A high-power long lifetime beam dump for the Thomson scattering diagnostic system in the XuanLong-50 experiment.

The Energy iNNovation's XuanLong-50 is a spherical torus experiment with up to 10 s plasma operation duration. A 3 J/50 Hz pulsed laser is used in the Thomson scattering diagnostic system that is developed to measure the time evolutions of plasma electron temperature and density profiles. The expected laser pulse number is about 7.5 × 106/year with a power load of 150 W. To meet at least 1-year lifetime requirement, a Chevron type beam dump with polished molybdenum plates is designed and fabricated, which absorbs the laser beam energy in a 3D structure to reduce the laser fluence deposited on the material surface. To prevent the backscattered stray light from interfering with the Thomson scattering measurements, a 7.5 m beam path with folding mirrors is set between the beam dump and the plasma scattering volumes. Details of the beam dump design procedure including the laser beam profile control, multi-pulse laser damage threshold, heat dissipation, Zemax modeling, folding mirror selection, and beam path enclosure are presented together with the testing results.

A novel polychromator calibration method for Thomson scattering diagnostics.

Polychromators are most frequently used in Thomson scattering (TS) diagnostics to analyze the scattered light spectrum and intensity so that the plasma electron temperature (Te) and density (ne) can be derived. For Te measurements, the spectral response of the polychromator channels and the relative spectral responsivities need to be calibrated. The spectral response is calibrated with a bromine tungsten lamp and a monochromator in a conventional way. A novel method for calibrating the relative spectral responsivities of the polychromators is described in detail. A broadband pulsed Light Emission Diode (LED) is used, which has a spectral irradiance similar to that of the TS spectrum, and the LED can be driven in pulse mode with the pulse width similar to the TS signal pulse width of about 10-20 ns full width at half maximum. This new method allows for the calibration to be done after the polychromator is fully installed, and in situ system calibration can be easily performed, showing the advantages of accuracy, simplicity, efficiency, and flexibility. For ne measurements, absolute sensitivity calibration is done by Rayleigh scattering with argon gas. Formulas for calculating the plasma density from the calibration data and the polychromator signals from the off-laser wavelength channels are presented.

Thomson scattering diagnostic system for the XuanLong-50 experiment.

A 15-point Thomson scattering diagnostic system is developed for ENN's spherical torus experiment XuanLong-50 (EXL-50). A BeamTech laser with 3 J/pulse (1064 nm wavelength) at 50 Hz repetition rate is chosen for measurements during EXL-50 plasma operations. To enable measurements at low density (∼0.5 × 1018 m-3) plasma operations, the opto-mechanical subsystems are carefully designed to maximize the collection and transmission of the scattered light and to minimize the stray light level. In addition, the high bandwidth trans-impedance amplifiers and segmented high speed waveform digitizers allow for the application of muti-pulse averaging to further improve the signal-to-noise ratio. Details of the diagnostic system are described and initial experimental results are presented.

[Hippocampus is involved in 17ß-estradiol exacerbating experimental occlusal inter- ference-induced chronic masseter hyperalgesia in ovariectomized rats].

OBJECTIVE: To investigate the influence of chronic masseter hyperalgesia induced by 17ß-estradiol (E2) and experimental occlusal interference (EOI) on underlying mechanism in hippocampus of ovariectomized (OVX) rats. METHODS: In the study, 32 OVX rats were randomly divided into 4 groups (8 rats/group): The control group was OVX group, and 0 µg/d E2 (vehicle) injection was started 7 d after OVX without EOI; in the experimental group (1) OVX + E2 group, 80 µg/d E2 injection was started 7 d after OVX without EOI; in the experimental group (2) OVX + EOI group, vehicle injection was started 7 d after OVX and EOI was applied 17 d after OVX; in the experimental group (3) OVX + E2 + EOI group, 80 µg/d E2 injection was started 7 d after OVX and EOI was applied 17 d after OVX. Bilateral masseter muscle mechanical withdrawal thresholds were measured before OVX, 7 days after OVX (before E2 injection), 17 days after OVX (10 days after E2 injection and before EOI) and 24 days after OVX (7 days after EOI). Immunofluorescence staining was used to reveal phospho-extracellular signal regulated kinase 1/2 (p-ERK1/2)-positive neurons in CA3 of hippocampus. The protein expression of p-ERK1/2 in hippocampus was detected using Western Blot. RESULTS: Compared with the control group [left side: (135.3±8.5) g, right side: (135.4±10.8) g], bilateral masseter muscle mechanical withdrawal thresholds of OVX+E2 group [left side: (113.3±5.6) g, right side: (112.5 ± 5.6) g] and OVX+EOI group [left side: (93.3±5.4) g, right side: 90.8±5.5) g] were decreased (P < 0.01). Bilateral masseter muscle mechanical withdrawal thresholds were significantly lower in OVX+E2+EOI group [left side: (81.2±6.2) g, right side: 79.8±7.7) g] than in the control, OVX+E2 and OVX+EOI groups (P < 0.05). The proportion of p-ERK1/2 positive neurons in the CA3 region of the hippocampus was increased in the control, OVX+E2, OVX+EOI and OVX+E2+EOI groups in turn, and the difference between the groups was statistically significant (P < 0.05). p-ERK1/2 protein expression was increased in the control, OVX+E2 and OVX+EOI groups in turn, but the difference was not statistically significant (P>0.05). p-ERK1/2 expression was significantly higher in OVX+E2+EOI group than in the other three groups (P < 0.05). CONCLUSION: High concentration of E2 could exacerbated EOI-induced chronic masseter hyperalgesia in ovariectomized rats, and its central mechanism may be related to the upregulation of the phosphorylation of ERK1/2 in hippocampus.

