The work present in this book deals with preparation and characterization of new complexes which contain some transition ions ( Sc3+, Ti3+, V5+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, and Cu2+) and non transition metal ions ( Ba2+, Ca2+, Zn2+, Cd2+, and Sn2+) with ligands ( Thymol, Vanillin, o, m, p-Cresol, Salicylic acid, Methyl salicylaste, Guaiacol, Eugenol, and Menthol). The prepared complexes subsequently tried as dental filling passing the required tests of color, pH, setting time, consistency, compressive strength, film thickness, microlekage, and antibacterial. The complex [ calcium-guaiacolate] show superiority in this respect and it is hoped that this complex (as dental filling) establish a chemical binding with the calcium of the tooth.