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The effect of viscosity, specimen geometry and adhesion on the linear polymerization shrinkage measurement of light cured composites


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The effect of viscosity, specimen geometry and adhesion on the linear polymerization shrinkage measurement of light cured composites

Article information

Restor Dent Endod. 2003;28(6):457-466
Publication date (electronic) : 2003 November 30
doi : https://doi.org/10.5395/JKACD.2003.28.6.457
In-Bog Lee, Ho-Hyun Son, Hyuk-Chun Kwon, Chung-Moon Um, Byeong-Hoon Cho
Department of Conservative Dentistry, College of Dentistry, Seoul National University, Korea.
Corresponding author (chobh@plaza.snu.ac.kr)

Abstract

Objectives

The aim of study was to investigate the effect of flow, specimen geometry and adhesion on the measurement of linear polymerization shrinkage of light cured composite resins using linear shrinkage measuring device.

Methods

Four commercially available composites - an anterior posterior hybrid composite Z100, a posterior packable composite P60 and two flowable composites, Filtek flow and Tetric flow - were studied. The linear polymerization shrinkage of composites was determined using 'bonded disc method' and 'non-bonded' free shrinkage method at varying C-factor in the range of 1~8 by changing specimen geometry. These measured linear shrinkage values were compared with free volumetric shrinkage values.

The viscosity and flow of composites were determined and compared by measuring the dropping speed of metal rod under constant load.

Results

In non-bonded method, the linear shrinkage approximated one third of true volumetric shrinkage by isotropic contraction. However, in bonded disc method, as the bonded surface increased the linear shrinkage increased up to volumetric shrinkage value by anisotropic contraction. The linear shrinkage value increased with increasing C-factor and approximated true volumetric shrinkage and reached plateau at about C-factor 5~6. The more flow the composite was, reduced linear shrinkage was measured by compensation radial flow.

Keywords: Anisotropy; Polymerization shrinkage; Bonded disc method; Flow; C-factor; Light cured composites

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Article information Continued

Copyright © 2003 Korean Academy of Conservative Dentistry
(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.

Fig. 1-a

Fig. 1-a

The structure of instrument to measure linear shrinkage.

Fig. 1-b

Fig. 1-b

The geometry of composite specimen sandwiched between two glass plates. Polymerization shrinkage creates axial (vertical) and radial (horizontal) contraction of the specimen.

Fig. 2

Fig. 2

Linear polymerization shrinkage curves of composites as a function of time at C-factor ≈ 6.

Fig. 3

Fig. 3

Linear polymerization shrinkage of composites measured using bonded disc method. The linear shrinkage value increased with increasing C-factor and approximated volumetric shrinkage and reached plateau at about C-factor 5~6.

a) Linear shrinkage of Z1 as a function of C-factor.

b) Linear shrinkage of P6 as a function of C-factor.

c) Liner shrinkage of FF as a function of C-factor.

d) Linear shrinkage of TF as a function of C-factor.

Fig. 4

Fig. 4

Linear polymerization shrinkage of composites measured using non-bonded disc method with Vaseline. The linear shrinkage is not affected by specimen diameter and is approximated the theoretical linear shrinkage value calculated from true volumetric shrinkage value.

a) Linear shrinkage of Z1 as a function of specimen geometry.

b) Linear shrinkage of P6 as a function of specimen geometry.

c) Liner shrinkage of FF as a function of specimen geometry.

d) Linear shrinkage of TF as a function of specimen geometry.

Fig. 5

Fig. 5

Peak time (peak shrinkage rate time) of Z1 as a function of C-factor.

Fig. 6

Fig. 6

Relative viscosity of composites based on flow normalized to Z1.

Table 1

Materials used in this study

Table 1

Table 2

Volumetric polymerization shrinkage and linear shrinkage of composite resins at varying C-factor

Table 2

S.D. in parenthesis

N=5 in volumetric shrinkage measurement, however the number of samples varied in linear shrinkage measurement.

Table 3

Cure speed based on Peak Time (P.T.) of composites at varying C-factor

Table 3

Table 4

Consistency (viscosity) based on the flow of composite resins

Table 4

Relative flow is the flow value normalized to that of Z1 S.D. in parenthesis.

N=5