Biomaterials, restorative materials, and tissue engineering are fundamental to the dental hygiene process of care and are used in a variety of dental hygiene roles and practices. This chapter reviews the general considerations of specific biomaterials as well as preventive and restorative materials, including applications, terminology, and classifications for each; the structures of materials in terms of the starting components, reactions involved in their use, and manipulation procedures; and the properties of materials, including physical, chemical, mechanical, and biologic characteristics.
Direct applications of these materials include dental amalgams; dental composites; pit-and-fissure sealants; infiltrants for lesions; bonding agents; cement liners, cement bases, and other cements; fluoride-releasing restorative materials, topical fluorides, and fluoride varnishes; dentifrices and prophylactic pastes; and bleaching agents. Indirect applications include impression materials, provisional materials, models, casts, dies, waxes, investment materials, casting alloys, dental solders, chromium alloys for partial dentures, porcelain-fused-to-metal (PFM) alloys, dental ceramics, crown-and-bridge cements, acrylic appliances, acrylic denture bases, denture teeth, denture liners, denture cleansers, mouth protectors, veneers, computer-assisted design and computer-assisted machining (CAD/CAM) and copy-milled restorations, and dental implants.
FIGURE 13-1 Linear coefficient of thermal expansion.
b. Electrochemical corrosion—chemical reaction that requires an anode (e.g., dental amalgam), a cathode (e.g., gold crown), an electrolyte (e.g., saliva), and an electrical circuit (e.g., contact) for electron flow (Figure 13-2)
FIGURE 13-2 Electrochemical corrosion.
(3) Crevice corrosion—corrosion in the crack under plaque, between a restoration and the tooth structure, or in the scratch on the surface of a restoration, where the metals may be the same but the electrolytes are different locally
FIGURE 13-3 Resolution of forces.
FIGURE 13-4 Stress–strain curve.
(e) Hardness—value on a relative scale that estimates the elastic limit in terms of a material’s resistance to indentation, for example, Knoop hardness scale, Diamond pyramid hardness scale, Brinnell hardness scale, Rockwell hardness scale, Barcol scale, Shore A hardness scale, and Mohs’ hardness scale (Table 13-1); hardness values are used to determine the ability of abrasives to alter the substrates they contact
|Hard gold alloys||3–4|
(2) Instruments may transfer debris onto the cut surface from their own surfaces during cutting, polishing, or cleaning operations (this has important implications in cleaning dental implant surfaces)