[Effect of porous zirconia ceramics on proliferation and differentiation of osteoblasts].

OBJECTIVE: To investigate the effect of porous surface morphology of zirconia on the proliferation and differentiation of osteoblasts. METHODS: According to different manufacturing and pore-forming methods, the zirconia specimens were divided into 4 groups, including milled sintering group (M-Ctrl), milled porous group (M-Porous), 3D printed sintering group (3D-Ctrl) and 3D printed porous group (3D-Porous). The surface micromorphology, surface roughness, contact angle and surface elements of specimens in each group were detected by scanning electron microscope (SEM), 3D laser microscope, contact angle measuring device and energy-dispersion X-ray analysis, respectively. MC3T3-E1 cells were cultured on 4 groups of zirconia discs. The cell morphology of MC3T3-E1 cells on zirconia discs was eva-luated on 1 and 7 days by SEM. The cell proliferation was detected on 1, 3 and 5 days by cell counting kit-8 (CCK-8). After osteogenic induction for 14 days, the relative mRNA expression of alkaline phosphatase (ALP), type Ⅰ collagen (Colla1), Runt-related transcription factor-2 (Runx2) and osteocalcin (OCN) in MC3T3-E1 cells were detected by real-time quantitative polymerase chain reaction. RESULTS: The pore size [(419.72±6.99) µm] and pore depth [(560.38±8.55) µm] of 3D-Porous group were significantly larger than the pore size [(300.55±155.65) µm] and pore depth [(69.97±31.38) µm] of M-Porous group (P < 0.05). The surface of 3D-Porous group appeared with more regular round pores than that of M-Porous group. The contact angles of all the groups were less than 90°. The contact angles of 3D-Ctrl (73.83°±5.34°) and M-Porous group (72.7°±2.72°) were the largest, with no significant difference between them (P>0.05). Cells adhered inside the pores in M-Porous and 3D-Porous groups, and the proliferation activities of them were significantly higher than those of M-Ctrl and 3D-Ctrl groups after 3 and 5 days' culture (P < 0.05). After 14 days' incubation, ALP, Colla1, Runx2 and OCN mRNA expression in 3D-Porous groups were significantly lower than those of M-Ctrl and 3D-Ctrl groups (P < 0.05). Colla1, Runx2 and OCN mRNA expressions in M-Porous group were higher than those of 3D-Porous group (P < 0.05). CONCLUSION: The porous surface morphology of zirconia can promote the proliferation and adhesion but inhibit the differentiation of MC3T3-E1 cells.

[Advance in research of occlusal dysesthesia].

Occlusal dysesthesia (OD) or phantom bite syndrome refers to a persistent complaint of uncomfortable bite sensation with no obvious occlusal discrepancy. OD is a rare condition, and is usually associated with emotional distress and triggered by dental treatments. The diagnosis and management of OD patients still remains a major challenge for dental practitioners and affected patients. This topical review aims to describe the properties, etiologies, diagnosis, managements and prognosis of OD comprehensively.

[Occlusion variation of posterior implant-supported single crown: a prospective 4-year follow-up study].

