Chemical products for dental and dental-laboratory purposes, adhesive cement, impression, modelling, and doubling materials for dental and dental-laboratory purposes, agents for the surface treatment of teeth, namely etching and sealing agents, dental ceramic compositions and synthetic dental materials in the form of liquids, pastes or powders for producing and restoring crowns, bridges, prostheses, parts of prostheses, dental plates, material for blending and filling, adhesion promoting agents for dental and dental-laboratory purposes