Dental Materials - Complete denture acrylics Flashcards
Define denture base
Part of the denture which rests on oral mucosa and teeth are attached
What properties should denture bases have (3)
Retentive, stable, supportive
5 functions of denture bases
Aesthetic Support and retain artificial teeth Support lips and cheek Stimulate underlying tissues Eliminate undesirable food
Requirements of ideal denture base material (8)
Natural appearance Easy processing Easy to clean Easy to repair Inexpensive and long shelf life Biocompatible Resistant to bacterial contamination Radio-opaque Heat transfer Adequate mechanical properties (strength, stiffness, hardness, toughness)
Why should denture bases material be radio-opqaue?
Can be seen on X-ray if swallowed
What is the most common material used as a denture base?
Acrylic denture base - PMMA
Composition of PMMA
Powder and liquid
Powder = polymer
Liquid = monomer
4 stages of polymerisation
Activation
Initiation
Propagation
Termination
Denture processing problems
Porosity
Strains
List 3 types of porosity
Polymerisation shrinkage = contraction porosity
Volatilisation of monomer = gaseous porosity
Granular porosity
Cause and manifestation of contraction porosity
Insufficient material or pressure
Porosity throughout denture
Cause and manifestation of gaseous porosity
Vaporization of monomer during processing
Porosity in localised area (thicker parts)
Cause and manifestation of granular porosity
Incorrect polymer:monomer ratio
Porosity appears in thin sections - white frosty appearance)
What types of processing strains can occur?
Warpage, crazing, distortion
What problems can occur when a patient cleans the acrylic denutre?
Brush and paste = scratching and abrasion - (hardness of material)
Soaking = oxygenating cleanser and water temperature