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Dent Mater J. 2019 Jun 7. doi: 10.4012/dmj.2018-279. [Epub ahead of print]

Effect of light-curing time on light-cure/post-cure volumetric polymerization shrinkage and regional ultimate tensile strength at different depths of bulk-fill resin composites.

Author information

1
Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU).
2
Department of Oral Prosthetic Engineering, Graduate School, Faculty of Dentistry, Tokyo Medical and Dental University (TMDU).
3
Department of Operative Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University.
4
Division of Conservative Dentistry, King's College London Dental Institute at Guy's, King's and St Thomas' Hospitals, King's College London.
5
National Center for Geriatrics oand Gerontology, Department of Advanced Dental Research, Center of Advanced Medicine for Dental and Oral Disease.
6
Global Center of Excellence Program; International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University.

Abstract

The aim of this study was to investigate volumetric polymerization shrinkage (VS), using swept-source optical coherence tomography (SS-OCT), of bulk-fill composites with different light-curing strategies; immediately after light-irradiation and after 24 h, and to evaluate their regional ultimate tensile strength (UTS) at different curing depths. The immediate VS after photo-polymerization decreased when the curing light-curing time was reduced from 20 to 10 to 5 s. On the other hand, their VS values after 24 h significantly increased due to the post-cure polymerization, resulting in similar VS values at all the light-curing times. Five seconds light-curing decreased the regional UTS of resin composites after the 24 h period compared with the 10 and 20 s light-curing regimes; therefore, the remarkable progress of post-cure polymerization after light-curing for a short time would not lead to an improvement in the mechanical properties of resin composites. The influence of the light-curing time on the curing depth was dependent upon the bulk-fill composite material.

KEYWORDS:

Bulk fill; Depth of cure; Optical coherence tomography; Ultimate tensile strength; Volumetric shrinkage

PMID:
31178547
DOI:
10.4012/dmj.2018-279
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