2Occlusal forces Average occlusal forces for fully dentate patients : 150 Newton in the anterior region to 500N in posterior regionMaximum occlusal forces: different reports in the literature up to 3500N.The occlusal forces for edentulous patients 15% of dentate patients.
4Stress Stress: Internal resistance to applied external force. Force per unit area; a force exerted on one bodythat presses on, pulls on, pushes against, or tends to invest,compress another body; the deformation caused in a body by such a force;an internal force that resists an externally applied load orforce. It is normally defined in terms of mechanical stress, whichis the force divided by the perpendicular cross sectional area overwhich the force is applied.GPT 2005, J Prosthetic DentistryStress: Internal resistance to applied external force.Stress= Force/Area
13B:Yield strength(YS)The stress at which a material exhibits a specified limiting deviation from proportionality of stress to strain* YS indicates a degree of permanent deformation (usually 0.2%)YS indicates a functional failure!!!
14Elastic modulusIs a measure of elasticity of the material: how stiff the material is in the elastic rangeElastic modulus= Stress/StrainThe slope of the curveABStress (Pa)StrainResilience
15Poisson’s ratioRatio of lateral to axial strain within the elastic range
16Ductility and malleability Ductility: The ability of a material to be plastically deformed.Malleability: The ability of a material to be hammered or rolled into thin sheets without fractureing.
18C: Ultimate strength Tensile or Compressive. The Ultimate strength: The maximum that a material can withstand before failure (tension or compressive).it does give an indication of the needed thickness (cross section) of the restorations before failure.
19D: fracture strengthThe stress at which the material fractures.
20Toughness The resistance of a material to fracture So what does yellow area under curve represent?
21Fracture toughnessThe amount of energy required for fracture.
22Bond strength:the bond strength between two dental materials.Either tensile or shearFatigue bond strength?
45MetamerismWhen two colour samples match when viewed under one light source but not another.Any significance in dentistry?
46FlouresenceThe emission of luminous energy by a material when a beam of light is shown on it.What impact does this have in anterior restorations.
47Thermal properties Heat of fusion: melting or freezing heat. Coefficient of thermal expansion: of paramount importance in clinical dentistry, why???Glass transition temperature??? For non metallic structures; glasses and polymers