Direct tooth colored restorations Flashcards
Direct
inserted as soft, ex composite, GI
Indirect
outside of mouth - cemented and bonded later. Veneers, onlays, etc.
Composites
polymer base, static, mechanically like amalgam, wear resistance a concern in the past, micromechanical retention - resin tags and a hybrid layer.
GI
water based, dynamic fluoride reservoir, decrease mechanical properties, wear resistance is good, chemically bonds (ionic bond not strong), recharge with fluoride varnish.
Posterior Composites - Advantages
Esthetic
• Conservative to tooth structure
• Easier preparation
Posterior Composites - Disadvantages
Technique sensitive
• Effects of polymerization shrinkage
Posterior Composites - Indications
In small/moderate-sized Class I & II preparations
• Areas where esthetics is of prime importance
Posterior Composites - Coutnerindatations
Complete moisture control is inadequate
• Heavy occlusal stresses
• The larger the preparation and the more posterior location
If a lot of attrition, bruxism, grinding
no composite
Resin matrix
soft phase, bis-GMA, TEGMA
BIS-GMA
main monomer, viscous oligomers
TEGMA
small linear molecule ~30% of composite oligomers
Filler
reinforcing phase
Max degree of conversion for composite
65-70%
Residual monomers =
30-35%, will plasticize, leak BPA
Filler
irregular or spherical particles
Degree of conversion
of double bonds of a monomer converted to single carbon bond during polymerization. This shrinks polymer, causing stress.
If stresses exceed binding agent,
debonding will occur.
Minimizing Gaps: 1.
Incremental/Layering Technique: Reduces bulk volumetric shrinkage
Minimizing gaps 2.
Placing a low viscosity material such as flowable composite prior to composite “Elastic theory”
Concept filler
improve in mechanical behavior
More filler = less resin , less polymerization shrinkage, decrease coefficient of thermal expansion
Glass particles and spheroidal silica particles Shape: spherical, irregular, combination
Size: range
Large fillers
under sliding force or wear, soft matrix can be removed leaving large filler exposed. This dislodges easily, exposing underlying resin (discolors as well). A cycle.
Nanosized - don’t
overload, this increases surface area and thus viscosity is too high.
Nanosized
no plucking, less wear
high polish
Too little = slump and sticky
Too much = hard to handle.