Machinability of high-speed enamel cutting with carbide bur.

The cutting of tooth enamel using a high-speed air-turbine handpiece and carbide bur is a key procedure in oral surgeries, such as the minimally invasive extraction. However, presently little is known about the cutting mechanics and material removal mechanism related to tooth enamel machinability. In this study, the machinability of high-speed enamel cutting with carbide bur is studied by a computer-aided numerical control system. The dynamic cutting forces of enamel of the occlusal, buccal/lingual, and proximal surfaces were measured by the force measuring system. The force ratio, cutting torque, rotating speed, specific cutting energy, and bur wear were analyzed. The microstructure of enamel and carbide burs was observed by the scanning electron microscope, and the relationship between enamel microstructures and machinability was further analyzed. The results show that during the high-speed enamel cutting with carbide bur, the chip thickness is on the nano-scale, and the plastic deformation of the machined surface is obvious. With increased material removal rate, the cutting force, torque, specific cutting energy, and bur wear increases accordingly, whereas the rotating speed decelerates (p < 0.05). The different angles between the cutting direction and the axial direction of the enamel rods give rise to the large differences in the cutting mechanics and mechanism of the proximal, buccal/lingual, and occlusal surfaces of the teeth. When the cutting direction is parallel, vertical, and oblique 45° to the axial direction of the enamel rods, the force required for material fracture and crack propagation increases, and the cutting force increases as a consequence. Parallel and oblique 45° cutting are the main modes of tooth segmentation in the minimally invasive extraction. In comparison with the parallel cutting mode, the cutting force, torque, and cutting ratio of the oblique 45° cutting mode can be significantly increased, and the tool wear is obviously accelerated. This is the lowest priority in segmentation surgery, hence the problems of overload and temperature rise need to be considered. The cutting mechanics and cutting mechanism obtained in this study will provide scientific process guidance for dental cutting operations with the air-turbine handpiece driving bur.

Predictive value of the surgical pleth index for the hemodynamic responses to trachea intubation and skin incision.

Surgical pleth index (SPI) has been widely investigated in assessing the nociceptive level. The aim of this study was to investigate the relationship between SPI level and patient responses to trachea intubation and skin incision. A total of 40 patients undergoing open abdominal general surgery were recruited for analyses. The patients were monitored with electrocardiogram, non-invasive blood pressure, SpO2, invasive blood pressure and SPI before anesthesia induction. Anesthesia was induced with midazolam, propofol, sufentanil and rocuronium and maintained with sufentanil and sevoflurane. Blood pressure, heart rate and SPI were recorded for analyses during the peri-intubation and peri-incision periods. A receiver operating characteristic (ROC) curve analysis was performed to analyze the predictive value of blood pressure, heart rate (HR) and SPI for hemodynamic responses for trachea intubation and skin incision. SPI had a similar changing trend to systolic blood pressure (SBP) and diastolic blood pressure (DBP). The SPI level was linearly correlated with SBP, DBP and HR. SPI increased significantly after intubation and incision in patients with positive but not negative responses to intubation and incision. The ROC analysis showed that only SBP level is predictive of intubation responses. These data suggested that SPI elevated under the noxious stimulation by intubation and incision, but it was not predictive of the hemodynamic responses to intubation and incision.

Effects of local delivery of bFGF from PLGA microspheres on osseointegration around implants in diabetic rats.

OBJECTIVE: Diabetes mellitus may impair bone healing after dental implant placement. The objective of this study was to evaluate the effects of the local delivery of basic fibroblast growth factor (bFGF) from poly(lactide-co-glycolide) (PLGA) microspheres on osseointegration around titanium implants in diabetic rats. STUDY DESIGN: The bFGF-PLGA microspheres were prepared by the W/O/W double-emulsion solvent evaporation method. A total of 20 rats were used to create diabetic animal models by giving them a high-fat and high-sugar diet and a low-dose streptozotocin intraperitoneal injection. Titanium implants were planted into the tibias of the diabetic rats and into 10 normal rats. Microspheres were loaded on the surfaces of the implants in the bFGF intervention group before they were placed into the rats. After 4 or 8 weeks, the tibias containing the implants were removed and embedded with resin. Uncalcified tissue slices were prepared to compare osseointegration. RESULTS: At 4 weeks, the bone-implant contact rate in the diabetic control group was less than that in the control group and the bFGF intervention group (P < .05). At 8 weeks, the results among the 3 groups were similar to those at 4 weeks. CONCLUSIONS: The local delivery of bFGF from PLGA microspheres into areas around titanium implants may improve osseointegration in diabetic rats.

Remote ischemic preconditioning protects neurocognitive function of rats following cerebral hypoperfusion.

