Head position affects the direction of occlusal force during tapping movement.

Despite numerous reports describing the relationship between head position and mandibular movement in human subjects, the direction and magnitude of force at the occlusal contacts have not been investigated in relation to head position. The objective was to investigate the effect of head position on the direction of occlusal force while subjects performed a tapping movement. Twenty-three healthy adult subjects were asked to sit on a chair with their back upright and to perform 15 tapping movements in five different head positions: natural head position (control); forward; backward; and right and left rolled. The direction and magnitude of force were measured using a small triaxial force sensor. The Wilcoxon signed-rank test and Bonferroni test were used to compare head positions in each angle of the anteroposterior axis direction and the lateral axis direction with respect to the superior axis. The force element in the anteroposterior axis shifted to the forward direction in the head position pitched backward, compared with control, pitched forward and rolled left positions (P = .02, <.01 and <.01, respectively). The force direction in the lateral axis with the head position rolled to the right or left shifted to the left and right directions, respectively, compared with those in the other positions (P < .05). Results of this study suggest that the head should be maintained in a position in which a stable tapping movement can be performed in a relaxed position without anteroposterior and lateral loading.

Peroxisome proliferator-activated receptor (PPAR) γ polymorphism, vitamin D, bone mineral density and periodontitis in postmenopausal women.

OBJECTIVES: PPARg regulates bone metabolism and inflammation. Our previous study suggested PPARg Pro12Ala polymorphism to represent a susceptibility factor for periodontitis in pregnant Japanese women. Several recent papers have drawn attention to a possible link between low bone mineral density (BMD) and periodontitis in postmenopausal women. Since the pathogenesis for both involve bone remodeling, they might share common risk factors such as gene polymorphisms and vitamin D level. The present study investigated possible associations between the PPARgPro12Ala polymorphism, periodontitis, BMD and serum 25(OH)D in postmenopausal Japanese women. MATERIALS AND METHODS: PPARgPro12Ala genotypes of 359 women were determined by PCR-RFLP. BMD and periodontal parameters of each woman were measured. Serum 25(OH)D levels were determined by radioimmunoassay. RESULTS: PPARgPro12Ala polymorphism was not associated with periodontitis or BMD as an independent factor. Serum 25(OH)D was significantly higher in Ala allele carriers compared to non-carriers. Only in the Ala allele carriers, positive correlations were found between mean clinical attachment level and BMD, between BMD and 25(OH)D, and between percentage of sites with probing depth ≥ 4 mm and 25(OH)D. CONCLUSIONS: PPARgPro12Ala polymorphism was not independently associated with periodontitis or BMD. However, the polymorphism might be a modulator of the relationship between the two conditions in postmenopausal Japanese women.

The possible mechanism of preterm birth associated with periodontopathic Porphyromonas gingivalis.

BACKGROUND AND OBJECTIVE: Previous studies have shown that Porphyromonas gingivalis is found in the amniotic fluid and placentae of pregnant women with some obstetric diseases. However, the biological effects of P. gingivalis on intrauterine tissues remain unclear. The aim of this study was to investigate the presence of P. gingivalis in chorionic tissues from hospitalized high-risk pregnant women, and the effects of P. gingivalis lipopolysaccharide on the production of proinflammatory molecules in human chorion-derived cells. MATERIAL AND METHODS: Twenty-three subjects were selected from Japanese hospitalized high-risk pregnant women. The presence of P. gingivalis in chorionic tissues was analyzed by PCR. Cultured chorion-derived cells or Toll-like receptor-2 (TLR-2) gene-silenced chorion-derived cells were stimulated with P. gingivalis lipopolysaccharide. Real-time PCR was performed to evaluate TLR-2 and Toll-like receptor-4 (TLR-4) mRNA expression in the cells. Levels of interleukin-6 and interleukin-8 in culture supernatants of the chorion-derived cells were measured by ELISA. RESULTS: P. gingivalis DNA was detected in chorionic tissues from two women with threatened preterm labor, two with multiple pregnancy and two with placenta previa. Stimulation of chorion-derived cells with P. gingivalis lipopolysaccharide significantly increased TLR-2 mRNA expression, whereas TLR-4 mRNA expression was not changed. P. gingivalis lipopolysaccharide induced interleukin-6 and interleukin-8 production in chorion-derived cells, but the P. gingivalis lipopolysaccharide-induced interleukin-6 and interleukin-8 production was reduced in TLR-2 gene-silenced chorion-derived cells. CONCLUSION: Our results suggest that P. gingivalis can be detected in chorionic tissues of hospitalized high-risk pregnant women, and that P. gingivalis lipopolysaccharide induces interleukin-6 and interleukin-8 production via TLR-2 in chorion-derived cells.

