Effects of compressive loading on biomechanical properties of disc and peripheral tissue in a rat tail model.

Intervertebral disc degeneration induced by mechanical compression is an important issue in spinal disorder research. In this study, the biomechanical aspect of the rat tail model was investigated. An external loading device equipped with super-elastic TiNi springs was developed to apply a precise load to the rat tail.

The most appropriate position and number for absolute anchorages for orthodontic tooth movements.

Absolute anchorages proved to be very effective for orthodontic tooth movements. We used a 3D digitizer to record each tooth on pre-treatment diagnostic and post-treatment predictive setup models and then 3D coordinate system conversion was performed to make the coordinate values comparable. An arithmetic calculation of vector and moment based on the orthodontic forces and the tooth displacement under preliminary premises undertaken to decide the most favorable position and number for absolute anchorages.

[The investigation of the testing method on fracture toughness of dental adhesive resins].

Objective: The testing method for mode I fracture toughness (GIC) of dental adhesive resins was investigated.

Methods: The dental adhesive resins were placed between two Co-Cr alloy plates to make up test specimen, so test specimen had a metal/adhesive resin/metal construction. The category of adhesive resins, the dimensions of test specimen and testing speed were used as the variants.

In vitro change in mechanical strength of beta-tricalcium phosphate/copolymerized poly-L-lactide composites and their application for guided bone regeneration.

Novel composites of bioactive beta-tricalcium phosphate [Ca(3)(PO(4))(2)] and biodegradable copolymerized poly-L-lactide (CPLA) were prepared by a heat-kneading method. The mechanical and chemical changes of the composites were evaluated in vitro by soaking in physiological saline and Dulbecco's phosphate buffered saline. When soaked in physiological saline, the 3-point mechanical strength decreased rapidly from 60 to 30 MPa in the initial 4 weeks and then gradually reached a plateau; the initial decrease in the mechanical strength was ascribed to the dissolution of beta-tricalcium phosphate from the surface.

Development of an orthodontic simulator for measurement of orthodontic forces.

In this research we developed an orthodontic simulator for analysis of orthodontic forces distribution in the case of the continuous arch technique. In order to take into account vertical force, besides horizontal force and occlusogingival moment on instrumented artificial tooth, tooth root was designed as a ring load cell. Fixing each artificial tooth onto combined mechanical stages enabled variation of tooth anteroposterior position and inclination related to occlusal plane.

Fatigue behavior of the zinc-phosphate cement layer.

Purpose: Fatigue behavior of luting cement film between model fixed partial dentures (FPD) and their dies was investigated to gain a better understanding of the mechanical properties of zinc-phosphate cement.

Materials And Methods: Fifty-six brass dies were made, half of them with grooves and half without grooves. A cantilever FPD for each die was cast in Au-Pd-Ag alloy.

[Mechanical behavior of the cement layer of a cast crown--effect of the mechanical properties of casting alloy].

Experimental crowns with uniform thickness at their axial surfaces were made of dental casting gold-silver-palladium alloy (12% gold) and dental casting gold alloy (Type IV). They were cemented on model teeth for abutment and their deformations under applied loads were measured with strain gages. The effect of axial metal thickness on the crown's rigidity and the cement fracture strength were examined.

Deformation of restoration and fracture of luting cement film.

Objectives: Functional occlusal loading can generate complicated stresses in the luting cement film between a restoration and its abutment. Such stresses may lead to cement fractures, which can promote cement dissolution and induce clinical problems. The purpose of this study is to determine the function of the cement film under loading, and to clarify the relationship between the deformation of the restoration and the cement fractures.

Surface strain on crown and luting cement fractures.

This study investigated fractures of the cement layer between a crown and a die. Model crowns were luted on dies with zinc phosphate cement and various magnitudes of load were applied. Surface strain on the crown was measured using strain gauges.

Magnetic resonance imaging and pathologic studies on lateral fluid percussion injury as a model of focal brain injury in rats.

In this study, morphologic changes in brain lesions initiated by moderate lateral fluid percussion injury in rats were investigated chronologically using high-resolution magnetic resonance imaging (MRI) and histopathologic methods. Rats were subjected to moderate fluid percussion injury (average 2.80 +/- 0.

Tensile behaviour of fibroblasts cultured in collagen gel.

An in vitro morphological study on the relation of the stress field and the orientation of cells with the use of the time lapse video recording system was carried out. Specimens of thin collagen gel membrane, within which cells are proliferating, were examined under various mechanical conditions. Cell stretching, cell orientation, cell migration, cell proliferation and generation of tensile stress in collagen gel were recorded.

Changes in lCBF, morphology and related parameters by fluid percussion injury.

We investigated the pathophysiological and morphological responses of anaesthetized rats to fluid percussion brain injury generated by an original midline fluid percussion injury device. Following different grades of trauma, lCBF was measured continuously in the right parietal cortex through a burr hole using laser Doppler flowmeter, and physiological parameters were monitored. Pathological changes also were evaluated microscopically.

An approach to computer aided porcelain forming system.

To examine a new concept for computerized production of dental prostheses, an experimental porcelain forming system was devised. Unlike other dental CAM systems, the system is intended to form porcelain much as human technicians do. The system builds up an object by alternately applying water and droplets of porcelain powder.

[Mechanical analysis of the denture bases using the photoelastic-coating method. 2. Upper complete denture bases under uniform bending moment load].

Deformation of the anterior teeth and palatal regions on upper complete dentures was investigated using the photoelastic coating method and strain gages. In this experiment, an uniform-moment bending load method was employed to simulate the occlusal situation, and the distribution of strain in epoxy resin, stainless swaged and Co-Cr alloy cast dentures were measured and analyzed. The 030-series reflection polariscope is compact and lightweight with its main components consisting of two polarizer/quarter-wave-plate assemblies attached to a common frame.

[Mechanical analysis of the denture bases, using the photoelastic-coating method. 1. Influence of the coating on mechanical properties of the test denture].

The anterior palatal area may be related with the flexural rigidity and bending strength of the upper complete dentures. Therefore, the deformation of this area should be measured widely and continuously when new materials were applied to the dentures. The influence of the photoelastic coating on the mechanical properties of the upper complete dentures was investigated, prior to the measurement of surface strains on the denture bases by the photoelastic coatings.

[Experimental HFV apparatus utilizing a mechanical vibration].

We make an experimental HFV apparatus in which the mass-spring system is utilized as the vibration actuator. When this apparatus is operated near the characteristic frequency of the mechanical vibration system, the efficiency is quite good and trivial motor is enough to realize the vibrating flow for the experimental ventilator. In this paper we first investigate the flow-frequency relations and found that above the characteristic frequency of the mechanical vibration system the oscillating volume of flow is nearly constant.