Oral environment Flashcards
what causes the oral environment’s complexity
- amount of saliva and pH of saliva
- oral hygiene
- forces upon the area to be restored
selection of the most appropriate dental material depends upon
- extent of decay
- type of defect
- condition of oral cavity
- visibility of restoration
- cost
three limitations of the oral environment
- what can and cannot used safely
- type of tx, long-term clinical needs of the tx
- condition of the oral cavity (oral hygiene and health; loss of teeth; broken down teeth)
restorative
- to reconstruct tooth structure
therapeutic
- the ability to treat disease
aesthetic
- aestetically pleasing appearance
therapeutic agents
- generally used for short periods of time
restorative agents
- expected to remain in contact with tissues for indefinite periods of time
common dental restorative materials
- composite resins
- amalgam
- sealants and preventive resins and restorations
- glass ionomers
- temporary materials
- tooth whitening products
- gold alloys
- veneers
who makes sure standards are being followed for dental materials by manufacturing companies
- the committee on clinical and scientific affairs (a subcommittee of the canadian dental association)
criteria for all dental material
must not be:
- poisonous or harmful to the body
- harmful or irritating to the tissues of oral cavity (o.c)
must be:
- help protect the tooth and tissues
- resemble the natural dentition acap for aesthetics and function
- be easily formed and placed to restore natural contour
- conform and function despite limited access, wet conditions and poor visibility
- biocompatible
- durable
- non-reactive in acidic and alkaline conditions
- compatible with other materials
- aesthetically acceptable
biomechanics
- functions of material dependent on properties, and on what the material is expected to do
- withstand varying degrees of force or load caused by muscular actions of pushing and pulling during mastication and bruxism
what is a biting force
- a measure of the strength of the muscles of mastication during normal chewing
what is stress
- the internal force, which resists the applied force
what is strain
- distortion or deformation occurring when an object cannot resist a stress
what is a force
- any push or pull on matter
what are the 3 types of forces
- compressive: pushes the material together
- tensile: pulls and stretches the material (applied in opposite directions)
- shearing: breakdown of material as a result of something sliding over the 2 areas (in a twisting or rotating motion)
normal masticatory forces
- on occlusal surfaces: 90-200 lbs
- on a cusp tip can = 28,000 lbs/square inch
- decreased in incisor areas
- increased during bruxism
forces enamel can handle (in lbs/in2)
- compressive: 56,000 lbs/in2
- tensile: 1500 lbs/in2
forces dentin can handle (in lbs/in2)
- compressive: 43,000 lbs/in2
- tensile: 4500 lbs/in2
forces amalgam can handle (in lbs/in2)
- compressive: 45,000 - 64,000 lbs/in2
- tensile: 7000 - 9000 lbs/in2
forces porcelain can handle (in lbs/in2)
- compressive: 21,000 lbs/in2
- tensile: 5400 lbs/in2
forces composite resins can handle (in lbs/in2)
- compressive: 30,000 - 60,000 lbs/in2
- tensile: 6000 - 9000 lbs/in2
forces acrylic can handle (in lbs/in2)
- compressive: 11,000 lbs/in2
- tensile: 8000 lbs/in2
what is fatigue failure
- repeated stresses, produce microscopic flaws that grow and over time result in fractures
what is flexural stress
- bending stress, a combination of tension (tensile) and compression
pH of oral cavity depends on:
- foods
- beverages
- medications
- the amount of biofilm (acid-producing bacteria) present
the breakdown of most restorative materials is directly related to:
- acid
- moisture
- stress
what is solubility
- susceptibility to being dissolved
what is water sorption
- the ability to absorb moisture
what is corrosion
- breakdown of metal from chemicals or an electrochemical reaction between metals due to moisture and acid in the oral cavity
what is tarnish
- discolouration caused by oxidation on the surface of a metal
what is galvanism
- an electric current transmitted between to dissimilar metals
what is galvanic shock
- when the electric current caused by galvanism results in stimulation to the pulp
what is dimensional change
- all forms of matter will expand when heated and contract when cooled
what happens when there is excessive expansion (heat)
- leads to fracture of cusps
what happens when there is excessive contraction (cold)
- leads to microleakage
what is percolation
- movement of fluid between the restoration and the tooth
- as a result of different expansion and contraction rates of tooth and restoration with temperature changes from the ingestion of hot and cold fluids and foods
what happens when there is percolation
- allows bacteria and oral fluids to accumulate at the margin of a restoration which can lead to
- recurrent caries
- staining
- pulpal irritation
what is thermal conductivity
- the rate at which heat flows through a material
what are insulators
- matter that prevents the passage of electricity, heat, or sound through an object
what is retention
- the ability of a material to maintain its position without displacement under stress
what is mechanical retention
- when material is locked into place through the use of undercuts or other projections
what is chemical retention
- when a reaction takes place between two materials to form a bond
what is bonding
- the ability to hold two components together
what is the acid etch technique
- creates microscopic pores in enamel and dentin
- a fluid bonding material then flows into these pores to form a mechanical lock into the tooth structure
- restorative materials are then placed that adhere chemically to the bonding material
what is microleakage
- the seepage of harmful materials
- responsible for:
- recurrent caries
- marginal staining
- postoperative sensitivity
aesthetics-wise, there are 3 components of colour in dentistry:
- hue: the dominant colour of the wavelength
- chroma: the intensity or strength of the colour
- value: describes how light or dark the colour
light considerations (4):
- transparent: is when light passes directly through an object
- opaque: when light is completely absorbed by the object
- reflect: when light is thrown back off the object
- translucent: when diffuse light is let through an object
how can we identify restorative materials
- appearance
- location of margins
- tactile sensitivity
- radiographs
what tools can we use to identify restorative materials
- adequate illumination
- air
- sharp explorer
- magnification
materials must be:
- biocompatible
- exhibit long-term clinical durability
- be aesthetically acceptable
