upregulated cleaved PARP, cleaved caspase-3 and cleaved caspase-9. It could also reduce expression of c-Myc and MMP-7. Meanwhile, TBMS1 did not change the total ERK1/2 expression. CONCLUSION: These results revealed that TBMS1 might be a potential chemotherapeutic drug for the management of OSCC.

Leflunomide inhibits proliferation and tumorigenesis of oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) is the most prevalent pathological cancer occurring in the head and neck area. Progress has previously been made regarding treatment strategies of OSCC, however the 5­year survival rate of these patients is only 50%. The present study examined if leflunomide (LEF), a drug primarily used for the treatment of rheumatoid arthritis, exhibited antitumor effects in OSCC. The results demonstrated that LEF inhibited cell proliferation and blocked the cell cycle at the S phase in OSCC cells, with upregulation of cyclin A protein expression. LEF reduced the expression of dihydroorotate dehydrogenase, which is an essential enzyme in the de novo pyrimidine biosynthetic pathway. LEF additionally inhibited colony formation in soft agar and reduced tumor growth in a xenograft model. The results suggested that LEF may act as a potential therapeutic agent in the treatment of OSCC in the future.

Epigenetic Regulation of Osteogenic Differentiation of Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are multipotent progenitors that have the abilities of self-renewal and multiple direction differentiation. The osteogenic potential of MSCs holds great promise for bone defect repair and bone disease treatment. For a long time studies about osteogenic differentiation of MSCs have emphasized on the effect of extrinsic regulators and the corresponding transcription factors controlling cell fate. In fact, cell fate is determined by lineage specific gene expression that is regulated more specifically by epigenetic mechanism. Over the last decade, some progress has been made in epigenetic researches of MSCs osteogenic differentiation. DNA methylation, histone modifications and microRNA (miRNA) are all verified important mechanisms regulating MSCs differentiation. Epigenetic regulation might provide novel treatment targets for promoting bone formation. In this review, we will summarize the recent advance about the epigenetic mechanism that control MSCs commitment to osteoblasts and the potential clinical application of MSCs epigenetics in future.

Effects of TGF-ß1 on OPG/RANKL expression of cementoblasts and osteoblasts are similar without stress but different with mechanical compressive stress.

INTRODUCTION: This study aimed to explore the effects of TGF-ß1 on regulating activities of cementoblasts and osteoblasts with or without stress. MATERIAL AND METHODS: Human recombinant TGF-ß1 was added with different doses. Immunohistochemical test of osteoprotegerin (OPG)/receptor activator of nuclear factor-kappaB ligand (RANKL) and Alizarin Red-S staining were conducted. Mechanical compressive stress was obtained by increasing the pressure of gaseous phase. OPG/RANKL expression was detected in both cells through quantitative real-time PCR. RESULTS: Similar significant differences (P < 0.05) existed in OPG/RANKL change with increasing concentration of TGF-ß1 without mechanical stress for cementoblasts and osteoblasts. However, under 3 h stress, OPG increased and RANKL decreased significantly (P < 0.01) but with similar OPG/RANKL change. Moreover, under 24 h stress, OPG change exhibited no difference (P > 0.05), but RANKL decreased significantly (P < 0.01) at 10 and 100 ng/mL TGF-ß1 in cementoblasts. In osteoblasts, OPG increased significantly (P < 0.01) at 10 and 100 ng/mL, whereas RANKL decreased with statistical difference (P < 0.05) at 1 and 10 ng/mL. CONCLUSIONS: The effects of TGF-ß1 on OPG/RANKL expression of cementoblasts and osteoblasts are similar even without mechanical stress. However, these effects are different under mechanical compressive stress.

Inhibition of H3K9 methyltransferase G9a induces autophagy and apoptosis in oral squamous cell carcinoma.

