An Evidence-Based Medical Review on Promoting Gastrointestinal Function Recovery After Colorectal Cancer Surgery.

Objective: The objective of this study was to search for, evaluate, and summarize data related to a faster postoperative recovery in patients with colorectal cancer (CRC) based on literature from China as well as internationally. This will serve as an evidence-based foundation for the clinical implementation of enhanced postoperative recovery of gastrointestinal function in patients with CRC. Methods: Based on the hierarchical "6S" evidence model, we conducted a systematic search of computerized decision-support systems, guideline websites, as well as domestic and international databases for evidence, guidelines, expert consensus statements, clinical decision-making, best practices, evidence summaries, and systematic reviews of interventions focusing on accelerating gastrointestinal function rehabilitation after CRC surgery. The time limit for the search was from the date of creation of the database to January 2023. Two researchers evaluated the quality of the literature that was included, and we extracted data and summarized the evidence from those publications that fulfilled the quality criteria. Results: The review included a total of 21 publications, comprising 6 guidelines, 6 systematic reviews, 3 expert consensus statements, 4 randomized controlled trials, and 2 evidence summaries. We summarized 51 best evidence findings across five areas: organizational management, preoperative risk assessment, education, intraoperative monitoring, and postoperative management. Conclusion: There is a wide variety and wealth of information available on interventions to promote enhanced postoperative recovery of gastrointestinal function in patients with CRC. The use of evidence is discussed, keeping in mind the practical situation in China.

[Measuring three-dimensional displacement of tooth-supported rigid fixed bridge under oblique concentrated loading using digital laser speckle photography].

OBJECTIVE: To measure three-dimensional displacements of rigid fixed bridge under oblique concentrated loading and to analyze the effect of displacement on the stability of abutment teeth. METHODS: Right mandible of Beagle dog was used to establish the tooth-supported rigid fixed bridge. Digital laser speckle photography was employed to measure the three-dimensional displacements of the prosthesis under oblique concentrated loading ranging from 200 g to 3000 g. RESULTS: The displacements of prosthesis increased as the load increased. When the load was on the abutment, the buccolingual displacement of the abutment under loading was the biggest but no more than 100 microm. This was followed by mesiodistal and occlusallingual displacements. With slighter loadings, the buccolingual displacements of non-loaded abutment were greater than the mesiodistal displacements. However, as the loading increased greater mesiodistal displacements on non-loaded abutment were found compared to buccolingual displacements. When the bridge was loaded, the biggest displacements of the prosthesis were always shown on the buccolingual direction, followed by the mesiodistal direction and the occlusallingual direction. The displacements with loaded bridge were smaller than those when the load was applied on abutment. CONCLUSION: The displacements of rigid fixed bridge change with different loading positions. This has implications on the design of prosthesis. Lateral force should be minimized and early occlusion contact should be avoided, especially on the feeble abutment. This study has developed a new method for measuring bit shift of teeth.

Flavokawain B induces apoptosis of human oral adenoid cystic cancer ACC-2 cells via up-regulation of Bim and down-regulation of Bcl-2 expression.

Novel effective drugs are still urgently needed in the prevention and treatment of oral adenoid cystic carcinoma (ACC). In this study, we have assessed the antitumor potential and molecular mechanisms of flavokawain B (FKB) as a kava chalcone on the ACC-2 cell line in vitro. The results demonstrated that FKB could significantly inhibit the cell proliferation of ACC-2 in a dose-dependent manner that was associated with induced apoptosis and cell cycle G2-M arrest, and the half maximal inhibitory concentration (IC50) of flavokawain-B treatment for 48 h was estimated to be 4.69 ± 0.43 µmol/L. Mechanistically, FKB could induce the release of cytochrome c from mitochondria into the cytosol, and activate the cleavage of caspase-3 and, eventually, the poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner, leading to marked apoptotic effect of ACC-2 cells. The apoptotic action of FKB was associated with the increased expression of proapoptotic proteins: Bim, Bax, Bak and a decreased expression of antiapoptotic Bcl-2. Among them, Bim expression was significantly induced by FKB, and knockdown of Bim expression by short-hairpin RNAs attenuated the inhibitory effect induced by FKB on ACC-2 cells. These results suggest Bim may be one of the potential transcriptional targets, and suggests the potential usefulness of FKB for the prevention and treatment of ACC.