Objective: To analyze the longitudinal variation of occlusal force distribution and occlusal contact time in posterior implant-supported single crown with the computerized occlusal analysis system. Methods: Partially edentulous patients who visited the Department of Prosthodontics, Peking University School and Hospital of Stomatology between December 2012 and December 2013, and had received implant-supported single crown in the posterior region were enrolled. The participants underwent occlusal examinations with the computerized occlusal analysis system at 2 weeks, 3 and 6 months, 1, 2, 3, and 4 years after implant prosthesis delivery. The relative occlusal force (ROF) of implant prostheses, mesial adjacent teeth, and control teeth (corresponding teeth on the contralateral side) were recorded, and implant prosthesis occlusion time ratios (implant prosthesis occlusion time/occlusion time) were calculated. The interproximal contact between implant prostheses and adjacent teeth was evaluated using metal contact gauge and dental floss. Mechanical complications of implant prostheses were recorded. The paired t test or Wilcoxon signed-rank test was used to compare the implant prosthesis occlusion time ratios and ROF of implant prostheses at 2 different times as a self-control. The differences in ROF between implant prostheses and control teeth in the same participant at the same time were also analyzed using paired t test. Using a complementary log-log model, the correlation between the occurrence of veneering material fracture and ROF of implant prosthesis was analyzed with gender, age and follow-up time as the control variables. Results: Thirty-seven posterior fixed implant-supported single crowns in 33 participants, including 16 men and 17 women aged (42.8±12.9) years (23.9 to 70.0 years) were followed up for 2 weeks to 4 years [(38.3±15.2) months]. The ROF of implant prostheses increased significantly (P<0.01) from 2 weeks [(7.0±4.2)%] to 3 months [(9.9±6.8)%], whereas those of control natural teeth decreased significantly (P<0.05) from (13.1±6.1)% to (11.4±5.5)%. The ROF of implant prostheses continued to increase from 6 months to 1 year, from 1 year to 2 years and from 2 years to 3 years, with significant differences (P<0.05). Implant prosthesis occlusion time ratios also increased significantly between 2 weeks and 3 months and between 3 months and 6 months (P<0.05). No significant differences were found between other time points (P>0.05). For comparison between implant prosthesis and control teeth at the same time point, the ROF of the implant prostheses [(7.5±4.2)%] were significantly lower than those of the control teeth [(13.8±6.0)%] at 2 weeks (P<0.01). While at 4 years, ROF of implant prostheses [16.7% (8.6%, 32.4%)] became significantly higher than those of control teeth [9.5% (4.9%, 18.0%)] (P<0.05). ROF of the implant prostheses did not differ significantly with those of the control teeth in other follow-up time points (P>0.05). The 4-year cumulative incidence of proximal contact loss rate was 32% (22/68). The incidences of veneering material fracture and prostheses loosening were 16% (6/37) and 8% (3/37), respectively. Logistic regression showed a significant correlation between veneering material fracture and ROF of implant prostheses (r=0.26, P<0.05). Conclusions: The occlusal force and occlusal contact time of posterior implant-supported single crown change over time in 4-year follow-up period, which is mainly reflected in the increasing occlusal force and occlusal contact time. The occlusion of posterior implant prostheses should be carefully monitored during follow-up examinations, and occlusal adjustment should be considered when necessary.

[Adenosine triphosphate induced odontoblastic differentiation of human dental pulp cells in vitro and in vivo].

Objective: To choose a suitable efficient concentration of adenosine triphosphate (ATP) which can induce human dental pulp cells (HDPC) differentiate into odontoblast successfully, and explore the role of this concentration of ATP in dentin regeneration in vivo. Methods: HDPC were treated with different concentrations (0, 10, 400, 600, 800 µmol/L) of ATP. Then cell counting kit-8 (CCK-8), quantitative real-time PCR, and Western blotting were used to detect the cell proliferation and the expressions of odontoblastic differentiation related markers, dentin matrix protein 1 (DMP1) and dentin sialophosphoprotein (DSPP). Alizarin red S staining experiment was used to analyze the effect of ATP on the mineralization ability of HDPC. By the above experiments, the suitable effective concentration of ATP was chosen to pretreat the HDPC for 7 days, then cells were seeded on gelfoam, inserted into the root canal fragment, and subsequently transplanted into the subcutaneous space on the back of immunodeficient mice, after three months, the samples were stained with HE for histological analysis. Results: The CCK-8 results in 5 d showed that 10 µmol/L ATP obviously promoted the proliferation of HDPC, while the 600 and 800 µmol/L ATP apparently inhibited the HDPC proliferation, however, the proliferation in 800 µmol/L ATP group was lower than that of 600 µmol/L ATP group (P<0.05). qPCR and Western blotting results showed that the 600 and 800 µmol/L ATP significantly up-regulated the DMP1 and DSPP expressions (P<0.05), furthermore, there was no significant difference in the two groups, but no changes were found in other groups (P>0.05). After 21 days of culturing, there were obvious mineralization nodules in 600 and 800 µmol/L ATP groups, but no mineralization nodules in other groups. Quantitative analysis of the staining results showed the A value in 0, 10, 400, 600, and 800 µmol/L ATP groups were respectively 1.05±0.15, 1.11±0.23, 1.15±0.17, 3.65±0.30, and 3.40±0.43, and the A value in 600 and 800 µmol/L ATP groups were higher than those of other groups; however, there was no difference in 600 and 800 µmol/L ATP groups. The histological analysis showed that 600 µmol/L ATP could induce the HDPC differentiate into dentin-like structure in the root canal fragment. Conclusions: Therefore, the suitable effective concentration of ATP is 600 µmol/L, which could induce HDPC differentiate into odontoblast-like cells, and form the dentin-like structure in vivo.

