RESUMEN
Objective To prepare a novel bioactive and degradable scaffold with mineralized collagenpolyose based composite by biomimetic synthesis for bone tissue engineering and explore the compatibility of osteoblast culturing on the scaffold. Methods Two kinds of polyelectrolyte were assembled on the surface of diatomite particles in order to adsorbe on nano-zirconia through opposite charges. Zeta potential,particle size and size distribution were compared before and after the modification of diatomite; IR was used to analysis molecular structure of functional group changes on the surface of diatomite particles, nano-composite powder morphology was observed by SEM. Results Two kinds of the polyelectrolyte were successfully assembled on the surface of diatomite powders. Particle size and size distribution were significantly reduced, d (0.5) reduce from 16.421 μm to 0.420 μm. SEM showed the dispersion of the modified diatomite was improved and had a good adsorption with nano-zirconia. Conclusion Layer-by-layer technique could enhance the dispersion of diatomite-based dental ceramic powders as well as a good adsorption of nano-composite ceramic powder.
RESUMEN
Objective:To evaluate the bio-mechanics of the cracked molars. Methods: A three dimensional finite element(3D-FEM) model of an upper first molar was constructed by Ansys 8.0 software. The model's cuspal inclination was shaped according to the mean value of the cuspal inclination in the cracked maxillary first molars and the intact ones respectively. The influence of cuspal inclination on the stress distribution was evaluated under different loads:Load of 600 N vertically applied to the occlusal surface of the model, or load of 200 N applied from three directions (vertically, at a 45?angle, horizontally). Results:For the model with the cuspal inclination of the cracked maxillary first molars, its maximum tensile stress, compressive stress and Von Mises stress were higher than those of the control models. The tensile stress and Von Mises stress increased with the increase of force direction and became to the highest under horizontal loads. The tensile stress was mainly distributed at the mediolingual cusp, centre groove and the palatal side of the cervical region. Conclusions: Under equivalent loads, the molar with bigger cuspal inclination suffers more unfavorable stress, which will magnify the occurrence of cracked tooth syndrome (CTS), and horizontal bite force may be a critical factor.