BisEMA (BE) systems have lower viscosities and can be used for processing composites with less diluent (T=Tegdma)) than traditional BisGMA (BG) resin. Low diluent-containing formulations can result in lower polymerization shrinkage without greatly reducing degrees of polymer conversion. Objective: The purpose of this investigation was to determine the clinical relevance of combining low shrinkage composites with pulse activation light curing. Methods: Three formulations were used to fabricate highly filled composites (70% SrSiO2,, 10% OX50). A high diluent-containing BisGMA resin (BG5T5) was compared to high (BE5T5) and low (BE9T1) diluent-containing BisEMA composites. The linear polymerization shrinkage, shrinkage stress, and degree of double-bond conversion (DC) were determined for the composite materials after a 40 sec. light exposure (Control) and after pulse-delay activation (PD). To determine the clinical significance, a simulated class I leakage test was devised using 6mm ID glass-rings and standard bonding techniques. Wall detachment could be easily measured and the percentage of remaining attachment determined for each material and curing technique. The means (sd) of measured values are reported. Results: Two-way ANOVAs suggest that both the material and the
|
ID |
Stress (microstrain) |
Linear % |
DC (%) |
% attachment |
||||
|
Control |
PD |
Control |
PD |
Control |
Pd |
Control |
PD |
|
|
BG5T5 |
1462 (113) |
962 (271) |
2.7 (0.1) |
2.6 (0.2) |
50 (1) |
51 (1) |
25(2) |
39(8) |
|
BE5T5 |
2168 (244) |
1466 (151) |
3.2 (0.5) |
2.7 (0.2) |
55(0.4) |
53 (1) |
25(2) |
31(6) |
|
BE9T1 |
1495 (125) |
880 (28) |
2.1 (0.1) |
2.0 (0.1) |
54(0.2) |
53 (1) |
40(5) |
58(2) |
curing method significantly affect each of the measured properties. Conclusion: While shrinkage and shrinkage stress can be significantly reduced through the use of pulse-delay activation and low shrinkage composite, the leakage test suggests that the perfect seal may not be achieved. Materials and techniques can be implemented to reduce but not eliminate leakage. Supported by NIH #T32 DE14320.