[Characteristics of orofacial operant test for orofacial pain sensitivity caused by occlusal interference in rats].

OBJECTIVE: To compare the orofacial pain sensitivity with operant test and mechanical hyperalgesia with von Frey filaments of two orofacial pain models (EOI: experimental occlusal interference; pIONX: partial infraorbital nerve transection). To investigate the operant and evoked characteristics of EOI-rats. METHODS: The orofacial operant behaviors were tested by Ugo Basile Orofacial Stimulation Test System. The mechanical thresholds of vibrissal pads were tested by von Frey filaments. Male Sprague-Dawley rats were randomly divided into eight groups: von Frey group: sham-EOI, EOI, sham-pIONX, pIONX (sham: sham-operated group); operant test group: sham-EOI, EOI, sham-pIONX, pIONX (sham: sham-operated group). The mechanical thresholds and orofacial operant behaviors were tested on pre-operation and post-operation days l, 3, 7, 10, 14 and 21. RESULTS: In pIONX of von Frey group, the mechanical withdrawal threshold decreased from days 1 to 21 (P<0.05), peaking from days 7 to 10, and lasted until the end of the experiment. There was no significant difference between the bilateral sides. In pIONX of operant test group, the total contact time decreased from days 10 to 21 (P<0.05), peaking from days 10 to 14, and lasted until the end of the experiment. In EOI of von Frey group, the mechanical withdrawal threshold decreased from days 3 to 21 (P<0.05), peaking on day 7, and lasted until the end of the experiment. There was no significant difference between the bilateral sides. In EOI of operant test group, the total contact time decreased from days 1 to 21 (P<0.05), peaking from days 7 to 10, and lasting until the end of experiment. CONCLUSION: Orofacial operant test is a stable method to evaluate orofacial pain behaviors, which could discriminate the feature of neuropathic and EOI orofacial pain. In these two animal models, both of the operant behaviors and the mechanical hyperalgesia exhibited different time courses. Orofacial operant test provides a novel method for evaluating the orofacial pain sensitivity and studying the orofacial pain mechanism thoroughly.

[Research progress on factors influencing early liver dysfunction after liver transplantation].

Liver transplantation is the most effective treatment for end-stage liver disease, and early graft dysfunction often occurs after surgery. Early liver dysfunction after liver transplantation has become one of the complications after liver transplantation, which seriously affects the graft and patient survival. Therefore, reducing its occurrence can be an important means to improve the prognosis of recipients after liver transplantation. This paper discusses the research progress on the definition, influencing factors, and prognosis and prediction model in order to provide better prevention and effective reference for improving the success rate and prognosis of early liver dysfunction in recipients after liver transplantation.

[In vitro evaluation of the application of digital individual tooth tray in the impression making of mandibular full-arch crown abutments].

OBJECTIVE: To establish a method for the production of digital individual tooth tray based on three-dimensional (3D) scan, computer-aided design (CAD) and 3D printing, and to evaluate the effect of impression taking of full-arch crown abutments by digital individual tooth tray technique and conventional method through in vitro study. METHODS: The full crown preparation was performed on all the fourteen resin teeth in a standard model of mandibular dentition. The surface data of prepared abutments was collected by 3D scanning. A new project was created in a dental CAD software including all the fourteen teeth in the mandibular dentition. The design modules of anatomy crown and coping were selected for each tooth. The dentition was divided for three sections: right posterior teeth, anterior teeth, and left posterior teeth areas. The connector design was added between the abutments within the same section. The scanned data of the abutments were imported. The occlusal plane and insertion path were determined. The position of margin line, as well as the shape of anatomy crown and connector as the main body of the individual tooth tray were designed for each abutment. The shape of coping was generated as the space for holding the impression material. The finalized data of the main body was imported into Geomagic software. The retentive attachment was added at the external surface and the tissue stop was formed at the internal surface. The completed individual tooth tray was manufactured by 3D printing with resin material. The data of full-arch crown abutments were modified and printed. The conventional dentition trays A and B, as well as digital individual tooth tray were designed and printed for four copies each. The polyether impressions of the full-arch abutments were made by conventional one-step method using dentition tray A, and by sectional-impression technique using digital individual tooth tray and dentition tray B for four times each. The time spent for each impression taking and the numbers of defects at the shoulder and axial/occlusal surface in each impression were recorded. The impression quality of each abutment was evaluated. The overall quality distribution and the pass rate of abutments between the two methods were analyzed. RESULTS: The impressions made by conventional method had more defects at shoulder than those made by digital individual tooth tray technique. No difference of the number of defects at axial/occlusal surface between the two methods was observed. The digital individual tooth tray technique for the full-arch abutment impression exhibited higher pass rate of abutments and better quality of impression, compared with conventional methods. CONCLUSION: A new method for the production of digital individual tooth tray based on digital scanning, CAD and 3D printing was established. Compared with conventional method, using digital individual tooth tray technique for impression taking of full-arch abutments can achieve better effect.