Evaluation of the Pentax-AWS(®) and the Macintosh laryngoscope in difficult intubation: a manikin study.

BACKGROUND: The Pentax-AWS (AWS(®)), a new video laryngoscope, has been shown to be useful in cases of difficult intubation. We hypothesized that the AWS(®) would be more useful in the settings of a narrow upper airway than the Macintosh laryngoscope. We compared each device in simulated scenarios of representative difficulty of tracheal intubation using a manikin. The primary endpoint was the rate of successful intubation. METHODS: With each device, 23 anesthesiologists performed tracheal intubation in a SimMan(®) manikin in the following scenarios: (1) normal airway, (2) tongue edema, (3) cervical spine rigidity, (4) pharyngeal obstruction, (5) jaw trismus, (6) tongue edema with pharyngeal obstruction. The intubation time and success rate were measured. Each participant was asked to rate the difficulty of intubation (1=very easy; 5=very difficult). RESULTS: In the scenarios of tongue edema and tongue edema with pharyngeal obstruction, the AWS(®) yielded a higher success rate (100% vs. 34.8%; P<0.001, 65.2% vs. 21.7%; P=0.006), a shorter intubation time [14.6 (7.0) vs. 33.4 (13.0) s; P<0.001, 24.5 (12.0) vs. 37.6 (11.9); P=0.047; mean (standard deviation)], and a lower difficulty score [2 (1-4) vs. 5 (1-5); P<0.001, 4 (2-5) vs. 5 (3-5); P<0.001; median (range)], compared with the Macintosh laryngoscope. CONCLUSION: The AWS(®) has an advantage over the Macintosh laryngoscope in simulated tongue edema and tongue edema with pharyngeal obstruction. Further studies in a clinical setting are necessary to confirm these findings.

Development of temporomandibular disorder symptoms: a 3-year cohort study of university students.

The aims of this study were to examine the incidence of temporomandibular disorders (TMDs) over a 3-year period and to evaluate the risk of self-reported TMDs among university students in Japan. The study population comprised 2374 university students examined at the start of their undergraduate course and 492 students re-examined after 3 years using questionnaires on symptoms of TMD and experiences of jaw injury, stress, orthodontic treatment and parafunctional habits. Cumulative incidence (%) and relative risks were calculated overall. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the degree of risks of these variables for symptoms of TMDs using logistic regression. Results of logistic regression analysis showed that male subjects with experience of jaw injury had a 3·54 (CI=1·45-8·68, P<0·01)-fold higher risk of temporomandibular joint (TMJ) pain than that for those who did not. Female subjects who reported experiencing stress and bruxism had 10·56 (CI=1·28-87·54, P<0·05)- and 5·00 (CI=1·21-20·71, P<0·05)-fold higher risks of TMJ sound, respectively, than the risk for female subjects who had not experienced stress or bruxism. The results indicated that experiences of jaw injury, stress and bruxism were significantly associated with increased risks of development of TMJ disorders in a 3-year cohort.

Surface grafting of biocompatible phospholipid polymer MPC provides wear resistance of tibial polyethylene insert in artificial knee joints.

OBJECTIVE: Aseptic loosening of artificial knee joints induced by wear particles from a tibial polyethylene (PE) insert is a serious problem limiting their longevity. This study investigated the effects of grafting with our original biocompatible phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) on the insert surface. METHODS: The hydrophilicity of the PE surface was determined by the contact angle of a water droplet, and the friction torque was measured against a cobalt-chromium alloy component. The wear amount was compared among PE inserts with or without cross-linking and MPC grafting during 5x10(6) cycles of loading in a knee joint simulator. The surfaces of the insert and the wear particles in the lubricant were subjected to electron and laser microscopic analyses. The mechanical properties of the inserts were evaluated by the small punch test. RESULTS: The MPC grafting increased hydrophilicity and decreased friction torque. In the simulator experiment, the wear of the tibial insert was significantly suppressed in the cross-linked PE (CLPE) insert, and even more dramatically decreased in the MPC-grafted CLPE insert, as compared to that in the non-cross-linked PE insert. Surface analyses confirmed the wear resistance by the cross-linking, and further by the MPC grafting. The particle size distribution was not affected by cross-linking or MPC grafting. The mechanical properties of the insert material remained unchanged during the loading regardless of the cross-linking or grafting. CONCLUSION: Surface grafting with MPC polymer furnished the PE insert with wear resistance in an artificial knee joint through increased hydrophilicity and decreased friction torque.

