Intro to Biomaterials-Amalgam & Class I and Class V Restorations Flashcards
What are the four major classes of dental materials?
- Metals and Alloys
- Porcelains and Ceramics
- Polymers
- Composites
Who regulates dental materials?
American Dental Association
Food and Drug Administration
How does the atomic structure affect the dental materials?
Atomic structure determines mechanical and physical properties of materials
What are the types of interatomic bonds?
Primary
- Ionic, covalent, metallic
Secondary
- H bonds, Van der Waals forces
What is an ionic bond?
Electrostatic attraction of positive and negative charges
- involves electron transfer between ions
What are the properties of an ionic bond?
- non-directional, strong bond
- no free electrons
- good thermal and electrical insulator
What are some examples of dental materials that use ionic bonds?
ceramics
gypsum
What is a covalent bond?
2 atoms share an electron
What are the properties of a covalent bond?
- directional bond
- low electrical and thermal conductivity
- water insoluable
What are some examples of covalent dental materials?
polymers
composite
What is a metallic bond?
Cluster of positive metal ions surrounded by a gas of electrons
What are the properties of a metallic bond?
- non-directional bonds
- high electrical and thermal conductivity
What are some examples of metallic dental materials?
amalgam and gold alloys
What are the four classifications of material properties?
biological
surface
physical
mechanical
What is the biological classification of material properties?
The biological response to a material when in contact with the human body (ex: gingivitis from plaque)
What is the surface classification of material properties?
The unique properties of a material associated with its surface (ex: denture retention, adhesive bonding)
What is the physical classification of material properties?
Depend on the type of atoms and the bonding present in material; size or shape have NO AFFECT (ex: optic and thermal)
What is the mechanical classification of material properties?
Reaction of a material to the application of an external force, size and shape of specimen AFFECT properties
What is fracture strength?
how much stress a material can withstand before it breaks
What type of stress is compressive?
pushing
- Measure of the stress necessary to fracture a material by 2 opposing forces directed toward each other
What type of stress is tensile?
pulling
- Measure of the stress necessary to fracture a material by 2 opposing forces directed away from each other
What type of stress is shear?
sliding
- Stress necessary to rupture a material by 2 opposing parallel forces directed toward each other but not in the same plane
What type of stress is torsion?
twisting
What type of stress is flexure?
bending
- Measure of stress to cause failure in bending
What is the highest strength measure for most materials?
compressive strength
What force pushes atoms and structures closer together?
compressive
What is the lowest strength for most materials?
tensile
Where does protrusive movement place stress?
anterior teeth (incisors)
Where does posterior occlusion put stress?
- marginal ridge contact areas
- fossa areas
What does premature contact cause?
- decreased area
- occlusal force is the same
- occlusal stress is increased
- possible restoration failure
- possible pain/discomfort
What is strain?
The DEFORMATION that occurs in a material when force is applied to the material
What is elastic strain?
temporary distortion of material by applied force
* Strain is BELOW THE ELASTIC LIMIT
* When force is removed, materials reverts to original form
What is plastic strain?
PERMANENT distortion of a material
* Strain is BEYOND the elastic limit
Elastic portion of strain recovered Plastic portion of strain NOT recovered
* When force is removed, shape
remains changed
What are the benefits of amalgam?
- easy to manipulate
- place in its plastic state and carved before it hardens
- excellent physical properties (strong, self-sealing)
- cost effective
What is the composition of amalgam?
Silver - 70%
Tin - 16%
Copper - 13%
Zinc - 1%
What are the metals of amalgam mixed with to form an alloy that can be packed into a dental prep?
mercury
What phase does high copper amalgam eliminate to result in a stronger restoration?
eliminates gamma-2 phase
What phase of amalgam setting is the weakest and most susceptible to corrosion?
Gamma-2
What phase of amalgam setting is the most strong and corrosion resistant?
Gamma
What are the different shapes of particles depending on the type of amalgam?
- lathe
- admixed
- spherical
What amalgam shape of particle is the most commonly used type?
admixed
What are the characteristics of admixed amalgam?