[Method and accuracy of determining the jaw position of repositioning splint with the aid of digital technique].

OBJECTIVE: To establish the workflow of determining the jaw position of repositioning splint with the aid of digital technique, and to evaluate the accuracy of this workflow and compare the accuracy of raising different vertical dimensions in vitro. METHODS: A volunteer was recruited. The data of full-arch scans, cone beam computed tomography (CBCT) image and ultrasonic jaw motion tracking of the volunteer were acquired. The full-arch scans were merged with the CBCT image, which were then matched to the jaw motion tracking reference system. The jaw position of repositioning splint was determined when the anterior teeth opening was 3 mm and the condyle was in centric relation of the fossa in the sagittal plane. A digital repositioning splint was designed in the software based on virtual articulator and fabricated with additive manufacturing technique. After the splint was tried in, another CBCT image was taken and a qualitative analysis was conducted to compare the position of condyle between these two CBCT images. In the in vitro study, standard dental plaster casts with resin ball markers attached to the base were mounted onto a fully adjustable articulator in the intercuspal position. The dental casts were scanned by an extraoral scanner to establish digital models. The ultrasonic jaw motion tracking device was used to obtain simulated jaw movements on the articulator, which was repeated for three times. The digital models and data of jaw movements were merged in one coordination with the aid of bite forks. The jaw position of repositioning splint was determined by adjusting data of jaw movements, each of which was used to determine three vertical jaw positions 4 mm, 5 mm, and 6 mm with the horizontal jaw position of protrusion 2 mm. The virtual articulators with differently adjusted jaw movements were applied in designing repositioning splints, and the final repositioning splints and virtual jaw relationships were exported in STL format. Then the repositioning splints were fabricated with additive manufacturing technique and tried in plaster casts on the mechanical articulator, which were scanned and the jaw relationships on the mechanical articulator were exported later. The virtual jaw relationships and scanned jaw relationships were registered according to lower models and displacement of upper models was calculated. Ball markers were fit to acquire the coordinates of centers and absolute difference values of centers along three coordinating axes X, Y, and Z were calculated. One-way analysis of variance was conducted using SPSS 18.0 software to compare deviations of the three different vertical jaw relationships in two-side test and the significance level was 0.05. RESULTS: With the aid of multi-source data fusion and individualized jaw motion, the clinical workflow of determining jaw position of repositioning splint was preliminarily established. The designed jaw position was realized on the right and the condyle was more inferior than the designed position on the left. Both displacement of the upper models and absolute difference values of centers showed no significant differences (P>0.05) in different vertical jaw dimensions. The displacement of the upper models was (0.25±0.04) mm. The absolute difference values of centers along the three coordinating axes X, Y, and Z were respectively (0.08±0.01) mm, (0.30±0.02) mm, and (0.21±0.04) mm. CONCLUSION: A novel method of determining the jaw position of repositioning splint with the aid of digital technique is established. It is proved to be feasible by try-in after multi-data fusion, computer-aided design and computer-aided manufacturing. As is shown in vitro, it is accurate to apply this method in adjusting jaw position. Further clinical trial will be designed to evaluate its clinical effect.

[Quantitative analysis of occlusal changes in posterior partial fixed implant supported prostheses].

OBJECTIVE: To analyze changes in occlusal force distribution and occlusal contact in posterior partial fixed implant-supported prostheses over time, and to provide reference for the precise occlusion design, adjustment and maintenance of implant prostheses. METHODS: According to certain inclusion and exclusion criteria, patients were recruited from partially edentulous patients who had received implant-supported single crown or fixed bridge in the posterior region. The patients were collected since the implant prostheses settling and scheduled for the routine examination of implant prostheses and the occlusal examinations of complete dentition after 2 weeks, 3, 6, and 12 months. Occlusal examinations were taken with the articulating papers and T-Scan III (Tekscan, South Boston, USA), which could check and measure the occlusal contact condition of complete dentition. The occlusion time and relative occlusal forces of implant prostheses, mesial adjacent teeth and control teeth were recorded at the same time. RESULTS: Thirty-seven posterior partial fixed implant prostheses in 33 patients (17 women and 16 men, aged 24-70 years) were followed up for 3-12 months (average 8.3 months). At baseline, the relative occlusal forces of implant prostheses were significantly lower than those of the corresponding control teeth (P<0.001). However, after 3 months, the relative occlusal forces of implant prostheses had significantly increased (P<0.05), while control teeth decreased significantly (P<0.05), resulting in no statistical significance between them. The implant prostheses occlusion time ratio also increased significantly from 2 weeks to 3 months (P<0.05). There was no significant difference from the third month to the sixth month, or from the sixth month to the twelfth month (P>0.05). CONCLUSION: Light contact and time-delayed occlusion of posterior implant prostheses changes significantly in the first three months after settling implant prostheses. These changes mainly include the advance of the time point of the implant prosthesis to start the occlusion contact, and the increase of the occlusal force of the implant prosthesis. The occlusion of posterior implant prostheses should be carefully monitored at end of the third month follow-up clinically.