Effects of Sulfonylureas on Periodontopathic Bacteria-Induced Inflammation.

Interleukin-1ß (IL-1ß) is an inflammatory cytokine produced by monocytes/macrophages and is closely associated with periodontal diseases. The NLRP3 inflammasome is involved in IL-1ß activation through pro-IL-1ß processing and pyroptotic cell death in bacterial infection. Recently, glyburide, a hypoglycemic sulfonylurea, has been reported to reduce IL-1ß activation by suppressing activation of the NLRP3 inflammasome. Therefore, we evaluated the possibility of targeting the NLRP3 inflammasome pathway by glyburide to suppress periodontal pathogen-induced inflammation. THP-1 cells (a human monocyte cell line) were differentiated to macrophage-like cells by treatment with phorbol 12-myristate 13-acetate and stimulated by periodontopathic bacteria, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, or Fusobacterium nucleatum, in the presence of glyburide. IL-1ß and caspase-1 expression in the cells and culture supernatants were analyzed by Western blotting and enzyme-linked immunosorbent assay, and cell death was analyzed by lactate dehydrogenase assay. Stimulation of THP-1 macrophage-like cells with every periodontopathic bacteria induced IL-1ß secretion without cell death, which was suppressed by the NLRP3 inhibitor, MCC950, and caspase-1 inhibitor, z-YVAD-FMK. Glyburide treatment suppressed IL-1ß expression in culture supernatants and enhanced intracellular IL-1ß expression, suggesting that glyburide may have inhibited IL-1ß secretion. Subsequently, a periodontitis rat model was generated by injecting periodontal bacteria into the gingiva, which was analyzed histologically. Oral administration of glyburide significantly suppressed the infiltration of inflammatory cells and the number of osteoclasts in the alveolar bone compared with the control. In addition to glyburide, glimepiride was shown to suppress the release of IL-1ß from THP-1 macrophage-like cells, whereas other sulfonylureas (tolbutamide and gliclazide) or other hypoglycemic drugs belonging to the biguanide family, such as metformin, failed to suppress IL-1ß release. Our results suggest that pharmacological targeting of the NLRP3 pathway may be a strategy for suppressing periodontal diseases.

Granulocyte colony-stimulating factor induced reduction in pulpal necrosis.

AIM: To examine the effect of recombinant granulocyte colony-stimulating factor (G-CSF) on the number and function of neutrophils and on the histopathology of pulpal inflammation in normal and neutropenic rats. METHODOLOGY: The effect of G-CSF on changes in pulpal tissue was investigated at 2, 4, 7, and 10 days after pulpal exposure of the mandibular first molar of normal rats and of those with methotrexate-induced neutropenia. The area of pulpal necrosis was measured. The neutrophil count in peripheral blood was determined, and their phagocytosis and chemotactic reaction were also examined. Statistical significance was examined by use of the two way analysis of variance. RESULTS: In untreated rats, G-CSF significantly (P < 0.05) increased the number of peripheral neutrophils and their chemotactic reaction, but did not affect pulpal inflammation. In methotrexate-induced neutropenic rats, the phagocytosis and migration of neutrophils reduced, and the area of pulpal necrosis enlarged. After the G-CSF injection, the decreases in neutrophil count and their functions significantly (P < 0.05) reversed, and the enlargement of pulpal necrosis inhibited. CONCLUSIONS: These findings indicate that G-CSF prevented the reduction in neutrophil function and reduced the pulpal necrosis observed in the neutropenic rats, and suggest that neutrophils defend against bacterial invasion in pulpal tissue.

Effect of low-temperature degradation on the mechanical and microstructural properties of tooth-colored 3Y-TZP ceramics.

