The most of dental materials used in pedodontics and orthodontics are suspected as nonbiocompatible. In this article, analyses in biocompatibility of the materials, designs of biocompatible materials and the biocompatibility of the dental materials used in pedodontics and orthodontics will be discussed according to the recent literature. Although, the adverse effects in the living organisms of some solutions and filling material used in pediatric dentistry for the prophylactic, conservative and corrective purposes were shown in vitro, in fact their clinical incidence is very rare to prove their being. On the other hand, the allergic reactions caused by acrylic and metallic components of removable and fixed orthodontic appliances are rarely but certainly observed in clinical practice. The fact that the medical dentists and the dental production companies are becoming conscious increasingly and the continuing scientific and technological reseacrhes will decrease the probability of the complications made by dental materials and will challenge a better clinical practice.