[Present situation and future of occlusal splint in treatment of oral diseases].

Occlusal splint is a removable device for the treatment of oral and maxillary diseases with reversible occlusal treatment property. When patients wear the occlusal splint, the occlusal contact state can be changed and the position of the lower jaw may be adjusted, with the improvement of functions of temporomandibular joints and masticatory muscles. There are various types of occlusal splints, among which stabilization splint, soft occlusal splint and repositioning splint are widely used in the treatment of temporomandibular disorders and night bruxism. For the patients requiring occlusal reconstruction, occlusal splint can be used as an important means to adjust and verify the therapeutic jaw position. As a major trend of research in future, the digital design and production of occlusal splint are still in the initial stage and need to be further improved.

[Effect of long-term resistance exercise on masseter muscle mechanical hyperalgesia in rats].

OBJECTIVE: To investigate the effect of long-term resistance exercise of hindlimb on mechanical hyperalgesia of bilateral masseter muscle in rats with or without occlusal interference. METHODS: Six-teen male Sprague-Dawley rats (220-250 g) were randomly divided into four groups: the naive control group, naive exercise group, occlusal interference control group, and occlusal interference exercise group. The rats in occlusal interference groups (occlusal interference control group and occlusal interference exercise group) obtained occlusal interference with 0.4 mm-thick crowns bonded to the right maxillary first molars. The rats in exercise groups (naive exercise group and occlusal interference exercise group) performed squat-type resistance exercises for 30 minutes, once a day, 5 days/week, lasting for 14 weeks. Resistance exercise was recorded every day. Mechanical withdrawal thresholds of bilateral masseter muscle were tested per week by use of modified electronic von-frey anesthesiometer. The rats were weighed per week. After the 14-week exercise, the muscle strength of the hindlimb was tested with a grip strength meter. Muscle (gastrocnemius and soleus) weight of bilateral hindlimb and length of bilateral fibula of the rats were obtained. The muscle-mass/body-mass ratios and muscle-mass/fibula-length ratios were calculated. RESULTS: Between the naive control group and naive exercise group, there was no significant difference in the mechanical withdrawal thresholds of bilateral masseter muscle for the 0-4 weeks (P>0.05). During the 5-14 weeks, the mechanical withdrawal thresholds of the rats in the naive exercise group were higher than those in the naive control group (P<0.05). Between the occlusal interference control group and occlusal interference exercise group, there was no significant difference in the mechanical withdrawal thresholds of bilateral masseter muscle for the 0-6 weeks (P>0.05). During the 7-14 weeks, the mechanical withdrawal thresholds of rats in the naive exercise group were higher than those in the occlusal interference control group (P<0.05). After the 14week exercise, the body mass of the rats in nonexercise group (the naive control group and occlusal interference control group) were larger than those in exercise group [(462±6) g vs. (418±14) g, P<0.05]. And the muscle strength of hindlimb of the rats in exercise group were bigger than those in non-exercise group [(6.75±0.13) N vs. (5.41±0.15) N, P<0.01]. CONCLUSION: long-term resistance exercise can increase mechanical withdrawal thresholds of the bilateral masseter muscle in rats with or without masseter muscle mechanical hyperalgesia.

ACC Plasticity Maintains Masseter Hyperalgesia Caused by Occlusal Interference.