[Finite element analysis of different intramedullary fixation methods for the treatment of senile pubic ramus fractures].

OBJECTIVE: To evaluate the biomechanical stability of elastic intramedullary nail in the treatment of pubic ramus fractures by finite element analysis, and to compare the stability of elastic intramedullary nail with cannulated screw intramedullary fixation. METHODS: The CT data of the pelvis of a volunteer were selected, and the three-dimensional model of the pelvis was reconstructed by reverse engineering software and the fracture of the pubic ramus fractures was simulated by osteotomy. The hollow nail model, single elastic nail model and double elastic nailmodel were assembled with different implants respectively. The mesh division, material assignment loading and other steps were carried out in the ANSYS software, and then the calculation was submitted. RESULTS: The overall displacement of the pelvis of the elastic nail model was smaller than that of the cannulated screw model, in which the double elastic nail model had the smallest overall displacement, but the cannulated screw model had the smallest plant displacement and the single elastic nail model had the largest plant displacement. Although the stress of cannulated screw was small, there was obvious stress concentration, the stress of elastic nail was large, but there was no obvious stress concentration, especially the stress distribution of double elastic nail was more uniform and the overall stress of pelvis was the smallest. CONCLUSION: All the three fixation methods can effectively improve the stability of the anterior ring of the pelvis. Among them, there is no significant difference in the overall biomechanical propertiesof hollow nail fixation and double elastic nail fixation, which is better than that of single elastic nail fixation. Elastic nail fixation has the advantages of minimally invasive surgery and good biomechanical stability, so it can be used as a better surgical method for the treatment of pubic ramus fractures.

[Intestinal absorption of the effective components of Schisandra chinensis Baill by rats single-pass perfusion in situ].

The aim of the study is to investigate rat intestinal absorption behavior of three main active components, schisandrol A, schisandrin A and schisandrin B in Schisandra chinensis Baill extracts in intestine of rats. With phenol red as the indicator, in situ single pass intestinal perfusion (SPIP) model was used and the concentrations of three main active components in perfusion solution of different intestinal segments (duodenum, jejunum, ileum, and colon) were determined by HPLC in combination with diode array detection. The results showed that the absorption rate constant (Ka) and effective permeability values (Peff) of three main active components in Schisandra chinensis Baill extracts had significant difference (P < 0.05) at different concentrations of perfusion solution, the Ka and Peff first increased and then decreased with the increase of drug concentration, the middle concentration was higher than those of the other two concentrations. The saturate absorption phenomena were observed, and it suggested that the transport mechanisms of three main active components in vivo were similar to active transport or facilitated diffusion. Three active components can be well absorbed in all of the intestinal segments, while duodenum is the best absorption region. The Ka and Peff of three active components in jejunum and ileum had no significant difference (P > 0.05). The absorption of the three active components displayed significant difference (P < 0.05) at different intestinal segments of rats. Schisandrin A had the best absorption in duodenum. The Ka and Peff among three active components were sequenced as follows: schisandrin A > schisandrin B > schisandrol A in other intestinal segments, and there is significant difference (P < 0.05) between them.

[Relationship between tissular structure and strength of fresh bull periodontal ligament].

OBJECTIVE: To study the relationship between the width and the content of fiber in peridontal ligament (PDL) and the strength of peridontal membrane. METHODS: Fresh mandible of bull was obtained to prepare for a 5 mm x 2 mm x 10 mm cuboid including teeth, peridontal membrane, and alveolar bone. The width of the PDL was measured under a stereomicroseope. Pull stress was loaded on the test piece until it broke. The stress-strain curve was recorded. The broken ends of the PDL was dyed with siriue to adalyze the content of fiber. RESULTS: The relationship between the width of the PDL and the maximum stress was expressed as Y = 9.786e(-3.6693x). The relationship between the width of the PDL and the physiological ultimate stress was expressed as Y = e((2.188(-3.953)x). The relationship between the percentage of fiber and maximum stress was expressed as Y = 20.788-0.755x + 0.007x(2). The relationship between the percentage of fiber and the physiological ultimate stress was expressed as Y = 1.39e(-14) x x(7.666). The initial physiological stress was 0.28 N/mm2. CONCLUSION: The strength of PDL increases with the decrease of PDL width and increase of fiber content.

