Effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resin.
10.5395/JKACD.2008.33.4.341
- Author:
Min Kyung KIM
1
;
Sung Ho PARK
;
Deog Gyu SEO
;
Yun Jung SONG
;
Yoon LEE
;
Chan Young LEE
Author Information
1. Department of Conservative Dentistry, College of Dentistry, Yonsei University, Korea. chanyoungl@yuhs.ac
- Publication Type:Original Article
- Keywords:
Intermittent polymerization;
Rate of polymerization shrinkage;
Cuspal deflection;
Composite resin
- MeSH:
Acrylic Resins;
Bicuspid;
Composite Resins;
Light;
Polymerization;
Polymers;
Polyurethanes;
Tooth
- From:Journal of Korean Academy of Conservative Dentistry
2008;33(4):341-351
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
This study investigated the effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resins. The linear polymerization shrinkage of each composite was measured using the custom-made linometer along with the light shutter specially devised to block the light at the previously determined interval. Samples were divided into 4 groups by light curing method; Group 1) continuous light (60s with light on); Group 2) intermittent light (cycles of 3s with 2s light on & 1s with light off for 90s); Group 3) intermittent light (cycles of 2s with 1s light on & 1s with light off for 120s); Group 4) intermittent light (cycles of 3s with 1s light on & 2s with light off for 180s). The amount of linear polymerization shrinkage was measured and its maximum rate (Rmax) and peak time (PT) in the first 15 seconds were calculated. For the measurement of cuspal deflection of teeth, MOD cavities were prepared in 10 extracted maxillary premolars. Reduction in the intercuspal distance was measured by the custom-made cuspal deflection measuring machine. ANOVA analysis was used for the comparison of the light curing groups and t-test was used to determine significant difference between the composite resins. Pyramid showed the greater amount of polymerization shrinkage than Heliomolar (p < 0.05). There was no significant difference in the linear polymerization shrinkage among the groups. The Rmax was group 4 < 3, 2 < 1 in Heliomolar and group 3 < 4 < 2, 1 in Pyramid (p < 0.05). Pyramid demonstrated greater cuspal deflection than Heliomolar. The cuspal deflection in Heliomolar was group 4 < 3 < 2, 1 and group 4, 3 < 2, 1 in Pyramid (p < 0.05). It was concluded that the reduced rate of polymerization shrinkage by intermittent polymerization can help to decrease the cuspal deflection.