Acute occlusal interference following improper occlusal alteration in dental practice can induce chronic masticatory muscle pain. The underlying mechanism has not been clarified. Synaptic plasticity in the anterior cingulate cortex (ACC) plays a key role in the chronic pain state. This study investigated the role of synaptic plasticity in the ACC in acute occlusal interference-induced chronic masticatory muscle pain. A rat model of experimental occlusal interference (EOI) was established. In vivo local field potential (LFP) recording was conducted to evaluate the change of synaptic strength and plasticity from the medial thalamus (MT) to the ACC after EOI application. The effects of microdialysis of antagonists of glutamate receptors into the ACC on synaptic transmission from the MT to the ACC were examined. Furthermore, the influence of inhibiting glutamate receptors in the ACC on EOI-induced mechanical hyperalgesia in the masseter muscles of rats was investigated. The amplitude of LFP in the ACC evoked by MT stimulation was significantly potentiated since 14 d of EOI application. Long-term potentiation of LFP in the ACC was reliably induced by theta burst stimulation to the MT in control rats but was occluded in 14-d EOI rats. Microdialysis of AMPA/kainate receptor antagonist CNQX into the ACC attenuated LFP in the ACC evoked by stimulating the MT in control and EOI rats. Administration of NMDA receptor subunit NR2B antagonist Ro 25-6981 into the ACC significantly alleviated the potentiation of MT stimulation-evoked LFP in the ACC of EOI rats without affecting that in control rats. EOI-induced hyperalgesia in the bilateral masseter muscles of rats was dose-dependently relieved after microdialysis of Ro 25-6981 into ACC. These findings provide direct evidence that prolonged acute occlusal interference potentiates synaptic transmission in the ACC, which in turn mediates chronic masticatory muscle pain.

[Docosahexaenoic acid inhibits hypoxia-induced pulmonary arterial smooth muscle cells phenotype switching by inhibiting NFATc1 signaling].

Objective: To explore the molecular mechanism of docosahexaenoic acid (DHA) on regulating the phenotype switching of hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs). Methods: The PASMCs were isolated from Sprague Dawley rats. PASMCs were divided into five groups: normal control group, hypoxia group (1%O(2, )94%N(2, )5% CO(2) stimulation for 12 hours), hypoxia+ DHA group (10 µmol/L DHA pretreatment followed by 12 hours hypoxia), hypoxia+ DHA+ NFATc1 overexpression group (transfection of the NFATc1 lentivirus for 24 hours, followed by hypoxia stimulation for 12 hours after 10 µmol/L DHA treatment), and hypoxia+ DHA+ siNFATc1 group (transfection the siNFATc1 for 24 hours, followed by hypoxia stimulation for 12 hours after 10 µmol/L DHA treatment). The hypoxia stimulation was achieved by use of a special hypoxia incubator (1%O(2, )94%N(2, )5%CO(2)). The expressions of NFATc1 of various groups were determined by qRT-PCR and Western blot. The expression of α-SMA was determined by immunofluorescence staining, qRT-PCR and Western blot. The expression of SM22 was determined by qRT-PCR. The proliferation of PASMC was determined by EDU staining. Results: The mRNA and protein expression levels of NFATc1 were significantly upregulated in hypoxia group compared with the normal control group (P<0.05), while hypoxia-induced upregulation of NFTAc1 could be significantly downregulated by DHA treatment (P<0.05). The α-SMA positive cell number, protein and mRNA levels of α-SMA and the mRNA level of SM22 were significantly lower in the hypoxia group than in normal control group, which could be significantly reversed by DHA, the protective effects could then be abolished by NFATc1 overexpression. Above indices were significantly lower in the hypoxia+ DHA+ siNFATc1 group than in hypoxia+ DHA+ NFATc1 overexpression group (P<0.05). The proliferation of PASMCs was significantly higher in the hypoxia group than in the control group (P<0.05), and which could be significantly reduced by DHA (P<0.05), and the protective effect of DHA could be significantly abolished by overexpression of NFATc1 (P<0.05). The proliferation of PASMCs was significantly lower in the hypoxia+ DHA+ siNFATc1 group than in the hypoxia+ DHA+ overexpression NFATc1 group (P<0.05). Conclusion: DHA could prevent hypoxia-induced PASMCs phenotype switching and proliferation by inhibiting NFATc1 signaling.

[Changes of productions of energy metabolism in masseter of rats induced by occlusal interference].