- lathe mixed with small spheres
- more condensation force required
- most commonly used
- low early strength (1 hr)
- Kerr Contour and Ivoclar Valiant
What is the most critical variable in amalgam manipulation?
condensation
- undercondensation is the most common error made by dentists
What are the different variables for amalgam manipulation?
- mercury to alloy ratio
- trituration
- condensation
- carving and finishing
Amalgam has or has not been found to play a role in neurodegenerative diseases?
has NOT
What are the properties of amalgam?
- high compressive strength and low tensile strength
- sensative to moisture contamination
- can corrode
- creates and regenerates a seal between itself and the tooth
What are the disadvantages of amalgam?
- poor esthetics
- need good mercury hygiene
- remove more tooth structure
- doesn’t bond to tooth structure
- thermal conductor
- may “ditch” at the margins
What are the advantages of amalgam?
- More forgiving in areas where moisture is hard to control.
- High wear resistance and compressive strength.
- Can be placed in less time than other options (lower cost.)
- Relatively long-lasting.
- Regenerates its seal.
- Is less prone to recurrent decay than bonded composite resin restorations.
When can you use amalgam?
- Moderate to large Class I and Class II restorations.
- Heavy occlusal wear.
- High caries rate.
- Difficult isolation.
- Gingival margins on root.
- Class V restorations in non-esthetic zones.
- Temporary restorations on teeth with questionable prognosis.
- Buildups under crowns for extensively damaged teeth
What are the steps for placing an amalgam occlusal restoration in the clinic?
- Place liner and/or base if needed
- Seal dentinal tubules (if needed)
- Mix Amalgam
- Dispense into amalgam well and pick up with carrier
- Place amalgam
- Condense Amalgam
- Overfill the Prep
- Pre-carve burnish
- Carve anatomy
- Refine Restoration
- Smoothign the surface
What are the different types of liners/bases?
- Calcium hydroxide (dycal)
- Glass Ionomer (vitrebond)
How do you place the liner/base?
place in deeper areas only with a dycal instrument, keeping away from the margins
When do you use liner verses base?
- liner is a thin layer over dentin
- base is a thick layer on the floor of prepared cavity
When would you need to seal dentinal tubules?
when teeth may be especially prone to sensitivity
What are the different types of desensitizers?
- copal resin
- bonding agents
- gluteraldehyde (Gluma)
What are the advantages and disadvantages of Gluma?
advantages - no film thickness, one step application
disadvantages = expensive, somewhat caustic to soft tissues and pulp
How do you apply Gluma?
-apply to walls for 30 seconds , dry, rinse, dry again.
-material is caustic; minimize contact with gingivae and protect pulp with liner/base in deep preparations prior to applying.
How should you condense amalgam?
a. Tamp into the preparation to fix the amalgam in place
b. Use the small condenser nib to pack the material FIRMLY into all line angles at a 45 degree angle, using a pressing, wiggling motion
How much should you overfill the amalgam preparation?
1.0 mm
How long do you need to wait after placement to finish and polish amalgam?
24 hours after placement
What are the different types of finishing burs?
*Green stone (coarse)
*White stone (medium)
*12 bladed polishing bur
(medium-fine)
What are the different types of polishing burs?
- Brown (pre-polish)
- Green (polish)
- Green with yellow collar
(superpolish)
What is the basic procedure for amalgam restoration?
- Triturate amalgam
- Place amalgam
- Condense amalgam
- Pre-carve burnish
- Carve anatomy
- Assess occlusion, refine restoration
What is the basic procedure for composite resin restoration?
- Etch 20 sec, rinse
- Place bond, gently air dry, light cure
- Place composite increment, condense, light cure, repeat until prep is filled
- Create anatomy, finish occlusal surface, light cure
- Assess occlusion, refine restoration
- Polish
What are the steps in the clinic for placing an occlusal restoration using composite resin?
- Acid etch prepared toot structure
- Place bond agent into enamel and dentin
- Insert composite resin via syringe
- create anatomy before light curing fingal increment
- Finish and Polish
What are the advantages of composite?
- preps are more forgiving
- esthetic
- operator control of set up time
- preserve tooth structure
What are the disadvantages of composite?
- restoration more technique sensitive
- additional steps
- may not last as long
- not as strong
- no moisture tolerance
