Dental materials properties and management powers and wataha Flashcards
Diabetis and perio
Increases the risk of periodontal disease
flourosis
high levels of fluoride consumed from drinking water during tooth formation & calcification causing stain
Two basic kinds of restorations
- Intracoronal prepared cavity in the tooth structure internal components
- Extracoronal structure of the tooth on the outside (crown) often indirect fabrication but can be direct as well.
edentulism
All teeth missing
Some missing would be partial edentulism
Dental Bridge
- Also called fixed partial denture
replaces missing teeth, has retainer at each end. Retainers are supported by teeth called abutments. Replacement teeth called pontics
Maryland bridge
replaces anterior or posterior tooth and is cemented directly to the adjacent or abutting teeth, also called resin bonded negating the need to place crown on the abutment teeth
considerations for removable partial dentures
- Adequate root structure of remaining teeth
- Health
- Age of patient
- Periodontal health
- Ability to care for product and clean well
Caries is caused by:
- food debris.
- materia alba.
- bacterial plaque. Correct
- salivary glycoproteins.
- acidic foodstuff.
- See questions on evolve elsiever
Dimensional change of a material
The percentage of shrinkage or expansion of a material in dentistry related to heating and cooling or thermal dimensional change
Linear thermal coefficient of expansion of a material
a measure of how much it expands per unit length if heated 1 C degree higher
What are the best materials by the coefficient of linear expansion for dental restoritives
- Gold
- Ceramic
Amalgam and composites 3-5 times that of teeth
percolation
repeated expansion and contraction of teeth and restoration at different rates and the oral fluid entering the space and being forced out by this contraction and expansion.
Dental amalgam and percolation
decreases over time thought to be from corrosion at the margin of the restoration
Percolation and composites
Gets worse as the bond is broken down over time.
Thermal conductivity and dental restoratives
high thermal conductivity values = good conductors of cold
Thermal conductors
good conductors metals and alloys
Poor ceramics and composites
Cavity liners and bases such as glass ionomers are used to combat thermal sensitivity why?
Thin dentin in deep cavity preps the bases gives extra space until secondary or tertiary dentin is formed protecting from thermal insults
Galvanism or corrosion of dental materials
Two dissimilar metals in the mouth. Oral fluids provide ions and the diffence in the electrode potential of the metals can produce an electric potential that the patient can feel. Generally to opposing teeth or a spoon on a crown or restoration.
Gold to aluminum
Tarnish
sruface reactions of metals in the mouth from components in saliva and foods
Corrosion
is the dissolution of metals in the mouth and pits and rougness. seen in gold crowns contaminated with iron fragments
Solubility and sorption
- the solubility of material in the mouth and how their sorption of oral fluids is an important consideration because they will be exposed to plaque (that give off various acids and organic materials)
- Reported 2 ways in weight percentage of soluble or sorbed material in the solid
and the weight of the solution on the surface of the material.
absorption and adsorption
Absorption= uptake of liquid by the bulk material
Adsorption is the concentration of liquid molecules on the surface of the solid material
Wettability
is a measure of the affinity of a liquid for solid as indicated by spreading of a drop
shape of a drop of liquid when determining wettability
- Low contact angle Hydrophillic no beading of the drops
2. High contact angle of the drop Hydrophobic the liquid beads up
Patients with dentures apply what percent of normal force
19%
Stress
is the force per unit area
usually a ratio
so smaller area higher force = higher stress
Usually reported as MPa
Strain
is the change in length per unit length of a material produced by stress
Forces acting on teeth can be seen as
- Compressive
- Tensile,
- shear
- Twisting movement
- bending moment
Strain
is the change in length per unit length of a material produced by stress
Elastic modulus
= to the ratio of the stress to the strain in the linear or elastic protion of the stress-strain curve.
Or it is the stiffness of a material
- Yield strength
2. proportional limit
- amount of force needed to cause permanent deformation
2. End point of the straight line portion of SS curve
Ultimate strength
The stress point at which fracture occurs
If this happens with tensile then tensile strength, compression strength, and shear strength
Elongation and compression
amount of deformation a material can withstand before rupture
- Percent of elongation when under tensile stress
- report as a percent of compression when under compressive stress
Percents of elongation are important properties in that they are measurements of
Ductility and malleability
Ductile alloys
high elongation percent allows significant deformation before fracture
Brittle materials
low elongation percentage so minimal deformation before fracture