J Korean Acad Conserv Dent JKACD Journal of Korean Academy of Conservative Dentistry 1225-0864 2093-8179 The Korean Academy of Conservative Dentistry 10.5395/JKACD.2006.31.1.058 Original Article The comparison of relative reliability on biaxial and three point flexural strength testing methods of light curing composite resin Seo Deog-Gyu Roh Byoung-Duck Department of Conservative Dentistry, College of Dentistry, Yonsei University, Korea. Corresponding Author: Byoung-Duck Roh. Department of Conservative Dentistry, College of Dentistry, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-752, Korea. Tel: 82-2-2228-3146, Fax: 82-2-313-7575, operatys16@yumc.yonsei.ac.kr 01 2006 31 01 2006 31 1 58 65 09 08 2005 30 10 2005 28 12 2005 Copyright © 2006 Korean Academy of Conservative Dentistry 2006

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.

The possibility of applying a bi-axial flexure strength test on composite resin was examined using three point and bi-axial flexure strength tests to measure the strength of the light-cured resin and to compare the relative reliability using the Weibull modulus.

The materials used in this study were light-curing restorative materials, MICRONEW™, RENEW® (Bisco, Schaumburg, USA). The bi-axial flexure strength measurements used the piston-on-3-ball test according to the regulations of the International Organization for Standardization (ISO) 6872 and were divided into 6 groups, where the radius of the specimens were 12 mm (radius connecting the 3-balls: 3.75 mm), 16 mm (radius connecting the 3-balls: 5 mm), and the thickness were 0.5 mm, 1 mm, 2 mm for each radius.

The bi-axial flexure strength of the MICRONEW™ and RENEW® were higher than the three point flexure strength and the Weibull modulus value were also higher in all of the bi-axial flexure strength groups, indicating that the bi-axial strength test is relatively less affected by experimental error.

In addition, the 2 mm thick specimens had the highest Weibull modulus values in the bi-axial flexure strength test, and the MICRONEW™ group showed no significant statistical difference (p > 0.05). Besides the 2 mm MICRONEW™ group, each group showed significant statistical differences (p < 0.05) according to the thickness of the specimen and the radius connecting the 3-balls.

The results indicate that for the 2 mm group, the bi-axial flexure strength test is a more reliable testing method than the three point flexure strength test.

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Schematic illustration of three point flexure test.

Schematic illustration of piston-on-three-ball bi-axial flexure test.

Weibull modulus graph according to specimen thickness on 3.75 mm supporting ball radius (MICRONEW™, Bisco, Schaumburg, U.S.A.).

Weibull modulus graph according to specimen thickness on 5 mm supporting ball radius (MICRONEW™, Bisco, Schaumburg, U.S.A.).

Weibull modulus graph according to specimen thickness on 3.75 mm supporting ball radius (RENEW®, Bisco, Schaumburg, U.S.A.).

Weibull modulus graph according to specimen thickness on 5 mm supporting ball radius (RENEW®, Bisco, Schaumburg, U.S.A.).

Light cured composite resin used in this study

Mean flexure strength and Weibull modulus of three point flexure test and biaxial flexure test

If the alphabet is different, significant difference at α= 0.05 (between the thickness on the same diameter).

*indicates significant difference at α= 0.05 (between the diameter on the same thickness).

Mean flexure strength and Weibull modulus of three point flexure test and biaxial flexure test

If the alphabet is different, significant difference at α= 0.05 (between the thickness on the same diameter).

*indicates significant difference at α= 0.05 (between the diameter on the same thickness).