Properties of Dental Materials DA 122 Dental Materials

Council on Dental Materials, Instruments, and Equipment  Subgroup of the American Dental Association  Sets standards and specifications that all dental materials must meet

Acidity  1. affect oral tissues: Changing acidity levels determines use of products in oral cavity  2. acidity of materials may cause irritation to gingival tissue or damage to pulp  Ex. Mountain Dew!!

Adhesion  Chemical or physical force or attraction that holds unlike substances together

Biting Forces  Stress  Strain  Tensile  Ductility  Compressive  Malleability  Shearing  Bruxism

Stress and Strain  Stress: reaction of an object to resist external force  Strain: Enough stress placed on an object to cause change or deformation

Tensile  Pulls and stretches a material  Tensile stress and strain causes structure to be elongated  Ex. Tug-of-war

Tensile Strength  Resistance to a pulling force  Important quality of dental materials

Ductility  Ability of material to withstand forces of tensile stress without failing

Malleability  Ability of a material to withstand compressive stresses without fracturing  Capable of being reshaped or flattened

Shearing  Slides one part of material parallel to another, in back and forth motion  Ex. Cutting with scissors

Biting Forces

Bruxism  Grinding of teeth  Example of shearing

Corrosion  Tarnish: reactions of saliva and metal to cause dullness and discoloration

Dimensional Change  Shrinkage or expansion of dental material or other substance  Distortion  Disfigurement  Deformation (remember the 3 D’s!)

Distortion  Mis-shaped, twisted out of proper or normal shape

Deformation  Distortion or disfigurement

Prevention of dimensional changes  Distortion, disfigurement and deformation are all undesirable changes  Occur when dental materials are mishandled

Elasticity  Capable of maintaining or returning to normal size and shape after having been stretched  EX. Rubber bands

Flow  To move in a manner similar to a liquid stream  To creep or slump  Ex. Compare water and honey

Galvanism  Electrical shock resulting when two dissimilar metals contact one another in the mouth  Oral fluids act as a carrier between the two metals  Ex. Biting on a piece of tin foil with an amalgam restored tooth

Hardness  Resistance of material to scratch or indent  “hard as a rock”

Microleakage

Retention  Means by which materials and surfaces are held in place 1.mechanical retention 2.chemical retention

Mechanical Retention surfaces are prepared to hold materials in place

Chemical Retention  Chemical reaction between tooth surface and material

Bonding Process  Process by which materials adhere firmly or hold together  Dentistry uses bonding agents to bond dentin and enamel with restorative materials

Solubility   Ability/rate of material to dissolve in fluid  Important if material is going to be exposed to the saliva and might dissolve and expose tooth structure

Thermal Properties  Relate to temperature (i.e. heat)  1. thermal conductivity/sensitivity  2. thermal expansion

Thermal Conductivity  Ability of a material to feel, transmit, or react to heat

Thermal Expansion  Reaction of material with heat to cause expanding or contracting

Exothermic Properties  When a dental material releases heat when it sets Example: pour dental models in gypsum- heats as it sets

Viscosity  Ability of a liquid to flow  Thicker material: Less flow More viscous  Olive oil  Thinner material: More flow Less viscous  Vinegar

Wettability

Key Terms Activity Using index cards make key terms for the properties of dental materials Copyright 2012 Porter and Chester Institute, Inc. All rights reserved