Intro to DMS Flashcards
Behaviour of dental materials effects the selection of material. What considerations do you need to make?
- Is the material adequate and the best type?
What should be on a product to ensure that it is safe?
- A CE mark
- However, it is not a guarantee that the material is the best available
What are 5 examples of restorative materials?
- Amalgam
- Composites
- Glass ionomer cements
- Compomers
- Porcelain
What are 4 examples of impression materials?
- Impression compound
- Impression paste
- Hydrocolloids
= Alginate
- Elastomers
= Polysulphides
= Polyethers
= Silicones
What are 5 examples of metals/alloys that are used in dentistry ?
- Amalgam
- Cobalt chromium
- Titanium
- Gold
- Stainless steel
What does Porcelain look like?
- Tooth like in appearance
What material is used for a negative replica of the dentition?
- Impression materials
What material is used to make a positive replica of the dentition?
- Gypsum
What can stainless steal be used for in dentistry?(2 points)
- A denture base
- An orthodontic appliance
What can cobalt chromium be used for in dentistry?
- Partial denture
What is the relevance of studying DMS?
- Will use many different materials with a range of characteristics and modes of use
- Must use materials appropriately
- Must be independent
- Need to be able to communicate with other dental professionals
- Provides framework for understand=nding materials
- Be able to address health and safety issues of materials - allergic components
- Manage patient expectations (aesthetics, longevity of restoration)
What are the different properties of a material that we need to know about? (3 points)
- Mechanical
- Chemical
- Physical
What could a force applied to a material cause it to do? (3 points)
- Stretch/compress (depends on how the force is applied)
- Deform (temporary or permanent)
- Fracture (failure)
What is compressive strength?
The maximum compressive stress that under gradually applied load is given solid material will sustain without fracture
What is tensile strength?
- The greatest longitudinal stress a substance can bear without tearing apart
What is shear force?
- Unaligned forces pushing one part of a body in one direction, and another part of the body in the opposite direction
What is stress?
- Force applied divided by the area of the object
What is strain?
- The change in length with respect to the original length
- Stress is proportional to strain
What is stress proportional to?
- Strain
What is the Young’s modulus equal to?
- Stress/strain
- It i the gradient or slope of the linear bit of a stress/strain graph
What is opposite of hard?
- Soft
What is the opposite of strong?
- Weak
What is the opposite of ductile?
- Brittle
What behaviour would you ideally expect from a dental material?
- Ideally it would have similar properties to enamel and dentine
What force is applied to upper teeth when biting?
- Compressive force
What is the typical biting force?
500 - 700N
50-70kg
What force is applied to teeth when grinding/chewing?
- Shear force - frictional force experienced
- Tooth slides along the surface of the other
What has a greater fracture stress: enamel or dentine?
- Enamel
What is more rigid: enamel or dentine?
- Enamel
What does the choice of material influence in relation to the cavity?
- The cavity design
What is the opposite of rigid?
- Flexible
What type of cavity design would yo make for an amalgam filling?
- Undercut
What type of cavity design would you make for a composite resin?
- Minimal
What type of retention is used for amalgam fillings?
- Mechanical
What type of retention is used for composite resin fillings?
- Adhesive
What is meant by fracture?
Large force causing catastrophic destruction of material’s structure
What is meant by hardness?
- Ability of surface to resist indentation
What is meant by abrasion?
- Material surface removal due to grinding
What is meant by abrasion resistance?
- The ability to withstand surface layers being removed, so compromising surface integrity
What is fatigue?
- Repetitive ‘small’ stresses over time causes material fracture
What is creep?
- Gradual dimensional change due to repetitive small forces
What does deformation mean?
- An applied force may cause a permanent change in the dimensions (but not fracture it)
What does de-bond mean?
- Applied forces sufficient to break material-tooth bond
What does impact mean?
- Large, sudden force causing fracture
What is hardness about?
- The surface, it is not about the strength
- If material is hard then indentation will be relatively small
- If material is soft then much deeper notch will be created
What is fatigue?
- Repeated stressors over a period of time can lead to the material cracking - not one single large stress
- Most failures are not due to the application of a single load
- When repeated loads are applied, small flaws (cracks) in a material grow (propagate), allowing fracture when only a relatively small force is applied
What is creep?
- Repetitive forces causing dimesional change
What is elastic limit and permanent deformation?
- If you apply a certain level of stress, material will stretch
- Eventually will reach the elastic limit - if you apply a stress larger than the material can cope with, if you release the stress the material will not return to its original length (ends up slightly longer) so ends up permanently deformed
What are 3 things you need to consider about chemical properties?
- Setting mechanism
- Setting time
- Corrosive potential
What are 5 things you need to consider about physical properties?
- Viscosity
- Thermal conductivity
- Thermal expansion
- Density
- Radiodensity