The aim of the present study was to evaluate the effects of low-temperature degradation (LTD) induced by autoclaving on the mechanical and microstructural properties of tooth-colored 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP). In total, 162 disc-shaped 3Y-TZP specimens were prepared. Two-thirds of the specimens were shaded by either the infiltration or powder mixing methods while the remaining specimens were used without coloring. The specimens were autoclaved at 134 °C for 0, 10, and 100 h to induce LTD (n=18 for each group). Chemical compositions were analyzed with X-ray fluorescence spectroscopy. Biaxial flexural strength was measured using a piston-on-three-ball test. The surface fraction and penetration depth of the monoclinic phase were examined using X-ray diffraction and scanning electron microscopy, respectively. The tooth-colored 3Y-TZP specimens contained Fe2O3 and Er2O3 (infiltration technique), and Fe2O3 (powder mixing method) at concentrations of<0.5 wt%. The tooth-colored 3Y-TZP had higher strength than the non-colored material after 100 h of autoclaving. In terms of surface fraction and penetration depth, the generation of monoclinic phase was significantly lower in the tooth-colored 3Y-TZP than in the non-colored material. The tooth-colored 3Y-TZP possessed equivalent biaxial flexural strength to that of the non-colored material and higher resistance to LTD regardless of the coloring technique (infiltration technique or powder mixing method) when the coloring pigments were contained at concentrations used in the present study.

A prospective randomized trial of either famotidine or omeprazole for the prevention of bleeding after endoscopic mucosal resection and the healing of endoscopic mucosal resection-induced ulceration.

BACKGROUND: It has been reported that inhibitors of gastric acid secretion prevent bleeding after endoscopic mucosal resection for mucosal gastric neoplasm. However, uncertain whether an histamine2-receptor antagonist or proton-pump inhibitor is more effective. AIM: To evaluate prospectively the effectiveness of famotidine or omeprazole for ulcer management after endoscopic mucosal resection. METHODS: From July 2003 to October 2004, 57 patients were randomly assigned to famotidine or omeprazole for the management of endoscopic mucosal resection. Both drugs were given intravenously for the first 2 days, thereafter by mouth. The bleeding rates after endoscopic mucosal resection, the effects on the healing of endoscopic mucosal resection-induced ulceration, and cost-benefits were compared. RESULTS: Twenty-eight patients received famotidine and 29 received omeprazole. No significant difference was observed between the two groups in patient characteristics. The bleeding rates after endoscopic mucosal resection were not significantly different (18% vs. 14%) between the groups. Similarly, no differences were seen in the size of the endoscopic mucosal resection-induced ulceration at 1, 30 and 60 days after resection between groups. The total costs of anti-secretory agents demonstrated a significant cost-benefit to those treated with famotidine (10,420 yen vs. 17,782 yen). CONCLUSIONS: Famotidine is suggested as a better alternative to omeprazole for the management of endoscopic mucosal resection, as it showed a clear cost-benefit, and the healing results after endoscopic mucosal resection were similar for the two treatment strategies.

Relationships between IL-6 gene polymorphism, low BMD and periodontitis in postmenopausal women.

OBJECTIVE: IL-6 plays critical roles in bone resorption and the pathogenesis of periodontitis in both inflammation and alveolar bone loss. A negative correlation was observed between periodontitis and truncal bone mineral density (BMD) in postmenopausal women. The C allele carriers of a genetic polymorphism IL-6-572G/C have higher levels of serum IL-6 compared to G allele carriers. We investigated the possible effect of IL-6-572G/C polymorphism on the relationship between low BMD and periodontitis in postmenopausal women. SUBJECTS AND METHODS: A total of 300 postmenopausal Japanese women who lived in Yokogoshi area of Niigata City, Japan, participated in this study. Genomic DNA was extracted from peripheral blood. The IL-6-572G/C genotypes were determined by the restriction fragment length polymorphism method. Bone mineral density (BMD) of right femoral neck and serum bone metabolism markers were measured. Low BMD was defined to have the BMD<80% of the mean for young adults. Periodontal parameters at two sites per tooth were measured. RESULTS: Serum osteocalcin levels were significantly lower in the IL-6-572G/G genotype (p=0.025). In the -572G allele non-carriers, percentages of PPD≥4mm sites were significantly higher in low BMD group compared with the healthy control group (p=0.021). Logistic regression analysis revealed low BMD to be associated with periodontitis (Odds ratio=1.736, p=0.027) after adjusted with IL-6-572G carriage, age, serum albumin level. CONCLUSIONS: IL-6-572G/C polymorphism was not an independent risk factor of low BMD or periodontitis, but may affect the relationship between the two diseases in postmenopausal Japanese women.

