Jerzy Detyna

Do Mechanical and Physicochemical Properties of Orthodontic NiTi Wires Remain Stable In Vivo

Introduction and Aim. Exceptional properties of the NiTi archwires may be jeopardized by the oral cavity; thus its long-term effect on the mechanical and physiochemical properties of NiTi archwires was the aim of work. Material and Methods. Study group comprised sixty 0.016 × 0.022 NiTi archwires from the same manufacturer evaluated (group A) after the first 12 weeks of orthodontic treatment. 30 mm long pieces cut off from each wire prior to insertion formed the control group B. Obeying the strict rules of randomization, all samples were subjected to microscopic evaluation and nanoindentation test. Results. Both groups displayed substantial presence of nonmetallic inclusions. Heterogeneity of the structure and its alteration after usage were found in groups B and A, respectively. Conclusions. Long-term, reliable prediction of biomechanics of NiTi wires in vivo is impossible, especially new archwires from the same vendor display different physiochemical properties. Moreover, manufacturers have to decrease contamination in the production process in order to minimize risk of mutual negative influence of nickel-titanium archwires and oral environment.

Stochastic Models of Particle Distribution in Separation Processes

Separation processes are important in industry. The understanding of the fundamentals of granular separation on sieve surfaces is incomplete. It results from the fact that granular matter is a system of many particles interacting via short ranged repulsive and dissipative forces, both normal and tangential to the surface of contact. We can try describing the separation processes by the Newton equations in a deterministic way. However, the models contain quite a lot of simplifications and therefore such models are not very useful. We perceive separation process as process of random character. Therefore, we can use statistical models to describe the separation process. In this article I presented the methodology of modelling and the way of using selected probability density functions. Parameters of these functions were appointed on the basis of regressive methods.

Structure and Mechanical Properties of Soft Tissues during Selected PathologicalProcesses

Pathological process often modifies the structure of the soft tissue and can lead changes of mechanical properties. The regularity of this relationship has already been used in the elastography and currently it is applied in medical diagnostic. Tissue stiffness can be identified by a quick measurement but more accurate details can be obtained only by biopsy. Studies, presented in a scientific literature, focus only on pathological stiffness or consider only changes in biochemical structure. These researches revealed two very important components of those modifications – elastin and collagen. Soft tissues are multicomponent, inhomogeneous and anisotropic structures. Their functionality depends on complicated processes on molecular level. Probably the individual components of the tissue can effect on each other. They may promote creation of processes, which can participate in modifications of elasticity. For this reason, it is very important to relate changes on the structural level with mechanical properties. This information can be very helpful in diagnosis and treatment of soft tissue disease.

In-vivo corneal pulsation in relation to in-vivo intraocular pressure and corneal biomechanics assessed in-vitro. An animal pilot study

ABSTRACT The aim was to ascertain whether the characteristics of the corneal pulse (CP) measured in‐vivo in a rabbit eye change after short‐term artificial increase of intraocular pressure (IOP) and whether they correlate with corneal biomechanics assessed in‐vitro. Eight New Zealand white rabbits were included in this study and were anesthetized. In‐vivo experiments included simultaneous measurements of the CP signal, registered with a non‐contact method, IOP, intra‐arterial blood pressure, and blood pulse (BPL), at the baseline and short‐term elevated IOP. Afterwards, thickness of post‐mortem corneas was determined and then uniaxial tensile tests were conducted leading to estimates of their Youngs modulus (E). At the baseline IOP, backward stepwise regression analyses were performed in which successively the ocular biomechanical, biometric and cardiovascular predictors were separately taken into account. Results of the analysis revealed that the 3rd CP harmonic can be statistically significantly predicted by E and central corneal thickness (Models: R2 = 0.662, p < 0.005 and R2 = 0.832, p < 0.001 for the signal amplitude and power, respectively). The 1st CP harmonic can be statistically significantly predicted by the amplitude and power of the 1st BPL harmonic (Models: R2 = 0.534, p = 0.015 and R2 = 0.509, p < 0.018, respectively). For elevated IOP, non‐parametric analysis indicated significant differences for the power of the 1st CP harmonic (Kruskal–Wallis test; p = 0.031) and for the mean, systolic and diastolic blood pressures (p = 0.025, p = 0.019, p = 0.033, respectively). In conclusion, for the first time, the association between parameters of the CP signal in‐vivo and corneal biomechanics in‐vitro was confirmed. In particular, spectral analysis revealed that higher amplitude and power of the 3rd CP harmonic indicates higher corneal stiffness, while the 1st CP harmonic correlates positively with the corresponding harmonic of the BPL signal. HIGHLIGHTSIn‐vivo corneal pulse (CP) is linked to in‐vitro corneal biomechanics.Higher power of the 3rd CP frequency harmonic indicates increased corneal stiffness.Elevated intraocular pressure differentiate spectral distribution of CP signal.