OBJECTIVE: To explore whether inhibition of H3K9 Methyltransferase G9a could exert an antitumoral effect in oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: First we checked G9a expression in two OSCC cell lines Tca8113 and KB. Next we used a special G9a inhibitor BIX01294 (BIX) to explore the effect of inhibition of G9a on OSCC in vitro. Cell growth was tested by typlan blue staining, MTT assay and Brdu immunofluorescence staining. Cell autophagy was examined by monodansylcadaverine (MDC) staining, LC3-II immunofluorescence staining and LC3-II western blot assay. Cell apoptosis was checked by FITC Annexin-V and PI labeling, tunnel staining and caspase 3 western blot assay. Finally, the effect of inhibition of G9a on clonogenesis and tumorigenesis capacity of OSCC was analyzed by soft agar growth and xenograft model. RESULTS: Here we showed that G9a was expressed in both Tca8113 and KB cells. Inhibition of G9a using BIX significantly reduced cell growth and proliferation in Tca8113 and KB. Inhibition of G9a induced cell autophagy with conversion of LC3-I to LC3-II and cell apoptosis with the expression of cleaved caspase 3. We also found that inhibition of G9a reduced colony formation in soft agar and repressed tumor growth in mouse xenograph model. CONCLUSION: Our results suggested that G9a might be a potential epigenetic target for OSCC treatment.

The effects of mesenchymal stem cells in craniofacial tissue engineering.

Due to the ability to differentiate into numerous cell types, multipotent mesenchymal stem cells (MSCs) are currently researched widely including in the field of craniofacial tissues engineering where always requires a wide variety of cell types and tissues while complete surgical reconstruction of craniofacial tissues is always difficult to achieve based on conventional therapies due to such high complexity. Nowadays, numerous animal model studies have been reported on the effect of MSCs in craniofacial tissue engineering including bone, tendon, cartilage, cutaneous wound and vascularization repair etc. Several clinical trials also have been reported with inspiring results. In this review, we will summarize the recent progress of MSCs in craniofacial tissue engineering and the potential clinical application in future.

Expression of osteoprotegerin and receptor activator of nuclear factor κB ligand in root resorption induced by heavy force in rats.

OBJECTIVE: The aim of this study was to investigate the expression patterns of osteoprotegerin (OPG) and the receptor activator of nuclear factor κB ligand (RANKL) in root resorption during orthodontic tooth movement. MATERIAL AND METHODS: Forty 12-week-old male SD rats were used with the right maxillary side as the experimental group and the left maxillary side as the control group. After 1 N (100g) force was loaded on the right maxillary first molar, the rats were sacrificed on days 0, 1, 4, 8, and 12. Mesial root resorption of the first molar, the number of odontoclasts and osteoclasts, and OPG and RANKL mRNA expression were determined by hematoxylin-eosin and scanning electron microscopy, tartrate-resistant acid phosphate staining, and in situ hybridization, respectively. RESULTS: Serious root resorption was apparent on the pressure side of the mesial root of the right maxillary first molar on days 8 and 12. The number of odontoclasts in the cementum lacuna was elevated on days 8 and 12. OPG expression rose significantly on the tensile side, while RANKL expression increased on the pressure side. The mRNA level of RANKL was significantly elevated on days 4, 8, and 12. Moreover, the RANKL/OPG mRNA ratio was increased on the pressure side, but decreased on the tensile side. CONCLUSION: Changes in the expression of RANKL mRNA and the RANKL/OPG mRNA ratio are accompanied by a parallel alteration in the number of odontoclasts and tooth resorption, suggesting crucial involvement of RANKL and OPG in tooth resorption.

The three-dimension finite element analysis of stress in posterior tooth residual root restored with postcore crown.

OBJECTIVE: Teeth that have been endodontically treated and restored with postcore crown may experience fracture sometimes. Some researchers have analyzed the stress of the anterior teeth after postcore crown restoration, but the stress of the posterior teeth after such restoration has not been reported. We used three-dimension finite element methods to analyze the stress magnitude and distribution of remaining dentin in posterior tooth residual root restored with postcore crown. The binding material, loading direction, number, length and material of posts were studied. METHODS: The models of residual root of maxillary first molar restored with postcore crown were created by CT scanning, mimics software and abaqus software. Different number, length and material of posts were used in the modeling. The posts were cemented with zinc-phosphate cement or composited resin. A load of 240 N was applied to the occlusal surface in four directions and tensile, shear, and von Mises stresses were calculated. RESULT: (i) The maximum stress on remaining dentin changed irregularly as the number and length of posts changed. (ii) The maximum stress on remaining dentin decreased slightly as elastic modulus of the material of posts increased. (iii) The maximum stress on bonding layer and remaining dentin was lower when bonded with resin luting agent than with zinc-phosphate cement. (iv) The maximum stress on remaining dentin increased markedly as loading angle increased. CONCLUSION: The number, length, material of posts, bonding material and loading angle all have influence on the magnitude and distribution of stress. The influence of loading angle is most apparent.