The influence of low-temperature degradation and cyclic loading on the fracture resistance of monolithic zirconia molar crowns.

The present study analyzed the kinetics of low-temperature degradation (LTD) in zirconia, and evaluated the influence of LTD and cyclic loading on the fracture resistance of monolithic zirconia molar crowns. Bar-shaped zirconia specimens were divided into nine groups and autoclaved at 134°C for 0-200h to induce LTD. The surface fraction and penetration depth of the monoclinic phase were examined using X-ray diffraction and scanning electron microscopy. Monolithic zirconia molar crowns were prepared for crown fracture testing. The crowns were autoclaved for 0-100h (n=6) and cemented to dies. Six crown-die samples that were not autoclaved and six samples that were autoclaved for 100h were subjected to cyclic loading with a load of 300N for 240,000 cycles. All samples were tested in a load-to-failure test. The monoclinic fraction on the surface increased with autoclaving time and reached a plateau after 50h. The depth of the monoclinic phase increased without reaching a plateau. The fracture load of the crowns significantly decreased from 5683N (SD: 342) to 3975N (SD: 194) after 100h of autoclaving. Cyclic loading did not significantly affect the fracture resistance of the crowns in all cases. Kinetic analysis showed no linear correlation between the surface fraction and depth of the monoclinic phase after 50h of autoclaving. Even though LTD increased the monoclinic phase, resulting in lower strength, the fracture resistance of the monolithic zirconia crowns was still sufficient to withstand the loading conditions in the molar regions.

Factors contributing to the emulsification of intraocular silicone and fluorosilicone oils.

Silicone oil (SiO) and fluorosilicone oil (FSiO) are used as vitreous substitutes during retinal detachment surgery. Emulsification of these oils causes complications in oil-injected eyes. One factor contributing to emulsification is interfacial tension (gamma i) of the oils. In general, the lower the gamma i, the more easily the oils are emulsified. We measured the gamma i of SiO and FSiO by the ring method at 37 degrees C; corrected the measured values by the Harkins-Jordan table or the Zuidema-Waters equation; and found that the gamma i between the oils and liquefied bovine vitreous was low compared with the gamma i between the oils and water (eg, gamma i of 1000 centistokes [cs]SiO against liquefied vitreous and water was 16.0 and 42.8 dyne/cm, and that of 1000 cs FSiO was 14.7 and 38.7 dyne/cm, respectively). When SiO or FSiO and liquefied vitreous were shaken in a partially filled vial, both oils were emulsified regardless of viscosity and purity. However, when the vial was filled completely (a situation in which the hydrodynamic condition of the oils may be similar to that in the eye), SiO of 1000 and 12,500 cs and FSiO of 10,000 cs did not emulsify, although FSiO of 1000 cs did emulsify. SiO was less emulsified than FSiO of the same viscosity, possibly because the smaller density difference between SiO and intraocular fluids makes agitation difficult compared with FSiO. High viscosity of the oils restricted mechanical emulsification, which was not prevented by eliminating low-molecular-weight components of the oils. Residual catalysts may relate to spontaneous emulsification, which was observed occasionally with high-viscosity SiO in water.

Analysis and fractionation of silicone and fluorosilicone oils for intraocular use.

Silicone oil (SiO) and fluorosilicone oil (FSiO) are useful in difficult cases of retinal detachment surgery. Unidentified low-molecular-weight components (LMWC) and residual catalysts in SiO and FSiO have been implicated in the adverse reactions of the oils in the eye. The authors analyzed LMWC of SiO and FSiO using a gas chromatograph (GC) equipped with a 6-ft x 2-mm column packed with 3% SP-2250 and a flame-ionization detector. By commercially available standards and a homologous series plot, MD3M to MD23M (linear LMWC) and D4 to D30 (cyclic LMWC) were positively identified in commercial-grade 1000-centistokes (cs) SiO. Commercial-grade 12,500-cs SiO contained GC-detectable LMWC (up to MD28M and D30) at higher concentrations than commercial-grade 1000 cs SiO, although the weight percent of acetone-extractable LMWC (including those larger than MD28M and D30) was less in the former than in the latter. The GC-detectable LMWC in most medical-grade SiO were less than those in commercial-grade SiO. Tetramethylammonium siloxanolate (a residual catalyst) and tributylphosphine oxide (a heat-decomposition product of a polymerization catalyst) were tentatively identified in commercial- and medical-grade 12,500-cs SiO, respectively. Commercial-grade 1000- and 10,000-cs FSiO also contained LMWC, including F3 and/or F4 (cyclic LMWC). To eliminate LMWC from the oils, the authors developed a solvent fractionation method using acetone for SiO and hexane for FSiO. After continuous solvent extraction of SiO for 2 weeks and FSiO for 3 weeks, all measurable LMWC were eliminated from the oils.