BACKGROUND: Protection of remote ischemic preconditioning on neurocognitive function caused by bilateral common carotid artery occlusion has been investigated in rats. MATERIAL/METHODS: Thirty-six male Sprague-Dawley rats were divided into 3 groups - control group (Group C, n=12), bilateral carotid arteries occlusion group (Group B, n=12) and remote ischemic precondition group (Group P, n=12). In Group P, remote ischemic preconditioning (RIPC) was performed on the right femoral artery with 3 cycles (10 min) of occlusion/perfusion. After 3 cycles of preconditioning, bilateral carotid arteries were occluded immediately for 60 min. In Group B, ischemic insults were conducted without RIPC. Sham surgeries were performed in Group C. Evaluation of memory and learning capacity was performed on days 5-8 after surgery by Morris water maze testing of spatial learning capacity (n=6 for each group). Apoptosis of cells in the hippocampus region was determined by TUNEL tests and Bcl-2 at this region was determined by ELISA 24 h and 9 days after vessel occlusion (n=6 for each group). RESULTS: Neurocognitive tests showed that latency time was significantly longer in Group B than in Group P on day 7 (p=0.016) and day 8 (p=0.036). Moreover, frequency of platform crossings was significant less in group B than in the other 2 groups on day 9. Bcl-2 level was significantly increased in the hippocampal region of rats in Group P on days 1 and 9 after vessel occlusion. TUNEL test showed that apoptosis could be observed at 24 h after occlusion in Group B, but not in Group P and Group C. No apoptosis was observed on day 9. CONCLUSIONS: Our results suggest that RIPC can protect neurocognitive function of rats after bilateral carotid occlusions, and that Bcl-2 may play an important role in this protective effect.

Seasonal dynamics of wintering waterbirds in two shallow lakes along Yangtze River in Anhui Province.

The shallow lake wetlands in the middle and lower Yangtze River floodplain are important wintering and stopover habitats for migratory waterbirds on the East Asia-Australia Flyway. With increasing fishery practices in recent years, however, the wetlands have deteriorated significantly and now threaten wintering waterbirds. To gain insight into the influence of deteriorating wetlands on waterbirds, we conducted a survey of wintering waterbird species, population size, and distribution across 11 belt transects in Caizi Lake and Shengjin Lake, two shallow lakes along the Yangtze River in Anhui Province from November 2007-April 2008 and from November 2008-April 2009, respectively. The impacts of different fishery patterns on the distribution of waterbirds were also analyzed. A total of 43 waterbirds species belong to 7 orders of 12 families were counted during the surveys, of which 38 were found in Caizi Lake with a density of 8.2 ind./hm(2), and 42 in Shengjin Lake with a density of 3.5 ind./hm(2). Geese (Anser cygnoides), bean geese (Anser fabalis), tundra swan (Cygnus columbianus), and dunlin (Calidris alpina) were the dominant species in the two shallow lakes. Species number and individual assemble reached maximum at the end of December and in early January of the following year, without coincidence of the largest flock for different ecological groups. Based on waterbird diversity across the 11 belt transects and the fishery patterns, habitats could be divided into three groups. Gruiformes, Anseriformes and Charadriiformes had relatively higher densities in the natural fishery zones and lower densities in the cage fishery zones; whereas, the density of Ardeidae showed little change across all lake zones. It is important to develop sustainable fishery patterns in shallow lakes along the middle and lower Yangtze River floodplain to better protect resources of wintering waterbirds.

Synthesis, characterization, DNA-binding and antiproliferative activity of Nd(III) complexes with N-(nitrogen heterocyclic) norcantharidin acylamide acid.

Three novel complexes [Nd(L)(NO3)(H2O)2].NO(3).2H2O (HL1 = N-pyrimidine norcantharidin acylamide acid, C12H13N3O4; HL2 = N-pyridine norcantharidin acylamide acid, C13H14N2O4; HL3 = N-phenyl norcantharidin acylamide acid, C14H15NO4) were synthesized. HL1, HL2 and HL3 are the ligand of complex(1), complex(2) and complex(3), respectively. Their structures were characterized by elemental analysis, conductivity measurement, infrared spectra and thermogravimetric analysis. The DNA-binding properties of the complexes have been investigated by fluorescence spectroscopy and viscosity measurements. The results suggest that the complexes can bind to DNA by partial intercalation. The liner Stern-Volmer quenching constant Ksq values are 3.3(+/-0.21)(1), 1.7(+/-0.19)(2) and 0.9(+/-0.04)(3), respectively. Complex (1) and (2) have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity indicates that complex(1) has strong antiproliferative ability against the SMMC7721 (IC50 = 131.7 +/- 23.4 micromol x L(-1)) and A549 (IC50 = 128.4 +/- 19.9 micromol x L(-1)) cell lines. The inhibition rates of complex(2) (IC50 = 86.3 +/- 11.3 micromol x L(-1)) are much higher than that of NCTD (IC50 = 115.5 +/- 9.5 micromol x L(-1)) and HL2 (111.0 +/- 5.7 micromol x L(-1)) against SMMC7721 cell lines.

8-Phenyl-10-oxa-8-aza-tricyclo-[4.3.0.1]decane-7,9-dione.

The reaction of aniline with norcantharidin produced the imide title compound, C(14)H(13)NO(3), which shows no significant hydrogen bonds in the crystal structure. The dihedral angle between the phenyl and pyrrolidine rings is 48.48 (6)°.

catena-Poly[[diaqua-nickel(II)]-µ-7-oxabicyclo-[2.2.1]heptane-2,3-di-carboxyl-ato].

In the crystal structure of the title compound, [Ni(C(8)H(8)O(5))(H(2)O)(2)](n), the Ni(II) cation is in a Jahn-Teller-distorted octahedral coordination environment binding to two O atoms from water molecules, the bridging O atom of the bicycloheptane unit, two carboxylate O atoms from different carboxylate groups and one carboxylate O atom from a symmetry-related bridging ligand. The crystal structure is made up from layers propagating parallel to the bc plane.