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

Article information

Restor Dent Endod. 2005;30(2):128-137

Publication date (electronic) : 2005 March 31

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

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 2004 September 06; Revised 2004 November 18; Accepted 2004 November 23.

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

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