Ocular toxicity of low-molecular-weight components of silicone and fluorosilicone oils.

Silicone oil (SiO) and fluorosilicone oil (FSiO) are injected into the vitreous cavity in difficult cases of retinal detachment surgery. SiO and FSiO contain linear and cyclic low-molecular-weight components (LMWC) that are thought to cause ocular toxicity. Using the purified oils (without LMWC) and some of the individual LMWC, the authors evaluated the relation of the LMWC to the short-term ocular toxicity of the oils. When octamethylcyclotetrasiloxane or other single small species of linear and cyclic LMWC of SiO were injected into the rabbit anterior chamber, severe inflammation and corneal edema were induced. The ocular responses to the single species of the LMWC of SiO decreased with an increase of the molecular weights. Cyclic LMWC of FSiO (a mixture of trimethyl-3,3,3-trifluoropropylcyclotrisiloxane and tetramethyl-3,3,3-trifluoropropylcyclotetrasiloxane) also induced inflammation and corneal edema. However, unpurified SiO and FSiO, as well as purified oils (via solvent fractionation), did not cause significant adverse ocular response, presumably because the amounts of LMWC (especially the smallest species) in the oils were relatively small. Using gas chromatography, the authors analyzed SiO and FSiO recovered from rabbit and human vitreous cavities up to 2 yr after injection. In most of the cases, the concentrations of LMWC in SiO decreased after injection. This is consistent with the possibility that LMWC diffused from the oils into the ocular tissues. The long-term effect of LMWC in intraocular SiO and FSiO has not been determined. However, diffusion of LMWC into ocular tissues may relate to the chronic ocular toxicity of the oils.

Effects of complexation between liposome and poly(malic acid) on aggregation and leakage behaviour.

The design and development of novel pH-sensitive liposomes were investigated to improve the release of liposome-encapsulated chemicals. Stable liposomes comprising of L-alpha-dipalmitoylphosphatidylcholine (DPPC) and poly(carboxylic acid) were prepared and characterized. Poly(malic acid) (PMLA) was chosen as a fusogen, because of its excellent biodegradability in physiological regions. Octyl groups introduced in the poly(malic acid) worked as anchors at the surface of the liposomes and made a remarkable contribution to complexing. The interaction between the liposomes and the polyacids was studied in terms of the change in size of the liposomes. The influences of molecular weight and amounts of polymer upon their characteristics, especially fusion, were discussed. The influences of pH change with respect to the association behavior of the liposomes such as aggregation and fusion were estimated by the particle size of the liposomes, turbidimetry of the solution and resonance energy transfer assay. From the results of these studies, it was shown that more tightly complexed liposomes aggregated and fused more positively with increasing acidity of the solution. The leakage of calcein entrapped in the inner aqueous phase of the liposomes increased with decreasing pH. The effect of pH on the liposome aggregation in a solution qualitatively paralleled that found in the leakage behavior.

Osteogenic response of the rabbit femur to a hydroxyapatite thermal decomposition product-fibrin glue mixture.

The effect of fibrin glue on the hardening process of hydroxyapatite thermal decomposition product (HATDP) was investigated in vitro. To study, in vivo, the effect of fibrin glue on osteogenesis, a mixture of HATDP with fibrin glue was injected into the left femurs of 20 rabbits, and HATDP without fibrin glue was injected into the right femurs. New bone formation was observed in the area of direct contact with the fibrin-containing mixture in the metaphysis at 2 weeks after injection in two of four femurs, but not in the fibrin-free group. At 4 weeks after injection, new bone formed a bridge between the mixture and the cortical bone in three of the four specimens. A parameter of osteogenesis (the affinity index) was calculated at 4, 12 and 24 weeks after injection. It was respectively 0.14+/-0.02, 0.49+/-0.12 and 0.44+/-0.05 for the fibrin-containing mixture, and 0.14+/-0.062, 0.44+/-0.15 and 0.49+/-0.04 for the control. A comparable but significant increase in the average affinity index was noted over 12 weeks in both the fibrin-containing and the fibrin-free HATDP. These findings indicate that fibrin glue accelerated the hardening of HATDP but did not inhibit the process of osteogenesis.

