The polymerization rate and the degree of conversion of composite resins by different light sources

Joo-Hee Ryoo; In-Bog Lee; Hyun-Mee Yoo; Mi-Ja Kim; Chang-In Seok; Hyuk-Choon Kwon

doi:10.5395/JKACD.2004.29.4.386

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Ryoo, Lee, Yoo, Kim, Seok, and Kwon: The polymerization rate and the degree of conversion of composite resins by different light sources

Original Article

Journal of Korean Academy of Conservative Dentistry

Journal of Korean Academy of Conservative Dentistry 2004; 29(4): 386-398.

Published online: 31 July 2004

DOI: https://doi.org/10.5395/JKACD.2004.29.4.386

The polymerization rate and the degree of conversion of composite resins by different light sources

Joo-Hee Ryoo¹, In-Bog Lee¹, Hyun-Mee Yoo², Mi-Ja Kim¹, Chang-In Seok¹, Hyuk-Choon Kwon¹

¹Department of Conservative Dentistry, College of Dentistry, Seoul National University, Korea.

²Department of Conservative Dentistry, The Institute of Oral Health Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.

Corresponding author: Hyuk-Choon Kwon. Department of Conservative Dentistry, College of Dentistry, Seoul National University, 28-2 Yeongun-dong, Chongro-gu, Seoul, Korea 110-749. Tel: 82-2-422-6644, Fax: 82-2-424-0135, dentphd@hanmail.net

(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

Objectives

The purpose of this study was to observe the reaction kinetics and the degree of polymerization of composite resins when cured by different light sources and to evaluate the effectiveness of the blue Light Emitting Diode Light Curing Units (LED LCUs) compared with conventional halogen LCUs.

Materials and Methods

First, thermal analysis was performed by a differential scanning calorimeter (DSC). The LED LCU (Elipar Freelight, 320 mW/cm²) and the conventional halogen LCU (XL3000, 400 mW/cm²) were used in this study for curing three composite resins (SureFil, Z-250 and AEliteFLO). Second, the degree of conversion was obtained in the composite resins cured according to the above curing mode with a FTIR. Third, the measurements of depth of cure were carried out in accordance with ISO 4049 standards. Statistical analysis was performed by two-way ANOVA test at 95% levels of confidence and Duncan's procedure for multiple comparisons.

Results

The heat of cure was not statistically different among the LCUs (p > 0.05). The composites cured by the LED (Exp) LCUs were statistically more slowly polymerized than by the halogen LCU and the LED (Std) LCU (p < 0.05). The composite resin groups cured by the LED (Exp) LCUs had significantly greater degree of conversion value than by the halogen LCU and the LED (Std) LCU (p = 0.0002). The composite resin groups cured by the LED (Std) LCUs showed significantly greater depth of cure value than by the halogen LCU and the LED (Exp) LCU (p < 0.05).

Keywords: LED light curing units, DSC, Heat of cure, Maximum rate of heat output, Peak heat flow time, Degree of conversion, Depth of cure

Figures and Tables

Figure 1

DSC cell section and acrylic stand to fix light guide.

Figure 2

Stainless steel mold cross-section.

Figure 3

Heat of cure (-△H : J/g) of each resin with different light sources.

Figure 4

Maximum rate of heat output (watt/g).

Figure 5

Mean time to reach peak heat output (sec).

Figure 6

Degree of conversion (%) of each resin with different light sources.

Figure 7

Depth of cure (mm) of each resin with different light sources.

Graph 1

DSC thermogram of Z-250 when cured with Elipar Freelight (Std)-LED

Graph 2

FTIR spectrum of SureFil when cured with Elipar Freelight (Std)-LED

Table 1

Curing lights used in this study

Table 2

Composite resins used in this study

Table 3

Heat of cure (-△H : J/g) of each resin with different light sources

Different letters(a,b,c) indicate statistically significant differences on the horizontal line (p < 0.05).

Table 4

Maximum rate of heat output (watt/g)

^*Indicates statistically significant differences on the vertical line (p < 0.05).

Different letters (a,b,c) indicate statistically significant differences on the horizontal line (p < 0.05).

Table 5

Mean time to reach peak heat output(sec)

^*Indicates statistically significant differences on the vertical line (p < 0.05).

^†Indicates statistically significant differences on the horizontal line (p < 0.05).

Table 6

Degree of conversion (%) of each resin with different light sources

^*Indicates statistically significant differences on the vertical line (p < 0.05).

Different letters (a,b,c) indicate statistically significant differences on the horizontal line (p < 0.05).

Table 7

Depth of cure (mm) of each resin with different light sources

^*Indicates statistically significant differences on the vertical line (p < 0.05).

^†Indicates statistically significant differences on the horizontal line (p < 0.05).

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