Surface hardness of the dental composite cured by light that penetrate tooth structure according to thickness of tooth structure, light intensity and curing time

Soo-Kyung Cho; Dong-Jun Kim; Yun-Chan Hwang; Won-Mann Oh; In-Nam Hwang

doi:10.5395/JKACD.2005.30.2.128

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Cho, Kim, Hwang, Oh, and Hwang: Surface hardness of the dental composite cured by light that penetrate tooth structure according to thickness of tooth structure, light intensity and curing time

Original Article

Journal of Korean Academy of Conservative Dentistry

Journal of Korean Academy of Conservative Dentistry 2005; 30(2): 128-137.

Published online: 31 March 2005

DOI: https://doi.org/10.5395/JKACD.2005.30.2.128

Surface hardness of the dental composite cured by light that penetrate tooth structure according to thickness of tooth structure, light intensity and curing time

Soo-Kyung Cho, Dong-Jun Kim, Yun-Chan Hwang, Won-Mann Oh, In-Nam Hwang

Department of Conservative Dentistry, College of Dentistry, DSRI, Chonnam National University, Korea.

Corresponding author: In-Nam Hwang. Department of Conservative Dentistry, College of Dentistry, Chonnam National University, 8 Hak-dong, Dong-gu, Gwangju, Korea, 501-757. Tel: 82-62-220-4443, Fax: 82-62-225-8387, hinso@jnu.ac.kr

Received 6 September 2004 Revised 18 November 2004 Accepted 23 November 2004

(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

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 mW/cm² light intensity and a 7 mm diameter turbo light guide with 1100 mW/cm².

Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers'hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05).

The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.

Keywords: Polymerization rate, Vickers' hardness, Thickness of tooth structure

Figures and Tables

Figure 1

Schematic drawing of specimen fabrication.

Figure 2

Vickers' hardness number of all specimens.

Figure 3

Vickers' hardness of resin composites cured by Turbo-light guide.

Figure 4

Vickers' hardness of resin composites cured by 12 mm diameter light guide.

Figure 5

Ratio of Vickers' hardness by thickness of tooth structure.

Table 1

Groups were divided according to the thickness of tooth specimen, used light guide, curing time.

Table 2

Vickers' hardness of the tested resin composites

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