GC EUROPE Kalore - Manual (Page 10)

10
70
70
50
50
27
30
45
50
90
100
0.0 20.0 40.0 60.0 80.0 100.0 120.0
Before Polymerization
After Polymerization
Before Polymerization
After Polymerization
Before Polymerization
After Polymerization Filler
Resin
teG
Dma
mw=
286.3
Bis-
Gma
mw=
512.6
uDma
mw=
470.6
GC Kalore technical manual
Figure 4. Influence of filler loading on shrinkage. Figure 5. Polymerization shrinkage of low vs. high molecular
weight monomers.
5.3 Reducing Polymerization Shrinkage
Polymerization shrinkage is influenced by clinical technique and manufacturing of the composite resin.
there are several ways to reduce shrinkage from a manufacturing perspective, as described below.
Increase Filler Loading
Increasing filler loading in the resin matrix
reduces polymerization shrinkage by
decreasing the proportion of monomer
content, thereby reducing shrinkage (Fig. 4).
Adjust the Monomers
monomers with a low molecular weight shrink
more during polymerization than those with higher molecular weights. methacrylate monomers are
typically used in dental composite resins, mainly Bis-GMA and UDMA, due to their favorable
physical properties. teGDma is usually added to adjust the viscosity and to make the composite
material easier to handle. TEGDMA has a lower molecular weight than Bis-GMA and UDMA (Table
2). Using less TEGDMA decreases polymerization shrinkage (Fig. 5).
table 2. molecular weight of monomers typically used in dental composites.
Use of Pre-polymerized Fillers
Pre-polymerized fillers are relatively large fillers with less surface area, enabling greater volumetric
filler loading and thereby resulting in less volumetric shrinkage (Fig. 6b). these larger fillers also
prevent the resin matrix from moving as a result of friction between the resin and the pre-
polymerized filler surface during curing, thereby reducing shrinkage. this technology is used in
GRaDia DiRect.
Figure 6b. Polymerization shrinkage of composites containing
pre-polymerized fillers. close contact between the
pre-polymerized fillers prevents resin shrinkage.
Figure 6a. Shrinkage of microhybrid composites.
the distance between the glass particles lessens
during shrinkage.
Polymerazation
Before Polymerization
After Polymerization
Before Polymerization
After Polymerization
Before Polymerization
After Polymerization
Filler
Resin