2. The science of dental materials involves the study of the composition and properties of materials and the way in which they interact with the oral environment in which they are placed.

3. Dental materials may be classified: - impression materials, - wax, - metals, - polymers, - ceramics

32. Metals  Metals are used for making restorations of the lost tooth structure, prosthetic devices, orthodontic appliances, and many other applications where strength and elasticity are required.  A mixture of two or more metallic elements is called alloy (Gold alloy &Cobalt chromium alloy)

33. Metallic restoration

34. COBALT CHROMIUM ALLOYS Cobalt based alloys are used in one of three forms Cast; as prepared Wrought (fine structure with low carbon contents ; pure forms) Forged Cobalt based alloys are better than stainless steel devices because of low corrosion resistance

35. Wrought alloy: possess a uniform microstructure with fine grains. Wrought Co-Cr –Mo alloy can be further strengthened by cold work. Forged Alloy: produced from a hot forging process. Forging of Co-Cr –Mo alloy requires sophisticated press and complicated tooling. Factors make it more expensive to fabricate a device

36. TITANIUM BASED ALLOYS The advantage of using titanium based alloys as implant materials are low density good mechano-chemical properties The major disadvantages relatively high cost reactivity.

37. Polymers Polymers are synthetic resins. Types of dental polymers: Polymeric impression materials. Denture base materials. Tooth colored restorative materials.

39. The structures of polymers determine their utilization in various medical domains like in surgery, dermatology, ophthalmology, pharmacy,depending on chemical and physical properties. The stability and lifetime of polymers in long-term implantation depend not only on chemical structure of the material employed but also on the conditions under which they are utilized. Biomedical polymers can be classified into either elastomers or plastics.

41. Ceramics Ceramics include a wide variety of substances such as glass, cement, refractory (high temp), and many other materials.

42. Types of dental ceramics:  Dental porcelain.  Dental cements.  Gypsum products.  Casting investment

43. Ceramic restoration

44. Ceramo-metal system Bridge