[A structural mechanics study with human maxillary premolar].

OBJECTIVE: To evaluate the stress distribution and offset of dental and periodontal tissues imposed by changes in inner diameter of pulp cavity. METHODS: Six models of maxillary second bicuspid tooth with different inner diameter of pulp cavity were established, including: (1) calcificated pulp without pulp chamberi (2) mostly calcificated pulp chamber with inward reduction of 0. 5 mm in normal pulp cavity; (3) initially calcificated pulp chamber with inward reduction of 0.25 mm in normal pulp cavity; (4) normal pulp cavity; (5) initially absorbed pulp chamber with outward expansion of 0.25 mm in normal pulp cavity; (6) mostly absorbed pulp chamber with outward expansion of 0.5 mm in normal pulp cavity. Vertical and oblique forces with 160 N were loaded on the central fossa, respectively, in order to calculate the stress distribution of dental and periodontal tissues and the maximum incipient offset of the teeth. RESULTS: With loaded vertical and oblique forces on central fossa, increased stress distribution of periodontal tissues and maximum incipient offset of teeth were found in all of the models, which increased with the increase of pulp cavity. CONCLUSION: The change in inner diameter of pulp cavity has an impact on the stress distribution of periodontal tissues and maximum incipient offset of the second upper bicuspid teeth.

Osteocyte: the impresario in the electrical stimulation for bone fracture healing.

Delayed healing and nonunions of bone fracture are critical problems in orthopedic surgery. Electrical stimulation has been used as a therapeutic method for enhancing bone healing for a long time. Despite unanimous clinical success, the underlying mechanism concerning bone tissue in response to electrical stimulation remains poorly understood. In the meantime, emerging evidences suggest that osteocytes, with their unique location and morphologies, play an important role in regulating the behaviors of other bone cells, including osteoblasts, osteoclasts and their progenitor cells. In this paper, we hypothesize that osteocytes are the sensory cells for the electrical stimulation, and they orchestrate the whole process of new bone formation and remodeling in the electrotherapy for bone fracture. The postulated electrosensory transduction pathway might be a coupling effect of osteoblasts and osteoclasts, which is regulated by the biochemical signals expressed from osteocytes after sensing the membrane potential changes. It is believed that better understanding of this mechanism would facilitate optimizing the electrotherapy for bone disorders and assist in solving these clinical problems.

[Effect of gilding technique on the element release of beryllium ion from Vera Bond titanium alloy].

OBJECTIVE: To research the effect of gilding technique on the element release from Vera Bond Ti alloy exposed to artificial saliva. METHODS: To divided experimental group into 4 groups: common used Ti porcelain crown (controlling group, A1), polished Ti porcelain crown (polished group, A2), gilded Ti porcelain crown (gold-plating group, A3), gilded Ti porcelain crown prolonged 50% (gold-plating prolonged 50% group, A4). T measure the quantity of beryllium ion in artificial saliva after 1 month, 3 months and 6 months by means of ICP-AES. So the efect of released beryllium ion with different treatments and the role of different times with the same treatment were compared. RESULTS: The quantity of released beryllium ion was statistic significant among different treatments. The quantity of released beryllium ion was gradually increased with the same treatment. The speed of released beryllium ion was gradually decreased with the same treatment. CONCLUSION: The gilding treatment can decrease the quantity of beryllium ion which released from Ti porcelain crown,and improve the biocompatibility.

[Neuroprotective effects of topiramate and folic acid on young rats with kindling-induced epilepsy].