OBJECTIVE: To investigate the effect of occlusal interference on the energy metabolism of masticatory muscle by studying the changes of adenosine triphosphate (ATP), adenosine diphosphate (ADP), inosine monophosphate (IMP), phosphocreatine, creatine, lactate and pH level in masseter muscles of rats after occlusal interference. METHODS: Fifty male Sprague-Dawley rats were randomly assigned into experimental group (n=40) and control group (n=10). In experimental group, 0.4 mm thick metal crown was cemented to the upper right first molar of the rat, and maintained for 3, 7, 10, 14 d separately (n=10 for each time point). No occlusal interference was applied for control group. Bilateral masseter muscles of all the rats were acquired under general anesthesia. The samples of 5 rats in each group were fully homogenized with 0.4 mol/L perchlorate (10 mL/g). The homogenates were centrifuged, filtered and analyzed for ATP, ADP, IMP, phosphocreatine, creatine and lactate content by high performance liquid chromatography. The other samples in each group were mixed with homogenates containing 5 mmol/L sodium iodoacetate (10 mL/g), then homogenized and measured for pH value by pH meter in thermostatic water bathunder 37 degrees centigrade. RESULTS: Compared with control group, ATP content in bilateral masseter of the rats increased 3 d after occlusal interference [right side:(5.36±0.13) µmol/g,left side:(5.77±0.25) µmol/g] (P<0.05), and back to normal on 7, 10 and 14 d. There was an increase in IMP [right side:(0.21±0.03) µmol/g,left side:(0.19±0.03) µmol/g]and creatine content [right side:(24.76±2.94) µmol/g,left side:(27.75±2.23) µmol/g]in bilateral masseter of the rats 7 d after occlusal interference (P<0.05) and no difference was detected on 3, 10, and 14. Phosphocreatine content in bilateral masseter started to decline 7 d after occlusal interference and maintained the low level on 10 and 14 d [right side:(10.70±0.71) µmol/g, (11.57±0.52) µmol/g, (10.74±1.39) µmol/g, left side:(10.05±0.57) µmol/g, (10.75±1.12)µmol/g, (10.61±1.15) µmol/g](P<0.05). No change of ADP, lactate or pH level in bilateral muscles of the rats after occlusal interference was observed (P>0.05). CONCLUSION: Occlusal interference influences the content of energy metabolites in masticatory muscle of rats, which may be related to the pathological process of masticatory muscles induced by occlusal interference, such as muscle pain, dysfunction and altered fiber architecture.

Molecular Changes Involving MEK3-p38 MAPK Activation in Chronic Masticatory Myalgia.

The exact mechanism underlying chronic masticatory myalgia (CMM), a conspicuous symptom in temporomandibular disorders, remains unclear. This investigation compared gene expression profiles between CMM patients and healthy subjects. Peripheral blood leukocytes were collected in 8 cases and 8 controls and subjected to whole genome microarray analyses. Data were analyzed with Gene Ontology and interactive pathways analyses. According to Gene Ontology analysis, categories such as ion transport, response to stimuli, and metabolic process were upregulated. The pathway analysis suggested overexpression of the mitogen-activated protein kinase (MAPK) pathway in CMM patients and to a higher degree in a pathway network. Overexpression of representative members of the MAPK pathway-including MAPK kinase 3 (MEK3), calcium voltage-gated channel auxiliary subunit gamma 2 (CACNG2), and growth arrest and DNA damage-inducible gamma (GADD45G)-was validated with real-time polymerase chain reaction. The upregulation of MEK3 was negatively correlated with the age of the CMM group. In the next step, the authors focused on MEK3, the gene that exhibited the greatest degree of differential expression, and its downstream target protein p38 MAPK. The results revealed upregulation of MEK3, as well as phosphorylated MEK3 and phosphorylated p38 MAPK, in CMM patients. These results provide a "fingerprint" for mechanistic studies of CMM in the future and highlight the importance of MEK3-p38 MAPK activation in CMM.

[The loss of interproximal contact between posterior fixed implant prostheses and adjacent teeth: a retrospective study].

OBJECTIVE: To investigate the interproximal contact(IC) loss rate and the associated risk factors of IC loss between posterior fixed implant prostheses and the adjacent teeth. METHODS: Ninety-seven posterior fixed implant prostheses including 165 IC in 78 patients(34 men, 44 women) between 23 and 76 years of age were investigated. The period after restoration ranged from 1 to 44 months. The IC between implant prostheses and adjacent teeth was evaluated using a 30-µm-thick contact gauge and dental floss, and the IC was regarded as lost when the gauge or dental floss was inserted into an IC without any resistance at follow-up visits. The state of IC, region of implant prostheses, the condition of opposing dentition, the vitality of the adjacent teeth and the time interval of tooth loss were also confirmed for correlation analysis. RESULTS: All 78 patients finished follow-up examination. Forty-eight of 165 IC(29%) were regarded as lost. The IC loss rate at the mesial aspect[75%(36/48)] was significantly greater than that at the distal aspect[25%(12/48)](χ(2)=7.344,P=0.007). The difference between IC loss rate in the maxilla[46% (22/48)] and that in the mandible[54%(26/48)] was not significant(χ(2)=2.992,P=0.084). Free-end[hazard ratio (HR)=2.870], and the time interval of tooth loss(HR=0.919) affected the loss of IC significantly(P<0.05, Cox regression analysis). CONCLUSIONS: Loss of IC between posterior fixed implant prostheses and adjacent teeth was one of biological complications, which was observed frequently at follow-up visits. Patients who have the free-end fixed implant prostheses, or undergo short time interval of tooth loss before restoration may have high risk of the IC loss.