Lec 10 - Class 2 Flashcards
class 2 challenge of achieving tight contacts solution
prewedge wooden or ring
class 2 challenge of achieving ideal proximal wall contours solution
using sectional matrices
class 2 challenge of achieving intimate gingival marginal seal
good wedging, use of flowable liners
when there are only interproximal caries in a class 2 we use this prep
class 2 slot
this type of class 2 is used when mesial and distal interproximals are carious as well as occlusal
MOD
modern composite systems are formulated with variations from the blank molecule for the last 50 years
bisGMA
when resin is exposed to light, there is a blank of the molecules
reorganizations
volumetric contraction (gelation, hardening, polymerization) of modern composite
2.6-7.1%
viscous plastic phase and material is able to flow
pre gel
viscous, flow cannot keep up with contraction phase
gel point
phase that is rigid elastic when contraction is obstructed stress occurs
post gel phase
this happens during post gel phase if bond strength is lower than stress
gap formation
this happens during post gel phase if bond strength is higher than the stress
deformation
invisible contraction leads to blank
stress
stress is usually this much
4-7 MPa
problems of contraction in posterior teeth include blank of the resin at the margins, formation of blank forces at the margins, blank in the enamel, and blank of the cusps
separation, tension, fractures, deformation
each resin needs a minimum amount of blank to obtain clinically acceptable results
energy
energy is measured in blank
joules
optimal energy to polymerize a resin
16 joules (40 seconds with curing light)
joules formula
watts x time
if you double the watts cant you just cut the time polymerizing time in half?
no because it takes time for energy to be absorbed
there are blank and blank polymerizing resins
fast, slow
blank is formed when the resin cannot adequately contract due to the bond between the resin and the walls
stress
during polymerization, only the blank surfaces can act as stress relievers during the plastic deformation of the resin
free
fewer free surfaces results in blank
more stress
ratio of bonded to unbonded surfaces
C factor
c factor of class 3 MF in anterior teeth
4/2=2
c factor of class 3 MFL in anterior teeth
3/3=1
c factor of class 4
2/4=.5 (lower stress)
c factor of class 5 veneer
1/5=5=.2
higher stresses are caused by a higher blank
c factor
these classes have the highest stress
class 1, class 5
class 1 / class 5 c factor
5/1=5
these classes have the lowest stress
3,4
halogen lights tend to have blank power and these are like the ones we use in b28
lower
50-400 J
low intensity
Joules =
mW/cm^2
400-800 J
medium intensity
1000 J +
high intensity
two theories to reduce stress generation during polymerization
control amount of resin being polymerized, control the amount of energy given to the resin
a way to decrease stress is to apply blank before blank
flowable composite, resin composite
a way to decrease stress is to apply final layers in blank orientation
oblique
