Polymerization shrinkage of composite resins cured by variable light intensities

Mi-Young Lim; Kyung-Mo Cho; Chan-Ui Hong

doi:10.5395/JKACD.2007.32.1.028

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Lim, Cho, and Hong: Polymerization shrinkage of composite resins cured by variable light intensities

Original Article

Journal of Korean Academy of Conservative Dentistry

Journal of Korean Academy of Conservative Dentistry 2007; 32(1): 28-36.

Published online: 31 January 2007

DOI: https://doi.org/10.5395/JKACD.2007.32.1.028

Polymerization shrinkage of composite resins cured by variable light intensities

Mi-Young Lim¹, Kyung-Mo Cho², Chan-Ui Hong¹

¹Department of Conservative Dentistry, School of Dentistry Dankook University, Korea.

²Department of Conservative Dentistry, School of Dentistry Kangnung National University, Korea.

Corresponding Author: Chan-Ui Hong. Department of Conservative Dentistry, College of Dentistry, Dankook University, 7-1 Shinbu-dong, Cheonan, Korea. Tel: 82-41-550-1964, Fax: 82-41-550-1963, endohong@hanmail.net

Received 4 December 2006 Revised 15 December 2006 Accepted 28 December 2006

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The purpose of this study was to compare the effect of exponential curing method with conventional curing and soft start curing method on polymerization shrinkage of composite resins.

Three brands of composite resins (Synergy Duo Shade, Z250, Filtek Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trilight) were used. 40 seconds curing time was given. The shrinkage was measured using linometer for 90 seconds.

The effect of time on polymerization shrinkage was analysed by one-way ANOVA and the effect of curing modes and materials on polymerization shrinkage at the time of 90s were analysed by two-way ANOVA. The shrinkage ratios at the time of 20s to 90s were taken and analysed the same way. The results were as follows:

1. All the groups except Supreme shrank almost within 20s. Supreme cured by soft start and exponential curing had no further shrinkage after 30s (p < 0.05).

2. Statistical analysis revealed that polymerization shrinkage varied among materials (p = 0.000) and curing modes (p = 0.003). There was no significant interaction between material and curing mode.

3. The groups cured by exponential curing showed the statistically lower polymerization shrinkage at 90s than the groups cured by conventional curing and soft start curing (p < 0.05).

4. The initial shrinkage ratios of soft start and exponential curing were statistically lower than conventional curing (p < 0.05).

From this study, the use of low initial light intensities may reduce the polymerization rate and, as a result, reduce the stress of polymerization shrinkage.

Keywords: Polymerization shrinkage, Light intensities, Soft start, Exponential curing, Linometer, Polymerization rate

Figures and Tables

Figure 1

Diagram of linometer.

Figure 2

Linear polymerization shrinkage of Synergy Duo Shade.

Figure 3

Linear polymerization shrinkage of Filtek Z250.

Figure 4

Linear polymerization shrinkage of Filtek Supreme.

Table 1

Linear polymerization shrinkage after 90 seconds with various curing modes (%)

Table 2

Two-factor analysis of variance for linear shrinkage at 90 seconds

Table 3

Homogeneous subsets of materials and curing modes at 90 seconds

Table 4

Linear polymerization shrinkage (%) at 20s and 90s and their ratio (%)(S.D)

Table 5

Two-factor analysis of variance for initial shrinkage ratios

Table 6

Homogeneous subsets of materials and curing modes of initial shrinkage ratios

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