OBJECTIVE: To study the neuroprotective effects of topiramate (TPM) alone or together with folic acid (FA) on young rats with kindling-induced epilepsy. METHODS: Rat models of epilepsy were prepared by pentylenetetrazol (PTZ)-induced kindling. Seventy-two 3-week-old male Wistar rats were randomly divided into 6 groups: four TPM-treated epilepsy groups (TPM 20, 40 or 80 mg/kg/d and TPM 40 mg/kg/d + FA 5 mg/kg/d), a positive control group (untreated epilepsy group) and a negative control group (normal control group). After two months of administration, behaviors of the rats were recorded; serum levels of neuron-specific enolase (NSE) were measured using ELISA; pathological changes in the hippocampus were observed. RESULTS: The frequency of convulsion seizures in the 20, 40 and 80 mg TPM treatment and TPM+FA groups was 44.7 +/- 2.9, 44.3 +/- 3.1, 42.7 +/- 3.2, and 40.8 +/- 3.7 respectively, which were significantly lower than that in the positive control group (48.4 +/- 3.7) (P <0.01). Twenty, forty and eighty mg TPM treatment and TPM+FA treatment significantly reduced NSE levels from 35.71 +/- 5.97 microg/L of the control group to 27.40+/- 6.40, 24.79 +/- 6.22, 21.47 +/- 6.87 and 22.55 +/- 7.02 microg/L respectively (P <0.05). Neuronal apoptosis in the CA3 and CA1 regions were alleviated in the four TPM treatment groups compared with positive control. The number of necrotic neurons was progressively reduced with the increased dose of TPM. The 40 mg TPM+FA treatment group showed less necrotic neurons in the CA3 and CA1 regions than the 40 mg TPM alone treatment group. CONCLUSIONS: TPM has protective effects against epilepsy-induced neuronal damage. The effect is dose-dependent. A combination of TPM and FA can produce a synergistic effect.

[Effect of gilding technique on the release of elements from copper-based alloy post-core].

OBJECTIVE: To evaluate the effect of gilding technique on the release of element from copper-based alloy post-core exposed to artificial saliva. METHODS: The quantities of nickel ion and copper ion released from common copper-based alloy post-core (control group), blasting gilding copper-based alloy post-core (blasting group) and burnishing gilding Copper-based alloy post-core (burnishing group) in artificial saliva after 1 month,3 months,6 months and 8 months of exposure were measured with atomic absorption spectrophotometer. The tooth tissues were stripped off at the eighth month and the oxygenization on the surface of the posts were observed. RESULTS: There was a significant difference of element release of nickel between the gilding groups and the control group at the sixth and eighth month. There was a significant difference of element release of copper between the gilding groups and the control group at the third, sixth and eighth month. The quantities of element released from the gilding groups were fewer than those from the control groups. The release of nickel and copper ions increased with the length of exposure significantly after three month of exposure. The element release from the control groups increased more rapidly than the gilding groups. The surface of the post-core in the control groups were all oxygenized while those in the gilding groups had been oxygenized only near the margins of the cores and the upper 1/3 part of the post with uncontinuous and relatively thin layers. CONCLUSION: Gilding surface treatment can decrease the release of nickel and copper ions from copper based-alloy post-core and the surface oxygenization, which will improve the biocompatibility of the core.

[An experimental study on hepatotoxicity of topiramate in young rats].