[The three-dimension finite element analysis of stress in posterior residual root restored with different designed post-core crown].

OBJECTIVE: To analyze the stress magnitude and distribution of remaining dentin in posterior residual root restored with post-core crown by three-dimension finite element methods. The variables were number, length and material of post. METHODS: The models of residual root of maxillary first molar restored with post-core crown were created by CT scanning, Mimics software and Abaqus software. Different number, length and material of posts were used in the modeling. The post was cemented with zinc-phosphate cement. A load of 240 N was applied to the occlusal surface in vertical direction and tensile, shear, and Von mises stresses were calculated. RESULTS: The maximum stresses on remaining dentin changed irregularly as the number and length of post. The maximum stresses on remaining dentin decreased slightly as elastic modulus of the material of post increase. CONCLUSION: The number, length, material of post have influence on magnitude and distribution of stress.

Mechanical tensile stress effects on the expression of bone sialoprotein in bovine cementoblasts.

OBJECTIVE: To develop a new cementoblast culture method and to detect bone sialoprotein (BSP) expression in response to high and low mechanical tensile stress in cementoblast in vitro. MATERIALS AND METHODS: Cementoblasts were collected from the roots of newborn bovine teeth and were identified with cementum-derived attachment protein (CAP) antibody 3G9. Cell proliferation was evaluated by MTT [3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, and mineralization was confirmed by von Kossa staining. Mechanical tensile stress was applied in vitro to the cementoblast with the use of a uniaxial four-point bending system with 2000 or 4000 microstrains, at a frequency of 0.5 Hz for 3, 6, 12, 24, or 36 hours. BSP mRNA level was quantified by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). RESULTS: A large amount of cementoblast was observed to be expressing CAP. Cementoblasts had a proliferation tendency similar to that of osteoblasts but different from that of periodontal ligament (PDL) cells. Cementoblasts had the ability to become mineralized between osteoblasts and PDL cells. The mechanical tensile stress significantly up-regulated BSP mRNA expression, which reached a peak at 24 hours in both 2000 and 4000 microstrain groups (P < .01) and was tenfold and sixfold higher than that of controls, respectively. BSP expression dropped toward baseline levels at 36 hours in both groups. CONCLUSIONS: Mechanical tensile stress up-regulated the expression of BSP. Low mechanical tensile stress induced earlier and more intensive up-regulation of BSP mRNA; this might represent the optimal stimuli for cementoblast activity.

Response of cementoblast-like cells to mechanical tensile or compressive stress at physiological levels in vitro.

To clarify the role of cementoblast in orthodontic-related root resorption, this study was attempted to examine whether murine cementoblast-like cells are responsive to mechanical stress, and how mechanical forces regulate bone sialoprotein (BSP) and osteopontin (OPN) gene expression in these cells in vitro. In this force-loading model, defined and reproducible mechanical loadings of different magnitudes and types were applied up to 24 h. Besides a transitory and reversible change in cell proliferation, remarkable alterations in gene transcription of BSP and OPN were found. BSP mRNA was suppressed by the stresses. Three and six hours-loadings at 2,000 microstrain up-regulated the expression of OPN mRNA, while the other loadings inhibited it. The study also concluded that 4,000 microstrain was likely to exert more influence on cementoblast-like cells than 2,000 microstrain. Furthermore, no obvious evidence indicated the difference between tension and compression. These results suggested that cementoblast-like cells are sensitive to mechanical stress, and may play a role in regulating orthodontic-related root resorption/repair.