Testing of Dental materials Flashcards
compression strength in test
shear forces along the cone-shaped area at each end
tensile forces central portion of the mass
compression forces on the ends
permanent bending
used to measure the number of bends the specimen will withstand and to compare different composition and dimensions as well as its treatment in fabrication.
eg. orthodontic wires and removable denture clasps
Diametral tensile strength test
test for tensile strength that is only used for materials that exhibit predominantly elastic deformation and little or no plastic deformation.
basically not for brittle materials
shear strength
the max stress that a material can withstand before failure in a shear mode load
eg. a metal bracket used for braces
fatigue strength
the stress level at which a material fails under repeated loading
fatigue strength testing
subjecting a specimen to alternating stress applications below its yield strength until fracture occurs.
stress may be: tensile, compressive, shear, bending, and torsion
what fractographic analysis
the study of fracture surfaces of materials.
helps to define the cause of failures and aid in the structural design, as well as to improve existing materials
what is tear strength
the measure of resistance of a material to tearing forces
what is hardness
the resistance of a material to suffer indentation, scratching, or bending
how is hardness tested?
applying a standardized force or weight to an indenter
Brinell Hardness test
using a spherical indenter to penetrate the material.
after hitting the material the diameter is measured of the dent.
Knoop Hardness test
a material is indented with a diamond shape and then the height and length of the indentation is measured
Vickers Hardness test
measure of the surface area of the pyramid indentation on the material
The resistant to wear of the composite resins to abrasion depends on what?
the nature of the filler particles(glass or quartz) and on silanation of the filler
How many more times is enamel resistant to abrasion than dentin?
5 to 20
cementum is the least resistant to abrasion
After how long can prophylaxis fluoride be removed?
30 seconds
how much enamel can be removed due to abrasion
0.6 to 4 micrometers
what is working time
time after which the material cannot be manipulated without creating distortion in the final product
final setting time?
the time at which a material can be withdrawn without distortion or tearing.
eg. alginate
initial setting time
the time at which a certain arbitrary stage of firmness is reached in the setting process
Dynamic mechanical analysis
allows us to predict the strength and structure of the tested materials and applicability in the clinical setting
what is rheology
the study of deformation and flow of materials
What does the differential scanning calorimetry tool do?
determines temperature transitions in materials
eg. glass transition temperature and melting temperature
Spectrometric technique
Fourier-transformed infrared (FTIR) spectroscopy is used for molecular characterization and for following chemical reactions
Pycnometry
a technique used to determine material density
Bond strength test methods
macroshear
typical dentin bond strength values are 10-50 MPa. Cohesive and mixed failure 55% of specimens
Bond strength test methods
macrotensile
typical bond strength values are 10 MPa. Cohesive and mixed failure 35% of specimens
Bond strength test methods
Microtensile
typical bond strength values are 30-50 MPa. Cohesive and mixed failure less than 20% of specimens
Bond strength test methods
Microshear
typical bond strength values are 20 MPa. Cohesive and mixed failure 50% of specimens
Polymerization Stress Test
was developed to evaluate the stresses developed at the bonded interface due to resin composite polymerization while bonded to cavity walls.
What are the two committees that have to pass a product?
American National Standards Institute (ANSI)
American Association Standards Committee of Dental Products
Then approval is reviewed by the Council of scientific affairs of the ADA
What is the program for international specifications?
FDI World Dental Federation and the International Organization for Standardization (ISO)