OBJECTIVE: Topiramate (TPM) has an evident efficacy in the treatment of childhood epilepsy for multiple pharmacologic properties. However it was reported that it may cause adverse effects such as liver failure and hepatitis, which arouses the attention of the medical field. This study aimed to investigate the hepatotoxicity of low-dosage, high-dosage TPM or TPM along with valproate sodium (VPA) in aspects of biochemistry indexes, oxidative stress indexes and liver pathomorphology in young rats. METHODS: Sixty 3-week-old male Wistar rats were randomly assigned into five groups of 12 rats (Groups A-E). The rats in the experimental groups (Groups A-C) were administered intragastrically with TPM 40 mg/(kg.d), 80 mg/(kg.d) and TPM 40 mg/(kg.d) plus VPA 300 mg/(kg.d) respectively. The rats in the negative control group (Group D) were administered with the same volume of distilled water. The ones in the positive control group (Group E) were treated by injection of 10% carbon tetrachloride dissolved in olive oil subcutaneously at a dose of 5 mL/kg twice a week. After 3-month administration, the changes of body weight and liver pathomorphology were observed; biochemical markers in serum and indexes of oxidative stress in liver homogenate associated with hepatotoxicity were examined. RESULTS: The body weights of rats in the experimental groups were significantly lower than that of rats in the negative control group. The levels of serum alanine aminotransferase, alkaline phosphatase and the content of malondialdehyde, and the activity of superoxide dismutase in liver tissues did not change significantly in the experimental groups. The contents of glutathion in the high dosage of TPM group (29.85 +/- 1.62 mg/g prot) or in the TPM plus VPA group (29.63 +/- 4.47 mg/g prot) were significantly reduced compared with those of the negative control group (33.09 +/- 1.69 mg/g prot) and that of the low dosage of TPM group (32.43 +/- 2.11 mg/g prot) (both P < 0.05). In the histopathological examination, extensive steatosis and diffuse punctate necrosis of hepatocytes distributed in the portal area were found by microscopy in the positive control group. There were granular degeneration of some hepatocytes near the central veins of hepatic lobules in the low dosage of TPM group and punctate necrosis of some hepatocytes in the high dosage of TPM group. In the TPM plus VPA group, histological examination showed granular degeneration and fatty degeneration of partial liver cells and punctate necrosis of some hepatocytes. CONCLUSIONS: Long-term use of TPM can decrease antioxidant capacity of organism, resulting in slight pathological changes of liver tissues. High dosage of TPM or TPM along with VPA administration enhances the risk of the side effects.

[Effect of cone angle on fracture resistance force of root and post-core system].

OBJECTIVE: To study the effect of cone angle on fracture resistance force of root and post-core system. METHODS: Forty-two simulated tooth roots made of polymethacrylate (PMMA) were divided into six groups according to the root canal cone angles of 0 degrees, 3.93 degrees, 5.71 degrees, 7.48 degrees, 11.31 degrees and 14.71 degrees. Cast post and cores were manufactured and cemented with zinc polycarboxylate cement (PC). Casting the post and core to restore every simulated tooth root. Each specimen was embedded in acrylic resin and then fixed in a special jig on the universal load-testing machine. A compressive load was applied at a 90-degree angle to the long axis of the core until fracture, at a crosshead speed of 1 mm/min. The maximum of load was recorded. RESULTS: The mean values of load in root and post-core system were 0.1225 kN, 0.1498 kN, 0.1600 kN, 0.1893 kN, 0.1078 kN and 0.0945 kN. There were significant differences in the fracture resistance among groups. CONCLUSION: The fracture resistance force of cast post and core increased with the enlargement of post cone angles under certain conditions.

[Effects of the loss of alveolar bone on the areas of periodontal ligament, mechanical fulcrum and fracture resistance of root and post-core system].

OBJECTIVE: To assess the effects of loss of alveolar bone on the areas of periodontal ligament (PL), mechanical fulcrum and fracture resistance of root and post-core system. METHODS: One hundred and eight simulated roots in the same length, taper and diameter were made of polymethylmethacrylate and were divided into 13 groups. Then the wax patterns of post-cores were casted and cemented. Each specimen was embedded in acrylic resin in accordance with different loss of alveolar bone and different mechanical fulcrum. Base on the anatomic and physiological special features of the periodontal tissues, three mechanical methods were designed. The compress test was run by the speed of 1 mm/min and the fracture resistance was recorded. The areas of periodontal ligament were measured and calculated. RESULTS: When the loss of alveolar bone and the mechanical fulcrum were 0 mm and 12/12 group, 1 mm and 11/12 group, 2 mm and 10/12 group, 3 mm and 9/12 group, 3.5 mm and 8.5/12 group, 4 mm and 8/12 group, 4.5 mm and 7.5/12 group, 5 mm and 7/12 group,5. 5 mm and 6.5/12 group, 6 mm and 6/ 12 group, 7 mm and 5/12 group, 8 mm and 4/12 group, 9 mm and 3/12 group, the means of the areas of PL (mm2) and fracture resistance (N) were 178.95 and 232. 90 +/- 25. 93, 159. 64 and 195.58 +/- 12.46, 141.18 and 173.92 +/- 13.51, 123.27 and 154.00 +/- 11.74, 106.14 and 123.25 +/- 14.29, 89.67 and 96.86 +/- 6. 20, 73.90 and 59.14 +/- 7.28, 58.82 and 52.52 +/- 5. 82, 44.44 and 45.90 +/- 7.40, 30.76 and 58.60 +/- 6.63 (mm, N). The linear correlations were found between the percentage of the loss of alveolar bone and surplus areas of PL, the loss of alveolar bone and the fracture resistance of root and post-core system, the percentage of the areas of PL and the fracture resistance of root and post-core system, the distance of the fulcrum and the percentage of the loss of alveolar bone. CONCLUSION: The loss of alveolar bone caused the decrease in areas of PL, the dessent of mechanical fulcrum, and the diminution of the fracture resistance of root and post-core system.

