Microhardness of resin composite materials light-cured through fiber reinforced composite

Fennis, Willem M.M.; Ray, Noel J.; Creugers, Nico H.J.; Kreulen, Cees M.

doi:10.1016/j.dental.2009.01.102

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Volume 25, Issue 8 , Pages 947-951, August 2009

Microhardness of resin composite materials light-cured through fiber reinforced composite

Willem M.M. Fennis
- Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- Corresponding author at: Department of Oral Function and Prosthetic Dentistry, College of Dental Science, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Tel.: +31 24 361 4004; fax: +31 24 354 1971.
Noel J. Ray
- Materials Science Group, University Dental School and Hospital, University College Cork, Cork, Ireland
Nico H.J. Creugers
- Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
Cees M. Kreulen
- Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands

Received 22 July 2008; accepted 30 January 2009.

Abstract

Objectives

To compare polymerization efficiency of resin composite basing materials when light-cured through resin composite and fiber reinforced composite (FRC) by testing microhardness.

Methods

Simulated indirect restorations were prepared by application of resin composite (Clearfil AP-X) or FRC (EverStick) to nylon rings with 1.5mm thickness and 8mm diameter, followed by light-curing. Resin composite basing material (Clearfil Majesty Flow or Clearfil AP-X) was applied to identical rings and light-cured through the simulated indirect restorations with exposure times of 20, 40, or 60s. Light-curing though a ring without resin material (=no indirect restoration) served as control. For each combination of basing material and indirect restoration 10 specimens were prepared for each exposure time. Top and bottom surface Vickers microhardness numbers (VHNs) of basing materials were recorded after 24h.

Results

After 60s exposure time, VHNs with indirect FRC were not different from control VHNs, while VHNs with indirect resin composite were significantly lower (p<0.001). Linear regression analysis revealed that resin composite basing material used had the greatest effect on top and bottom VHNs (p<0.001). The presence of an indirect restoration resulted in decreased VHNs (p<0.001), with resin composite resulting in lower VHNs when compared to FRC. Moreover, a longer exposure time resulted in increased VHNs (p<0.001).

Significance

Results suggest that polymerization of resin composite basing materials is more effective when light-curing through an FRC than through a resin composite indirect restoration. Prolonging of exposure time, however, is necessary when compared to light-curing without presence of indirect restoration material.

Keywords: Dental material, Microhardness, Polymerization, Fiber reinforced composite, Indirect restoration, Resin composite, Composite basing, Exposure time