Construction of Customized Palatal Orthodontic Devices on Skeletal Anchorage Using Biomechanical Modeling.

Orthodontic implants have been developed for the implementation of skeletal anchorage and are effectively used in the design of individual orthodontic devices. However, despite a significant amount of clinical research, the biomechanical aspects of the use of skeletal anchorage have not been adequately studied. The aim of this work was to numerically investigate the stress-strain state of the developed palatal orthodontic device supported by mini-implants. Four possible options for the placement of mini-implants in the bone were analyzed. The effect of a chewing load of 100 N on the bite plane was investigated. The study was carried out using biomechanical modeling based on the finite element method. The installation of the palatal orthodontic device fixed on mini-implants with an individual bite plane positioned on was simulated. The dependence of equivalent stresses and deformation changes on the number and location of the supporting mini-implants of the palatal orthodontic device was investigated. Two materials (titanium alloy and stainless steel) of the palatal orthodontic device were also investigated. The choice of a successful treatment option was based on the developed biomechanical criteria for assessing the surgical treatment success. Application of the criteria made it possible to estimate the stability and strength of fixation of each of the considered mini-implants installation options. As a result, options for the mini-implants optimal placement were identified (the first and the fourth which provide distributed front and side support of the device), as well as the preferred material (titanium alloy) for the manufacture of the palatal orthodontic device.

Kinetic limit of heterogeneous melting in metals.

The velocity and nanoscale shape of the melting front are investigated in a model that combines the molecular dynamics method with a continuum description of the electron heat conduction and electron-phonon coupling. The velocity of the melting front is strongly affected by the local drop of the lattice temperature, defined by the kinetic balance between the transfer of thermal energy to the latent heat of melting, the electron heat conduction from the overheated solid, and the electron-phonon coupling. The maximum velocity of the melting front is found to be below 3% of the room temperature speed of sound in the crystal, suggesting a limited contribution of heterogeneous melting under conditions of fast heating.

Effect of pressure relaxation on the mechanisms of short-pulse laser melting.

The kinetics and microscopic mechanisms of laser melting of a thin metal film are investigated in a computational study that combines molecular dynamics simulations with a continuum description of the laser excitation and subsequent relaxation of the conduction band electrons. Two competing melting mechanisms, homogeneous nucleation of liquid regions inside the crystalline material and propagation of melting fronts from external surfaces, are found to be strongly affected by the dynamics of the relaxation of the laser-induced pressure.