Many chemical constituents. Often based on SiO2
traditionally have glass and more ordered elements.
Use of ceramics
Denture teeth, Crowns, PFM, inlays, onlays, laminates
Structure of soda glass
Na2O-SiO2. Sodium disrupts the silica crystal. Metal oxides lower melting range and decrease viscosity. Make it glossy
Properties of ceramic material
high compressive strength but low tensile strength
Strengthening Brittle materials
Interrupt crack propagation. Introduce residual stress on surface. Add high-fusion tough particles. Expansion of mismatch of layers. Resin-bonded cementation
Transmission of stress through ceramic
Smoother surface gives increased strength because stresses don't concentrate. Glazes and polishes
Contraindicated in ceramics because of low pH. acidulated phosphate fluoride.
Turning porcelain opaque after multiple firings. Vitreous (amorphous) portions crystallize
Design considerations for ceramics
Minimize tensile stress (contraindicated on posterior teeth without metal) and stress concentrations (thick enough and rounded).
Advantages and disadvantages
Advantages: Esthetics, high compressive strength, chemical durability, biocompatible, stain resistant. Disadvantages: Brittle, low tensile strength, high hardness.
Thin veneers that are bonded to acid etched enamel with resin cement. Fragile until bonded, expensive, may abrade opposing teeth.