Mechanical properties and microleakage of composite resin materials cured by variable light intensities

Seung-Ryul Han; Kyung-San Min; Dong-Hoon Shin

doi:10.5395/JKACD.2003.28.2.134

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Han, Min, and Shin: Mechanical properties and microleakage of composite resin materials cured by variable light intensities

Original Article

Journal of Korean Academy of Conservative Dentistry

Journal of Korean Academy of Conservative Dentistry 2003; 28(2): 134-145.

Published online: 31 March 2003

DOI: https://doi.org/10.5395/JKACD.2003.28.2.134

Mechanical properties and microleakage of composite resin materials cured by variable light intensities

Seung-Ryul Han, Kyung-San Min, Dong-Hoon Shin

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

Corresponding author (donyshin@dankook.ac.kr)

(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

Mechanical properties and microleakage of two composites [conventional hybrid type DenFil (VERICOM Co., Anyang, Korea) / micro matrix hybrid type Esthet X (Dentsply Caulk, Milford, DE, U.S.A.)] were evaluated to assess whether variable light intensity curing is better than conventional curing technique.

Curing was done for 40 seconds in two ways of 2 step soft-start technique and 5 step ramping technique. Three kinds of light intensities of 50, 100, 200 mW/cm² were initially used for 10, 20, 30 seconds each and the maximum intensity of 600 mW/cm² was used for the rest of curing time in a soft-start curing technique. In a ramping technique, curing was done with the same initial intensities and the light intensity was increased 5 times with the same rate to the maximum intensity of 600 mW/cm².

After determining conditions that showed no different mechanical properties with conventional technique, Esthet X composite was filled in a class V cavity, which dimension was 4×3×1.5 mm and cured under those conditions.

Microleakage was evaluated in two ways of dye penetration and maximum gap estimation through SEM observation. ANOVA and Spearman's rho test were used to confirm any statistical significance among groups.

The results were as follows:

Several curing conditions of variable light intensities resulted in the similar mechanical properties with a conventional continuous curing technique, except conditions that start curing with an initial light intensity of 50 mW/cm²,
Conventional and ramping techniques were better than soft-start technique in mechanical properties of microhardness and compressive strength.
Soft-start group that started curing with an initial light intensity of 100 mW/cm² for 10 seconds showed the least dye penetration. Soft-start group that started curing with an initial light intensity of 200 mW/cm² for 10 seconds showed the smallest marginal gap, if there was no difference among groups.
Soft-start technique resulted in better dye-proof margin than conventional technique (p=0.014) and ramping technique(p=0.002).
There was a very low relationship(p=0.157) between the methods of dye penetration and marginal gap determination through SEM evaluation.

From the results of this study, it was revealed that ramping technique would be better than conventional technique in mechanical properties, however, soft-start technique might be better than conventional one in microleakage.

It was concluded that much endeavor should be made to find out the curing conditions, which have advantages of both aspects or to solve these kinds of problems through a novel idea of polymerization.

Keywords: Conventional curing technique, Soft-start technique, Ramping technique, Microhardness, Compressive strength, Microleakage

Figures and Tables

Fig. 1

Diagram of the length measurement of diamond-shape indent

Table 1

Experimental materials

Table 2

Classification of experimental groups according to curing conditions

600(40)^*:Control group

Table 3

Vickers hardness [Mean (S.D.)] (unit: kg/mm²)

Table 4

Mean hardness value and statistics of the upper surface according to ways of variable light intensity (DenFil)

^**:p < 0.01

Table 5

Mean hardness value and statistics of the lower surface according to ways of variable light intensity (DenFil)

^**:p < 0.01

Table 6

Mean hardness value and statistics of the upper surface according to ways of variable light intensity (Esthet X)

^**:p < 0.01

Table 7

Mean hardness value and statistics of the lower surface according to ways of variable light intensity (Esthet X)

^**:p < 0.01

Table 8

Maximum compressive strength (kg/mm²)

Table 9

Mean maximum compressive strength and statistics of DenFil according to ways of variable light intensity (unit: kgf/mm²)

^**:p < 0.01

Table 10

Mean maximum compressive strength and statistics of Esthet X according to ways of variable light intensity (unit: kgf/mm²)

^*:p < 0.05

Table 11

Mean degree of dye penetration

Table 12

Mean ranks of degree of dye penetration (Kruskal-Wallis test)

^*:p < 0.05

Table 13

Mean degree of dye penetration and ranks at gingival margin according to ways of variable light intensity

^*:p < 0.05 ^**:p < 0.01

Table 14

Maximum gap (unit: µm)

Table 15

Mean maximum gap at gingival margin according to ways of variable light intensity (unit: µm)

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