Unfilled Cavities Research Articles

Evaluation of the effect of heterologous type I collagen on healing of bone defects

Purpose: The purpose of this investigation was to evaluate the effect of type I collagen on the healing of bone defects both experimentally and clinically. Materials and Methods: In the experimental study, 16 adult male rabbits were divided into 2 groups: a collagen group and a control group. After the induction of general anesthesia with intraperitoneal ketamine, the anterior surfaces of tibias of the rabbits were surgically exposed, and a hole 4 mm in diameter was made in each tibia. In the collagen group, the defects were filled with type I collagen. The unfilled defects of the other animals were used as controls. During the study, the serum alkaline phosphatase activity of the rabbits, and radiopacity changes in the radiographs of the tibias of the rabbits were evaluated. The rabbits were killed on the 35th day, and histologic sections of the tibias were prepared. The clinical study was carried out on periapical defects in a total of 15 patients who underwent apicoectomy. After the surgical procedure, the osseous defects in periapical regions of 7 patients were filled with type I collagen. The unfilled cavities of the other patients were used for control purposes. The patients were evaluated clinically and radiographically in the postoperative period. The data were analyzed by Student's t-test and Mann-Whitney U test. Results: In the experimental study, there was an increase in radiopacity corresponding with the serum alkaline phosphatase activity, and there were statistically significant differences between the control and collagen groups both radiologically and biochemically on the 14th and 28th days of the study. In the clinical study, the control cavities filled with a tissue of normal bone density in about 5 months, but the collagen cavities filled in 3 months. Conclusions: It was determined that heterologous type I collagen provides a more rapid regeneration of bone defects. © 2002 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 60:541-545, 2002

96/01311 Hydrothermal alteration of bazhenite to aliphatic hydrocarbons, car☐ylic acids and other oxygen-containing compounds (letter)

Complex heterogeneous reservoir exhibits special characteristics, such as multiple storage types, wide range of storage sizes, complicated storage combinations, and various flow behaviors. Multi-continuum model is needed to rigorously simulate this type of reservoir. However most reservoir simulators use dual porous media model, and the theory of the models is mainly focused on matrix-fracture system. Therefore when porous media is more complex than matrix-fracture system, such software cannot be utilized to simulate these reservoirs directly. Some studies have been proposed to solve the problem, but most of them are either at the theoretical level or cannot been used widely in the simulation softwares. The goal of this paper is not to develop new numerical simulation software, but to obtain appropriate ways to improve performance of current simulation software for complex reservoir.Our approach is theoretically based on multi-continuum seepage theory. By comparing the microscopic seepage model and multi-continuum seepage model, we find that the conventional theory becomes improper because of the absence of an important restriction to the interporosity flow. In the conventional way, an N-multiple flow model always can be established based on N types of continuous media. In fact, one more restrictive condition needs to be added to make it valid: all the crossflow between any two types of continuum can be simplified into a source or sink terms in the seepage model. Consequently, the multiplicity of the seepage model is always less or equal to the number of the continuum types. In addition, because different type of dual-medium has different crossflow, it is required to construct their crossflow models respectively and derive corresponding calculation formula.Several steps developed in this paper are as follows on the basis of multi-continuum theory and the restrictions appended: First, reservoir storage is categorized into continuous and non-continuous media according to storage scale characteristics, distribution and intensity. In general, small cavities, small fractures, and pores in the rock are continuous while large-scale fractures, big cavities or caves are non-continuous. The whole reservoir is therefore classified into continuum region and dis-continuum region. Second, in the continuum region, multi-media model and its multiplicity are determined by using the new theory proposed in this paper. Third, calculation formulae are constructed for each type of crossflow. This research takes fractured vuggy reservoirs as an example. A new calculation for the flux transfer is derived for such fracture-vug dual-porosity system. Forth, in the discrete region, flow in a filled non-continuous medium is described by Darcy's law and free flow in large unfilled cavities or caves follows Navier-Stokes equation and an approximate approach to using Darcy flow simulation is provided. Lastly, this paper introduces the methods how to simplify multi-media into two media and how to simulate the complex reservoir by using the existing simulators.The proposed method is applied to a naturally fractured carbonate reservoir with cavities in the Tarim Basin in China. The simulation results illustrate the production mechanisms of reservoir development using water flooding, including water injection and shut-in, stairs-shaped line of water cut with time, high production with low water cut for long time.

Evaluation of tricalciumphosphate/ hydroxyapatite cement for tooth replacement: an experimental animal study

A calciumphosphate cement, consisting mainly of tricalciumphosphate (85% α-TCP and 15% β-TCP), was inserted in 16 surgical defects created in the tibia of goats. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) showed that after 3 months of implantation the α-TCP was transformed to hydroxyapatite (HA). Histological evaluation revealed that the presence of cement stimulated the ingrowth of bone compared with unfilled cavities. Active resorption and remodelling of cement particles was observed. The cement did not evoke an inflammatory reaction. At 6 months after implantation no further changes in the composition of the cement occurred. All remaining material was surrounded by mature bone.

Development of a computer code to predict cooling of die and billet in forging

A hot billet in contact with relatively cold dies undergoes rapid cooling in the forging operation. This may give rise to unfilled cavities, poor surface finish and stalling of the press. A knowledge of billet-die temperatures as a function of time is therefore essential for process design. A computer code using finite difference method is written to estimate such temperature histories and validated by comparing the predicted cooling of an integral die-billet configuration with that obtained experimentally.

Some factors influencing filling of multiple cavities during injection molding

AbstractThe rate of filling of multiple cavities positioned along a runner is of significant importance to injection molders. Unevenness in filling can lead to unfilled cavities near the end of the runners or to long cycle times. The effects of gate dimension and shape, cavity capacity and injection rate on injection pressure for an isothermal Newtonian fluid are discussed in detail. Extension to power‐law fluids and nonisothermal viscosity is outlined.

Full-scale testing of the resistance to water penetration of seven cavity fills

The cavity fills were installed in conventionally built houses, and subjected to a wetting regime which represented severe weather conditions which occur occasionally in Britain. It was found that some water crossed a few of the unfilled cavities under the test conditions but that filling the cavities always reduced the water resistance of the wall. The performance of the fills differed considerably in this respect but the results showed that some fill materials permitted only little water to cross in the test programme.

The effect of scleral grafts in osseous defects in rabbits.

Scleral grafts were implanted into bony cavities in the tibiae of 8 rabbits for periods of two to six weeks. By four weeks, control unfilled cavities were full of woven bone, which had been remodelled into mature compact bone by six weeks. Healing of cavities filled with scleral allografts was delayed and they were not filled with woven bone until six weeks. There was no evidence of osteogenetic induction of sclera. Human heterografts caused marked rejection responses.

Pseudo-discoloration of plastic fillings.

The purpose of the present work was to demonstrate whether marginal discoloration of plastic fillings may cause an apparent discoloration of the whole filling. The synthetic resins used in the investigation were Addent XV and Sevriton Simplified. Cavities were cut in teflon and plexiglas. Marginal discoloration was produced either by painting the unfilled cavities with a colored varnish or by intermittent vacuum-treatment in Indian ink of hardened, polished fillings. Fillings discolored only at the margin showed a marked apparent discoloration of the whole filling. On removal from their respective cavities, these fillings reverted to a color indistinguishable from that of the control fillings.Marginal discoloration can occur only where there are marginal gaps. Good adaptation between filling material and tooth is thus of great importance for the esthetic properties of the estoration.