Elasticity Of Dentin Research Articles

Synthesis and Characterization of MgPSZ-PMMA Composite by Sol-Gel Modification and Direct Foaming Technique Using Egg Whites

This study prepared Magnesium-Partially Stabilized Zirconia (Mg-PSZ) filler synthesis and direct foaming technique using egg whites, and impregnated by PMMA. The results were evaluated systematically by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). XRD results denote that the powder sample of MgPSZ was successfully formed with various crystal size of tetragonal and monoclinic phase. SEM and TEM observations revealed that nanoparticles MgPSZ were in spherical and long rounded shapes. Furthermore, SEM observation revealed that the direct foaming method were also successful in the formation of porous structures which favourable for impregnation process by PMMA. The use of egg whites as a polymer precursor in both methods demonstrates that porous specimens contained nanosized, predominantly tetragonal, Mg-PSZ powders were successfully synthesized. This shall yield an interesting prospect towards cheap, reliable, and biocompatible product to resemble the modulus elasticity of dentin.

Multiscale characterization of partially demineralized superficial and deep dentin surfaces

The objective of this study was to address the following question: 'Which properties are modified in partially demineralized surfaces, compared with non-demineralized dentin surfaces, following orthophosphoric acid-etching as performed in clinical procedures?'. For this purpose, the complementary techniques atomic force microscopy/spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and contact angle measurements were used to provide a multiscale characterization of the dentin substrate undergoing the acidic preconditioning designed to enhance wetting. Special attention was given to the influence of the etching pretreatment on the nanomechanical properties at different levels of dentin surfaces, in both dry and hydrated conditions. The four-sided pyramid model (extended Hertz contact model) proved to be accurate for calculating the apparent Young's modulus, offering new information on the elasticity of dentin. The modulus value notably decreased following etching and surface hydration. This study underlines that after the acid etching pretreatment the contribution of the nanomechanical, morphological, and physicochemical modifications has a strong influence on the dentin adhesion properties and thus plays a significant role in the coupling of the adhesive-resin composite build-up material at the dentin surface.

Ultrasonic monitoring of the effect of sodium hypochlorite on the elasticity of dentine

To determine the change in ultrasonic velocity of dentine after the application of 5% NaOCl. Twenty standardized plano-parallel dentine bars were divided into two groups. Dentine bars were wetted on only one surface. The test group (n = 10) was irrigated with 5% NaOCl, and the control group, (n = 10) with saline. Ultrasonic velocities before and after irrigation were compared to determine the change in the modulus of elasticity. Finally, dentine bars were loaded until failure in a 3-point bending test. Paired t-test and the mean of differences were used to assess the statistical significance between the groups. The mean ultrasonic velocity decreased by 1.4% after the application of NaOCl; no change was observed for saline. The mean velocity reduction of 49 m s⁻¹ was found to be highly significant (P = 0.004). The ultrasonically derived modulus of elasticity decreased by 2.6% compared to the initial value of 17.8 GPa. However, the observed reduction in elasticity derived from the 3-point bending test was not significant (P = 0.238). NaOCl reduced the ultrasonic velocity of dentine and the ultrasonically derived modulus of elasticity.

The relationship of dental cements, pins, and retention

D I. ms, which are retained by the elasticity of dentin, may traumatize the tooth into which they are placed.‘, ” Although cemented pins have a smaller potential for causing trauma, they also have a lower retentive capacity.“, 5 The authors have recently reported some inherent effects of cement type and thickness upon retention of threaded pins.” The foregoing’ work considered only one threaded pin design. These pins were installed into precise channels prepared with a drill press. This led to a consideration of clinically oriented techniques to determine the optimal retention of cemented pins. The purpose of this study was to evaluate the interactions among various pin types, cement types, and channel sizes to determine the most retentive combinations.

The chilled silver cone as a root canal filling material

In an effort to improve the existing silver cone method of filling root canals, we have presented a chilled silver cone technique that relies on the malleability of silver, on silver's contraction and expansion with temperature change, and on the elasticity of dentine. A preliminary in vitro study was conducted on forty-two freshly extracted teeth. In Phase I fitted silver cones were cooled with Freon to a possible -60° C., causing a decrease in cone diameter of at least 0.01 mm. The chilled cones were cemented into canals prepared through the apex. By measuring the distance that the cones moved beyond the apex, we determined that 0.5 mm. was the amount that could be cut off the apical tip of a fitted silver cone and still allow the chilled cone to seat to the original working distance in the sealer-coated canal. Phase II consisted of a practical demonstration of the chilled silver cone technique in conventionally prepared root canals. The silver cones were fitted, and 0.5 mm. was removed from the apical tip of the cones; they were then cooled with Freon and seated to the working distance in the sealer-lined canals. Upon warming to body temperature, the silver cones apparently expanded against the walls of the root canals, probably providing a more adequate seal without causing fracture of the teeth.

永久歯の硬度と彈性

Hardness and elasticity of enamel and dentin of healthy permanet teeth from 6 to 7 by Mohs were measured by means of Dulometer, and the results were summarized as follows. Difference in hardness in diffent parts of a tooth was readily perceived. The difference seems to be based upon the degree of thickess of tooth's hard tissue. In dentin, local hardness difference was smaller than in enamel, and the difference became smaller toward the posterior teeth, which was inverse in enamel. Elasticity of dentin is also higher in posterior teeth than in anterior teeth, and the individual diviations are greater than those in enamel.