Assessment of heat and storage conditions on gamma-ray and electron beam irradiated UHMWPE by electron spin resonance.

Electron spin resonance (ESR) spectroscopic study was undertaken to explore the nature of any remaining radicals in ultra-high molecular weight polyethylene (UHMWPE) after irradiation with gamma-rays and electron beams to a dose of 25 KGy in air or N2 environment. The decay of radicals was studied by observing the ESR intensity change as a function of time. The following post-irradiation conditions were employed: (1) storage in air or N2 at 25 degrees C, and (2) heat treatment in air or N2 at 80, 100, and 120 degrees C for time intervals up to 8 h. The study suggests that radicals remaining trapped in the matrix of UHMWPE could be dramatically scavenged by heat treatment, independently of the atmosphere during irradiation and the heating process. The melting temperature and mechanical properties of irradiated UHMWPE under the experimental conditions employed were shown not to alter significantly by heat treatment, except in the presence of air.

Quantitative analysis of the resorption and osteoconduction process of a calcium phosphate cement and its mechanical effect for screw fixation.

The clinical application of calcium phosphate cements (CPCs) composed of tetracalcium phosphate and dicalcium phosphate anhydrous has been limited because of its longer setting time, so that we developed the CPC in which the setting time was shortened to approximately 10 min. Aiming at clinical application, we evaluated the histological response in the bone quantitatively and the biomechanical effectiveness of this substance. The CPC was implanted in the rabbit femoral condyle up to 52 weeks for histological evaluation. In mechanical testing, small cancellous screws were inserted into the condyle, both with and without augmentation with the CPC, and the pull-out strength was measured. The micro-computed tomography finding demonstrated that the cross-sectional area of the implanted CPC at 24 weeks was approximately two-thirds of the initial area. The amount of newly calcified bone around the CPC was significantly greater than that of the sintered hydroxyapatite. Histologically, the new bone was formed on the surface of the implanted CPC 1 week after the implantation and resorption of the CPC was evident at 3 weeks. The pull-out strength was enhanced significantly by augmentation with the CPC and the initial strength was maintained for a 6 week period. This CPC showed good osteoconductivity and was resorbed without adverse inflammation. Using the CPC as augmentation may be capable of useful treatment options in fractures with poor bone quality.

Characteristics of rat lateral hypothalamic neuron responses to smell and taste in emotional behavior.

Single unit activity in the lateral hypothalamus (LHA) of the rat was recorded while the animal learned to discriminate cue signals. Normally preferred potables (glucose, orange, or grape solution) or intracranial self-stimulation (ICSS) were used as rewards. Electric shock or tail pinch were used as aversive stimuli. The same behavior, licking, was the response required to either obtain the rewarding stimuli or avoid the aversive ones. For positive reinforcement a rat was rewarded with fluid or ICSS upon licking a spout presented in front of its mouth. In negative reinforcement experiments, an aversive stimulus, electric shock or tail pinch, was applied if the rat did not lick the spout. Solutions having smell only, taste only, or smell-plus-taste, were prepared from oranges or grape extract. Of 392 neurons analyzed, 256 responded differentially to rewarding and aversive stimuli, and 138 of these were tested with the 3 different solutions. Similar LHA neural responses occurred during actual drinking of the 3 kinds of solutions, as well as on recognition of the cue signal. Responses to smell only had shorter latency than responses to taste only. Neural activity in response to solutions that could be both smelled and tasted was the sum of activity in response to taste-only solutions plus that in response to smell-only solutions. Cue signal responses were rapidly acquired, usually within 2-5 trials, for both taste-only and smell-only solutions. The results indicate the integration of both taste and olfactory information by the same LHA neurons, and these neurons are involved in cue signal learning. Present results of LHA neuronal responses to taste and smell suggest that the intensity of gustation and olfaction may add together to enhance instinctive hedonic sensations. These neurons are involved in the formation of stimulus-reinforcement association in learning, and in elicitation of conditioned emotional responses.