[Effects of post length on the dislocation of post and core crown].

OBJECTIVE: To evaluate the effects of the length of post on the dislocation of cast post and core crown. METHODS: Forty simulated tooth roots made of polymethyl methacrylate were divided into five groups according to different length of post. These cast post and core were bonded with zinc phosphate cement. Then these specimens were strectched on the INSTRON-4302 by the speed of 10 mm/min. The maximum of load was recorded. RESULTS: The loads of 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm were (203.25 +/- 57.19) N, (213.63 +/- 45.06) N, (234.44 +/- 59.27) N, (317.75 +/- 60.94) N, (334.25 +/- 58.00) N respectively. Linear regression analysis revealed the linear relationship of post length with dislocation, bonding, and mechanical interlocking; the values of r being 0.676, 1.000, 0.949; the regression equations being D = 73.225L - 325.776, B = 0.442L + 9.951, M = 72. 676L-334. 338. CONCLUSION: Mechanical interlocking is the main factor in dislocation of post and core crown. The length of post should be increased from 2/3 to 3/4 of the length of tooth root when prepared in clinic.

[Fracture resistence force of the cement-expanded composite screw post-core system].

OBJECTIVE: This is a study comparing the effects of different post designs on the fracture resistence. METHODS: Twenty-seven simulated tooth roots made of polymethyl methacrylate (PMMA) were divided into three groups, then the cement-expanded composite screw post-core system (CECSP), cement screw post-core system (CSP) and cast metal post-core system (CMP) were manufactured. The root and post-core system was compressed by the speed of 1 mm/min on the Instron 4302 and the fracture resistence force was recorded. RESULTS: Statistical analysis of the measured values showed the fracture resistence force of CECSP and CMP to be significantly greater than that of CSP (P < 0.05), but there was no significant difference between the fracture resistence force of CECSP and CMP (P > 0.05). CONCLUSION: The fracture mechanical properties of CECSP are much better than those of cement screw post-core system and are similar to cast metal post-core system. Therefore, it is possible to find a new way for restoration of endodontally treated teeth.

[The development and clinical applications of automatic negative pressure gun for biopsy].

Using the new negative pressure biopsy technology, the automatic negative pressure gun and the specific puncture needle for the biopsy have been developed. Renal biopsies were conducted in 1136 cases, with the success rate being 99.9%, and 29 cases gross hematuria while the hepatic biopsies were conducted in 16 cases, mass biopsies in 3 cases with the success rates being 100% respectively. The biopsy gun has the advantages of easy manipulation, higher success rate and lower incidence of complications.

Attenuation of inflammatory response by 25- hydroxyvitamin D3-loaded polylactic acid microspheres in treatment of periodontitis in diabetic rats.

