Final Study Guide Flashcards
What is sclerotic dentin?
Primary dentin that has changed
What happens when sclerotic dentin is placed?
Peritubular dentin widens, fills with calcified material
What is reparative dentin formed by?
Secondary odontoblasts at the end of the tubules at surface of pulp
What is reparative dentin formed in response to?
Moderate irritant, trauma, chronic irritation
What does reparative dentin provide protection to?
Underlying pulp by decreasing dentin permeability
Describe this diagram
What is a line angle?
Junction of 2 walls
What is an internal line angle?
Apex points away from observer
What is an external line angle?
Apex points toward observer
What is a point angle?
Junction of 3 walls
What is resistance?
Resistance to fracture (withstand occlusal forces)
How can you ensure you get ample resistance?
Conservative extension
Preserce cusps and marginal ridges
Internal/external line angles need to be beveled
Flat floors to precent restoration movements
What does a bevel reduce?
Stress
What should you do if the margin exceeds 2/3 distance of central groove?
Cap weak cusps
What should you do if margin ends 1/2 distance of central groove and cusp tip?
Consider capping cusps
What is retention?
Retains restoration during function
What can you do to ensure retention?
Convergence
Parallelism
Taller walls
Dovetail
What does a dovetail prevent?
Tipping and proximal displacement
Class I
Occlusal surface of posterior teeth
May include lingual/buccal grooves and pits
Class II
Proximal surfaces of premolars and molars
Class III
Proximal surfaces of incisors and canines that DO NOT involved the incisal edge
Class IV
Class III but with an added incisal edge
Class V
Gingival ⅓ of smooth surfaces
Buccal, lingual
Class VI
Incisal edge or cusp
Where are retention grooves placed in the box?
- just inside DEJ, entirely in dentin (do NOT go into gingival flor)
- at buccal/lingual axial line angle
Where are retention grooves placed in a class V?
- occlusal retention groove@ occlusal - axial line angle and gingival retention groove
- always in dentin just inside DEJ
Where do walls converge and diverge?
What is convergence for?
retention (isthmus/box walls)
What is divergence for?
Preserve the marginal ridge and ensure no undermined enamel
What is coppers role in amalgam?
Strength
What is the copper contents of conventional amalgam?
Low copper
What are qualities of high copper amalgam?
Superior to conventional
We use this
What does high copper amalgam eliminate? what does it add?
Gamma 2 phase = stronger restoration
Adds copper-tin phase
What does premature contact do to area?
Decreases area
What does premature contact do for occlusal force and stress?
Occlusal force stays the same but occlusal stress is increased
What is a result of premature contact?
Restoration failure
Pain/discomfort when biting
What is stress?
When load (force) is applied to material, stress is response
What are examples of stress?
- Protrusive movement
Anterior teeth
Flexure load on incisors - Posterior occlusion
Chewing = compressive load
At marginal ridge contact areas
At fossa areas - Occlusal stress = occlusal load (force) / occlusal contact area
- Tripodized occlusal contacts allows distribution of occlusal load across maximum area = minimal stress
What is compression?
Push
Stress necessary to fracture material by 2 forces OPPOSING eachother
What kind of load does compression require to cause failure?
Higher loads
What is the highest strength force?
Compression
What is the lowest type of force?
Tensile
What is tensile force?
Pull
Stress necessary to fracture a material by 2 opposing forces AWAY from eachother
When does tensile failure occur?
At lower loads
ex: laffy taffy
What is shear force?
Sliding
Stress that ruptures material of 2 opposing forces in different planes
What is intermediate between compressive and tensile force?
Shear
What is an example of shear force?
Implant-bone interface
What is torsion?
Twist
What is torsion used for?
To place implants (torque)
- torsion test on dental implants
- torsion fatigue on endo rotary files
What is flexural force?
Bending force
Stress to cause failure in bending
What is the test for flexure forces?
3 point bend test
- compressive load
- combo of compressive and tensile
What is flexural force vital due to?
Occlusal load
- on direct restrations (amalgam/composite)
- indirect/removable (everything that gets chewed on)
Describe biological properties
Biologic response when contact with human body
ex: gingivitis from plague
Describe surface properties
Material associated with surface
ex: denture retention, adhesive bonding
Describe physical properties
- type of atoms and bonding present in material
- size or shape have no effect
- structure insensitive
ex: optic (color, glass)
Thermal (conductive)
Describe mechanical properties
- reaction of a material to the application of an external force, size and shape affects properties
- structure sensitive
- applied force referred to as load
What bonds does amalgam have?
Metallic bonds
- cluster of positive metal ion surrounded by gas of electrons
- non directional bonds
- high electrical and thermal conductivity