Journal of the Korean Academy of Pediatric Dentistry 2003;30(1):102-109.
Published online February 28, 2003.
A STUDY ON THE POLYMERIZATION SHRINKAGE OF COMPOSITE RESIN ACCORDING TO VARIOUS LIGHT-CURING METHODS
 
광조사 방법에 따른 복합레진의 중합수축에 관한 연구
권오진, 김종수, 권순원
단국대학교 치과대학 소아치과학교실
Abstract
The purpose of this study was to evaluate the linear polymerization shrinkage(%) and microhardness of composite resin(Z-100, 3M, USA) according to 2-step light curing method. Conventional light curing unit(Curing Light 2500, 3M USA) and 2-step light curing unit(Elipar Highlight, ESPE, Germany) were used as light source. The strain gauge method was used for determination of polymerization shrinkage(%). Samples were divided by 3 groups according to light curing methods (Group I : 450mW/cm2, 40sec, Group II : 650mW/cm2, 40sec, Group III : 150mW/cm2, 10sec & 650mW/cm2, 30sec). Preparations of acrylic molds were followed by filling and curing. Strain gauges attached to each sample were connected to a strainmeter. Measurements were recorded at each second for the total of 10 minutes including the periods of light application. And microhardness of each group after 24hours from light irradiation were measured. Obtained data were analyzed statistically using Ore-way ANOVA and/or Scheffe test. The results of the present study can be summarized as follows: 1. Composite resin in acrylic molds showed the initial expansion at the early phase of polymerization. This was followed by the contraction with the rapid increase in volume during the first 60 seconds and gradually diminished as curing process continued. 2. The lowest linear polymerization shrinkage(%) was found in group III followed by group I, II during the measuring periods. 3. Group III using 2-step curing method showed statistically significant reduction of linear polymerization shrinkage(%) compared with group I, II at 1 minute and 10 minutes from light irradiation(p<0.05). 4. The microhardness values of each group not revealed significant difference.
Key Words: 2-step curing, Polymerization shrinkage, Strain gauge method, Composite resin


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