OBJECTIVE: To investigate the inhibitory effects of 25-hydroxyvitamin D3 (25(OH)D3)-loaded polylactic acid (PLA) microspheres on inflammatory response in diabetic periodontitis. METHODS: 25(OH)D3-loaded PLA microspheres were produced using emulsion-solvent evaporation method. Rat bone marrow stromal cells (BMSCs) cultured with Aggregatibacter actinomycetemcomitans in high glucose medium were chosen to mimic diabetic periodontitis. After cultivation with 25(OH)D3-loaded PLA microspheres, inflammation-related proteins in BMSCs were detected using Western blot analysis. Periodontitis was induced using silk ligatures in diabetic rats, and 25(OH)D3-loaded PLA microspheres were placed into the periodontal pockets. Periodontal tissues were examined using hematoxylin and eosin staining and western blot analysis. RESULTS: Drug release from the 25(OH)D3-loaded microspheres was relatively steady during 70 days. In a diabetic periodontitis-like environment, 25(OH)D3-loaded microspheres upregulated vitamin D receptor expression, and downregulated nuclear factor-κB expression and signal transducer and activator of transcription 3 phosphorylation in the BMSCs. These 25(OH)D3 microspheres also attenuated periodontal inflammatory infiltrate and bone loss in diabetic rats with periodontitis. CONCLUSION: 25(OH)D3-loaded microspheres could ameliorate diabetic periodontitis by inhibiting inflammatory response, and may provide a potential therapy for patients with this disease.

Effect of proximal contact strength on the three-dimensional displacements of implant-supported cantilever fixed partial dentures under axial loading.

OBJECTIVE: This study investigated the effect of proximal contact strength on the three-dimensional displacements of cantilever fixed partial denture (CFPD) under vertically concentrated loading with digital laser speckle (DLS) technique. METHODS: Fresh mandible of beagle dog was used to establish the implant-supported CFPD for specimen. DLS technique was employed for measuring the three-dimensional displacement of the prosthesis under vertically concentrated loading ranging from 200 to 3000 g. The effect of the contact tightness on the displacement of CFPD was investigated by means of changing the contact tightness. RESULTS: When an axial concentrated loading was exerted on the pontic of the implant-supported CFPD, the displacement of the CFPD was the greatest. The displacement of the prosthesis decreased with the increase of contact strength. When the contact strength was 0, 0.95, and 3.25 N, the displacement of the buccolingual direction was smaller than that of the mesiodistal direction but greater than that of the occlusogingival direction. When the force on the contact area was 6.50 N, the mesiodistal displacement of the prosthesis was the biggest while the buccolingual displacement was the smallest. CONCLUSIONS: The implant-supported CFPD is an effective therapy for fully or partially edentulous patients. The restoration of the contact area and the selection of the appropriate contact strength can reduce the displacement of the CFPD, and get a better stress distribution. The most appropriate force value is 3.25 N in this study.

Temporal change in NMDA receptor signaling and GABAA receptor expression in rat caudal vestibular nucleus during motion sickness habituation.

Repeated exposure to a provocative motion stimulus leads to motion sickness habituation indicative of the existence of central processes to counteract the disturbing properties of the imposed motion. In the present study, we attempt to investigate whether NMDA and GABA(A) receptors in rat caudal vestibular nucleus neurons are involved in motion sickness habituation induced by repeated Ferris-wheel like rotation in daily session (2h/d). We showed that defecation response increased and spontaneous locomotion decreased within 4 sessions (sickness phase). They recovered back to the control level after 7 sessions (habituation phase). Western blot analysis found that NMDA receptor signal molecules: calmodulin protein kinase II and cAMP response element-binding protein (CREB) were both activated during sickness phase, while a prolonged CREB activation was also observed during habituation phase. Real-time quantitative PCR revealed an increase in c-fos and a decrease in Arc mRNA level during sickness phase. We also found an increase in GABA(A) receptor α1 subunit (GABA(A) α1) protein level in this stage. These results suggested that altered NMDA receptor signaling and GABA(A) receptor expression level in caudal vestibular nucleus were associated with motion sickness habituation. Furthermore, immunofluorescence and confocal laser scanning microscopy showed that the number of GABA(A) α1 immunolabeled neurons in caudal vestibular nucleus increased while the number of GABA(A) α1/Arc double labeled neurons and the average amount of Arc particle in soma of these neurons decreased during sickness phase. It suggested that GABA(A) receptor level might be negatively regulated by Arc protein in caudal vestibular nucleus neurons.